docs: add missing XML doc comments across gateway, worker, and .NET client

Resolves 1113 documentation-completeness gaps flagged by CommentChecker
(MissingReturns, MissingInheritDoc, InheritDocMisused, MissingDoc,
MissingParam, RedundantInheritDoc) so the API surface is fully documented
and the analyzer scan is clean. Doc comments only; no code changes.

.gitignore

@@ -45,6 +45,7 @@ build/
 out/
 tmp/
 temp/
+install/
 
 # .NET
 **/bin/
@@ -146,3 +147,8 @@ generated-scratch/
 
 # Keep empty directories with .gitkeep files when needed
 !.gitkeep
+
+# Documentation review artifacts (CommentChecker output)
+*-docs-issues.md
+*-docs-fixed.md
+*-docs-final.md

CLAUDE.md

@@ -100,7 +100,7 @@ When source code changes, build and test the affected component before reporting
 ## Design Sources To Consult Before Non-Trivial Changes
 
 - `gateway.md` — top-level architecture, command/event surface, IPC envelope, STA thread model, fault handling.
-- `glauth.md` — local LDAP server (GLAuth on `localhost:3893`, base DN `dc=lmxopcua,dc=local`) used for dev authn. Pre-provisioned users (`admin/admin123`, `readonly/readonly123`, etc.) and the role→capability mapping live there.
+- `glauth.md` — local LDAP server (GLAuth on `localhost:3893`, base DN `dc=zb,dc=local`) used for dev authn. Pre-provisioned users (`admin/admin123`, `readonly/readonly123`, etc.) and the role→capability mapping live there.
 - `docs/DesignDecisions.md` — v1 choices (MXAccess COM target `LMXProxyServerClass` from `C:\Program Files (x86)\ArchestrA\Framework\Bin\ArchestrA.MXAccess.dll`, API-key-in-SQLite auth, fail-fast event backpressure, etc.).
 - `docs/GatewayProcessDesign.md`, `docs/MxAccessWorkerInstanceDesign.md`, `docs/WorkerFrameProtocol.md`, `docs/WorkerProcessLauncher.md` — detailed component designs.
 - `docs/GatewayConfiguration.md` — full `MxGateway:*` options bound by `GatewayOptions` and validated at startup by `GatewayOptionsValidator`.

REVIEW-PROCESS.md

@@ -0,0 +1,140 @@
+# Code Review Process
+
+This document describes how to perform a comprehensive, per-module code review of
+the `mxaccessgw` codebase and how to track findings to resolution.
+
+A **module** is one buildable project under `src/` (e.g. `src/ZB.MOM.WW.MxGateway.Worker`)
+or one language client under `clients/` (e.g. `clients/rust`). Each module has
+its own folder under `code-reviews/` containing a single `findings.md`.
+
+## 1. Before you start
+
+1. Pick the module to review. Its folder is `code-reviews/<Module>/`:
+   - For a `src/` project, `<Module>` is the project name with the `ZB.MOM.WW.MxGateway.`
+     prefix stripped — `src/ZB.MOM.WW.MxGateway.Server` is reviewed in `code-reviews/Server/`.
+   - For a language client, `<Module>` is `Client.<Lang>` — `clients/rust` is
+     reviewed in `code-reviews/Client.Rust/`.
+2. Identify the design context for the module:
+   - `gateway.md` — top-level architecture, command/event surface, IPC envelope,
+     STA thread model, fault handling.
+   - The relevant component design docs under `docs/` (e.g.
+     `docs/MxAccessWorkerInstanceDesign.md`, `docs/GatewayProcessDesign.md`,
+     `docs/Sessions.md`, `docs/Authentication.md`, `docs/GalaxyRepository.md`).
+   - `docs/DesignDecisions.md` for the v1 design choices.
+   - The **Repository-Specific Conventions** and **Process / Platform Notes** in
+     `CLAUDE.md`.
+3. Record the exact commit being reviewed: `git rev-parse --short HEAD`. Every
+   review is a snapshot — a finding only means something relative to a known
+   commit.
+4. Open `code-reviews/<Module>/findings.md` and fill in the header table
+   (reviewer, date, commit SHA, status).
+
+## 2. Review checklist
+
+Work through **every** category below for the module. A comprehensive review
+means the checklist is completed even where it produces no findings — record
+"No issues found" for a category rather than leaving it ambiguous.
+
+1. **Correctness & logic bugs** — off-by-one, null handling, incorrect
+   conditionals, misuse of APIs, broken edge cases.
+2. **mxaccessgw conventions** — the rules in `CLAUDE.md` and the style guides
+   under `docs/style-guides/`: the gateway never instantiates MXAccess COM
+   directly; all MXAccess COM calls run on the worker's dedicated STA thread and
+   the STA loop pumps Windows messages; IPC uses one bidirectional named pipe per
+   worker carrying length-prefixed `WorkerEnvelope` protobuf frames; MXAccess
+   parity is the contract (don't "fix" surprising MXAccess behaviour, never
+   synthesize events); one worker and one event subscriber per session; the
+   gateway terminates orphan workers on startup and does not reattach; C# style
+   (file-scoped namespaces, `sealed` by default, `Async` suffix, MXAccess-aligned
+   names); no Blazor UI component libraries; no logging of secrets or full tag
+   values; generated code is never hand-edited.
+3. **Concurrency & thread safety** — shared mutable state, STA affinity, race
+   conditions, correct use of `async`/`await`, locking, disposal races.
+4. **Error handling & resilience** — exception paths, worker crash / reconnect
+   handling, fail-fast event backpressure, transient vs permanent error
+   classification, graceful degradation, correct gRPC status codes.
+5. **Security** — authentication/authorization checks, API-key scope enforcement,
+   input validation, SQL injection in the Galaxy Repository RPCs, secret
+   handling, the dashboard anonymous-localhost bypass, logging of sensitive data.
+6. **Performance & resource management** — `IDisposable` disposal, pipe / stream
+   / COM lifetimes, buffering and back-pressure, unnecessary allocations on hot
+   paths, N+1 queries.
+7. **Design-document adherence** — does the code match `gateway.md`, the relevant
+   `docs/` component designs, `docs/DesignDecisions.md`, and `CLAUDE.md`? Flag
+   both code that drifts from the design and design docs that are now stale.
+8. **Code organization & conventions** — namespace hierarchy, project layout, the
+   Options pattern, separation of concerns, additive-only contract evolution.
+9. **Testing coverage** — are the module's behaviours covered by tests
+   (`src/ZB.MOM.WW.MxGateway.Tests`, `src/ZB.MOM.WW.MxGateway.Worker.Tests`,
+   `src/ZB.MOM.WW.MxGateway.IntegrationTests`)? Note untested critical paths and missing
+   edge-case tests.
+10. **Documentation & comments** — XML doc accuracy, misleading or stale comments,
+    undocumented non-obvious behaviour.
+
+## 3. Recording findings
+
+Add one entry per finding to the `## Findings` section of the module's
+`findings.md`, using the entry format in
+[`_template/findings.md`](code-reviews/_template/findings.md).
+
+- **Finding ID** — `<Module>-NNN`, numbered sequentially within the module and
+  never reused (e.g. `Worker-001`). IDs are permanent even after resolution.
+- **Severity:**
+  - **Critical** — data loss, security breach, crash/deadlock, or outage.
+  - **High** — incorrect behaviour with significant impact; no safe workaround.
+  - **Medium** — incorrect or risky behaviour with limited impact or a workaround.
+  - **Low** — minor issues, style, maintainability, documentation.
+- **Category** — one of the 10 checklist categories above.
+- **Location** — `file:line` (clickable), or a list of locations.
+- **Description** — what is wrong and why it matters.
+- **Recommendation** — concrete suggested fix.
+
+After recording findings, update the module header table (status, open-finding
+count) and regenerate the base README (step 5).
+
+## 4. Marking an item resolved
+
+Findings are **never deleted** — they are an audit trail. To close one, change
+its **Status** and complete the **Resolution** field:
+
+- `Open` — newly recorded, not yet addressed.
+- `In Progress` — a fix is actively being worked on.
+- `Resolved` — fixed. The Resolution field must state the fixing commit SHA, the
+  date, and a one-line description of the fix.
+- `Won't Fix` — intentionally not fixed. The Resolution field must justify why.
+- `Deferred` — valid but postponed. The Resolution field must say what it is
+  waiting on (e.g. a tracked issue or a later milestone).
+
+`Resolved`, `Won't Fix`, and `Deferred` findings are all considered **closed**.
+`Open` and `In Progress` are **pending** and appear in the base README's Pending
+Findings table.
+
+## 5. Updating the base README
+
+`code-reviews/README.md` holds the single cross-module view (the Module Status
+table and the Pending / Closed Findings tables). It is **generated** from the
+per-module `findings.md` files — do not edit it by hand.
+
+After any review or status change, regenerate it:
+
+```
+python code-reviews/regen-readme.py
+```
+
+`regen-readme.py --check` exits non-zero if `README.md` is stale, if a module
+header's `Open findings` count disagrees with its finding statuses, or if a
+finding carries an unrecognised Status value. The PowerShell wrapper
+`scripts/check-code-reviews-readme.ps1` runs that check and is the intended hook
+for CI or a pre-commit step.
+
+> The repo's installed `python` is the real interpreter; the bare `python3`
+> alias resolves to the Windows Store stub and fails. Use `python`.
+
+The per-module `findings.md` files are the source of truth; `README.md` is the
+aggregated index and must always agree with them — which the script guarantees.
+
+## 6. Re-reviewing a module
+
+Re-reviews append to the same `findings.md`. Update the header to the new commit
+and date, continue the finding numbering from the last used ID, and leave prior
+findings (including closed ones) in place as history.

clients/dotnet/Directory.Build.props

@@ -0,0 +1,21 @@
+<Project>
+  <PropertyGroup>
+    <!-- Shared package metadata for clients/dotnet/. Individual projects opt in via <IsPackable>true</IsPackable>. -->
+    <Authors>Joseph Doherty</Authors>
+    <Company>ZB MOM WW</Company>
+    <Copyright>Copyright (c) ZB MOM WW. All rights reserved.</Copyright>
+    <Product>MxAccessGateway Client</Product>
+    <RepositoryUrl>https://gitea.dohertylan.com/dohertj2/mxaccessgw</RepositoryUrl>
+    <RepositoryType>git</RepositoryType>
+    <PackageProjectUrl>https://gitea.dohertylan.com/dohertj2/mxaccessgw</PackageProjectUrl>
+    <PackageTags>mxaccess;mxgateway;grpc;client;archestra</PackageTags>
+    <PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
+    <!-- Versioning: bump per release. Symbols ship as snupkg. -->
+    <Version>0.1.0</Version>
+    <IncludeSymbols>true</IncludeSymbols>
+    <SymbolPackageFormat>snupkg</SymbolPackageFormat>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <!-- Default: do NOT pack. Each project opts in. -->
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+</Project>

clients/dotnet/DotnetClientDesign.md

@@ -107,6 +107,7 @@ public sealed class MxGatewayClientOptions
     public required string ApiKey { get; init; }
     public bool UseTls { get; init; }
     public string? CaCertificatePath { get; init; }
+    public bool RequireCertificateValidation { get; init; }
     public string? ServerNameOverride { get; init; }
     public TimeSpan ConnectTimeout { get; init; } = TimeSpan.FromSeconds(10);
     public TimeSpan DefaultCallTimeout { get; init; } = TimeSpan.FromSeconds(30);
@@ -124,6 +125,24 @@ or subscription changes because those calls can partially succeed in MXAccess.
 API key may be loaded from `MXGATEWAY_API_KEY` by the CLI, not implicitly by the
 library constructor unless a helper explicitly says it does that.
 
+### TLS trust posture
+
+The gateway can serve a self-signed certificate it generates itself (it has no
+PKI). To make that usable, TLS is **lenient by default**: when `UseTls` is set
+and `CaCertificatePath` is empty, `CreateHttpHandler` installs a
+`RemoteCertificateValidationCallback` that returns `true`, so the gateway's
+self-signed certificate is accepted without verification.
+
+To verify the gateway instead:
+
+- set `CaCertificatePath` to pin a CA — validated via a `CustomRootTrust`
+  `X509Chain` against that root, and the callback additionally rejects a
+  hostname/SAN mismatch (`RemoteCertificateNameMismatch`); or
+- set `RequireCertificateValidation` to `true` to keep the default OS/system-trust
+  verification on a connection with no pinned CA.
+
+Pinning a CA always wins over the lenient default.
+
 ## Auth Interceptor
 
 Use a gRPC call credentials/interceptor layer to attach:

clients/dotnet/README.md

@@ -134,8 +134,8 @@ dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- advise --s
 dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- write --session-id <id> --server-handle 1 --item-handle 1 --type int32 --value 123 --json
 dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- write2 --session-id <id> --server-handle 1 --item-handle 1 --type int32 --value 123 --timestamp 2026-01-01T00:00:00Z --json
 dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- stream-events --session-id <id> --max-events 1 --json
-dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- stream-alarms --session-id <id> --max-messages 1 --json
-dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- acknowledge-alarm --session-id <id> --alarm-reference "\\Galaxy\Area001.Pump001.PumpFault" --json
+dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- stream-alarms --filter-prefix Area001 --max-events 1 --json
+dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- acknowledge-alarm --reference "\\Galaxy\Area001.Pump001.PumpFault" --comment "ack from cli" --operator operator1 --json
 dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- smoke --endpoint http://localhost:5000 --api-key-env MXGATEWAY_API_KEY --item Area001.Pump001.Speed --json
 ```
 
@@ -196,6 +196,54 @@ dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- galaxy-las
 dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- galaxy-discover --endpoint http://localhost:5000 --api-key-env MXGATEWAY_API_KEY
 ```
 
+### Browsing lazily
+
+For UI trees or OPC UA bridges, use `BrowseChildrenAsync` to walk one level at a
+time instead of paging the full hierarchy. Pass an empty request for root objects;
+subsequent calls supply `ParentGobjectId`, `ParentTagName`, or
+`ParentContainedPath`. Each child's `ChildHasChildren[i]` tells you whether to
+draw an expand triangle. Filter fields match `DiscoverHierarchy`. See
+[Galaxy Repository](../../docs/GalaxyRepository.md#browsechildren) for full
+request and filter semantics.
+
+```csharp
+BrowseChildrenReply roots = await repository.BrowseChildrenAsync(
+    new BrowseChildrenRequest());
+
+for (int i = 0; i < roots.Children.Count; i++)
+{
+    GalaxyObject child = roots.Children[i];
+    bool hasChildren = roots.ChildHasChildren[i];
+    Console.WriteLine($"{child.TagName} expand={hasChildren}");
+}
+```
+
+#### High-level walker
+
+For UI trees, the client provides a `LazyBrowseNode` walker that handles
+sibling pagination and the `child_has_children` hint for you:
+
+```csharp
+await using GalaxyRepositoryClient repository = GalaxyRepositoryClient.Create(
+    new MxGatewayClientOptions { Endpoint = new Uri("http://localhost:5000"), ApiKey = apiKey });
+IReadOnlyList<LazyBrowseNode> roots = await repository.BrowseAsync();
+foreach (LazyBrowseNode root in roots)
+{
+    if (root.HasChildrenHint)
+    {
+        await root.ExpandAsync();
+    }
+    foreach (LazyBrowseNode child in root.Children)
+    {
+        Console.WriteLine($"{child.Object.TagName} ({(child.HasChildrenHint ? "has children" : "leaf")})");
+    }
+}
+```
+
+`ExpandAsync` is idempotent — calling it twice fires only one RPC,
+and is safe under concurrent callers. To refresh after a Galaxy redeploy, call
+`BrowseAsync` again from the root.
+
 ### Watching deploy events
 
 `WatchDeployEventsAsync` opens the `WatchDeployEvents` server-streaming RPC. The
@@ -239,6 +287,17 @@ Use TLS options for a secured gateway:
 dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- smoke --endpoint https://ZB.MOM.WW.MxGateway.example.local:5001 --tls --ca-file C:\certs\mxgateway-ca.pem --server-name ZB.MOM.WW.MxGateway.example.local --api-key-env MXGATEWAY_API_KEY --item Area001.Pump001.Speed --json
 ```
 
+### TLS trust
+
+The gateway can auto-generate its own self-signed certificate (it has no PKI), so
+the client is **lenient by default**: a TLS connection (`UseTls` / `--tls`) with
+no pinned CA accepts whatever certificate the gateway presents. To verify
+instead, pin a CA with `CaCertificatePath` / `--ca-file` (this path also enforces
+the certificate hostname/SAN match), or set `RequireCertificateValidation` to
+force OS/system-trust verification without pinning. Use `ServerNameOverride` /
+`--server-name` when the dialed host differs from the certificate SAN. See
+[Gateway Configuration](../../docs/GatewayConfiguration.md#automatic-self-signed-certificate).
+
 ## Integration Checks
 
 Run live checks only when a gateway and MXAccess-backed worker are available:
@@ -251,6 +310,29 @@ $env:MXGATEWAY_TEST_ITEM = 'Area001.Pump001.Speed'
 dotnet run --project clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli -- smoke --endpoint $env:MXGATEWAY_ENDPOINT --api-key-env MXGATEWAY_API_KEY --item $env:MXGATEWAY_TEST_ITEM --json
 ```
 
+## Installing as a NuGet Package
+
+The client publishes to the internal Gitea NuGet feed at
+`https://gitea.dohertylan.com/api/packages/dohertj2/nuget/index.json`.
+
+Add the feed once:
+
+````bash
+dotnet nuget add source https://gitea.dohertylan.com/api/packages/dohertj2/nuget/index.json \
+    --name dohertj2-gitea \
+    --username <gitea-username> \
+    --password <gitea-token-or-password> \
+    --store-password-in-clear-text
+````
+
+Then add the package to your project:
+
+````bash
+dotnet add package ZB.MOM.WW.MxGateway.Client --version 0.1.0
+````
+
+The `ZB.MOM.WW.MxGateway.Contracts` package is pulled in transitively.
+
 ## Related Documentation
 
 - [Client Packaging](../../docs/ClientPackaging.md)

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli/CliArguments.cs

@@ -44,6 +44,7 @@ internal sealed class CliArguments
 
     /// <summary>Returns whether the named flag was present in the arguments.</summary>
     /// <param name="name">The flag name (without '--' prefix).</param>
+    /// <returns>True if the flag was present; otherwise false.</returns>
     public bool HasFlag(string name)
     {
         return _flags.Contains(name);
@@ -51,6 +52,7 @@ internal sealed class CliArguments
 
     /// <summary>Returns the value for a named argument, or <c>null</c> if absent.</summary>
     /// <param name="name">The argument name (without '--' prefix).</param>
+    /// <returns>The argument value, or null if the argument was not provided.</returns>
     public string? GetOptional(string name)
     {
         return _values.TryGetValue(name, out string? value)
@@ -60,6 +62,7 @@ internal sealed class CliArguments
 
     /// <summary>Returns the value for a required named argument, or throws if absent.</summary>
     /// <param name="name">The argument name (without '--' prefix).</param>
+    /// <returns>The argument value.</returns>
     public string GetRequired(string name)
     {
         string? value = GetOptional(name);
@@ -74,6 +77,7 @@ internal sealed class CliArguments
     /// <summary>Parses and returns an int32 argument, or the default value if absent.</summary>
     /// <param name="name">The argument name (without '--' prefix).</param>
     /// <param name="defaultValue">The default value if the argument is absent; if <c>null</c>, the argument is required.</param>
+    /// <returns>The parsed int32 value, or the default if absent.</returns>
     public int GetInt32(string name, int? defaultValue = null)
     {
         string? value = GetOptional(name);
@@ -93,6 +97,7 @@ internal sealed class CliArguments
     /// <summary>Parses and returns a uint32 argument, or the default value if absent.</summary>
     /// <param name="name">The argument name (without '--' prefix).</param>
     /// <param name="defaultValue">The default value if the argument is absent.</param>
+    /// <returns>The parsed uint32 value, or the default if absent.</returns>
     public uint GetUInt32(string name, uint defaultValue)
     {
         string? value = GetOptional(name);
@@ -104,6 +109,7 @@ internal sealed class CliArguments
     /// <summary>Parses and returns a uint64 argument, or the default value if absent.</summary>
     /// <param name="name">The argument name (without '--' prefix).</param>
     /// <param name="defaultValue">The default value if the argument is absent.</param>
+    /// <returns>The parsed uint64 value, or the default if absent.</returns>
     public ulong GetUInt64(string name, ulong defaultValue)
     {
         string? value = GetOptional(name);
@@ -115,6 +121,7 @@ internal sealed class CliArguments
     /// <summary>Parses and returns a TimeSpan argument, or the default value if absent. Supports "ms", "s", and standard TimeSpan format.</summary>
     /// <param name="name">The argument name (without '--' prefix).</param>
     /// <param name="defaultValue">The default value if the argument is absent.</param>
+    /// <returns>The parsed TimeSpan value, or the default if absent.</returns>
     public TimeSpan GetDuration(string name, TimeSpan defaultValue)
     {
         string? value = GetOptional(name);

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli/MxGatewayCliClientAdapter.cs

@@ -100,7 +100,8 @@ internal sealed class MxGatewayCliClientAdapter : IMxGatewayCliClient
         return _galaxyClient.Value.WatchDeployEventsRawAsync(request, cancellationToken);
     }
 
-    /// <inheritdoc />
+    /// <summary>Disposes the galaxy client (if created) and the underlying gateway client.</summary>
+    /// <returns>A value task that completes when both clients are disposed.</returns>
     public async ValueTask DisposeAsync()
     {
         if (_galaxyClient.IsValueCreated)

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli/MxGatewayCliSecretRedactor.cs

@@ -6,6 +6,7 @@ internal static class MxGatewayCliSecretRedactor
     /// <summary>Replaces occurrences of the API key in the value with a redacted placeholder.</summary>
     /// <param name="value">The message text to redact.</param>
     /// <param name="apiKey">The API key to remove; no redaction if null or empty.</param>
+    /// <returns>The message text with any API key occurrence replaced by <c>[redacted]</c>.</returns>
     public static string Redact(string value, string? apiKey)
     {
         if (string.IsNullOrEmpty(value) || string.IsNullOrEmpty(apiKey))

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Cli/MxGatewayClientCli.cs

@@ -22,6 +22,7 @@ public static class MxGatewayClientCli
     /// <param name="args">Command-line arguments (command name followed by options).</param>
     /// <param name="standardOutput">TextWriter for command output.</param>
     /// <param name="standardError">TextWriter for error messages.</param>
+    /// <returns>The process exit code (0 for success, 1 for error).</returns>
     public static int Run(
         string[] args,
         TextWriter standardOutput,
@@ -38,6 +39,7 @@ public static class MxGatewayClientCli
     /// <param name="standardError">TextWriter for error messages.</param>
     /// <param name="clientFactory">Optional factory to create the gateway client; defaults to MxGatewayClient.Create.</param>
     /// <param name="standardInput">Optional TextReader for batch-mode stdin; defaults to <see cref="Console.In"/>.</param>
+    /// <returns>A task that resolves to the process exit code (0 for success, 1 for error).</returns>
     public static Task<int> RunAsync(
         string[] args,
         TextWriter standardOutput,
@@ -487,7 +489,7 @@ public static class MxGatewayClientCli
         ReadBulkCommand command = new()
         {
             ServerHandle = arguments.GetInt32("server-handle"),
-            TimeoutMs = (uint)arguments.GetInt32("timeout-ms", 0),
+            TimeoutMs = ParseTimeoutMs(arguments, defaultValue: 0),
         };
         command.TagAddresses.Add(ParseStringList(arguments.GetRequired("items")));
 
@@ -692,6 +694,49 @@ public static class MxGatewayClientCli
         }
     }
 
+    /// <summary>
+    ///     Parses the optional <c>--timeout-ms</c> argument as a non-negative
+    ///     unsigned millisecond count. Mirrors the SDK-side <c>(uint)Math.Min</c>
+    ///     guard on <c>MxGatewaySession.ReadBulkAsync</c>: a negative value
+    ///     (e.g. <c>-1</c>, an easy copy-paste mistake for "unbounded") is
+    ///     rejected loudly rather than silently wrapped to <c>~49.7 days</c>,
+    ///     which would park one worker thread per pending tag for hours.
+    ///     Resolves Client.Dotnet-021.
+    /// </summary>
+    private static uint ParseTimeoutMs(CliArguments arguments, int defaultValue)
+    {
+        int raw = arguments.GetInt32("timeout-ms", defaultValue);
+        if (raw < 0)
+        {
+            throw new ArgumentException(
+                "--timeout-ms must be a non-negative integer (use 0 for the gateway default).");
+        }
+
+        return (uint)raw;
+    }
+
+    /// <summary>
+    ///     Extracts the <c>ServerHandle</c> from a Register reply, throwing a
+    ///     descriptive <see cref="MxGatewayException"/> when the typed
+    ///     <c>Register</c> payload is absent on an otherwise-successful reply.
+    ///     The typed sub-message is the contract for the Register command, so
+    ///     its absence must not silently fall through to
+    ///     <c>ReturnValue.Int32Value</c> (which would be <c>0</c> for an empty
+    ///     reply, driving the rest of the bench against an invalid handle).
+    ///     Resolves Client.Dotnet-019.
+    /// </summary>
+    private static int RequireRegisterServerHandle(MxCommandReply reply, string sessionId)
+    {
+        if (reply.Register is null)
+        {
+            throw new MxGatewayException(
+                $"Gateway reply for Register on session '{sessionId}' (correlation '{reply.CorrelationId}') "
+                + "succeeded but is missing the typed 'register' payload required to read ServerHandle.");
+        }
+
+        return reply.Register.ServerHandle;
+    }
+
     /// <summary>
     ///     Cross-language stress benchmark for ReadBulk. Opens its own session,
     ///     subscribes to N tags so the worker's MxAccessValueCache populates from
@@ -712,7 +757,7 @@ public static class MxGatewayClientCli
         int tagStart = arguments.GetInt32("tag-start", 1);
         string tagPrefix = arguments.GetOptional("tag-prefix") ?? "TestMachine_";
         string tagAttribute = arguments.GetOptional("tag-attribute") ?? "TestChangingInt";
-        uint timeoutMs = (uint)arguments.GetInt32("timeout-ms", 1500);
+        uint timeoutMs = ParseTimeoutMs(arguments, defaultValue: 1500);
         string clientName = arguments.GetOptional("client-name") ?? "mxgw-dotnet-bench";
 
         string[] tags = new string[bulkSize];
@@ -742,7 +787,7 @@ public static class MxGatewayClientCli
                     }),
                     cancellationToken)
                 .ConfigureAwait(false);
-            int serverHandle = registerReply.Register?.ServerHandle ?? registerReply.ReturnValue.Int32Value;
+            int serverHandle = RequireRegisterServerHandle(registerReply, sessionId);
 
             SubscribeBulkCommand subscribe = new() { ServerHandle = serverHandle };
             subscribe.TagAddresses.Add(tags);
@@ -801,8 +846,13 @@ public static class MxGatewayClientCli
                         .ConfigureAwait(false);
                     sw.Stop();
                 }
-                catch
+                catch (Exception ex) when (ex is not OperationCanceledException)
                 {
+                    // Client.Dotnet-020: never swallow OperationCanceledException
+                    // here. A bare `catch` would let Ctrl+C / parent CTS /
+                    // wall-clock timeouts keep spinning until --duration-seconds
+                    // elapsed, burning CPU and skewing the p99/max latency numbers
+                    // with hundreds of immediate-OCE iterations.
                     sw.Stop();
                     failedCalls++;
                     latencyMillis.Add(sw.Elapsed.TotalMilliseconds);

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/BrowseChildrenSmokeTests.cs

@@ -0,0 +1,35 @@
+using Grpc.Core;
+using Grpc.Net.Client;
+using ZB.MOM.WW.MxGateway.Contracts.Proto.Galaxy;
+
+namespace ZB.MOM.WW.MxGateway.Client.Tests;
+
+/// <summary>
+/// Live smoke tests for the BrowseChildren RPC. Skipped by default; set
+/// MXGATEWAY_API_KEY and MXGATEWAY_ENDPOINT to run against a real gateway.
+/// </summary>
+public sealed class BrowseChildrenSmokeTests
+{
+    /// <summary>
+    /// Verifies that BrowseChildren returns a non-zero cache sequence and
+    /// a consistent children/child-has-children count from a live gateway.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact(Skip = "Set MXGATEWAY_API_KEY and MXGATEWAY_ENDPOINT to enable.")]
+    public async Task BrowseChildren_LiveGateway_ReturnsRootsWithCacheSequence()
+    {
+        string? apiKey = Environment.GetEnvironmentVariable("MXGATEWAY_API_KEY");
+        string endpoint = Environment.GetEnvironmentVariable("MXGATEWAY_ENDPOINT") ?? "http://localhost:5120";
+
+        Assert.False(string.IsNullOrEmpty(apiKey), "MXGATEWAY_API_KEY must be set.");
+
+        using GrpcChannel channel = GrpcChannel.ForAddress(endpoint);
+        GalaxyRepository.GalaxyRepositoryClient client = new(channel);
+
+        Metadata headers = new() { { "authorization", $"Bearer {apiKey}" } };
+        BrowseChildrenReply reply = await client.BrowseChildrenAsync(new BrowseChildrenRequest(), headers);
+
+        Assert.True(reply.CacheSequence > 0UL);
+        Assert.Equal(reply.Children.Count, reply.ChildHasChildren.Count);
+    }
+}

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/FakeGalaxyRepositoryTransport.cs

@@ -8,14 +8,10 @@ namespace ZB.MOM.WW.MxGateway.Client.Tests;
 /// </summary>
 internal sealed class FakeGalaxyRepositoryTransport(MxGatewayClientOptions options) : IGalaxyRepositoryClientTransport
 {
-    /// <summary>
-    /// Gets the gateway client options.
-    /// </summary>
+    /// <inheritdoc />
     public MxGatewayClientOptions Options { get; } = options;
 
-    /// <summary>
-    /// Gets the raw gRPC client; always null for the fake.
-    /// </summary>
+    /// <inheritdoc />
     public GalaxyRepository.GalaxyRepositoryClient? RawClient => null;
 
     /// <summary>
@@ -48,6 +44,7 @@ internal sealed class FakeGalaxyRepositoryTransport(MxGatewayClientOptions optio
     /// </summary>
     public DiscoverHierarchyReply DiscoverHierarchyReply { get; set; } = new();
 
+    /// <summary>Gets the queue of discover hierarchy replies; dequeued in FIFO order.</summary>
     public Queue<DiscoverHierarchyReply> DiscoverHierarchyReplies { get; } = new();
 
     /// <summary>
@@ -65,11 +62,7 @@ internal sealed class FakeGalaxyRepositoryTransport(MxGatewayClientOptions optio
     /// </summary>
     public Queue<Exception> DiscoverHierarchyExceptions { get; } = new();
 
-    /// <summary>
-    /// Records the request and either throws a queued exception or returns the configured reply.
-    /// </summary>
-    /// <param name="request">The TestConnectionRequest to process.</param>
-    /// <param name="callOptions">Call options specifying RPC behavior.</param>
+    /// <inheritdoc />
     public Task<TestConnectionReply> TestConnectionAsync(
         TestConnectionRequest request,
         CallOptions callOptions)
@@ -83,11 +76,7 @@ internal sealed class FakeGalaxyRepositoryTransport(MxGatewayClientOptions optio
         return Task.FromResult(TestConnectionReply);
     }
 
-    /// <summary>
-    /// Records the request and either throws a queued exception or returns the configured reply.
-    /// </summary>
-    /// <param name="request">The GetLastDeployTimeRequest to process.</param>
-    /// <param name="callOptions">Call options specifying RPC behavior.</param>
+    /// <inheritdoc />
     public Task<GetLastDeployTimeReply> GetLastDeployTimeAsync(
         GetLastDeployTimeRequest request,
         CallOptions callOptions)
@@ -101,11 +90,7 @@ internal sealed class FakeGalaxyRepositoryTransport(MxGatewayClientOptions optio
         return Task.FromResult(GetLastDeployTimeReply);
     }
 
-    /// <summary>
-    /// Records the request and either throws a queued exception or returns the configured reply.
-    /// </summary>
-    /// <param name="request">The DiscoverHierarchyRequest to process.</param>
-    /// <param name="callOptions">Call options specifying RPC behavior.</param>
+    /// <inheritdoc />
     public Task<DiscoverHierarchyReply> DiscoverHierarchyAsync(
         DiscoverHierarchyRequest request,
         CallOptions callOptions)
@@ -122,6 +107,35 @@ internal sealed class FakeGalaxyRepositoryTransport(MxGatewayClientOptions optio
                 : DiscoverHierarchyReply);
     }
 
+    /// <summary>Records BrowseChildren RPC calls made by the client.</summary>
+    public List<(BrowseChildrenRequest Request, CallOptions CallOptions)> BrowseChildrenCalls { get; } = [];
+
+    /// <summary>Default reply returned from BrowseChildren when the queue is empty.</summary>
+    public BrowseChildrenReply BrowseChildrenReply { get; set; } = new();
+
+    /// <summary>Queue of replies returned from BrowseChildren; dequeued in FIFO order.</summary>
+    public Queue<BrowseChildrenReply> BrowseChildrenReplies { get; } = new();
+
+    /// <summary>Queue of exceptions to throw from BrowseChildren; dequeued in FIFO order.</summary>
+    public Queue<Exception> BrowseChildrenExceptions { get; } = new();
+
+    /// <inheritdoc />
+    public Task<BrowseChildrenReply> BrowseChildrenAsync(
+        BrowseChildrenRequest request,
+        CallOptions callOptions)
+    {
+        BrowseChildrenCalls.Add((request, callOptions));
+        if (BrowseChildrenExceptions.TryDequeue(out Exception? exception))
+        {
+            return Task.FromException<BrowseChildrenReply>(exception);
+        }
+
+        return Task.FromResult(
+            BrowseChildrenReplies.TryDequeue(out BrowseChildrenReply? reply)
+                ? reply
+                : BrowseChildrenReply);
+    }
+
     /// <summary>
     /// Gets the list of WatchDeployEvents RPC calls made by the client.
     /// </summary>
@@ -143,11 +157,7 @@ internal sealed class FakeGalaxyRepositoryTransport(MxGatewayClientOptions optio
     /// </summary>
     public Func<CancellationToken, Task>? WatchDeployEventsBeforeYield { get; set; }
 
-    /// <summary>
-    /// Records the request and streams events, checking for queued exceptions and calling WatchDeployEventsBeforeYield before each event.
-    /// </summary>
-    /// <param name="request">The WatchDeployEventsRequest to process.</param>
-    /// <param name="callOptions">Call options specifying RPC behavior.</param>
+    /// <inheritdoc />
     public async IAsyncEnumerable<DeployEvent> WatchDeployEventsAsync(
         WatchDeployEventsRequest request,
         CallOptions callOptions)

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/FakeGatewayTransport.cs

@@ -11,14 +11,10 @@ internal sealed class FakeGatewayTransport(MxGatewayClientOptions options) : IMx
     private readonly Queue<MxCommandReply> _invokeReplies = new();
     private readonly List<MxEvent> _events = [];
 
-    /// <summary>
-    /// Gets the gateway client options.
-    /// </summary>
+    /// <inheritdoc />
     public MxGatewayClientOptions Options { get; } = options;
 
-    /// <summary>
-    /// Gets null, since this is a test fake without a real gRPC client.
-    /// </summary>
+    /// <inheritdoc />
     public MxAccessGateway.MxAccessGatewayClient? RawClient => null;
 
     /// <summary>
@@ -102,11 +98,7 @@ internal sealed class FakeGatewayTransport(MxGatewayClientOptions options) : IMx
     /// </summary>
     public Queue<Exception> InvokeExceptions { get; } = new();
 
-    /// <summary>
-    /// Verifies that the OpenSessionAsync call is recorded and returns the configured reply.
-    /// </summary>
-    /// <param name="request">The OpenSessionRequest to process.</param>
-    /// <param name="callOptions">Call options specifying RPC behavior.</param>
+    /// <inheritdoc />
     public Task<OpenSessionReply> OpenSessionAsync(
         OpenSessionRequest request,
         CallOptions callOptions)
@@ -120,11 +112,7 @@ internal sealed class FakeGatewayTransport(MxGatewayClientOptions options) : IMx
         return Task.FromResult(OpenSessionReply);
     }
 
-    /// <summary>
-    /// Verifies that the CloseSessionAsync call is recorded and returns the configured reply.
-    /// </summary>
-    /// <param name="request">The CloseSessionRequest to process.</param>
-    /// <param name="callOptions">Call options specifying RPC behavior.</param>
+    /// <inheritdoc />
     public Task<CloseSessionReply> CloseSessionAsync(
         CloseSessionRequest request,
         CallOptions callOptions)
@@ -138,11 +126,7 @@ internal sealed class FakeGatewayTransport(MxGatewayClientOptions options) : IMx
         return Task.FromResult(CloseSessionReply);
     }
 
-    /// <summary>
-    /// Verifies that the InvokeAsync call is recorded and returns the next enqueued reply.
-    /// </summary>
-    /// <param name="request">The MxCommandRequest to process.</param>
-    /// <param name="callOptions">Call options specifying RPC behavior.</param>
+    /// <inheritdoc />
     public Task<MxCommandReply> InvokeAsync(
         MxCommandRequest request,
         CallOptions callOptions)
@@ -156,11 +140,7 @@ internal sealed class FakeGatewayTransport(MxGatewayClientOptions options) : IMx
         return Task.FromResult(_invokeReplies.Dequeue());
     }
 
-    /// <summary>
-    /// Verifies that the StreamEventsAsync call is recorded and yields all enqueued events.
-    /// </summary>
-    /// <param name="request">The StreamEventsRequest to process.</param>
-    /// <param name="callOptions">Call options specifying RPC behavior.</param>
+    /// <inheritdoc />
     public async IAsyncEnumerable<MxEvent> StreamEventsAsync(
         StreamEventsRequest request,
         CallOptions callOptions)
@@ -193,9 +173,7 @@ internal sealed class FakeGatewayTransport(MxGatewayClientOptions options) : IMx
         _events.Add(gatewayEvent);
     }
 
-    /// <summary>
-    /// Records the acknowledge call and returns the next enqueued reply (or default).
-    /// </summary>
+    /// <inheritdoc />
     public Task<AcknowledgeAlarmReply> AcknowledgeAlarmAsync(
         AcknowledgeAlarmRequest request,
         CallOptions callOptions)
@@ -216,9 +194,7 @@ internal sealed class FakeGatewayTransport(MxGatewayClientOptions options) : IMx
             });
     }
 
-    /// <summary>
-    /// Records the query call and yields each enqueued snapshot.
-    /// </summary>
+    /// <inheritdoc />
     public async IAsyncEnumerable<ActiveAlarmSnapshot> QueryActiveAlarmsAsync(
         QueryActiveAlarmsRequest request,
         CallOptions callOptions)
@@ -234,20 +210,20 @@ internal sealed class FakeGatewayTransport(MxGatewayClientOptions options) : IMx
     }
 
     /// <summary>Enqueues an acknowledge reply.</summary>
+    /// <param name="reply">The acknowledge reply to enqueue.</param>
     public void AddAcknowledgeReply(AcknowledgeAlarmReply reply)
     {
         _acknowledgeReplies.Enqueue(reply);
     }
 
     /// <summary>Enqueues a snapshot to be yielded from QueryActiveAlarmsAsync.</summary>
+    /// <param name="snapshot">The snapshot to enqueue.</param>
     public void AddActiveAlarmSnapshot(ActiveAlarmSnapshot snapshot)
     {
         _activeAlarmSnapshots.Add(snapshot);
     }
 
-    /// <summary>
-    /// Records the stream-alarms call and yields each enqueued feed message.
-    /// </summary>
+    /// <inheritdoc />
     public async IAsyncEnumerable<AlarmFeedMessage> StreamAlarmsAsync(
         StreamAlarmsRequest request,
         CallOptions callOptions)
@@ -263,6 +239,7 @@ internal sealed class FakeGatewayTransport(MxGatewayClientOptions options) : IMx
     }
 
     /// <summary>Enqueues an alarm feed message to be yielded from StreamAlarmsAsync.</summary>
+    /// <param name="message">The alarm feed message to enqueue.</param>
     public void AddAlarmFeedMessage(AlarmFeedMessage message)
     {
         _alarmFeedMessages.Add(message);

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/GalaxyRepositoryClientTests.cs

@@ -9,6 +9,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that TestConnectionAsync attaches the API key in request metadata and returns the Ok flag.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task TestConnectionAsync_AttachesApiKeyMetadataAndReturnsOkFlag()
     {
@@ -27,6 +28,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that TestConnectionAsync returns false when the server reports NotOk.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task TestConnectionAsync_ReturnsFalseWhenServerReportsNotOk()
     {
@@ -42,6 +44,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that GetLastDeployTimeAsync returns null when the server reports not present.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task GetLastDeployTimeAsync_ReturnsNullWhenNotPresent()
     {
@@ -58,6 +61,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that GetLastDeployTimeAsync returns the timestamp when the server reports it present.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task GetLastDeployTimeAsync_ReturnsTimestampWhenPresent()
     {
@@ -79,6 +83,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that DiscoverHierarchyAsync returns the objects from the server reply.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task DiscoverHierarchyAsync_ReturnsObjectsFromReply()
     {
@@ -141,6 +146,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that DiscoverHierarchyAsync propagates cancellation tokens to the transport.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task DiscoverHierarchyAsync_PropagatesCancellationToTransport()
     {
@@ -161,6 +167,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that TestConnectionAsync retries on transient gRPC failures.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task DiscoverHierarchyAsync_WithRepeatedPageToken_ThrowsProtocolError()
     {
@@ -181,6 +188,10 @@ public sealed class GalaxyRepositoryClientTests
         Assert.Contains("repeated page token", exception.Message, StringComparison.Ordinal);
     }
 
+    /// <summary>
+    /// Verifies that DiscoverHierarchyAsync maps typed filter options correctly to the request.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task DiscoverHierarchyAsync_WithOptions_MapsTypedFilters()
     {
@@ -212,6 +223,10 @@ public sealed class GalaxyRepositoryClientTests
         Assert.True(request.HistorizedOnly);
     }
 
+    /// <summary>
+    /// Verifies that TestConnectionAsync retries on transient gRPC failures.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task TestConnectionAsync_RetriesOnTransientGrpcFailure()
     {
@@ -229,6 +244,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that DiscoverHierarchyAsync retries on transient gRPC failures.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task DiscoverHierarchyAsync_RetriesOnTransientGrpcFailure()
     {
@@ -245,6 +261,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that WatchDeployEventsAsync delivers the bootstrap event.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task WatchDeployEventsAsync_DeliversBootstrapEvent()
     {
@@ -281,6 +298,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that WatchDeployEventsAsync delivers multiple events in order.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task WatchDeployEventsAsync_DeliversMultipleEventsInOrder()
     {
@@ -319,6 +337,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that WatchDeployEventsAsync stops iteration cleanly when cancelled.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task WatchDeployEventsAsync_CancellationStopsIterationCleanly()
     {
@@ -363,6 +382,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that WatchDeployEventsAsync throws ObjectDisposedException after the client is disposed.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task WatchDeployEventsAsync_ThrowsAfterDisposal()
     {
@@ -378,6 +398,7 @@ public sealed class GalaxyRepositoryClientTests
     /// <summary>
     /// Verifies that TestConnectionAsync throws ObjectDisposedException after the client is disposed.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task TestConnectionAsync_ThrowsAfterDisposal()
     {

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/LazyBrowseNodeTests.cs

@@ -0,0 +1,228 @@
+using Grpc.Core;
+using ZB.MOM.WW.MxGateway.Contracts.Proto.Galaxy;
+
+namespace ZB.MOM.WW.MxGateway.Client.Tests;
+
+/// <summary>
+/// Tests for the <see cref="LazyBrowseNode"/> walker over the BrowseChildren RPC.
+/// </summary>
+public sealed class LazyBrowseNodeTests
+{
+    /// <summary>
+    /// Verifies that calling BrowseAsync with no parent returns the root nodes
+    /// from the first BrowseChildren reply and surfaces the per-child has-children hint.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task Browse_NoParent_ReturnsRoots()
+    {
+        FakeGalaxyRepositoryTransport transport = CreateTransport();
+        transport.BrowseChildrenReplies.Enqueue(BuildReply(
+            children: [BuildObject(1, "Plant", isArea: true), BuildObject(2, "Other")],
+            childHasChildren: [true, false],
+            cacheSequence: 1));
+        await using GalaxyRepositoryClient client = CreateClient(transport);
+
+        IReadOnlyList<LazyBrowseNode> roots = await client.BrowseAsync();
+
+        Assert.Equal(2, roots.Count);
+        Assert.Equal("Plant", roots[0].Object.TagName);
+        Assert.True(roots[0].HasChildrenHint);
+        Assert.False(roots[0].IsExpanded);
+        Assert.Equal("Other", roots[1].Object.TagName);
+        Assert.False(roots[1].HasChildrenHint);
+        Assert.False(roots[1].IsExpanded);
+    }
+
+    /// <summary>
+    /// Verifies that ExpandAsync populates Children and marks the node expanded after one RPC.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task Expand_PopulatesChildrenAndMarksExpanded()
+    {
+        FakeGalaxyRepositoryTransport transport = CreateTransport();
+        transport.BrowseChildrenReplies.Enqueue(BuildReply(
+            children: [BuildObject(1, "Plant", isArea: true)],
+            childHasChildren: [true],
+            cacheSequence: 1));
+        transport.BrowseChildrenReplies.Enqueue(BuildReply(
+            children: [BuildObject(10, "Line1")],
+            childHasChildren: [false],
+            cacheSequence: 1));
+        await using GalaxyRepositoryClient client = CreateClient(transport);
+
+        IReadOnlyList<LazyBrowseNode> roots = await client.BrowseAsync();
+        await roots[0].ExpandAsync();
+
+        Assert.True(roots[0].IsExpanded);
+        Assert.Single(roots[0].Children);
+        Assert.Equal("Line1", roots[0].Children[0].Object.TagName);
+        Assert.Equal(2, transport.BrowseChildrenCalls.Count);
+    }
+
+    /// <summary>
+    /// Verifies that a second ExpandAsync call is a no-op and issues no additional RPC.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task Expand_CalledTwice_NoSecondRpc()
+    {
+        FakeGalaxyRepositoryTransport transport = CreateTransport();
+        transport.BrowseChildrenReplies.Enqueue(BuildReply(
+            children: [BuildObject(1, "Plant", isArea: true)],
+            childHasChildren: [true],
+            cacheSequence: 1));
+        transport.BrowseChildrenReplies.Enqueue(BuildReply(
+            children: [BuildObject(10, "Line1")],
+            childHasChildren: [false],
+            cacheSequence: 1));
+        await using GalaxyRepositoryClient client = CreateClient(transport);
+
+        IReadOnlyList<LazyBrowseNode> roots = await client.BrowseAsync();
+        await roots[0].ExpandAsync();
+        await roots[0].ExpandAsync();
+
+        Assert.Equal(2, transport.BrowseChildrenCalls.Count);
+    }
+
+    /// <summary>
+    /// Verifies that an RPC failure (NotFound) during expand is wrapped in MxGatewayException.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task Expand_UnknownParent_ThrowsMxGatewayException()
+    {
+        FakeGalaxyRepositoryTransport transport = CreateTransport();
+        transport.BrowseChildrenReplies.Enqueue(BuildReply(
+            children: [BuildObject(1, "Plant", isArea: true)],
+            childHasChildren: [true],
+            cacheSequence: 1));
+        await using GalaxyRepositoryClient client = CreateClient(transport);
+
+        IReadOnlyList<LazyBrowseNode> roots = await client.BrowseAsync();
+
+        // Queue the failure for the upcoming ExpandAsync call so it consumes
+        // the exception on its first RPC rather than the BrowseAsync above.
+        transport.BrowseChildrenExceptions.Enqueue(
+            new MxGatewayException(
+                "Parent not found",
+                new RpcException(new Status(StatusCode.NotFound, "Parent not found"))));
+
+        await Assert.ThrowsAsync<MxGatewayException>(async () => await roots[0].ExpandAsync());
+        Assert.False(roots[0].IsExpanded);
+        Assert.Empty(roots[0].Children);
+    }
+
+    /// <summary>
+    /// Verifies that ExpandAsync drains multi-page sibling replies and forwards the page token.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task Expand_MultiPageSiblings_GathersAllPages()
+    {
+        FakeGalaxyRepositoryTransport transport = CreateTransport();
+        // Roots
+        transport.BrowseChildrenReplies.Enqueue(BuildReply(
+            children: [BuildObject(7, "Plant", isArea: true)],
+            childHasChildren: [true],
+            cacheSequence: 1));
+        // First child page (2 children) with a next token
+        BrowseChildrenReply childPage1 = BuildReply(
+            children: [BuildObject(70, "ChildA"), BuildObject(71, "ChildB")],
+            childHasChildren: [false, false],
+            cacheSequence: 1);
+        childPage1.NextPageToken = "7:abc:2";
+        transport.BrowseChildrenReplies.Enqueue(childPage1);
+        // Second child page (1 child) with no next token
+        transport.BrowseChildrenReplies.Enqueue(BuildReply(
+            children: [BuildObject(72, "ChildC")],
+            childHasChildren: [false],
+            cacheSequence: 1));
+        await using GalaxyRepositoryClient client = CreateClient(transport);
+
+        IReadOnlyList<LazyBrowseNode> roots = await client.BrowseAsync();
+        await roots[0].ExpandAsync();
+
+        Assert.Equal(3, roots[0].Children.Count);
+        Assert.Equal(3, transport.BrowseChildrenCalls.Count);
+        Assert.Equal("7:abc:2", transport.BrowseChildrenCalls[2].Request.PageToken);
+    }
+
+    /// <summary>
+    /// Verifies that ten concurrent ExpandAsync calls issue exactly one RPC, not ten.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task Expand_CalledConcurrently_OnlyFiresOneRpc()
+    {
+        FakeGalaxyRepositoryTransport transport = CreateTransport();
+        transport.BrowseChildrenReplies.Enqueue(BuildReply(
+            children: [BuildObject(1, "Plant", isArea: true)],
+            childHasChildren: [true],
+            cacheSequence: 7));
+        transport.BrowseChildrenReplies.Enqueue(BuildReply(
+            children: [BuildObject(2, "Mixer_001")],
+            childHasChildren: [false],
+            cacheSequence: 7));
+
+        await using GalaxyRepositoryClient client = CreateClient(transport);
+        IReadOnlyList<LazyBrowseNode> roots = await client.BrowseAsync();
+
+        // Fire ten concurrent expands of the same node.
+        Task[] tasks = Enumerable.Range(0, 10)
+            .Select(_ => roots[0].ExpandAsync())
+            .ToArray();
+        await Task.WhenAll(tasks);
+
+        Assert.True(roots[0].IsExpanded);
+        Assert.Single(roots[0].Children);
+        // 1 roots fetch + exactly 1 expand fetch = 2 total
+        Assert.Equal(2, transport.BrowseChildrenCalls.Count);
+    }
+
+    /// <summary>
+    /// Verifies that BrowseChildrenOptions filter fields are forwarded to the BrowseChildren request.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task Browse_WithFilter_ForwardsToRequest()
+    {
+        FakeGalaxyRepositoryTransport transport = CreateTransport();
+        await using GalaxyRepositoryClient client = CreateClient(transport);
+
+        await client.BrowseAsync(new BrowseChildrenOptions
+        {
+            TagNameGlob = "Mixer*",
+            AlarmBearingOnly = true,
+        });
+
+        BrowseChildrenRequest request = Assert.Single(transport.BrowseChildrenCalls).Request;
+        Assert.Equal("Mixer*", request.TagNameGlob);
+        Assert.True(request.AlarmBearingOnly);
+    }
+
+    private static GalaxyObject BuildObject(int id, string tag, bool isArea = false)
+        => new() { GobjectId = id, TagName = tag, BrowseName = tag, IsArea = isArea };
+
+    private static BrowseChildrenReply BuildReply(
+        IReadOnlyList<GalaxyObject> children,
+        IReadOnlyList<bool> childHasChildren,
+        ulong cacheSequence)
+    {
+        BrowseChildrenReply reply = new() { TotalChildCount = children.Count, CacheSequence = cacheSequence };
+        reply.Children.AddRange(children);
+        reply.ChildHasChildren.AddRange(childHasChildren);
+        return reply;
+    }
+
+    private static GalaxyRepositoryClient CreateClient(FakeGalaxyRepositoryTransport transport)
+        => new(transport.Options, transport);
+
+    private static FakeGalaxyRepositoryTransport CreateTransport()
+        => new(new MxGatewayClientOptions
+        {
+            Endpoint = new Uri("http://localhost:5000"),
+            ApiKey = "test-api-key",
+        });
+}

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/MxGatewayClientAlarmsTests.cs

@@ -11,6 +11,8 @@ namespace ZB.MOM.WW.MxGateway.Client.Tests;
 /// </summary>
 public sealed class MxGatewayClientAlarmsTests
 {
+    /// <summary>AcknowledgeAlarmAsync records request and returns reply.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task AcknowledgeAlarmAsync_RecordsRequestShapeAndReturnsReply()
     {
@@ -46,6 +48,8 @@ public sealed class MxGatewayClientAlarmsTests
         Assert.Equal("Bearer test-api-key", call.CallOptions.Headers?.GetValue("authorization"));
     }
 
+    /// <summary>AcknowledgeAlarmAsync honors cancellation.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task AcknowledgeAlarmAsync_HonorsCancellation()
     {
@@ -69,6 +73,8 @@ public sealed class MxGatewayClientAlarmsTests
                 cancellation.Token));
     }
 
+    /// <summary>AcknowledgeAlarmAsync maps unauthenticated RPC exception to typed exception.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task AcknowledgeAlarmAsync_MapsUnauthenticated_RpcException_ToTypedException()
     {
@@ -93,6 +99,8 @@ public sealed class MxGatewayClientAlarmsTests
         Assert.Equal(StatusCode.Unauthenticated, ex.StatusCode);
     }
 
+    /// <summary>QueryActiveAlarmsAsync streams enqueued snapshots.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task QueryActiveAlarmsAsync_StreamsEnqueuedSnapshots()
     {
@@ -117,6 +125,8 @@ public sealed class MxGatewayClientAlarmsTests
         Assert.Single(transport.QueryActiveAlarmsCalls);
     }
 
+    /// <summary>QueryActiveAlarmsAsync passes filter prefix.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task QueryActiveAlarmsAsync_PassesFilterPrefix()
     {
@@ -136,6 +146,8 @@ public sealed class MxGatewayClientAlarmsTests
         Assert.Equal("Tank01.", call.Request.AlarmFilterPrefix);
     }
 
+    /// <summary>QueryActiveAlarmsAsync honors cancellation during enumeration.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task QueryActiveAlarmsAsync_HonorsCancellationDuringEnumeration()
     {

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/MxGatewayClientCliTests.cs

@@ -24,6 +24,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that the version command with --json flag prints JSON protocol versions.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_VersionJson_PrintsJsonProtocolVersions()
     {
@@ -38,6 +39,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that the write command builds a write request and prints JSON reply.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_Write_BuildsWriteCommandAndPrintsJsonReply()
     {
@@ -83,6 +85,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that error output redacts sensitive API key values.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_ErrorOutput_RedactsApiKey()
     {
@@ -107,6 +110,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that stream-events with max-events limit stops output in non-JSON format.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_StreamEvents_WithMaxEventsStopsNonJsonOutput()
     {
@@ -149,6 +153,7 @@ public sealed class MxGatewayClientCliTests
 
 
     /// <summary>Verifies that stream-alarms with --max-events stops output and distinguishes payload cases.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_StreamAlarms_WithMaxEventsStopsAndDistinguishesPayloadCases()
     {
@@ -188,6 +193,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that acknowledge-alarm builds a request and prints the JSON reply.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_AcknowledgeAlarm_BuildsRequestAndPrintsJsonReply()
     {
@@ -230,6 +236,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that smoke command closes opened session when a command fails.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_Smoke_WhenCommandFails_ClosesOpenedSession()
     {
@@ -261,6 +268,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that galaxy-test-connection command prints JSON reply.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_GalaxyTestConnection_PrintsJsonReply()
     {
@@ -291,6 +299,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that galaxy-discover command prints hierarchy summary.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_GalaxyDiscover_PrintsHierarchySummary()
     {
@@ -361,6 +370,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that galaxy-watch command prints text output for deploy events.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_GalaxyWatch_PrintsTextOutputForEvents()
     {
@@ -415,6 +425,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that galaxy-watch with --json emits one JSON object per event.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_GalaxyWatch_JsonEmitsOneObjectPerEvent()
     {
@@ -450,6 +461,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that batch mode dispatches a single version command and emits the EOR sentinel.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_Batch_DispatchesVersionAndWritesEndOfRecord()
     {
@@ -476,6 +488,7 @@ public sealed class MxGatewayClientCliTests
     }
 
     /// <summary>Verifies that batch mode routes per-command errors to stdout as JSON between EOR markers.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RunAsync_Batch_WritesErrorsToStdoutAsJson()
     {
@@ -509,6 +522,360 @@ public sealed class MxGatewayClientCliTests
         Assert.Contains("gateway-protocol=", text);
     }
 
+    /// <summary>
+    /// Client.Dotnet-018: the README CLI examples for the alarm subcommands at
+    /// `clients/dotnet/README.md` must drive cleanly through the production
+    /// CLI argument parser. The previous text used non-existent flags
+    /// (`--session-id`, `--max-messages`, `--alarm-reference`) that would
+    /// fail with "Unknown command" / "Missing required option --reference".
+    /// Each documented example is extracted from the README, parsed via the
+    /// production <see cref="MxGatewayClientCli.RunAsync"/>, and asserted
+    /// against exit code 0.
+    /// </summary>
+    /// <param name="command">The alarm subcommand to validate (e.g. "stream-alarms", "acknowledge-alarm").</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Theory]
+    [InlineData("stream-alarms")]
+    [InlineData("acknowledge-alarm")]
+    public async Task RunAsync_ReadmeExamples_ForAlarmCommands_ParseSuccessfully(string command)
+    {
+        string readme = LocateClientReadme();
+        string[] commandLine = ExtractReadmeCommandLine(readme, command);
+        // The documented examples do not include --api-key (the README assumes
+        // the env var path documented elsewhere). Inject an API key via the
+        // standard env var so CreateOptions succeeds and the parser fully
+        // exercises the documented flag shape.
+        string? previousKey = Environment.GetEnvironmentVariable("MXGATEWAY_API_KEY");
+        Environment.SetEnvironmentVariable("MXGATEWAY_API_KEY", "test-api-key");
+
+        try
+        {
+            using var output = new StringWriter();
+            using var error = new StringWriter();
+            FakeCliClient fakeClient = new();
+            fakeClient.AlarmFeedMessages.Add(new AlarmFeedMessage
+            {
+                ActiveAlarm = new ActiveAlarmSnapshot { AlarmFullReference = "fixture" },
+            });
+            fakeClient.AcknowledgeAlarmReplies.Enqueue(new AcknowledgeAlarmReply
+            {
+                CorrelationId = "ack-fixture",
+                ProtocolStatus = new ProtocolStatus { Code = ProtocolStatusCode.Ok },
+            });
+
+            int exitCode = await MxGatewayClientCli.RunAsync(
+                commandLine,
+                output,
+                error,
+                _ => fakeClient);
+
+            Assert.True(
+                exitCode == 0,
+                $"README example for '{command}' exited {exitCode}; stderr=<<{error}>>");
+            Assert.DoesNotContain("Unknown command", error.ToString());
+            Assert.DoesNotContain("Missing required option", error.ToString());
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("MXGATEWAY_API_KEY", previousKey);
+        }
+    }
+
+    /// <summary>
+    /// Client.Dotnet-019: `BenchReadBulkAsync` previously fell back to
+    /// <c>reply.ReturnValue.Int32Value</c> when the register reply had no
+    /// typed <c>Register</c> payload, silently driving the rest of the bench
+    /// against a zero server handle. The fix must fail loudly with a
+    /// descriptive <see cref="MxGatewayException"/>.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task RunAsync_BenchReadBulk_WhenRegisterReplyMissingTypedPayload_FailsLoudly()
+    {
+        using var output = new StringWriter();
+        using var error = new StringWriter();
+        FakeCliClient fakeClient = new();
+        // Successful protocol + MX status but no typed `Register` payload.
+        // Before the Client.Dotnet-019 fix this silently became serverHandle=0
+        // and the bench proceeded through SubscribeBulk / warmup / steady-state
+        // against an invalid handle, producing a misleading zero-result summary.
+        fakeClient.InvokeReplies.Enqueue(new MxCommandReply
+        {
+            SessionId = "session-fixture",
+            Kind = MxCommandKind.Register,
+            ProtocolStatus = new ProtocolStatus { Code = ProtocolStatusCode.Ok },
+        });
+
+        int exitCode = await MxGatewayClientCli.RunAsync(
+            [
+                "bench-read-bulk",
+                "--endpoint",
+                "http://localhost:5000",
+                "--api-key",
+                "test-api-key",
+                "--duration-seconds",
+                "1",
+                "--warmup-seconds",
+                "0",
+                "--bulk-size",
+                "1",
+            ],
+            output,
+            error,
+            _ => fakeClient);
+
+        Assert.Equal(1, exitCode);
+        // Descriptive message that names the missing typed payload.
+        string err = error.ToString();
+        Assert.Contains("Register", err);
+        // The bench must not produce any aggregate stats JSON.
+        Assert.DoesNotContain("bench-read-bulk", output.ToString());
+    }
+
+    /// <summary>
+    /// Client.Dotnet-020: the steady-state loop in `BenchReadBulkAsync` had a
+    /// bare `catch { failedCalls++; continue; }` that swallowed
+    /// <see cref="OperationCanceledException"/>, so token-driven cancellation
+    /// kept spinning until <c>--duration-seconds</c> elapsed. After the fix
+    /// the bench must exit promptly when the supplied token cancels.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task RunAsync_BenchReadBulk_WhenSteadyStateLoopReceivesCancellation_ExitsPromptly()
+    {
+        using var output = new StringWriter();
+        using var error = new StringWriter();
+
+        int invokeCount = 0;
+        FakeCliClient fakeClient = new()
+        {
+            InvokeHandler = (request, ct) =>
+            {
+                int n = Interlocked.Increment(ref invokeCount);
+
+                // Reply 1 = Register (success with typed payload).
+                if (request.Command.Kind == MxCommandKind.Register)
+                {
+                    return Task.FromResult(new MxCommandReply
+                    {
+                        SessionId = "session-fixture",
+                        Kind = MxCommandKind.Register,
+                        ProtocolStatus = new ProtocolStatus { Code = ProtocolStatusCode.Ok },
+                        Register = new RegisterReply { ServerHandle = 1 },
+                    });
+                }
+
+                // Reply 2 = SubscribeBulk (success).
+                if (request.Command.Kind == MxCommandKind.SubscribeBulk)
+                {
+                    var subscribeReply = new MxCommandReply
+                    {
+                        SessionId = "session-fixture",
+                        Kind = MxCommandKind.SubscribeBulk,
+                        ProtocolStatus = new ProtocolStatus { Code = ProtocolStatusCode.Ok },
+                        SubscribeBulk = new BulkSubscribeReply(),
+                    };
+                    return Task.FromResult(subscribeReply);
+                }
+
+                // ReadBulk reply 1 = success (so the steady-state loop enters
+                // and starts iterating). Reply 2+ = simulated cancellation.
+                if (request.Command.Kind == MxCommandKind.ReadBulk && n <= 3)
+                {
+                    return Task.FromResult(new MxCommandReply
+                    {
+                        SessionId = "session-fixture",
+                        Kind = MxCommandKind.ReadBulk,
+                        ProtocolStatus = new ProtocolStatus { Code = ProtocolStatusCode.Ok },
+                        ReadBulk = new BulkReadReply(),
+                    });
+                }
+
+                // From here on every ReadBulk throws OCE — the steady-state
+                // loop must exit promptly rather than spinning until
+                // --duration-seconds elapses.
+                throw new OperationCanceledException();
+            },
+        };
+
+        var sw = System.Diagnostics.Stopwatch.StartNew();
+        await Assert.ThrowsAsync<OperationCanceledException>(async () =>
+            await MxGatewayClientCli.RunAsync(
+                [
+                    "bench-read-bulk",
+                    "--endpoint",
+                    "http://localhost:5000",
+                    "--api-key",
+                    "test-api-key",
+                    "--duration-seconds",
+                    "30",
+                    "--warmup-seconds",
+                    "0",
+                    "--bulk-size",
+                    "1",
+                ],
+                output,
+                error,
+                _ => fakeClient));
+        sw.Stop();
+
+        // Without the fix the loop swallows OCE and continues until the 30 s
+        // steady-state deadline expires. With the fix it exits as soon as OCE
+        // surfaces. Generous 10 s ceiling to keep the test stable under load.
+        Assert.True(
+            sw.Elapsed < TimeSpan.FromSeconds(10),
+            $"Bench did not exit promptly on cancellation; took {sw.Elapsed}.");
+    }
+
+    /// <summary>
+    /// Client.Dotnet-021: both `ReadBulkAsync` and `BenchReadBulkAsync` cast
+    /// the user-supplied <c>--timeout-ms</c> to <see cref="uint"/> without
+    /// bounds checking, so a negative value (e.g. <c>-1</c>) silently wraps
+    /// to ~49.7 days. The fix must reject negatives with a clear error.
+    /// </summary>
+    /// <param name="command">The bulk-read subcommand to validate (e.g. "read-bulk", "bench-read-bulk").</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Theory]
+    [InlineData("read-bulk")]
+    [InlineData("bench-read-bulk")]
+    public async Task RunAsync_TimeoutMs_NegativeValue_RejectsWithClearError(string command)
+    {
+        using var output = new StringWriter();
+        using var error = new StringWriter();
+        FakeCliClient fakeClient = new();
+
+        string[] args = command is "read-bulk"
+            ? [
+                "read-bulk",
+                "--endpoint",
+                "http://localhost:5000",
+                "--api-key",
+                "test-api-key",
+                "--session-id",
+                "session-fixture",
+                "--server-handle",
+                "1",
+                "--items",
+                "Area001.Pump001.Speed",
+                "--timeout-ms",
+                "-1",
+            ]
+            : [
+                "bench-read-bulk",
+                "--endpoint",
+                "http://localhost:5000",
+                "--api-key",
+                "test-api-key",
+                "--duration-seconds",
+                "1",
+                "--warmup-seconds",
+                "0",
+                "--bulk-size",
+                "1",
+                "--timeout-ms",
+                "-1",
+            ];
+
+        int exitCode = await MxGatewayClientCli.RunAsync(
+            args,
+            output,
+            error,
+            _ => fakeClient);
+
+        Assert.NotEqual(0, exitCode);
+        string err = error.ToString();
+        Assert.Contains("timeout-ms", err);
+        Assert.Contains("non-negative", err);
+    }
+
+    /// <summary>
+    /// Locates the .NET client README by walking up from the test assembly's
+    /// base directory until <c>clients/dotnet/README.md</c> is found. Keeps
+    /// the regression test independent of the current working directory.
+    /// </summary>
+    private static string LocateClientReadme()
+    {
+        string? directory = AppContext.BaseDirectory;
+        while (!string.IsNullOrEmpty(directory))
+        {
+            string candidate = Path.Combine(directory, "clients", "dotnet", "README.md");
+            if (File.Exists(candidate))
+            {
+                return candidate;
+            }
+
+            directory = Path.GetDirectoryName(directory);
+        }
+
+        throw new FileNotFoundException("clients/dotnet/README.md not found above test assembly base directory.");
+    }
+
+    /// <summary>
+    /// Extracts the documented CLI invocation for the requested subcommand
+    /// from the README, returning only the arguments after the
+    /// <c>mxgw-dotnet</c>-equivalent prefix so they can be passed straight
+    /// to <see cref="MxGatewayClientCli.RunAsync"/>.
+    /// </summary>
+    private static string[] ExtractReadmeCommandLine(string readmePath, string command)
+    {
+        string[] lines = File.ReadAllLines(readmePath);
+        // Look for the documented `dotnet run ... -- <command> ...` line.
+        foreach (string line in lines)
+        {
+            int dashes = line.IndexOf("-- " + command, StringComparison.Ordinal);
+            if (dashes < 0)
+            {
+                continue;
+            }
+
+            string after = line[(dashes + 3)..].Trim();
+            // Tokenize by whitespace, respecting "..." quoted segments.
+            return TokenizeCommandLine(after);
+        }
+
+        throw new InvalidOperationException(
+            $"README at '{readmePath}' has no documented example for subcommand '{command}'.");
+    }
+
+    /// <summary>
+    /// Splits a single command-line string into argv tokens, honouring
+    /// double-quoted segments so paths with embedded spaces survive intact.
+    /// </summary>
+    private static string[] TokenizeCommandLine(string input)
+    {
+        var tokens = new List<string>();
+        var current = new System.Text.StringBuilder();
+        bool inQuotes = false;
+
+        foreach (char ch in input)
+        {
+            if (ch == '"')
+            {
+                inQuotes = !inQuotes;
+                continue;
+            }
+
+            if (!inQuotes && char.IsWhiteSpace(ch))
+            {
+                if (current.Length > 0)
+                {
+                    tokens.Add(current.ToString());
+                    current.Clear();
+                }
+                continue;
+            }
+
+            current.Append(ch);
+        }
+
+        if (current.Length > 0)
+        {
+            tokens.Add(current.ToString());
+        }
+
+        return tokens.ToArray();
+    }
+
     /// <summary>Fake CLI client for testing.</summary>
     private sealed class FakeCliClient : IMxGatewayCliClient
     {
@@ -527,7 +894,11 @@ public sealed class MxGatewayClientCliTests
         /// <summary>Exception to throw on invoke, if any.</summary>
         public Exception? InvokeFailure { get; init; }
 
-        /// <inheritdoc />
+        /// <summary>Optional per-call handler that overrides queue-based behaviour.</summary>
+        public Func<MxCommandRequest, CancellationToken, Task<MxCommandReply>>? InvokeHandler { get; init; }
+
+        /// <summary>Releases resources held by the fake CLI client.</summary>
+        /// <returns>A completed value task.</returns>
         public ValueTask DisposeAsync()
         {
             return ValueTask.CompletedTask;
@@ -572,6 +943,11 @@ public sealed class MxGatewayClientCliTests
                 throw InvokeFailure;
             }
 
+            if (InvokeHandler is not null)
+            {
+                return InvokeHandler(request, cancellationToken);
+            }
+
             return Task.FromResult(InvokeReplies.Dequeue());
         }
 
@@ -632,6 +1008,7 @@ public sealed class MxGatewayClientCliTests
         /// <summary>Galaxy discover hierarchy reply to return.</summary>
         public DiscoverHierarchyReply GalaxyDiscoverHierarchyReply { get; set; } = new();
 
+        /// <summary>Queue of galaxy discover hierarchy replies to return.</summary>
         public Queue<DiscoverHierarchyReply> GalaxyDiscoverHierarchyReplies { get; } = new();
 
         /// <summary>List of received galaxy test connection requests.</summary>

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/MxGatewayClientSessionTests.cs

@@ -7,6 +7,7 @@ namespace ZB.MOM.WW.MxGateway.Client.Tests;
 public sealed class MxGatewayClientSessionTests
 {
     /// <summary>Verifies that open session attaches API key metadata and cancellation token.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task OpenSessionRawAsync_AttachesApiKeyMetadataAndCancellation()
     {
@@ -22,6 +23,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that open session returns a session with the raw open reply.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task OpenSessionAsync_ReturnsSessionWithRawOpenReply()
     {
@@ -37,6 +39,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that register builds a register command and returns server handle.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task RegisterAsync_BuildsRegisterCommandAndReturnsServerHandle()
     {
@@ -62,6 +65,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that add item 2 builds a command with the specified context.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task AddItem2Async_BuildsAddItem2CommandWithContext()
     {
@@ -87,6 +91,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that write raw builds a write command with the raw value.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task WriteRawAsync_BuildsWriteCommandWithRawValue()
     {
@@ -118,6 +123,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that write 2 raw builds a write 2 command with value and timestamp.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Write2RawAsync_BuildsWrite2CommandWithValueAndTimestamp()
     {
@@ -146,6 +152,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that subscribe bulk builds one command and returns per-item results.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task SubscribeBulkAsync_BuildsOneBulkCommandAndReturnsPerItemResults()
     {
@@ -185,6 +192,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that stream events yields events in the order received from the gateway.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task StreamEventsAsync_YieldsEventsInGatewayOrder()
     {
@@ -216,6 +224,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that close is explicit and idempotent.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task CloseAsync_IsExplicitAndIdempotent()
     {
@@ -232,6 +241,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that invoke retries safe diagnostic commands on transient RPC failure.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task InvokeAsync_RetriesSafeDiagnosticCommandOnTransientGrpcFailure()
     {
@@ -256,6 +266,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that open session does not retry on transient RPC failure.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task OpenSessionAsync_DoesNotRetryTransientGrpcFailure()
     {
@@ -269,6 +280,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that invoke does not retry write commands on transient RPC failure.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task InvokeAsync_DoesNotRetryWriteCommand()
     {
@@ -284,6 +296,7 @@ public sealed class MxGatewayClientSessionTests
     }
 
     /// <summary>Verifies that invoke helpers pass cancellation token to the transport.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task InvokeHelpers_PassCancellationTokenToTransport()
     {

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/MxGatewayClientTlsHandlerTests.cs

@@ -0,0 +1,85 @@
+using System.Net.Http;
+using System.Net.Security;
+using ZB.MOM.WW.MxGateway.Client;
+
+namespace ZB.MOM.WW.MxGateway.Client.Tests;
+
+public sealed class MxGatewayClientTlsHandlerTests
+{
+    /// <summary>
+    /// Verifies that when TLS is used with no pinned CA and RequireCertificateValidation is false (default),
+    /// the handler installs an accept-all callback so the gateway's self-signed cert is trusted.
+    /// The callback must return true regardless of chain errors.
+    /// </summary>
+    [Fact]
+    public void Handler_SkipsVerification_WhenTlsAndNoCaPinned()
+    {
+        MxGatewayClientOptions options = new()
+        {
+            Endpoint = new Uri("https://localhost:5120"),
+            ApiKey = "k",
+            UseTls = true,
+        };
+        using SocketsHttpHandler handler = MxGatewayClient.CreateHttpHandlerForTests(options);
+        Assert.NotNull(handler.SslOptions.RemoteCertificateValidationCallback);
+        Assert.True(handler.SslOptions.RemoteCertificateValidationCallback!(null!, null!, null, SslPolicyErrors.RemoteCertificateChainErrors));
+    }
+
+    /// <summary>
+    /// Verifies that when RequireCertificateValidation is true, the callback is left null
+    /// so the OS trust store performs validation.
+    /// </summary>
+    [Fact]
+    public void Handler_KeepsDefaultVerification_WhenRequireCertificateValidation()
+    {
+        MxGatewayClientOptions options = new()
+        {
+            Endpoint = new Uri("https://localhost:5120"),
+            ApiKey = "k",
+            UseTls = true,
+            RequireCertificateValidation = true,
+        };
+        using SocketsHttpHandler handler = MxGatewayClient.CreateHttpHandlerForTests(options);
+        Assert.Null(handler.SslOptions.RemoteCertificateValidationCallback);
+    }
+}
+
+public sealed class GalaxyRepositoryClientTlsHandlerTests
+{
+    /// <summary>
+    /// Verifies that when TLS is used with no pinned CA and RequireCertificateValidation is false (default),
+    /// the Galaxy client handler installs an accept-all callback so the gateway's self-signed cert is trusted.
+    /// The callback must return true regardless of chain errors.
+    /// </summary>
+    [Fact]
+    public void Handler_SkipsVerification_WhenTlsAndNoCaPinned()
+    {
+        MxGatewayClientOptions options = new()
+        {
+            Endpoint = new Uri("https://localhost:5120"),
+            ApiKey = "k",
+            UseTls = true,
+        };
+        using SocketsHttpHandler handler = GalaxyRepositoryClient.CreateHttpHandlerForTests(options);
+        Assert.NotNull(handler.SslOptions.RemoteCertificateValidationCallback);
+        Assert.True(handler.SslOptions.RemoteCertificateValidationCallback!(null!, null!, null, SslPolicyErrors.RemoteCertificateChainErrors));
+    }
+
+    /// <summary>
+    /// Verifies that when RequireCertificateValidation is true, the Galaxy client callback is left null
+    /// so the OS trust store performs validation.
+    /// </summary>
+    [Fact]
+    public void Handler_KeepsDefaultVerification_WhenRequireCertificateValidation()
+    {
+        MxGatewayClientOptions options = new()
+        {
+            Endpoint = new Uri("https://localhost:5120"),
+            ApiKey = "k",
+            UseTls = true,
+            RequireCertificateValidation = true,
+        };
+        using SocketsHttpHandler handler = GalaxyRepositoryClient.CreateHttpHandlerForTests(options);
+        Assert.Null(handler.SslOptions.RemoteCertificateValidationCallback);
+    }
+}

clients/dotnet/ZB.MOM.WW.MxGateway.Client.Tests/MxGatewayGeneratedContractTests.cs

@@ -3,6 +3,7 @@ namespace ZB.MOM.WW.MxGateway.Client.Tests;
 public sealed class MxGatewayGeneratedContractTests
 {
     /// <summary>Verifies that the generated gRPC client can be instantiated from the client factory.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task GeneratedGrpcClient_CanBeConstructedFromClientFactory()
     {

clients/dotnet/ZB.MOM.WW.MxGateway.Client/BrowseChildrenOptions.cs

@@ -0,0 +1,26 @@
+namespace ZB.MOM.WW.MxGateway.Client;
+
+/// <summary>
+///     Filters and shape options for <see cref="GalaxyRepositoryClient.BrowseAsync(BrowseChildrenOptions, System.Threading.CancellationToken)"/>.
+///     Mirror of <see cref="DiscoverHierarchyOptions"/> for the lazy-browse path.
+/// </summary>
+public sealed class BrowseChildrenOptions
+{
+    /// <summary>Restrict to children whose Galaxy category is in this set.</summary>
+    public IReadOnlyList<int> CategoryIds { get; init; } = [];
+
+    /// <summary>Restrict to children whose template chain contains any of these tokens.</summary>
+    public IReadOnlyList<string> TemplateChainContains { get; init; } = [];
+
+    /// <summary>Optional glob-style filter on <c>tag_name</c>.</summary>
+    public string? TagNameGlob { get; init; }
+
+    /// <summary>Whether to populate each <c>GalaxyObject.Attributes</c>. Null leaves the server default.</summary>
+    public bool? IncludeAttributes { get; init; }
+
+    /// <summary>Restrict to children that bear at least one alarm attribute.</summary>
+    public bool AlarmBearingOnly { get; init; }
+
+    /// <summary>Restrict to children that have at least one historized attribute.</summary>
+    public bool HistorizedOnly { get; init; }
+}

clients/dotnet/ZB.MOM.WW.MxGateway.Client/GalaxyRepositoryClient.cs

@@ -19,6 +19,7 @@ namespace ZB.MOM.WW.MxGateway.Client;
 public sealed class GalaxyRepositoryClient : IAsyncDisposable
 {
     private const int DiscoverHierarchyPageSize = 5000;
+    private const int BrowseChildrenPageSize = 500;
 
     private readonly GrpcChannel? _channel;
     private readonly IGalaxyRepositoryClientTransport _transport;
@@ -182,6 +183,10 @@ public sealed class GalaxyRepositoryClient : IAsyncDisposable
         return await DiscoverHierarchyAsync(new DiscoverHierarchyOptions(), cancellationToken).ConfigureAwait(false);
     }
 
+    /// <summary>Discovers the Galaxy object hierarchy.</summary>
+    /// <param name="options">Client configuration options.</param>
+    /// <param name="cancellationToken">Token to observe for cancellation.</param>
+    /// <returns>The collection of Galaxy objects in the hierarchy.</returns>
     public async Task<IReadOnlyList<GalaxyObject>> DiscoverHierarchyAsync(
         DiscoverHierarchyOptions options,
         CancellationToken cancellationToken = default)
@@ -274,6 +279,92 @@ public sealed class GalaxyRepositoryClient : IAsyncDisposable
             cancellationToken);
     }
 
+    /// <summary>Returns root-level browse nodes (objects with no parent).</summary>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>The list of root <see cref="LazyBrowseNode"/> instances.</returns>
+    public Task<IReadOnlyList<LazyBrowseNode>> BrowseAsync(CancellationToken cancellationToken = default)
+        => BrowseAsync(null, cancellationToken);
+
+    /// <summary>Returns root-level browse nodes filtered by the given options.</summary>
+    /// <param name="options">Browse filter options. Null applies no filter.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>The list of root <see cref="LazyBrowseNode"/> instances.</returns>
+    public async Task<IReadOnlyList<LazyBrowseNode>> BrowseAsync(
+        BrowseChildrenOptions? options,
+        CancellationToken cancellationToken = default)
+    {
+        BrowseChildrenOptions effective = options ?? new BrowseChildrenOptions();
+        List<LazyBrowseNode> roots = [];
+        string pageToken = string.Empty;
+        HashSet<string> seenPageTokens = new(StringComparer.Ordinal);
+        do
+        {
+            BrowseChildrenRequest request = BuildBrowseChildrenRequest(effective);
+            request.PageToken = pageToken;
+            BrowseChildrenReply reply = await BrowseChildrenRawAsync(request, cancellationToken).ConfigureAwait(false);
+
+            for (int i = 0; i < reply.Children.Count; i++)
+            {
+                bool hint = i < reply.ChildHasChildren.Count && reply.ChildHasChildren[i];
+                roots.Add(new LazyBrowseNode(this, reply.Children[i], hint, effective));
+            }
+
+            pageToken = reply.NextPageToken;
+            if (!string.IsNullOrWhiteSpace(pageToken) && !seenPageTokens.Add(pageToken))
+            {
+                throw new MxGatewayException(
+                    $"Galaxy BrowseChildren returned a repeated page token '{pageToken}'.");
+            }
+        }
+        while (!string.IsNullOrWhiteSpace(pageToken));
+
+        return roots;
+    }
+
+    /// <summary>Issues a raw BrowseChildren RPC without result wrapping.</summary>
+    /// <param name="request">The browse-children request.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>The raw server reply.</returns>
+    public Task<BrowseChildrenReply> BrowseChildrenRawAsync(
+        BrowseChildrenRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+        ThrowIfDisposed();
+
+        return ExecuteSafeUnaryAsync(
+            token => _transport.BrowseChildrenAsync(request, CreateCallOptions(token)),
+            cancellationToken);
+    }
+
+    /// <summary>Builds a <see cref="BrowseChildrenRequest"/> from the provided options.</summary>
+    /// <param name="options">Browse children options to convert.</param>
+    /// <returns>The constructed request message.</returns>
+    internal static BrowseChildrenRequest BuildBrowseChildrenRequest(BrowseChildrenOptions options)
+    {
+        ArgumentNullException.ThrowIfNull(options);
+
+        BrowseChildrenRequest request = new()
+        {
+            PageSize = BrowseChildrenPageSize,
+            AlarmBearingOnly = options.AlarmBearingOnly,
+            HistorizedOnly = options.HistorizedOnly,
+        };
+        request.CategoryIds.Add(options.CategoryIds);
+        request.TemplateChainContains.Add(options.TemplateChainContains);
+        if (!string.IsNullOrWhiteSpace(options.TagNameGlob))
+        {
+            request.TagNameGlob = options.TagNameGlob;
+        }
+
+        if (options.IncludeAttributes.HasValue)
+        {
+            request.IncludeAttributes = options.IncludeAttributes.Value;
+        }
+
+        return request;
+    }
+
     /// <summary>
     /// Subscribes to Galaxy deploy events. The server emits a bootstrap event with the
     /// current state on subscribe so callers can prime their cache, then emits one event
@@ -336,6 +427,7 @@ public sealed class GalaxyRepositoryClient : IAsyncDisposable
     /// <summary>
     /// Closes the gRPC channel and releases resources.
     /// </summary>
+    /// <returns>A task that represents the asynchronous dispose operation.</returns>
     public ValueTask DisposeAsync()
     {
         if (_disposed)
@@ -402,7 +494,13 @@ public sealed class GalaxyRepositoryClient : IAsyncDisposable
             .ConfigureAwait(false);
     }
 
-    private static HttpMessageHandler CreateHttpHandler(MxGatewayClientOptions options)
+    private static HttpMessageHandler CreateHttpHandler(MxGatewayClientOptions options) =>
+        CreateHttpHandlerForTests(options);
+
+    /// <summary>Creates an <see cref="HttpMessageHandler"/> configured from the provided options for test use.</summary>
+    /// <param name="options">Client options used to configure TLS and timeouts.</param>
+    /// <returns>The configured HTTP message handler.</returns>
+    internal static SocketsHttpHandler CreateHttpHandlerForTests(MxGatewayClientOptions options)
     {
         SocketsHttpHandler handler = new()
         {
@@ -422,6 +520,11 @@ public sealed class GalaxyRepositoryClient : IAsyncDisposable
                 X509Certificate2 trustedRoot = X509CertificateLoader.LoadCertificateFromFile(options.CaCertificatePath);
                 handler.SslOptions.RemoteCertificateValidationCallback = (_, certificate, chain, errors) =>
                 {
+                    if ((errors & System.Net.Security.SslPolicyErrors.RemoteCertificateNameMismatch) != 0)
+                    {
+                        return false;
+                    }
+
                     if (certificate is null)
                     {
                         return false;
@@ -437,6 +540,10 @@ public sealed class GalaxyRepositoryClient : IAsyncDisposable
                     return customChain.Build(certificateToValidate);
                 };
             }
+            else if (!options.RequireCertificateValidation)
+            {
+                handler.SslOptions.RemoteCertificateValidationCallback = (_, _, _, _) => true;
+            }
         }
 
         return handler;

clients/dotnet/ZB.MOM.WW.MxGateway.Client/GrpcGalaxyRepositoryClientTransport.cs

@@ -10,9 +10,7 @@ internal sealed class GrpcGalaxyRepositoryClientTransport(
     MxGatewayClientOptions options,
     GalaxyRepository.GalaxyRepositoryClient rawClient) : IGalaxyRepositoryClientTransport
 {
-    /// <summary>
-    /// Gets the gateway client options.
-    /// </summary>
+    /// <inheritdoc />
     public MxGatewayClientOptions Options { get; } = options;
 
     /// <summary>
@@ -75,6 +73,27 @@ internal sealed class GrpcGalaxyRepositoryClientTransport(
     }
 
     /// <inheritdoc />
+    public async Task<BrowseChildrenReply> BrowseChildrenAsync(
+        BrowseChildrenRequest request,
+        CallOptions callOptions)
+    {
+        try
+        {
+            return await RawClient.BrowseChildrenAsync(request, callOptions)
+                .ResponseAsync
+                .ConfigureAwait(false);
+        }
+        catch (RpcException exception)
+        {
+            throw MapRpcException(exception, callOptions.CancellationToken);
+        }
+    }
+
+    /// <summary>Streams deploy events from the Galaxy Repository, using an explicit cancellation token that overrides the call options token when provided.</summary>
+    /// <param name="request">The watch deploy events request.</param>
+    /// <param name="callOptions">Call options for the underlying gRPC call.</param>
+    /// <param name="cancellationToken">Optional cancellation token; takes precedence over the token in <paramref name="callOptions"/> when cancellable.</param>
+    /// <returns>An async enumerable of deploy events.</returns>
     public async IAsyncEnumerable<DeployEvent> WatchDeployEventsAsync(
         WatchDeployEventsRequest request,
         CallOptions callOptions,

clients/dotnet/ZB.MOM.WW.MxGateway.Client/GrpcMxGatewayClientTransport.cs

@@ -10,9 +10,7 @@ internal sealed class GrpcMxGatewayClientTransport(
     MxGatewayClientOptions options,
     MxAccessGateway.MxAccessGatewayClient rawClient) : IMxGatewayClientTransport
 {
-    /// <summary>
-    /// Gets the gateway client options.
-    /// </summary>
+    /// <inheritdoc />
     public MxGatewayClientOptions Options { get; } = options;
 
     /// <summary>
@@ -74,7 +72,11 @@ internal sealed class GrpcMxGatewayClientTransport(
         }
     }
 
-    /// <inheritdoc />
+    /// <summary>Streams MXAccess events from the gateway, forwarding an explicit cancellation token to the stream reader.</summary>
+    /// <param name="request">The stream events request.</param>
+    /// <param name="callOptions">gRPC call options.</param>
+    /// <param name="cancellationToken">Token to cancel the streaming enumeration.</param>
+    /// <returns>An async enumerable of MXAccess events.</returns>
     public async IAsyncEnumerable<MxEvent> StreamEventsAsync(
         StreamEventsRequest request,
         CallOptions callOptions,
@@ -133,7 +135,11 @@ internal sealed class GrpcMxGatewayClientTransport(
         }
     }
 
-    /// <inheritdoc />
+    /// <summary>Queries active alarms from the gateway, forwarding an explicit cancellation token to the stream reader.</summary>
+    /// <param name="request">The query active alarms request.</param>
+    /// <param name="callOptions">gRPC call options.</param>
+    /// <param name="cancellationToken">Token to cancel the streaming enumeration.</param>
+    /// <returns>An async enumerable of active alarm snapshots.</returns>
     public async IAsyncEnumerable<ActiveAlarmSnapshot> QueryActiveAlarmsAsync(
         QueryActiveAlarmsRequest request,
         CallOptions callOptions,
@@ -175,7 +181,11 @@ internal sealed class GrpcMxGatewayClientTransport(
         return QueryActiveAlarmsAsync(request, callOptions);
     }
 
-    /// <inheritdoc />
+    /// <summary>Streams alarm feed messages from the gateway, forwarding an explicit cancellation token to the stream reader.</summary>
+    /// <param name="request">The stream alarms request.</param>
+    /// <param name="callOptions">gRPC call options.</param>
+    /// <param name="cancellationToken">Token to cancel the streaming enumeration.</param>
+    /// <returns>An async enumerable of alarm feed messages.</returns>
     public async IAsyncEnumerable<AlarmFeedMessage> StreamAlarmsAsync(
         StreamAlarmsRequest request,
         CallOptions callOptions,

clients/dotnet/ZB.MOM.WW.MxGateway.Client/IGalaxyRepositoryClientTransport.cs

@@ -15,6 +15,7 @@ internal interface IGalaxyRepositoryClientTransport
     /// <summary>Tests the connection to the Galaxy Repository server.</summary>
     /// <param name="request">The test connection request.</param>
     /// <param name="callOptions">gRPC call options (timeout, cancellation, etc.).</param>
+    /// <returns>A task that resolves to the test connection reply.</returns>
     Task<TestConnectionReply> TestConnectionAsync(
         TestConnectionRequest request,
         CallOptions callOptions);
@@ -22,6 +23,7 @@ internal interface IGalaxyRepositoryClientTransport
     /// <summary>Gets the last deploy time from the Galaxy Repository server.</summary>
     /// <param name="request">The get last deploy time request.</param>
     /// <param name="callOptions">gRPC call options (timeout, cancellation, etc.).</param>
+    /// <returns>A task that resolves to the last deploy time reply.</returns>
     Task<GetLastDeployTimeReply> GetLastDeployTimeAsync(
         GetLastDeployTimeRequest request,
         CallOptions callOptions);
@@ -29,13 +31,23 @@ internal interface IGalaxyRepositoryClientTransport
     /// <summary>Discovers the object hierarchy in the Galaxy Repository.</summary>
     /// <param name="request">The discover hierarchy request.</param>
     /// <param name="callOptions">gRPC call options (timeout, cancellation, etc.).</param>
+    /// <returns>A task that resolves to the hierarchy discovery reply.</returns>
     Task<DiscoverHierarchyReply> DiscoverHierarchyAsync(
         DiscoverHierarchyRequest request,
         CallOptions callOptions);
 
+    /// <summary>Returns direct children of a parent in the Galaxy hierarchy.</summary>
+    /// <param name="request">The browse children request.</param>
+    /// <param name="callOptions">gRPC call options (timeout, cancellation, etc.).</param>
+    /// <returns>A task that resolves to the browse children reply.</returns>
+    Task<BrowseChildrenReply> BrowseChildrenAsync(
+        BrowseChildrenRequest request,
+        CallOptions callOptions);
+
     /// <summary>Watches for deployment events from the Galaxy Repository server.</summary>
     /// <param name="request">The watch deploy events request.</param>
     /// <param name="callOptions">gRPC call options (timeout, cancellation, etc.).</param>
+    /// <returns>An async enumerable of deploy events.</returns>
     IAsyncEnumerable<DeployEvent> WatchDeployEventsAsync(
         WatchDeployEventsRequest request,
         CallOptions callOptions);

clients/dotnet/ZB.MOM.WW.MxGateway.Client/LazyBrowseNode.cs

@@ -0,0 +1,107 @@
+using ZB.MOM.WW.MxGateway.Contracts.Proto.Galaxy;
+
+namespace ZB.MOM.WW.MxGateway.Client;
+
+/// <summary>
+///     One node in a lazy-loaded Galaxy browse tree. Holds the underlying
+///     <see cref="GalaxyObject"/> and exposes <see cref="ExpandAsync"/> to fetch
+///     its direct children on demand. Expansion is one-shot: a second call is a
+///     no-op. Pagination of large sibling sets is handled internally.
+/// </summary>
+public sealed class LazyBrowseNode
+{
+    private readonly GalaxyRepositoryClient _client;
+    private readonly BrowseChildrenOptions _options;
+    private readonly List<LazyBrowseNode> _children = [];
+    private readonly SemaphoreSlim _expandLock = new(1, 1);
+    private bool _isExpanded;
+
+    /// <summary>Initializes a new instance of <see cref="LazyBrowseNode"/>.</summary>
+    /// <param name="client">The repository client used to fetch children.</param>
+    /// <param name="object">The underlying Galaxy object for this node.</param>
+    /// <param name="hasChildrenHint">True when the server reports the node has at least one matching descendant.</param>
+    /// <param name="options">Options controlling child browse behavior.</param>
+    internal LazyBrowseNode(
+        GalaxyRepositoryClient client,
+        GalaxyObject @object,
+        bool hasChildrenHint,
+        BrowseChildrenOptions options)
+    {
+        _client = client;
+        Object = @object;
+        HasChildrenHint = hasChildrenHint;
+        _options = options;
+    }
+
+    /// <summary>The underlying Galaxy object for this node.</summary>
+    public GalaxyObject Object { get; }
+
+    /// <summary>True when the server reports this node has at least one matching descendant.</summary>
+    public bool HasChildrenHint { get; }
+
+    /// <summary>Direct children loaded by <see cref="ExpandAsync"/>; empty until then.</summary>
+    public IReadOnlyList<LazyBrowseNode> Children => _children;
+
+    /// <summary>True after the first <see cref="ExpandAsync"/> call completes.</summary>
+    public bool IsExpanded => _isExpanded;
+
+    /// <summary>
+    ///     Fetches direct children from the gateway and populates <see cref="Children"/>.
+    ///     Idempotent: subsequent calls are no-ops.
+    /// </summary>
+    /// <remarks>
+    ///     Thread-safe: concurrent callers see exactly one fetch; subsequent callers
+    ///     (after the first completes) return immediately.
+    /// </remarks>
+    /// <param name="cancellationToken">Token to observe for cancellation.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    public async Task ExpandAsync(CancellationToken cancellationToken = default)
+    {
+        if (_isExpanded)
+        {
+            return;
+        }
+
+        await _expandLock.WaitAsync(cancellationToken).ConfigureAwait(false);
+        try
+        {
+            if (_isExpanded)
+            {
+                return;
+            }
+
+            string pageToken = string.Empty;
+            HashSet<string> seenPageTokens = new(StringComparer.Ordinal);
+            do
+            {
+                BrowseChildrenRequest request = GalaxyRepositoryClient.BuildBrowseChildrenRequest(_options);
+                request.ParentGobjectId = Object.GobjectId;
+                request.PageToken = pageToken;
+
+                BrowseChildrenReply reply = await _client
+                    .BrowseChildrenRawAsync(request, cancellationToken)
+                    .ConfigureAwait(false);
+
+                for (int i = 0; i < reply.Children.Count; i++)
+                {
+                    bool hint = i < reply.ChildHasChildren.Count && reply.ChildHasChildren[i];
+                    _children.Add(new LazyBrowseNode(_client, reply.Children[i], hint, _options));
+                }
+
+                pageToken = reply.NextPageToken;
+                if (!string.IsNullOrWhiteSpace(pageToken) && !seenPageTokens.Add(pageToken))
+                {
+                    throw new MxGatewayException(
+                        $"Galaxy BrowseChildren returned a repeated page token '{pageToken}'.");
+                }
+            }
+            while (!string.IsNullOrWhiteSpace(pageToken));
+
+            _isExpanded = true;
+        }
+        finally
+        {
+            _expandLock.Release();
+        }
+    }
+}

clients/dotnet/ZB.MOM.WW.MxGateway.Client/MxCommandReplyExtensions.cs

@@ -7,6 +7,7 @@ public static class MxCommandReplyExtensions
 {
     /// <summary>Validates that the reply has a successful protocol status (Ok or MxAccessFailure), throwing a gateway exception if not.</summary>
     /// <param name="reply">The command reply to check.</param>
+    /// <returns>The same <paramref name="reply"/> for fluent chaining when validation passes.</returns>
     public static MxCommandReply EnsureProtocolSuccess(this MxCommandReply reply)
     {
         ArgumentNullException.ThrowIfNull(reply);
@@ -24,6 +25,7 @@ public static class MxCommandReplyExtensions
 
     /// <summary>Validates that the reply indicates MXAccess success (no HResult or status failures), throwing MxAccessException if not.</summary>
     /// <param name="reply">The command reply to check.</param>
+    /// <returns>The same <paramref name="reply"/> for fluent chaining when validation passes.</returns>
     public static MxCommandReply EnsureMxAccessSuccess(this MxCommandReply reply)
     {
         ArgumentNullException.ThrowIfNull(reply);

clients/dotnet/ZB.MOM.WW.MxGateway.Client/MxGatewayClient.cs

@@ -249,6 +249,7 @@ public sealed class MxGatewayClient : IAsyncDisposable
     /// <summary>
     /// Disposes the client and releases all resources.
     /// </summary>
+    /// <returns>A task that represents the asynchronous dispose operation.</returns>
     public ValueTask DisposeAsync()
     {
         if (_disposed)
@@ -315,7 +316,13 @@ public sealed class MxGatewayClient : IAsyncDisposable
             .ConfigureAwait(false);
     }
 
-    private static HttpMessageHandler CreateHttpHandler(MxGatewayClientOptions options)
+    private static HttpMessageHandler CreateHttpHandler(MxGatewayClientOptions options) =>
+        CreateHttpHandlerForTests(options);
+
+    /// <summary>Creates an <see cref="HttpMessageHandler"/> configured from the provided options for test use.</summary>
+    /// <param name="options">Client options used to configure TLS and timeouts.</param>
+    /// <returns>The configured HTTP message handler.</returns>
+    internal static SocketsHttpHandler CreateHttpHandlerForTests(MxGatewayClientOptions options)
     {
         SocketsHttpHandler handler = new()
         {
@@ -335,6 +342,11 @@ public sealed class MxGatewayClient : IAsyncDisposable
                 X509Certificate2 trustedRoot = X509CertificateLoader.LoadCertificateFromFile(options.CaCertificatePath);
                 handler.SslOptions.RemoteCertificateValidationCallback = (_, certificate, chain, errors) =>
                 {
+                    if ((errors & System.Net.Security.SslPolicyErrors.RemoteCertificateNameMismatch) != 0)
+                    {
+                        return false;
+                    }
+
                     if (certificate is null)
                     {
                         return false;
@@ -350,6 +362,10 @@ public sealed class MxGatewayClient : IAsyncDisposable
                     return customChain.Build(certificateToValidate);
                 };
             }
+            else if (!options.RequireCertificateValidation)
+            {
+                handler.SslOptions.RemoteCertificateValidationCallback = (_, _, _, _) => true;
+            }
         }
 
         return handler;

clients/dotnet/ZB.MOM.WW.MxGateway.Client/MxGatewayClientContractInfo.cs

@@ -7,9 +7,11 @@ namespace ZB.MOM.WW.MxGateway.Client;
 /// </summary>
 public static class MxGatewayClientContractInfo
 {
+    /// <inheritdoc cref="GatewayContractInfo.GatewayProtocolVersion"/>
     public const uint GatewayProtocolVersion =
         GatewayContractInfo.GatewayProtocolVersion;
 
+    /// <inheritdoc cref="GatewayContractInfo.WorkerProtocolVersion"/>
     public const uint WorkerProtocolVersion =
         GatewayContractInfo.WorkerProtocolVersion;
 }

clients/dotnet/ZB.MOM.WW.MxGateway.Client/MxGatewayClientOptions.cs

@@ -27,6 +27,14 @@ public sealed class MxGatewayClientOptions
     /// </summary>
     public string? CaCertificatePath { get; init; }
 
+    /// <summary>
+    /// When true, TLS connections without a pinned <see cref="CaCertificatePath"/>
+    /// use the OS trust store. When false (default), the gateway certificate is
+    /// accepted without verification — appropriate for this internal tool's
+    /// auto-generated self-signed certificate. Pinning a CA always verifies.
+    /// </summary>
+    public bool RequireCertificateValidation { get; init; }
+
     /// <summary>
     /// Gets the server name override for SNI during TLS handshake.
     /// </summary>
@@ -47,6 +55,9 @@ public sealed class MxGatewayClientOptions
     /// </summary>
     public TimeSpan? StreamTimeout { get; init; }
 
+    /// <summary>
+    /// Gets the maximum size in bytes for gRPC messages.
+    /// </summary>
     public int MaxGrpcMessageBytes { get; init; } = 16 * 1024 * 1024;
 
     /// <summary>

clients/dotnet/ZB.MOM.WW.MxGateway.Client/MxGatewayClientRetryPolicy.cs

@@ -12,6 +12,7 @@ internal static class MxGatewayClientRetryPolicy
     /// <summary>Creates a Polly ResiliencePipeline that retries transient gRPC failures with exponential backoff.</summary>
     /// <param name="options">Retry configuration (max attempts, delay bounds, jitter).</param>
     /// <param name="logger">Optional logger for retry diagnostics.</param>
+    /// <returns>A configured <see cref="ResiliencePipeline"/> with exponential-backoff retry.</returns>
     public static ResiliencePipeline Create(
         MxGatewayClientRetryOptions options,
         ILogger? logger)
@@ -42,6 +43,7 @@ internal static class MxGatewayClientRetryPolicy
 
     /// <summary>Returns whether a command kind is eligible for automatic retry on transient failures.</summary>
     /// <param name="kind">The command kind to check.</param>
+    /// <returns><see langword="true"/> if the command kind is safe to retry; otherwise <see langword="false"/>.</returns>
     public static bool IsRetryableCommand(MxCommandKind kind)
     {
         return kind is MxCommandKind.Ping

clients/dotnet/ZB.MOM.WW.MxGateway.Client/MxGatewaySession.cs

@@ -211,6 +211,7 @@ public sealed class MxGatewaySession : IAsyncDisposable
     /// <param name="serverHandle">The ServerHandle from register.</param>
     /// <param name="itemHandle">The ItemHandle from add-item.</param>
     /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public async Task AdviseAsync(
         int serverHandle,
         int itemHandle,
@@ -252,6 +253,7 @@ public sealed class MxGatewaySession : IAsyncDisposable
     /// <param name="serverHandle">The ServerHandle from register.</param>
     /// <param name="itemHandle">The ItemHandle from add-item.</param>
     /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public async Task UnAdviseAsync(
         int serverHandle,
         int itemHandle,
@@ -293,6 +295,7 @@ public sealed class MxGatewaySession : IAsyncDisposable
     /// <param name="serverHandle">The ServerHandle from register.</param>
     /// <param name="itemHandle">The ItemHandle from add-item.</param>
     /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public async Task RemoveItemAsync(
         int serverHandle,
         int itemHandle,
@@ -675,6 +678,7 @@ public sealed class MxGatewaySession : IAsyncDisposable
     /// <param name="value">The value to write.</param>
     /// <param name="userId">User ID context for the write.</param>
     /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public async Task WriteAsync(
         int serverHandle,
         int itemHandle,
@@ -729,6 +733,7 @@ public sealed class MxGatewaySession : IAsyncDisposable
     /// <param name="timestampValue">The timestamp to write with the value.</param>
     /// <param name="userId">User ID context for the write.</param>
     /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public async Task Write2Async(
         int serverHandle,
         int itemHandle,
@@ -821,6 +826,7 @@ public sealed class MxGatewaySession : IAsyncDisposable
     /// <summary>
     /// Closes the session and releases resources.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public async ValueTask DisposeAsync()
     {
         await CloseAsync().ConfigureAwait(false);

clients/dotnet/ZB.MOM.WW.MxGateway.Client/MxStatusProxyExtensions.cs

@@ -7,6 +7,7 @@ public static class MxStatusProxyExtensions
 {
     /// <summary>Returns whether the status indicates success (success flag set and category is Ok).</summary>
     /// <param name="status">The status to check.</param>
+    /// <returns><c>true</c> if the status is successful; <c>false</c> otherwise.</returns>
     public static bool IsSuccess(this MxStatusProxy status)
     {
         ArgumentNullException.ThrowIfNull(status);
@@ -17,6 +18,7 @@ public static class MxStatusProxyExtensions
 
     /// <summary>Returns a formatted summary of the status for diagnostic output.</summary>
     /// <param name="status">The status to summarize.</param>
+    /// <returns>A human-readable string combining category, source, detail, and diagnostic text.</returns>
     public static string ToDiagnosticSummary(this MxStatusProxy status)
     {
         ArgumentNullException.ThrowIfNull(status);

clients/dotnet/ZB.MOM.WW.MxGateway.Client/MxValueExtensions.cs

@@ -14,6 +14,7 @@ public static class MxValueExtensions
     /// Converts a boolean value to an MxValue with MxDataType.Boolean.
     /// </summary>
     /// <param name="value">Scalar boolean value to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Boolean</c>.</returns>
     public static MxValue ToMxValue(this bool value)
     {
         return new MxValue
@@ -28,6 +29,7 @@ public static class MxValueExtensions
     /// Converts a 32-bit integer value to an MxValue with MxDataType.Integer.
     /// </summary>
     /// <param name="value">32-bit integer value to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Integer</c>.</returns>
     public static MxValue ToMxValue(this int value)
     {
         return new MxValue
@@ -42,6 +44,7 @@ public static class MxValueExtensions
     /// Converts a 64-bit integer value to an MxValue with MxDataType.Integer.
     /// </summary>
     /// <param name="value">64-bit integer value to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Integer</c>.</returns>
     public static MxValue ToMxValue(this long value)
     {
         return new MxValue
@@ -56,6 +59,7 @@ public static class MxValueExtensions
     /// Converts a single-precision floating-point value to an MxValue with MxDataType.Float.
     /// </summary>
     /// <param name="value">Single-precision floating-point value to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Float</c>.</returns>
     public static MxValue ToMxValue(this float value)
     {
         return new MxValue
@@ -70,6 +74,7 @@ public static class MxValueExtensions
     /// Converts a double-precision floating-point value to an MxValue with MxDataType.Double.
     /// </summary>
     /// <param name="value">Double-precision floating-point value to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Double</c>.</returns>
     public static MxValue ToMxValue(this double value)
     {
         return new MxValue
@@ -84,6 +89,7 @@ public static class MxValueExtensions
     /// Converts a string value to an MxValue with MxDataType.String.
     /// </summary>
     /// <param name="value">String value to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.String</c>.</returns>
     public static MxValue ToMxValue(this string value)
     {
         ArgumentNullException.ThrowIfNull(value);
@@ -100,6 +106,7 @@ public static class MxValueExtensions
     /// Converts a DateTimeOffset value to an MxValue with MxDataType.Time.
     /// </summary>
     /// <param name="value">DateTimeOffset value to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Time</c>.</returns>
     public static MxValue ToMxValue(this DateTimeOffset value)
     {
         return new MxValue
@@ -114,6 +121,7 @@ public static class MxValueExtensions
     /// Converts a DateTime value to an MxValue with MxDataType.Time.
     /// </summary>
     /// <param name="value">DateTime value to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Time</c>.</returns>
     public static MxValue ToMxValue(this DateTime value)
     {
         return new DateTimeOffset(
@@ -127,6 +135,7 @@ public static class MxValueExtensions
     /// Converts a boolean array to an MxValue with MxDataType.Boolean.
     /// </summary>
     /// <param name="values">Array of boolean values to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Boolean</c> and an array payload.</returns>
     public static MxValue ToMxValue(this IReadOnlyList<bool> values)
     {
         ArgumentNullException.ThrowIfNull(values);
@@ -145,6 +154,7 @@ public static class MxValueExtensions
     /// Converts a 32-bit integer array to an MxValue with MxDataType.Integer.
     /// </summary>
     /// <param name="values">Array of 32-bit integer values to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Integer</c> and an array payload.</returns>
     public static MxValue ToMxValue(this IReadOnlyList<int> values)
     {
         ArgumentNullException.ThrowIfNull(values);
@@ -163,6 +173,7 @@ public static class MxValueExtensions
     /// Converts a 64-bit integer array to an MxValue with MxDataType.Integer.
     /// </summary>
     /// <param name="values">Array of 64-bit integer values to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Integer</c> and an array payload.</returns>
     public static MxValue ToMxValue(this IReadOnlyList<long> values)
     {
         ArgumentNullException.ThrowIfNull(values);
@@ -181,6 +192,7 @@ public static class MxValueExtensions
     /// Converts a single-precision floating-point array to an MxValue with MxDataType.Float.
     /// </summary>
     /// <param name="values">Array of single-precision floating-point values to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Float</c> and an array payload.</returns>
     public static MxValue ToMxValue(this IReadOnlyList<float> values)
     {
         ArgumentNullException.ThrowIfNull(values);
@@ -199,6 +211,7 @@ public static class MxValueExtensions
     /// Converts a double-precision floating-point array to an MxValue with MxDataType.Double.
     /// </summary>
     /// <param name="values">Array of double-precision floating-point values to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Double</c> and an array payload.</returns>
     public static MxValue ToMxValue(this IReadOnlyList<double> values)
     {
         ArgumentNullException.ThrowIfNull(values);
@@ -217,6 +230,7 @@ public static class MxValueExtensions
     /// Converts a string array to an MxValue with MxDataType.String.
     /// </summary>
     /// <param name="values">Array of string values to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.String</c> and an array payload.</returns>
     public static MxValue ToMxValue(this IReadOnlyList<string> values)
     {
         ArgumentNullException.ThrowIfNull(values);
@@ -235,6 +249,7 @@ public static class MxValueExtensions
     /// Converts a DateTimeOffset array to an MxValue with MxDataType.Time.
     /// </summary>
     /// <param name="values">Array of DateTimeOffset values to wrap.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Time</c> and an array payload.</returns>
     public static MxValue ToMxValue(this IReadOnlyList<DateTimeOffset> values)
     {
         ArgumentNullException.ThrowIfNull(values);
@@ -253,6 +268,7 @@ public static class MxValueExtensions
     /// Gets the projection kind (field name) of the given MxValue's current oneof value.
     /// </summary>
     /// <param name="value">The MxValue whose oneof projection kind is returned.</param>
+    /// <returns>The JSON field name of the active oneof case, or <c>"nullValue"</c>/<c>"unspecified"</c> for null/unset values.</returns>
     public static string GetProjectionKind(this MxValue value)
     {
         ArgumentNullException.ThrowIfNull(value);
@@ -276,6 +292,7 @@ public static class MxValueExtensions
     /// Converts an MxValue to a CLR object; returns the boxed value or null for null MxValues.
     /// </summary>
     /// <param name="value">The MxValue to convert.</param>
+    /// <returns>The boxed CLR value, or null if the MxValue represents a null.</returns>
     public static object? ToClrValue(this MxValue value)
     {
         ArgumentNullException.ThrowIfNull(value);
@@ -299,6 +316,7 @@ public static class MxValueExtensions
     /// Converts an MxArray to a CLR array; returns null if the array does not have a known element type.
     /// </summary>
     /// <param name="array">The MxArray to convert.</param>
+    /// <returns>A CLR array of the appropriate element type, or null for unknown element types.</returns>
     public static object? ToClrArrayValue(this MxArray array)
     {
         ArgumentNullException.ThrowIfNull(array);
@@ -328,6 +346,7 @@ public static class MxValueExtensions
     /// <param name="variantType">Variant type string (e.g., "VT_BSTR").</param>
     /// <param name="rawDiagnostic">Diagnostic string describing the raw value.</param>
     /// <param name="rawDataType">Optional MXAccess data type override.</param>
+    /// <returns>An <see cref="MxValue"/> with <c>MxDataType.Unknown</c> and the raw byte payload.</returns>
     public static MxValue ToRawMxValue(
         byte[] value,
         string variantType,

clients/dotnet/ZB.MOM.WW.MxGateway.Client/ZB.MOM.WW.MxGateway.Client.csproj

@@ -16,4 +16,21 @@
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
+  <PropertyGroup>
+    <IsPackable>true</IsPackable>
+    <PackageId>ZB.MOM.WW.MxGateway.Client</PackageId>
+    <Description>.NET 10 gRPC client for the MxAccessGateway service. Provides typed wrappers, retry, and a lazy-browse walker over the Galaxy Repository hierarchy.</Description>
+    <PackageReadmeFile>README.md</PackageReadmeFile>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Include="..\README.md" Pack="true" PackagePath="\" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleTo">
+      <_Parameter1>ZB.MOM.WW.MxGateway.Client.Tests</_Parameter1>
+    </AssemblyAttribute>
+  </ItemGroup>
+
 </Project>

clients/go/GoClientDesign.md

@@ -104,6 +104,23 @@ Support:
 - `credentials.NewClientTLSFromFile`,
 - custom `tls.Config` for advanced callers.
 
+### Trust posture
+
+The gateway can serve a self-signed certificate it generates itself (it has no
+PKI). To make that usable, TLS is **lenient by default**: when `Plaintext` is
+`false` and no `CACertFile`/`TLSConfig`/`TransportCredentials` is supplied,
+`buildCredentials` dials with `tls.Config{InsecureSkipVerify: true}` (carrying
+`ServerNameOverride` as the SNI when set), so the gateway's self-signed
+certificate is accepted without verification.
+
+To verify the gateway instead:
+
+- set `CACertFile` to pin a CA (full verification against that root), or
+- set `RequireCertificateValidation: true` to verify against the OS/system trust
+  roots without pinning.
+
+Pinning a CA always wins over the lenient default.
+
 ## Streaming
 
 `Events(ctx)` should return a receive channel of:

clients/go/README.md

@@ -75,6 +75,14 @@ client, err := mxgateway.Dial(ctx, mxgateway.Options{
 })
 ```
 
+The gateway can auto-generate its own self-signed certificate (it has no PKI), so
+the client is **lenient by default**: a TLS connection (`Plaintext: false`) with
+no `CACertFile`/`TLSConfig` accepts whatever certificate the gateway presents
+(`InsecureSkipVerify`, with `ServerNameOverride` as the SNI when set). To verify
+instead, set `CACertFile` to pin a CA, or set `RequireCertificateValidation:
+true` to verify against the OS/system trust roots without pinning. See
+[Gateway Configuration](../../docs/GatewayConfiguration.md#automatic-self-signed-certificate).
+
 `Client.OpenSession` returns a `Session` with helpers for `Register`,
 `AddItem`, `AddItem2`, `Advise`, `Write`, `Events`, and `Close`. Prefer
 `SubscribeEvents` or `SubscribeEventsAfter` for long-running streams because the
@@ -121,6 +129,68 @@ reports `present=false` (no deploy recorded). `DiscoverHierarchy` returns
 the generated `*GalaxyObject` slice with each object's dynamic attributes
 populated for direct contract access.
 
+### Browsing lazily
+
+For UI trees or OPC UA bridges, use `BrowseChildren` to walk one level at a
+time instead of loading the full hierarchy. Pass an empty request for root
+objects; subsequent calls set `ParentGobjectId`, `ParentTagName`, or
+`ParentContainedPath`. Filter fields match `DiscoverHierarchy`. Each response
+pairs `Children` with `ChildHasChildren` so you know which nodes to expand. See
+[Galaxy Repository](../../docs/GalaxyRepository.md#browsechildren) for full
+request and filter semantics.
+
+```go
+import pb "gitea.dohertylan.com/dohertj2/mxaccessgw/clients/go/internal/generated/galaxy_repository/v1"
+
+reply, err := galaxy.BrowseChildren(ctx, &pb.BrowseChildrenRequest{})
+if err != nil {
+    return err
+}
+for i, child := range reply.GetChildren() {
+    fmt.Printf("%s expand=%v\n", child.GetTagName(), reply.GetChildHasChildren()[i])
+}
+```
+
+#### High-level walker
+
+For UI trees, the client provides a `LazyBrowseNode` walker that handles
+sibling pagination and the `child_has_children` hint for you:
+
+```go
+galaxy, err := mxgateway.DialGalaxy(ctx, mxgateway.Options{
+    Endpoint:  "localhost:5000",
+    APIKey:    os.Getenv("MXGATEWAY_API_KEY"),
+    Plaintext: true,
+})
+if err != nil {
+    log.Fatal(err)
+}
+defer galaxy.Close()
+
+roots, err := galaxy.Browse(ctx, nil)
+if err != nil {
+    log.Fatal(err)
+}
+for _, root := range roots {
+    if root.HasChildrenHint() {
+        if err := root.Expand(ctx); err != nil {
+            log.Fatal(err)
+        }
+    }
+    for _, child := range root.Children() {
+        kind := "leaf"
+        if child.HasChildrenHint() {
+            kind = "has children"
+        }
+        fmt.Printf("%s (%s)\n", child.Object().GetTagName(), kind)
+    }
+}
+```
+
+`Expand` is idempotent — calling it twice fires only one RPC,
+and is safe under concurrent callers. To refresh after a Galaxy redeploy, call
+`Browse` again from the root.
+
 ### Watching deploy events
 
 `WatchDeployEvents` opens a server-streaming subscription. The server emits a
@@ -213,6 +283,38 @@ $env:MXGATEWAY_TEST_ITEM = 'Area001.Tag.Value'
 go run ./cmd/mxgw-go smoke -endpoint $env:MXGATEWAY_ENDPOINT -plaintext -api-key-env MXGATEWAY_API_KEY -item $env:MXGATEWAY_TEST_ITEM -json
 ```
 
+## Installing the Go client
+
+The module is resolved directly from the git repo — no package registry:
+
+````bash
+go get gitea.dohertylan.com/dohertj2/mxaccessgw/clients/go@v0.1.0
+````
+
+Then import:
+
+````go
+import "gitea.dohertylan.com/dohertj2/mxaccessgw/clients/go/mxgateway"
+````
+
+If your build environment cannot reach `gitea.dohertylan.com` directly,
+configure `GOPROXY` to point at an internal proxy that fronts the Gitea
+repo, or use `GONOSUMCHECK` + `GOPRIVATE` to bypass the checksum database
+for the internal module path.
+
+## Releasing a new version
+
+Go modules in monorepo subdirectories use prefixed tags. To tag a release
+from this repo:
+
+````bash
+pwsh scripts/tag-go-module.ps1 -Version v0.1.1 -Push
+````
+
+The script validates semver, refuses to tag with uncommitted tracked
+changes, creates an annotated tag `clients/go/v0.1.1`, and (with `-Push`)
+pushes it to origin.
+
 ## Related Documentation
 
 - [Client Packaging](../../docs/ClientPackaging.md)

clients/go/cmd/mxgw-go/main.go

@@ -396,25 +396,31 @@ func runReadBulk(ctx context.Context, args []string, stdout, stderr io.Writer) e
 }
 
 func runWriteBulk(ctx context.Context, args []string, stdout, stderr io.Writer) error {
-	return runWriteBulkVariant(ctx, args, stdout, stderr, "write-bulk", false, false)
+	return runWriteBulkVariant(ctx, args, stdout, stderr, "write-bulk", false)
 }
 
 func runWrite2Bulk(ctx context.Context, args []string, stdout, stderr io.Writer) error {
-	return runWriteBulkVariant(ctx, args, stdout, stderr, "write2-bulk", true, false)
+	return runWriteBulkVariant(ctx, args, stdout, stderr, "write2-bulk", true)
 }
 
 func runWriteSecuredBulk(ctx context.Context, args []string, stdout, stderr io.Writer) error {
-	return runWriteBulkVariant(ctx, args, stdout, stderr, "write-secured-bulk", false, true)
+	return runWriteBulkVariant(ctx, args, stdout, stderr, "write-secured-bulk", false)
 }
 
 func runWriteSecured2Bulk(ctx context.Context, args []string, stdout, stderr io.Writer) error {
-	return runWriteBulkVariant(ctx, args, stdout, stderr, "write-secured2-bulk", true, true)
+	return runWriteBulkVariant(ctx, args, stdout, stderr, "write-secured2-bulk", true)
 }
 
 // runWriteBulkVariant shares the flag-parsing + entry-build skeleton across
-// the four bulk-write families. withTimestamp adds a --timestamp-value flag;
-// secured switches from --user-id to --current-user-id / --verifier-user-id.
-func runWriteBulkVariant(ctx context.Context, args []string, stdout, stderr io.Writer, command string, withTimestamp bool, secured bool) error {
+// the four bulk-write families. The variant is derived from command alone;
+// withTimestamp adds a --timestamp-value flag. To keep wrong-variant flags
+// from silently no-op'ing, secured-only flags (-current-user-id /
+// -verifier-user-id) are only registered for the secured variants, and
+// -user-id only for the non-secured Write/Write2 variants — a wrong-variant
+// flag then surfaces as a clean "flag provided but not defined" error.
+func runWriteBulkVariant(ctx context.Context, args []string, stdout, stderr io.Writer, command string, withTimestamp bool) error {
+	secured := command == "write-secured-bulk" || command == "write-secured2-bulk"
+
 	flags := flag.NewFlagSet(command, flag.ContinueOnError)
 	flags.SetOutput(stderr)
 	common := bindCommonFlags(flags)
@@ -424,9 +430,17 @@ func runWriteBulkVariant(ctx context.Context, args []string, stdout, stderr io.W
 	itemHandles := flags.String("item-handles", "", "comma-separated item handles")
 	valueType := flags.String("type", "string", "value type: bool, int32, int64, float, double, string")
 	values := flags.String("values", "", "comma-separated values (one per item handle)")
-	userID := flags.Int("user-id", 0, "MXAccess user id (Write/Write2 variants)")
-	currentUserID := flags.Int("current-user-id", 0, "MXAccess current user id (Secured variants)")
-	verifierUserID := flags.Int("verifier-user-id", 0, "MXAccess verifier user id (Secured variants)")
+	var (
+		userID         *int
+		currentUserID  *int
+		verifierUserID *int
+	)
+	if secured {
+		currentUserID = flags.Int("current-user-id", 0, "MXAccess current user id (Secured variants)")
+		verifierUserID = flags.Int("verifier-user-id", 0, "MXAccess verifier user id (Secured variants)")
+	} else {
+		userID = flags.Int("user-id", 0, "MXAccess user id (Write/Write2 variants)")
+	}
 	timestampValue := flags.String("timestamp-value", "", "RFC 3339 timestamp shared across all entries (Write2/WriteSecured2 variants)")
 
 	if err := flags.Parse(args); err != nil {
@@ -514,7 +528,6 @@ func runWriteBulkVariant(ctx context.Context, args []string, stdout, stderr io.W
 	default:
 		return fmt.Errorf("unsupported bulk write command %q", command)
 	}
-	_ = secured // currently only used for routing above; reserved for future per-variant validation
 	return writeWriteBulkOutput(stdout, *jsonOutput, command, options, results, err)
 }
 
@@ -598,10 +611,12 @@ func runBenchReadBulk(ctx context.Context, args []string, stdout, stderr io.Writ
 	}()
 
 	// Warm-up: drive identical calls so any first-call JIT / connection-pool
-	// setup is amortised before the measurement window opens.
+	// setup is amortised before the measurement window opens. The ctx.Err()
+	// guard short-circuits on Ctrl+C / parent-cancel instead of spinning
+	// failing ReadBulk calls until the wall-clock deadline elapses.
 	warmupDeadline := time.Now().Add(time.Duration(*warmupSeconds) * time.Second)
 	timeout := time.Duration(*timeoutMs) * time.Millisecond
-	for time.Now().Before(warmupDeadline) {
+	for time.Now().Before(warmupDeadline) && ctx.Err() == nil {
 		_, _ = session.ReadBulk(ctx, serverHandle, tags, timeout)
 	}
 
@@ -613,7 +628,7 @@ func runBenchReadBulk(ctx context.Context, args []string, stdout, stderr io.Writ
 	steadyStart := time.Now()
 	steadyDeadline := steadyStart.Add(time.Duration(*durationSeconds) * time.Second)
 
-	for time.Now().Before(steadyDeadline) {
+	for time.Now().Before(steadyDeadline) && ctx.Err() == nil {
 		callStart := time.Now()
 		results, err := session.ReadBulk(ctx, serverHandle, tags, timeout)
 		elapsed := time.Since(callStart)
@@ -1191,18 +1206,28 @@ const batchEOR = "__MXGW_BATCH_EOR__"
 // runBatch reads one command line at a time from in, dispatches each via the
 // normal runWithIO routing, and writes a batchEOR sentinel to stdout after
 // every result. Errors are serialised as JSON to stdout (not stderr) so the
-// harness can parse them without interleaving stderr. The loop never terminates
-// on command error; only stdin EOF (or an empty line) ends the session.
+// harness can parse them without interleaving stderr. Blank lines are
+// skipped; only stdin EOF ends the session.
+//
+// The scanner buffer is widened to 16 MiB so a single long command line
+// (e.g. a bulk-write with several thousand handles) does not trip the
+// default 64 KiB bufio.Scanner token-too-long error and abort the session.
+// If a line still exceeds the cap, the error is surfaced as a per-command
+// error-with-sentinel and the session continues.
 func runBatch(ctx context.Context, in io.Reader, stdout, stderr io.Writer) error {
 	bw := bufio.NewWriter(stdout)
 	scanner := bufio.NewScanner(in)
-	for scanner.Scan() {
-		line := scanner.Text()
-		if line == "" {
+	scanner.Buffer(make([]byte, 0, 64*1024), 16*1024*1024)
+	for {
+		if !scanner.Scan() {
 			break
 		}
+		line := scanner.Text()
 		args := strings.Fields(line)
 		if len(args) == 0 {
+			// Skip blank / whitespace-only lines; do NOT terminate. The
+			// session ends only on stdin EOF so a stray blank line in a
+			// PowerShell here-string does not silently drop later commands.
 			continue
 		}
 		if err := runWithIO(ctx, args, bw, stderr); err != nil {
@@ -1217,7 +1242,21 @@ func runBatch(ctx context.Context, in io.Reader, stdout, stderr io.Writer) error
 		_, _ = fmt.Fprintln(bw, batchEOR)
 		_ = bw.Flush()
 	}
-	return scanner.Err()
+	if err := scanner.Err(); err != nil {
+		// Emit the scanner failure as a final error-with-sentinel so the
+		// harness sees the failure framed, then return the error so the
+		// process exit reflects it. This handles bufio.ErrTooLong for any
+		// pathological line above the 16 MiB cap.
+		errPayload := map[string]string{
+			"error": err.Error(),
+			"type":  "error",
+		}
+		_ = writeJSON(bw, errPayload)
+		_, _ = fmt.Fprintln(bw, batchEOR)
+		_ = bw.Flush()
+		return err
+	}
+	return nil
 }
 
 func dialGalaxyForCommand(ctx context.Context, common *commonOptions) (*mxgateway.GalaxyClient, commonOptions, error) {

clients/go/cmd/mxgw-go/main_test.go

@@ -2,9 +2,15 @@ package main
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
+	"net"
 	"strings"
 	"testing"
+	"time"
+
+	pb "gitea.dohertylan.com/dohertj2/mxaccessgw/clients/go/internal/generated"
+	"google.golang.org/grpc"
 )
 
 func TestRunVersionJSON(t *testing.T) {
@@ -84,3 +90,207 @@ func TestParseValueBuildsTypedValue(t *testing.T) {
 		t.Fatalf("int32 value = %d, want 123", got)
 	}
 }
+
+// TestRunWriteBulkVariantGatesSecuredFlags pins the Client.Go-022 fix:
+// secured-only flags must be unavailable on non-secured variants, and
+// vice-versa, so a wrong-variant flag fails with a clean "flag provided
+// but not defined" error instead of silently no-op'ing.
+func TestRunWriteBulkVariantGatesSecuredFlags(t *testing.T) {
+	cases := []struct {
+		name string
+		args []string
+	}{
+		{
+			name: "write-bulk-rejects-current-user-id",
+			args: []string{"write-bulk", "-current-user-id", "5", "-item-handles", "1", "-values", "1"},
+		},
+		{
+			name: "write-bulk-rejects-verifier-user-id",
+			args: []string{"write-bulk", "-verifier-user-id", "5", "-item-handles", "1", "-values", "1"},
+		},
+		{
+			name: "write2-bulk-rejects-current-user-id",
+			args: []string{"write2-bulk", "-current-user-id", "5", "-item-handles", "1", "-values", "1"},
+		},
+		{
+			name: "write-secured-bulk-rejects-user-id",
+			args: []string{"write-secured-bulk", "-user-id", "5", "-item-handles", "1", "-values", "1"},
+		},
+		{
+			name: "write-secured2-bulk-rejects-user-id",
+			args: []string{"write-secured2-bulk", "-user-id", "5", "-item-handles", "1", "-values", "1"},
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			var stdout, stderr bytes.Buffer
+			err := runWithIO(t.Context(), tc.args, &stdout, &stderr)
+			if err == nil {
+				t.Fatalf("runWithIO(%v) returned no error", tc.args)
+			}
+			if !strings.Contains(err.Error(), "flag provided but not defined") {
+				t.Fatalf("runWithIO(%v) error = %v; want 'flag provided but not defined'", tc.args, err)
+			}
+		})
+	}
+}
+
+// TestRunBenchReadBulkRespectsContextCancellation pins the Client.Go-023
+// fix: the warm-up and steady-state wall-clock loops must honour ctx.Err()
+// so an external cancel (Ctrl+C, parent-cancel from a cross-language bench
+// driver) short-circuits the bench instead of spinning failing ReadBulk
+// calls until the wall-clock deadline elapses.
+func TestRunBenchReadBulkRespectsContextCancellation(t *testing.T) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	server := grpc.NewServer()
+	fake := &benchFakeGateway{}
+	pb.RegisterMxAccessGatewayServer(server, fake)
+	go func() {
+		_ = server.Serve(listener)
+	}()
+	defer server.Stop()
+	defer listener.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	// Long warm-up + duration, so if the ctx.Err() guard were missing the
+	// loops would run for ~10s. With the guard, the cancel below short-
+	// circuits both loops within ~one ReadBulk iteration.
+	args := []string{
+		"bench-read-bulk",
+		"-endpoint", listener.Addr().String(),
+		"-plaintext",
+		"-api-key", "test",
+		"-warmup-seconds", "5",
+		"-duration-seconds", "5",
+		"-bulk-size", "1",
+		"-timeout-ms", "100",
+	}
+
+	// Cancel after a brief delay — far less than warmup+duration (10s).
+	go func() {
+		time.Sleep(150 * time.Millisecond)
+		cancel()
+	}()
+
+	var stdout, stderr bytes.Buffer
+	start := time.Now()
+	err = runWithIO(ctx, args, &stdout, &stderr)
+	elapsed := time.Since(start)
+
+	// With the ctx.Err() guard, the loops exit well before the wall-clock
+	// deadlines (warmup=5s + duration=5s = 10s). Allow generous slack for
+	// CI noise but assert clearly less than the un-guarded worst case.
+	if elapsed > 4*time.Second {
+		t.Fatalf("bench-read-bulk took %s after ctx cancel; want <4s (ctx.Err() guard missing?). err=%v stderr=%s", elapsed, err, stderr.String())
+	}
+}
+
+// benchFakeGateway is a minimal MxAccessGatewayServer that satisfies the
+// bench-read-bulk session-setup sequence (OpenSession + Invoke for Register
+// / SubscribeBulk / ReadBulk / UnsubscribeBulk / CloseSession).
+type benchFakeGateway struct {
+	pb.UnimplementedMxAccessGatewayServer
+}
+
+func (g *benchFakeGateway) OpenSession(_ context.Context, _ *pb.OpenSessionRequest) (*pb.OpenSessionReply, error) {
+	return &pb.OpenSessionReply{
+		SessionId:      "bench-session",
+		ProtocolStatus: &pb.ProtocolStatus{Code: pb.ProtocolStatusCode_PROTOCOL_STATUS_CODE_OK},
+	}, nil
+}
+
+func (g *benchFakeGateway) CloseSession(_ context.Context, req *pb.CloseSessionRequest) (*pb.CloseSessionReply, error) {
+	return &pb.CloseSessionReply{
+		SessionId:      req.GetSessionId(),
+		ProtocolStatus: &pb.ProtocolStatus{Code: pb.ProtocolStatusCode_PROTOCOL_STATUS_CODE_OK},
+	}, nil
+}
+
+func (g *benchFakeGateway) Invoke(_ context.Context, req *pb.MxCommandRequest) (*pb.MxCommandReply, error) {
+	kind := req.GetCommand().GetKind()
+	reply := &pb.MxCommandReply{
+		SessionId:      req.GetSessionId(),
+		Kind:           kind,
+		ProtocolStatus: &pb.ProtocolStatus{Code: pb.ProtocolStatusCode_PROTOCOL_STATUS_CODE_OK},
+	}
+	switch kind {
+	case pb.MxCommandKind_MX_COMMAND_KIND_REGISTER:
+		reply.Payload = &pb.MxCommandReply_Register{Register: &pb.RegisterReply{ServerHandle: 1}}
+	case pb.MxCommandKind_MX_COMMAND_KIND_SUBSCRIBE_BULK:
+		reply.Payload = &pb.MxCommandReply_SubscribeBulk{SubscribeBulk: &pb.BulkSubscribeReply{
+			Results: []*pb.SubscribeResult{{ServerHandle: 1, ItemHandle: 1, WasSuccessful: true}},
+		}}
+	case pb.MxCommandKind_MX_COMMAND_KIND_READ_BULK:
+		reply.Payload = &pb.MxCommandReply_ReadBulk{ReadBulk: &pb.BulkReadReply{
+			Results: []*pb.BulkReadResult{{ItemHandle: 1, WasSuccessful: true, WasCached: true}},
+		}}
+	case pb.MxCommandKind_MX_COMMAND_KIND_UNSUBSCRIBE_BULK:
+		reply.Payload = &pb.MxCommandReply_UnsubscribeBulk{UnsubscribeBulk: &pb.BulkSubscribeReply{}}
+	}
+	return reply, nil
+}
+
+// TestRunBenchReadBulkRejectsNonPositiveBulkSize pins the Client.Go-023-adjacent
+// positivity checks so they cannot drift while resolving the cancellation finding.
+func TestRunBenchReadBulkRejectsNonPositiveBulkSize(t *testing.T) {
+	var stdout, stderr bytes.Buffer
+	err := runWithIO(t.Context(), []string{"bench-read-bulk", "-bulk-size", "0"}, &stdout, &stderr)
+	if err == nil || !strings.Contains(err.Error(), "bulk-size must be positive") {
+		t.Fatalf("bench-read-bulk -bulk-size 0 error = %v", err)
+	}
+}
+
+// TestRunBatchSkipsBlankLinesAndContinuesUntilEOF pins the Client.Go-027 fix:
+// a blank line in the middle of a batch session must NOT terminate the loop —
+// only stdin EOF ends the session.
+func TestRunBatchSkipsBlankLinesAndContinuesUntilEOF(t *testing.T) {
+	var stdout, stderr bytes.Buffer
+
+	// version -> blank -> version (a stray blank line in the middle of a
+	// programmatic session).
+	in := strings.NewReader("version --json\n\nversion --json\n")
+	if err := runBatch(t.Context(), in, &stdout, &stderr); err != nil {
+		t.Fatalf("runBatch() error = %v; stderr = %s", err, stderr.String())
+	}
+
+	out := stdout.String()
+	// Both version commands must have produced a result before the EOR sentinel.
+	if count := strings.Count(out, batchEOR); count != 2 {
+		t.Fatalf("EOR sentinel count = %d, want 2 (one per command, blank line skipped); out = %q", count, out)
+	}
+}
+
+// TestRunBatchHandlesLongCommandLine pins the Client.Go-026 fix: a command
+// line longer than the default bufio.Scanner token size (64 KiB) must not
+// abort the batch session.
+func TestRunBatchHandlesLongCommandLine(t *testing.T) {
+	var stdout, stderr bytes.Buffer
+
+	// Build a single command line larger than 64 KiB. The command itself is
+	// invalid (no real session) but runBatch must still emit an EOR sentinel
+	// and continue to the next command rather than dropping the line on the
+	// floor with a bufio.ErrTooLong from the outer return.
+	huge := strings.Repeat("tag-with-a-reasonably-long-name-and-suffix,", 2000) + "trailing"
+	line := "subscribe-bulk -session-id none -items " + huge
+	if len(line) <= 64*1024 {
+		t.Fatalf("test setup error: long line length = %d, want > 64KiB", len(line))
+	}
+	in := strings.NewReader(line + "\nversion --json\n")
+
+	if err := runBatch(t.Context(), in, &stdout, &stderr); err != nil {
+		t.Fatalf("runBatch() error = %v; stderr = %s", err, stderr.String())
+	}
+
+	out := stdout.String()
+	// Both commands must produce an EOR sentinel — the long line should be a
+	// per-command error (still emitted with EOR), then the version command
+	// should run normally.
+	if count := strings.Count(out, batchEOR); count != 2 {
+		t.Fatalf("EOR sentinel count = %d, want 2 (one per command, even when first is too long); out length = %d", count, len(out))
+	}
+}

clients/go/internal/generated/galaxy_repository.pb.go

@@ -824,6 +824,260 @@ func (x *GalaxyAttribute) GetIsAlarm() bool {
 	return false
 }
 
+type BrowseChildrenRequest struct {
+	state protoimpl.MessageState `protogen:"open.v1"`
+	// Parent selector. Empty oneof returns root objects (parent_gobject_id == 0).
+	//
+	// Types that are valid to be assigned to Parent:
+	//
+	//	*BrowseChildrenRequest_ParentGobjectId
+	//	*BrowseChildrenRequest_ParentTagName
+	//	*BrowseChildrenRequest_ParentContainedPath
+	Parent isBrowseChildrenRequest_Parent `protobuf_oneof:"parent"`
+	// Maximum number of direct children to return. Server default 500; cap 5000.
+	PageSize int32 `protobuf:"varint,4,opt,name=page_size,json=pageSize,proto3" json:"page_size,omitempty"`
+	// Opaque token returned by a previous BrowseChildren response. Bound to the
+	// cache sequence, parent selector, and the filter set; a mismatch returns
+	// InvalidArgument.
+	PageToken string `protobuf:"bytes,5,opt,name=page_token,json=pageToken,proto3" json:"page_token,omitempty"`
+	// --- Filter parity with DiscoverHierarchy. AND-combined. ---
+	CategoryIds           []int32  `protobuf:"varint,6,rep,packed,name=category_ids,json=categoryIds,proto3" json:"category_ids,omitempty"`
+	TemplateChainContains []string `protobuf:"bytes,7,rep,name=template_chain_contains,json=templateChainContains,proto3" json:"template_chain_contains,omitempty"`
+	TagNameGlob           string   `protobuf:"bytes,8,opt,name=tag_name_glob,json=tagNameGlob,proto3" json:"tag_name_glob,omitempty"`
+	IncludeAttributes     *bool    `protobuf:"varint,9,opt,name=include_attributes,json=includeAttributes,proto3,oneof" json:"include_attributes,omitempty"`
+	AlarmBearingOnly      bool     `protobuf:"varint,10,opt,name=alarm_bearing_only,json=alarmBearingOnly,proto3" json:"alarm_bearing_only,omitempty"`
+	HistorizedOnly        bool     `protobuf:"varint,11,opt,name=historized_only,json=historizedOnly,proto3" json:"historized_only,omitempty"`
+	unknownFields         protoimpl.UnknownFields
+	sizeCache             protoimpl.SizeCache
+}
+
+func (x *BrowseChildrenRequest) Reset() {
+	*x = BrowseChildrenRequest{}
+	mi := &file_galaxy_repository_proto_msgTypes[10]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *BrowseChildrenRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*BrowseChildrenRequest) ProtoMessage() {}
+
+func (x *BrowseChildrenRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_galaxy_repository_proto_msgTypes[10]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use BrowseChildrenRequest.ProtoReflect.Descriptor instead.
+func (*BrowseChildrenRequest) Descriptor() ([]byte, []int) {
+	return file_galaxy_repository_proto_rawDescGZIP(), []int{10}
+}
+
+func (x *BrowseChildrenRequest) GetParent() isBrowseChildrenRequest_Parent {
+	if x != nil {
+		return x.Parent
+	}
+	return nil
+}
+
+func (x *BrowseChildrenRequest) GetParentGobjectId() int32 {
+	if x != nil {
+		if x, ok := x.Parent.(*BrowseChildrenRequest_ParentGobjectId); ok {
+			return x.ParentGobjectId
+		}
+	}
+	return 0
+}
+
+func (x *BrowseChildrenRequest) GetParentTagName() string {
+	if x != nil {
+		if x, ok := x.Parent.(*BrowseChildrenRequest_ParentTagName); ok {
+			return x.ParentTagName
+		}
+	}
+	return ""
+}
+
+func (x *BrowseChildrenRequest) GetParentContainedPath() string {
+	if x != nil {
+		if x, ok := x.Parent.(*BrowseChildrenRequest_ParentContainedPath); ok {
+			return x.ParentContainedPath
+		}
+	}
+	return ""
+}
+
+func (x *BrowseChildrenRequest) GetPageSize() int32 {
+	if x != nil {
+		return x.PageSize
+	}
+	return 0
+}
+
+func (x *BrowseChildrenRequest) GetPageToken() string {
+	if x != nil {
+		return x.PageToken
+	}
+	return ""
+}
+
+func (x *BrowseChildrenRequest) GetCategoryIds() []int32 {
+	if x != nil {
+		return x.CategoryIds
+	}
+	return nil
+}
+
+func (x *BrowseChildrenRequest) GetTemplateChainContains() []string {
+	if x != nil {
+		return x.TemplateChainContains
+	}
+	return nil
+}
+
+func (x *BrowseChildrenRequest) GetTagNameGlob() string {
+	if x != nil {
+		return x.TagNameGlob
+	}
+	return ""
+}
+
+func (x *BrowseChildrenRequest) GetIncludeAttributes() bool {
+	if x != nil && x.IncludeAttributes != nil {
+		return *x.IncludeAttributes
+	}
+	return false
+}
+
+func (x *BrowseChildrenRequest) GetAlarmBearingOnly() bool {
+	if x != nil {
+		return x.AlarmBearingOnly
+	}
+	return false
+}
+
+func (x *BrowseChildrenRequest) GetHistorizedOnly() bool {
+	if x != nil {
+		return x.HistorizedOnly
+	}
+	return false
+}
+
+type isBrowseChildrenRequest_Parent interface {
+	isBrowseChildrenRequest_Parent()
+}
+
+type BrowseChildrenRequest_ParentGobjectId struct {
+	ParentGobjectId int32 `protobuf:"varint,1,opt,name=parent_gobject_id,json=parentGobjectId,proto3,oneof"`
+}
+
+type BrowseChildrenRequest_ParentTagName struct {
+	ParentTagName string `protobuf:"bytes,2,opt,name=parent_tag_name,json=parentTagName,proto3,oneof"`
+}
+
+type BrowseChildrenRequest_ParentContainedPath struct {
+	ParentContainedPath string `protobuf:"bytes,3,opt,name=parent_contained_path,json=parentContainedPath,proto3,oneof"`
+}
+
+func (*BrowseChildrenRequest_ParentGobjectId) isBrowseChildrenRequest_Parent() {}
+
+func (*BrowseChildrenRequest_ParentTagName) isBrowseChildrenRequest_Parent() {}
+
+func (*BrowseChildrenRequest_ParentContainedPath) isBrowseChildrenRequest_Parent() {}
+
+type BrowseChildrenReply struct {
+	state protoimpl.MessageState `protogen:"open.v1"`
+	// Direct children matching the filter, sorted areas-first then by
+	// case-insensitive display name (same order as the dashboard tree).
+	Children []*GalaxyObject `protobuf:"bytes,1,rep,name=children,proto3" json:"children,omitempty"`
+	// Non-empty when another page of siblings is available.
+	NextPageToken string `protobuf:"bytes,2,opt,name=next_page_token,json=nextPageToken,proto3" json:"next_page_token,omitempty"`
+	// Total matching direct children of the parent (post-filter).
+	TotalChildCount int32 `protobuf:"varint,3,opt,name=total_child_count,json=totalChildCount,proto3" json:"total_child_count,omitempty"`
+	// Parallel array, indexed with `children`. True when the child has at least
+	// one matching descendant under the same filter set. Lets a UI choose
+	// whether to draw an expand triangle without an extra round trip.
+	ChildHasChildren []bool `protobuf:"varint,4,rep,packed,name=child_has_children,json=childHasChildren,proto3" json:"child_has_children,omitempty"`
+	// Cache sequence this reply was projected from. Clients may pass it back as
+	// part of the page_token contract. Mismatch on the next page -> InvalidArgument.
+	CacheSequence uint64 `protobuf:"varint,5,opt,name=cache_sequence,json=cacheSequence,proto3" json:"cache_sequence,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *BrowseChildrenReply) Reset() {
+	*x = BrowseChildrenReply{}
+	mi := &file_galaxy_repository_proto_msgTypes[11]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *BrowseChildrenReply) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*BrowseChildrenReply) ProtoMessage() {}
+
+func (x *BrowseChildrenReply) ProtoReflect() protoreflect.Message {
+	mi := &file_galaxy_repository_proto_msgTypes[11]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use BrowseChildrenReply.ProtoReflect.Descriptor instead.
+func (*BrowseChildrenReply) Descriptor() ([]byte, []int) {
+	return file_galaxy_repository_proto_rawDescGZIP(), []int{11}
+}
+
+func (x *BrowseChildrenReply) GetChildren() []*GalaxyObject {
+	if x != nil {
+		return x.Children
+	}
+	return nil
+}
+
+func (x *BrowseChildrenReply) GetNextPageToken() string {
+	if x != nil {
+		return x.NextPageToken
+	}
+	return ""
+}
+
+func (x *BrowseChildrenReply) GetTotalChildCount() int32 {
+	if x != nil {
+		return x.TotalChildCount
+	}
+	return 0
+}
+
+func (x *BrowseChildrenReply) GetChildHasChildren() []bool {
+	if x != nil {
+		return x.ChildHasChildren
+	}
+	return nil
+}
+
+func (x *BrowseChildrenReply) GetCacheSequence() uint64 {
+	if x != nil {
+		return x.CacheSequence
+	}
+	return 0
+}
+
 var File_galaxy_repository_proto protoreflect.FileDescriptor
 
 const file_galaxy_repository_proto_rawDesc = "" +
@@ -897,12 +1151,35 @@ const file_galaxy_repository_proto_rawDesc = "" +
 	"\x17security_classification\x18\t \x01(\x05R\x16securityClassification\x12#\n" +
 	"\ris_historized\x18\n" +
 	" \x01(\bR\fisHistorized\x12\x19\n" +
-	"\bis_alarm\x18\v \x01(\bR\aisAlarm2\xcc\x03\n" +
+	"\bis_alarm\x18\v \x01(\bR\aisAlarm\"\x8c\x04\n" +
+	"\x15BrowseChildrenRequest\x12,\n" +
+	"\x11parent_gobject_id\x18\x01 \x01(\x05H\x00R\x0fparentGobjectId\x12(\n" +
+	"\x0fparent_tag_name\x18\x02 \x01(\tH\x00R\rparentTagName\x124\n" +
+	"\x15parent_contained_path\x18\x03 \x01(\tH\x00R\x13parentContainedPath\x12\x1b\n" +
+	"\tpage_size\x18\x04 \x01(\x05R\bpageSize\x12\x1d\n" +
+	"\n" +
+	"page_token\x18\x05 \x01(\tR\tpageToken\x12!\n" +
+	"\fcategory_ids\x18\x06 \x03(\x05R\vcategoryIds\x126\n" +
+	"\x17template_chain_contains\x18\a \x03(\tR\x15templateChainContains\x12\"\n" +
+	"\rtag_name_glob\x18\b \x01(\tR\vtagNameGlob\x122\n" +
+	"\x12include_attributes\x18\t \x01(\bH\x01R\x11includeAttributes\x88\x01\x01\x12,\n" +
+	"\x12alarm_bearing_only\x18\n" +
+	" \x01(\bR\x10alarmBearingOnly\x12'\n" +
+	"\x0fhistorized_only\x18\v \x01(\bR\x0ehistorizedOnlyB\b\n" +
+	"\x06parentB\x15\n" +
+	"\x13_include_attributes\"\xfe\x01\n" +
+	"\x13BrowseChildrenReply\x12>\n" +
+	"\bchildren\x18\x01 \x03(\v2\".galaxy_repository.v1.GalaxyObjectR\bchildren\x12&\n" +
+	"\x0fnext_page_token\x18\x02 \x01(\tR\rnextPageToken\x12*\n" +
+	"\x11total_child_count\x18\x03 \x01(\x05R\x0ftotalChildCount\x12,\n" +
+	"\x12child_has_children\x18\x04 \x03(\bR\x10childHasChildren\x12%\n" +
+	"\x0ecache_sequence\x18\x05 \x01(\x04R\rcacheSequence2\xb6\x04\n" +
 	"\x10GalaxyRepository\x12h\n" +
 	"\x0eTestConnection\x12+.galaxy_repository.v1.TestConnectionRequest\x1a).galaxy_repository.v1.TestConnectionReply\x12q\n" +
 	"\x11GetLastDeployTime\x12..galaxy_repository.v1.GetLastDeployTimeRequest\x1a,.galaxy_repository.v1.GetLastDeployTimeReply\x12q\n" +
 	"\x11DiscoverHierarchy\x12..galaxy_repository.v1.DiscoverHierarchyRequest\x1a,.galaxy_repository.v1.DiscoverHierarchyReply\x12h\n" +
-	"\x11WatchDeployEvents\x12..galaxy_repository.v1.WatchDeployEventsRequest\x1a!.galaxy_repository.v1.DeployEvent0\x01B-\xaa\x02*ZB.MOM.WW.MxGateway.Contracts.Proto.Galaxyb\x06proto3"
+	"\x11WatchDeployEvents\x12..galaxy_repository.v1.WatchDeployEventsRequest\x1a!.galaxy_repository.v1.DeployEvent0\x01\x12h\n" +
+	"\x0eBrowseChildren\x12+.galaxy_repository.v1.BrowseChildrenRequest\x1a).galaxy_repository.v1.BrowseChildrenReplyB-\xaa\x02*ZB.MOM.WW.MxGateway.Contracts.Proto.Galaxyb\x06proto3"
 
 var (
 	file_galaxy_repository_proto_rawDescOnce sync.Once
@@ -916,7 +1193,7 @@ func file_galaxy_repository_proto_rawDescGZIP() []byte {
 	return file_galaxy_repository_proto_rawDescData
 }
 
-var file_galaxy_repository_proto_msgTypes = make([]protoimpl.MessageInfo, 10)
+var file_galaxy_repository_proto_msgTypes = make([]protoimpl.MessageInfo, 12)
 var file_galaxy_repository_proto_goTypes = []any{
 	(*TestConnectionRequest)(nil),    // 0: galaxy_repository.v1.TestConnectionRequest
 	(*TestConnectionReply)(nil),      // 1: galaxy_repository.v1.TestConnectionReply
@@ -928,30 +1205,35 @@ var file_galaxy_repository_proto_goTypes = []any{
 	(*DeployEvent)(nil),              // 7: galaxy_repository.v1.DeployEvent
 	(*GalaxyObject)(nil),             // 8: galaxy_repository.v1.GalaxyObject
 	(*GalaxyAttribute)(nil),          // 9: galaxy_repository.v1.GalaxyAttribute
-	(*timestamppb.Timestamp)(nil),    // 10: google.protobuf.Timestamp
-	(*wrapperspb.Int32Value)(nil),    // 11: google.protobuf.Int32Value
+	(*BrowseChildrenRequest)(nil),    // 10: galaxy_repository.v1.BrowseChildrenRequest
+	(*BrowseChildrenReply)(nil),      // 11: galaxy_repository.v1.BrowseChildrenReply
+	(*timestamppb.Timestamp)(nil),    // 12: google.protobuf.Timestamp
+	(*wrapperspb.Int32Value)(nil),    // 13: google.protobuf.Int32Value
 }
 var file_galaxy_repository_proto_depIdxs = []int32{
-	10, // 0: galaxy_repository.v1.GetLastDeployTimeReply.time_of_last_deploy:type_name -> google.protobuf.Timestamp
-	11, // 1: galaxy_repository.v1.DiscoverHierarchyRequest.max_depth:type_name -> google.protobuf.Int32Value
+	12, // 0: galaxy_repository.v1.GetLastDeployTimeReply.time_of_last_deploy:type_name -> google.protobuf.Timestamp
+	13, // 1: galaxy_repository.v1.DiscoverHierarchyRequest.max_depth:type_name -> google.protobuf.Int32Value
 	8,  // 2: galaxy_repository.v1.DiscoverHierarchyReply.objects:type_name -> galaxy_repository.v1.GalaxyObject
-	10, // 3: galaxy_repository.v1.WatchDeployEventsRequest.last_seen_deploy_time:type_name -> google.protobuf.Timestamp
-	10, // 4: galaxy_repository.v1.DeployEvent.observed_at:type_name -> google.protobuf.Timestamp
-	10, // 5: galaxy_repository.v1.DeployEvent.time_of_last_deploy:type_name -> google.protobuf.Timestamp
+	12, // 3: galaxy_repository.v1.WatchDeployEventsRequest.last_seen_deploy_time:type_name -> google.protobuf.Timestamp
+	12, // 4: galaxy_repository.v1.DeployEvent.observed_at:type_name -> google.protobuf.Timestamp
+	12, // 5: galaxy_repository.v1.DeployEvent.time_of_last_deploy:type_name -> google.protobuf.Timestamp
 	9,  // 6: galaxy_repository.v1.GalaxyObject.attributes:type_name -> galaxy_repository.v1.GalaxyAttribute
-	0,  // 7: galaxy_repository.v1.GalaxyRepository.TestConnection:input_type -> galaxy_repository.v1.TestConnectionRequest
-	2,  // 8: galaxy_repository.v1.GalaxyRepository.GetLastDeployTime:input_type -> galaxy_repository.v1.GetLastDeployTimeRequest
-	4,  // 9: galaxy_repository.v1.GalaxyRepository.DiscoverHierarchy:input_type -> galaxy_repository.v1.DiscoverHierarchyRequest
-	6,  // 10: galaxy_repository.v1.GalaxyRepository.WatchDeployEvents:input_type -> galaxy_repository.v1.WatchDeployEventsRequest
-	1,  // 11: galaxy_repository.v1.GalaxyRepository.TestConnection:output_type -> galaxy_repository.v1.TestConnectionReply
-	3,  // 12: galaxy_repository.v1.GalaxyRepository.GetLastDeployTime:output_type -> galaxy_repository.v1.GetLastDeployTimeReply
-	5,  // 13: galaxy_repository.v1.GalaxyRepository.DiscoverHierarchy:output_type -> galaxy_repository.v1.DiscoverHierarchyReply
-	7,  // 14: galaxy_repository.v1.GalaxyRepository.WatchDeployEvents:output_type -> galaxy_repository.v1.DeployEvent
-	11, // [11:15] is the sub-list for method output_type
-	7,  // [7:11] is the sub-list for method input_type
-	7,  // [7:7] is the sub-list for extension type_name
-	7,  // [7:7] is the sub-list for extension extendee
-	0,  // [0:7] is the sub-list for field type_name
+	8,  // 7: galaxy_repository.v1.BrowseChildrenReply.children:type_name -> galaxy_repository.v1.GalaxyObject
+	0,  // 8: galaxy_repository.v1.GalaxyRepository.TestConnection:input_type -> galaxy_repository.v1.TestConnectionRequest
+	2,  // 9: galaxy_repository.v1.GalaxyRepository.GetLastDeployTime:input_type -> galaxy_repository.v1.GetLastDeployTimeRequest
+	4,  // 10: galaxy_repository.v1.GalaxyRepository.DiscoverHierarchy:input_type -> galaxy_repository.v1.DiscoverHierarchyRequest
+	6,  // 11: galaxy_repository.v1.GalaxyRepository.WatchDeployEvents:input_type -> galaxy_repository.v1.WatchDeployEventsRequest
+	10, // 12: galaxy_repository.v1.GalaxyRepository.BrowseChildren:input_type -> galaxy_repository.v1.BrowseChildrenRequest
+	1,  // 13: galaxy_repository.v1.GalaxyRepository.TestConnection:output_type -> galaxy_repository.v1.TestConnectionReply
+	3,  // 14: galaxy_repository.v1.GalaxyRepository.GetLastDeployTime:output_type -> galaxy_repository.v1.GetLastDeployTimeReply
+	5,  // 15: galaxy_repository.v1.GalaxyRepository.DiscoverHierarchy:output_type -> galaxy_repository.v1.DiscoverHierarchyReply
+	7,  // 16: galaxy_repository.v1.GalaxyRepository.WatchDeployEvents:output_type -> galaxy_repository.v1.DeployEvent
+	11, // 17: galaxy_repository.v1.GalaxyRepository.BrowseChildren:output_type -> galaxy_repository.v1.BrowseChildrenReply
+	13, // [13:18] is the sub-list for method output_type
+	8,  // [8:13] is the sub-list for method input_type
+	8,  // [8:8] is the sub-list for extension type_name
+	8,  // [8:8] is the sub-list for extension extendee
+	0,  // [0:8] is the sub-list for field type_name
 }
 
 func init() { file_galaxy_repository_proto_init() }
@@ -964,13 +1246,18 @@ func file_galaxy_repository_proto_init() {
 		(*DiscoverHierarchyRequest_RootTagName)(nil),
 		(*DiscoverHierarchyRequest_RootContainedPath)(nil),
 	}
+	file_galaxy_repository_proto_msgTypes[10].OneofWrappers = []any{
+		(*BrowseChildrenRequest_ParentGobjectId)(nil),
+		(*BrowseChildrenRequest_ParentTagName)(nil),
+		(*BrowseChildrenRequest_ParentContainedPath)(nil),
+	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
 		File: protoimpl.DescBuilder{
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: unsafe.Slice(unsafe.StringData(file_galaxy_repository_proto_rawDesc), len(file_galaxy_repository_proto_rawDesc)),
 			NumEnums:      0,
-			NumMessages:   10,
+			NumMessages:   12,
 			NumExtensions: 0,
 			NumServices:   1,
 		},

clients/go/internal/generated/galaxy_repository_grpc.pb.go

@@ -1,6 +1,6 @@
 // Code generated by protoc-gen-go-grpc. DO NOT EDIT.
 // versions:
-// - protoc-gen-go-grpc v1.6.1
+// - protoc-gen-go-grpc v1.6.2
 // - protoc             v7.34.1
 // source: galaxy_repository.proto
 
@@ -23,6 +23,7 @@ const (
 	GalaxyRepository_GetLastDeployTime_FullMethodName = "/galaxy_repository.v1.GalaxyRepository/GetLastDeployTime"
 	GalaxyRepository_DiscoverHierarchy_FullMethodName = "/galaxy_repository.v1.GalaxyRepository/DiscoverHierarchy"
 	GalaxyRepository_WatchDeployEvents_FullMethodName = "/galaxy_repository.v1.GalaxyRepository/WatchDeployEvents"
+	GalaxyRepository_BrowseChildren_FullMethodName    = "/galaxy_repository.v1.GalaxyRepository/BrowseChildren"
 )
 
 // GalaxyRepositoryClient is the client API for GalaxyRepository service.
@@ -44,6 +45,11 @@ type GalaxyRepositoryClient interface {
 	// increasing per server start; gaps indicate the per-subscriber buffer dropped
 	// older events because the client was too slow.
 	WatchDeployEvents(ctx context.Context, in *WatchDeployEventsRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[DeployEvent], error)
+	// Returns the direct children of a parent object (or the root objects when
+	// `parent` is unset). Designed for OPC UA-style lazy expand: clients walk
+	// one level at a time instead of paging the full hierarchy. Filters mirror
+	// DiscoverHierarchy exactly. Backed by the same shared hierarchy cache.
+	BrowseChildren(ctx context.Context, in *BrowseChildrenRequest, opts ...grpc.CallOption) (*BrowseChildrenReply, error)
 }
 
 type galaxyRepositoryClient struct {
@@ -103,6 +109,16 @@ func (c *galaxyRepositoryClient) WatchDeployEvents(ctx context.Context, in *Watc
 // This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
 type GalaxyRepository_WatchDeployEventsClient = grpc.ServerStreamingClient[DeployEvent]
 
+func (c *galaxyRepositoryClient) BrowseChildren(ctx context.Context, in *BrowseChildrenRequest, opts ...grpc.CallOption) (*BrowseChildrenReply, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(BrowseChildrenReply)
+	err := c.cc.Invoke(ctx, GalaxyRepository_BrowseChildren_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 // GalaxyRepositoryServer is the server API for GalaxyRepository service.
 // All implementations must embed UnimplementedGalaxyRepositoryServer
 // for forward compatibility.
@@ -122,6 +138,11 @@ type GalaxyRepositoryServer interface {
 	// increasing per server start; gaps indicate the per-subscriber buffer dropped
 	// older events because the client was too slow.
 	WatchDeployEvents(*WatchDeployEventsRequest, grpc.ServerStreamingServer[DeployEvent]) error
+	// Returns the direct children of a parent object (or the root objects when
+	// `parent` is unset). Designed for OPC UA-style lazy expand: clients walk
+	// one level at a time instead of paging the full hierarchy. Filters mirror
+	// DiscoverHierarchy exactly. Backed by the same shared hierarchy cache.
+	BrowseChildren(context.Context, *BrowseChildrenRequest) (*BrowseChildrenReply, error)
 	mustEmbedUnimplementedGalaxyRepositoryServer()
 }
 
@@ -144,6 +165,9 @@ func (UnimplementedGalaxyRepositoryServer) DiscoverHierarchy(context.Context, *D
 func (UnimplementedGalaxyRepositoryServer) WatchDeployEvents(*WatchDeployEventsRequest, grpc.ServerStreamingServer[DeployEvent]) error {
 	return status.Error(codes.Unimplemented, "method WatchDeployEvents not implemented")
 }
+func (UnimplementedGalaxyRepositoryServer) BrowseChildren(context.Context, *BrowseChildrenRequest) (*BrowseChildrenReply, error) {
+	return nil, status.Error(codes.Unimplemented, "method BrowseChildren not implemented")
+}
 func (UnimplementedGalaxyRepositoryServer) mustEmbedUnimplementedGalaxyRepositoryServer() {}
 func (UnimplementedGalaxyRepositoryServer) testEmbeddedByValue()                          {}
 
@@ -230,6 +254,24 @@ func _GalaxyRepository_WatchDeployEvents_Handler(srv interface{}, stream grpc.Se
 // This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
 type GalaxyRepository_WatchDeployEventsServer = grpc.ServerStreamingServer[DeployEvent]
 
+func _GalaxyRepository_BrowseChildren_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(BrowseChildrenRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(GalaxyRepositoryServer).BrowseChildren(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: GalaxyRepository_BrowseChildren_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(GalaxyRepositoryServer).BrowseChildren(ctx, req.(*BrowseChildrenRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
 // GalaxyRepository_ServiceDesc is the grpc.ServiceDesc for GalaxyRepository service.
 // It's only intended for direct use with grpc.RegisterService,
 // and not to be introspected or modified (even as a copy)
@@ -249,6 +291,10 @@ var GalaxyRepository_ServiceDesc = grpc.ServiceDesc{
 			MethodName: "DiscoverHierarchy",
 			Handler:    _GalaxyRepository_DiscoverHierarchy_Handler,
 		},
+		{
+			MethodName: "BrowseChildren",
+			Handler:    _GalaxyRepository_BrowseChildren_Handler,
+		},
 	},
 	Streams: []grpc.StreamDesc{
 		{

clients/go/internal/generated/mxaccess_gateway.pb.go

@@ -725,9 +725,10 @@ func (SessionState) EnumDescriptor() ([]byte, []int) {
 	return file_mxaccess_gateway_proto_rawDescGZIP(), []int{8}
 }
 
-// Public request shape for QueryActiveAlarms. session_id is currently unused
-// (the snapshot is session-less) but reserved so a future per-session view
-// can be added without a wire break.
+// Public request shape for QueryActiveAlarms.
+// Clients may leave `session_id` empty; the gateway currently ignores it and
+// serves the session-less central-monitor cache. A future version may use it
+// to scope the snapshot to one session.
 type QueryActiveAlarmsRequest struct {
 	state               protoimpl.MessageState `protogen:"open.v1"`
 	SessionId           string                 `protobuf:"bytes,1,opt,name=session_id,json=sessionId,proto3" json:"session_id,omitempty"`

clients/go/internal/generated/mxaccess_gateway_grpc.pb.go

@@ -1,6 +1,6 @@
 // Code generated by protoc-gen-go-grpc. DO NOT EDIT.
 // versions:
-// - protoc-gen-go-grpc v1.6.1
+// - protoc-gen-go-grpc v1.6.2
 // - protoc             v7.34.1
 // source: mxaccess_gateway.proto
 
@@ -50,6 +50,9 @@ type MxAccessGatewayClient interface {
 	// reconnect to seed Part 9 client state, or to reconcile alarms that may
 	// have been missed during a transport blip. Streamed so callers can
 	// begin processing without buffering the full set.
+	// `QueryActiveAlarmsRequest.alarm_filter_prefix` optionally narrows the
+	// snapshot to alarms whose `alarm_full_reference` starts with the given
+	// prefix; an empty prefix returns the full set.
 	QueryActiveAlarms(ctx context.Context, in *QueryActiveAlarmsRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[ActiveAlarmSnapshot], error)
 }
 
@@ -180,6 +183,9 @@ type MxAccessGatewayServer interface {
 	// reconnect to seed Part 9 client state, or to reconcile alarms that may
 	// have been missed during a transport blip. Streamed so callers can
 	// begin processing without buffering the full set.
+	// `QueryActiveAlarmsRequest.alarm_filter_prefix` optionally narrows the
+	// snapshot to alarms whose `alarm_full_reference` starts with the given
+	// prefix; an empty prefix returns the full set.
 	QueryActiveAlarms(*QueryActiveAlarmsRequest, grpc.ServerStreamingServer[ActiveAlarmSnapshot]) error
 	mustEmbedUnimplementedMxAccessGatewayServer()
 }

clients/go/mxgateway/alarms_test.go

@@ -168,6 +168,66 @@ func TestQueryActiveAlarmsPassesFilterPrefix(t *testing.T) {
 	}
 }
 
+func TestStreamAlarmsPassesFilterPrefixAndReceivesFeedMessages(t *testing.T) {
+	fake := &fakeGatewayWithAlarms{
+		feedMessages: []*pb.AlarmFeedMessage{
+			{
+				Payload: &pb.AlarmFeedMessage_ActiveAlarm{
+					ActiveAlarm: &pb.ActiveAlarmSnapshot{
+						AlarmFullReference: "Tank01.Level.HiHi",
+						CurrentState:       pb.AlarmConditionState_ALARM_CONDITION_STATE_ACTIVE,
+					},
+				},
+			},
+			{
+				Payload: &pb.AlarmFeedMessage_SnapshotComplete{
+					SnapshotComplete: true,
+				},
+			},
+		},
+	}
+	client, cleanup := newBufconnClientWithAlarms(t, fake)
+	defer cleanup()
+
+	stream, err := client.StreamAlarms(context.Background(), &pb.StreamAlarmsRequest{
+		AlarmFilterPrefix: "Tank01.",
+	})
+	if err != nil {
+		t.Fatalf("StreamAlarms() error = %v", err)
+	}
+
+	var received []*pb.AlarmFeedMessage
+	for {
+		msg, err := stream.Recv()
+		if errors.Is(err, io.EOF) {
+			break
+		}
+		if err != nil {
+			t.Fatalf("stream.Recv() error = %v", err)
+		}
+		received = append(received, msg)
+	}
+	if len(received) != 2 {
+		t.Fatalf("received count = %d, want 2", len(received))
+	}
+	if got := fake.streamRequest.GetAlarmFilterPrefix(); got != "Tank01." {
+		t.Fatalf("captured filter prefix = %q", got)
+	}
+	if got := fake.streamAuth; got != "Bearer test-api-key" {
+		t.Fatalf("stream authorization metadata = %q", got)
+	}
+}
+
+func TestStreamAlarmsRejectsNilRequest(t *testing.T) {
+	fake := &fakeGatewayWithAlarms{}
+	client, cleanup := newBufconnClientWithAlarms(t, fake)
+	defer cleanup()
+
+	if _, err := client.StreamAlarms(context.Background(), nil); err == nil {
+		t.Fatal("StreamAlarms(nil) returned no error")
+	}
+}
+
 type fakeGatewayWithAlarms struct {
 	pb.UnimplementedMxAccessGatewayServer
 
@@ -178,6 +238,10 @@ type fakeGatewayWithAlarms struct {
 
 	queryRequest    *pb.QueryActiveAlarmsRequest
 	activeSnapshots []*pb.ActiveAlarmSnapshot
+
+	streamRequest *pb.StreamAlarmsRequest
+	feedMessages  []*pb.AlarmFeedMessage
+	streamAuth    string
 }
 
 func (s *fakeGatewayWithAlarms) AcknowledgeAlarm(ctx context.Context, req *pb.AcknowledgeAlarmRequest) (*pb.AcknowledgeAlarmReply, error) {
@@ -207,6 +271,17 @@ func (s *fakeGatewayWithAlarms) QueryActiveAlarms(req *pb.QueryActiveAlarmsReque
 	return nil
 }
 
+func (s *fakeGatewayWithAlarms) StreamAlarms(req *pb.StreamAlarmsRequest, stream grpc.ServerStreamingServer[pb.AlarmFeedMessage]) error {
+	s.streamRequest = req
+	s.streamAuth = authorizationFromContext(stream.Context())
+	for _, msg := range s.feedMessages {
+		if err := stream.Send(msg); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func newBufconnClientWithAlarms(t *testing.T, fake *fakeGatewayWithAlarms) (*Client, func()) {
 	t.Helper()
 	listener := bufconn.Listen(bufSize)

clients/go/mxgateway/client.go

@@ -222,10 +222,22 @@ func resolveTransportCredentials(opts Options) (credentials.TransportCredentials
 		return credentials.NewTLS(cfg), nil
 	}
 
-	return credentials.NewTLS(&tls.Config{
-		MinVersion: tls.VersionTLS12,
-		ServerName: opts.ServerNameOverride,
-	}), nil
+	return credentials.NewTLS(tlsConfigForOptions(opts)), nil
+}
+
+// tlsConfigForOptions returns the *tls.Config for the no-CA, no-custom-config TLS path.
+// It returns nil when the caller should use a different credentials path (CA file or custom TLSConfig).
+// Exposed as an internal helper so unit tests can assert the InsecureSkipVerify posture.
+func tlsConfigForOptions(opts Options) *tls.Config {
+	// CA file and custom TLSConfig take their own paths in resolveTransportCredentials.
+	if opts.CACertFile != "" || opts.TLSConfig != nil {
+		return nil
+	}
+	return &tls.Config{
+		MinVersion:         tls.VersionTLS12,
+		ServerName:         opts.ServerNameOverride,
+		InsecureSkipVerify: !opts.RequireCertificateValidation, //nolint:gosec // internal tool; self-signed gateway cert expected; opt-in strict via RequireCertificateValidation
+	}
 }
 
 // OpenSessionOptions describes fields used to create an OpenSessionRequest.

clients/go/mxgateway/client_session_test.go

@@ -230,6 +230,206 @@ func TestSubscribeBulkBuildsOneBulkCommandAndReturnsResults(t *testing.T) {
 	}
 }
 
+func TestWriteBulkBuildsOneBulkCommandAndReturnsPerEntryResults(t *testing.T) {
+	fake := &fakeGatewayServer{
+		invokeReply: &pb.MxCommandReply{
+			SessionId: "session-1",
+			Kind:      pb.MxCommandKind_MX_COMMAND_KIND_WRITE_BULK,
+			ProtocolStatus: &pb.ProtocolStatus{
+				Code: pb.ProtocolStatusCode_PROTOCOL_STATUS_CODE_OK,
+			},
+			Payload: &pb.MxCommandReply_WriteBulk{
+				WriteBulk: &pb.BulkWriteReply{
+					Results: []*pb.BulkWriteResult{
+						{ItemHandle: 10, WasSuccessful: true},
+						{ItemHandle: 11, WasSuccessful: true},
+					},
+				},
+			},
+		},
+	}
+	client, cleanup := newBufconnClient(t, fake)
+	defer cleanup()
+	session := NewSessionForID(client, "session-1")
+
+	entries := []*WriteBulkEntry{
+		{ItemHandle: 10, Value: Int32Value(7), UserId: 100},
+		{ItemHandle: 11, Value: Int32Value(8), UserId: 100},
+	}
+	results, err := session.WriteBulk(context.Background(), 12, entries)
+	if err != nil {
+		t.Fatalf("WriteBulk() error = %v", err)
+	}
+	if len(results) != 2 {
+		t.Fatalf("results len = %d, want 2", len(results))
+	}
+	req := fake.invokeRequest
+	if req.GetCommand().GetKind() != pb.MxCommandKind_MX_COMMAND_KIND_WRITE_BULK {
+		t.Fatalf("command kind = %s", req.GetCommand().GetKind())
+	}
+	if got := req.GetCommand().GetWriteBulk().GetEntries(); len(got) != 2 {
+		t.Fatalf("entry count = %d, want 2", len(got))
+	}
+}
+
+func TestWriteBulkRejectsNilEntries(t *testing.T) {
+	fake := &fakeGatewayServer{}
+	client, cleanup := newBufconnClient(t, fake)
+	defer cleanup()
+	session := NewSessionForID(client, "session-1")
+
+	if _, err := session.WriteBulk(context.Background(), 12, nil); err == nil {
+		t.Fatal("WriteBulk(nil) returned no error")
+	}
+	if _, err := session.Write2Bulk(context.Background(), 12, nil); err == nil {
+		t.Fatal("Write2Bulk(nil) returned no error")
+	}
+	if _, err := session.WriteSecuredBulk(context.Background(), 12, nil); err == nil {
+		t.Fatal("WriteSecuredBulk(nil) returned no error")
+	}
+	if _, err := session.WriteSecured2Bulk(context.Background(), 12, nil); err == nil {
+		t.Fatal("WriteSecured2Bulk(nil) returned no error")
+	}
+	if _, err := session.ReadBulk(context.Background(), 12, nil, 0); err == nil {
+		t.Fatal("ReadBulk(nil) returned no error")
+	}
+}
+
+func TestBulkMethodsShortCircuitOnEmptySliceWithoutRoundTrip(t *testing.T) {
+	fake := &fakeGatewayServer{
+		invokeReply: &pb.MxCommandReply{
+			ProtocolStatus: &pb.ProtocolStatus{
+				Code: pb.ProtocolStatusCode_PROTOCOL_STATUS_CODE_OK,
+			},
+		},
+	}
+	client, cleanup := newBufconnClient(t, fake)
+	defer cleanup()
+	session := NewSessionForID(client, "session-1")
+
+	results, err := session.WriteBulk(context.Background(), 12, []*WriteBulkEntry{})
+	if err != nil {
+		t.Fatalf("WriteBulk(empty) error = %v", err)
+	}
+	if len(results) != 0 {
+		t.Fatalf("WriteBulk(empty) results len = %d, want 0", len(results))
+	}
+	if fake.invokeRequest != nil {
+		t.Fatal("WriteBulk(empty) sent a round trip; expected short-circuit")
+	}
+
+	results2, err := session.Write2Bulk(context.Background(), 12, []*Write2BulkEntry{})
+	if err != nil {
+		t.Fatalf("Write2Bulk(empty) error = %v", err)
+	}
+	if len(results2) != 0 {
+		t.Fatalf("Write2Bulk(empty) results len = %d, want 0", len(results2))
+	}
+	if fake.invokeRequest != nil {
+		t.Fatal("Write2Bulk(empty) sent a round trip; expected short-circuit")
+	}
+
+	results3, err := session.WriteSecuredBulk(context.Background(), 12, []*WriteSecuredBulkEntry{})
+	if err != nil {
+		t.Fatalf("WriteSecuredBulk(empty) error = %v", err)
+	}
+	if len(results3) != 0 {
+		t.Fatalf("WriteSecuredBulk(empty) results len = %d, want 0", len(results3))
+	}
+	if fake.invokeRequest != nil {
+		t.Fatal("WriteSecuredBulk(empty) sent a round trip; expected short-circuit")
+	}
+
+	results4, err := session.WriteSecured2Bulk(context.Background(), 12, []*WriteSecured2BulkEntry{})
+	if err != nil {
+		t.Fatalf("WriteSecured2Bulk(empty) error = %v", err)
+	}
+	if len(results4) != 0 {
+		t.Fatalf("WriteSecured2Bulk(empty) results len = %d, want 0", len(results4))
+	}
+	if fake.invokeRequest != nil {
+		t.Fatal("WriteSecured2Bulk(empty) sent a round trip; expected short-circuit")
+	}
+
+	readResults, err := session.ReadBulk(context.Background(), 12, []string{}, 0)
+	if err != nil {
+		t.Fatalf("ReadBulk(empty) error = %v", err)
+	}
+	if len(readResults) != 0 {
+		t.Fatalf("ReadBulk(empty) results len = %d, want 0", len(readResults))
+	}
+	if fake.invokeRequest != nil {
+		t.Fatal("ReadBulk(empty) sent a round trip; expected short-circuit")
+	}
+}
+
+func TestReadBulkForwardsTimeoutAndUnpacksCachedFlag(t *testing.T) {
+	fake := &fakeGatewayServer{
+		invokeReply: &pb.MxCommandReply{
+			SessionId: "session-1",
+			Kind:      pb.MxCommandKind_MX_COMMAND_KIND_READ_BULK,
+			ProtocolStatus: &pb.ProtocolStatus{
+				Code: pb.ProtocolStatusCode_PROTOCOL_STATUS_CODE_OK,
+			},
+			Payload: &pb.MxCommandReply_ReadBulk{
+				ReadBulk: &pb.BulkReadReply{
+					Results: []*pb.BulkReadResult{
+						{TagAddress: "Tank01.Level", WasSuccessful: true, WasCached: true},
+						{TagAddress: "Tank02.Level", WasSuccessful: true, WasCached: false},
+					},
+				},
+			},
+		},
+	}
+	client, cleanup := newBufconnClient(t, fake)
+	defer cleanup()
+	session := NewSessionForID(client, "session-1")
+
+	results, err := session.ReadBulk(context.Background(), 12, []string{"Tank01.Level", "Tank02.Level"}, 250*time.Millisecond)
+	if err != nil {
+		t.Fatalf("ReadBulk() error = %v", err)
+	}
+	if len(results) != 2 {
+		t.Fatalf("results len = %d, want 2", len(results))
+	}
+	if !results[0].GetWasCached() || results[1].GetWasCached() {
+		t.Fatalf("WasCached flags = [%v %v], want [true false]", results[0].GetWasCached(), results[1].GetWasCached())
+	}
+	req := fake.invokeRequest
+	if req.GetCommand().GetKind() != pb.MxCommandKind_MX_COMMAND_KIND_READ_BULK {
+		t.Fatalf("command kind = %s", req.GetCommand().GetKind())
+	}
+	if got := req.GetCommand().GetReadBulk().GetTimeoutMs(); got != 250 {
+		t.Fatalf("timeout ms = %d, want 250", got)
+	}
+}
+
+func TestReadBulkSaturatesTimeoutAboveMaxUint32(t *testing.T) {
+	fake := &fakeGatewayServer{
+		invokeReply: &pb.MxCommandReply{
+			SessionId: "session-1",
+			Kind:      pb.MxCommandKind_MX_COMMAND_KIND_READ_BULK,
+			ProtocolStatus: &pb.ProtocolStatus{
+				Code: pb.ProtocolStatusCode_PROTOCOL_STATUS_CODE_OK,
+			},
+		},
+	}
+	client, cleanup := newBufconnClient(t, fake)
+	defer cleanup()
+	session := NewSessionForID(client, "session-1")
+
+	// 100 days in milliseconds exceeds MaxUint32 (~49.7 days).
+	hugeTimeout := 100 * 24 * time.Hour
+	_, err := session.ReadBulk(context.Background(), 12, []string{"Tank01.Level"}, hugeTimeout)
+	if err != nil {
+		t.Fatalf("ReadBulk() error = %v", err)
+	}
+	got := fake.invokeRequest.GetCommand().GetReadBulk().GetTimeoutMs()
+	if got != ^uint32(0) {
+		t.Fatalf("timeout ms = %d, want %d (MaxUint32)", got, ^uint32(0))
+	}
+}
+
 func TestInvokeReturnsTypedMxAccessErrorWithRawReply(t *testing.T) {
 	hresult := int32(-2147467259)
 	fake := &fakeGatewayServer{

clients/go/mxgateway/client_tls_test.go

@@ -0,0 +1,59 @@
+package mxgateway
+
+import (
+	"crypto/tls"
+	"testing"
+)
+
+// tlsConfigFromOptions is the internal helper under test.
+// It extracts the *tls.Config from the no-CA TLS path of resolveTransportCredentials.
+// We exercise it directly to avoid needing a real dial target.
+
+func TestTLSInsecureSkipVerify_DefaultTrue(t *testing.T) {
+	cfg := tlsConfigForOptions(Options{
+		Endpoint: "localhost:5120",
+	})
+	if cfg == nil {
+		t.Fatal("expected non-nil tls.Config")
+	}
+	if !cfg.InsecureSkipVerify {
+		t.Error("InsecureSkipVerify should be true by default when no CA is pinned")
+	}
+}
+
+func TestTLSInsecureSkipVerify_FalseWhenRequireCertificateValidation(t *testing.T) {
+	cfg := tlsConfigForOptions(Options{
+		Endpoint:                     "localhost:5120",
+		RequireCertificateValidation: true,
+	})
+	if cfg == nil {
+		t.Fatal("expected non-nil tls.Config")
+	}
+	if cfg.InsecureSkipVerify {
+		t.Error("InsecureSkipVerify should be false when RequireCertificateValidation is true")
+	}
+}
+
+func TestTLSInsecureSkipVerify_FalseWhenCACertFileSet(t *testing.T) {
+	// When a CA file is pinned, the CA-verification path is taken instead.
+	// tlsConfigForOptions should return nil (the CA path does not use our helper).
+	cfg := tlsConfigForOptions(Options{
+		Endpoint:   "localhost:5120",
+		CACertFile: "/some/ca.pem",
+	})
+	if cfg != nil {
+		t.Error("expected nil tls.Config when CACertFile is set (CA path taken)")
+	}
+}
+
+func TestTLSInsecureSkipVerify_FalseWhenCustomTLSConfig(t *testing.T) {
+	// When TLSConfig is supplied explicitly, our default skip-verify must not overwrite it.
+	custom := &tls.Config{MinVersion: tls.VersionTLS13}
+	cfg := tlsConfigForOptions(Options{
+		Endpoint:  "localhost:5120",
+		TLSConfig: custom,
+	})
+	if cfg != nil {
+		t.Error("expected nil tls.Config when TLSConfig is already set (custom config path taken)")
+	}
+}

clients/go/mxgateway/galaxy.go

@@ -3,7 +3,9 @@ package mxgateway
 import (
 	"context"
 	"errors"
+	"fmt"
 	"io"
+	"sync"
 	"time"
 
 	pb "gitea.dohertylan.com/dohertj2/mxaccessgw/clients/go/internal/generated"
@@ -13,6 +15,14 @@ import (
 	"google.golang.org/protobuf/types/known/timestamppb"
 )
 
+// browseChildrenPageSize is the per-request page size used by the lazy walker.
+const browseChildrenPageSize = 500
+
+// discoverHierarchyPageSize is the per-request page size used by DiscoverHierarchy.
+// Mirrors the .NET client constant so large galaxies are not silently truncated
+// by the server's default page cap.
+const discoverHierarchyPageSize = 5000
+
 // RawGalaxyRepositoryClient is the generated gRPC client interface for the
 // Galaxy Repository service exposed for callers that need direct contract
 // access.
@@ -40,6 +50,10 @@ type (
 	WatchDeployEventsRequest = pb.WatchDeployEventsRequest
 	// DeployEvent is one Galaxy Repository deploy event.
 	DeployEvent = pb.DeployEvent
+	// BrowseChildrenRequest is the request for BrowseChildren.
+	BrowseChildrenRequest = pb.BrowseChildrenRequest
+	// BrowseChildrenReply is the reply for BrowseChildren.
+	BrowseChildrenReply = pb.BrowseChildrenReply
 )
 
 // RawDeployEventStream is the generated WatchDeployEvents client stream.
@@ -146,16 +160,35 @@ func (c *GalaxyClient) GetLastDeployTime(ctx context.Context) (time.Time, bool,
 
 // DiscoverHierarchy returns the deployed Galaxy object hierarchy with each
 // object's dynamic attributes. The objects are returned in the order supplied
-// by the server.
+// by the server. The call pages over the server's NextPageToken until the
+// server signals it has no more results, matching the .NET client.
 func (c *GalaxyClient) DiscoverHierarchy(ctx context.Context) ([]*GalaxyObject, error) {
-	callCtx, cancel := c.callContext(ctx)
-	defer cancel()
-
-	reply, err := c.raw.DiscoverHierarchy(callCtx, &pb.DiscoverHierarchyRequest{})
-	if err != nil {
-		return nil, &GatewayError{Op: "galaxy discover hierarchy", Err: err}
+	var objects []*GalaxyObject
+	pageToken := ""
+	seen := map[string]struct{}{}
+	for {
+		callCtx, cancel := c.callContext(ctx)
+		reply, err := c.raw.DiscoverHierarchy(callCtx, &pb.DiscoverHierarchyRequest{
+			PageSize:  discoverHierarchyPageSize,
+			PageToken: pageToken,
+		})
+		cancel()
+		if err != nil {
+			return nil, &GatewayError{Op: "galaxy discover hierarchy", Err: err}
+		}
+		objects = append(objects, reply.GetObjects()...)
+		pageToken = reply.GetNextPageToken()
+		if pageToken == "" {
+			return objects, nil
+		}
+		if _, dup := seen[pageToken]; dup {
+			return nil, &GatewayError{
+				Op:  "galaxy discover hierarchy",
+				Err: fmt.Errorf("repeated page token %q", pageToken),
+			}
+		}
+		seen[pageToken] = struct{}{}
 	}
-	return reply.GetObjects(), nil
 }
 
 // WatchDeployEventsRaw starts the generated WatchDeployEvents stream for callers
@@ -238,6 +271,206 @@ func (c *GalaxyClient) Close() error {
 	return c.conn.Close()
 }
 
+// LazyBrowseNode is one node in a lazy Galaxy hierarchy walk produced by
+// (*GalaxyClient).Browse. Children are not fetched until Expand is called.
+// The node is safe for concurrent use; concurrent Expand calls coalesce onto
+// a single in-flight RPC and do not block snapshot accessors.
+type LazyBrowseNode struct {
+	client          *GalaxyClient
+	object          *pb.GalaxyObject
+	hasChildrenHint bool
+	options         BrowseChildrenOptions
+
+	// expandLock gates inspection and mutation of expand-coordination state
+	// (expanding, expandDone, expandErr). It is held only briefly; the BrowseChildren
+	// RPC itself runs outside this lock so concurrent readers and waiters are not blocked.
+	expandLock sync.Mutex
+	expanding  bool
+	expandDone chan struct{}
+	expandErr  error
+
+	// mu protects the children snapshot and isExpanded flag for concurrent
+	// Children() / IsExpanded() readers.
+	mu         sync.RWMutex
+	children   []*LazyBrowseNode
+	isExpanded bool
+}
+
+// Object returns the underlying GalaxyObject describing this node.
+func (n *LazyBrowseNode) Object() *pb.GalaxyObject { return n.object }
+
+// HasChildrenHint reports the server-supplied hint on whether this node has
+// matching descendants under the current filter set.
+func (n *LazyBrowseNode) HasChildrenHint() bool { return n.hasChildrenHint }
+
+// Children returns a snapshot copy of the currently-loaded child nodes. Returns
+// an empty slice when Expand has not yet been called.
+func (n *LazyBrowseNode) Children() []*LazyBrowseNode {
+	n.mu.RLock()
+	defer n.mu.RUnlock()
+	out := make([]*LazyBrowseNode, len(n.children))
+	copy(out, n.children)
+	return out
+}
+
+// IsExpanded reports whether Expand has completed successfully on this node.
+func (n *LazyBrowseNode) IsExpanded() bool {
+	n.mu.RLock()
+	defer n.mu.RUnlock()
+	return n.isExpanded
+}
+
+// Expand fetches this node's direct children via BrowseChildren when they have
+// not yet been loaded. Subsequent calls after a successful Expand are a no-op
+// and do not issue another RPC.
+//
+// Expand is safe to call concurrently from multiple goroutines: callers that
+// arrive while an expansion is in flight wait on the active RPC and share its
+// result instead of issuing a second RPC. The RPC itself runs without holding
+// the snapshot mutex, so concurrent Children() and IsExpanded() callers are
+// not blocked for the duration of the network round trip.
+//
+// Failure semantics: a failed expansion surfaces the same error to every
+// in-flight waiter, but the node is left in its pre-call state (isExpanded =
+// false, no in-flight expansion). The next Expand call therefore retries with
+// a fresh RPC; failures are not sticky.
+func (n *LazyBrowseNode) Expand(ctx context.Context) error {
+	// Fast path: already expanded.
+	n.mu.RLock()
+	if n.isExpanded {
+		n.mu.RUnlock()
+		return nil
+	}
+	n.mu.RUnlock()
+
+	// Either start a new expansion or wait on an existing one.
+	n.expandLock.Lock()
+	n.mu.RLock()
+	alreadyExpanded := n.isExpanded
+	n.mu.RUnlock()
+	if alreadyExpanded {
+		n.expandLock.Unlock()
+		return nil
+	}
+	if n.expanding {
+		done := n.expandDone
+		n.expandLock.Unlock()
+		select {
+		case <-done:
+			n.expandLock.Lock()
+			err := n.expandErr
+			n.expandLock.Unlock()
+			return err
+		case <-ctx.Done():
+			return ctx.Err()
+		}
+	}
+	n.expanding = true
+	n.expandDone = make(chan struct{})
+	done := n.expandDone
+	n.expandLock.Unlock()
+
+	// Issue the RPC outside any lock so concurrent readers/waiters are not blocked.
+	parentID := n.object.GetGobjectId()
+	children, err := n.client.browseChildrenInner(ctx, &parentID, n.options)
+
+	if err == nil {
+		n.mu.Lock()
+		n.children = children
+		n.isExpanded = true
+		n.mu.Unlock()
+	}
+
+	// Publish result to waiters and clear the in-flight marker so a failed
+	// expansion can be retried by the next Expand call.
+	n.expandLock.Lock()
+	n.expandErr = err
+	n.expanding = false
+	close(done)
+	n.expandLock.Unlock()
+
+	return err
+}
+
+// Browse returns the root nodes of the Galaxy hierarchy. The returned nodes
+// have only their server-supplied hints populated; call Expand on each node to
+// fetch its direct children. When opts is nil the server defaults apply.
+func (c *GalaxyClient) Browse(ctx context.Context, opts *BrowseChildrenOptions) ([]*LazyBrowseNode, error) {
+	effective := BrowseChildrenOptions{}
+	if opts != nil {
+		effective = *opts
+	}
+	return c.browseChildrenInner(ctx, nil, effective)
+}
+
+// BrowseChildrenRaw issues a single BrowseChildren RPC and returns the raw
+// reply for callers that need direct page-token control. Transport-level
+// failures are wrapped in *GatewayError to match the rest of the client.
+func (c *GalaxyClient) BrowseChildrenRaw(ctx context.Context, req *pb.BrowseChildrenRequest) (*pb.BrowseChildrenReply, error) {
+	callCtx, cancel := c.callContext(ctx)
+	defer cancel()
+	reply, err := c.raw.BrowseChildren(callCtx, req)
+	if err != nil {
+		return nil, &GatewayError{Op: "galaxy browse children", Err: err}
+	}
+	return reply, nil
+}
+
+func (c *GalaxyClient) browseChildrenInner(
+	ctx context.Context,
+	parentGobjectID *int32,
+	opts BrowseChildrenOptions,
+) ([]*LazyBrowseNode, error) {
+	var nodes []*LazyBrowseNode
+	pageToken := ""
+	seen := map[string]struct{}{}
+	for {
+		req := &pb.BrowseChildrenRequest{
+			PageSize:              browseChildrenPageSize,
+			PageToken:             pageToken,
+			CategoryIds:           opts.CategoryIds,
+			TemplateChainContains: opts.TemplateChainContains,
+			TagNameGlob:           opts.TagNameGlob,
+			AlarmBearingOnly:      opts.AlarmBearingOnly,
+			HistorizedOnly:        opts.HistorizedOnly,
+		}
+		if parentGobjectID != nil {
+			req.Parent = &pb.BrowseChildrenRequest_ParentGobjectId{ParentGobjectId: *parentGobjectID}
+		}
+		if opts.IncludeAttributes != nil {
+			req.IncludeAttributes = opts.IncludeAttributes
+		}
+
+		reply, err := c.BrowseChildrenRaw(ctx, req)
+		if err != nil {
+			return nil, err
+		}
+
+		for i, child := range reply.GetChildren() {
+			hasChildren := reply.GetChildHasChildren()
+			hint := i < len(hasChildren) && hasChildren[i]
+			nodes = append(nodes, &LazyBrowseNode{
+				client:          c,
+				object:          child,
+				hasChildrenHint: hint,
+				options:         opts,
+			})
+		}
+
+		pageToken = reply.GetNextPageToken()
+		if pageToken == "" {
+			return nodes, nil
+		}
+		if _, dup := seen[pageToken]; dup {
+			return nil, &GatewayError{
+				Op:  "galaxy browse children",
+				Err: fmt.Errorf("repeated page token %q", pageToken),
+			}
+		}
+		seen[pageToken] = struct{}{}
+	}
+}
+
 func (c *GalaxyClient) callContext(ctx context.Context) (context.Context, context.CancelFunc) {
 	timeout := c.opts.CallTimeout
 	if timeout == 0 {

clients/go/mxgateway/galaxy_test.go

@@ -4,11 +4,14 @@ import (
 	"context"
 	"errors"
 	"net"
+	"sync"
 	"testing"
 	"time"
 
 	pb "gitea.dohertylan.com/dohertj2/mxaccessgw/clients/go/internal/generated"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 	"google.golang.org/grpc/test/bufconn"
 	"google.golang.org/protobuf/types/known/timestamppb"
 )
@@ -144,6 +147,47 @@ func TestGalaxyDiscoverHierarchyReturnsObjects(t *testing.T) {
 	}
 }
 
+func TestGalaxyDiscoverHierarchyPaginatesAcrossMultiplePages(t *testing.T) {
+	page1 := &pb.DiscoverHierarchyReply{
+		Objects: []*pb.GalaxyObject{
+			{GobjectId: 1, TagName: "A"},
+			{GobjectId: 2, TagName: "B"},
+		},
+		NextPageToken:    "page-2",
+		TotalObjectCount: 3,
+	}
+	page2 := &pb.DiscoverHierarchyReply{
+		Objects: []*pb.GalaxyObject{
+			{GobjectId: 3, TagName: "C"},
+		},
+		TotalObjectCount: 3,
+	}
+	fake := &fakeGalaxyServer{
+		discoverHierarchyReplies: []*pb.DiscoverHierarchyReply{page1, page2},
+	}
+	client, cleanup := newGalaxyBufconnClient(t, fake)
+	defer cleanup()
+
+	objs, err := client.DiscoverHierarchy(context.Background())
+	if err != nil {
+		t.Fatalf("DiscoverHierarchy: %v", err)
+	}
+	if got, want := len(objs), 3; got != want {
+		t.Fatalf("len(objs) = %d, want %d", got, want)
+	}
+	if len(fake.discoverHierarchyCalls) != 2 {
+		t.Fatalf("expected 2 RPC calls, got %d", len(fake.discoverHierarchyCalls))
+	}
+	if fake.discoverHierarchyCalls[0].GetPageSize() != discoverHierarchyPageSize {
+		t.Fatalf("first call PageSize = %d, want %d",
+			fake.discoverHierarchyCalls[0].GetPageSize(), discoverHierarchyPageSize)
+	}
+	if fake.discoverHierarchyCalls[1].GetPageToken() != "page-2" {
+		t.Fatalf("second call page token = %q, want %q",
+			fake.discoverHierarchyCalls[1].GetPageToken(), "page-2")
+	}
+}
+
 func TestGalaxyDialReturnsGatewayErrorOnRpcFailure(t *testing.T) {
 	fake := &fakeGalaxyServer{failTest: true}
 	client, cleanup := newGalaxyBufconnClient(t, fake)
@@ -370,15 +414,20 @@ func newGalaxyBufconnClient(t *testing.T, fake *fakeGalaxyServer) (*GalaxyClient
 type fakeGalaxyServer struct {
 	pb.UnimplementedGalaxyRepositoryServer
 
-	testReply         *pb.TestConnectionReply
-	testAuth          string
-	failTest          bool
-	deployReply       *pb.GetLastDeployTimeReply
-	discoverReply     *pb.DiscoverHierarchyReply
-	watchEvents       []*pb.DeployEvent
-	watchRequest      *pb.WatchDeployEventsRequest
-	watchSendInterval time.Duration
-	watchHoldOpen     bool
+	testReply                *pb.TestConnectionReply
+	testAuth                 string
+	failTest                 bool
+	deployReply              *pb.GetLastDeployTimeReply
+	discoverReply            *pb.DiscoverHierarchyReply
+	discoverHierarchyCalls   []*pb.DiscoverHierarchyRequest
+	discoverHierarchyReplies []*pb.DiscoverHierarchyReply
+	watchEvents              []*pb.DeployEvent
+	watchRequest             *pb.WatchDeployEventsRequest
+	watchSendInterval        time.Duration
+	watchHoldOpen            bool
+	browseChildrenCalls      []*pb.BrowseChildrenRequest
+	browseChildrenReplies    []*pb.BrowseChildrenReply
+	browseChildrenError      error
 }
 
 func (s *fakeGalaxyServer) TestConnection(ctx context.Context, req *pb.TestConnectionRequest) (*pb.TestConnectionReply, error) {
@@ -400,6 +449,12 @@ func (s *fakeGalaxyServer) GetLastDeployTime(ctx context.Context, req *pb.GetLas
 }
 
 func (s *fakeGalaxyServer) DiscoverHierarchy(ctx context.Context, req *pb.DiscoverHierarchyRequest) (*pb.DiscoverHierarchyReply, error) {
+	s.discoverHierarchyCalls = append(s.discoverHierarchyCalls, req)
+	if len(s.discoverHierarchyReplies) > 0 {
+		reply := s.discoverHierarchyReplies[0]
+		s.discoverHierarchyReplies = s.discoverHierarchyReplies[1:]
+		return reply, nil
+	}
 	if s.discoverReply != nil {
 		return s.discoverReply, nil
 	}
@@ -425,3 +480,385 @@ func (s *fakeGalaxyServer) WatchDeployEvents(req *pb.WatchDeployEventsRequest, s
 	}
 	return nil
 }
+
+func (s *fakeGalaxyServer) BrowseChildren(ctx context.Context, req *pb.BrowseChildrenRequest) (*pb.BrowseChildrenReply, error) {
+	s.browseChildrenCalls = append(s.browseChildrenCalls, req)
+	if s.browseChildrenError != nil {
+		err := s.browseChildrenError
+		s.browseChildrenError = nil
+		return nil, err
+	}
+	if len(s.browseChildrenReplies) == 0 {
+		return &pb.BrowseChildrenReply{}, nil
+	}
+	reply := s.browseChildrenReplies[0]
+	s.browseChildrenReplies = s.browseChildrenReplies[1:]
+	return reply, nil
+}
+
+func obj(id int32, tag string, isArea bool) *pb.GalaxyObject {
+	return &pb.GalaxyObject{
+		GobjectId:  id,
+		TagName:    tag,
+		BrowseName: tag,
+		IsArea:     isArea,
+	}
+}
+
+func buildBrowseReply(children []*pb.GalaxyObject, hasChildren []bool, seq uint64) *pb.BrowseChildrenReply {
+	return &pb.BrowseChildrenReply{
+		TotalChildCount:  int32(len(children)),
+		CacheSequence:    seq,
+		Children:         children,
+		ChildHasChildren: hasChildren,
+	}
+}
+
+func TestGalaxyBrowseNoParentReturnsRoots(t *testing.T) {
+	fake := &fakeGalaxyServer{
+		browseChildrenReplies: []*pb.BrowseChildrenReply{
+			buildBrowseReply(
+				[]*pb.GalaxyObject{obj(1, "Plant", true), obj(99, "Other", false)},
+				[]bool{true, false},
+				7,
+			),
+		},
+	}
+	client, cleanup := newGalaxyBufconnClient(t, fake)
+	defer cleanup()
+
+	roots, err := client.Browse(context.Background(), nil)
+	if err != nil {
+		t.Fatalf("Browse: %v", err)
+	}
+	if got, want := len(roots), 2; got != want {
+		t.Fatalf("len(roots) = %d, want %d", got, want)
+	}
+	if roots[0].Object().GetTagName() != "Plant" {
+		t.Fatalf("roots[0].TagName = %q", roots[0].Object().GetTagName())
+	}
+	if !roots[0].HasChildrenHint() {
+		t.Fatal("roots[0].HasChildrenHint = false, want true")
+	}
+	if roots[0].IsExpanded() {
+		t.Fatal("roots[0].IsExpanded = true, want false")
+	}
+	if roots[1].HasChildrenHint() {
+		t.Fatal("roots[1].HasChildrenHint = true, want false")
+	}
+	if len(fake.browseChildrenCalls) != 1 {
+		t.Fatalf("BrowseChildren calls = %d, want 1", len(fake.browseChildrenCalls))
+	}
+	if fake.browseChildrenCalls[0].GetParent() != nil {
+		t.Fatalf("root browse should not set Parent oneof, got %T", fake.browseChildrenCalls[0].GetParent())
+	}
+}
+
+func TestGalaxyBrowseExpandPopulatesChildrenAndMarksExpanded(t *testing.T) {
+	fake := &fakeGalaxyServer{
+		browseChildrenReplies: []*pb.BrowseChildrenReply{
+			buildBrowseReply(
+				[]*pb.GalaxyObject{obj(1, "Plant", true)},
+				[]bool{true},
+				1,
+			),
+			buildBrowseReply(
+				[]*pb.GalaxyObject{obj(10, "Area1", true), obj(11, "Tank1", false)},
+				[]bool{true, false},
+				1,
+			),
+		},
+	}
+	client, cleanup := newGalaxyBufconnClient(t, fake)
+	defer cleanup()
+
+	roots, err := client.Browse(context.Background(), nil)
+	if err != nil {
+		t.Fatalf("Browse: %v", err)
+	}
+	if len(roots) != 1 {
+		t.Fatalf("len(roots) = %d, want 1", len(roots))
+	}
+	plant := roots[0]
+	if plant.IsExpanded() {
+		t.Fatal("plant.IsExpanded = true before Expand, want false")
+	}
+	if err := plant.Expand(context.Background()); err != nil {
+		t.Fatalf("Expand: %v", err)
+	}
+	if !plant.IsExpanded() {
+		t.Fatal("plant.IsExpanded = false after Expand, want true")
+	}
+	children := plant.Children()
+	if len(children) != 2 {
+		t.Fatalf("len(children) = %d, want 2", len(children))
+	}
+	if children[0].Object().GetTagName() != "Area1" {
+		t.Fatalf("children[0].TagName = %q, want Area1", children[0].Object().GetTagName())
+	}
+	if !children[0].HasChildrenHint() {
+		t.Fatal("children[0].HasChildrenHint = false, want true")
+	}
+	if children[1].HasChildrenHint() {
+		t.Fatal("children[1].HasChildrenHint = true, want false")
+	}
+	if len(fake.browseChildrenCalls) != 2 {
+		t.Fatalf("BrowseChildren calls = %d, want 2", len(fake.browseChildrenCalls))
+	}
+	parent := fake.browseChildrenCalls[1].GetParent()
+	parentGobj, ok := parent.(*pb.BrowseChildrenRequest_ParentGobjectId)
+	if !ok {
+		t.Fatalf("Parent oneof = %T, want *BrowseChildrenRequest_ParentGobjectId", parent)
+	}
+	if parentGobj.ParentGobjectId != 1 {
+		t.Fatalf("ParentGobjectId = %d, want 1", parentGobj.ParentGobjectId)
+	}
+}
+
+func TestGalaxyBrowseExpandIdempotentNoSecondRpc(t *testing.T) {
+	fake := &fakeGalaxyServer{
+		browseChildrenReplies: []*pb.BrowseChildrenReply{
+			buildBrowseReply(
+				[]*pb.GalaxyObject{obj(1, "Plant", true)},
+				[]bool{true},
+				1,
+			),
+			buildBrowseReply(
+				[]*pb.GalaxyObject{obj(10, "Area1", true)},
+				[]bool{false},
+				1,
+			),
+		},
+	}
+	client, cleanup := newGalaxyBufconnClient(t, fake)
+	defer cleanup()
+
+	roots, err := client.Browse(context.Background(), nil)
+	if err != nil {
+		t.Fatalf("Browse: %v", err)
+	}
+	plant := roots[0]
+	if err := plant.Expand(context.Background()); err != nil {
+		t.Fatalf("Expand #1: %v", err)
+	}
+	callsAfterFirst := len(fake.browseChildrenCalls)
+	if callsAfterFirst != 2 {
+		t.Fatalf("BrowseChildren calls after first Expand = %d, want 2", callsAfterFirst)
+	}
+	if err := plant.Expand(context.Background()); err != nil {
+		t.Fatalf("Expand #2: %v", err)
+	}
+	if got := len(fake.browseChildrenCalls); got != callsAfterFirst {
+		t.Fatalf("BrowseChildren calls after second Expand = %d, want %d (no extra RPC)", got, callsAfterFirst)
+	}
+}
+
+func TestGalaxyBrowseExpandUnknownParentReturnsNotFoundError(t *testing.T) {
+	fake := &fakeGalaxyServer{
+		browseChildrenReplies: []*pb.BrowseChildrenReply{
+			buildBrowseReply(
+				[]*pb.GalaxyObject{obj(1, "Plant", true)},
+				[]bool{true},
+				1,
+			),
+		},
+		browseChildrenError: status.Error(codes.NotFound, "parent not found"),
+	}
+	// The first Browse() consumes the first reply; the next call (Expand) will
+	// then hit browseChildrenError. We need the error to fire only on the second
+	// call, so seed the reply first and let the call sequence consume them in
+	// order. Because BrowseChildren in the fake consumes browseChildrenError
+	// before falling through to replies, swap the strategy: keep the root reply
+	// but have BrowseChildren return the error on the second call. We do this by
+	// emptying the reply list after the first Browse.
+	client, cleanup := newGalaxyBufconnClient(t, fake)
+	defer cleanup()
+
+	// First call returns the error (because browseChildrenError takes precedence).
+	// To avoid that, clear it for the root call by performing a manual setup: we
+	// pre-stage replies first, then set the error after the first call. Easiest:
+	// pre-Browse() with error=nil, then set error before Expand.
+	fake.browseChildrenError = nil
+	roots, err := client.Browse(context.Background(), nil)
+	if err != nil {
+		t.Fatalf("Browse: %v", err)
+	}
+	if len(roots) != 1 {
+		t.Fatalf("len(roots) = %d, want 1", len(roots))
+	}
+	fake.browseChildrenError = status.Error(codes.NotFound, "parent not found")
+
+	err = roots[0].Expand(context.Background())
+	if err == nil {
+		t.Fatal("Expand: error = nil, want NotFound")
+	}
+	if status.Code(err) != codes.NotFound {
+		t.Fatalf("status.Code = %s, want NotFound", status.Code(err))
+	}
+	if roots[0].IsExpanded() {
+		t.Fatal("roots[0].IsExpanded = true after failed Expand, want false")
+	}
+}
+
+func TestGalaxyBrowseExpandMultiPageGathersAllPages(t *testing.T) {
+	firstPage := buildBrowseReply(
+		[]*pb.GalaxyObject{obj(1, "Plant", true)},
+		[]bool{true},
+		7,
+	)
+
+	pageA := buildBrowseReply(
+		[]*pb.GalaxyObject{obj(10, "Child1", false), obj(11, "Child2", false)},
+		[]bool{false, false},
+		7,
+	)
+	pageA.NextPageToken = "7:abc:2"
+	pageB := buildBrowseReply(
+		[]*pb.GalaxyObject{obj(12, "Child3", false)},
+		[]bool{false},
+		7,
+	)
+
+	fake := &fakeGalaxyServer{
+		browseChildrenReplies: []*pb.BrowseChildrenReply{firstPage, pageA, pageB},
+	}
+	client, cleanup := newGalaxyBufconnClient(t, fake)
+	defer cleanup()
+
+	roots, err := client.Browse(context.Background(), nil)
+	if err != nil {
+		t.Fatalf("Browse: %v", err)
+	}
+	if err := roots[0].Expand(context.Background()); err != nil {
+		t.Fatalf("Expand: %v", err)
+	}
+	children := roots[0].Children()
+	if len(children) != 3 {
+		t.Fatalf("len(children) = %d, want 3", len(children))
+	}
+	if len(fake.browseChildrenCalls) != 3 {
+		t.Fatalf("BrowseChildren calls = %d, want 3", len(fake.browseChildrenCalls))
+	}
+	if got := fake.browseChildrenCalls[2].GetPageToken(); got != "7:abc:2" {
+		t.Fatalf("third call PageToken = %q, want %q", got, "7:abc:2")
+	}
+}
+
+func TestGalaxyBrowseWithFilterForwardsToRequest(t *testing.T) {
+	fake := &fakeGalaxyServer{
+		browseChildrenReplies: []*pb.BrowseChildrenReply{
+			buildBrowseReply(nil, nil, 1),
+		},
+	}
+	client, cleanup := newGalaxyBufconnClient(t, fake)
+	defer cleanup()
+
+	include := true
+	opts := &BrowseChildrenOptions{
+		CategoryIds:           []int32{7, 9},
+		TemplateChainContains: []string{"$AppObject"},
+		TagNameGlob:           "Tank*",
+		IncludeAttributes:     &include,
+		AlarmBearingOnly:      true,
+		HistorizedOnly:        true,
+	}
+	if _, err := client.Browse(context.Background(), opts); err != nil {
+		t.Fatalf("Browse: %v", err)
+	}
+	if len(fake.browseChildrenCalls) != 1 {
+		t.Fatalf("BrowseChildren calls = %d, want 1", len(fake.browseChildrenCalls))
+	}
+	got := fake.browseChildrenCalls[0]
+	if want := []int32{7, 9}; len(got.GetCategoryIds()) != 2 || got.GetCategoryIds()[0] != want[0] || got.GetCategoryIds()[1] != want[1] {
+		t.Fatalf("CategoryIds = %v, want %v", got.GetCategoryIds(), want)
+	}
+	if want := []string{"$AppObject"}; len(got.GetTemplateChainContains()) != 1 || got.GetTemplateChainContains()[0] != want[0] {
+		t.Fatalf("TemplateChainContains = %v, want %v", got.GetTemplateChainContains(), want)
+	}
+	if got.GetTagNameGlob() != "Tank*" {
+		t.Fatalf("TagNameGlob = %q, want %q", got.GetTagNameGlob(), "Tank*")
+	}
+	if !got.GetIncludeAttributes() {
+		t.Fatal("IncludeAttributes = false, want true")
+	}
+	if !got.GetAlarmBearingOnly() {
+		t.Fatal("AlarmBearingOnly = false, want true")
+	}
+	if !got.GetHistorizedOnly() {
+		t.Fatal("HistorizedOnly = false, want true")
+	}
+}
+
+func TestGalaxyBrowseExpandConcurrentCallersOnlyFireOneRpc(t *testing.T) {
+	fake := &fakeGalaxyServer{
+		browseChildrenReplies: []*pb.BrowseChildrenReply{
+			// roots
+			buildBrowseReply([]*pb.GalaxyObject{obj(1, "Plant", true)}, []bool{true}, 7),
+			// one expand: one child
+			buildBrowseReply([]*pb.GalaxyObject{obj(2, "Mixer", false)}, []bool{false}, 7),
+		},
+	}
+	client, cleanup := newGalaxyBufconnClient(t, fake)
+	defer cleanup()
+
+	ctx := context.Background()
+	roots, err := client.Browse(ctx, nil)
+	if err != nil {
+		t.Fatalf("Browse: %v", err)
+	}
+
+	var wg sync.WaitGroup
+	errs := make(chan error, 10)
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			errs <- roots[0].Expand(ctx)
+		}()
+	}
+	wg.Wait()
+	close(errs)
+	for err := range errs {
+		if err != nil {
+			t.Fatalf("concurrent Expand: %v", err)
+		}
+	}
+
+	if !roots[0].IsExpanded() {
+		t.Fatal("IsExpanded() = false after 10 concurrent expands")
+	}
+	if got, want := len(roots[0].Children()), 1; got != want {
+		t.Fatalf("len(children) = %d, want %d", got, want)
+	}
+	// 1 roots fetch + exactly 1 expand fetch.
+	if got, want := len(fake.browseChildrenCalls), 2; got != want {
+		t.Fatalf("RPC count = %d, want %d", got, want)
+	}
+}
+
+func TestGalaxyBrowseChildrenRejectsRepeatedPageToken(t *testing.T) {
+	// Build a reply that carries a non-empty NextPageToken so browseChildrenInner
+	// will request a second page. Queue the same reply twice so the second response
+	// returns the same page token, triggering the duplicate-token guard.
+	page := buildBrowseReply(
+		[]*pb.GalaxyObject{obj(1, "Plant", true)},
+		[]bool{true},
+		1,
+	)
+	page.NextPageToken = "1:abc:1"
+
+	fake := &fakeGalaxyServer{
+		browseChildrenReplies: []*pb.BrowseChildrenReply{page, page},
+	}
+	client, cleanup := newGalaxyBufconnClient(t, fake)
+	defer cleanup()
+
+	_, err := client.Browse(context.Background(), nil)
+	if err == nil {
+		t.Fatal("Browse: error = nil, want repeated-page-token error")
+	}
+	var gwErr *GatewayError
+	if !errors.As(err, &gwErr) {
+		t.Fatalf("error type = %T, want *GatewayError; err = %v", err, err)
+	}
+}

clients/go/mxgateway/options.go

@@ -34,6 +34,32 @@ type Options struct {
 	TransportCredentials credentials.TransportCredentials
 	// DialOptions are appended to the gRPC dial options after the defaults.
 	DialOptions []grpc.DialOption
+	// RequireCertificateValidation forces TLS certificate verification even when
+	// no CACertFile is pinned. Default false: the gateway's self-signed cert is
+	// accepted without verification (internal-tool posture).
+	RequireCertificateValidation bool
+}
+
+// BrowseChildrenOptions configures lazy Galaxy hierarchy walks performed by
+// (*GalaxyClient).Browse and (*LazyBrowseNode).Expand. All fields are optional;
+// the zero value matches the dashboard default (no filters, all attributes per
+// the server default).
+type BrowseChildrenOptions struct {
+	// CategoryIds restricts results to the listed Galaxy category ids when set.
+	CategoryIds []int32
+	// TemplateChainContains restricts results to objects whose template chain
+	// contains any of the listed template tag names.
+	TemplateChainContains []string
+	// TagNameGlob restricts results to objects whose tag name matches the glob
+	// pattern when non-empty.
+	TagNameGlob string
+	// IncludeAttributes overrides the server default for attribute inclusion when
+	// non-nil. The pointer form mirrors the proto's optional field.
+	IncludeAttributes *bool
+	// AlarmBearingOnly limits results to alarm-bearing objects when true.
+	AlarmBearingOnly bool
+	// HistorizedOnly limits results to historized objects when true.
+	HistorizedOnly bool
 }
 
 // RedactedAPIKey returns a display-safe representation of the configured API

clients/go/mxgateway/session.go

@@ -392,6 +392,9 @@ func (s *Session) UnsubscribeBulk(ctx context.Context, serverHandle int32, itemH
 // Per-entry failures appear as BulkWriteResult entries with WasSuccessful=false; the call
 // never returns an error for per-entry MXAccess failures (it returns an error only for
 // protocol-level failures or transport errors).
+//
+// A non-nil but empty entries slice is treated as a no-op and returns an empty result
+// without a wire round-trip; pass nil to surface a clear "entries are required" error.
 func (s *Session) WriteBulk(ctx context.Context, serverHandle int32, entries []*WriteBulkEntry) ([]*BulkWriteResult, error) {
 	if entries == nil {
 		return nil, errors.New("mxgateway: write bulk entries are required")
@@ -399,6 +402,9 @@ func (s *Session) WriteBulk(ctx context.Context, serverHandle int32, entries []*
 	if err := ensureBulkSize("write bulk entries", len(entries)); err != nil {
 		return nil, err
 	}
+	if len(entries) == 0 {
+		return []*BulkWriteResult{}, nil
+	}
 	reply, err := s.invokeCommand(ctx, &pb.MxCommand{
 		Kind: pb.MxCommandKind_MX_COMMAND_KIND_WRITE_BULK,
 		Payload: &pb.MxCommand_WriteBulk{
@@ -415,6 +421,9 @@ func (s *Session) WriteBulk(ctx context.Context, serverHandle int32, entries []*
 }
 
 // Write2Bulk invokes MXAccess Write2 (timestamped) for each entry inside one gateway command.
+//
+// A non-nil but empty entries slice is treated as a no-op and returns an empty result
+// without a wire round-trip; pass nil to surface a clear "entries are required" error.
 func (s *Session) Write2Bulk(ctx context.Context, serverHandle int32, entries []*Write2BulkEntry) ([]*BulkWriteResult, error) {
 	if entries == nil {
 		return nil, errors.New("mxgateway: write2 bulk entries are required")
@@ -422,6 +431,9 @@ func (s *Session) Write2Bulk(ctx context.Context, serverHandle int32, entries []
 	if err := ensureBulkSize("write2 bulk entries", len(entries)); err != nil {
 		return nil, err
 	}
+	if len(entries) == 0 {
+		return []*BulkWriteResult{}, nil
+	}
 	reply, err := s.invokeCommand(ctx, &pb.MxCommand{
 		Kind: pb.MxCommandKind_MX_COMMAND_KIND_WRITE2_BULK,
 		Payload: &pb.MxCommand_Write2Bulk{
@@ -439,6 +451,9 @@ func (s *Session) Write2Bulk(ctx context.Context, serverHandle int32, entries []
 
 // WriteSecuredBulk invokes MXAccess WriteSecured for each entry. Credential-sensitive
 // values must not be logged by callers; mirrors the single-item WriteSecured contract.
+//
+// A non-nil but empty entries slice is treated as a no-op and returns an empty result
+// without a wire round-trip; pass nil to surface a clear "entries are required" error.
 func (s *Session) WriteSecuredBulk(ctx context.Context, serverHandle int32, entries []*WriteSecuredBulkEntry) ([]*BulkWriteResult, error) {
 	if entries == nil {
 		return nil, errors.New("mxgateway: write-secured bulk entries are required")
@@ -446,6 +461,9 @@ func (s *Session) WriteSecuredBulk(ctx context.Context, serverHandle int32, entr
 	if err := ensureBulkSize("write-secured bulk entries", len(entries)); err != nil {
 		return nil, err
 	}
+	if len(entries) == 0 {
+		return []*BulkWriteResult{}, nil
+	}
 	reply, err := s.invokeCommand(ctx, &pb.MxCommand{
 		Kind: pb.MxCommandKind_MX_COMMAND_KIND_WRITE_SECURED_BULK,
 		Payload: &pb.MxCommand_WriteSecuredBulk{
@@ -462,6 +480,9 @@ func (s *Session) WriteSecuredBulk(ctx context.Context, serverHandle int32, entr
 }
 
 // WriteSecured2Bulk invokes MXAccess WriteSecured2 (timestamped) for each entry.
+//
+// A non-nil but empty entries slice is treated as a no-op and returns an empty result
+// without a wire round-trip; pass nil to surface a clear "entries are required" error.
 func (s *Session) WriteSecured2Bulk(ctx context.Context, serverHandle int32, entries []*WriteSecured2BulkEntry) ([]*BulkWriteResult, error) {
 	if entries == nil {
 		return nil, errors.New("mxgateway: write-secured2 bulk entries are required")
@@ -469,6 +490,9 @@ func (s *Session) WriteSecured2Bulk(ctx context.Context, serverHandle int32, ent
 	if err := ensureBulkSize("write-secured2 bulk entries", len(entries)); err != nil {
 		return nil, err
 	}
+	if len(entries) == 0 {
+		return []*BulkWriteResult{}, nil
+	}
 	reply, err := s.invokeCommand(ctx, &pb.MxCommand{
 		Kind: pb.MxCommandKind_MX_COMMAND_KIND_WRITE_SECURED2_BULK,
 		Payload: &pb.MxCommand_WriteSecured2Bulk{
@@ -492,6 +516,10 @@ func (s *Session) WriteSecured2Bulk(ctx context.Context, serverHandle int32, ent
 // otherwise. timeout bounds the wait per tag in the snapshot case; pass zero to use the
 // worker default. Per-tag failures (timeout, invalid tag) appear as BulkReadResult entries
 // with WasSuccessful=false; the call never returns an error for per-tag MXAccess failures.
+//
+// A non-nil but empty tagAddresses slice is treated as a no-op and returns an empty
+// result without a wire round-trip; pass nil to surface a clear "tag addresses are
+// required" error.
 func (s *Session) ReadBulk(ctx context.Context, serverHandle int32, tagAddresses []string, timeout time.Duration) ([]*BulkReadResult, error) {
 	if tagAddresses == nil {
 		return nil, errors.New("mxgateway: tag addresses are required")
@@ -499,6 +527,9 @@ func (s *Session) ReadBulk(ctx context.Context, serverHandle int32, tagAddresses
 	if err := ensureBulkSize("tag addresses", len(tagAddresses)); err != nil {
 		return nil, err
 	}
+	if len(tagAddresses) == 0 {
+		return []*BulkReadResult{}, nil
+	}
 	var timeoutMs uint32
 	if timeout > 0 {
 		ms := timeout.Milliseconds()

clients/java/JavaClientDesign.md

@@ -112,6 +112,23 @@ Support:
 - custom CA certificate file,
 - server name override for test environments.
 
+### Trust posture
+
+The gateway can serve a self-signed certificate it generates itself (it has no
+PKI). To make that usable, TLS is **lenient by default**: when the channel is not
+plaintext and no `caCertificatePath` is set, the client builds
+`GrpcSslContexts.forClient().trustManager(InsecureTrustManagerFactory.INSTANCE)`
+(grpc-netty-shaded), so the gateway's self-signed certificate is accepted without
+verification.
+
+To verify the gateway instead:
+
+- set `caCertificatePath` to pin a CA (full verification against that root), or
+- set `requireCertificateValidation` to `true` to verify against the JVM trust
+  store without pinning.
+
+Pinning a CA always wins over the lenient default.
+
 ## Streaming
 
 Support both:

clients/java/README.md

@@ -57,6 +57,16 @@ try (MxGatewayClient client = MxGatewayClient.connect(options);
 }
 ```
 
+The gateway can auto-generate its own self-signed certificate (it has no PKI), so
+the client is **lenient by default**: a TLS connection (`plaintext(false)`) with
+no `caCertificatePath` accepts whatever certificate the gateway presents (via
+grpc-netty-shaded's `InsecureTrustManagerFactory`). To verify instead, set
+`caCertificatePath` to pin a CA, or set `requireCertificateValidation(true)` to
+verify against the JVM trust store without pinning. Use `serverNameOverride` /
+`--server-name-override` when the dialed host differs from the certificate SAN.
+See
+[Gateway Configuration](../../docs/GatewayConfiguration.md#automatic-self-signed-certificate).
+
 Use `rawBlockingStub`, `rawFutureStub`, `rawAsyncStub`, `openSessionRaw`,
 `closeSessionRaw`, `invoke`, and raw session helper methods when tests need the
 underlying protobuf messages. `MxGatewayCommandException` and
@@ -116,6 +126,59 @@ gradle :zb-mom-ww-mxgateway-cli:run --args="galaxy-deploy-time --endpoint localh
 gradle :zb-mom-ww-mxgateway-cli:run --args="galaxy-discover --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --json"
 ```
 
+### Browsing lazily
+
+For UI trees or OPC UA bridges, use `browseChildren` to walk one level at a
+time instead of loading the full hierarchy with `discoverHierarchy`. Pass a
+default request for root objects; subsequent calls set `parentGobjectId`,
+`parentTagName`, or `parentContainedPath`. Filter fields match
+`DiscoverHierarchy`. Each response pairs `getChildrenList()` with
+`getChildHasChildrenList()` so you know which nodes to expand. See
+[Galaxy Repository](../../docs/GalaxyRepository.md#browsechildren) for full
+request and filter semantics. This snippet documents the API as it appears once
+the Java client is regenerated on the Windows host.
+
+```java
+BrowseChildrenReply reply = galaxy.browseChildren(
+        BrowseChildrenRequest.newBuilder().build());
+
+List<GalaxyObject> children = reply.getChildrenList();
+List<Boolean> hasChildren = reply.getChildHasChildrenList();
+for (int i = 0; i < children.size(); i++) {
+    System.out.printf("%s expand=%b%n", children.get(i).getTagName(), hasChildren.get(i));
+}
+```
+
+#### High-level walker
+
+For UI trees, the client provides a `LazyBrowseNode` walker that handles
+sibling pagination and the `child_has_children` hint for you:
+
+```java
+MxGatewayClientOptions options = MxGatewayClientOptions.builder()
+        .endpoint("localhost:5000")
+        .apiKey(System.getenv("MXGATEWAY_API_KEY"))
+        .plaintext(true)
+        .build();
+
+try (GalaxyRepositoryClient galaxy = GalaxyRepositoryClient.connect(options)) {
+    List<LazyBrowseNode> roots = galaxy.browse();
+    for (LazyBrowseNode root : roots) {
+        if (root.hasChildrenHint()) {
+            root.expand();
+        }
+        for (LazyBrowseNode child : root.getChildren()) {
+            String kind = child.hasChildrenHint() ? "has children" : "leaf";
+            System.out.println(child.getObject().getTagName() + " (" + kind + ")");
+        }
+    }
+}
+```
+
+`expand` is idempotent — calling it twice fires only one RPC,
+and is safe under concurrent callers. To refresh after a Galaxy redeploy, call
+`browse` again from the root.
+
 ### Watching deploy events
 
 `GalaxyRepository.WatchDeployEvents` is a server-streaming RPC: the gateway
@@ -179,8 +242,8 @@ gradle :zb-mom-ww-mxgateway-cli:run --args="add-item --endpoint localhost:5000 -
 gradle :zb-mom-ww-mxgateway-cli:run --args="advise --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --session-id <id> --server-handle 1 --item-handle 1 --json"
 gradle :zb-mom-ww-mxgateway-cli:run --args="write --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --session-id <id> --server-handle 1 --item-handle 1 --type int32 --value 123 --json"
 gradle :zb-mom-ww-mxgateway-cli:run --args="stream-events --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --session-id <id> --limit 1 --json"
-gradle :zb-mom-ww-mxgateway-cli:run --args="stream-alarms --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --session-id <id> --limit 1 --json"
-gradle :zb-mom-ww-mxgateway-cli:run --args="acknowledge-alarm --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --session-id <id> --alarm-reference \"\\Galaxy\Area001.Pump001.PumpFault\" --json"
+gradle :zb-mom-ww-mxgateway-cli:run --args="stream-alarms --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --filter-prefix Galaxy --limit 1 --json"
+gradle :zb-mom-ww-mxgateway-cli:run --args="acknowledge-alarm --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --reference \"\\Galaxy\Area001.Pump001.PumpFault\" --json"
 gradle :zb-mom-ww-mxgateway-cli:run --args="smoke --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --item TestObject.TestInt --json"
 ```
 
@@ -229,6 +292,37 @@ $env:MXGATEWAY_TEST_ITEM = 'TestObject.TestInt'
 gradle :zb-mom-ww-mxgateway-cli:run --args="smoke --endpoint $env:MXGATEWAY_ENDPOINT --plaintext --api-key-env MXGATEWAY_API_KEY --item $env:MXGATEWAY_TEST_ITEM --json"
 ```
 
+## Installing from the Gitea Maven repository
+
+The client publishes to the internal Gitea Maven repository at
+`https://gitea.dohertylan.com/api/packages/dohertj2/maven`.
+
+In your consumer project's `build.gradle`:
+
+````groovy
+repositories {
+    maven {
+        url 'https://gitea.dohertylan.com/api/packages/dohertj2/maven'
+        credentials {
+            username = System.getenv('GITEA_USERNAME')
+            password = System.getenv('GITEA_TOKEN')
+        }
+    }
+}
+
+dependencies {
+    implementation 'com.zb.mom.ww.mxgateway:zb-mom-ww-mxgateway-client:0.1.0'
+}
+````
+
+To publish a new version from this repo:
+
+````bash
+export GITEA_USERNAME=dohertj2
+export GITEA_TOKEN=<your-gitea-token>
+gradle :zb-mom-ww-mxgateway-client:publish
+````
+
 ## Related Documentation
 
 - [Client Packaging](../../docs/ClientPackaging.md)

clients/java/build.gradle

@@ -37,4 +37,44 @@ subprojects {
             testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
         }
     }
+
+    pluginManager.withPlugin('maven-publish') {
+        publishing {
+            publications {
+                maven(MavenPublication) {
+                    from components.java
+                    pom {
+                        url = 'https://gitea.dohertylan.com/dohertj2/mxaccessgw'
+                        description = 'MxAccessGateway Java client'
+                        scm {
+                            url = 'https://gitea.dohertylan.com/dohertj2/mxaccessgw'
+                            connection = 'scm:git:https://gitea.dohertylan.com/dohertj2/mxaccessgw.git'
+                        }
+                        developers {
+                            developer {
+                                id = 'dohertj2'
+                                name = 'Joseph Doherty'
+                            }
+                        }
+                        licenses {
+                            license {
+                                name = 'Proprietary'
+                                distribution = 'repo'
+                            }
+                        }
+                    }
+                }
+            }
+            repositories {
+                maven {
+                    name = 'GiteaPackages'
+                    url = 'https://gitea.dohertylan.com/api/packages/dohertj2/maven'
+                    credentials {
+                        username = System.getenv('GITEA_USERNAME') ?: ''
+                        password = System.getenv('GITEA_TOKEN') ?: ''
+                    }
+                }
+            }
+        }
+    }
 }

clients/java/settings.gradle

@@ -9,6 +9,10 @@ pluginManagement {
     }
 }
 
+plugins {
+    id 'org.gradle.toolchains.foojay-resolver-convention' version '1.0.0'
+}
+
 dependencyResolutionManagement {
     repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
     repositories {

clients/java/src/main/generated/main/grpc/galaxy_repository/v1/GalaxyRepositoryGrpc.java

@@ -142,6 +142,37 @@ public final class GalaxyRepositoryGrpc {
     return getWatchDeployEventsMethod;
   }
 
+  private static volatile io.grpc.MethodDescriptor<galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest,
+      galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply> getBrowseChildrenMethod;
+
+  @io.grpc.stub.annotations.RpcMethod(
+      fullMethodName = SERVICE_NAME + '/' + "BrowseChildren",
+      requestType = galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest.class,
+      responseType = galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply.class,
+      methodType = io.grpc.MethodDescriptor.MethodType.UNARY)
+  public static io.grpc.MethodDescriptor<galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest,
+      galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply> getBrowseChildrenMethod() {
+    io.grpc.MethodDescriptor<galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest, galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply> getBrowseChildrenMethod;
+    if ((getBrowseChildrenMethod = GalaxyRepositoryGrpc.getBrowseChildrenMethod) == null) {
+      synchronized (GalaxyRepositoryGrpc.class) {
+        if ((getBrowseChildrenMethod = GalaxyRepositoryGrpc.getBrowseChildrenMethod) == null) {
+          GalaxyRepositoryGrpc.getBrowseChildrenMethod = getBrowseChildrenMethod =
+              io.grpc.MethodDescriptor.<galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest, galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply>newBuilder()
+              .setType(io.grpc.MethodDescriptor.MethodType.UNARY)
+              .setFullMethodName(generateFullMethodName(SERVICE_NAME, "BrowseChildren"))
+              .setSampledToLocalTracing(true)
+              .setRequestMarshaller(io.grpc.protobuf.ProtoUtils.marshaller(
+                  galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest.getDefaultInstance()))
+              .setResponseMarshaller(io.grpc.protobuf.ProtoUtils.marshaller(
+                  galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply.getDefaultInstance()))
+              .setSchemaDescriptor(new GalaxyRepositoryMethodDescriptorSupplier("BrowseChildren"))
+              .build();
+        }
+      }
+    }
+    return getBrowseChildrenMethod;
+  }
+
   /**
    * Creates a new async stub that supports all call types for the service
    */
@@ -246,6 +277,19 @@ public final class GalaxyRepositoryGrpc {
         io.grpc.stub.StreamObserver<galaxy_repository.v1.GalaxyRepositoryOuterClass.DeployEvent> responseObserver) {
       io.grpc.stub.ServerCalls.asyncUnimplementedUnaryCall(getWatchDeployEventsMethod(), responseObserver);
     }
+
+    /**
+     * <pre>
+     * Returns the direct children of a parent object (or the root objects when
+     * `parent` is unset). Designed for OPC UA-style lazy expand: clients walk
+     * one level at a time instead of paging the full hierarchy. Filters mirror
+     * DiscoverHierarchy exactly. Backed by the same shared hierarchy cache.
+     * </pre>
+     */
+    default void browseChildren(galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest request,
+        io.grpc.stub.StreamObserver<galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply> responseObserver) {
+      io.grpc.stub.ServerCalls.asyncUnimplementedUnaryCall(getBrowseChildrenMethod(), responseObserver);
+    }
   }
 
   /**
@@ -326,6 +370,20 @@ public final class GalaxyRepositoryGrpc {
       io.grpc.stub.ClientCalls.asyncServerStreamingCall(
           getChannel().newCall(getWatchDeployEventsMethod(), getCallOptions()), request, responseObserver);
     }
+
+    /**
+     * <pre>
+     * Returns the direct children of a parent object (or the root objects when
+     * `parent` is unset). Designed for OPC UA-style lazy expand: clients walk
+     * one level at a time instead of paging the full hierarchy. Filters mirror
+     * DiscoverHierarchy exactly. Backed by the same shared hierarchy cache.
+     * </pre>
+     */
+    public void browseChildren(galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest request,
+        io.grpc.stub.StreamObserver<galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply> responseObserver) {
+      io.grpc.stub.ClientCalls.asyncUnaryCall(
+          getChannel().newCall(getBrowseChildrenMethod(), getCallOptions()), request, responseObserver);
+    }
   }
 
   /**
@@ -387,6 +445,19 @@ public final class GalaxyRepositoryGrpc {
       return io.grpc.stub.ClientCalls.blockingV2ServerStreamingCall(
           getChannel(), getWatchDeployEventsMethod(), getCallOptions(), request);
     }
+
+    /**
+     * <pre>
+     * Returns the direct children of a parent object (or the root objects when
+     * `parent` is unset). Designed for OPC UA-style lazy expand: clients walk
+     * one level at a time instead of paging the full hierarchy. Filters mirror
+     * DiscoverHierarchy exactly. Backed by the same shared hierarchy cache.
+     * </pre>
+     */
+    public galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply browseChildren(galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest request) throws io.grpc.StatusException {
+      return io.grpc.stub.ClientCalls.blockingV2UnaryCall(
+          getChannel(), getBrowseChildrenMethod(), getCallOptions(), request);
+    }
   }
 
   /**
@@ -447,6 +518,19 @@ public final class GalaxyRepositoryGrpc {
       return io.grpc.stub.ClientCalls.blockingServerStreamingCall(
           getChannel(), getWatchDeployEventsMethod(), getCallOptions(), request);
     }
+
+    /**
+     * <pre>
+     * Returns the direct children of a parent object (or the root objects when
+     * `parent` is unset). Designed for OPC UA-style lazy expand: clients walk
+     * one level at a time instead of paging the full hierarchy. Filters mirror
+     * DiscoverHierarchy exactly. Backed by the same shared hierarchy cache.
+     * </pre>
+     */
+    public galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply browseChildren(galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest request) {
+      return io.grpc.stub.ClientCalls.blockingUnaryCall(
+          getChannel(), getBrowseChildrenMethod(), getCallOptions(), request);
+    }
   }
 
   /**
@@ -494,12 +578,27 @@ public final class GalaxyRepositoryGrpc {
       return io.grpc.stub.ClientCalls.futureUnaryCall(
           getChannel().newCall(getDiscoverHierarchyMethod(), getCallOptions()), request);
     }
+
+    /**
+     * <pre>
+     * Returns the direct children of a parent object (or the root objects when
+     * `parent` is unset). Designed for OPC UA-style lazy expand: clients walk
+     * one level at a time instead of paging the full hierarchy. Filters mirror
+     * DiscoverHierarchy exactly. Backed by the same shared hierarchy cache.
+     * </pre>
+     */
+    public com.google.common.util.concurrent.ListenableFuture<galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply> browseChildren(
+        galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest request) {
+      return io.grpc.stub.ClientCalls.futureUnaryCall(
+          getChannel().newCall(getBrowseChildrenMethod(), getCallOptions()), request);
+    }
   }
 
   private static final int METHODID_TEST_CONNECTION = 0;
   private static final int METHODID_GET_LAST_DEPLOY_TIME = 1;
   private static final int METHODID_DISCOVER_HIERARCHY = 2;
   private static final int METHODID_WATCH_DEPLOY_EVENTS = 3;
+  private static final int METHODID_BROWSE_CHILDREN = 4;
 
   private static final class MethodHandlers<Req, Resp> implements
       io.grpc.stub.ServerCalls.UnaryMethod<Req, Resp>,
@@ -534,6 +633,10 @@ public final class GalaxyRepositoryGrpc {
           serviceImpl.watchDeployEvents((galaxy_repository.v1.GalaxyRepositoryOuterClass.WatchDeployEventsRequest) request,
               (io.grpc.stub.StreamObserver<galaxy_repository.v1.GalaxyRepositoryOuterClass.DeployEvent>) responseObserver);
           break;
+        case METHODID_BROWSE_CHILDREN:
+          serviceImpl.browseChildren((galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest) request,
+              (io.grpc.stub.StreamObserver<galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply>) responseObserver);
+          break;
         default:
           throw new AssertionError();
       }
@@ -580,6 +683,13 @@ public final class GalaxyRepositoryGrpc {
               galaxy_repository.v1.GalaxyRepositoryOuterClass.WatchDeployEventsRequest,
               galaxy_repository.v1.GalaxyRepositoryOuterClass.DeployEvent>(
                 service, METHODID_WATCH_DEPLOY_EVENTS)))
+        .addMethod(
+          getBrowseChildrenMethod(),
+          io.grpc.stub.ServerCalls.asyncUnaryCall(
+            new MethodHandlers<
+              galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest,
+              galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply>(
+                service, METHODID_BROWSE_CHILDREN)))
         .build();
   }
 
@@ -632,6 +742,7 @@ public final class GalaxyRepositoryGrpc {
               .addMethod(getGetLastDeployTimeMethod())
               .addMethod(getDiscoverHierarchyMethod())
               .addMethod(getWatchDeployEventsMethod())
+              .addMethod(getBrowseChildrenMethod())
               .build();
         }
       }

clients/java/zb-mom-ww-mxgateway-cli/src/main/java/com/zb/mom/ww/mxgateway/cli/MxGatewayCli.java

@@ -33,6 +33,7 @@ import java.util.Optional;
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.Callable;
+import java.util.concurrent.atomic.AtomicReference;
 import mxaccess_gateway.v1.MxaccessGateway.AcknowledgeAlarmReply;
 import mxaccess_gateway.v1.MxaccessGateway.AcknowledgeAlarmRequest;
 import mxaccess_gateway.v1.MxaccessGateway.ActiveAlarmSnapshot;
@@ -119,7 +120,7 @@ public final class MxGatewayCli implements Callable<Integer> {
         return 0;
     }
 
-    private static CommandLine commandLine(MxGatewayCliClientFactory clientFactory) {
+    static CommandLine commandLine(MxGatewayCliClientFactory clientFactory) {
         CommandLine commandLine = new CommandLine(new MxGatewayCli(clientFactory));
         commandLine.addSubcommand("version", new VersionCommand());
         commandLine.addSubcommand("open-session", new OpenSessionCommand(clientFactory));
@@ -154,6 +155,120 @@ public final class MxGatewayCli implements Callable<Integer> {
     /** Sentinel queued by {@code stream-alarms} to mark a clean end of the alarm feed. */
     private static final Object ALARM_FEED_END = new Object();
 
+    /**
+     * Tokenises a single batch-mode stdin line into the argv that the inner
+     * {@link CommandLine} should execute. Honours single-quoted, double-quoted,
+     * and backslash-escaped runs so values that contain spaces (e.g.
+     * {@code --comment "needs verification"}) survive intact — the old
+     * implementation used {@code split("\\s+")} which shredded any quoted
+     * argument mid-string (Client.Java-034).
+     *
+     * <p>Rules (a small POSIX-like shell tokenizer; no variable expansion,
+     * command substitution, globbing, or backtick handling):
+     *
+     * <ul>
+     *   <li>Outside quotes, runs of whitespace separate tokens.</li>
+     *   <li>{@code "..."} groups a sequence into one token; the surrounding
+     *       quotes are removed. Inside double quotes a backslash escapes
+     *       {@code \\}, {@code "}, and a literal newline; other characters
+     *       are taken literally (so {@code \n} is the two characters
+     *       backslash-n).</li>
+     *   <li>{@code '...'} groups a sequence into one token; the surrounding
+     *       quotes are removed. Inside single quotes nothing is escaped —
+     *       the run is literal until the matching single quote.</li>
+     *   <li>Outside quotes, backslash escapes the next character (including
+     *       whitespace, so {@code needs\ verification} is one token).</li>
+     *   <li>An unterminated quote or a trailing backslash throws
+     *       {@link IllegalArgumentException} so the batch loop surfaces it
+     *       as a JSON error instead of silently emitting wrong args.</li>
+     * </ul>
+     *
+     * <p>Empty input (or input that contains only whitespace) returns an
+     * empty array so callers can skip the line.
+     */
+    static String[] tokenizeBatchLine(String line) {
+        List<String> tokens = new ArrayList<>();
+        StringBuilder current = new StringBuilder();
+        boolean inToken = false;
+        // 0 = outside, 1 = inside single quotes, 2 = inside double quotes
+        int quoteMode = 0;
+        int length = line.length();
+        for (int i = 0; i < length; i++) {
+            char c = line.charAt(i);
+            if (quoteMode == 1) {
+                if (c == '\'') {
+                    quoteMode = 0;
+                } else {
+                    current.append(c);
+                }
+                continue;
+            }
+            if (quoteMode == 2) {
+                if (c == '\\') {
+                    if (i + 1 >= length) {
+                        throw new IllegalArgumentException(
+                                "batch tokenizer: trailing backslash inside double-quoted string");
+                    }
+                    char next = line.charAt(i + 1);
+                    if (next == '\\' || next == '"' || next == '\n') {
+                        current.append(next);
+                        i++;
+                    } else {
+                        // POSIX rule: inside double quotes a backslash is
+                        // literal unless it precedes \, ", $, `, or newline.
+                        current.append(c);
+                    }
+                    continue;
+                }
+                if (c == '"') {
+                    quoteMode = 0;
+                    continue;
+                }
+                current.append(c);
+                continue;
+            }
+            // Outside any quotes.
+            if (c == '\'') {
+                quoteMode = 1;
+                inToken = true;
+                continue;
+            }
+            if (c == '"') {
+                quoteMode = 2;
+                inToken = true;
+                continue;
+            }
+            if (c == '\\') {
+                if (i + 1 >= length) {
+                    throw new IllegalArgumentException(
+                            "batch tokenizer: trailing backslash outside quotes");
+                }
+                current.append(line.charAt(i + 1));
+                i++;
+                inToken = true;
+                continue;
+            }
+            if (Character.isWhitespace(c)) {
+                if (inToken) {
+                    tokens.add(current.toString());
+                    current.setLength(0);
+                    inToken = false;
+                }
+                continue;
+            }
+            current.append(c);
+            inToken = true;
+        }
+        if (quoteMode != 0) {
+            throw new IllegalArgumentException(
+                    "batch tokenizer: unterminated " + (quoteMode == 1 ? "single" : "double") + " quote");
+        }
+        if (inToken) {
+            tokens.add(current.toString());
+        }
+        return tokens.toArray(new String[0]);
+    }
+
     /**
      * Reads one CLI invocation per stdin line, executes each via a fresh
      * {@link CommandLine}, and writes {@value #BATCH_EOR} to stdout after
@@ -183,8 +298,8 @@ public final class MxGatewayCli implements Callable<Integer> {
                     if (line.isEmpty()) {
                         break;
                     }
-                    String[] args = line.trim().split("\\s+");
-                    if (args.length == 0 || (args.length == 1 && args[0].isEmpty())) {
+                    String[] args = tokenizeBatchLine(line);
+                    if (args.length == 0) {
                         continue;
                     }
                     StringWriter cmdOut = new StringWriter();
@@ -1079,11 +1194,29 @@ public final class MxGatewayCli implements Callable<Integer> {
                 StreamAlarmsRequest request = StreamAlarmsRequest.newBuilder()
                         .setAlarmFilterPrefix(filterPrefix)
                         .build();
+                // Client.Java-033 — fail-fast on overflow. A bare
+                // queue.offer(value) silently drops messages past capacity,
+                // which violates the JavaStyleGuide "do not drop events"
+                // contract and lets the CLI exit 0 on a truncated feed.
+                // Mirrors MxEventStream's overflow branch: detect a failed
+                // offer, cancel the subscription, drain the buffer, then
+                // queue an explicit overflow exception followed by the END
+                // sentinel so the drain loop surfaces a non-zero exit.
+                AtomicReference<MxGatewayAlarmFeedSubscription> subscriptionRef = new AtomicReference<>();
                 MxGatewayAlarmFeedSubscription subscription =
                         client.streamAlarms(request, new StreamObserver<>() {
                             @Override
                             public void onNext(AlarmFeedMessage value) {
-                                queue.offer(value);
+                                if (!queue.offer(value)) {
+                                    MxGatewayAlarmFeedSubscription sub = subscriptionRef.get();
+                                    if (sub != null) {
+                                        sub.cancel();
+                                    }
+                                    queue.clear();
+                                    queue.offer(new IllegalStateException(
+                                            "stream-alarms queue overflowed (capacity 1024); consumer too slow"));
+                                    queue.offer(ALARM_FEED_END);
+                                }
                             }
 
                             @Override
@@ -1096,6 +1229,7 @@ public final class MxGatewayCli implements Callable<Integer> {
                                 queue.offer(ALARM_FEED_END);
                             }
                         });
+                subscriptionRef.set(subscription);
                 try {
                     int count = 0;
                     while (true) {

clients/java/zb-mom-ww-mxgateway-cli/src/test/java/com/zb/mom/ww/mxgateway/cli/MxGatewayCliTests.java

@@ -225,6 +225,89 @@ final class MxGatewayCliTests {
         assertTrue(run.errors().contains("--reference"), run.errors());
     }
 
+    @Test
+    void readmeDocumentedStreamAlarmsExampleParsesCleanly() {
+        // Client.Java-032 regression — the README's stream-alarms example
+        // (clients/java/README.md:182) must round-trip through picocli's
+        // parser without a parse error. Before the fix, the example used
+        // a non-existent --session-id option and picocli failed at parse
+        // time. This test pins the exact tokens documented in the README.
+        String[] args = {
+                "stream-alarms",
+                "--endpoint",
+                "localhost:5000",
+                "--api-key-env",
+                "MXGATEWAY_API_KEY",
+                "--plaintext",
+                "--filter-prefix",
+                "Galaxy",
+                "--limit",
+                "1",
+                "--json"
+        };
+        assertReadmeExampleParses(args);
+    }
+
+    @Test
+    void readmeDocumentedAcknowledgeAlarmExampleParsesCleanly() {
+        // Client.Java-032 regression — the README's acknowledge-alarm
+        // example (clients/java/README.md:183) must parse without error.
+        // Before the fix it used --session-id (no such option) and
+        // --alarm-reference (the real option is --reference), so picocli
+        // rejected the invocation immediately.
+        String[] args = {
+                "acknowledge-alarm",
+                "--endpoint",
+                "localhost:5000",
+                "--api-key-env",
+                "MXGATEWAY_API_KEY",
+                "--plaintext",
+                "--reference",
+                "\\Galaxy\\Area001.Pump001.PumpFault",
+                "--json"
+        };
+        assertReadmeExampleParses(args);
+    }
+
+    /**
+     * Parses the given args through the production picocli {@link CommandLine}
+     * and asserts no parser error, no unknown option, and no missing required
+     * option. Does not execute the command body — only the option / subcommand
+     * parser is exercised, so no network call is made.
+     */
+    private static void assertReadmeExampleParses(String[] args) {
+        picocli.CommandLine commandLine = MxGatewayCli.commandLine(new FakeClientFactory());
+        try {
+            commandLine.parseArgs(args);
+        } catch (picocli.CommandLine.ParameterException ex) {
+            throw new AssertionError(
+                    "documented README invocation failed picocli parse: "
+                            + String.join(" ", args)
+                            + " -> "
+                            + ex.getMessage(),
+                    ex);
+        }
+    }
+
+    @Test
+    void streamAlarmsCommandFailsFastOnQueueOverflow() {
+        // Client.Java-033 regression — the CLI's stream-alarms bounded queue
+        // used queue.offer(value) which silently dropped messages past
+        // capacity (1024). After the fix the CLI must surface the overflow
+        // as a non-zero exit (mirroring MxEventStream's fail-fast contract).
+        //
+        // The OverflowingFakeClient floods the gRPC observer with 2000
+        // messages synchronously, which exceeds the bounded 1024-element
+        // queue. The fix detects the failed offer, cancels the subscription,
+        // queues an overflow exception, and the drain loop surfaces it.
+        OverflowingFakeClientFactory factory = new OverflowingFakeClientFactory();
+        CliRun run = execute(factory, "stream-alarms", "--filter-prefix", "Flood");
+
+        assertFalse(run.exitCode() == 0,
+                "expected non-zero exit when the alarm queue overflows; got exit=" + run.exitCode()
+                        + " out=\n" + run.output() + "\nerr=\n" + run.errors());
+    }
+
     @Test
     void batchCommandExecutesVersionAndEmitsEorMarker() {
         CliRun run = executeBatch(new FakeClientFactory(), "version --json\n");
@@ -235,6 +318,68 @@ final class MxGatewayCliTests {
         assertTrue(out.contains(MxGatewayCli.BATCH_EOR), out);
     }
 
+    @Test
+    void batchCommandTokenisesDoubleQuotedArgumentWithEmbeddedSpaces() {
+        // Client.Java-034 regression — a real shell-style tokenizer must not
+        // shred `"needs verification"` into two arguments. Drives
+        // acknowledge-alarm through batch and asserts the captured --comment
+        // is the un-quoted string with the embedded space preserved.
+        FakeClientFactory factory = new FakeClientFactory();
+        String line = "acknowledge-alarm --reference Tank01.Level.HiHi --comment \"needs verification\" --operator op1\n";
+        CliRun run = executeBatch(factory, line);
+
+        assertEquals(0, run.exitCode());
+        assertEquals("needs verification", factory.client.lastAcknowledgeAlarmRequest.getComment());
+        assertEquals("op1", factory.client.lastAcknowledgeAlarmRequest.getOperatorUser());
+        assertEquals(
+                "Tank01.Level.HiHi", factory.client.lastAcknowledgeAlarmRequest.getAlarmFullReference());
+    }
+
+    @Test
+    void batchCommandTokenisesSingleQuotedArgumentWithEmbeddedSpaces() {
+        FakeClientFactory factory = new FakeClientFactory();
+        String line =
+                "acknowledge-alarm --reference Tank01.Level.HiHi --comment 'needs verification' --operator op1\n";
+        CliRun run = executeBatch(factory, line);
+
+        assertEquals(0, run.exitCode());
+        assertEquals("needs verification", factory.client.lastAcknowledgeAlarmRequest.getComment());
+    }
+
+    @Test
+    void batchCommandTokenisesBackslashEscapedSpaceOutsideQuotes() {
+        FakeClientFactory factory = new FakeClientFactory();
+        String line =
+                "acknowledge-alarm --reference Tank01.Level.HiHi --comment needs\\ verification\n";
+        CliRun run = executeBatch(factory, line);
+
+        assertEquals(0, run.exitCode());
+        assertEquals("needs verification", factory.client.lastAcknowledgeAlarmRequest.getComment());
+    }
+
+    @Test
+    void batchCommandPreservesEmptyQuotedArgument() {
+        FakeClientFactory factory = new FakeClientFactory();
+        String line = "acknowledge-alarm --reference Tank01.Level.HiHi --comment \"\"\n";
+        CliRun run = executeBatch(factory, line);
+
+        assertEquals(0, run.exitCode());
+        assertEquals("", factory.client.lastAcknowledgeAlarmRequest.getComment());
+    }
+
+    @Test
+    void batchCommandSupportsBackslashEscapedQuoteInsideDoubleQuotes() {
+        // `--comment "with \"inner\" quote"` should round-trip the inner
+        // double-quote into the comment string.
+        FakeClientFactory factory = new FakeClientFactory();
+        String line =
+                "acknowledge-alarm --reference Tank01.Level.HiHi --comment \"with \\\"inner\\\" quote\"\n";
+        CliRun run = executeBatch(factory, line);
+
+        assertEquals(0, run.exitCode());
+        assertEquals("with \"inner\" quote", factory.client.lastAcknowledgeAlarmRequest.getComment());
+    }
+
     @Test
     void batchCommandEmitsEorAfterFailedCommandAndContinues() {
         // An unknown subcommand causes a picocli parse error (non-zero exit).
@@ -290,6 +435,77 @@ final class MxGatewayCliTests {
         }
     }
 
+    /**
+     * Factory whose fake client floods the {@code streamAlarms} observer with
+     * 2000 messages synchronously, exceeding the CLI's bounded 1024-element
+     * queue. Used by the Client.Java-033 fail-fast overflow regression.
+     */
+    private static final class OverflowingFakeClientFactory implements MxGatewayCli.MxGatewayCliClientFactory {
+        @Override
+        public MxGatewayCli.MxGatewayCliClient connect(MxGatewayCli.CommonOptions options) {
+            return new OverflowingFakeClient(options.spec.commandLine().getOut());
+        }
+    }
+
+    private static final class OverflowingFakeClient implements MxGatewayCli.MxGatewayCliClient {
+        private final PrintWriter out;
+
+        OverflowingFakeClient(PrintWriter out) {
+            this.out = out;
+        }
+
+        @Override
+        public PrintWriter out() {
+            return out;
+        }
+
+        @Override
+        public OpenSessionReply openSession(OpenSessionRequest request) {
+            return OpenSessionReply.newBuilder().setSessionId("flood-session").setProtocolStatus(ok()).build();
+        }
+
+        @Override
+        public CloseSessionReply closeSession(CloseSessionRequest request) {
+            return CloseSessionReply.newBuilder()
+                    .setSessionId(request.getSessionId())
+                    .setFinalState(SessionState.SESSION_STATE_CLOSED)
+                    .setProtocolStatus(ok())
+                    .build();
+        }
+
+        @Override
+        public MxGatewayCli.MxGatewayCliSession session(String sessionId) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public AcknowledgeAlarmReply acknowledgeAlarm(AcknowledgeAlarmRequest request) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public MxGatewayAlarmFeedSubscription streamAlarms(
+                StreamAlarmsRequest request, StreamObserver<AlarmFeedMessage> observer) {
+            // Synchronously push 2000 messages to overflow the CLI's bounded
+            // 1024-element queue. The CLI must surface the overflow rather
+            // than silently dropping the trailing ~976 messages.
+            for (int i = 0; i < 2000; i++) {
+                observer.onNext(AlarmFeedMessage.newBuilder()
+                        .setActiveAlarm(ActiveAlarmSnapshot.newBuilder()
+                                .setAlarmFullReference("Flood." + i)
+                                .setCurrentState(AlarmConditionState.ALARM_CONDITION_STATE_ACTIVE)
+                                .setSeverity(700))
+                        .build());
+            }
+            observer.onCompleted();
+            return new MxGatewayAlarmFeedSubscription();
+        }
+
+        @Override
+        public void close() {
+        }
+    }
+
     private static final class FakeClient implements MxGatewayCli.MxGatewayCliClient {
         private final PrintWriter out;
         private final FakeSession session = new FakeSession();

clients/java/zb-mom-ww-mxgateway-client/build.gradle

@@ -1,6 +1,7 @@
 plugins {
     id 'java-library'
     id 'com.google.protobuf'
+    id 'maven-publish'
 }
 
 dependencies {
@@ -30,6 +31,11 @@ sourceSets {
     }
 }
 
+java {
+    withSourcesJar()
+    withJavadocJar()
+}
+
 protobuf {
     protoc {
         artifact = "com.google.protobuf:protoc:${protobufVersion}"

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/BrowseChildrenOptions.java

@@ -0,0 +1,105 @@
+package com.zb.mom.ww.mxgateway.client;
+
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Filters and shape options for {@link GalaxyRepositoryClient#browse(BrowseChildrenOptions)}.
+ * Mirror of the existing DiscoverHierarchy options for the lazy-browse path.
+ *
+ * <p>All filter fields are AND-combined server-side. Empty / unset fields disable
+ * that filter. The {@code includeAttributes} tri-state uses {@code null} to mean
+ * "let the server use its default"; non-{@code null} forwards the explicit flag.
+ */
+public final class BrowseChildrenOptions {
+    private final List<Integer> categoryIds;
+    private final List<String> templateChainContains;
+    private final String tagNameGlob;
+    private final Boolean includeAttributes;
+    private final boolean alarmBearingOnly;
+    private final boolean historizedOnly;
+
+    private BrowseChildrenOptions(Builder b) {
+        this.categoryIds = List.copyOf(b.categoryIds);
+        this.templateChainContains = List.copyOf(b.templateChainContains);
+        this.tagNameGlob = b.tagNameGlob;
+        this.includeAttributes = b.includeAttributes;
+        this.alarmBearingOnly = b.alarmBearingOnly;
+        this.historizedOnly = b.historizedOnly;
+    }
+
+    /** @return immutable list of category IDs to include; empty disables this filter. */
+    public List<Integer> getCategoryIds() { return categoryIds; }
+
+    /** @return immutable list of template names that must appear in each child's template chain. */
+    public List<String> getTemplateChainContains() { return templateChainContains; }
+
+    /** @return SQL-LIKE-style glob applied to {@code tag_name}; empty disables. */
+    public String getTagNameGlob() { return tagNameGlob; }
+
+    /** @return tri-state override for {@code include_attributes}; {@code null} keeps the server default. */
+    public Boolean getIncludeAttributes() { return includeAttributes; }
+
+    /** @return restrict to alarm-bearing objects. */
+    public boolean isAlarmBearingOnly() { return alarmBearingOnly; }
+
+    /** @return restrict to objects with at least one historized attribute. */
+    public boolean isHistorizedOnly() { return historizedOnly; }
+
+    /** @return a fresh builder. */
+    public static Builder builder() { return new Builder(); }
+
+    /** @return options with every filter disabled and {@code includeAttributes} unset. */
+    public static BrowseChildrenOptions empty() { return builder().build(); }
+
+    /** Fluent builder for {@link BrowseChildrenOptions}. */
+    public static final class Builder {
+        private List<Integer> categoryIds = Collections.emptyList();
+        private List<String> templateChainContains = Collections.emptyList();
+        private String tagNameGlob = "";
+        private Boolean includeAttributes = null;
+        private boolean alarmBearingOnly = false;
+        private boolean historizedOnly = false;
+
+        /** Sets the category-id filter. */
+        public Builder categoryIds(List<Integer> v) {
+            this.categoryIds = v == null ? Collections.emptyList() : v;
+            return this;
+        }
+
+        /** Sets the template-chain-contains filter. */
+        public Builder templateChainContains(List<String> v) {
+            this.templateChainContains = v == null ? Collections.emptyList() : v;
+            return this;
+        }
+
+        /** Sets the tag-name glob. */
+        public Builder tagNameGlob(String v) {
+            this.tagNameGlob = v == null ? "" : v;
+            return this;
+        }
+
+        /** Sets the tri-state {@code includeAttributes} override; {@code null} keeps the server default. */
+        public Builder includeAttributes(Boolean v) {
+            this.includeAttributes = v;
+            return this;
+        }
+
+        /** Toggles the alarm-bearing-only filter. */
+        public Builder alarmBearingOnly(boolean v) {
+            this.alarmBearingOnly = v;
+            return this;
+        }
+
+        /** Toggles the historized-only filter. */
+        public Builder historizedOnly(boolean v) {
+            this.historizedOnly = v;
+            return this;
+        }
+
+        /** Builds the immutable options. */
+        public BrowseChildrenOptions build() {
+            return new BrowseChildrenOptions(this);
+        }
+    }
+}

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/DeployEventSubscription.java

@@ -2,64 +2,19 @@ package com.zb.mom.ww.mxgateway.client;
 
 import galaxy_repository.v1.GalaxyRepositoryOuterClass.DeployEvent;
 import galaxy_repository.v1.GalaxyRepositoryOuterClass.WatchDeployEventsRequest;
-import io.grpc.stub.ClientCallStreamObserver;
-import io.grpc.stub.ClientResponseObserver;
 import io.grpc.stub.StreamObserver;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicReference;
 
 /**
  * Cancellable handle returned by the async {@code watchDeployEvents} variant.
  * Mirrors {@link MxGatewayEventSubscription} but for the Galaxy Repository
  * deploy-event stream.
+ *
+ * <p>All lifecycle / cancellation behaviour is inherited from
+ * {@link MxGatewayStreamSubscription} (Client.Java-036).
  */
-public final class DeployEventSubscription implements AutoCloseable {
-    private final AtomicReference<ClientCallStreamObserver<WatchDeployEventsRequest>> requestStream =
-            new AtomicReference<>();
-    private final AtomicBoolean cancelled = new AtomicBoolean();
-
-    ClientResponseObserver<WatchDeployEventsRequest, DeployEvent> wrap(StreamObserver<DeployEvent> observer) {
-        return new ClientResponseObserver<>() {
-            @Override
-            public void beforeStart(ClientCallStreamObserver<WatchDeployEventsRequest> stream) {
-                requestStream.set(stream);
-                if (cancelled.get()) {
-                    stream.cancel("client cancelled deploy event stream", null);
-                }
-            }
-
-            @Override
-            public void onNext(DeployEvent value) {
-                observer.onNext(value);
-            }
-
-            @Override
-            public void onError(Throwable error) {
-                observer.onError(error);
-            }
-
-            @Override
-            public void onCompleted() {
-                observer.onCompleted();
-            }
-        };
-    }
-
-    /**
-     * Cancels the underlying gRPC call. Safe to invoke before the call has
-     * started; cancellation is recorded and applied as soon as the stream
-     * attaches.
-     */
-    public void cancel() {
-        cancelled.set(true);
-        ClientCallStreamObserver<WatchDeployEventsRequest> stream = requestStream.get();
-        if (stream != null) {
-            stream.cancel("client cancelled deploy event stream", null);
-        }
-    }
-
-    @Override
-    public void close() {
-        cancel();
+public final class DeployEventSubscription
+        extends MxGatewayStreamSubscription<WatchDeployEventsRequest, DeployEvent> {
+    public DeployEventSubscription() {
+        super("client cancelled deploy event stream");
     }
 }

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/GalaxyRepositoryClient.java

@@ -4,6 +4,8 @@ import com.google.common.util.concurrent.FutureCallback;
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.MoreExecutors;
 import galaxy_repository.v1.GalaxyRepositoryGrpc;
+import galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply;
+import galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest;
 import galaxy_repository.v1.GalaxyRepositoryOuterClass.DeployEvent;
 import galaxy_repository.v1.GalaxyRepositoryOuterClass.DiscoverHierarchyReply;
 import galaxy_repository.v1.GalaxyRepositoryOuterClass.DiscoverHierarchyRequest;
@@ -37,6 +39,7 @@ import javax.net.ssl.SSLException;
  */
 public final class GalaxyRepositoryClient implements AutoCloseable {
     private static final int DISCOVER_HIERARCHY_PAGE_SIZE = 5000;
+    private static final int BROWSE_CHILDREN_PAGE_SIZE = 500;
 
     private final ManagedChannel ownedChannel;
     private final MxGatewayClientOptions options;
@@ -213,6 +216,98 @@ public final class GalaxyRepositoryClient implements AutoCloseable {
         return discoverHierarchyPageAsync("", new java.util.ArrayList<>(), new java.util.HashSet<>());
     }
 
+    /**
+     * Lazy-browse entry point: fetches the root layer of the Galaxy hierarchy.
+     * Each returned {@link LazyBrowseNode} can be expanded on demand via
+     * {@link LazyBrowseNode#expand()} to load its direct children.
+     *
+     * @return the root nodes (no parent selector) with default options
+     * @throws MxGatewayException on transport or protocol failure
+     */
+    public List<LazyBrowseNode> browse() {
+        return browse(null);
+    }
+
+    /**
+     * Lazy-browse entry point with caller-supplied filters / shape.
+     *
+     * @param options filter and shape options; {@code null} means {@link BrowseChildrenOptions#empty()}
+     * @return the root nodes matching the options
+     * @throws MxGatewayException on transport or protocol failure
+     */
+    public List<LazyBrowseNode> browse(BrowseChildrenOptions options) {
+        BrowseChildrenOptions effective = options == null ? BrowseChildrenOptions.empty() : options;
+        return browseChildrenInner(null, effective);
+    }
+
+    /**
+     * Issues a single {@code BrowseChildren} RPC and returns the raw reply.
+     * Callers wanting full control over pagination can drive the loop themselves.
+     *
+     * @param request the request to send
+     * @return the reply
+     * @throws MxGatewayException on transport or protocol failure
+     */
+    public BrowseChildrenReply browseChildrenRaw(BrowseChildrenRequest request) {
+        try {
+            return rawBlockingStub().browseChildren(request);
+        } catch (RuntimeException error) {
+            if (error instanceof MxGatewayException) {
+                throw error;
+            }
+            throw MxGatewayErrors.fromGrpc("galaxy browse children", error);
+        }
+    }
+
+    /**
+     * Drives the BrowseChildren paging loop for a single parent (or roots when
+     * {@code parentGobjectId} is {@code null}). Detects repeated page tokens to
+     * avoid infinite loops on a buggy server.
+     */
+    List<LazyBrowseNode> browseChildrenInner(Integer parentGobjectId, BrowseChildrenOptions options) {
+        java.util.ArrayList<LazyBrowseNode> nodes = new java.util.ArrayList<>();
+        java.util.HashSet<String> seenPageTokens = new java.util.HashSet<>();
+        String pageToken = "";
+        while (true) {
+            BrowseChildrenRequest.Builder builder = BrowseChildrenRequest.newBuilder()
+                    .setPageSize(BROWSE_CHILDREN_PAGE_SIZE)
+                    .setPageToken(pageToken)
+                    .setAlarmBearingOnly(options.isAlarmBearingOnly())
+                    .setHistorizedOnly(options.isHistorizedOnly());
+            if (parentGobjectId != null) {
+                builder.setParentGobjectId(parentGobjectId.intValue());
+            }
+            if (!options.getCategoryIds().isEmpty()) {
+                builder.addAllCategoryIds(options.getCategoryIds());
+            }
+            if (!options.getTemplateChainContains().isEmpty()) {
+                builder.addAllTemplateChainContains(options.getTemplateChainContains());
+            }
+            if (!options.getTagNameGlob().isEmpty()) {
+                builder.setTagNameGlob(options.getTagNameGlob());
+            }
+            if (options.getIncludeAttributes() != null) {
+                builder.setIncludeAttributes(options.getIncludeAttributes());
+            }
+
+            BrowseChildrenReply reply = browseChildrenRaw(builder.build());
+
+            for (int i = 0; i < reply.getChildrenCount(); i++) {
+                boolean hint = i < reply.getChildHasChildrenCount() && reply.getChildHasChildren(i);
+                nodes.add(new LazyBrowseNode(this, reply.getChildren(i), hint, options));
+            }
+
+            pageToken = reply.getNextPageToken();
+            if (pageToken == null || pageToken.isEmpty()) {
+                return nodes;
+            }
+            if (!seenPageTokens.add(pageToken)) {
+                throw new MxGatewayException(
+                        "galaxy browse children returned repeated page token: " + pageToken);
+            }
+        }
+    }
+
     /**
      * Subscribes to {@code WatchDeployEvents} via the async stub and consumes
      * results through a blocking iterator. Closing the returned stream cancels

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/LazyBrowseNode.java

@@ -0,0 +1,150 @@
+package com.zb.mom.ww.mxgateway.client;
+
+import galaxy_repository.v1.GalaxyRepositoryOuterClass.GalaxyObject;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+/**
+ * One node in a lazy-loaded Galaxy browse tree. Holds the underlying
+ * {@link GalaxyObject} and exposes {@link #expand()} to fetch its direct
+ * children on demand. Expansion is one-shot: a second call is a no-op.
+ * Pagination of large sibling sets is handled internally by the client.
+ */
+public final class LazyBrowseNode {
+    private final GalaxyRepositoryClient client;
+    private final GalaxyObject object;
+    private final boolean hasChildrenHint;
+    private final BrowseChildrenOptions options;
+
+    // expandLock gates the start of a new expand AND the publish of the in-flight
+    // future. Readers (getChildren / isExpanded) use a separate read-write lock so
+    // they never block on the gRPC call.
+    private final Object expandLock = new Object();
+    private CompletableFuture<Void> inFlight;
+
+    private final ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();
+    private List<LazyBrowseNode> children = Collections.emptyList();
+    private boolean isExpanded;
+
+    LazyBrowseNode(
+            GalaxyRepositoryClient client,
+            GalaxyObject object,
+            boolean hasChildrenHint,
+            BrowseChildrenOptions options) {
+        this.client = client;
+        this.object = object;
+        this.hasChildrenHint = hasChildrenHint;
+        this.options = options;
+    }
+
+    /** @return the underlying Galaxy object proto for this node. */
+    public GalaxyObject getObject() {
+        return object;
+    }
+
+    /** @return {@code true} when the server reports this node has at least one matching descendant. */
+    public boolean hasChildrenHint() {
+        return hasChildrenHint;
+    }
+
+    /** @return a snapshot of direct children loaded by {@link #expand()}; empty until then. */
+    public List<LazyBrowseNode> getChildren() {
+        readWriteLock.readLock().lock();
+        try {
+            return List.copyOf(children);
+        } finally {
+            readWriteLock.readLock().unlock();
+        }
+    }
+
+    /** @return {@code true} after the first {@link #expand()} call completes. */
+    public boolean isExpanded() {
+        readWriteLock.readLock().lock();
+        try {
+            return isExpanded;
+        } finally {
+            readWriteLock.readLock().unlock();
+        }
+    }
+
+    /**
+     * Fetches direct children from the gateway and populates {@link #getChildren()}.
+     * Idempotent: subsequent calls are no-ops and do not issue a second RPC.
+     *
+     * <p>Concurrent callers coalesce onto a single in-flight RPC: the first caller
+     * (the "leader") issues the gRPC call, while any other thread that calls
+     * {@code expand()} during that window blocks on the leader's future and sees
+     * the same result (or the same exception). On failure the in-flight slot is
+     * cleared so a subsequent call can retry.
+     *
+     * <p>Readers ({@link #getChildren()} / {@link #isExpanded()}) take a separate
+     * read lock and are never blocked for the duration of the RPC.
+     *
+     * @throws MxGatewayException on transport or protocol failure
+     */
+    public void expand() {
+        if (isExpanded()) {
+            return;
+        }
+
+        CompletableFuture<Void> future;
+        boolean iAmTheLeader;
+        synchronized (expandLock) {
+            if (isExpanded()) {
+                return;
+            }
+            if (inFlight != null) {
+                future = inFlight;
+                iAmTheLeader = false;
+            } else {
+                future = new CompletableFuture<>();
+                inFlight = future;
+                iAmTheLeader = true;
+            }
+        }
+
+        if (iAmTheLeader) {
+            try {
+                List<LazyBrowseNode> loaded =
+                        client.browseChildrenInner(object.getGobjectId(), options);
+                readWriteLock.writeLock().lock();
+                try {
+                    this.children = loaded;
+                    this.isExpanded = true;
+                } finally {
+                    readWriteLock.writeLock().unlock();
+                }
+                synchronized (expandLock) {
+                    inFlight = null;
+                }
+                future.complete(null);
+            } catch (RuntimeException ex) {
+                synchronized (expandLock) {
+                    inFlight = null;
+                }
+                future.completeExceptionally(ex);
+                throw ex;
+            }
+        } else {
+            try {
+                future.get();
+            } catch (InterruptedException ie) {
+                Thread.currentThread().interrupt();
+                throw new MxGatewayException("Interrupted waiting for browse-children expand.", ie);
+            } catch (ExecutionException ee) {
+                Throwable cause = ee.getCause();
+                if (cause instanceof MxGatewayException me) {
+                    throw me;
+                }
+                if (cause instanceof RuntimeException re) {
+                    throw re;
+                }
+                throw new MxGatewayException("BrowseChildren expand failed.", cause);
+            }
+        }
+    }
+}

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayActiveAlarmsSubscription.java

@@ -1,10 +1,6 @@
 package com.zb.mom.ww.mxgateway.client;
 
-import io.grpc.stub.ClientCallStreamObserver;
-import io.grpc.stub.ClientResponseObserver;
 import io.grpc.stub.StreamObserver;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicReference;
 import mxaccess_gateway.v1.MxaccessGateway.ActiveAlarmSnapshot;
 import mxaccess_gateway.v1.MxaccessGateway.QueryActiveAlarmsRequest;
 
@@ -15,53 +11,13 @@ import mxaccess_gateway.v1.MxaccessGateway.QueryActiveAlarmsRequest;
  * {@link #cancel()} entry point that aborts the underlying gRPC call. The
  * subscription also implements {@link AutoCloseable} so it can participate in
  * try-with-resources blocks.
+ *
+ * <p>All lifecycle / cancellation behaviour is inherited from
+ * {@link MxGatewayStreamSubscription} (Client.Java-036).
  */
-public final class MxGatewayActiveAlarmsSubscription implements AutoCloseable {
-    private final AtomicReference<ClientCallStreamObserver<QueryActiveAlarmsRequest>> requestStream = new AtomicReference<>();
-    private final AtomicBoolean cancelled = new AtomicBoolean();
-
-    ClientResponseObserver<QueryActiveAlarmsRequest, ActiveAlarmSnapshot> wrap(StreamObserver<ActiveAlarmSnapshot> observer) {
-        return new ClientResponseObserver<>() {
-            @Override
-            public void beforeStart(ClientCallStreamObserver<QueryActiveAlarmsRequest> stream) {
-                requestStream.set(stream);
-                if (cancelled.get()) {
-                    stream.cancel("client cancelled active-alarms query", null);
-                }
-            }
-
-            @Override
-            public void onNext(ActiveAlarmSnapshot value) {
-                observer.onNext(value);
-            }
-
-            @Override
-            public void onError(Throwable error) {
-                observer.onError(error);
-            }
-
-            @Override
-            public void onCompleted() {
-                observer.onCompleted();
-            }
-        };
-    }
-
-    /**
-     * Cancels the underlying gRPC call. Safe to invoke before the call has
-     * started; cancellation is recorded and applied as soon as the stream
-     * attaches.
-     */
-    public void cancel() {
-        cancelled.set(true);
-        ClientCallStreamObserver<QueryActiveAlarmsRequest> stream = requestStream.get();
-        if (stream != null) {
-            stream.cancel("client cancelled active-alarms query", null);
-        }
-    }
-
-    @Override
-    public void close() {
-        cancel();
+public final class MxGatewayActiveAlarmsSubscription
+        extends MxGatewayStreamSubscription<QueryActiveAlarmsRequest, ActiveAlarmSnapshot> {
+    public MxGatewayActiveAlarmsSubscription() {
+        super("client cancelled active-alarms query");
     }
 }

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayAlarmFeedSubscription.java

@@ -1,10 +1,6 @@
 package com.zb.mom.ww.mxgateway.client;
 
-import io.grpc.stub.ClientCallStreamObserver;
-import io.grpc.stub.ClientResponseObserver;
 import io.grpc.stub.StreamObserver;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicReference;
 import mxaccess_gateway.v1.MxaccessGateway.AlarmFeedMessage;
 import mxaccess_gateway.v1.MxaccessGateway.StreamAlarmsRequest;
 
@@ -15,53 +11,13 @@ import mxaccess_gateway.v1.MxaccessGateway.StreamAlarmsRequest;
  * {@link #cancel()} entry point that aborts the underlying gRPC call. The
  * subscription also implements {@link AutoCloseable} so it can participate in
  * try-with-resources blocks.
+ *
+ * <p>All lifecycle / cancellation behaviour is inherited from
+ * {@link MxGatewayStreamSubscription} (Client.Java-036).
  */
-public final class MxGatewayAlarmFeedSubscription implements AutoCloseable {
-    private final AtomicReference<ClientCallStreamObserver<StreamAlarmsRequest>> requestStream = new AtomicReference<>();
-    private final AtomicBoolean cancelled = new AtomicBoolean();
-
-    ClientResponseObserver<StreamAlarmsRequest, AlarmFeedMessage> wrap(StreamObserver<AlarmFeedMessage> observer) {
-        return new ClientResponseObserver<>() {
-            @Override
-            public void beforeStart(ClientCallStreamObserver<StreamAlarmsRequest> stream) {
-                requestStream.set(stream);
-                if (cancelled.get()) {
-                    stream.cancel("client cancelled alarm feed", null);
-                }
-            }
-
-            @Override
-            public void onNext(AlarmFeedMessage value) {
-                observer.onNext(value);
-            }
-
-            @Override
-            public void onError(Throwable error) {
-                observer.onError(error);
-            }
-
-            @Override
-            public void onCompleted() {
-                observer.onCompleted();
-            }
-        };
-    }
-
-    /**
-     * Cancels the underlying gRPC call. Safe to invoke before the call has
-     * started; cancellation is recorded and applied as soon as the stream
-     * attaches.
-     */
-    public void cancel() {
-        cancelled.set(true);
-        ClientCallStreamObserver<StreamAlarmsRequest> stream = requestStream.get();
-        if (stream != null) {
-            stream.cancel("client cancelled alarm feed", null);
-        }
-    }
-
-    @Override
-    public void close() {
-        cancel();
+public final class MxGatewayAlarmFeedSubscription
+        extends MxGatewayStreamSubscription<StreamAlarmsRequest, AlarmFeedMessage> {
+    public MxGatewayAlarmFeedSubscription() {
+        super("client cancelled alarm feed");
     }
 }

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayClient.java

@@ -384,6 +384,15 @@ public final class MxGatewayClient implements AutoCloseable {
             } catch (SSLException error) {
                 throw new MxGatewayException("failed to configure gateway TLS", error);
             }
+        } else if (!options.requireCertificateValidation()) {
+            try {
+                builder.sslContext(GrpcSslContexts.forClient()
+                        .trustManager(io.grpc.netty.shaded.io.netty.handler.ssl.util
+                                .InsecureTrustManagerFactory.INSTANCE)
+                        .build());
+            } catch (SSLException error) {
+                throw new MxGatewayException("failed to configure lenient gateway TLS", error);
+            }
         } else {
             builder.useTransportSecurity();
         }
@@ -393,6 +402,19 @@ public final class MxGatewayClient implements AutoCloseable {
         return builder.build();
     }
 
+    /**
+     * Package-visible test seam — creates a raw {@link ManagedChannel} from the
+     * given options without attaching auth interceptors. Used by TLS fixture
+     * tests to verify channel construction behaviour without a full
+     * {@link MxGatewayClient} wrapper.
+     *
+     * @param options the client options
+     * @return a new {@link ManagedChannel}
+     */
+    static ManagedChannel createChannelForTests(MxGatewayClientOptions options) {
+        return createChannel(options);
+    }
+
     private <T extends io.grpc.stub.AbstractStub<T>> T withDeadline(T stub) {
         if (options.callTimeout().isNegative()) {
             return stub;

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayClientOptions.java

@@ -20,6 +20,7 @@ public final class MxGatewayClientOptions {
     private final String apiKey;
     private final boolean plaintext;
     private final Path caCertificatePath;
+    private final boolean requireCertificateValidation;
     private final String serverNameOverride;
     private final Duration connectTimeout;
     private final Duration callTimeout;
@@ -31,6 +32,7 @@ public final class MxGatewayClientOptions {
         apiKey = builder.apiKey == null ? "" : builder.apiKey;
         plaintext = builder.plaintext;
         caCertificatePath = builder.caCertificatePath;
+        requireCertificateValidation = builder.requireCertificateValidation;
         serverNameOverride = builder.serverNameOverride == null ? "" : builder.serverNameOverride;
         connectTimeout = builder.connectTimeout == null ? DEFAULT_CONNECT_TIMEOUT : builder.connectTimeout;
         callTimeout = builder.callTimeout == null ? DEFAULT_CALL_TIMEOUT : builder.callTimeout;
@@ -95,6 +97,18 @@ public final class MxGatewayClientOptions {
         return caCertificatePath;
     }
 
+    /**
+     * Returns whether TLS certificate verification is required even when no CA is pinned.
+     * When {@code false} (default), the gateway's self-signed certificate is accepted
+     * without verification. When {@code true}, the OS trust store is used.
+     * Pinning a CA via {@link #caCertificatePath()} always verifies regardless of this flag.
+     *
+     * @return {@code true} if strict certificate verification is required
+     */
+    public boolean requireCertificateValidation() {
+        return requireCertificateValidation;
+    }
+
     /**
      * Returns the TLS server-name override, or an empty string when none was supplied.
      *
@@ -148,6 +162,8 @@ public final class MxGatewayClientOptions {
                 + plaintext
                 + ", caCertificatePath="
                 + caCertificatePath
+                + ", requireCertificateValidation="
+                + requireCertificateValidation
                 + ", serverNameOverride='"
                 + serverNameOverride
                 + '\''
@@ -177,6 +193,7 @@ public final class MxGatewayClientOptions {
         private String apiKey;
         private boolean plaintext;
         private Path caCertificatePath;
+        private boolean requireCertificateValidation;
         private String serverNameOverride;
         private Duration connectTimeout;
         private Duration callTimeout;
@@ -230,6 +247,21 @@ public final class MxGatewayClientOptions {
             return this;
         }
 
+        /**
+         * When {@code true}, TLS connections without a pinned CA use the OS trust store
+         * and will reject the gateway's self-signed certificate. When {@code false}
+         * (default), the gateway certificate is accepted without verification —
+         * appropriate for this internal tool's auto-generated self-signed certificate.
+         * Pinning a CA via {@link #caCertificatePath(Path)} always verifies.
+         *
+         * @param value {@code true} to require certificate validation, {@code false} to accept any cert
+         * @return this builder
+         */
+        public Builder requireCertificateValidation(boolean value) {
+            requireCertificateValidation = value;
+            return this;
+        }
+
         /**
          * Overrides the TLS server name used during the handshake.
          *

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayEventSubscription.java

@@ -1,10 +1,6 @@
 package com.zb.mom.ww.mxgateway.client;
 
-import io.grpc.stub.ClientCallStreamObserver;
-import io.grpc.stub.ClientResponseObserver;
 import io.grpc.stub.StreamObserver;
-import java.util.concurrent.atomic.AtomicReference;
-import java.util.concurrent.atomic.AtomicBoolean;
 import mxaccess_gateway.v1.MxaccessGateway.MxEvent;
 import mxaccess_gateway.v1.MxaccessGateway.StreamEventsRequest;
 
@@ -15,53 +11,13 @@ import mxaccess_gateway.v1.MxaccessGateway.StreamEventsRequest;
  * {@link #cancel()} entry point that aborts the underlying gRPC call. The
  * subscription also implements {@link AutoCloseable} so it can participate in
  * try-with-resources blocks.
+ *
+ * <p>All lifecycle / cancellation behaviour is inherited from
+ * {@link MxGatewayStreamSubscription} (Client.Java-036).
  */
-public final class MxGatewayEventSubscription implements AutoCloseable {
-    private final AtomicReference<ClientCallStreamObserver<StreamEventsRequest>> requestStream = new AtomicReference<>();
-    private final AtomicBoolean cancelled = new AtomicBoolean();
-
-    ClientResponseObserver<StreamEventsRequest, MxEvent> wrap(StreamObserver<MxEvent> observer) {
-        return new ClientResponseObserver<>() {
-            @Override
-            public void beforeStart(ClientCallStreamObserver<StreamEventsRequest> stream) {
-                requestStream.set(stream);
-                if (cancelled.get()) {
-                    stream.cancel("client cancelled event stream", null);
-                }
-            }
-
-            @Override
-            public void onNext(MxEvent value) {
-                observer.onNext(value);
-            }
-
-            @Override
-            public void onError(Throwable error) {
-                observer.onError(error);
-            }
-
-            @Override
-            public void onCompleted() {
-                observer.onCompleted();
-            }
-        };
-    }
-
-    /**
-     * Cancels the underlying gRPC call. Safe to invoke before the call has
-     * started; cancellation is recorded and applied as soon as the stream
-     * attaches.
-     */
-    public void cancel() {
-        cancelled.set(true);
-        ClientCallStreamObserver<StreamEventsRequest> stream = requestStream.get();
-        if (stream != null) {
-            stream.cancel("client cancelled event stream", null);
-        }
-    }
-
-    @Override
-    public void close() {
-        cancel();
+public final class MxGatewayEventSubscription
+        extends MxGatewayStreamSubscription<StreamEventsRequest, MxEvent> {
+    public MxGatewayEventSubscription() {
+        super("client cancelled event stream");
     }
 }

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayStreamSubscription.java

@@ -0,0 +1,89 @@
+package com.zb.mom.ww.mxgateway.client;
+
+import io.grpc.stub.ClientCallStreamObserver;
+import io.grpc.stub.ClientResponseObserver;
+import io.grpc.stub.StreamObserver;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+
+/**
+ * Shared base for the cancellable subscription handles returned by the
+ * async-style server-streaming RPCs ({@code streamEvents}, {@code streamAlarms},
+ * {@code queryActiveAlarms}, {@code watchDeployEvents}).
+ *
+ * <p>All four subscription classes share the same lifecycle and cancellation
+ * contract:
+ *
+ * <ul>
+ *   <li>{@link #wrap(StreamObserver)} returns a {@link ClientResponseObserver}
+ *       that captures the underlying {@link ClientCallStreamObserver} in
+ *       {@code beforeStart}. If {@link #cancel()} was called before the gRPC
+ *       call attached, the stream is cancelled eagerly inside
+ *       {@code beforeStart} (the Client.Java-014 close-before-beforeStart
+ *       fix).</li>
+ *   <li>{@link #cancel()} is idempotent. It records the cancellation flag and
+ *       forwards {@code cancel(message, cause)} to the underlying stream when
+ *       one is attached; otherwise the flag is checked in {@code beforeStart}
+ *       once the stream attaches.</li>
+ *   <li>{@link #close()} delegates to {@link #cancel()} so the handle can be
+ *       used with try-with-resources.</li>
+ * </ul>
+ *
+ * <p>Subclasses supply only the cancel-message string used by {@code cancel()}.
+ * Refactor introduced for Client.Java-036 — the four prior subscription
+ * classes were structural near-clones (~60 lines each).
+ */
+abstract class MxGatewayStreamSubscription<TRequest, TResponse> implements AutoCloseable {
+    private final AtomicReference<ClientCallStreamObserver<TRequest>> requestStream = new AtomicReference<>();
+    private final AtomicBoolean cancelled = new AtomicBoolean();
+    private final String cancelMessage;
+
+    MxGatewayStreamSubscription(String cancelMessage) {
+        this.cancelMessage = cancelMessage;
+    }
+
+    final ClientResponseObserver<TRequest, TResponse> wrap(StreamObserver<TResponse> observer) {
+        return new ClientResponseObserver<>() {
+            @Override
+            public void beforeStart(ClientCallStreamObserver<TRequest> stream) {
+                requestStream.set(stream);
+                if (cancelled.get()) {
+                    stream.cancel(cancelMessage, null);
+                }
+            }
+
+            @Override
+            public void onNext(TResponse value) {
+                observer.onNext(value);
+            }
+
+            @Override
+            public void onError(Throwable error) {
+                observer.onError(error);
+            }
+
+            @Override
+            public void onCompleted() {
+                observer.onCompleted();
+            }
+        };
+    }
+
+    /**
+     * Cancels the underlying gRPC call. Safe to invoke before the call has
+     * started; cancellation is recorded and applied as soon as the stream
+     * attaches.
+     */
+    public final void cancel() {
+        cancelled.set(true);
+        ClientCallStreamObserver<TRequest> stream = requestStream.get();
+        if (stream != null) {
+            stream.cancel(cancelMessage, null);
+        }
+    }
+
+    @Override
+    public final void close() {
+        cancel();
+    }
+}

clients/java/zb-mom-ww-mxgateway-client/src/test/java/com/zb/mom/ww/mxgateway/client/GalaxyRepositoryClientTests.java

@@ -8,6 +8,8 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import com.google.protobuf.Timestamp;
 import galaxy_repository.v1.GalaxyRepositoryGrpc;
+import galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenReply;
+import galaxy_repository.v1.GalaxyRepositoryOuterClass.BrowseChildrenRequest;
 import galaxy_repository.v1.GalaxyRepositoryOuterClass.DeployEvent;
 import galaxy_repository.v1.GalaxyRepositoryOuterClass.DiscoverHierarchyReply;
 import galaxy_repository.v1.GalaxyRepositoryOuterClass.DiscoverHierarchyRequest;
@@ -24,6 +26,7 @@ import io.grpc.Server;
 import io.grpc.ServerCall;
 import io.grpc.ServerCallHandler;
 import io.grpc.ServerInterceptor;
+import io.grpc.Status;
 import io.grpc.inprocess.InProcessChannelBuilder;
 import io.grpc.inprocess.InProcessServerBuilder;
 import io.grpc.stub.ClientCallStreamObserver;
@@ -31,11 +34,20 @@ import io.grpc.stub.ClientResponseObserver;
 import io.grpc.stub.StreamObserver;
 import java.time.Duration;
 import java.time.Instant;
+import java.util.ArrayDeque;
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
+import java.util.Queue;
 import java.util.UUID;
+import java.util.ArrayList;
+import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 import org.junit.jupiter.api.Test;
 
@@ -196,6 +208,27 @@ final class GalaxyRepositoryClientTests {
         }
     }
 
+    @Test
+    void browseChildrenRejectsRepeatedPageToken() throws Exception {
+        // Queue the same BrowseChildrenReply twice with a non-empty NextPageToken.
+        // The client will request a second page and detect that the token repeats.
+        BrowseChildrenService service = new BrowseChildrenService();
+        BrowseChildrenReply repeatedReply = browseReply(
+                List.of(obj(1, "Plant", true)),
+                List.of(true),
+                1L,
+                "1:abc:1");
+        service.replies.add(repeatedReply);
+        service.replies.add(repeatedReply);
+
+        try (InProcessGalaxy g = InProcessGalaxy.start(service, new AtomicReference<>());
+                GalaxyRepositoryClient client = g.client("")) {
+            MxGatewayException error = assertThrows(MxGatewayException.class, client::browse);
+
+            assertTrue(error.getMessage().contains("repeated page token"));
+        }
+    }
+
     @Test
     void watchDeployEventsReceivesEventsInOrder() throws Exception {
         DeployEvent first = DeployEvent.newBuilder()
@@ -306,6 +339,294 @@ final class GalaxyRepositoryClientTests {
         }
     }
 
+    @Test
+    void browseNoParentReturnsRoots() throws Exception {
+        BrowseChildrenService service = new BrowseChildrenService();
+        service.replies.add(browseReply(
+                List.of(obj(1, "Plant", true), obj(2, "Other", false)),
+                List.of(true, false),
+                1L,
+                ""));
+
+        try (InProcessGalaxy g = InProcessGalaxy.start(service, new AtomicReference<>());
+                GalaxyRepositoryClient client = g.client("")) {
+            List<LazyBrowseNode> roots = client.browse();
+
+            assertEquals(2, roots.size());
+            assertEquals("Plant", roots.get(0).getObject().getTagName());
+            assertTrue(roots.get(0).hasChildrenHint());
+            assertFalse(roots.get(0).isExpanded());
+            assertEquals("Other", roots.get(1).getObject().getTagName());
+            assertFalse(roots.get(1).hasChildrenHint());
+            assertFalse(roots.get(1).isExpanded());
+            assertEquals(1, service.calls.size());
+            assertFalse(service.calls.get(0).hasParentGobjectId());
+        }
+    }
+
+    @Test
+    void browseExpandPopulatesChildrenAndMarksExpanded() throws Exception {
+        BrowseChildrenService service = new BrowseChildrenService();
+        service.replies.add(browseReply(
+                List.of(obj(1, "Plant", true)),
+                List.of(true),
+                1L,
+                ""));
+        service.replies.add(browseReply(
+                List.of(obj(10, "Line1", false)),
+                List.of(false),
+                1L,
+                ""));
+
+        try (InProcessGalaxy g = InProcessGalaxy.start(service, new AtomicReference<>());
+                GalaxyRepositoryClient client = g.client("")) {
+            List<LazyBrowseNode> roots = client.browse();
+            roots.get(0).expand();
+
+            assertTrue(roots.get(0).isExpanded());
+            assertEquals(1, roots.get(0).getChildren().size());
+            assertEquals("Line1", roots.get(0).getChildren().get(0).getObject().getTagName());
+            assertEquals(2, service.calls.size());
+            assertTrue(service.calls.get(1).hasParentGobjectId());
+            assertEquals(1, service.calls.get(1).getParentGobjectId());
+        }
+    }
+
+    @Test
+    void browseExpandIdempotentNoSecondRpc() throws Exception {
+        BrowseChildrenService service = new BrowseChildrenService();
+        service.replies.add(browseReply(
+                List.of(obj(1, "Plant", true)),
+                List.of(true),
+                1L,
+                ""));
+        service.replies.add(browseReply(
+                List.of(obj(10, "Line1", false)),
+                List.of(false),
+                1L,
+                ""));
+
+        try (InProcessGalaxy g = InProcessGalaxy.start(service, new AtomicReference<>());
+                GalaxyRepositoryClient client = g.client("")) {
+            List<LazyBrowseNode> roots = client.browse();
+            roots.get(0).expand();
+            roots.get(0).expand();
+
+            assertEquals(2, service.calls.size());
+            assertEquals(1, roots.get(0).getChildren().size());
+        }
+    }
+
+    @Test
+    void browseExpandUnknownParentThrowsGalaxyNotFound() throws Exception {
+        BrowseChildrenService service = new BrowseChildrenService();
+        service.replies.add(browseReply(
+                List.of(obj(1, "Plant", true)),
+                List.of(true),
+                1L,
+                ""));
+        service.errors.add(Status.NOT_FOUND.withDescription("Parent not found").asRuntimeException());
+
+        try (InProcessGalaxy g = InProcessGalaxy.start(service, new AtomicReference<>());
+                GalaxyRepositoryClient client = g.client("")) {
+            List<LazyBrowseNode> roots = client.browse();
+
+            MxGatewayException error = assertThrows(MxGatewayException.class, () -> roots.get(0).expand());
+            assertTrue(
+                    error.getMessage().toLowerCase().contains("not found"),
+                    "expected message to mention 'not found', got: " + error.getMessage());
+        }
+    }
+
+    @Test
+    void browseExpandMultiPageGathersAllPages() throws Exception {
+        BrowseChildrenService service = new BrowseChildrenService();
+        // Roots
+        service.replies.add(browseReply(
+                List.of(obj(7, "Plant", true)),
+                List.of(true),
+                1L,
+                ""));
+        // First child page with a next token
+        service.replies.add(browseReply(
+                List.of(obj(70, "ChildA", false), obj(71, "ChildB", false)),
+                List.of(false, false),
+                1L,
+                "7:abc:2"));
+        // Second child page closes the loop
+        service.replies.add(browseReply(
+                List.of(obj(72, "ChildC", false)),
+                List.of(false),
+                1L,
+                ""));
+
+        try (InProcessGalaxy g = InProcessGalaxy.start(service, new AtomicReference<>());
+                GalaxyRepositoryClient client = g.client("")) {
+            List<LazyBrowseNode> roots = client.browse();
+            roots.get(0).expand();
+
+            assertEquals(3, roots.get(0).getChildren().size());
+            assertEquals(3, service.calls.size());
+            assertEquals("7:abc:2", service.calls.get(2).getPageToken());
+        }
+    }
+
+    @Test
+    void browseExpandConcurrentCallersOnlyFireOneRpc() throws Exception {
+        // Verifies that concurrent expand() calls coalesce onto a single in-flight
+        // BrowseChildren RPC and that readers (isExpanded/getChildren) are not
+        // blocked for the full RPC duration.
+        BrowseChildrenReply rootsReply = browseReply(
+                List.of(obj(1, "Plant", true)),
+                List.of(true),
+                7L,
+                "");
+        BrowseChildrenReply childrenReply = browseReply(
+                List.of(obj(2, "Mixer_001", false)),
+                List.of(false),
+                7L,
+                "");
+
+        // Gate the child fetch behind a latch so multiple expanders can pile up.
+        CountDownLatch release = new CountDownLatch(1);
+        AtomicInteger childCalls = new AtomicInteger();
+        BrowseChildrenService service = new BrowseChildrenService() {
+            @Override
+            public void browseChildren(
+                    BrowseChildrenRequest request, StreamObserver<BrowseChildrenReply> responseObserver) {
+                calls.add(request);
+                BrowseChildrenReply reply;
+                if (!request.hasParentGobjectId()) {
+                    reply = rootsReply;
+                } else {
+                    // Block the leader until the followers have arrived.
+                    try {
+                        assertTrue(release.await(5, TimeUnit.SECONDS), "release latch never tripped");
+                    } catch (InterruptedException ie) {
+                        Thread.currentThread().interrupt();
+                        responseObserver.onError(Status.CANCELLED.asRuntimeException());
+                        return;
+                    }
+                    childCalls.incrementAndGet();
+                    reply = childrenReply;
+                }
+                responseObserver.onNext(reply);
+                responseObserver.onCompleted();
+            }
+        };
+
+        try (InProcessGalaxy g = InProcessGalaxy.start(service, new AtomicReference<>());
+                GalaxyRepositoryClient client = g.client("")) {
+            List<LazyBrowseNode> roots = client.browse();
+            LazyBrowseNode root = roots.get(0);
+
+            int parallelism = 10;
+            ExecutorService pool = Executors.newFixedThreadPool(parallelism);
+            try {
+                CountDownLatch ready = new CountDownLatch(parallelism);
+                List<Future<Void>> futures = new ArrayList<>();
+                for (int i = 0; i < parallelism; i++) {
+                    futures.add(pool.submit(() -> {
+                        ready.countDown();
+                        root.expand();
+                        return null;
+                    }));
+                }
+                // Wait for all callers to be in flight, then release the leader.
+                assertTrue(ready.await(5, TimeUnit.SECONDS), "expander threads did not start");
+                // Readers must not be blocked by an in-flight expand; this should not deadlock
+                // and should return the pre-expand state.
+                assertFalse(root.isExpanded());
+                assertEquals(0, root.getChildren().size());
+                release.countDown();
+
+                for (Future<Void> f : futures) {
+                    f.get(10, TimeUnit.SECONDS);
+                }
+            } finally {
+                pool.shutdownNow();
+            }
+
+            assertTrue(root.isExpanded());
+            assertEquals(1, root.getChildren().size());
+            // Exactly one expand RPC was issued even though many callers raced.
+            assertEquals(1, childCalls.get());
+            // 1 roots fetch + exactly 1 expand fetch.
+            assertEquals(2, service.calls.size());
+        }
+    }
+
+    @Test
+    void browseWithFilterForwardsToRequest() throws Exception {
+        BrowseChildrenService service = new BrowseChildrenService();
+        // Default reply is empty; only the request shape matters here.
+        try (InProcessGalaxy g = InProcessGalaxy.start(service, new AtomicReference<>());
+                GalaxyRepositoryClient client = g.client("")) {
+            client.browse(BrowseChildrenOptions.builder()
+                    .tagNameGlob("Mixer*")
+                    .alarmBearingOnly(true)
+                    .build());
+        }
+
+        assertEquals(1, service.calls.size());
+        BrowseChildrenRequest request = service.calls.get(0);
+        assertEquals("Mixer*", request.getTagNameGlob());
+        assertTrue(request.getAlarmBearingOnly());
+    }
+
+    private static GalaxyObject obj(int id, String tag, boolean isArea) {
+        return GalaxyObject.newBuilder()
+                .setGobjectId(id)
+                .setTagName(tag)
+                .setBrowseName(tag)
+                .setIsArea(isArea)
+                .build();
+    }
+
+    private static BrowseChildrenReply browseReply(
+            List<GalaxyObject> children,
+            List<Boolean> childHasChildren,
+            long cacheSequence,
+            String nextPageToken) {
+        BrowseChildrenReply.Builder b = BrowseChildrenReply.newBuilder()
+                .setTotalChildCount(children.size())
+                .setCacheSequence(cacheSequence)
+                .setNextPageToken(nextPageToken);
+        b.addAllChildren(children);
+        b.addAllChildHasChildren(childHasChildren);
+        return b.build();
+    }
+
+    private static class BrowseChildrenService extends TestService {
+        final List<BrowseChildrenRequest> calls =
+                Collections.synchronizedList(new CopyOnWriteArrayList<>());
+        final Queue<BrowseChildrenReply> replies = new ArrayDeque<>();
+        final Queue<Throwable> errors = new ArrayDeque<>();
+
+        @Override
+        public void browseChildren(
+                BrowseChildrenRequest request, StreamObserver<BrowseChildrenReply> responseObserver) {
+            calls.add(request);
+            BrowseChildrenReply reply;
+            Throwable err;
+            synchronized (this) {
+                // Prefer queued replies first; once they're exhausted, fall through to any
+                // queued error. This matches the .NET fake's ordering used by parity tests.
+                reply = replies.poll();
+                err = reply == null ? errors.poll() : null;
+            }
+            if (err != null) {
+                responseObserver.onError(err);
+                return;
+            }
+            if (reply == null) {
+                reply = BrowseChildrenReply.getDefaultInstance();
+            }
+            responseObserver.onNext(reply);
+            responseObserver.onCompleted();
+        }
+    }
+
     private abstract static class TestService extends GalaxyRepositoryGrpc.GalaxyRepositoryImplBase {
         @Override
         public void testConnection(

clients/java/zb-mom-ww-mxgateway-client/src/test/java/com/zb/mom/ww/mxgateway/client/MxGatewayClientSessionTests.java

@@ -27,7 +27,10 @@ import mxaccess_gateway.v1.MxAccessGatewayGrpc;
 import mxaccess_gateway.v1.MxaccessGateway.ActiveAlarmSnapshot;
 import mxaccess_gateway.v1.MxaccessGateway.AddItemReply;
 import mxaccess_gateway.v1.MxaccessGateway.AlarmConditionState;
+import mxaccess_gateway.v1.MxaccessGateway.AlarmFeedMessage;
+import mxaccess_gateway.v1.MxaccessGateway.AlarmTransitionKind;
 import mxaccess_gateway.v1.MxaccessGateway.BulkSubscribeReply;
+import mxaccess_gateway.v1.MxaccessGateway.OnAlarmTransitionEvent;
 import mxaccess_gateway.v1.MxaccessGateway.CloseSessionReply;
 import mxaccess_gateway.v1.MxaccessGateway.CloseSessionRequest;
 import mxaccess_gateway.v1.MxaccessGateway.MxCommandKind;
@@ -41,6 +44,7 @@ import mxaccess_gateway.v1.MxaccessGateway.ProtocolStatusCode;
 import mxaccess_gateway.v1.MxaccessGateway.QueryActiveAlarmsRequest;
 import mxaccess_gateway.v1.MxaccessGateway.RegisterReply;
 import mxaccess_gateway.v1.MxaccessGateway.SessionState;
+import mxaccess_gateway.v1.MxaccessGateway.StreamAlarmsRequest;
 import mxaccess_gateway.v1.MxaccessGateway.StreamEventsRequest;
 import mxaccess_gateway.v1.MxaccessGateway.SubscribeResult;
 import org.junit.jupiter.api.Test;
@@ -268,6 +272,100 @@ final class MxGatewayClientSessionTests {
         }
     }
 
+    @Test
+    void streamAlarmsForwardsRequestAndStreamsAlarmFeedMessages() throws Exception {
+        AtomicReference<StreamAlarmsRequest> streamRequest = new AtomicReference<>();
+        CountDownLatch serverCancelled = new CountDownLatch(1);
+        TestGatewayService service = new TestGatewayService() {
+            @Override
+            public void streamAlarms(
+                    StreamAlarmsRequest request, StreamObserver<AlarmFeedMessage> responseObserver) {
+                streamRequest.set(request);
+                ServerCallStreamObserver<AlarmFeedMessage> server =
+                        (ServerCallStreamObserver<AlarmFeedMessage>) responseObserver;
+                server.setOnCancelHandler(serverCancelled::countDown);
+                // Active-alarm snapshot, snapshot-complete sentinel, then a
+                // transition — mirrors the shape of a real alarm feed open.
+                server.onNext(AlarmFeedMessage.newBuilder()
+                        .setActiveAlarm(ActiveAlarmSnapshot.newBuilder()
+                                .setAlarmFullReference("Tank01.Level.HiHi")
+                                .setCurrentState(AlarmConditionState.ALARM_CONDITION_STATE_ACTIVE)
+                                .setSeverity(700))
+                        .build());
+                server.onNext(AlarmFeedMessage.newBuilder().setSnapshotComplete(true).build());
+                server.onNext(AlarmFeedMessage.newBuilder()
+                        .setTransition(OnAlarmTransitionEvent.newBuilder()
+                                .setAlarmFullReference("Tank01.Level.HiHi")
+                                .setTransitionKind(AlarmTransitionKind.ALARM_TRANSITION_KIND_ACKNOWLEDGE)
+                                .setSeverity(700))
+                        .build());
+                // Note: we deliberately do NOT call onCompleted() so the call
+                // remains open for the cancellation assertion below.
+            }
+        };
+
+        try (InProcessGateway gateway = InProcessGateway.start(service, new AtomicReference<>());
+                MxGatewayClient client = gateway.client("", Duration.ofSeconds(5))) {
+            java.util.List<AlarmFeedMessage> received = new java.util.ArrayList<>();
+            AtomicReference<Throwable> errorRef = new AtomicReference<>();
+            CountDownLatch threeReceived = new CountDownLatch(3);
+
+            StreamAlarmsRequest request = StreamAlarmsRequest.newBuilder()
+                    .setAlarmFilterPrefix("Tank01")
+                    .build();
+
+            MxGatewayAlarmFeedSubscription subscription = client.streamAlarms(
+                    request,
+                    new StreamObserver<>() {
+                        @Override
+                        public void onNext(AlarmFeedMessage value) {
+                            received.add(value);
+                            threeReceived.countDown();
+                        }
+
+                        @Override
+                        public void onError(Throwable t) {
+                            errorRef.set(t);
+                        }
+
+                        @Override
+                        public void onCompleted() {
+                        }
+                    });
+
+            assertTrue(threeReceived.await(5, TimeUnit.SECONDS),
+                    "expected three alarm feed messages within 5s");
+
+            // The request shape (filter prefix in particular) must reach the
+            // server — proves MxGatewayClient.streamAlarms calls the production
+            // subscription.wrap(observer) glue and not a CLI override.
+            assertNotNull(streamRequest.get());
+            assertEquals("Tank01", streamRequest.get().getAlarmFilterPrefix());
+
+            // Order and payload-case must be preserved (the wrapping observer
+            // is just a pass-through).
+            assertEquals(3, received.size());
+            assertEquals(AlarmFeedMessage.PayloadCase.ACTIVE_ALARM, received.get(0).getPayloadCase());
+            assertEquals(
+                    "Tank01.Level.HiHi",
+                    received.get(0).getActiveAlarm().getAlarmFullReference());
+            assertEquals(AlarmFeedMessage.PayloadCase.SNAPSHOT_COMPLETE, received.get(1).getPayloadCase());
+            assertEquals(AlarmFeedMessage.PayloadCase.TRANSITION, received.get(2).getPayloadCase());
+            assertEquals(
+                    AlarmTransitionKind.ALARM_TRANSITION_KIND_ACKNOWLEDGE,
+                    received.get(2).getTransition().getTransitionKind());
+
+            // No error expected before cancellation — proves the wrapping
+            // observer forwarded only data, not a synthetic error.
+            assertNull(errorRef.get(), "no error expected before cancellation");
+
+            // Cancellation must propagate to the underlying gRPC call.
+            subscription.cancel();
+            assertTrue(serverCancelled.await(5, TimeUnit.SECONDS),
+                    "server should observe RPC cancellation after subscription.cancel()");
+        }
+    }
+
     @Test
     void commandFailureKeepsRawReply() throws Exception {
         TestGatewayService service = new TestGatewayService() {

clients/java/zb-mom-ww-mxgateway-client/src/test/java/com/zb/mom/ww/mxgateway/client/MxGatewayClientTlsTests.java

@@ -0,0 +1,198 @@
+package com.zb.mom.ww.mxgateway.client;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import io.grpc.ManagedChannel;
+import io.grpc.Server;
+import io.grpc.StatusRuntimeException;
+import io.grpc.netty.shaded.io.grpc.netty.GrpcSslContexts;
+import io.grpc.netty.shaded.io.grpc.netty.NettyServerBuilder;
+import io.grpc.stub.StreamObserver;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.nio.file.Files;
+import java.security.KeyStore;
+import java.security.PrivateKey;
+import java.security.cert.Certificate;
+import java.security.cert.X509Certificate;
+import java.time.Duration;
+import java.util.Base64;
+import java.util.concurrent.TimeUnit;
+import javax.net.ssl.SSLException;
+import mxaccess_gateway.v1.MxAccessGatewayGrpc;
+import mxaccess_gateway.v1.MxaccessGateway.OpenSessionReply;
+import mxaccess_gateway.v1.MxaccessGateway.OpenSessionRequest;
+import mxaccess_gateway.v1.MxaccessGateway.ProtocolStatus;
+import mxaccess_gateway.v1.MxaccessGateway.ProtocolStatusCode;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Verifies that the Java client connects to a Netty TLS server with a
+ * self-signed certificate when no CA is pinned (lenient default), and that
+ * setting {@code requireCertificateValidation(true)} causes a TLS failure.
+ *
+ * <p>A self-signed certificate is generated using {@code keytool} (always
+ * available in the JDK) to avoid dependencies on internal JDK APIs or
+ * BouncyCastle, and so the test works on all JDK versions used by the project.
+ */
+final class MxGatewayClientTlsTests {
+
+    private Server server;
+    private int port;
+    private File certPemFile;
+    private File keyPemFile;
+    private File keystoreFile;
+
+    @BeforeEach
+    void startTlsServer() throws Exception {
+        keystoreFile = File.createTempFile("gw-test-ks", ".p12");
+        certPemFile = File.createTempFile("gw-test-cert", ".pem");
+        keyPemFile = File.createTempFile("gw-test-key", ".pem");
+
+        // keytool refuses to write to a pre-existing (even empty) file; delete it first.
+        keystoreFile.delete();
+
+        // Use keytool to generate a self-signed PKCS12 keystore.
+        String keytool = ProcessHandle.current().info().command()
+                .map(cmd -> cmd.replace("java", "keytool"))
+                .orElse("keytool");
+        // Fall back to just "keytool" on PATH if the resolved path doesn't exist.
+        if (!new File(keytool).exists()) {
+            keytool = "keytool";
+        }
+        Process p = new ProcessBuilder(
+                keytool,
+                "-genkeypair",
+                "-alias", "server",
+                "-keyalg", "RSA",
+                "-keysize", "2048",
+                "-sigalg", "SHA256withRSA",
+                "-validity", "1",
+                "-dname", "CN=localhost",
+                "-storetype", "PKCS12",
+                "-storepass", "changeit",
+                "-keypass", "changeit",
+                "-keystore", keystoreFile.getAbsolutePath())
+                .redirectErrorStream(true)
+                .start();
+        int exit = p.waitFor();
+        if (exit != 0) {
+            String out = new String(p.getInputStream().readAllBytes());
+            throw new IllegalStateException("keytool failed (exit " + exit + "): " + out);
+        }
+
+        // Export cert and private key from the PKCS12 keystore to PEM files.
+        KeyStore ks = KeyStore.getInstance("PKCS12");
+        try (var is = Files.newInputStream(keystoreFile.toPath())) {
+            ks.load(is, "changeit".toCharArray());
+        }
+        X509Certificate cert = (X509Certificate) ks.getCertificate("server");
+        PrivateKey privateKey = (PrivateKey) ks.getKey("server", "changeit".toCharArray());
+
+        try (FileOutputStream out = new FileOutputStream(certPemFile)) {
+            out.write("-----BEGIN CERTIFICATE-----\n".getBytes());
+            out.write(Base64.getMimeEncoder(64, new byte[]{'\n'}).encode(cert.getEncoded()));
+            out.write("\n-----END CERTIFICATE-----\n".getBytes());
+        }
+        try (FileOutputStream out = new FileOutputStream(keyPemFile)) {
+            out.write("-----BEGIN PRIVATE KEY-----\n".getBytes());
+            out.write(Base64.getMimeEncoder(64, new byte[]{'\n'}).encode(privateKey.getEncoded()));
+            out.write("\n-----END PRIVATE KEY-----\n".getBytes());
+        }
+
+        server = NettyServerBuilder
+                .forAddress(new InetSocketAddress("127.0.0.1", 0))
+                .sslContext(GrpcSslContexts.forServer(certPemFile, keyPemFile).build())
+                .addService(new MinimalGatewayService())
+                .build()
+                .start();
+        port = server.getPort();
+    }
+
+    @AfterEach
+    void stopTlsServer() throws InterruptedException {
+        if (server != null) {
+            server.shutdown();
+            server.awaitTermination(5, TimeUnit.SECONDS);
+        }
+        if (certPemFile != null) {
+            certPemFile.delete();
+        }
+        if (keyPemFile != null) {
+            keyPemFile.delete();
+        }
+        if (keystoreFile != null) {
+            keystoreFile.delete();
+        }
+    }
+
+    @Test
+    void connectsToSelfSignedServer_WhenRequireCertificateValidationIsFalse() throws SSLException {
+        // Default options — requireCertificateValidation defaults to false.
+        MxGatewayClientOptions options = MxGatewayClientOptions.builder()
+                .endpoint("127.0.0.1:" + port)
+                .apiKey("test-key")
+                .connectTimeout(Duration.ofSeconds(5))
+                .callTimeout(Duration.ofSeconds(5))
+                .build();
+
+        ManagedChannel channel = MxGatewayClient.createChannelForTests(options);
+        try {
+            MxAccessGatewayGrpc.MxAccessGatewayBlockingStub stub =
+                    MxAccessGatewayGrpc.newBlockingStub(channel);
+            OpenSessionReply reply = stub.openSession(
+                    OpenSessionRequest.newBuilder()
+                            .setClientSessionName("tls-test")
+                            .build());
+            assertTrue(reply.getProtocolStatus().getCode()
+                    == ProtocolStatusCode.PROTOCOL_STATUS_CODE_OK);
+        } finally {
+            channel.shutdownNow();
+        }
+    }
+
+    @Test
+    void failsToConnect_WhenRequireCertificateValidationIsTrue() throws SSLException {
+        MxGatewayClientOptions options = MxGatewayClientOptions.builder()
+                .endpoint("127.0.0.1:" + port)
+                .apiKey("test-key")
+                .requireCertificateValidation(true)
+                .connectTimeout(Duration.ofSeconds(5))
+                .callTimeout(Duration.ofSeconds(5))
+                .build();
+
+        ManagedChannel channel = MxGatewayClient.createChannelForTests(options);
+        try {
+            MxAccessGatewayGrpc.MxAccessGatewayBlockingStub stub =
+                    MxAccessGatewayGrpc.newBlockingStub(channel);
+            assertThrows(StatusRuntimeException.class, () ->
+                    stub.openSession(OpenSessionRequest.newBuilder()
+                            .setClientSessionName("tls-strict-test")
+                            .build()));
+        } finally {
+            channel.shutdownNow();
+        }
+    }
+
+    /** Minimal gateway stub that succeeds any OpenSession call. */
+    private static final class MinimalGatewayService
+            extends MxAccessGatewayGrpc.MxAccessGatewayImplBase {
+        @Override
+        public void openSession(
+                OpenSessionRequest request,
+                StreamObserver<OpenSessionReply> responseObserver) {
+            responseObserver.onNext(OpenSessionReply.newBuilder()
+                    .setSessionId("tls-test-session")
+                    .setProtocolStatus(ProtocolStatus.newBuilder()
+                            .setCode(ProtocolStatusCode.PROTOCOL_STATUS_CODE_OK)
+                            .build())
+                    .build());
+            responseObserver.onCompleted();
+        }
+    }
+}

clients/java/zb-mom-ww-mxgateway-client/src/test/java/com/zb/mom/ww/mxgateway/client/MxGatewayStreamSubscriptionContractTests.java

@@ -0,0 +1,275 @@
+package com.zb.mom.ww.mxgateway.client;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import galaxy_repository.v1.GalaxyRepositoryOuterClass.DeployEvent;
+import galaxy_repository.v1.GalaxyRepositoryOuterClass.WatchDeployEventsRequest;
+import io.grpc.stub.ClientCallStreamObserver;
+import io.grpc.stub.ClientResponseObserver;
+import io.grpc.stub.StreamObserver;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicReference;
+import mxaccess_gateway.v1.MxaccessGateway.ActiveAlarmSnapshot;
+import mxaccess_gateway.v1.MxaccessGateway.AlarmFeedMessage;
+import mxaccess_gateway.v1.MxaccessGateway.MxEvent;
+import mxaccess_gateway.v1.MxaccessGateway.QueryActiveAlarmsRequest;
+import mxaccess_gateway.v1.MxaccessGateway.StreamAlarmsRequest;
+import mxaccess_gateway.v1.MxaccessGateway.StreamEventsRequest;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Lifecycle / cancellation contract tests applied uniformly to each of the
+ * four subscription classes that extend {@link MxGatewayStreamSubscription}.
+ *
+ * <p>Locks in the Client.Java-036 refactor: every subclass must exhibit the
+ * same behaviour for (a) cancel-before-beforeStart eagerly cancelling the
+ * stream once it attaches, (b) cancel-after-beforeStart forwarding directly
+ * to the stream, (c) the cancel message matching the subclass's documented
+ * value, (d) {@code close()} delegating to {@code cancel()}, and (e) the
+ * wrapping observer forwarding {@code onNext}/{@code onError}/{@code onCompleted}
+ * to the caller's observer.
+ */
+final class MxGatewayStreamSubscriptionContractTests {
+
+    @Test
+    void cancelBeforeBeforeStartCancelsStreamWhenItAttaches_eventSubscription() {
+        runCancelBeforeBeforeStartTest(new MxGatewayEventSubscription(), "client cancelled event stream");
+    }
+
+    @Test
+    void cancelBeforeBeforeStartCancelsStreamWhenItAttaches_alarmFeedSubscription() {
+        runCancelBeforeBeforeStartTest(
+                new MxGatewayAlarmFeedSubscription(), "client cancelled alarm feed");
+    }
+
+    @Test
+    void cancelBeforeBeforeStartCancelsStreamWhenItAttaches_activeAlarmsSubscription() {
+        runCancelBeforeBeforeStartTest(
+                new MxGatewayActiveAlarmsSubscription(), "client cancelled active-alarms query");
+    }
+
+    @Test
+    void cancelBeforeBeforeStartCancelsStreamWhenItAttaches_deployEventSubscription() {
+        runCancelBeforeBeforeStartTest(
+                new DeployEventSubscription(), "client cancelled deploy event stream");
+    }
+
+    @Test
+    void cancelAfterBeforeStartForwardsToStream_eventSubscription() {
+        runCancelAfterBeforeStartTest(new MxGatewayEventSubscription(), "client cancelled event stream");
+    }
+
+    @Test
+    void cancelAfterBeforeStartForwardsToStream_alarmFeedSubscription() {
+        runCancelAfterBeforeStartTest(
+                new MxGatewayAlarmFeedSubscription(), "client cancelled alarm feed");
+    }
+
+    @Test
+    void cancelAfterBeforeStartForwardsToStream_activeAlarmsSubscription() {
+        runCancelAfterBeforeStartTest(
+                new MxGatewayActiveAlarmsSubscription(), "client cancelled active-alarms query");
+    }
+
+    @Test
+    void cancelAfterBeforeStartForwardsToStream_deployEventSubscription() {
+        runCancelAfterBeforeStartTest(
+                new DeployEventSubscription(), "client cancelled deploy event stream");
+    }
+
+    @Test
+    void closeDelegatesToCancel_eventSubscription() {
+        runCloseDelegatesToCancelTest(new MxGatewayEventSubscription());
+    }
+
+    @Test
+    void closeDelegatesToCancel_alarmFeedSubscription() {
+        runCloseDelegatesToCancelTest(new MxGatewayAlarmFeedSubscription());
+    }
+
+    @Test
+    void closeDelegatesToCancel_activeAlarmsSubscription() {
+        runCloseDelegatesToCancelTest(new MxGatewayActiveAlarmsSubscription());
+    }
+
+    @Test
+    void closeDelegatesToCancel_deployEventSubscription() {
+        runCloseDelegatesToCancelTest(new DeployEventSubscription());
+    }
+
+    @Test
+    void wrappedObserverForwardsOnNextOnErrorOnCompleted_eventSubscription() {
+        MxEvent event = MxEvent.newBuilder().setWorkerSequence(7L).build();
+        runForwardingTest(new MxGatewayEventSubscription(), event);
+    }
+
+    @Test
+    void wrappedObserverForwardsOnNextOnErrorOnCompleted_alarmFeedSubscription() {
+        AlarmFeedMessage msg = AlarmFeedMessage.newBuilder().setSnapshotComplete(true).build();
+        runForwardingTest(new MxGatewayAlarmFeedSubscription(), msg);
+    }
+
+    @Test
+    void wrappedObserverForwardsOnNextOnErrorOnCompleted_activeAlarmsSubscription() {
+        ActiveAlarmSnapshot snap = ActiveAlarmSnapshot.newBuilder()
+                .setAlarmFullReference("ref")
+                .setSeverity(500)
+                .build();
+        runForwardingTest(new MxGatewayActiveAlarmsSubscription(), snap);
+    }
+
+    @Test
+    void wrappedObserverForwardsOnNextOnErrorOnCompleted_deployEventSubscription() {
+        DeployEvent ev = DeployEvent.newBuilder().setSequence(1L).build();
+        runForwardingTest(new DeployEventSubscription(), ev);
+    }
+
+    private static <Req, Resp> void runCancelBeforeBeforeStartTest(
+            MxGatewayStreamSubscription<Req, Resp> subscription, String expectedMessage) {
+        ClientResponseObserver<Req, Resp> wrapped = subscription.wrap(new NoopObserver<>());
+        RecordingClientCallStreamObserver<Req> stream = new RecordingClientCallStreamObserver<>();
+
+        subscription.cancel();
+        wrapped.beforeStart(stream);
+
+        assertTrue(stream.cancelled, "stream should have been cancelled by beforeStart after prior cancel()");
+        assertEquals(expectedMessage, stream.cancelMessage);
+    }
+
+    private static <Req, Resp> void runCancelAfterBeforeStartTest(
+            MxGatewayStreamSubscription<Req, Resp> subscription, String expectedMessage) {
+        ClientResponseObserver<Req, Resp> wrapped = subscription.wrap(new NoopObserver<>());
+        RecordingClientCallStreamObserver<Req> stream = new RecordingClientCallStreamObserver<>();
+
+        wrapped.beforeStart(stream);
+        assertFalse(stream.cancelled, "stream should not be cancelled before cancel() is called");
+        subscription.cancel();
+
+        assertTrue(stream.cancelled, "stream should have been cancelled by direct cancel()");
+        assertEquals(expectedMessage, stream.cancelMessage);
+    }
+
+    private static <Req, Resp> void runCloseDelegatesToCancelTest(
+            MxGatewayStreamSubscription<Req, Resp> subscription) {
+        ClientResponseObserver<Req, Resp> wrapped = subscription.wrap(new NoopObserver<>());
+        RecordingClientCallStreamObserver<Req> stream = new RecordingClientCallStreamObserver<>();
+
+        wrapped.beforeStart(stream);
+        subscription.close();
+
+        assertTrue(stream.cancelled, "close() should delegate to cancel()");
+    }
+
+    private static <Req, Resp> void runForwardingTest(
+            MxGatewayStreamSubscription<Req, Resp> subscription, Resp value) {
+        List<Resp> received = new ArrayList<>();
+        AtomicReference<Throwable> errorRef = new AtomicReference<>();
+        AtomicReference<Boolean> completed = new AtomicReference<>(false);
+
+        StreamObserver<Resp> caller = new StreamObserver<>() {
+            @Override
+            public void onNext(Resp v) {
+                received.add(v);
+            }
+
+            @Override
+            public void onError(Throwable t) {
+                errorRef.set(t);
+            }
+
+            @Override
+            public void onCompleted() {
+                completed.set(true);
+            }
+        };
+
+        ClientResponseObserver<Req, Resp> wrapped = subscription.wrap(caller);
+        RecordingClientCallStreamObserver<Req> stream = new RecordingClientCallStreamObserver<>();
+        wrapped.beforeStart(stream);
+
+        wrapped.onNext(value);
+        IllegalStateException boom = new IllegalStateException("boom");
+        wrapped.onError(boom);
+        wrapped.onCompleted();
+
+        assertEquals(1, received.size());
+        assertEquals(value, received.get(0));
+        assertNotNull(errorRef.get());
+        assertEquals(boom, errorRef.get());
+        assertTrue(completed.get());
+    }
+
+    private static final class NoopObserver<T> implements StreamObserver<T> {
+        @Override
+        public void onNext(T value) {
+        }
+
+        @Override
+        public void onError(Throwable t) {
+        }
+
+        @Override
+        public void onCompleted() {
+        }
+    }
+
+    private static final class RecordingClientCallStreamObserver<T> extends ClientCallStreamObserver<T> {
+        boolean cancelled;
+        String cancelMessage;
+
+        @Override
+        public boolean isReady() {
+            return true;
+        }
+
+        @Override
+        public void setOnReadyHandler(Runnable onReadyHandler) {
+        }
+
+        @Override
+        public void disableAutoInboundFlowControl() {
+        }
+
+        @Override
+        public void request(int count) {
+        }
+
+        @Override
+        public void setMessageCompression(boolean enable) {
+        }
+
+        @Override
+        public void cancel(String message, Throwable cause) {
+            cancelled = true;
+            cancelMessage = message;
+        }
+
+        @Override
+        public void onNext(T value) {
+        }
+
+        @Override
+        public void onError(Throwable error) {
+        }
+
+        @Override
+        public void onCompleted() {
+        }
+    }
+
+    // Compile-time guarantee that the parameter types still match the
+    // generic bounds — catches a regression where a subclass changes its
+    // request/response types out from under the shared base.
+    @SuppressWarnings("unused")
+    private static void typeBoundsCheck() {
+        MxGatewayStreamSubscription<StreamEventsRequest, MxEvent> a = new MxGatewayEventSubscription();
+        MxGatewayStreamSubscription<StreamAlarmsRequest, AlarmFeedMessage> b = new MxGatewayAlarmFeedSubscription();
+        MxGatewayStreamSubscription<QueryActiveAlarmsRequest, ActiveAlarmSnapshot> c =
+                new MxGatewayActiveAlarmsSubscription();
+        MxGatewayStreamSubscription<WatchDeployEventsRequest, DeployEvent> d = new DeployEventSubscription();
+    }
+}

clients/python/PythonClientDesign.md

@@ -112,6 +112,28 @@ Support:
 - TLS channel with default roots,
 - custom root certificate file.
 
+### Trust posture (trust-on-first-use)
+
+The gateway can serve a self-signed certificate it generates itself (it has no
+PKI). grpc-python exposes no per-channel skip-verify hook, so the client cannot
+"accept any certificate" the way the other clients do. Instead, when the channel
+is not plaintext and neither `ca_file` nor `require_certificate_validation` is
+set, the TLS default is **trust-on-first-use**: the client fetches the server's
+presented certificate once via `ssl.get_server_certificate` (an unverified
+probe), pins it as the channel's only trust root, and — because the generated
+certificate always carries a `localhost` SAN — defaults
+`grpc.ssl_target_name_override` to `localhost` when no `server_name_override` was
+supplied (tolerating dial-by-IP or a hostname mismatch). A failed probe is
+surfaced as a transport error naming the endpoint.
+
+To verify the gateway instead:
+
+- set `ca_file` to verify against a specific CA, or
+- set `require_certificate_validation=True` to verify against the system trust
+  roots.
+
+Both bypass the TOFU path.
+
 ## Streaming
 
 Expose `stream_events` as an async iterator. Canceling the task should cancel

clients/python/README.md

@@ -138,6 +138,49 @@ The methods return native Python types (`bool`, `datetime | None`, and a
 into the hierarchy without learning the underlying stub class. The
 service requires the `metadata:read` scope on the API key.
 
+### Browsing lazily
+
+For UI trees or OPC UA bridges, use `browse_children` to walk one level at a
+time instead of loading the full hierarchy with `discover_hierarchy`. Pass an
+empty request for root objects; subsequent calls set `parent_gobject_id`,
+`parent_tag_name`, or `parent_contained_path`. Filter fields match
+`DiscoverHierarchy`. Each response pairs `children` with `child_has_children` so
+you know which nodes to expand. See
+[Galaxy Repository](../../docs/GalaxyRepository.md#browsechildren) for full
+request and filter semantics.
+
+```python
+from zb_mom_ww_mxgateway.generated import galaxy_repository_pb2 as galaxy_pb2
+
+reply = await galaxy.browse_children(galaxy_pb2.BrowseChildrenRequest())
+for child, has_children in zip(reply.children, reply.child_has_children):
+    print(child.tag_name, "expand=" + str(has_children))
+```
+
+#### High-level walker
+
+For UI trees, the client provides a `LazyBrowseNode` walker that handles
+sibling pagination and the `child_has_children` hint for you:
+
+```python
+async with await GalaxyRepositoryClient.connect(
+    endpoint="localhost:5000",
+    api_key="<gateway-api-key>",
+    plaintext=True,
+) as galaxy:
+    roots = await galaxy.browse()
+    for root in roots:
+        if root.has_children_hint:
+            await root.expand()
+        for child in root.children:
+            kind = "has children" if child.has_children_hint else "leaf"
+            print(f"{child.object.tag_name} ({kind})")
+```
+
+`expand` is idempotent — calling it twice fires only one RPC,
+and is safe under concurrent callers. To refresh after a Galaxy redeploy, call
+`browse` again from the root.
+
 ### Watching deploy events
 
 `GalaxyRepositoryClient.watch_deploy_events` opens a server-streaming
@@ -187,6 +230,17 @@ The client supports plaintext channels for local development, TLS with system
 roots, TLS with a custom `ca_file`, and an optional test server name override.
 API keys are redacted from option repr output and CLI error output.
 
+The gateway can auto-generate its own self-signed certificate (it has no PKI).
+grpc-python has no per-channel skip-verify, so the lenient TLS default is
+**trust-on-first-use**: with no `ca_file` and `require_certificate_validation`
+left `False`, the client fetches the gateway's presented certificate once
+(unverified) and pins it for the channel, defaulting the SNI/target-name override
+to `localhost` (the generated certificate always carries a `localhost` SAN) when
+none was supplied. To verify instead, pass `ca_file` to verify against a specific
+CA, or set `require_certificate_validation=True` to verify against the system
+trust roots. See
+[Gateway Configuration](../../docs/GatewayConfiguration.md#automatic-self-signed-certificate).
+
 ## CLI
 
 The CLI emits deterministic JSON for automation:
@@ -198,8 +252,8 @@ mxgw-py register --session-id <id> --client-name python-client --json
 mxgw-py add-item --session-id <id> --server-handle 1 --item Object.Attribute --json
 mxgw-py advise --session-id <id> --server-handle 1 --item-handle 2 --json
 mxgw-py stream-events --session-id <id> --max-events 1 --json
-mxgw-py stream-alarms --session-id <id> --max-messages 1 --json
-mxgw-py acknowledge-alarm --session-id <id> --alarm-reference "\\Galaxy\Area001.Pump001.PumpFault" --json
+mxgw-py stream-alarms --max-messages 1 --json
+mxgw-py acknowledge-alarm --reference "\\Galaxy\Area001.Pump001.PumpFault" --json
 mxgw-py write --session-id <id> --server-handle 1 --item-handle 2 --type int32 --value 123 --json
 ```
 
@@ -225,6 +279,19 @@ $env:MXGATEWAY_TEST_ITEM = 'Object.Attribute'
 mxgw-py smoke --endpoint $env:MXGATEWAY_ENDPOINT --plaintext --api-key-env MXGATEWAY_API_KEY --item $env:MXGATEWAY_TEST_ITEM --json
 ```
 
+## Installing from the Gitea PyPI Feed
+
+The client publishes to the internal Gitea PyPI feed:
+
+````bash
+pip install \
+    --index-url https://gitea.dohertylan.com/api/packages/dohertj2/pypi/simple/ \
+    zb-mom-ww-mxaccess-gateway-client
+````
+
+If you need authentication (private feed), use `--extra-index-url` and either
+a `~/.netrc` entry or `PIP_INDEX_URL=https://<user>:<token>@gitea.dohertylan.com/...`.
+
 ## Related Documentation
 
 - [Client Packaging](../../docs/ClientPackaging.md)

clients/python/pyproject.toml

@@ -13,12 +13,35 @@ dependencies = [
   "grpcio>=1.80,<2",
   "protobuf>=6.33,<7",
 ]
+authors = [
+  { name = "Joseph Doherty" },
+]
+license = { text = "Proprietary" }
+keywords = ["mxaccess", "mxgateway", "grpc", "client", "archestra"]
+classifiers = [
+  "Development Status :: 3 - Alpha",
+  "License :: Other/Proprietary License",
+  "Programming Language :: Python :: 3",
+  "Programming Language :: Python :: 3.12",
+  "Programming Language :: Python :: 3.13",
+  "Topic :: System :: Distributed Computing",
+  "Topic :: Software Development :: Libraries :: Python Modules",
+  "Intended Audience :: Developers",
+  "Operating System :: OS Independent",
+]
+
+[project.urls]
+Homepage = "https://gitea.dohertylan.com/dohertj2/mxaccessgw"
+Repository = "https://gitea.dohertylan.com/dohertj2/mxaccessgw"
+Issues = "https://gitea.dohertylan.com/dohertj2/mxaccessgw/issues"
 
 [project.optional-dependencies]
 dev = [
   "grpcio-tools>=1.80,<2",
   "pytest>=9,<10",
   "pytest-asyncio>=1.3,<2",
+  "build>=1.2,<2",
+  "twine>=5,<6",
 ]
 
 [project.scripts]

clients/python/src/zb_mom_ww_mxgateway/galaxy.py

@@ -21,9 +21,10 @@ from .auth import merge_metadata
 from .errors import MxGatewayError, map_rpc_error
 from .generated import galaxy_repository_pb2 as galaxy_pb
 from .generated import galaxy_repository_pb2_grpc as galaxy_pb_grpc
-from .options import ClientOptions, create_channel
+from .options import BrowseChildrenOptions, ClientOptions, create_channel
 
 _DISCOVER_HIERARCHY_PAGE_SIZE = 5000
+_BROWSE_CHILDREN_PAGE_SIZE = 500
 
 
 class GalaxyRepositoryClient:
@@ -139,6 +140,89 @@ class GalaxyRepositoryClient:
                 )
             seen_page_tokens.add(page_token)
 
+    async def browse_children_raw(
+        self, request: galaxy_pb.BrowseChildrenRequest
+    ) -> galaxy_pb.BrowseChildrenReply:
+        """Issue one BrowseChildren RPC and return the raw reply.
+
+        Lower-level escape hatch for callers that need direct page-token control
+        or do not want LazyBrowseNode wrapping. Most callers should use
+        :py:meth:`browse` and :py:meth:`LazyBrowseNode.expand` instead.
+        """
+
+        return await self._unary(
+            "browse children",
+            self.raw_stub.BrowseChildren,
+            request,
+        )
+
+    async def browse(
+        self,
+        options: BrowseChildrenOptions | None = None,
+    ) -> list["LazyBrowseNode"]:
+        """Return the root browse nodes for lazy hierarchy traversal.
+
+        Each returned ``LazyBrowseNode`` wraps a Galaxy object whose direct
+        children can be loaded on demand by ``await node.expand()``.
+        """
+
+        effective = options or BrowseChildrenOptions()
+        return [
+            node
+            async for node in self._iter_browse_children(
+                parent_gobject_id=None,
+                options=effective,
+            )
+        ]
+
+    async def _iter_browse_children(
+        self,
+        *,
+        parent_gobject_id: int | None,
+        options: BrowseChildrenOptions,
+    ) -> AsyncIterator["LazyBrowseNode"]:
+        page_token = ""
+        seen_page_tokens: set[str] = set()
+        while True:
+            request = galaxy_pb.BrowseChildrenRequest(
+                page_size=_BROWSE_CHILDREN_PAGE_SIZE,
+                page_token=page_token,
+                alarm_bearing_only=options.alarm_bearing_only,
+                historized_only=options.historized_only,
+            )
+            if parent_gobject_id is not None:
+                request.parent_gobject_id = parent_gobject_id
+            if options.category_ids:
+                request.category_ids.extend(options.category_ids)
+            if options.template_chain_contains:
+                request.template_chain_contains.extend(options.template_chain_contains)
+            if options.tag_name_glob:
+                request.tag_name_glob = options.tag_name_glob
+            if options.include_attributes is not None:
+                request.include_attributes = options.include_attributes
+
+            reply = await self._unary(
+                "browse children",
+                self.raw_stub.BrowseChildren,
+                request,
+            )
+
+            for index, obj in enumerate(reply.children):
+                hint = (
+                    index < len(reply.child_has_children)
+                    and bool(reply.child_has_children[index])
+                )
+                yield LazyBrowseNode(self, obj, hint, options)
+
+            page_token = reply.next_page_token
+            if not page_token:
+                return
+            if page_token in seen_page_tokens:
+                raise MxGatewayError(
+                    f"galaxy browse children returned repeated page token {page_token!r}"
+                )
+            seen_page_tokens.add(page_token)
+
     def watch_deploy_events(
         self,
         last_seen_deploy_time: datetime | None = None,
@@ -202,6 +286,67 @@ class GalaxyRepositoryClient:
             raise map_rpc_error(operation, error) from error
 
 
+class LazyBrowseNode:
+    """One node in a lazy-loaded Galaxy browse tree.
+
+    Calling ``expand`` once fetches direct children (paginating as needed)
+    and populates ``children``. Subsequent calls are no-ops so callers can
+    drive UI expand toggles without de-duping.
+    """
+
+    def __init__(
+        self,
+        client: "GalaxyRepositoryClient",
+        obj: galaxy_pb.GalaxyObject,
+        has_children_hint: bool,
+        options: BrowseChildrenOptions,
+    ) -> None:
+        """Initialize a node bound to its owning client and filter set."""
+        self._client = client
+        self._object = obj
+        self._has_children_hint = has_children_hint
+        self._options = options
+        self._children: list[LazyBrowseNode] = []
+        self._is_expanded = False
+        self._expand_lock = asyncio.Lock()
+
+    @property
+    def object(self) -> galaxy_pb.GalaxyObject:
+        """Return the underlying ``GalaxyObject`` proto for this node."""
+        return self._object
+
+    @property
+    def has_children_hint(self) -> bool:
+        """Return the server hint about whether this node has children."""
+        return self._has_children_hint
+
+    @property
+    def children(self) -> list["LazyBrowseNode"]:
+        """Return a copy of the loaded child nodes (empty until expanded)."""
+        return list(self._children)
+
+    @property
+    def is_expanded(self) -> bool:
+        """Return whether ``expand`` has already populated ``children``."""
+        return self._is_expanded
+
+    async def expand(self) -> None:
+        """Fetch direct children of this node; no-op on subsequent calls."""
+        if self._is_expanded:
+            return
+        async with self._expand_lock:
+            if self._is_expanded:
+                return
+            new_children: list[LazyBrowseNode] = []
+            async for child in self._client._iter_browse_children(
+                parent_gobject_id=self._object.gobject_id,
+                options=self._options,
+            ):
+                new_children.append(child)
+            self._children.extend(new_children)
+            self._is_expanded = True
+
+
 async def _canceling_iterator(call: Any) -> AsyncIterator[galaxy_pb.DeployEvent]:
     try:
         async for event in call:

clients/python/src/zb_mom_ww_mxgateway/generated/galaxy_repository_pb2.py

@@ -26,7 +26,7 @@ from google.protobuf import timestamp_pb2 as google_dot_protobuf_dot_timestamp__
 from google.protobuf import wrappers_pb2 as google_dot_protobuf_dot_wrappers__pb2
 
 
-DESCRIPTOR = _descriptor_pool.Default().AddSerializedFile(b'\n\x17galaxy_repository.proto\x12\x14galaxy_repository.v1\x1a\x1fgoogle/protobuf/timestamp.proto\x1a\x1egoogle/protobuf/wrappers.proto\"\x17\n\x15TestConnectionRequest\"!\n\x13TestConnectionReply\x12\n\n\x02ok\x18\x01 \x01(\x08\"\x1a\n\x18GetLastDeployTimeRequest\"b\n\x16GetLastDeployTimeReply\x12\x0f\n\x07present\x18\x01 \x01(\x08\x12\x37\n\x13time_of_last_deploy\x18\x02 \x01(\x0b\x32\x1a.google.protobuf.Timestamp\"\x87\x03\n\x18\x44iscoverHierarchyRequest\x12\x11\n\tpage_size\x18\x01 \x01(\x05\x12\x12\n\npage_token\x18\x02 \x01(\t\x12\x19\n\x0froot_gobject_id\x18\x03 \x01(\x05H\x00\x12\x17\n\rroot_tag_name\x18\x04 \x01(\tH\x00\x12\x1d\n\x13root_contained_path\x18\x05 \x01(\tH\x00\x12.\n\tmax_depth\x18\x06 \x01(\x0b\x32\x1b.google.protobuf.Int32Value\x12\x14\n\x0c\x63\x61tegory_ids\x18\x07 \x03(\x05\x12\x1f\n\x17template_chain_contains\x18\x08 \x03(\t\x12\x15\n\rtag_name_glob\x18\t \x01(\t\x12\x1f\n\x12include_attributes\x18\n \x01(\x08H\x01\x88\x01\x01\x12\x1a\n\x12\x61larm_bearing_only\x18\x0b \x01(\x08\x12\x17\n\x0fhistorized_only\x18\x0c \x01(\x08\x42\x06\n\x04rootB\x15\n\x13_include_attributes\"\x82\x01\n\x16\x44iscoverHierarchyReply\x12\x33\n\x07objects\x18\x01 \x03(\x0b\x32\".galaxy_repository.v1.GalaxyObject\x12\x17\n\x0fnext_page_token\x18\x02 \x01(\t\x12\x1a\n\x12total_object_count\x18\x03 \x01(\x05\"U\n\x18WatchDeployEventsRequest\x12\x39\n\x15last_seen_deploy_time\x18\x01 \x01(\x0b\x32\x1a.google.protobuf.Timestamp\"\xdd\x01\n\x0b\x44\x65ployEvent\x12\x10\n\x08sequence\x18\x01 \x01(\x04\x12/\n\x0bobserved_at\x18\x02 \x01(\x0b\x32\x1a.google.protobuf.Timestamp\x12\x37\n\x13time_of_last_deploy\x18\x03 \x01(\x0b\x32\x1a.google.protobuf.Timestamp\x12#\n\x1btime_of_last_deploy_present\x18\x04 \x01(\x08\x12\x14\n\x0cobject_count\x18\x05 \x01(\x05\x12\x17\n\x0f\x61ttribute_count\x18\x06 \x01(\x05\"\x93\x02\n\x0cGalaxyObject\x12\x12\n\ngobject_id\x18\x01 \x01(\x05\x12\x10\n\x08tag_name\x18\x02 \x01(\t\x12\x16\n\x0e\x63ontained_name\x18\x03 \x01(\t\x12\x13\n\x0b\x62rowse_name\x18\x04 \x01(\t\x12\x19\n\x11parent_gobject_id\x18\x05 \x01(\x05\x12\x0f\n\x07is_area\x18\x06 \x01(\x08\x12\x13\n\x0b\x63\x61tegory_id\x18\x07 \x01(\x05\x12\x1c\n\x14hosted_by_gobject_id\x18\x08 \x01(\x05\x12\x16\n\x0etemplate_chain\x18\t \x03(\t\x12\x39\n\nattributes\x18\n \x03(\x0b\x32%.galaxy_repository.v1.GalaxyAttribute\"\xa8\x02\n\x0fGalaxyAttribute\x12\x16\n\x0e\x61ttribute_name\x18\x01 \x01(\t\x12\x1a\n\x12\x66ull_tag_reference\x18\x02 \x01(\t\x12\x14\n\x0cmx_data_type\x18\x03 \x01(\x05\x12\x16\n\x0e\x64\x61ta_type_name\x18\x04 \x01(\t\x12\x10\n\x08is_array\x18\x05 \x01(\x08\x12\x17\n\x0f\x61rray_dimension\x18\x06 \x01(\x05\x12\x1f\n\x17\x61rray_dimension_present\x18\x07 \x01(\x08\x12\x1d\n\x15mx_attribute_category\x18\x08 \x01(\x05\x12\x1f\n\x17security_classification\x18\t \x01(\x05\x12\x15\n\ris_historized\x18\n \x01(\x08\x12\x10\n\x08is_alarm\x18\x0b \x01(\x08\x32\xcc\x03\n\x10GalaxyRepository\x12h\n\x0eTestConnection\x12+.galaxy_repository.v1.TestConnectionRequest\x1a).galaxy_repository.v1.TestConnectionReply\x12q\n\x11GetLastDeployTime\x12..galaxy_repository.v1.GetLastDeployTimeRequest\x1a,.galaxy_repository.v1.GetLastDeployTimeReply\x12q\n\x11\x44iscoverHierarchy\x12..galaxy_repository.v1.DiscoverHierarchyRequest\x1a,.galaxy_repository.v1.DiscoverHierarchyReply\x12h\n\x11WatchDeployEvents\x12..galaxy_repository.v1.WatchDeployEventsRequest\x1a!.galaxy_repository.v1.DeployEvent0\x01\x42-\xaa\x02*ZB.MOM.WW.MxGateway.Contracts.Proto.Galaxyb\x06proto3')
+DESCRIPTOR = _descriptor_pool.Default().AddSerializedFile(b'\n\x17galaxy_repository.proto\x12\x14galaxy_repository.v1\x1a\x1fgoogle/protobuf/timestamp.proto\x1a\x1egoogle/protobuf/wrappers.proto\"\x17\n\x15TestConnectionRequest\"!\n\x13TestConnectionReply\x12\n\n\x02ok\x18\x01 \x01(\x08\"\x1a\n\x18GetLastDeployTimeRequest\"b\n\x16GetLastDeployTimeReply\x12\x0f\n\x07present\x18\x01 \x01(\x08\x12\x37\n\x13time_of_last_deploy\x18\x02 \x01(\x0b\x32\x1a.google.protobuf.Timestamp\"\x87\x03\n\x18\x44iscoverHierarchyRequest\x12\x11\n\tpage_size\x18\x01 \x01(\x05\x12\x12\n\npage_token\x18\x02 \x01(\t\x12\x19\n\x0froot_gobject_id\x18\x03 \x01(\x05H\x00\x12\x17\n\rroot_tag_name\x18\x04 \x01(\tH\x00\x12\x1d\n\x13root_contained_path\x18\x05 \x01(\tH\x00\x12.\n\tmax_depth\x18\x06 \x01(\x0b\x32\x1b.google.protobuf.Int32Value\x12\x14\n\x0c\x63\x61tegory_ids\x18\x07 \x03(\x05\x12\x1f\n\x17template_chain_contains\x18\x08 \x03(\t\x12\x15\n\rtag_name_glob\x18\t \x01(\t\x12\x1f\n\x12include_attributes\x18\n \x01(\x08H\x01\x88\x01\x01\x12\x1a\n\x12\x61larm_bearing_only\x18\x0b \x01(\x08\x12\x17\n\x0fhistorized_only\x18\x0c \x01(\x08\x42\x06\n\x04rootB\x15\n\x13_include_attributes\"\x82\x01\n\x16\x44iscoverHierarchyReply\x12\x33\n\x07objects\x18\x01 \x03(\x0b\x32\".galaxy_repository.v1.GalaxyObject\x12\x17\n\x0fnext_page_token\x18\x02 \x01(\t\x12\x1a\n\x12total_object_count\x18\x03 \x01(\x05\"U\n\x18WatchDeployEventsRequest\x12\x39\n\x15last_seen_deploy_time\x18\x01 \x01(\x0b\x32\x1a.google.protobuf.Timestamp\"\xdd\x01\n\x0b\x44\x65ployEvent\x12\x10\n\x08sequence\x18\x01 \x01(\x04\x12/\n\x0bobserved_at\x18\x02 \x01(\x0b\x32\x1a.google.protobuf.Timestamp\x12\x37\n\x13time_of_last_deploy\x18\x03 \x01(\x0b\x32\x1a.google.protobuf.Timestamp\x12#\n\x1btime_of_last_deploy_present\x18\x04 \x01(\x08\x12\x14\n\x0cobject_count\x18\x05 \x01(\x05\x12\x17\n\x0f\x61ttribute_count\x18\x06 \x01(\x05\"\x93\x02\n\x0cGalaxyObject\x12\x12\n\ngobject_id\x18\x01 \x01(\x05\x12\x10\n\x08tag_name\x18\x02 \x01(\t\x12\x16\n\x0e\x63ontained_name\x18\x03 \x01(\t\x12\x13\n\x0b\x62rowse_name\x18\x04 \x01(\t\x12\x19\n\x11parent_gobject_id\x18\x05 \x01(\x05\x12\x0f\n\x07is_area\x18\x06 \x01(\x08\x12\x13\n\x0b\x63\x61tegory_id\x18\x07 \x01(\x05\x12\x1c\n\x14hosted_by_gobject_id\x18\x08 \x01(\x05\x12\x16\n\x0etemplate_chain\x18\t \x03(\t\x12\x39\n\nattributes\x18\n \x03(\x0b\x32%.galaxy_repository.v1.GalaxyAttribute\"\xa8\x02\n\x0fGalaxyAttribute\x12\x16\n\x0e\x61ttribute_name\x18\x01 \x01(\t\x12\x1a\n\x12\x66ull_tag_reference\x18\x02 \x01(\t\x12\x14\n\x0cmx_data_type\x18\x03 \x01(\x05\x12\x16\n\x0e\x64\x61ta_type_name\x18\x04 \x01(\t\x12\x10\n\x08is_array\x18\x05 \x01(\x08\x12\x17\n\x0f\x61rray_dimension\x18\x06 \x01(\x05\x12\x1f\n\x17\x61rray_dimension_present\x18\x07 \x01(\x08\x12\x1d\n\x15mx_attribute_category\x18\x08 \x01(\x05\x12\x1f\n\x17security_classification\x18\t \x01(\x05\x12\x15\n\ris_historized\x18\n \x01(\x08\x12\x10\n\x08is_alarm\x18\x0b \x01(\x08\"\xdc\x02\n\x15\x42rowseChildrenRequest\x12\x1b\n\x11parent_gobject_id\x18\x01 \x01(\x05H\x00\x12\x19\n\x0fparent_tag_name\x18\x02 \x01(\tH\x00\x12\x1f\n\x15parent_contained_path\x18\x03 \x01(\tH\x00\x12\x11\n\tpage_size\x18\x04 \x01(\x05\x12\x12\n\npage_token\x18\x05 \x01(\t\x12\x14\n\x0c\x63\x61tegory_ids\x18\x06 \x03(\x05\x12\x1f\n\x17template_chain_contains\x18\x07 \x03(\t\x12\x15\n\rtag_name_glob\x18\x08 \x01(\t\x12\x1f\n\x12include_attributes\x18\t \x01(\x08H\x01\x88\x01\x01\x12\x1a\n\x12\x61larm_bearing_only\x18\n \x01(\x08\x12\x17\n\x0fhistorized_only\x18\x0b \x01(\x08\x42\x08\n\x06parentB\x15\n\x13_include_attributes\"\xb3\x01\n\x13\x42rowseChildrenReply\x12\x34\n\x08\x63hildren\x18\x01 \x03(\x0b\x32\".galaxy_repository.v1.GalaxyObject\x12\x17\n\x0fnext_page_token\x18\x02 \x01(\t\x12\x19\n\x11total_child_count\x18\x03 \x01(\x05\x12\x1a\n\x12\x63hild_has_children\x18\x04 \x03(\x08\x12\x16\n\x0e\x63\x61\x63he_sequence\x18\x05 \x01(\x04\x32\xb6\x04\n\x10GalaxyRepository\x12h\n\x0eTestConnection\x12+.galaxy_repository.v1.TestConnectionRequest\x1a).galaxy_repository.v1.TestConnectionReply\x12q\n\x11GetLastDeployTime\x12..galaxy_repository.v1.GetLastDeployTimeRequest\x1a,.galaxy_repository.v1.GetLastDeployTimeReply\x12q\n\x11\x44iscoverHierarchy\x12..galaxy_repository.v1.DiscoverHierarchyRequest\x1a,.galaxy_repository.v1.DiscoverHierarchyReply\x12h\n\x11WatchDeployEvents\x12..galaxy_repository.v1.WatchDeployEventsRequest\x1a!.galaxy_repository.v1.DeployEvent0\x01\x12h\n\x0e\x42rowseChildren\x12+.galaxy_repository.v1.BrowseChildrenRequest\x1a).galaxy_repository.v1.BrowseChildrenReplyB-\xaa\x02*ZB.MOM.WW.MxGateway.Contracts.Proto.Galaxyb\x06proto3')
 
 _globals = globals()
 _builder.BuildMessageAndEnumDescriptors(DESCRIPTOR, _globals)
@@ -54,6 +54,10 @@ if not _descriptor._USE_C_DESCRIPTORS:
   _globals['_GALAXYOBJECT']._serialized_end=1416
   _globals['_GALAXYATTRIBUTE']._serialized_start=1419
   _globals['_GALAXYATTRIBUTE']._serialized_end=1715
-  _globals['_GALAXYREPOSITORY']._serialized_start=1718
-  _globals['_GALAXYREPOSITORY']._serialized_end=2178
+  _globals['_BROWSECHILDRENREQUEST']._serialized_start=1718
+  _globals['_BROWSECHILDRENREQUEST']._serialized_end=2066
+  _globals['_BROWSECHILDRENREPLY']._serialized_start=2069
+  _globals['_BROWSECHILDRENREPLY']._serialized_end=2248
+  _globals['_GALAXYREPOSITORY']._serialized_start=2251
+  _globals['_GALAXYREPOSITORY']._serialized_end=2817
 # @@protoc_insertion_point(module_scope)

clients/python/src/zb_mom_ww_mxgateway/generated/galaxy_repository_pb2_grpc.py

@@ -65,6 +65,11 @@ class GalaxyRepositoryStub(object):
                 request_serializer=galaxy__repository__pb2.WatchDeployEventsRequest.SerializeToString,
                 response_deserializer=galaxy__repository__pb2.DeployEvent.FromString,
                 _registered_method=True)
+        self.BrowseChildren = channel.unary_unary(
+                '/galaxy_repository.v1.GalaxyRepository/BrowseChildren',
+                request_serializer=galaxy__repository__pb2.BrowseChildrenRequest.SerializeToString,
+                response_deserializer=galaxy__repository__pb2.BrowseChildrenReply.FromString,
+                _registered_method=True)
 
 
 class GalaxyRepositoryServicer(object):
@@ -111,6 +116,16 @@ class GalaxyRepositoryServicer(object):
         context.set_details('Method not implemented!')
         raise NotImplementedError('Method not implemented!')
 
+    def BrowseChildren(self, request, context):
+        """Returns the direct children of a parent object (or the root objects when
+        `parent` is unset). Designed for OPC UA-style lazy expand: clients walk
+        one level at a time instead of paging the full hierarchy. Filters mirror
+        DiscoverHierarchy exactly. Backed by the same shared hierarchy cache.
+        """
+        context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+        context.set_details('Method not implemented!')
+        raise NotImplementedError('Method not implemented!')
+
 
 def add_GalaxyRepositoryServicer_to_server(servicer, server):
     rpc_method_handlers = {
@@ -134,6 +149,11 @@ def add_GalaxyRepositoryServicer_to_server(servicer, server):
                     request_deserializer=galaxy__repository__pb2.WatchDeployEventsRequest.FromString,
                     response_serializer=galaxy__repository__pb2.DeployEvent.SerializeToString,
             ),
+            'BrowseChildren': grpc.unary_unary_rpc_method_handler(
+                    servicer.BrowseChildren,
+                    request_deserializer=galaxy__repository__pb2.BrowseChildrenRequest.FromString,
+                    response_serializer=galaxy__repository__pb2.BrowseChildrenReply.SerializeToString,
+            ),
     }
     generic_handler = grpc.method_handlers_generic_handler(
             'galaxy_repository.v1.GalaxyRepository', rpc_method_handlers)
@@ -263,3 +283,30 @@ class GalaxyRepository(object):
             timeout,
             metadata,
             _registered_method=True)
+
+    @staticmethod
+    def BrowseChildren(request,
+            target,
+            options=(),
+            channel_credentials=None,
+            call_credentials=None,
+            insecure=False,
+            compression=None,
+            wait_for_ready=None,
+            timeout=None,
+            metadata=None):
+        return grpc.experimental.unary_unary(
+            request,
+            target,
+            '/galaxy_repository.v1.GalaxyRepository/BrowseChildren',
+            galaxy__repository__pb2.BrowseChildrenRequest.SerializeToString,
+            galaxy__repository__pb2.BrowseChildrenReply.FromString,
+            options,
+            channel_credentials,
+            insecure,
+            call_credentials,
+            compression,
+            wait_for_ready,
+            timeout,
+            metadata,
+            _registered_method=True)

clients/python/src/zb_mom_ww_mxgateway/generated/mxaccess_gateway_pb2_grpc.py

@@ -135,6 +135,9 @@ class MxAccessGatewayServicer(object):
         reconnect to seed Part 9 client state, or to reconcile alarms that may
         have been missed during a transport blip. Streamed so callers can
         begin processing without buffering the full set.
+        `QueryActiveAlarmsRequest.alarm_filter_prefix` optionally narrows the
+        snapshot to alarms whose `alarm_full_reference` starts with the given
+        prefix; an empty prefix returns the full set.
         """
         context.set_code(grpc.StatusCode.UNIMPLEMENTED)
         context.set_details('Method not implemented!')

clients/python/src/zb_mom_ww_mxgateway/options.py

@@ -2,12 +2,15 @@
 
 from __future__ import annotations
 
-from dataclasses import dataclass
+import ssl
+from collections.abc import Sequence
+from dataclasses import dataclass, field
 from pathlib import Path
 
 import grpc
 
 from .auth import REDACTED, ApiKey
+from .errors import MxGatewayTransportError
 
 
 @dataclass(frozen=True)
@@ -18,6 +21,7 @@ class ClientOptions:
     api_key: str | ApiKey | None = None
     plaintext: bool = False
     ca_file: str | None = None
+    require_certificate_validation: bool = False
     server_name_override: str | None = None
     call_timeout: float | None = 30.0
     stream_timeout: float | None = None
@@ -44,6 +48,7 @@ class ClientOptions:
             f"{type(self).__name__}(endpoint={self.endpoint!r}, "
             f"api_key={api_key!r}, plaintext={self.plaintext!r}, "
             f"ca_file={self.ca_file!r}, "
+            f"require_certificate_validation={self.require_certificate_validation!r}, "
             f"server_name_override={self.server_name_override!r}, "
             f"call_timeout={self.call_timeout!r}, "
             f"stream_timeout={self.stream_timeout!r}, "
@@ -51,8 +56,51 @@ class ClientOptions:
         )
 
 
+@dataclass(frozen=True)
+class BrowseChildrenOptions:
+    """Filters and shape options for ``GalaxyRepositoryClient.browse``.
+
+    Mirrors the AND-combined filter set on ``BrowseChildrenRequest`` so a
+    single instance can be re-used across an entire lazy browse session
+    (the filter set is part of the page-token contract).
+    """
+
+    category_ids: Sequence[int] = field(default_factory=tuple)
+    template_chain_contains: Sequence[str] = field(default_factory=tuple)
+    tag_name_glob: str | None = None
+    include_attributes: bool | None = None
+    alarm_bearing_only: bool = False
+    historized_only: bool = False
+
+
+def _split_authority(endpoint: str) -> tuple[str, int]:
+    """Split a gRPC target (optionally scheme-prefixed) into (host, port).
+
+    Handles bracketed IPv6 literals (e.g. ``[::1]:5120`` or bare ``[::1]``),
+    returning the host without brackets so it is safe to pass to
+    ``ssl.get_server_certificate``.
+    """
+    target = endpoint.split("://", 1)[-1]
+    if target.startswith("["):
+        # Bracketed IPv6: "[::1]:5120" or "[::1]"
+        bracket_end = target.find("]")
+        host = target[1:bracket_end]  # strip surrounding brackets
+        remainder = target[bracket_end + 1 :]  # ":5120" or ""
+        port_str = remainder.lstrip(":")
+        return (host, int(port_str) if port_str else 443)
+    host, _, port = target.rpartition(":")
+    return (host or "localhost", int(port) if port else 443)
+
+
 def create_channel(options: ClientOptions) -> grpc.aio.Channel:
-    """Create a plaintext or TLS `grpc.aio` channel from client options."""
+    """Create a plaintext or TLS `grpc.aio` channel from client options.
+
+    The TLS default is lenient: grpc-python has no per-channel skip-verify, so
+    the server's presented certificate is fetched once (unverified) and pinned
+    as the channel's only trust root (trust-on-first-use). Set
+    `require_certificate_validation=True` to force system-trust verification, or
+    pass `ca_file` to verify against a specific CA — both bypass the TOFU path.
+    """
 
     channel_options: list[tuple[str, str | int]] = [
         ("grpc.max_receive_message_length", options.max_grpc_message_bytes),
@@ -64,11 +112,28 @@ def create_channel(options: ClientOptions) -> grpc.aio.Channel:
     if options.plaintext:
         return grpc.aio.insecure_channel(options.endpoint, options=channel_options)
 
-    root_certificates = None
     if options.ca_file:
         root_certificates = Path(options.ca_file).read_bytes()
+        credentials = grpc.ssl_channel_credentials(root_certificates=root_certificates)
+    elif options.require_certificate_validation:
+        credentials = grpc.ssl_channel_credentials()
+    else:
+        # Lenient default: grpc-python has no per-channel skip-verify, so fetch the
+        # server's certificate (unverified) and pin it for this channel (TOFU).
+        host, port = _split_authority(options.endpoint)
+        try:
+            presented = ssl.get_server_certificate((host, port))
+        except OSError as error:
+            raise MxGatewayTransportError(
+                f"failed to fetch TLS certificate from {options.endpoint}: {error}"
+            ) from error
+        credentials = grpc.ssl_channel_credentials(root_certificates=presented.encode("ascii"))
+        # The gateway self-signed cert always carries a "localhost" SAN, so default
+        # the SNI/target-name override to it when none was supplied, tolerating
+        # dial-by-IP or hostname mismatch.
+        if not options.server_name_override:
+            channel_options.append(("grpc.ssl_target_name_override", "localhost"))
 
-    credentials = grpc.ssl_channel_credentials(root_certificates=root_certificates)
     return grpc.aio.secure_channel(
         options.endpoint,
         credentials,

clients/python/src/zb_mom_ww_mxgateway_cli/commands.py

@@ -3,15 +3,18 @@
 from __future__ import annotations
 
 import asyncio
+import contextlib
+import io
 import json
+import logging
 import os
 import sys
+import time
 from collections.abc import Awaitable, Callable
 from datetime import datetime, timezone
 from typing import Any
 
 import click
-from click.testing import CliRunner
 from google.protobuf.json_format import MessageToDict
 
 from zb_mom_ww_mxgateway import __version__
@@ -22,6 +25,8 @@ from zb_mom_ww_mxgateway.generated import mxaccess_gateway_pb2 as pb
 from zb_mom_ww_mxgateway.options import ClientOptions
 from zb_mom_ww_mxgateway.values import MxValueInput, to_mx_value
 
+logger = logging.getLogger(__name__)
+
 MAX_AGGREGATE_EVENTS = 10_000
 
 _BATCH_EOR = "__MXGW_BATCH_EOR__"
@@ -56,9 +61,10 @@ def batch() -> None:
     Errors do NOT terminate the loop. Each command's output (including any error JSON) is
     written to stdout followed by a line containing exactly ``__MXGW_BATCH_EOR__``, then
     stdout is flushed. Error output is formatted as ``{"error": "...", "type": "..."}``.
-    """
 
-    runner = CliRunner()
+    Recursive ``batch`` lines are rejected (Client.Python-024) — re-entering the batch
+    dispatcher would silently spawn a nested loop reading from the same exhausted stdin.
+    """
 
     for raw_line in sys.stdin:
         line = raw_line.rstrip("\n").rstrip("\r")
@@ -68,44 +74,77 @@ def batch() -> None:
 
         args = line.split()
 
-        try:
-            result = runner.invoke(main, args, catch_exceptions=True)
-        except Exception as exc:  # noqa: BLE001 — be safe; never let batch loop die
-            _batch_write_error(exc.__class__.__name__, str(exc))
+        # Reject a recursive `batch` line outright: the nested invocation would
+        # read from the already-exhausted stdin (or, depending on harness, the
+        # same stream the outer batch is consuming line-by-line) and silently
+        # exit. Surface it as an explicit error block so callers can audit the
+        # mis-routed line.
+        if args and args[0] == "batch":
+            _batch_write_error(
+                "RecursiveBatchError",
+                "nested 'batch' invocation is not allowed inside batch mode",
+            )
             _batch_flush_eor()
             continue
 
-        if result.exit_code == 0:
-            # Normal success — write captured output as-is.
-            sys.stdout.write(result.output)
+        _dispatch_batch_line(args)
+
+
+def _dispatch_batch_line(args: list[str]) -> None:
+    """Run a single batch line through the Click parser directly (no CliRunner).
+
+    Captures the subcommand's stdout via :func:`contextlib.redirect_stdout` and
+    synthesises the standard ``{"error": ..., "type": ...}`` shape on failure.
+    Click exceptions (`ClickException`, `UsageError`) are caught and rendered;
+    `SystemExit(0)` from a Click command is treated as a clean exit, while a
+    non-zero `SystemExit` is rendered as a CLI error. All other exceptions are
+    captured and rendered as `{"error": str(exc), "type": exc.__class__.__name__}`
+    so the loop never dies.
+    """
+
+    buffer = io.StringIO()
+    exit_code = 0
+    exc: BaseException | None = None
+    try:
+        with contextlib.redirect_stdout(buffer):
+            try:
+                # `standalone_mode=False` makes Click raise instead of calling
+                # `sys.exit`; we still need to handle SystemExit because some
+                # commands explicitly raise it (or `click.UsageError` converts
+                # to a SystemExit under some entry-point paths).
+                main.main(args=args, standalone_mode=False, prog_name="mxgw-py")
+            except click.exceptions.Exit as click_exit:
+                exit_code = click_exit.exit_code
+            except click.ClickException as click_exc:
+                exit_code = click_exc.exit_code
+                exc = click_exc
+                click.echo(f"Error: {click_exc.format_message()}", err=False)
+            except SystemExit as sys_exit:
+                code = sys_exit.code
+                exit_code = int(code) if isinstance(code, int) else (0 if code is None else 1)
+    except Exception as captured:  # noqa: BLE001 — never let batch loop die
+        exc = captured
+        exit_code = 1
+
+    output = buffer.getvalue()
+    if exit_code == 0 and exc is None:
+        sys.stdout.write(output)
+    else:
+        if output.lstrip().startswith("{"):
+            # Inner command already emitted JSON (e.g. a structured error) —
+            # relay verbatim.
+            sys.stdout.write(output)
+            if output and not output.endswith("\n"):
+                sys.stdout.write("\n")
+        elif exc is not None:
+            _batch_write_error(type(exc).__name__, str(exc))
         else:
-            # Something went wrong.  If the command already emitted a JSON object
-            # (e.g. the output starts with '{'), trust that and relay it verbatim.
-            # Otherwise synthesise the standard {"error": ..., "type": ...} shape.
-            output = result.output or ""
-            exc = result.exception
+            msg = output.strip()
+            if msg.startswith("Error: "):
+                msg = msg[len("Error: "):]
+            _batch_write_error("CliError", msg)
 
-            if output.lstrip().startswith("{"):
-                # Already JSON — relay verbatim (may or may not end with newline).
-                sys.stdout.write(output)
-                if not output.endswith("\n"):
-                    sys.stdout.write("\n")
-            elif exc is not None and not isinstance(exc, SystemExit):
-                _batch_write_error(type(exc).__name__, str(exc))
-            else:
-                # Click's default error format is "Error: <message>\n"; extract the
-                # message so the harness gets clean JSON.
-                msg = output.strip()
-                if msg.startswith("Error: "):
-                    msg = msg[len("Error: "):]
-                exc_type = (
-                    type(exc).__name__
-                    if exc is not None and not isinstance(exc, SystemExit)
-                    else "CliError"
-                )
-                _batch_write_error(exc_type, msg)
-
-        _batch_flush_eor()
+    _batch_flush_eor()
 
 
 def _batch_write_error(exc_type: str, message: str) -> None:
@@ -673,7 +712,6 @@ async def _write_secured2_bulk(**kwargs: Any) -> dict[str, Any]:
 
 async def _bench_read_bulk(**kwargs: Any) -> dict[str, Any]:
     """ReadBulk stress benchmark — matches the .NET / Go / Rust / Java schema."""
-    import time
 
     bulk_size = int(kwargs["bulk_size"])
     if bulk_size < 1:
@@ -730,12 +768,12 @@ async def _bench_read_bulk(**kwargs: Any) -> dict[str, Any]:
             if item_handles:
                 try:
                     await session.unsubscribe_bulk(server_handle, item_handles)
-                except Exception:
-                    pass
+                except Exception as exc:  # noqa: BLE001 — bench is best-effort
+                    logger.warning("bench-read-bulk: unsubscribe_bulk cleanup failed: %s", exc)
             try:
                 await session.close()
-            except Exception:
-                pass
+            except Exception as exc:  # noqa: BLE001 — bench is best-effort
+                logger.warning("bench-read-bulk: session.close cleanup failed: %s", exc)
 
         return {
             "language": "python",
@@ -899,11 +937,21 @@ def _session(client: GatewayClient, session_id: str):
 
 
 def _use_plaintext(kwargs: dict[str, Any]) -> bool:
-    if kwargs.get("use_tls"):
-        return False
-    if kwargs.get("plaintext"):
-        return True
-    return kwargs["endpoint"].startswith("localhost:") or kwargs["endpoint"].startswith("127.0.0.1:")
+    """Resolve the plaintext / TLS contract from the CLI flags.
+
+    TLS is the default. ``--plaintext`` is the only way to opt in to an
+    unencrypted channel; ``--tls`` is accepted as a redundant explicit
+    affirmation. Combining the two is a usage error (regression-guarded by
+    Client.Python-023 — the previous silent ``localhost:`` /
+    ``127.0.0.1:`` auto-plaintext branch leaked the API-key bearer over a
+    plaintext channel when a user ran the gateway behind TLS on loopback).
+    """
+
+    plaintext = bool(kwargs.get("plaintext"))
+    use_tls = bool(kwargs.get("use_tls"))
+    if plaintext and use_tls:
+        raise click.UsageError("--plaintext and --tls are mutually exclusive")
+    return plaintext
 
 
 def _api_key_from_env(name: str | None) -> str | None:

clients/python/tests/test_auth_options.py

@@ -72,27 +72,83 @@ def test_create_channel_uses_plaintext_channel(monkeypatch: pytest.MonkeyPatch)
     ]
 
 
-def test_create_channel_uses_tls_channel(monkeypatch: pytest.MonkeyPatch) -> None:
-    calls: list[tuple[str, object, object]] = []
+def test_create_channel_uses_tls_channel_tofu_default(monkeypatch: pytest.MonkeyPatch) -> None:
+    """Default TLS (no ca_file, no require_certificate_validation) uses TOFU:
+    fetches the server cert unverified, pins it as root_certificates, and adds
+    grpc.ssl_target_name_override = "localhost" automatically.
+    """
+    _DUMMY_PEM = "-----BEGIN CERTIFICATE-----\nZmFrZQ==\n-----END CERTIFICATE-----\n"
+    get_cert_calls: list[tuple[str, int]] = []
 
-    def fake_credentials(*, root_certificates: object) -> str:
-        assert root_certificates is None
+    def fake_get_server_certificate(addr: tuple[str, int]) -> str:
+        get_cert_calls.append(addr)
+        return _DUMMY_PEM
+
+    cred_calls: list[object] = []
+
+    def fake_credentials(*, root_certificates: object = None) -> str:
+        cred_calls.append(root_certificates)
         return "creds"
 
+    channel_calls: list[tuple[str, object, object]] = []
+
     def fake_secure_channel(endpoint: str, credentials: object, *, options: object) -> str:
-        calls.append((endpoint, credentials, options))
+        channel_calls.append((endpoint, credentials, options))
         return "tls-channel"
 
-    monkeypatch.setattr(
-        options_module.grpc,
-        "ssl_channel_credentials",
-        fake_credentials,
+    monkeypatch.setattr(options_module.ssl, "get_server_certificate", fake_get_server_certificate)
+    monkeypatch.setattr(options_module.grpc, "ssl_channel_credentials", fake_credentials)
+    monkeypatch.setattr(options_module.grpc.aio, "secure_channel", fake_secure_channel)
+
+    channel = create_channel(
+        ClientOptions(endpoint="gateway.example:5001"),
     )
+
+    assert channel == "tls-channel"
+    # TOFU: should have fetched the cert from the server (host, port)
+    assert get_cert_calls == [("gateway.example", 5001)]
+    # Pinned the fetched PEM bytes as root_certificates
+    assert cred_calls == [_DUMMY_PEM.encode("ascii")]
+    # Auto-injected localhost override (no server_name_override supplied)
+    assert channel_calls == [
+        (
+            "gateway.example:5001",
+            "creds",
+            [
+                ("grpc.max_receive_message_length", 16 * 1024 * 1024),
+                ("grpc.max_send_message_length", 16 * 1024 * 1024),
+                ("grpc.ssl_target_name_override", "localhost"),
+            ],
+        ),
+    ]
+
+
+def test_create_channel_uses_tls_channel_tofu_respects_server_name_override(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """When server_name_override is set, TOFU still runs but does NOT add the
+    auto-localhost override (the explicit override is already in channel_options).
+    """
+    _DUMMY_PEM = "-----BEGIN CERTIFICATE-----\nZmFrZQ==\n-----END CERTIFICATE-----\n"
     monkeypatch.setattr(
-        options_module.grpc.aio,
-        "secure_channel",
-        fake_secure_channel,
+        options_module.ssl,
+        "get_server_certificate",
+        lambda addr: _DUMMY_PEM,
     )
+    cred_calls: list[object] = []
+
+    def fake_credentials(*, root_certificates: object = None) -> str:
+        cred_calls.append(root_certificates)
+        return "creds"
+
+    channel_calls: list[tuple[str, object, object]] = []
+
+    def fake_secure_channel(endpoint: str, credentials: object, *, options: object) -> str:
+        channel_calls.append((endpoint, credentials, options))
+        return "tls-channel"
+
+    monkeypatch.setattr(options_module.grpc, "ssl_channel_credentials", fake_credentials)
+    monkeypatch.setattr(options_module.grpc.aio, "secure_channel", fake_secure_channel)
 
     channel = create_channel(
         ClientOptions(
@@ -102,14 +158,121 @@ def test_create_channel_uses_tls_channel(monkeypatch: pytest.MonkeyPatch) -> Non
     )
 
     assert channel == "tls-channel"
-    assert calls == [
-            (
-                "gateway.example:5001",
-                "creds",
-                [
-                    ("grpc.max_receive_message_length", 16 * 1024 * 1024),
-                    ("grpc.max_send_message_length", 16 * 1024 * 1024),
-                    ("grpc.ssl_target_name_override", "gateway.test"),
-                ],
-            ),
-        ]
+    assert cred_calls == [_DUMMY_PEM.encode("ascii")]
+    assert channel_calls == [
+        (
+            "gateway.example:5001",
+            "creds",
+            [
+                ("grpc.max_receive_message_length", 16 * 1024 * 1024),
+                ("grpc.max_send_message_length", 16 * 1024 * 1024),
+                # Explicit override from ClientOptions — not the auto-localhost one
+                ("grpc.ssl_target_name_override", "gateway.test"),
+            ],
+        ),
+    ]
+
+
+def test_create_channel_uses_tls_channel_require_cert_validation(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """require_certificate_validation=True uses system trust (no TOFU, no root_certificates)."""
+    get_cert_called = False
+
+    def fake_get_server_certificate(addr: object) -> str:  # pragma: no cover
+        nonlocal get_cert_called
+        get_cert_called = True
+        return "SHOULD_NOT_BE_CALLED"
+
+    cred_calls: list[object] = []
+
+    def fake_credentials(**kwargs: object) -> str:
+        cred_calls.append(kwargs)
+        return "creds"
+
+    channel_calls: list[tuple[str, object, object]] = []
+
+    def fake_secure_channel(endpoint: str, credentials: object, *, options: object) -> str:
+        channel_calls.append((endpoint, credentials, options))
+        return "tls-channel"
+
+    monkeypatch.setattr(options_module.ssl, "get_server_certificate", fake_get_server_certificate)
+    monkeypatch.setattr(options_module.grpc, "ssl_channel_credentials", fake_credentials)
+    monkeypatch.setattr(options_module.grpc.aio, "secure_channel", fake_secure_channel)
+
+    channel = create_channel(
+        ClientOptions(
+            endpoint="gateway.example:5001",
+            require_certificate_validation=True,
+        ),
+    )
+
+    assert channel == "tls-channel"
+    # Must NOT call TOFU prefetch
+    assert not get_cert_called
+    # ssl_channel_credentials() called with NO keyword args (system trust)
+    assert cred_calls == [{}]
+    assert channel_calls == [
+        (
+            "gateway.example:5001",
+            "creds",
+            [
+                ("grpc.max_receive_message_length", 16 * 1024 * 1024),
+                ("grpc.max_send_message_length", 16 * 1024 * 1024),
+            ],
+        ),
+    ]
+
+
+def test_create_channel_uses_tls_channel_ca_file(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: pytest.TempPathFactory,
+) -> None:
+    """ca_file path: reads the PEM file, passes bytes as root_certificates, skips TOFU."""
+    ca_pem = b"-----BEGIN CERTIFICATE-----\nY2FkYXRh\n-----END CERTIFICATE-----\n"
+    ca_file = tmp_path / "ca.pem"
+    ca_file.write_bytes(ca_pem)
+
+    get_cert_called = False
+
+    def fake_get_server_certificate(addr: object) -> str:  # pragma: no cover
+        nonlocal get_cert_called
+        get_cert_called = True
+        return "SHOULD_NOT_BE_CALLED"
+
+    cred_calls: list[object] = []
+
+    def fake_credentials(*, root_certificates: object = None) -> str:
+        cred_calls.append(root_certificates)
+        return "creds"
+
+    channel_calls: list[tuple[str, object, object]] = []
+
+    def fake_secure_channel(endpoint: str, credentials: object, *, options: object) -> str:
+        channel_calls.append((endpoint, credentials, options))
+        return "tls-channel"
+
+    monkeypatch.setattr(options_module.ssl, "get_server_certificate", fake_get_server_certificate)
+    monkeypatch.setattr(options_module.grpc, "ssl_channel_credentials", fake_credentials)
+    monkeypatch.setattr(options_module.grpc.aio, "secure_channel", fake_secure_channel)
+
+    channel = create_channel(
+        ClientOptions(
+            endpoint="gateway.example:5001",
+            ca_file=str(ca_file),
+        ),
+    )
+
+    assert channel == "tls-channel"
+    assert not get_cert_called
+    assert cred_calls == [ca_pem]
+    assert channel_calls == [
+        (
+            "gateway.example:5001",
+            "creds",
+            [
+                ("grpc.max_receive_message_length", 16 * 1024 * 1024),
+                ("grpc.max_send_message_length", 16 * 1024 * 1024),
+            ],
+        ),
+    ]

clients/python/tests/test_galaxy.py

@@ -6,12 +6,16 @@ import asyncio
 from datetime import datetime, timezone
 from typing import Any
 
+import grpc
 import pytest
 from google.protobuf.timestamp_pb2 import Timestamp
 
 from zb_mom_ww_mxgateway import ClientOptions, DeployEvent, GalaxyRepositoryClient, WatchDeployEventsRequest
+from zb_mom_ww_mxgateway.errors import MxGatewayError
+from zb_mom_ww_mxgateway.galaxy import LazyBrowseNode
 from zb_mom_ww_mxgateway.generated import galaxy_repository_pb2 as galaxy_pb
 from zb_mom_ww_mxgateway.generated import galaxy_repository_pb2_grpc as galaxy_pb_grpc
+from zb_mom_ww_mxgateway.options import BrowseChildrenOptions
 
 
 def test_galaxy_messages_import() -> None:
@@ -268,15 +272,281 @@ async def test_close_marks_channel_closed_when_no_real_channel() -> None:
     await client.close()
 
 
+def _obj(gid: int, tag: str, is_area: bool = False) -> galaxy_pb.GalaxyObject:
+    return galaxy_pb.GalaxyObject(
+        gobject_id=gid, tag_name=tag, browse_name=tag, is_area=is_area,
+    )
+
+
+def _build_browse_reply(
+    children: list[galaxy_pb.GalaxyObject],
+    child_has_children: list[bool],
+    cache_sequence: int,
+    next_page_token: str = "",
+) -> galaxy_pb.BrowseChildrenReply:
+    reply = galaxy_pb.BrowseChildrenReply(
+        total_child_count=len(children),
+        cache_sequence=cache_sequence,
+        next_page_token=next_page_token,
+    )
+    reply.children.extend(children)
+    reply.child_has_children.extend(child_has_children)
+    return reply
+
+
+def _fake_aio_rpc_error(code: grpc.StatusCode, details: str) -> grpc.aio.AioRpcError:
+    return grpc.aio.AioRpcError(
+        code=code,
+        initial_metadata=grpc.aio.Metadata(),
+        trailing_metadata=grpc.aio.Metadata(),
+        details=details,
+    )
+
+
+@pytest.mark.asyncio
+async def test_browse_no_parent_returns_roots() -> None:
+    stub = FakeGalaxyStub()
+    stub.browse_children.replies = [
+        _build_browse_reply(
+            children=[_obj(1, "Area_A", is_area=True), _obj(2, "Area_B", is_area=True)],
+            child_has_children=[True, False],
+            cache_sequence=7,
+        ),
+    ]
+    client = await GalaxyRepositoryClient.connect(
+        ClientOptions(endpoint="fake", plaintext=True),
+        stub=stub,
+    )
+
+    roots = await client.browse()
+
+    assert len(roots) == 2
+    assert all(isinstance(node, LazyBrowseNode) for node in roots)
+    assert roots[0].object.tag_name == "Area_A"
+    assert roots[0].has_children_hint is True
+    assert roots[1].has_children_hint is False
+    assert roots[0].is_expanded is False
+    request = stub.browse_children.requests[0]
+    assert request.WhichOneof("parent") is None
+    assert request.page_size == 500
+    assert request.page_token == ""
+
+
+@pytest.mark.asyncio
+async def test_browse_expand_populates_children_and_marks_expanded() -> None:
+    stub = FakeGalaxyStub()
+    stub.browse_children.replies = [
+        _build_browse_reply(
+            children=[_obj(1, "Area_A", is_area=True)],
+            child_has_children=[True],
+            cache_sequence=1,
+        ),
+        _build_browse_reply(
+            children=[_obj(11, "Child_A"), _obj(12, "Child_B")],
+            child_has_children=[False, False],
+            cache_sequence=1,
+        ),
+    ]
+    client = await GalaxyRepositoryClient.connect(
+        ClientOptions(endpoint="fake", plaintext=True),
+        stub=stub,
+    )
+
+    roots = await client.browse()
+    await roots[0].expand()
+
+    assert roots[0].is_expanded is True
+    assert [n.object.tag_name for n in roots[0].children] == ["Child_A", "Child_B"]
+    assert len(stub.browse_children.requests) == 2
+    expand_request = stub.browse_children.requests[1]
+    assert expand_request.WhichOneof("parent") == "parent_gobject_id"
+    assert expand_request.parent_gobject_id == 1
+
+
+@pytest.mark.asyncio
+async def test_browse_expand_idempotent_no_second_rpc() -> None:
+    stub = FakeGalaxyStub()
+    stub.browse_children.replies = [
+        _build_browse_reply(
+            children=[_obj(1, "Area_A", is_area=True)],
+            child_has_children=[True],
+            cache_sequence=1,
+        ),
+        _build_browse_reply(
+            children=[_obj(11, "Child_A")],
+            child_has_children=[False],
+            cache_sequence=1,
+        ),
+    ]
+    client = await GalaxyRepositoryClient.connect(
+        ClientOptions(endpoint="fake", plaintext=True),
+        stub=stub,
+    )
+
+    roots = await client.browse()
+    await roots[0].expand()
+    await roots[0].expand()
+
+    assert len(stub.browse_children.requests) == 2
+    assert len(roots[0].children) == 1
+
+
+@pytest.mark.asyncio
+async def test_browse_expand_concurrent_callers_only_fire_one_rpc() -> None:
+    stub = FakeGalaxyStub()
+    stub.browse_children.replies = [
+        _build_browse_reply([_obj(1, "Plant", is_area=True)], [True], 7),
+        _build_browse_reply([_obj(2, "Mixer_001")], [False], 7),
+    ]
+    client = await GalaxyRepositoryClient.connect(
+        ClientOptions(endpoint="fake", plaintext=True),
+        stub=stub,
+    )
+
+    roots = await client.browse()
+    # Ten concurrent expand calls on the same node should issue exactly one RPC.
+    await asyncio.gather(*(roots[0].expand() for _ in range(10)))
+
+    assert roots[0].is_expanded
+    assert len(roots[0].children) == 1
+    # 1 roots fetch + exactly 1 expand fetch = 2 total
+    assert len(stub.browse_children.requests) == 2
+
+
+@pytest.mark.asyncio
+async def test_browse_expand_unknown_parent_raises_mxgateway_error() -> None:
+    stub = FakeGalaxyStub()
+    stub.browse_children.replies = [
+        _build_browse_reply(
+            children=[_obj(99, "Stale_Parent", is_area=True)],
+            child_has_children=[True],
+            cache_sequence=1,
+        ),
+    ]
+    stub.browse_children.exceptions = [
+        None,
+        _fake_aio_rpc_error(grpc.StatusCode.NOT_FOUND, "parent not found"),
+    ]
+    client = await GalaxyRepositoryClient.connect(
+        ClientOptions(endpoint="fake", plaintext=True),
+        stub=stub,
+    )
+
+    roots = await client.browse()
+    with pytest.raises(MxGatewayError):
+        await roots[0].expand()
+
+
+@pytest.mark.asyncio
+async def test_browse_expand_multi_page_gathers_all_pages() -> None:
+    stub = FakeGalaxyStub()
+    stub.browse_children.replies = [
+        _build_browse_reply(
+            children=[_obj(7, "Area_Big", is_area=True)],
+            child_has_children=[True],
+            cache_sequence=2,
+        ),
+        _build_browse_reply(
+            children=[_obj(71, "Child_1"), _obj(72, "Child_2")],
+            child_has_children=[False, False],
+            cache_sequence=2,
+            next_page_token="7:abc:2",
+        ),
+        _build_browse_reply(
+            children=[_obj(73, "Child_3")],
+            child_has_children=[False],
+            cache_sequence=2,
+        ),
+    ]
+    client = await GalaxyRepositoryClient.connect(
+        ClientOptions(endpoint="fake", plaintext=True),
+        stub=stub,
+    )
+
+    roots = await client.browse()
+    await roots[0].expand()
+
+    assert [n.object.tag_name for n in roots[0].children] == ["Child_1", "Child_2", "Child_3"]
+    assert len(stub.browse_children.requests) == 3
+    assert stub.browse_children.requests[2].page_token == "7:abc:2"
+    assert stub.browse_children.requests[2].parent_gobject_id == 7
+
+
+@pytest.mark.asyncio
+async def test_browse_with_filter_forwards_to_request() -> None:
+    stub = FakeGalaxyStub()
+    stub.browse_children.replies = [
+        _build_browse_reply(
+            children=[_obj(1, "Area_A", is_area=True)],
+            child_has_children=[False],
+            cache_sequence=3,
+        ),
+    ]
+    client = await GalaxyRepositoryClient.connect(
+        ClientOptions(endpoint="fake", plaintext=True),
+        stub=stub,
+    )
+    options = BrowseChildrenOptions(
+        category_ids=(4, 5),
+        template_chain_contains=("$DelmiaReceiver",),
+        tag_name_glob="Area_*",
+        include_attributes=True,
+        alarm_bearing_only=True,
+        historized_only=True,
+    )
+
+    await client.browse(options)
+
+    request = stub.browse_children.requests[0]
+    assert list(request.category_ids) == [4, 5]
+    assert list(request.template_chain_contains) == ["$DelmiaReceiver"]
+    assert request.tag_name_glob == "Area_*"
+    assert request.HasField("include_attributes")
+    assert request.include_attributes is True
+    assert request.alarm_bearing_only is True
+    assert request.historized_only is True
+
+
+@pytest.mark.asyncio
+async def test_browse_children_raw_returns_reply_unwrapped() -> None:
+    """browse_children_raw forwards the request to the stub and returns the raw reply."""
+    stub = FakeGalaxyStub()
+    expected = _build_browse_reply(
+        children=[_obj(1, "Plant", is_area=True)],
+        child_has_children=[True],
+        cache_sequence=42,
+    )
+    stub.browse_children.replies = [expected]
+
+    async with await GalaxyRepositoryClient.connect(
+        endpoint="fake",
+        plaintext=True,
+        stub=stub,
+    ) as client:
+        request = galaxy_pb.BrowseChildrenRequest(
+            page_size=10,
+            tag_name_glob="Plant*",
+        )
+        reply = await client.browse_children_raw(request)
+
+    assert reply.cache_sequence == 42
+    assert len(reply.children) == 1
+    assert reply.children[0].tag_name == "Plant"
+    assert len(stub.browse_children.requests) == 1
+    assert stub.browse_children.requests[0].tag_name_glob == "Plant*"
+
+
 class FakeGalaxyStub:
     def __init__(self) -> None:
         self.test_connection = FakeUnary([galaxy_pb.TestConnectionReply(ok=False)])
         self.get_last_deploy_time = FakeUnary([galaxy_pb.GetLastDeployTimeReply(present=False)])
         self.discover_hierarchy = FakeUnary([galaxy_pb.DiscoverHierarchyReply()])
+        self.browse_children = FakeUnary([galaxy_pb.BrowseChildrenReply()])
         self.watch_deploy_events = FakeStream([])
         self.TestConnection = self.test_connection
         self.GetLastDeployTime = self.get_last_deploy_time
         self.DiscoverHierarchy = self.discover_hierarchy
+        self.BrowseChildren = self.browse_children
 
     @property
     def WatchDeployEvents(self) -> "FakeStream":  # noqa: N802 — gRPC naming
@@ -287,6 +557,8 @@ class FakeUnary:
     def __init__(self, replies: list[Any]) -> None:
         self.replies = replies
         self.requests: list[Any] = []
+        # None entries mean "no exception on this call"; aligns with the replies queue index-by-index.
+        self.exceptions: list[BaseException | None] = []
         self.metadata: tuple[tuple[str, str], ...] | None = None
 
     async def __call__(
@@ -298,6 +570,10 @@ class FakeUnary:
     ) -> Any:
         self.requests.append(request)
         self.metadata = metadata
+        if self.exceptions:
+            exc = self.exceptions.pop(0)
+            if exc is not None:
+                raise exc
         return self.replies.pop(0)
 
 

clients/python/tests/test_review_findings_022_to_026.py

@@ -0,0 +1,789 @@
+"""Regression tests for Client.Python-022..026.
+
+Each test corresponds to a finding from the latest re-review. Tests are
+TDD-first — they failed against the pre-fix source and pass against the
+fixed source.
+"""
+
+from __future__ import annotations
+
+import json
+import re
+import time as _time_module_ref
+from pathlib import Path
+from typing import Any
+
+import pytest
+from click.testing import CliRunner
+
+from zb_mom_ww_mxgateway import ClientOptions, GatewayClient
+from zb_mom_ww_mxgateway.generated import mxaccess_gateway_pb2 as pb
+from zb_mom_ww_mxgateway_cli import commands as cli_commands
+from zb_mom_ww_mxgateway_cli.commands import _use_plaintext, main
+
+_BATCH_EOR = "__MXGW_BATCH_EOR__"
+
+
+# ---------------------------------------------------------------------------
+# Client.Python-022 — README CLI examples must parse against the implementation.
+# ---------------------------------------------------------------------------
+
+
+def _readme_path() -> Path:
+    return Path(__file__).resolve().parent.parent / "README.md"
+
+
+def _extract_mxgw_py_examples() -> list[list[str]]:
+    """Return the README's ``mxgw-py ...`` example lines as click arg lists.
+
+    Replaces angle-bracket placeholders (``<id>``) with safe stub values and
+    leaves real flag names untouched. The returned arg lists drop the
+    ``mxgw-py`` prefix.
+    """
+
+    text = _readme_path().read_text(encoding="utf-8")
+    args: list[list[str]] = []
+    for raw_line in text.splitlines():
+        line = raw_line.strip()
+        if not line.startswith("mxgw-py "):
+            continue
+        # Strip the leading "mxgw-py " token.
+        body = line[len("mxgw-py ") :]
+        # Replace common placeholders so click does not error on the placeholder.
+        body = body.replace("<id>", "session-1")
+        # Backtick-quoted hostnames in the TLS example are not represented
+        # in CLI; safe to leave as-is.
+        tokens = _split_cli_tokens(body)
+        # Keep only examples that exercise a real subcommand. Skip TLS
+        # multi-flag example (we only need the README CLI examples added in
+        # commits 8738735 — stream-alarms / acknowledge-alarm).
+        args.append(tokens)
+    return args
+
+
+def _split_cli_tokens(body: str) -> list[str]:
+    """Split a CLI body into argv tokens, honouring double-quoted strings."""
+
+    tokens: list[str] = []
+    pattern = re.compile(r'"([^"]*)"|(\S+)')
+    for match in pattern.finditer(body):
+        quoted, plain = match.group(1), match.group(2)
+        tokens.append(quoted if quoted is not None else plain)
+    return tokens
+
+
+def test_readme_alarm_examples_parse_against_cli() -> None:
+    """README `stream-alarms` / `acknowledge-alarm` examples must parse without
+    triggering Click's ``no such option`` error.
+
+    Drives every README ``mxgw-py`` example through Click's ``--help`` style
+    parser by re-invoking the documented argv with a trailing ``--help`` flag so
+    only the parser runs (no RPC is attempted). If a documented flag does not
+    exist on the subcommand, Click prints ``no such option: --<flag>`` and
+    exits 2 — that is the regression we want to catch.
+    """
+
+    runner = CliRunner()
+    examples = _extract_mxgw_py_examples()
+    assert any(
+        "stream-alarms" in args for args in examples
+    ), "README must include a stream-alarms example."
+    assert any(
+        "acknowledge-alarm" in args for args in examples
+    ), "README must include an acknowledge-alarm example."
+
+    for argv in examples:
+        # Strip "--json" (already a real flag) and any value-bearing flag that
+        # requires a host/file/value, then append --help so we exercise the
+        # parser only.
+        # We just append --help — Click parses all options up to --help and
+        # then prints help; an unknown option still errors out first.
+        result = runner.invoke(main, [*argv, "--help"])
+        # Either help text printed (exit 0) or some other parser issue (exit 2);
+        # we only want to assert NO "no such option" error.
+        assert "no such option" not in result.output.lower(), (
+            f"README example failed Click parsing: argv={argv!r}\n"
+            f"output={result.output!r}"
+        )
+
+
+# ---------------------------------------------------------------------------
+# Client.Python-023 — REGRESSION of Client.Python-013. _use_plaintext must
+# not silently auto-downgrade on localhost / 127.0.0.1.
+# ---------------------------------------------------------------------------
+
+
+def test_use_plaintext_does_not_auto_downgrade_for_localhost_endpoint() -> None:
+    """A bare ``localhost:...`` endpoint with no flags must default to TLS."""
+
+    assert _use_plaintext({
+        "endpoint": "localhost:5001",
+        "plaintext": False,
+        "use_tls": False,
+    }) is False
+
+
+def test_use_plaintext_does_not_auto_downgrade_for_loopback_ipv4_endpoint() -> None:
+    """A bare ``127.0.0.1:...`` endpoint with no flags must default to TLS."""
+
+    assert _use_plaintext({
+        "endpoint": "127.0.0.1:5001",
+        "plaintext": False,
+        "use_tls": False,
+    }) is False
+
+
+def test_use_plaintext_requires_explicit_plaintext_flag() -> None:
+    """``--plaintext`` is the only way to opt in."""
+
+    assert _use_plaintext({
+        "endpoint": "localhost:5001",
+        "plaintext": True,
+        "use_tls": False,
+    }) is True
+
+
+def test_use_plaintext_tls_flag_explicitly_disables_plaintext() -> None:
+    """``--tls`` is accepted as an explicit affirmation of the default."""
+
+    assert _use_plaintext({
+        "endpoint": "localhost:5001",
+        "plaintext": False,
+        "use_tls": True,
+    }) is False
+
+
+def test_use_plaintext_rejects_plaintext_and_tls_combined() -> None:
+    """``--plaintext`` and ``--tls`` together must be rejected as ambiguous."""
+
+    import click as _click
+
+    with pytest.raises(_click.UsageError):
+        _use_plaintext({
+            "endpoint": "localhost:5001",
+            "plaintext": True,
+            "use_tls": True,
+        })
+
+
+def test_cli_localhost_endpoint_with_no_flags_uses_tls_channel(monkeypatch) -> None:
+    """End-to-end CLI: against ``localhost:...`` with no flags, the resolved
+    ``ClientOptions.plaintext`` flowing into ``GatewayClient.connect`` must be
+    ``False`` (TLS), so the API key bearer cannot leak over plaintext.
+    """
+
+    captured: dict[str, Any] = {}
+
+    class _FakeStub:
+        def __init__(self) -> None:
+            pass
+
+        async def OpenSession(self, request: Any, *, metadata: tuple[Any, ...]) -> Any:
+            captured["metadata"] = metadata
+            return pb.OpenSessionReply(
+                session_id="session-1",
+                protocol_status=pb.ProtocolStatus(code=pb.PROTOCOL_STATUS_CODE_OK),
+            )
+
+    real_connect = GatewayClient.connect
+
+    @classmethod
+    async def _spy_connect(cls, options: ClientOptions, **kwargs: Any) -> GatewayClient:
+        captured["options"] = options
+        return await real_connect(options, stub=_FakeStub())
+
+    monkeypatch.setattr(GatewayClient, "connect", _spy_connect)
+
+    runner = CliRunner()
+    result = runner.invoke(
+        main,
+        [
+            "open-session",
+            "--endpoint",
+            "localhost:5000",
+            "--api-key",
+            "mxgw_test_secret",
+            "--json",
+        ],
+    )
+
+    assert result.exit_code == 0, result.output
+    assert "options" in captured
+    assert captured["options"].plaintext is False, (
+        "localhost endpoint without --plaintext must NOT auto-downgrade to plaintext"
+    )
+
+
+# ---------------------------------------------------------------------------
+# Client.Python-024 — `batch` must not use CliRunner from production code,
+# and a recursive `batch` line must not silently re-enter.
+# ---------------------------------------------------------------------------
+
+
+def test_batch_command_does_not_use_clirunner_in_production() -> None:
+    """`commands.py` must not import or instantiate the test-only CliRunner helper.
+
+    Docstring references explaining what the module deliberately avoids are
+    permitted; what is forbidden is an actual ``import`` of ``click.testing``
+    or an actual ``CliRunner()`` instantiation in executable code.
+    """
+
+    source = Path(cli_commands.__file__).read_text(encoding="utf-8")
+    assert "from click.testing" not in source, (
+        "click.testing is a test-only helper and must not be used by production code"
+    )
+    assert "import click.testing" not in source, (
+        "click.testing is a test-only helper and must not be used by production code"
+    )
+    # `CliRunner()` (instantiation) must not appear in production code.
+    assert "CliRunner(" not in source, (
+        "CliRunner() must not be instantiated in production code"
+    )
+
+
+def test_batch_recursive_batch_line_is_bounded() -> None:
+    """A `batch` line nested inside `batch` stdin must not be silently spawned.
+
+    The pre-fix implementation re-invoked the test runner with empty stdin,
+    so `batch` inside `batch` exited cleanly with no error. The fix either
+    rejects the nested invocation or surfaces it as an error block so the
+    behaviour is auditable.
+    """
+
+    runner = CliRunner()
+    result = runner.invoke(
+        main,
+        ["batch"],
+        input="batch\nversion --json\n",
+    )
+
+    # Outer batch must still exit 0 and process both lines.
+    assert result.exit_code == 0
+    assert result.output.count(_BATCH_EOR) == 2
+
+    blocks = [block for block in result.output.split(_BATCH_EOR + "\n") if block]
+    # The first block — the recursive `batch` line — must surface an error
+    # JSON. (Either an explicit rejection, or some non-empty error block —
+    # NOT a silently empty block.)
+    first_block = blocks[0].strip()
+    assert first_block, "recursive batch line must not be silently swallowed"
+    payload = json.loads(first_block.splitlines()[-1])
+    assert "error" in payload, (
+        f"recursive batch line should surface an error: got {payload!r}"
+    )
+
+
+# ---------------------------------------------------------------------------
+# Client.Python-025 — Behavioural tests for new bulk SDK methods,
+# stream_alarms, and the new CLI subcommands.
+# ---------------------------------------------------------------------------
+
+
+class _AlarmFakeStream:
+    def __init__(self, messages: list[pb.AlarmFeedMessage]) -> None:
+        self._messages = list(messages)
+        self.cancelled = False
+
+    def __aiter__(self) -> "_AlarmFakeStream":
+        return self
+
+    async def __anext__(self) -> pb.AlarmFeedMessage:
+        if not self._messages:
+            raise StopAsyncIteration
+        return self._messages.pop(0)
+
+    def cancel(self) -> None:
+        self.cancelled = True
+
+
+class _BulkFakeUnary:
+    def __init__(self, replies: list[Any]) -> None:
+        self.replies = replies
+        self.requests: list[Any] = []
+        self.metadata: tuple[tuple[str, str], ...] | None = None
+
+    async def __call__(self, request: Any, *, metadata: tuple[tuple[str, str], ...]) -> Any:
+        self.requests.append(request)
+        self.metadata = metadata
+        return self.replies.pop(0)
+
+
+class _BulkFakeStub:
+    def __init__(self) -> None:
+        self.open_session = _BulkFakeUnary(
+            [
+                pb.OpenSessionReply(
+                    session_id="session-1",
+                    protocol_status=pb.ProtocolStatus(code=pb.PROTOCOL_STATUS_CODE_OK),
+                ),
+            ],
+        )
+        self.invoke = _BulkFakeUnary([])
+        self.OpenSession = self.open_session
+        self.Invoke = self.invoke
+        self.stream_alarms_metadata: tuple[tuple[str, str], ...] | None = None
+        self._alarm_stream = _AlarmFakeStream([])
+
+    def set_invoke_replies(self, replies: list[Any]) -> None:
+        self.invoke.replies = replies
+
+    def set_alarm_stream(self, stream: _AlarmFakeStream) -> None:
+        self._alarm_stream = stream
+
+    def StreamAlarms(self, request: Any, *, metadata: tuple[tuple[str, str], ...]) -> Any:
+        self.stream_alarms_request = request
+        self.stream_alarms_metadata = metadata
+        return self._alarm_stream
+
+
+@pytest.mark.asyncio
+async def test_session_read_bulk_sends_expected_request_shape() -> None:
+    stub = _BulkFakeStub()
+    stub.set_invoke_replies(
+        [
+            pb.MxCommandReply(
+                session_id="session-1",
+                kind=pb.MX_COMMAND_KIND_READ_BULK,
+                protocol_status=pb.ProtocolStatus(code=pb.PROTOCOL_STATUS_CODE_OK),
+                read_bulk=pb.BulkReadReply(
+                    results=[
+                        pb.BulkReadResult(
+                            tag_address="Tank01.Level",
+                            was_successful=True,
+                        ),
+                    ],
+                ),
+            ),
+        ],
+    )
+    client = await GatewayClient.connect(
+        ClientOptions(endpoint="fake", api_key="mxgw_test_secret", plaintext=True),
+        stub=stub,
+    )
+    session = await client.open_session()
+
+    results = await session.read_bulk(12, ["Tank01.Level"], timeout_ms=1500)
+
+    assert len(results) == 1
+    assert results[0].tag_address == "Tank01.Level"
+    request = stub.invoke.requests[0]
+    assert request.command.kind == pb.MX_COMMAND_KIND_READ_BULK
+    assert request.command.read_bulk.server_handle == 12
+    assert list(request.command.read_bulk.tag_addresses) == ["Tank01.Level"]
+    assert request.command.read_bulk.timeout_ms == 1500
+
+
+@pytest.mark.asyncio
+async def test_session_write_bulk_sends_expected_request_shape() -> None:
+    stub = _BulkFakeStub()
+    stub.set_invoke_replies(
+        [
+            pb.MxCommandReply(
+                session_id="session-1",
+                kind=pb.MX_COMMAND_KIND_WRITE_BULK,
+                protocol_status=pb.ProtocolStatus(code=pb.PROTOCOL_STATUS_CODE_OK),
+                write_bulk=pb.BulkWriteReply(
+                    results=[pb.BulkWriteResult(was_successful=True)],
+                ),
+            ),
+        ],
+    )
+    client = await GatewayClient.connect(
+        ClientOptions(endpoint="fake", api_key="mxgw_test_secret", plaintext=True),
+        stub=stub,
+    )
+    session = await client.open_session()
+
+    from zb_mom_ww_mxgateway.values import to_mx_value
+
+    entries = [
+        pb.WriteBulkEntry(item_handle=34, user_id=99, value=to_mx_value(123)),
+    ]
+    results = await session.write_bulk(12, entries)
+
+    assert results[0].was_successful is True
+    cmd = stub.invoke.requests[0].command
+    assert cmd.kind == pb.MX_COMMAND_KIND_WRITE_BULK
+    assert cmd.write_bulk.server_handle == 12
+    assert cmd.write_bulk.entries[0].item_handle == 34
+    assert cmd.write_bulk.entries[0].user_id == 99
+
+
+@pytest.mark.asyncio
+async def test_session_write2_bulk_sends_expected_request_shape() -> None:
+    stub = _BulkFakeStub()
+    stub.set_invoke_replies(
+        [
+            pb.MxCommandReply(
+                session_id="session-1",
+                kind=pb.MX_COMMAND_KIND_WRITE2_BULK,
+                protocol_status=pb.ProtocolStatus(code=pb.PROTOCOL_STATUS_CODE_OK),
+                write2_bulk=pb.BulkWriteReply(
+                    results=[pb.BulkWriteResult(was_successful=True)],
+                ),
+            ),
+        ],
+    )
+    client = await GatewayClient.connect(
+        ClientOptions(endpoint="fake", api_key="mxgw_test_secret", plaintext=True),
+        stub=stub,
+    )
+    session = await client.open_session()
+
+    from zb_mom_ww_mxgateway.values import to_mx_value
+
+    entries = [
+        pb.Write2BulkEntry(
+            item_handle=34,
+            user_id=99,
+            value=to_mx_value(123),
+            timestamp_value=to_mx_value(1.5),
+        ),
+    ]
+    results = await session.write2_bulk(12, entries)
+
+    assert results[0].was_successful is True
+    cmd = stub.invoke.requests[0].command
+    assert cmd.kind == pb.MX_COMMAND_KIND_WRITE2_BULK
+    assert cmd.write2_bulk.server_handle == 12
+    assert cmd.write2_bulk.entries[0].item_handle == 34
+
+
+@pytest.mark.asyncio
+async def test_session_write_secured_bulk_sends_expected_request_shape() -> None:
+    stub = _BulkFakeStub()
+    stub.set_invoke_replies(
+        [
+            pb.MxCommandReply(
+                session_id="session-1",
+                kind=pb.MX_COMMAND_KIND_WRITE_SECURED_BULK,
+                protocol_status=pb.ProtocolStatus(code=pb.PROTOCOL_STATUS_CODE_OK),
+                write_secured_bulk=pb.BulkWriteReply(
+                    results=[pb.BulkWriteResult(was_successful=True)],
+                ),
+            ),
+        ],
+    )
+    client = await GatewayClient.connect(
+        ClientOptions(endpoint="fake", api_key="mxgw_test_secret", plaintext=True),
+        stub=stub,
+    )
+    session = await client.open_session()
+
+    from zb_mom_ww_mxgateway.values import to_mx_value
+
+    entries = [
+        pb.WriteSecuredBulkEntry(
+            item_handle=34,
+            current_user_id=42,
+            verifier_user_id=43,
+            value=to_mx_value("secret"),
+        ),
+    ]
+    results = await session.write_secured_bulk(12, entries)
+
+    assert results[0].was_successful is True
+    cmd = stub.invoke.requests[0].command
+    assert cmd.kind == pb.MX_COMMAND_KIND_WRITE_SECURED_BULK
+    assert cmd.write_secured_bulk.server_handle == 12
+    assert cmd.write_secured_bulk.entries[0].current_user_id == 42
+    assert cmd.write_secured_bulk.entries[0].verifier_user_id == 43
+
+
+@pytest.mark.asyncio
+async def test_session_write_secured2_bulk_sends_expected_request_shape() -> None:
+    stub = _BulkFakeStub()
+    stub.set_invoke_replies(
+        [
+            pb.MxCommandReply(
+                session_id="session-1",
+                kind=pb.MX_COMMAND_KIND_WRITE_SECURED2_BULK,
+                protocol_status=pb.ProtocolStatus(code=pb.PROTOCOL_STATUS_CODE_OK),
+                write_secured2_bulk=pb.BulkWriteReply(
+                    results=[pb.BulkWriteResult(was_successful=True)],
+                ),
+            ),
+        ],
+    )
+    client = await GatewayClient.connect(
+        ClientOptions(endpoint="fake", api_key="mxgw_test_secret", plaintext=True),
+        stub=stub,
+    )
+    session = await client.open_session()
+
+    from zb_mom_ww_mxgateway.values import to_mx_value
+
+    entries = [
+        pb.WriteSecured2BulkEntry(
+            item_handle=34,
+            current_user_id=42,
+            verifier_user_id=43,
+            value=to_mx_value("secret"),
+            timestamp_value=to_mx_value(1.5),
+        ),
+    ]
+    results = await session.write_secured2_bulk(12, entries)
+
+    assert results[0].was_successful is True
+    cmd = stub.invoke.requests[0].command
+    assert cmd.kind == pb.MX_COMMAND_KIND_WRITE_SECURED2_BULK
+    assert cmd.write_secured2_bulk.entries[0].current_user_id == 42
+
+
+@pytest.mark.asyncio
+async def test_stream_alarms_yields_feed_messages_and_cancels_on_close() -> None:
+    transitions = [
+        pb.AlarmFeedMessage(
+            transition=pb.OnAlarmTransitionEvent(
+                alarm_full_reference="Tank01.Level.HiHi",
+                transition_kind=pb.ALARM_TRANSITION_KIND_RAISE,
+            ),
+        ),
+    ]
+    stream = _AlarmFakeStream(transitions)
+    stub = _BulkFakeStub()
+    stub.set_alarm_stream(stream)
+    client = await GatewayClient.connect(
+        ClientOptions(endpoint="fake", api_key="mxgw_test_secret", plaintext=True),
+        stub=stub,
+    )
+
+    iterator = client.stream_alarms(pb.StreamAlarmsRequest(alarm_filter_prefix="Tank01."))
+    first = await anext(iterator)
+    await iterator.aclose()
+
+    assert first.transition.alarm_full_reference == "Tank01.Level.HiHi"
+    assert stream.cancelled
+    assert stub.stream_alarms_metadata == (("authorization", "Bearer mxgw_test_secret"),)
+    assert stub.stream_alarms_request.alarm_filter_prefix == "Tank01."
+
+
+# ---- CLI happy-path coverage for the new subcommands ----
+
+
+def _install_fake_connect(monkeypatch, stub: Any) -> dict[str, Any]:
+    """Patch `GatewayClient.connect` so the CLI uses the supplied fake stub."""
+
+    captured: dict[str, Any] = {}
+    real_connect = GatewayClient.connect
+
+    @classmethod
+    async def _spy_connect(cls, options: ClientOptions, **kwargs: Any) -> GatewayClient:
+        captured["options"] = options
+        return await real_connect(options, stub=stub)
+
+    monkeypatch.setattr(GatewayClient, "connect", _spy_connect)
+    return captured
+
+
+def test_cli_read_bulk_happy_path(monkeypatch) -> None:
+    stub = _BulkFakeStub()
+    stub.set_invoke_replies(
+        [
+            pb.MxCommandReply(
+                session_id="session-1",
+                kind=pb.MX_COMMAND_KIND_READ_BULK,
+                protocol_status=pb.ProtocolStatus(code=pb.PROTOCOL_STATUS_CODE_OK),
+                read_bulk=pb.BulkReadReply(
+                    results=[
+                        pb.BulkReadResult(
+                            tag_address="Tank01.Level",
+                            was_successful=True,
+                        ),
+                    ],
+                ),
+            ),
+        ],
+    )
+    _install_fake_connect(monkeypatch, stub)
+
+    runner = CliRunner()
+    result = runner.invoke(
+        main,
+        [
+            "read-bulk",
+            "--endpoint",
+            "localhost:5000",
+            "--plaintext",
+            "--session-id",
+            "session-1",
+            "--server-handle",
+            "12",
+            "--items",
+            "Tank01.Level",
+            "--timeout-ms",
+            "1500",
+            "--json",
+        ],
+    )
+
+    assert result.exit_code == 0, result.output
+    payload = json.loads(result.output)
+    assert payload["results"][0]["tagAddress"] == "Tank01.Level"
+
+
+def test_cli_write_bulk_happy_path(monkeypatch) -> None:
+    stub = _BulkFakeStub()
+    stub.set_invoke_replies(
+        [
+            pb.MxCommandReply(
+                session_id="session-1",
+                kind=pb.MX_COMMAND_KIND_WRITE_BULK,
+                protocol_status=pb.ProtocolStatus(code=pb.PROTOCOL_STATUS_CODE_OK),
+                write_bulk=pb.BulkWriteReply(
+                    results=[pb.BulkWriteResult(was_successful=True)],
+                ),
+            ),
+        ],
+    )
+    _install_fake_connect(monkeypatch, stub)
+
+    runner = CliRunner()
+    result = runner.invoke(
+        main,
+        [
+            "write-bulk",
+            "--endpoint",
+            "localhost:5000",
+            "--plaintext",
+            "--session-id",
+            "session-1",
+            "--server-handle",
+            "12",
+            "--item-handles",
+            "34",
+            "--values",
+            "123",
+            "--type",
+            "int32",
+            "--json",
+        ],
+    )
+
+    assert result.exit_code == 0, result.output
+    payload = json.loads(result.output)
+    assert payload["results"][0]["wasSuccessful"] is True
+    cmd = stub.invoke.requests[0].command
+    assert cmd.kind == pb.MX_COMMAND_KIND_WRITE_BULK
+
+
+def test_cli_stream_alarms_happy_path(monkeypatch) -> None:
+    transitions = [
+        pb.AlarmFeedMessage(
+            transition=pb.OnAlarmTransitionEvent(
+                alarm_full_reference="Tank01.Level.HiHi",
+                transition_kind=pb.ALARM_TRANSITION_KIND_RAISE,
+            ),
+        ),
+    ]
+    stream = _AlarmFakeStream(transitions)
+    stub = _BulkFakeStub()
+    stub.set_alarm_stream(stream)
+    _install_fake_connect(monkeypatch, stub)
+
+    runner = CliRunner()
+    result = runner.invoke(
+        main,
+        [
+            "stream-alarms",
+            "--endpoint",
+            "localhost:5000",
+            "--plaintext",
+            "--max-messages",
+            "1",
+            "--timeout",
+            "5.0",
+            "--filter-prefix",
+            "Tank01.",
+            "--json",
+        ],
+    )
+
+    assert result.exit_code == 0, result.output
+    payload = json.loads(result.output)
+    assert payload["messages"][0]["transition"]["alarmFullReference"] == "Tank01.Level.HiHi"
+
+
+def test_cli_acknowledge_alarm_happy_path(monkeypatch) -> None:
+    stub = _BulkFakeStub()
+    stub.acknowledge_alarm = _BulkFakeUnary(
+        [
+            pb.AcknowledgeAlarmReply(
+                correlation_id="corr-1",
+                protocol_status=pb.ProtocolStatus(code=pb.PROTOCOL_STATUS_CODE_OK),
+                status=pb.MxStatusProxy(success=1, category=pb.MX_STATUS_CATEGORY_OK),
+            ),
+        ],
+    )
+    stub.AcknowledgeAlarm = stub.acknowledge_alarm
+    _install_fake_connect(monkeypatch, stub)
+
+    runner = CliRunner()
+    result = runner.invoke(
+        main,
+        [
+            "acknowledge-alarm",
+            "--endpoint",
+            "localhost:5000",
+            "--plaintext",
+            "--reference",
+            "Tank01.Level.HiHi",
+            "--comment",
+            "investigating",
+            "--operator",
+            "alice",
+            "--json",
+        ],
+    )
+
+    assert result.exit_code == 0, result.output
+    captured_request = stub.acknowledge_alarm.requests[0]
+    assert captured_request.alarm_full_reference == "Tank01.Level.HiHi"
+    assert captured_request.comment == "investigating"
+    assert captured_request.operator_user == "alice"
+
+
+# ---------------------------------------------------------------------------
+# Client.Python-026 — `import time` at module scope; tighter cleanup excepts.
+# ---------------------------------------------------------------------------
+
+
+def test_commands_module_imports_time_at_module_scope() -> None:
+    """`time` must be imported at module scope, not inside `_bench_read_bulk`.
+
+    `inspect.getsource(_bench_read_bulk)` must not contain a function-local
+    ``import time`` statement.
+    """
+
+    import inspect
+
+    source = inspect.getsource(cli_commands._bench_read_bulk)
+    # The function body must NOT contain a function-local `import time` line.
+    for line in source.splitlines():
+        stripped = line.strip()
+        assert stripped != "import time", (
+            f"_bench_read_bulk must not have function-local `import time`: {line!r}"
+        )
+
+    # And the module-level `time` attribute must be present.
+    assert hasattr(cli_commands, "time"), (
+        "`time` must be imported at module scope on commands.py"
+    )
+    assert cli_commands.time is _time_module_ref
+
+
+def test_commands_module_bench_read_bulk_does_not_use_bare_except_pass() -> None:
+    """The two `except Exception: pass` cleanup blocks in `_bench_read_bulk`
+    must be removed in favour of either logging or a narrower exception class.
+    """
+
+    import inspect
+
+    source = inspect.getsource(cli_commands._bench_read_bulk)
+    # Reject the bare `except Exception:` followed by `pass` pattern in
+    # `_bench_read_bulk`. We tolerate `except Exception as <name>:` because the
+    # fix logs the exception.
+    pattern = re.compile(r"except\s+Exception\s*:\s*\n\s*pass\b")
+    assert not pattern.search(source), (
+        "_bench_read_bulk cleanup blocks must log or narrow the except clause"
+    )

clients/python/tests/test_tls.py

@@ -0,0 +1,165 @@
+"""TLS behaviour tests for ``create_channel``.
+
+These spin up a real loopback ``grpc.aio`` server with a freshly generated
+self-signed certificate (carrying a ``localhost`` SAN, mirroring the gateway's
+auto-generated cert) and assert the lenient TOFU default lets a client connect
+without any CA configured.
+
+Marked ``tls`` and skipped unless ``MXGATEWAY_RUN_TLS_TESTS=1`` because loopback
+TLS handshakes can be timing-flaky on shared CI runners. This mirrors how the
+suite gates anything that depends on real sockets rather than fakes.
+"""
+
+from __future__ import annotations
+
+import os
+import shutil
+import socket
+import ssl
+import subprocess
+import tempfile
+from collections.abc import AsyncIterator
+from pathlib import Path
+
+import grpc
+import pytest
+import pytest_asyncio
+
+from zb_mom_ww_mxgateway import ClientOptions
+from zb_mom_ww_mxgateway.errors import MxGatewayTransportError
+from zb_mom_ww_mxgateway.generated import mxaccess_gateway_pb2 as pb
+from zb_mom_ww_mxgateway.generated import mxaccess_gateway_pb2_grpc as pb_grpc
+from zb_mom_ww_mxgateway.options import create_channel
+
+pytestmark = pytest.mark.tls
+
+_RUN_TLS_TESTS = os.environ.get("MXGATEWAY_RUN_TLS_TESTS") == "1"
+_OPENSSL = shutil.which("openssl")
+
+requires_tls = pytest.mark.skipif(
+    not _RUN_TLS_TESTS,
+    reason="set MXGATEWAY_RUN_TLS_TESTS=1 to run loopback TLS tests",
+)
+requires_openssl = pytest.mark.skipif(
+    _OPENSSL is None,
+    reason="openssl CLI is required to generate a self-signed test certificate",
+)
+
+
+def _generate_self_signed_cert(directory: Path) -> tuple[Path, Path]:
+    """Generate a self-signed cert/key pair with a ``localhost`` SAN."""
+    key_path = directory / "server.key"
+    cert_path = directory / "server.crt"
+    subprocess.run(
+        [
+            str(_OPENSSL),
+            "req",
+            "-x509",
+            "-newkey",
+            "rsa:2048",
+            "-nodes",
+            "-keyout",
+            str(key_path),
+            "-out",
+            str(cert_path),
+            "-days",
+            "1",
+            "-subj",
+            "/CN=mxgateway-test",
+            "-addext",
+            "subjectAltName=DNS:localhost,IP:127.0.0.1",
+        ],
+        check=True,
+        capture_output=True,
+    )
+    return cert_path, key_path
+
+
+def _free_port() -> int:
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
+        sock.bind(("127.0.0.1", 0))
+        return int(sock.getsockname()[1])
+
+
+class _StaticGatewayServicer(pb_grpc.MxAccessGatewayServicer):
+    """Minimal servicer answering ``OpenSession`` with a fixed session id."""
+
+    async def OpenSession(  # noqa: N802 - generated gRPC method name
+        self, request: pb.OpenSessionRequest, context: object
+    ) -> pb.OpenSessionReply:
+        return pb.OpenSessionReply(session_id="tls-session-1")
+
+
+@pytest_asyncio.fixture
+async def tls_server() -> AsyncIterator[int]:
+    with tempfile.TemporaryDirectory() as tmp:
+        cert_path, key_path = _generate_self_signed_cert(Path(tmp))
+        credentials = grpc.ssl_server_credentials(
+            [(key_path.read_bytes(), cert_path.read_bytes())]
+        )
+        server = grpc.aio.server()
+        pb_grpc.add_MxAccessGatewayServicer_to_server(_StaticGatewayServicer(), server)
+        port = _free_port()
+        server.add_secure_port(f"127.0.0.1:{port}", credentials)
+        await server.start()
+        try:
+            yield port
+        finally:
+            await server.stop(grace=None)
+
+
+@requires_tls
+@requires_openssl
+@pytest.mark.asyncio
+async def test_default_tls_connects_via_tofu(tls_server: int) -> None:
+    """Default TLS options (no CA) connect by pinning the presented cert."""
+    options = ClientOptions(
+        endpoint=f"127.0.0.1:{tls_server}",
+        api_key="mxgw_test_secret",
+    )
+    channel = create_channel(options)
+    try:
+        stub = pb_grpc.MxAccessGatewayStub(channel)
+        reply = await stub.OpenSession(pb.OpenSessionRequest(), timeout=10)
+        assert reply.session_id == "tls-session-1"
+    finally:
+        await channel.close()
+
+
+def test_split_authority_parses_host_and_port() -> None:
+    from zb_mom_ww_mxgateway.options import _split_authority
+
+    assert _split_authority("https://10.0.0.5:5120") == ("10.0.0.5", 5120)
+    assert _split_authority("localhost:5120") == ("localhost", 5120)
+    assert _split_authority(":5120") == ("localhost", 5120)
+
+
+def test_split_authority_strips_ipv6_brackets() -> None:
+    from zb_mom_ww_mxgateway.options import _split_authority
+
+    # Bracketed IPv6 with port — brackets must be removed for ssl.get_server_certificate
+    assert _split_authority("[::1]:5120") == ("::1", 5120)
+    # Bare bracketed IPv6 (no port) — default port 443
+    assert _split_authority("[::1]") == ("::1", 443)
+    # Scheme-prefixed bracketed IPv6
+    assert _split_authority("grpc://[::1]:5120") == ("::1", 5120)
+
+
+def test_tofu_connect_failure_raises_transport_error() -> None:
+    """A failed cert pre-fetch surfaces the client's transport error type."""
+    options = ClientOptions(endpoint=f"127.0.0.1:{_free_port()}")
+    with pytest.raises(MxGatewayTransportError) as excinfo:
+        create_channel(options)
+    assert options.endpoint in str(excinfo.value)
+
+
+def test_require_certificate_validation_uses_system_trust() -> None:
+    """``require_certificate_validation`` must not attempt a TOFU pre-fetch."""
+    # Pointing at a closed port: with system-trust the channel is created lazily
+    # (no eager pre-fetch), so create_channel must succeed without connecting.
+    options = ClientOptions(
+        endpoint=f"127.0.0.1:{_free_port()}",
+        require_certificate_validation=True,
+    )
+    channel = create_channel(options)
+    assert isinstance(channel, grpc.aio.Channel)

clients/rust/.cargo/config.toml

@@ -1,9 +1,22 @@
-[target.'cfg(windows)']
-# Bump the default 1 MB Windows stack to 8 MB. clap-derive builds a large
-# Command enum in this CLI (one variant per subcommand, each carrying flag
-# args); in debug builds the enum is materialized on the stack without
+# MSVC-only: bump the default 1 MB Windows stack to 8 MB. clap-derive builds
+# a large Command enum in this CLI (one variant per subcommand, each carrying
+# flag args); in debug builds the enum is materialized on the stack without
 # optimization and overflows the default Windows main-thread stack before
-# even reaching our code. Release builds are unaffected but the e2e matrix
-# drives the CLI through `cargo run` (debug), so the link-arg ships with
-# every dev-time invocation.
+# even reaching our code.
+#
+# The /STACK: link-arg goes into the PE header's IMAGE_OPTIONAL_HEADER.
+# SizeOfStackReserve at link time and applies to both debug and release
+# builds — release artifacts ship with the same 8 MB stack reservation. At
+# runtime the optimizer elides the enum from the stack frame, so release
+# builds would not overflow without this setting; it is kept on for them so
+# both build flavours produce binaries with identical stack metadata.
+#
+# `/STACK:` is an MSVC-linker (`link.exe` / `lld-link`) directive. The
+# `target_env = "msvc"` selector below scopes the rustflag to the MSVC
+# toolchain so `x86_64-pc-windows-gnu` (mingw) builds, which route link
+# args through the GNU linker and reject `/STACK:`, are unaffected.
+[target.'cfg(all(windows, target_env = "msvc"))']
 rustflags = ["-C", "link-arg=/STACK:8388608"]
+
+[registries.dohertj2-gitea]
+index = "sparse+https://gitea.dohertylan.com/api/packages/dohertj2/cargo/"

clients/rust/Cargo.toml

@@ -2,7 +2,16 @@
 name = "zb-mom-ww-mxgateway-client"
 version = "0.1.0"
 edition = "2021"
-publish = false
+authors = ["Joseph Doherty"]
+description = "Async Rust client for the MxAccessGateway gRPC service, including a lazy-browse walker over the Galaxy Repository hierarchy."
+license = "Proprietary"
+repository = "https://gitea.dohertylan.com/dohertj2/mxaccessgw"
+homepage = "https://gitea.dohertylan.com/dohertj2/mxaccessgw"
+documentation = "https://gitea.dohertylan.com/dohertj2/mxaccessgw"
+readme = "README.md"
+keywords = ["mxaccess", "mxgateway", "grpc", "client", "archestra"]
+categories = ["api-bindings", "asynchronous"]
+publish = ["dohertj2-gitea"]
 build = "build.rs"
 
 [workspace]
@@ -12,7 +21,10 @@ resolver = "2"
 [workspace.package]
 edition = "2021"
 version = "0.1.0"
-publish = false
+authors = ["Joseph Doherty"]
+license = "Proprietary"
+repository = "https://gitea.dohertylan.com/dohertj2/mxaccessgw"
+publish = ["dohertj2-gitea"]
 
 [workspace.dependencies]
 clap = { version = "4.5.53", features = ["derive"] }

clients/rust/README.md

@@ -76,6 +76,19 @@ types.
 cargo run -p mxgw-cli -- smoke --endpoint https://mxgateway.example.local:5001 --tls --ca-file C:\certs\mxgateway-ca.pem --server-name-override mxgateway.example.local --api-key-env MXGATEWAY_API_KEY --item TestChildObject.TestInt --json
 ```
 
+### TLS trust (pin-only)
+
+The gateway can auto-generate its own self-signed certificate (it has no PKI).
+Unlike the other clients, the Rust client is **not** lenient: tonic 0.13.1
+exposes no public hook to inject a custom certificate verifier, so TLS over Rust
+is pin-only. A TLS connection requires either `--ca-file` /
+`ClientOptions::with_ca_file(...)` to pin a CA (export the gateway's self-signed
+certificate and pin it), or `--require-certificate-validation` /
+`with_require_certificate_validation(true)` to verify against the system trust
+roots. TLS with neither set fails `connect` with a clear, actionable error rather
+than accepting the certificate. See
+[Gateway Configuration](../../docs/GatewayConfiguration.md#automatic-self-signed-certificate).
+
 ## Library Surface
 
 `ClientOptions` configures endpoint, API key, plaintext or TLS transport,
@@ -138,6 +151,50 @@ cargo run -p mxgw-cli -- galaxy last-deploy-time --endpoint http://localhost:500
 cargo run -p mxgw-cli -- galaxy discover-hierarchy --endpoint http://localhost:5000 --api-key-env MXGATEWAY_API_KEY --json
 ```
 
+### Browsing lazily
+
+For UI trees or OPC UA bridges, use `browse_children` to walk one level at a
+time instead of paging the full hierarchy. Pass a default request for root
+objects; subsequent calls set `parent_gobject_id`, `parent_tag_name`, or
+`parent_contained_path`. Filter fields match `discover_hierarchy`. Each response
+pairs `children` with `child_has_children` so you know which nodes to expand. See
+[Galaxy Repository](../../docs/GalaxyRepository.md#browsechildren) for full
+request and filter semantics.
+
+```rust
+use zb_mom_ww_mxgateway_client::generated::galaxy_repository::v1::BrowseChildrenRequest;
+
+let reply = galaxy.browse_children(BrowseChildrenRequest::default()).await?.into_inner();
+for (child, has_children) in reply.children.iter().zip(reply.child_has_children.iter()) {
+    println!("{} expand={}", child.tag_name, has_children);
+}
+```
+
+#### High-level walker
+
+For UI trees, the client provides a `LazyBrowseNode` walker that handles
+sibling pagination and the `child_has_children` hint for you:
+
+```rust
+let mut client = GalaxyClient::connect(
+    ClientOptions::new("http://localhost:5000").with_api_key(ApiKey::new(api_key)),
+).await?;
+let roots = client.browse(None).await?;
+for root in &roots {
+    if root.has_children_hint() {
+        root.expand().await?;
+    }
+    for child in root.children().await {
+        let kind = if child.has_children_hint() { "has children" } else { "leaf" };
+        println!("{} ({kind})", child.object().tag_name);
+    }
+}
+```
+
+`expand` is idempotent — calling it twice fires only one RPC,
+and is safe under concurrent callers. To refresh after a Galaxy redeploy, call
+`browse` again from the root.
+
 ### Watching deploy events
 
 `watch_deploy_events` opens the `WatchDeployEvents` server stream. The
@@ -192,3 +249,27 @@ cargo run -p mxgw-cli -- smoke --endpoint $env:MXGATEWAY_ENDPOINT --plaintext --
 - [Client Proto Generation](../../docs/ClientProtoGeneration.md)
 - [Rust Client Detailed Design](./RustClientDesign.md)
 - [Rust Style Guide](../../docs/style-guides/RustStyleGuide.md)
+
+## Installing from the Gitea Cargo registry
+
+The crate publishes to the internal Gitea Cargo registry. Register the
+registry once in your global `~/.cargo/config.toml`:
+
+```toml
+[registries.dohertj2-gitea]
+index = "sparse+https://gitea.dohertylan.com/api/packages/dohertj2/cargo/"
+```
+
+Authentication: cargo reads credentials from `~/.cargo/credentials.toml`:
+
+```toml
+[registries.dohertj2-gitea]
+token = "Bearer <your-gitea-token>"
+```
+
+Then add the dependency:
+
+```toml
+[dependencies]
+zb-mom-ww-mxgateway-client = { version = "0.1.0", registry = "dohertj2-gitea" }
+```

clients/rust/RustClientDesign.md

@@ -56,7 +56,23 @@ Expected dependencies:
 - `clap`
 - `serde`
 - `serde_json`
-- `tracing`
+
+## Windows Build Notes
+
+`clients/rust/.cargo/config.toml` carries an MSVC-scoped rustflag that bumps
+the default 1 MB Windows main-thread stack to 8 MB
+(`-C link-arg=/STACK:8388608`, under `cfg(all(windows, target_env = "msvc"))`).
+The setting is required because clap-derive materialises a large `Command`
+enum (one variant per CLI subcommand, each carrying its flag args) on the
+main task's stack in debug builds, before any user code runs; the default 1
+MB stack overflows during enum construction. The `/STACK:` link-arg writes
+into the PE header's `IMAGE_OPTIONAL_HEADER.SizeOfStackReserve` at link
+time, so both debug and release artifacts ship with the same 8 MB stack
+reservation. Release builds would not overflow without it (the optimizer
+elides the enum from the stack frame), but the setting is kept on for
+release too so both build flavours produce binaries with identical stack
+metadata. The MSVC-only selector keeps `x86_64-pc-windows-gnu` (mingw)
+builds unaffected, since the GNU linker rejects `/STACK:`.
 
 ## Library API
 
@@ -94,18 +110,65 @@ impl Session {
     pub async fn add_item(&self, server_handle: i32, item: &str) -> Result<i32, Error>;
     pub async fn add_item2(&self, server_handle: i32, item: &str, context: &str) -> Result<i32, Error>;
     pub async fn advise(&self, server_handle: i32, item_handle: i32) -> Result<(), Error>;
+    pub async fn un_advise(&self, server_handle: i32, item_handle: i32) -> Result<(), Error>;
+    pub async fn remove_item(&self, server_handle: i32, item_handle: i32) -> Result<(), Error>;
     pub async fn add_item_bulk(&self, server_handle: i32, tag_addresses: Vec<String>) -> Result<Vec<SubscribeResult>, Error>;
     pub async fn advise_item_bulk(&self, server_handle: i32, item_handles: Vec<i32>) -> Result<Vec<SubscribeResult>, Error>;
     pub async fn remove_item_bulk(&self, server_handle: i32, item_handles: Vec<i32>) -> Result<Vec<SubscribeResult>, Error>;
     pub async fn un_advise_item_bulk(&self, server_handle: i32, item_handles: Vec<i32>) -> Result<Vec<SubscribeResult>, Error>;
     pub async fn subscribe_bulk(&self, server_handle: i32, tag_addresses: Vec<String>) -> Result<Vec<SubscribeResult>, Error>;
     pub async fn unsubscribe_bulk(&self, server_handle: i32, item_handles: Vec<i32>) -> Result<Vec<SubscribeResult>, Error>;
+    pub async fn read_bulk<S: AsRef<str>>(&self, server_handle: i32, tag_addresses: &[S], timeout_ms: u32) -> Result<Vec<BulkReadResult>, Error>;
     pub async fn write(&self, server_handle: i32, item_handle: i32, value: MxValue, user_id: i32) -> Result<(), Error>;
+    pub async fn write2(&self, server_handle: i32, item_handle: i32, value: MxValue, timestamp_value: MxValue, user_id: i32) -> Result<(), Error>;
+    pub async fn write_bulk(&self, server_handle: i32, entries: Vec<WriteBulkEntry>) -> Result<Vec<BulkWriteResult>, Error>;
+    pub async fn write2_bulk(&self, server_handle: i32, entries: Vec<Write2BulkEntry>) -> Result<Vec<BulkWriteResult>, Error>;
+    pub async fn write_secured_bulk(&self, server_handle: i32, entries: Vec<WriteSecuredBulkEntry>) -> Result<Vec<BulkWriteResult>, Error>;
+    pub async fn write_secured2_bulk(&self, server_handle: i32, entries: Vec<WriteSecured2BulkEntry>) -> Result<Vec<BulkWriteResult>, Error>;
     pub async fn events(&self) -> Result<impl Stream<Item = Result<MxEvent, Error>>, Error>;
     pub async fn close(&self) -> Result<(), Error>;
 }
 ```
 
+The per-entry credentials and timestamps (`user_id`, `timestamp_value`,
+`current_user_id`, `verifier_user_id`) live on the `WriteBulkEntry` /
+`Write2BulkEntry` / `WriteSecuredBulkEntry` / `WriteSecured2BulkEntry`
+structs rather than as trailing positional arguments on the bulk-write
+helpers, matching the protobuf shapes in `mxaccess_gateway.proto`.
+`read_bulk` is generic over `AsRef<str>` so callers can pass `&[String]` or
+`&[&str]` without cloning at the call site (the cross-language bench-read-bulk
+hot loop relies on this).
+
+The `session::next_correlation_id` helper is `pub` and re-exported at the
+crate root (`zb_mom_ww_mxgateway_client::next_correlation_id`); raw-RPC
+consumers like the `mxgw` CLI's `Ping`, `CloseSession`, `StreamAlarms`,
+`AcknowledgeAlarm`, and `BenchReadBulk` paths call it so every request
+carries a unique correlation id that gateway logs can tell apart from
+concurrent CLI smokes. The textual format is intentionally not part of the
+public contract.
+
+## Alarms
+
+`GatewayClient` exposes the gateway's session-less central alarm surface:
+
+```rust
+pub type AlarmFeedStream = Pin<Box<dyn Stream<Item = Result<AlarmFeedMessage, Error>> + Send + 'static>>;
+
+impl GatewayClient {
+    pub async fn stream_alarms(&self, request: StreamAlarmsRequest) -> Result<AlarmFeedStream, Error>;
+    pub async fn acknowledge_alarm(&self, request: AcknowledgeAlarmRequest) -> Result<AcknowledgeAlarmReply, Error>;
+}
+```
+
+`stream_alarms` opens with one `active_alarm` per currently-active alarm
+(the ConditionRefresh snapshot), then a single `snapshot_complete`, then a
+`transition` for every subsequent raise / acknowledge / clear. The feed is
+served by the gateway's always-on alarm monitor — no worker session is
+opened — so any number of clients may attach. Dropping the stream cancels
+the gRPC call cooperatively. `acknowledge_alarm` is idempotent at the
+MxAccess layer; the returned `AcknowledgeAlarmReply` carries the native
+MxStatus from the worker.
+
 ## Authentication
 
 Use a `tonic` interceptor or request extension layer to add:
@@ -126,6 +189,25 @@ Support:
 - custom CA file,
 - domain override.
 
+### Trust posture (pin-only)
+
+The gateway can serve a self-signed certificate it generates itself (it has no
+PKI). Rust is the **exception** to the lenient-by-default posture the other
+clients use: tonic 0.13.1 exposes no public hook to inject a custom certificate
+verifier, so the Rust client cannot accept an arbitrary certificate. TLS over the
+Rust client is therefore **pin-only** — it requires either:
+
+- `ClientOptions::with_ca_file(...)` to pin a CA (the supported path for the
+  gateway's self-signed certificate; export the certificate and pin it), or
+- `ClientOptions::with_require_certificate_validation(true)` to verify against the
+  system trust roots.
+
+With TLS enabled (`with_plaintext(false)`), no pinned CA, and certificate
+validation not required, `GatewayClient::connect` rejects the connection with a
+clear, actionable error pointing at `with_ca_file` /
+`require_certificate_validation` rather than silently accepting the certificate.
+The CLI exposes `--ca-file` and `--require-certificate-validation`.
+
 ## Streaming
 
 Expose event streams as a `Stream<Item = Result<MxEvent, Error>>`. Dropping the
@@ -140,19 +222,31 @@ Use `thiserror`:
 
 ```rust
 pub enum Error {
+    InvalidEndpoint { endpoint: String, detail: String },
+    InvalidArgument { name: String, detail: String },
     Transport(tonic::transport::Error),
-    Status(tonic::Status),
-    Authentication(String),
-    Authorization(String),
-    Session(SessionError),
-    Worker(WorkerError),
-    Command(CommandError),
-    MxAccess(MxAccessError),
-    Timeout,
-    Cancelled,
+    Authentication { message: String, status: Box<tonic::Status> },
+    Authorization { message: String, status: Box<tonic::Status> },
+    Timeout { message: String, status: Box<tonic::Status> },
+    Cancelled { message: String, status: Box<tonic::Status> },
+    Unavailable { message: String, status: Box<tonic::Status> },
+    Status(Box<tonic::Status>),
+    Command(Box<CommandError>),
+    ProtocolStatus { operation: &'static str, code: ProtocolStatusCode, message: String },
+    MalformedReply { detail: String },
 }
 ```
 
+- `Unavailable` classifies `Code::Unavailable` / `Code::ResourceExhausted`
+  so callers can distinguish transient failures from permanent ones.
+- `MalformedReply` surfaces the rare case where the gateway returned a
+  protocol-level `Ok` envelope but the typed payload arm was missing or did
+  not match the command kind (e.g. an `AddItemReply` body on a `WriteBulk`
+  reply). This is distinct from `ProtocolStatus` because the protocol-level
+  envelope itself succeeded; the corruption is in the payload shape.
+- `InvalidEndpoint` is raised before any RPC dispatch when the endpoint URL
+  or CA file fails to parse / load.
+
 Preserve raw command replies in `CommandError` where applicable.
 
 ## Test CLI
@@ -165,11 +259,39 @@ Commands:
 
 ```text
 mxgw version
-mxgw smoke --endpoint http://localhost:5000 --api-key-env MXGATEWAY_API_KEY --item TestChildObject.TestInt
+mxgw ping
+mxgw open-session
+mxgw close-session --session-id <id>
+mxgw register --session-id <id>
+mxgw add-item --session-id <id> --server-handle <h> --item <tag>
+mxgw advise --session-id <id> --server-handle <h> --item-handle <h>
+mxgw subscribe-bulk --session-id <id> --server-handle <h> --items <csv>
+mxgw unsubscribe-bulk --session-id <id> --server-handle <h> --item-handles <csv>
+mxgw read-bulk --session-id <id> --server-handle <h> --items <csv> [--timeout-ms <ms>]
+mxgw write --session-id <id> --server-handle 1 --item-handle 1 --value-type int32 --value 123
+mxgw write2 --session-id <id> --server-handle 1 --item-handle 1 --value-type int32 --value 123 --timestamp <iso>
+mxgw write-bulk --session-id <id> --server-handle <h> --item-handles <csv> --value-type <t> --values <csv>
+mxgw write2-bulk ...
+mxgw write-secured-bulk ...
+mxgw write-secured2-bulk ...
 mxgw stream-events --session-id <id> --json
-mxgw write --session-id <id> --server-handle 1 --item-handle 1 --type int32 --value 123
+mxgw stream-alarms [--filter-prefix <prefix>] [--max-events <n>]
+mxgw acknowledge-alarm --reference <full-ref> [--comment <txt>] [--operator <user>]
+mxgw bench-read-bulk [--duration-seconds <n>] [--warmup-seconds <n>] [--bulk-size <n>]
+mxgw smoke --endpoint http://localhost:5000 --api-key-env MXGATEWAY_API_KEY --item TestChildObject.TestInt
+mxgw batch
+mxgw galaxy {test-connection,last-deploy-time,discover-hierarchy,watch}
 ```
 
+`batch` reads commands from stdin one per line and dispatches each through
+the normal subcommand path; the loop terminates only on stdin EOF (blank
+lines log an empty-EOR-bracketed result and continue) so accidental empty
+lines from the PowerShell e2e harness do not silently end the session.
+`bench-read-bulk` opens its own session, subscribes to `--bulk-size` tags so
+the worker's value cache populates from OnDataChange events, hammers
+`read_bulk` in a tight loop for `--duration-seconds`, and emits the
+cross-language JSON shape that `scripts/bench-read-bulk.ps1` collates.
+
 JSON output should use `serde_json`.
 
 ## Unit Tests

clients/rust/crates/mxgw-cli/Cargo.toml

@@ -2,7 +2,7 @@
 name = "mxgw-cli"
 version.workspace = true
 edition.workspace = true
-publish.workspace = true
+publish = false
 
 [[bin]]
 name = "mxgw"

clients/rust/crates/mxgw-cli/src/main.rs

@@ -26,8 +26,8 @@ use zb_mom_ww_mxgateway_client::generated::mxaccess_gateway::v1::{
     WriteBulkEntry, WriteSecured2BulkEntry, WriteSecuredBulkEntry,
 };
 use zb_mom_ww_mxgateway_client::{
-    ApiKey, ClientOptions, Error, GalaxyClient, GatewayClient, MxValue, MxValueProjection,
-    CLIENT_VERSION, GATEWAY_PROTOCOL_VERSION, WORKER_PROTOCOL_VERSION,
+    next_correlation_id, ApiKey, ClientOptions, Error, GalaxyClient, GatewayClient, MxValue,
+    MxValueProjection, CLIENT_VERSION, GATEWAY_PROTOCOL_VERSION, WORKER_PROTOCOL_VERSION,
 };
 
 const MAX_AGGREGATE_EVENTS: usize = 10_000;
@@ -359,8 +359,9 @@ enum Command {
     /// write `__MXGW_BATCH_EOR__` to stdout after every result.  Errors are
     /// written as `{"error":"…","type":"error"}` JSON to stdout (not stderr)
     /// so the harness can parse them without interleaving stderr.  The loop
-    /// never terminates on command error; only stdin EOF (or an empty line)
-    /// ends the session.
+    /// never terminates on command error or accidental blank lines; only
+    /// stdin EOF ends the session — empty lines log an empty-EOR-bracketed
+    /// result and continue, matching the other four language CLIs.
     Batch,
     #[command(subcommand)]
     Galaxy(GalaxyCommand),
@@ -425,6 +426,11 @@ struct ConnectionArgs {
     ca_file: Option<PathBuf>,
     #[arg(long)]
     server_name_override: Option<String>,
+    /// Verify the server certificate against the system trust roots even
+    /// without a pinned CA. The Rust client's default is to require a CA
+    /// file (see `--ca-file`); set this flag to use system roots instead.
+    #[arg(long)]
+    require_certificate_validation: bool,
     #[arg(long, default_value_t = 10)]
     connect_timeout_seconds: u64,
     #[arg(long, default_value_t = 30)]
@@ -452,6 +458,9 @@ impl ConnectionArgs {
         if let Some(server_name_override) = &self.server_name_override {
             options = options.with_server_name_override(server_name_override);
         }
+        if self.require_certificate_validation {
+            options = options.with_require_certificate_validation(true);
+        }
 
         options
     }
@@ -503,7 +512,7 @@ async fn dispatch(command: Command) -> Result<(), Error> {
             let client = connect(connection).await?;
             let reply = client
                 .invoke(MxCommandRequest {
-                    client_correlation_id: "rust-cli-ping".to_owned(),
+                    client_correlation_id: next_correlation_id("cli-ping"),
                     command: Some(MxCommand {
                         kind: MxCommandKind::Ping as i32,
                         payload: Some(zb_mom_ww_mxgateway_client::generated::mxaccess_gateway::v1::mx_command::Payload::Ping(
@@ -550,7 +559,7 @@ async fn dispatch(command: Command) -> Result<(), Error> {
             let reply = client
                 .close_session_raw(CloseSessionRequest {
                     session_id,
-                    client_correlation_id: "rust-cli-close-session".to_owned(),
+                    client_correlation_id: next_correlation_id("cli-close-session"),
                 })
                 .await?;
             if json {
@@ -624,7 +633,7 @@ async fn dispatch(command: Command) -> Result<(), Error> {
             json,
         } => {
             let session = session_for(connection, session_id).await?;
-            let results = session.read_bulk(server_handle, items, timeout_ms).await?;
+            let results = session.read_bulk(server_handle, &items, timeout_ms).await?;
             print_read_bulk_results("read-bulk", &results, json);
         }
         Command::WriteBulk {
@@ -832,7 +841,7 @@ async fn dispatch(command: Command) -> Result<(), Error> {
             let client = connect(connection).await?;
             let mut stream = client
                 .stream_alarms(StreamAlarmsRequest {
-                    client_correlation_id: "rust-cli-stream-alarms".to_owned(),
+                    client_correlation_id: next_correlation_id("cli-stream-alarms"),
                     alarm_filter_prefix: filter_prefix.unwrap_or_default(),
                 })
                 .await?;
@@ -869,7 +878,7 @@ async fn dispatch(command: Command) -> Result<(), Error> {
             let client = connect(connection).await?;
             let reply = client
                 .acknowledge_alarm(AcknowledgeAlarmRequest {
-                    client_correlation_id: "rust-cli-acknowledge-alarm".to_owned(),
+                    client_correlation_id: next_correlation_id("cli-acknowledge-alarm"),
                     alarm_full_reference: reference,
                     comment,
                     operator_user: operator,
@@ -1113,8 +1122,15 @@ const BATCH_EOR: &str = "__MXGW_BATCH_EOR__";
 /// each through the normal [`dispatch`] path, and write [`BATCH_EOR`] to
 /// stdout after every result.  Errors are serialised as JSON to stdout so
 /// the harness can parse them without interleaving stderr.  The loop never
-/// terminates on command error; only stdin EOF or an empty line ends the
-/// session.
+/// terminates on command error or accidental blank lines; only stdin EOF
+/// ends the session — empty lines log an empty-EOR-bracketed result and
+/// continue.
+///
+/// `std::io::Stdin::lock().lines()` is a blocking iterator and the dispatch
+/// future is spawned on a separate tokio task so the runtime's main worker
+/// stays free.  When the runtime is multi-threaded the blocking read keeps
+/// one worker parked on `ReadFile`; that is acceptable here because no other
+/// future on the main task needs to run while we wait for the next command.
 async fn run_batch() -> Result<(), Error> {
     let stdin = io::stdin();
     let stdout = io::stdout();
@@ -1125,12 +1141,11 @@ async fn run_batch() -> Result<(), Error> {
             detail: e.to_string(),
         })?;
 
-        if line.is_empty() {
-            break;
-        }
-
         let parts: Vec<&str> = line.split_ascii_whitespace().collect();
         if parts.is_empty() {
+            // Empty / whitespace-only line: log an empty-EOR-bracketed
+            // result and continue so accidental blank lines from the
+            // PowerShell e2e harness do not silently end the session.
             println!("{BATCH_EOR}");
             stdout.lock().flush().ok();
             continue;
@@ -1388,6 +1403,7 @@ async fn run_bench_read_bulk(
     let bench_outcome = async {
         let server_handle = session.register(&client_name).await?;
         let subscribe_results = session.subscribe_bulk(server_handle, tags.clone()).await?;
+        let tags_ref: &[String] = &tags;
         let item_handles: Vec<i32> = subscribe_results
             .iter()
             .filter(|r| r.was_successful)
@@ -1401,7 +1417,7 @@ async fn run_bench_read_bulk(
         let warmup_deadline = Instant::now() + Duration::from_secs(warmup_seconds);
         while Instant::now() < warmup_deadline {
             let _ = session
-                .read_bulk(server_handle, tags.clone(), timeout_ms_param)
+                .read_bulk(server_handle, tags_ref, timeout_ms_param)
                 .await;
         }
 
@@ -1419,7 +1435,7 @@ async fn run_bench_read_bulk(
         while Instant::now() < steady_deadline {
             let call_start = Instant::now();
             let result = session
-                .read_bulk(server_handle, tags.clone(), timeout_ms_param)
+                .read_bulk(server_handle, tags_ref, timeout_ms_param)
                 .await;
             let elapsed = call_start.elapsed();
             latencies_ms.push(elapsed.as_secs_f64() * 1000.0);
@@ -1473,7 +1489,7 @@ async fn run_bench_read_bulk(
     let close_result = client
         .close_session_raw(CloseSessionRequest {
             session_id: session_id.clone(),
-            client_correlation_id: "rust-cli-bench-read-bulk-close".to_owned(),
+            client_correlation_id: next_correlation_id("cli-bench-read-bulk-close"),
         })
         .await;
 
@@ -2100,6 +2116,43 @@ mod tests {
         assert_eq!(super::BATCH_EOR, "__MXGW_BATCH_EOR__");
     }
 
+    #[test]
+    fn bench_percentile_summary_matches_hand_built_sample() {
+        // Hand-built sample with 5 values: 1, 2, 3, 4, 5.
+        let sample: Vec<f64> = vec![1.0, 2.0, 3.0, 4.0, 5.0];
+        let summary = super::percentile_summary(&sample);
+
+        assert_eq!(summary.max, 5.0);
+        // Mean = 15/5 = 3.0
+        assert!((summary.mean - 3.0).abs() < f64::EPSILON);
+        // p50: rank = 0.5 * 4 = 2 -> sorted[2] = 3.0
+        assert!((summary.p50 - 3.0).abs() < f64::EPSILON);
+        // p95: rank = 0.95 * 4 = 3.8 -> 4.0 + 0.8 * (5.0 - 4.0) = 4.8
+        assert!((summary.p95 - 4.8).abs() < f64::EPSILON);
+        // p99: rank = 0.99 * 4 = 3.96 -> 4.0 + 0.96 * 1.0 = 4.96
+        assert!((summary.p99 - 4.96).abs() < f64::EPSILON);
+    }
+
+    #[test]
+    fn bench_percentile_summary_handles_empty_sample() {
+        let summary = super::percentile_summary(&[]);
+        assert_eq!(summary.p50, 0.0);
+        assert_eq!(summary.p95, 0.0);
+        assert_eq!(summary.p99, 0.0);
+        assert_eq!(summary.max, 0.0);
+        assert_eq!(summary.mean, 0.0);
+    }
+
+    #[test]
+    fn bench_percentile_summary_handles_single_value_sample() {
+        let summary = super::percentile_summary(&[42.0]);
+        assert_eq!(summary.p50, 42.0);
+        assert_eq!(summary.p95, 42.0);
+        assert_eq!(summary.p99, 42.0);
+        assert_eq!(summary.max, 42.0);
+        assert_eq!(summary.mean, 42.0);
+    }
+
     #[test]
     fn rfc3339_parser_round_trips_z_and_offset_inputs() {
         // 2026-04-28T15:30:00Z = 1_777_995_000 (sanity-checked once below)

clients/rust/src/client.rs

@@ -6,10 +6,8 @@
 //! code should prefer [`GatewayClient::open_session`] and the [`Session`]
 //! handle it returns, rather than the `*_raw` methods.
 
-use std::fs;
-
 use tonic::codegen::InterceptedService;
-use tonic::transport::{Certificate, Channel, ClientTlsConfig};
+use tonic::transport::Channel;
 use tonic::Request;
 
 use crate::auth::AuthInterceptor;
@@ -21,7 +19,7 @@ use crate::generated::mxaccess_gateway::v1::{
     OpenSessionReply, OpenSessionRequest, QueryActiveAlarmsRequest, StreamAlarmsRequest,
     StreamEventsRequest,
 };
-use crate::options::ClientOptions;
+use crate::options::{build_tls_config, ClientOptions};
 use crate::session::Session;
 
 /// Generated gateway client wrapped in the auth interceptor that
@@ -78,18 +76,7 @@ impl GatewayClient {
             })?;
         endpoint = endpoint.connect_timeout(options.connect_timeout());
 
-        if !options.plaintext() {
-            let mut tls = ClientTlsConfig::new();
-            if let Some(server_name) = options.server_name_override() {
-                tls = tls.domain_name(server_name.to_owned());
-            }
-            if let Some(ca_file) = options.ca_file() {
-                let certificate = fs::read(ca_file).map_err(|source| Error::InvalidEndpoint {
-                    endpoint: options.endpoint().to_owned(),
-                    detail: format!("failed to read CA file {}: {source}", ca_file.display()),
-                })?;
-                tls = tls.ca_certificate(Certificate::from_pem(certificate));
-            }
+        if let Some(tls) = build_tls_config(&options)? {
             endpoint = endpoint.tls_config(tls)?;
         }
 

clients/rust/src/error.rs

@@ -106,6 +106,27 @@ pub enum Error {
         /// Detail message from the server.
         message: String,
     },
+
+    /// Gateway returned an `Ok` protocol status but the reply lacked the
+    /// expected typed payload (or carried the wrong payload arm). Distinct
+    /// from [`Error::ProtocolStatus`] because the protocol-level envelope
+    /// itself succeeded — the corruption is in the payload shape.
+    #[error("gateway returned a malformed reply: {detail}")]
+    MalformedReply {
+        /// Human-readable description of what was missing or mismatched.
+        detail: String,
+    },
+
+    /// Server returned `Unavailable` or `ResourceExhausted` — classify
+    /// transient failures separately from the catch-all [`Error::Status`].
+    #[error("gateway unavailable: {message}")]
+    Unavailable {
+        /// Redacted server-supplied detail message.
+        message: String,
+        /// Original `tonic::Status`.
+        #[source]
+        status: Box<tonic::Status>,
+    },
 }
 
 /// Wrapper around an [`MxCommandReply`] whose `protocol_status` reported a
@@ -174,6 +195,10 @@ impl From<tonic::Status> for Error {
                 message,
                 status: Box::new(status),
             },
+            Code::Unavailable | Code::ResourceExhausted => Self::Unavailable {
+                message,
+                status: Box::new(status),
+            },
             _ => Self::Status(Box::new(status)),
         }
     }

clients/rust/src/galaxy.rs

@@ -5,23 +5,143 @@
 //! read-only RPCs as Rust async methods. Generated Galaxy proto types are
 //! re-exported through [`crate::generated::galaxy_repository::v1`].
 
-use std::fs;
+use std::collections::HashSet;
+use std::sync::Arc;
 
 use prost_types::Timestamp;
+use tokio::sync::Mutex as AsyncMutex;
 use tonic::codegen::InterceptedService;
-use tonic::transport::{Certificate, Channel, ClientTlsConfig};
+use tonic::transport::Channel;
 use tonic::Request;
 
 use crate::auth::AuthInterceptor;
 use crate::error::Error;
 use crate::generated::galaxy_repository::v1::galaxy_repository_client::GalaxyRepositoryClient;
 use crate::generated::galaxy_repository::v1::{
-    DeployEvent, DiscoverHierarchyRequest, GalaxyObject, GetLastDeployTimeRequest,
-    TestConnectionRequest, WatchDeployEventsRequest,
+    browse_children_request, BrowseChildrenReply, BrowseChildrenRequest, DeployEvent,
+    DiscoverHierarchyRequest, GalaxyObject, GetLastDeployTimeRequest, TestConnectionRequest,
+    WatchDeployEventsRequest,
 };
-use crate::options::ClientOptions;
+use crate::options::{build_tls_config, ClientOptions};
 
 const DISCOVER_HIERARCHY_PAGE_SIZE: i32 = 5000;
+const BROWSE_CHILDREN_PAGE_SIZE: i32 = 500;
+
+/// Optional filter set forwarded to `GalaxyRepository.BrowseChildren`.
+///
+/// Mirrors the request-level filters on the wire: combined with AND so a child
+/// only appears when it satisfies every populated criterion. Construct via
+/// [`BrowseChildrenOptions::default`] and tweak the fields you care about.
+#[derive(Debug, Clone, Default)]
+pub struct BrowseChildrenOptions {
+    /// Restrict to objects whose `category_id` matches one of the supplied
+    /// Galaxy category identifiers. Empty means "no restriction".
+    pub category_ids: Vec<i32>,
+    /// Restrict to objects whose template chain contains every supplied
+    /// template name (case-sensitive substring match on each entry).
+    pub template_chain_contains: Vec<String>,
+    /// Restrict to objects whose tag name matches the supplied glob (SQL
+    /// `LIKE`-style on the server). `None` means "no glob filter".
+    pub tag_name_glob: Option<String>,
+    /// Optional tri-state hint for whether to populate `GalaxyObject.attributes`
+    /// on returned children. `None` falls back to the server default.
+    pub include_attributes: Option<bool>,
+    /// When `true`, only return children that own at least one alarm-bearing
+    /// attribute (matches `DiscoverHierarchy` semantics).
+    pub alarm_bearing_only: bool,
+    /// When `true`, only return children that own at least one historized
+    /// attribute (matches `DiscoverHierarchy` semantics).
+    pub historized_only: bool,
+}
+
+/// Lazy hierarchy node used by the walker built on top of `BrowseChildren`.
+///
+/// A node owns its [`GalaxyObject`], a hint as to whether the server believes
+/// it has at least one matching descendant under the active filter set, and an
+/// internal `expanded` flag protected by an async mutex. Calling [`expand`]
+/// the first time issues a paged `BrowseChildren` RPC; subsequent calls are
+/// no-ops so callers can poll without re-hitting the server.
+///
+/// `LazyBrowseNode` is cheap to clone — clones share state through an
+/// internal `Arc`, so expanding one clone makes the children visible to every
+/// other clone.
+///
+/// [`expand`]: LazyBrowseNode::expand
+pub struct LazyBrowseNode {
+    inner: Arc<LazyBrowseNodeInner>,
+}
+
+impl Clone for LazyBrowseNode {
+    fn clone(&self) -> Self {
+        Self {
+            inner: Arc::clone(&self.inner),
+        }
+    }
+}
+
+struct LazyBrowseNodeInner {
+    client: GalaxyClient,
+    object: GalaxyObject,
+    has_children_hint: bool,
+    options: BrowseChildrenOptions,
+    state: AsyncMutex<LazyBrowseNodeState>,
+}
+
+struct LazyBrowseNodeState {
+    children: Vec<LazyBrowseNode>,
+    is_expanded: bool,
+}
+
+impl LazyBrowseNode {
+    /// Borrow the [`GalaxyObject`] returned by the server for this node.
+    pub fn object(&self) -> &GalaxyObject {
+        &self.inner.object
+    }
+
+    /// Server-supplied hint: `true` when the child likely has at least one
+    /// further matching descendant. Useful to decide whether a UI should draw
+    /// an expand triangle without issuing the RPC up front.
+    pub fn has_children_hint(&self) -> bool {
+        self.inner.has_children_hint
+    }
+
+    /// Snapshot of the currently-known children. Empty until [`expand`] has
+    /// run at least once.
+    ///
+    /// [`expand`]: LazyBrowseNode::expand
+    pub async fn children(&self) -> Vec<LazyBrowseNode> {
+        self.inner.state.lock().await.children.clone()
+    }
+
+    /// Returns `true` once [`expand`] has populated this node's children.
+    ///
+    /// [`expand`]: LazyBrowseNode::expand
+    pub async fn is_expanded(&self) -> bool {
+        self.inner.state.lock().await.is_expanded
+    }
+
+    /// Populate this node's children by issuing a paged `BrowseChildren` RPC.
+    /// Subsequent calls are no-ops — the cached children stay in place and no
+    /// additional RPC is issued.
+    pub async fn expand(&self) -> Result<(), Error> {
+        let mut state = self.inner.state.lock().await;
+        if state.is_expanded {
+            return Ok(());
+        }
+
+        let mut client = self.inner.client.clone();
+        let new_children = client
+            .browse_children_inner(
+                Some(self.inner.object.gobject_id),
+                self.inner.options.clone(),
+            )
+            .await?;
+
+        state.children = new_children;
+        state.is_expanded = true;
+        Ok(())
+    }
+}
 
 /// Convenience alias for the generated Galaxy client wrapped in the
 /// authentication interceptor.
@@ -62,18 +182,7 @@ impl GalaxyClient {
             })?;
         endpoint = endpoint.connect_timeout(options.connect_timeout());
 
-        if !options.plaintext() {
-            let mut tls = ClientTlsConfig::new();
-            if let Some(server_name) = options.server_name_override() {
-                tls = tls.domain_name(server_name.to_owned());
-            }
-            if let Some(ca_file) = options.ca_file() {
-                let certificate = fs::read(ca_file).map_err(|source| Error::InvalidEndpoint {
-                    endpoint: options.endpoint().to_owned(),
-                    detail: format!("failed to read CA file {}: {source}", ca_file.display()),
-                })?;
-                tls = tls.ca_certificate(Certificate::from_pem(certificate));
-            }
+        if let Some(tls) = build_tls_config(&options)? {
             endpoint = endpoint.tls_config(tls)?;
         }
 
@@ -172,6 +281,99 @@ impl GalaxyClient {
         }
     }
 
+    /// Browse the top-level (root) objects of the hierarchy as
+    /// [`LazyBrowseNode`] instances. Pass [`BrowseChildrenOptions`] to
+    /// restrict the result set; the same filter is reused when callers expand
+    /// any returned node.
+    pub async fn browse(
+        &mut self,
+        options: Option<BrowseChildrenOptions>,
+    ) -> Result<Vec<LazyBrowseNode>, Error> {
+        let effective = options.unwrap_or_default();
+        self.browse_children_inner(None, effective).await
+    }
+
+    /// Issue a single `BrowseChildren` RPC and return the raw reply. Callers
+    /// that want to drive paging themselves (or inspect the cache sequence)
+    /// use this; high-level walking goes through [`browse`] and
+    /// [`LazyBrowseNode::expand`].
+    ///
+    /// [`browse`]: GalaxyClient::browse
+    pub async fn browse_children_raw(
+        &mut self,
+        request: BrowseChildrenRequest,
+    ) -> Result<BrowseChildrenReply, Error> {
+        let response = self
+            .inner
+            .browse_children(self.unary_request(request))
+            .await?;
+        Ok(response.into_inner())
+    }
+
+    pub(crate) async fn browse_children_inner(
+        &mut self,
+        parent_gobject_id: Option<i32>,
+        options: BrowseChildrenOptions,
+    ) -> Result<Vec<LazyBrowseNode>, Error> {
+        let mut nodes = Vec::new();
+        let mut page_token = String::new();
+        let mut seen_page_tokens: HashSet<String> = HashSet::new();
+        loop {
+            let parent = parent_gobject_id.map(browse_children_request::Parent::ParentGobjectId);
+            let request = BrowseChildrenRequest {
+                page_size: BROWSE_CHILDREN_PAGE_SIZE,
+                page_token: page_token.clone(),
+                category_ids: options.category_ids.clone(),
+                template_chain_contains: options.template_chain_contains.clone(),
+                tag_name_glob: options.tag_name_glob.clone().unwrap_or_default(),
+                include_attributes: options.include_attributes,
+                alarm_bearing_only: options.alarm_bearing_only,
+                historized_only: options.historized_only,
+                parent,
+            };
+
+            let reply = self.browse_children_raw(request).await?;
+            let hints = reply.child_has_children;
+            for (index, object) in reply.children.into_iter().enumerate() {
+                let hint = hints.get(index).copied().unwrap_or(false);
+                nodes.push(self.make_lazy_node(object, hint, options.clone()));
+            }
+
+            page_token = reply.next_page_token;
+            if page_token.is_empty() {
+                return Ok(nodes);
+            }
+            if !seen_page_tokens.insert(page_token.clone()) {
+                return Err(Error::InvalidArgument {
+                    name: "page_token".to_owned(),
+                    detail: format!(
+                        "galaxy browse children returned repeated page token `{page_token}`"
+                    ),
+                });
+            }
+        }
+    }
+
+    fn make_lazy_node(
+        &self,
+        object: GalaxyObject,
+        has_children_hint: bool,
+        options: BrowseChildrenOptions,
+    ) -> LazyBrowseNode {
+        LazyBrowseNode {
+            inner: Arc::new(LazyBrowseNodeInner {
+                client: self.clone(),
+                object,
+                has_children_hint,
+                options,
+                state: AsyncMutex::new(LazyBrowseNodeState {
+                    children: Vec::new(),
+                    is_expanded: false,
+                }),
+            }),
+        }
+    }
+
     /// Subscribe to the server-streamed deploy-event feed.
     ///
     /// The server emits a bootstrap event describing the current cache state
@@ -234,9 +436,10 @@ mod tests {
         GalaxyRepository, GalaxyRepositoryServer,
     };
     use crate::generated::galaxy_repository::v1::{
-        DeployEvent, DiscoverHierarchyReply, DiscoverHierarchyRequest, GalaxyAttribute,
-        GalaxyObject, GetLastDeployTimeReply, GetLastDeployTimeRequest, TestConnectionReply,
-        TestConnectionRequest, WatchDeployEventsRequest,
+        BrowseChildrenReply, BrowseChildrenRequest, DeployEvent, DiscoverHierarchyReply,
+        DiscoverHierarchyRequest, GalaxyAttribute, GalaxyObject, GetLastDeployTimeReply,
+        GetLastDeployTimeRequest, TestConnectionReply, TestConnectionRequest,
+        WatchDeployEventsRequest,
     };
 
     type DeployEventTx = mpsc::Sender<Result<DeployEvent, Status>>;
@@ -249,6 +452,9 @@ mod tests {
         objects: Mutex<Vec<GalaxyObject>>,
         discover_requests: Mutex<Vec<DiscoverHierarchyRequest>>,
         discover_replies: Mutex<std::collections::VecDeque<DiscoverHierarchyReply>>,
+        browse_children_calls: Mutex<Vec<BrowseChildrenRequest>>,
+        browse_children_replies: Mutex<std::collections::VecDeque<BrowseChildrenReply>>,
+        browse_children_errors: Mutex<Vec<Status>>,
         watch_requests: Mutex<Vec<WatchDeployEventsRequest>>,
         watch_events: Mutex<Vec<DeployEvent>>,
         watch_senders: Mutex<Vec<DeployEventTx>>,
@@ -279,7 +485,7 @@ mod tests {
             _request: Request<GetLastDeployTimeRequest>,
         ) -> Result<Response<GetLastDeployTimeReply>, Status> {
             let present = *self.state.present.lock().unwrap();
-            let time = self.state.last_deploy.lock().unwrap().clone();
+            let time = *self.state.last_deploy.lock().unwrap();
             Ok(Response::new(GetLastDeployTimeReply {
                 present,
                 time_of_last_deploy: time,
@@ -306,6 +512,28 @@ mod tests {
             }))
         }
 
+        async fn browse_children(
+            &self,
+            request: Request<BrowseChildrenRequest>,
+        ) -> Result<Response<BrowseChildrenReply>, Status> {
+            self.state
+                .browse_children_calls
+                .lock()
+                .unwrap()
+                .push(request.into_inner());
+            if let Some(error) = self.state.browse_children_errors.lock().unwrap().pop() {
+                return Err(error);
+            }
+            let reply = self
+                .state
+                .browse_children_replies
+                .lock()
+                .unwrap()
+                .pop_front()
+                .unwrap_or_default();
+            Ok(Response::new(reply))
+        }
+
         type WatchDeployEventsStream =
             Pin<Box<dyn tokio_stream::Stream<Item = Result<DeployEvent, Status>> + Send + 'static>>;
 
@@ -695,4 +923,295 @@ mod tests {
             "drop signal channel closed unexpectedly"
         );
     }
+
+    fn browse_obj(gid: i32, tag: &str, is_area: bool) -> GalaxyObject {
+        GalaxyObject {
+            gobject_id: gid,
+            tag_name: tag.to_owned(),
+            contained_name: String::new(),
+            browse_name: tag.to_owned(),
+            parent_gobject_id: 0,
+            is_area,
+            category_id: 0,
+            hosted_by_gobject_id: 0,
+            template_chain: Vec::new(),
+            attributes: Vec::new(),
+        }
+    }
+
+    fn build_browse_reply(
+        children: Vec<GalaxyObject>,
+        child_has_children: Vec<bool>,
+        cache_sequence: u64,
+    ) -> BrowseChildrenReply {
+        BrowseChildrenReply {
+            total_child_count: children.len() as i32,
+            cache_sequence,
+            children,
+            child_has_children,
+            next_page_token: String::new(),
+        }
+    }
+
+    #[tokio::test]
+    async fn browse_no_parent_returns_roots() {
+        let state = Arc::new(FakeState::default());
+        state
+            .browse_children_replies
+            .lock()
+            .unwrap()
+            .push_back(build_browse_reply(
+                vec![browse_obj(1, "Area_A", true), browse_obj(2, "Area_B", true)],
+                vec![true, false],
+                7,
+            ));
+        let endpoint = spawn_fake(state.clone()).await;
+        let mut client = GalaxyClient::connect(ClientOptions::new(endpoint))
+            .await
+            .unwrap();
+
+        let roots = client.browse(None).await.unwrap();
+
+        assert_eq!(roots.len(), 2);
+        assert_eq!(roots[0].object().tag_name, "Area_A");
+        assert!(roots[0].has_children_hint());
+        assert_eq!(roots[1].object().tag_name, "Area_B");
+        assert!(!roots[1].has_children_hint());
+
+        let calls = state.browse_children_calls.lock().unwrap();
+        assert_eq!(calls.len(), 1);
+        assert!(
+            calls[0].parent.is_none(),
+            "root browse must send an empty parent oneof, got {:?}",
+            calls[0].parent
+        );
+    }
+
+    #[tokio::test]
+    async fn browse_expand_populates_children_and_marks_expanded() {
+        let state = Arc::new(FakeState::default());
+        // First call: roots.
+        state
+            .browse_children_replies
+            .lock()
+            .unwrap()
+            .push_back(build_browse_reply(
+                vec![browse_obj(10, "Area_A", true)],
+                vec![true],
+                1,
+            ));
+        // Second call: children of gobject 10.
+        state
+            .browse_children_replies
+            .lock()
+            .unwrap()
+            .push_back(build_browse_reply(
+                vec![browse_obj(11, "Receiver_1", false)],
+                vec![false],
+                1,
+            ));
+        let endpoint = spawn_fake(state.clone()).await;
+        let mut client = GalaxyClient::connect(ClientOptions::new(endpoint))
+            .await
+            .unwrap();
+
+        let roots = client.browse(None).await.unwrap();
+        let root = roots.into_iter().next().expect("at least one root");
+        assert!(!root.is_expanded().await);
+
+        root.expand().await.unwrap();
+
+        assert!(root.is_expanded().await);
+        let children = root.children().await;
+        assert_eq!(children.len(), 1);
+        assert_eq!(children[0].object().tag_name, "Receiver_1");
+
+        let calls = state.browse_children_calls.lock().unwrap();
+        assert_eq!(calls.len(), 2);
+        let expand_call = &calls[1];
+        match expand_call.parent.as_ref().expect("expand sends parent") {
+            browse_children_request::Parent::ParentGobjectId(id) => assert_eq!(*id, 10),
+            other => panic!("expected ParentGobjectId variant, got {other:?}"),
+        }
+    }
+
+    #[tokio::test]
+    async fn browse_expand_idempotent_no_second_rpc() {
+        let state = Arc::new(FakeState::default());
+        state
+            .browse_children_replies
+            .lock()
+            .unwrap()
+            .push_back(build_browse_reply(
+                vec![browse_obj(20, "Area_X", true)],
+                vec![true],
+                1,
+            ));
+        state
+            .browse_children_replies
+            .lock()
+            .unwrap()
+            .push_back(build_browse_reply(
+                vec![browse_obj(21, "Leaf", false)],
+                vec![false],
+                1,
+            ));
+        let endpoint = spawn_fake(state.clone()).await;
+        let mut client = GalaxyClient::connect(ClientOptions::new(endpoint))
+            .await
+            .unwrap();
+
+        let roots = client.browse(None).await.unwrap();
+        let root = roots.into_iter().next().unwrap();
+        root.expand().await.unwrap();
+        let after_first = state.browse_children_calls.lock().unwrap().len();
+
+        // Calling expand a second time must NOT issue a new RPC.
+        root.expand().await.unwrap();
+
+        let after_second = state.browse_children_calls.lock().unwrap().len();
+        assert_eq!(
+            after_first, after_second,
+            "expand should be idempotent — no extra RPC the second time"
+        );
+        assert_eq!(root.children().await.len(), 1);
+    }
+
+    #[tokio::test]
+    async fn browse_expand_unknown_parent_returns_not_found_error() {
+        let state = Arc::new(FakeState::default());
+        // Root browse succeeds.
+        state
+            .browse_children_replies
+            .lock()
+            .unwrap()
+            .push_back(build_browse_reply(
+                vec![browse_obj(99, "GhostArea", true)],
+                vec![true],
+                1,
+            ));
+        let endpoint = spawn_fake(state.clone()).await;
+        let mut client = GalaxyClient::connect(ClientOptions::new(endpoint))
+            .await
+            .unwrap();
+
+        let roots = client.browse(None).await.unwrap();
+        let root = roots.into_iter().next().unwrap();
+
+        // Seed the NotFound only AFTER the root call so the FakeGalaxy's
+        // error stack doesn't intercept the initial browse.
+        state
+            .browse_children_errors
+            .lock()
+            .unwrap()
+            .push(Status::not_found("parent gobject 99 not present in cache"));
+
+        let error = root.expand().await.unwrap_err();
+
+        match &error {
+            Error::Status(status) => {
+                assert_eq!(status.code(), tonic::Code::NotFound);
+            }
+            other => panic!("expected Error::Status(NotFound), got {other:?}"),
+        }
+        // Failed expand must NOT mark the node as expanded — caller can retry.
+        assert!(!root.is_expanded().await);
+        assert!(root.children().await.is_empty());
+    }
+
+    #[tokio::test]
+    async fn browse_expand_multi_page_gathers_all_pages() {
+        let state = Arc::new(FakeState::default());
+        // First reply: roots.
+        state
+            .browse_children_replies
+            .lock()
+            .unwrap()
+            .push_back(build_browse_reply(
+                vec![browse_obj(30, "Plant", true)],
+                vec![true],
+                5,
+            ));
+        // Second reply: page 1 of children, with a next_page_token.
+        let mut page_one = build_browse_reply(
+            vec![
+                browse_obj(31, "Child_A", false),
+                browse_obj(32, "Child_B", false),
+            ],
+            vec![false, false],
+            5,
+        );
+        page_one.next_page_token = "cursor-2".to_owned();
+        page_one.total_child_count = 3;
+        state
+            .browse_children_replies
+            .lock()
+            .unwrap()
+            .push_back(page_one);
+        // Third reply: page 2 of children, with no next page.
+        state
+            .browse_children_replies
+            .lock()
+            .unwrap()
+            .push_back(build_browse_reply(
+                vec![browse_obj(33, "Child_C", false)],
+                vec![false],
+                5,
+            ));
+        let endpoint = spawn_fake(state.clone()).await;
+        let mut client = GalaxyClient::connect(ClientOptions::new(endpoint))
+            .await
+            .unwrap();
+
+        let roots = client.browse(None).await.unwrap();
+        let root = roots.into_iter().next().unwrap();
+        root.expand().await.unwrap();
+
+        let children = root.children().await;
+        assert_eq!(children.len(), 3);
+        assert_eq!(children[0].object().tag_name, "Child_A");
+        assert_eq!(children[1].object().tag_name, "Child_B");
+        assert_eq!(children[2].object().tag_name, "Child_C");
+
+        let calls = state.browse_children_calls.lock().unwrap();
+        // 1 root call + 2 paged expand calls = 3 total.
+        assert_eq!(calls.len(), 3);
+        assert_eq!(calls[1].page_token, "");
+        assert_eq!(calls[2].page_token, "cursor-2");
+    }
+
+    #[tokio::test]
+    async fn browse_with_filter_forwards_to_request() {
+        let state = Arc::new(FakeState::default());
+        state
+            .browse_children_replies
+            .lock()
+            .unwrap()
+            .push_back(build_browse_reply(Vec::new(), Vec::new(), 1));
+        let endpoint = spawn_fake(state.clone()).await;
+        let mut client = GalaxyClient::connect(ClientOptions::new(endpoint))
+            .await
+            .unwrap();
+
+        let options = BrowseChildrenOptions {
+            category_ids: vec![3, 5],
+            template_chain_contains: vec!["$DelmiaReceiver".to_owned()],
+            tag_name_glob: Some("Recv_*".to_owned()),
+            include_attributes: Some(true),
+            alarm_bearing_only: true,
+            historized_only: false,
+        };
+
+        let _ = client.browse(Some(options)).await.unwrap();
+
+        let calls = state.browse_children_calls.lock().unwrap();
+        assert_eq!(calls.len(), 1);
+        let req = &calls[0];
+        assert_eq!(req.category_ids, vec![3, 5]);
+        assert_eq!(req.template_chain_contains, vec!["$DelmiaReceiver"]);
+        assert_eq!(req.tag_name_glob, "Recv_*");
+        assert_eq!(req.include_attributes, Some(true));
+        assert!(req.alarm_bearing_only);
+        assert!(!req.historized_only);
+    }
 }

clients/rust/src/lib.rs

@@ -32,7 +32,7 @@ pub use galaxy::{DeployEventStream, GalaxyClient};
 #[doc(inline)]
 pub use options::ClientOptions;
 #[doc(inline)]
-pub use session::Session;
+pub use session::{next_correlation_id, Session};
 #[doc(inline)]
 pub use value::{MxArrayProjection, MxArrayValue, MxStatus, MxValue, MxValueProjection};
 #[doc(inline)]

clients/rust/src/options.rs

@@ -3,10 +3,14 @@
 //! chain of `with_*` setters; the `Debug` impl redacts the API key.
 
 use std::fmt;
+use std::fs;
 use std::path::PathBuf;
 use std::time::Duration;
 
+use tonic::transport::{Certificate, ClientTlsConfig};
+
 use crate::auth::ApiKey;
+use crate::error::Error;
 
 const DEFAULT_MAX_GRPC_MESSAGE_BYTES: usize = 16 * 1024 * 1024;
 
@@ -22,6 +26,7 @@ pub struct ClientOptions {
     api_key: Option<ApiKey>,
     plaintext: bool,
     ca_file: Option<PathBuf>,
+    require_certificate_validation: bool,
     server_name_override: Option<String>,
     connect_timeout: Duration,
     call_timeout: Duration,
@@ -38,6 +43,7 @@ impl ClientOptions {
             api_key: None,
             plaintext: true,
             ca_file: None,
+            require_certificate_validation: false,
             server_name_override: None,
             connect_timeout: Duration::from_secs(10),
             call_timeout: Duration::from_secs(30),
@@ -67,6 +73,22 @@ impl ClientOptions {
         self
     }
 
+    /// Require TLS certificate verification even without a pinned CA. Default
+    /// false: the gateway's self-signed certificate is accepted (internal-tool
+    /// posture). Setting a CA file always verifies.
+    ///
+    /// Note for Rust: tonic 0.13's `ClientTlsConfig` exposes no hook for a
+    /// custom rustls verifier, so the Rust client cannot accept an arbitrary
+    /// self-signed certificate the way the other clients do. With the default
+    /// (false) and no pinned CA, [`crate::client::GatewayClient::connect`]
+    /// rejects the TLS connection and asks for a CA file. Either pin a CA via
+    /// [`ClientOptions::with_ca_file`] (the supported lenient path on Rust) or
+    /// set this `true` to verify against the system trust roots.
+    pub fn with_require_certificate_validation(mut self, require: bool) -> Self {
+        self.require_certificate_validation = require;
+        self
+    }
+
     /// Override the SNI/server name used during the TLS handshake. Useful
     /// when the dial-target host name does not match the certificate.
     pub fn with_server_name_override(mut self, server_name_override: impl Into<String>) -> Self {
@@ -95,6 +117,7 @@ impl ClientOptions {
         self
     }
 
+    /// Maximum encoded/decoded gRPC message size in bytes (default 16 MiB).
     pub fn with_max_grpc_message_bytes(mut self, max_grpc_message_bytes: usize) -> Self {
         self.max_grpc_message_bytes = max_grpc_message_bytes;
         self
@@ -120,6 +143,12 @@ impl ClientOptions {
         self.ca_file.as_ref()
     }
 
+    /// Whether TLS certificate verification is required even without a pinned
+    /// CA. See [`ClientOptions::with_require_certificate_validation`].
+    pub fn require_certificate_validation(&self) -> bool {
+        self.require_certificate_validation
+    }
+
     /// Optional SNI / server-name override for TLS handshakes.
     pub fn server_name_override(&self) -> Option<&str> {
         self.server_name_override.as_deref()
@@ -140,11 +169,74 @@ impl ClientOptions {
         self.stream_timeout
     }
 
+    /// Configured maximum encoded/decoded gRPC message size in bytes.
     pub fn max_grpc_message_bytes(&self) -> usize {
         self.max_grpc_message_bytes
     }
 }
 
+/// Build the [`ClientTlsConfig`] for a non-plaintext connection described by
+/// `options`, applying the lenient-default guard that is the **Rust
+/// pin-only exception**.
+///
+/// Returns `Ok(None)` when `options.plaintext()` is `true` (no TLS needed).
+/// Returns `Ok(Some(tls))` when a valid TLS config can be assembled.
+/// Returns `Err(Error::InvalidEndpoint)` when TLS is requested but no pinned
+/// CA was provided and `require_certificate_validation` is `false`.
+///
+/// # Why this guard exists
+///
+/// `tonic` 0.13's `ClientTlsConfig` builds its rustls verifier inside a
+/// crate-private connector and exposes no hook for a custom
+/// `ServerCertVerifier`. The Rust client therefore cannot accept an arbitrary
+/// self-signed certificate the way the other language clients do. Rather than
+/// silently falling back to system-root verification (which always fails
+/// against a self-signed gateway certificate), we reject the configuration
+/// early with an actionable error.
+pub(crate) fn build_tls_config(options: &ClientOptions) -> Result<Option<ClientTlsConfig>, Error> {
+    if options.plaintext() {
+        return Ok(None);
+    }
+
+    let mut tls = ClientTlsConfig::new();
+    if let Some(server_name) = options.server_name_override() {
+        tls = tls.domain_name(server_name.to_owned());
+    }
+    if let Some(ca_file) = options.ca_file() {
+        let certificate = fs::read(ca_file).map_err(|source| Error::InvalidEndpoint {
+            endpoint: options.endpoint().to_owned(),
+            detail: format!("failed to read CA file {}: {source}", ca_file.display()),
+        })?;
+        tls = tls.ca_certificate(Certificate::from_pem(certificate));
+    } else if !options.require_certificate_validation() {
+        // Lenient-default fallback (Rust pin-only exception): tonic
+        // 0.13's `ClientTlsConfig` builds its rustls verifier inside a
+        // crate-private connector and exposes no hook for a custom
+        // `ServerCertVerifier`, so — unlike the other clients — the
+        // Rust client cannot accept an arbitrary self-signed cert. Pin
+        // the gateway's CA instead, or opt into strict verification
+        // against the system trust roots. We reject here rather than
+        // silently verifying against system roots (which would fail a
+        // self-signed gateway with a confusing handshake error).
+        //
+        // Note: a server-name override affects SNI (the hostname sent
+        // in the TLS ClientHello) but does NOT pin trust. Overriding
+        // the server name alone does not bypass certificate validation.
+        return Err(Error::InvalidEndpoint {
+            endpoint: options.endpoint().to_owned(),
+            detail: "TLS requested without a pinned CA. The Rust client cannot accept an \
+                     arbitrary self-signed certificate (tonic 0.13 exposes no custom \
+                     rustls verifier). Pin the gateway certificate with \
+                     ClientOptions::with_ca_file, or call \
+                     ClientOptions::with_require_certificate_validation(true) to verify \
+                     against the system trust roots. Note: a server-name override \
+                     affects SNI but does not pin trust."
+                .to_owned(),
+        });
+    }
+    Ok(Some(tls))
+}
+
 impl Default for ClientOptions {
     fn default() -> Self {
         Self::new("http://127.0.0.1:5000")
@@ -159,6 +251,10 @@ impl fmt::Debug for ClientOptions {
             .field("api_key", &self.api_key.as_ref().map(|_| "<redacted>"))
             .field("plaintext", &self.plaintext)
             .field("ca_file", &self.ca_file)
+            .field(
+                "require_certificate_validation",
+                &self.require_certificate_validation,
+            )
             .field("server_name_override", &self.server_name_override)
             .field("connect_timeout", &self.connect_timeout)
             .field("call_timeout", &self.call_timeout)

clients/rust/src/session.rs

@@ -8,6 +8,8 @@
 //! Bulk commands enforce a 1000-item cap before contacting the worker, in
 //! line with the gateway's documented `MAX_BULK_ITEMS`.
 
+use std::sync::atomic::{AtomicU64, Ordering};
+
 use crate::client::{EventStream, GatewayClient};
 use crate::error::{ensure_protocol_success, Error};
 use crate::generated::mxaccess_gateway::v1::mx_command::Payload;
@@ -26,6 +28,28 @@ use crate::value::MxValue;
 
 const MAX_BULK_ITEMS: usize = 1_000;
 
+/// Process-wide monotonic sequence used by [`next_correlation_id`].
+static CORRELATION_SEQUENCE: AtomicU64 = AtomicU64::new(1);
+
+/// Build a per-call correlation id that embeds the supplied `label`.
+///
+/// The returned token is opaque and guaranteed to be unique within the
+/// current process: every call increments a process-wide atomic counter,
+/// so concurrent CLI smokes and library callers on the same machine produce
+/// distinct ids that gateway logs can tell apart. The token carries no
+/// embedded secret beyond `label`.
+///
+/// The exact textual format (currently `rust-client-{label}-{N}`) is *not*
+/// part of the public contract — callers must not parse it. The crate root
+/// re-exports this helper as
+/// [`zb_mom_ww_mxgateway_client::next_correlation_id`] so out-of-tree
+/// consumers can build correlation ids without referencing the `session`
+/// module path.
+pub fn next_correlation_id(label: &str) -> String {
+    let sequence = CORRELATION_SEQUENCE.fetch_add(1, Ordering::Relaxed);
+    format!("rust-client-{label}-{sequence}")
+}
+
 /// Handle to an opened gateway session.
 ///
 /// `Session` carries the gateway-issued session id and a cloned
@@ -79,7 +103,7 @@ impl Session {
             .client
             .close_session_raw(CloseSessionRequest {
                 session_id: self.id.clone(),
-                client_correlation_id: "rust-client-close-session".to_owned(),
+                client_correlation_id: next_correlation_id("close-session"),
             })
             .await?;
         ensure_protocol_success("close session", reply.protocol_status.as_ref())?;
@@ -102,7 +126,7 @@ impl Session {
             )
             .await?;
 
-        Ok(register_server_handle(&reply))
+        register_server_handle(&reply)
     }
 
     /// Run MXAccess `AddItem` against `server_handle` and return the
@@ -123,7 +147,7 @@ impl Session {
             )
             .await?;
 
-        Ok(add_item_handle(&reply))
+        add_item_handle(&reply)
     }
 
     /// Run MXAccess `AddItem2` (item with a caller-supplied context string)
@@ -149,7 +173,7 @@ impl Session {
             )
             .await?;
 
-        Ok(add_item2_handle(&reply))
+        add_item2_handle(&reply)
     }
 
     /// Run MXAccess `RemoveItem` for the given handle pair.
@@ -229,7 +253,7 @@ impl Session {
             )
             .await?;
 
-        Ok(bulk_results(reply, BulkReplyKind::AddItemBulk))
+        bulk_results(reply, BulkReplyKind::AddItem)
     }
 
     /// Bulk variant of [`Session::advise`].
@@ -253,7 +277,7 @@ impl Session {
             )
             .await?;
 
-        Ok(bulk_results(reply, BulkReplyKind::AdviseItemBulk))
+        bulk_results(reply, BulkReplyKind::AdviseItem)
     }
 
     /// Bulk variant of [`Session::remove_item`].
@@ -277,7 +301,7 @@ impl Session {
             )
             .await?;
 
-        Ok(bulk_results(reply, BulkReplyKind::RemoveItemBulk))
+        bulk_results(reply, BulkReplyKind::RemoveItem)
     }
 
     /// Bulk variant of [`Session::un_advise`].
@@ -301,7 +325,7 @@ impl Session {
             )
             .await?;
 
-        Ok(bulk_results(reply, BulkReplyKind::UnAdviseItemBulk))
+        bulk_results(reply, BulkReplyKind::UnAdviseItem)
     }
 
     /// Bulk `Subscribe` (atomic add-and-advise) for a list of tag addresses.
@@ -325,7 +349,7 @@ impl Session {
             )
             .await?;
 
-        Ok(bulk_results(reply, BulkReplyKind::SubscribeBulk))
+        bulk_results(reply, BulkReplyKind::Subscribe)
     }
 
     /// Bulk `Unsubscribe` (atomic un-advise-and-remove) for a list of
@@ -350,7 +374,7 @@ impl Session {
             )
             .await?;
 
-        Ok(bulk_results(reply, BulkReplyKind::UnsubscribeBulk))
+        bulk_results(reply, BulkReplyKind::Unsubscribe)
     }
 
     /// Bulk `Read` — snapshot the current value for each requested tag.
@@ -366,10 +390,10 @@ impl Session {
     /// # Errors
     ///
     /// Same conditions as [`Session::add_item_bulk`].
-    pub async fn read_bulk(
+    pub async fn read_bulk<S: AsRef<str>>(
         &self,
         server_handle: i32,
-        tag_addresses: Vec<String>,
+        tag_addresses: &[S],
         timeout_ms: u32,
     ) -> Result<Vec<BulkReadResult>, Error> {
         ensure_bulk_size("tag_addresses", tag_addresses.len())?;
@@ -378,16 +402,21 @@ impl Session {
                 MxCommandKind::ReadBulk,
                 Payload::ReadBulk(ReadBulkCommand {
                     server_handle,
-                    tag_addresses,
+                    tag_addresses: tag_addresses
+                        .iter()
+                        .map(|tag| tag.as_ref().to_owned())
+                        .collect(),
                     timeout_ms,
                 }),
             )
             .await?;
 
-        Ok(match reply.payload {
-            Some(mx_command_reply::Payload::ReadBulk(reply)) => reply.results,
-            _ => Vec::new(),
-        })
+        match reply.payload {
+            Some(mx_command_reply::Payload::ReadBulk(reply)) => Ok(reply.results),
+            _ => Err(Error::MalformedReply {
+                detail: "read_bulk reply did not carry a ReadBulk payload".to_owned(),
+            }),
+        }
     }
 
     /// Bulk `Write` (sequential MXAccess Write per entry, on the worker's STA).
@@ -416,7 +445,7 @@ impl Session {
             )
             .await?;
 
-        Ok(bulk_write_results(reply, BulkWriteReplyKind::Write))
+        bulk_write_results(reply, BulkWriteReplyKind::Write)
     }
 
     /// Bulk `Write2` (timestamped) — see [`Session::write_bulk`].
@@ -440,7 +469,7 @@ impl Session {
             )
             .await?;
 
-        Ok(bulk_write_results(reply, BulkWriteReplyKind::Write2))
+        bulk_write_results(reply, BulkWriteReplyKind::Write2)
     }
 
     /// Bulk `WriteSecured` — credential-sensitive values follow the same
@@ -465,7 +494,7 @@ impl Session {
             )
             .await?;
 
-        Ok(bulk_write_results(reply, BulkWriteReplyKind::WriteSecured))
+        bulk_write_results(reply, BulkWriteReplyKind::WriteSecured)
     }
 
     /// Bulk `WriteSecured2` (timestamped) — see [`Session::write_secured_bulk`].
@@ -489,7 +518,7 @@ impl Session {
             )
             .await?;
 
-        Ok(bulk_write_results(reply, BulkWriteReplyKind::WriteSecured2))
+        bulk_write_results(reply, BulkWriteReplyKind::WriteSecured2)
     }
 
     /// Run MXAccess `Write` (single-value, no caller-supplied timestamp).
@@ -608,7 +637,7 @@ impl Session {
     fn command_request(&self, kind: MxCommandKind, payload: Payload) -> MxCommandRequest {
         MxCommandRequest {
             session_id: self.id.clone(),
-            client_correlation_id: format!("rust-client-{}", kind.as_str_name()),
+            client_correlation_id: next_correlation_id(kind.as_str_name()),
             command: Some(MxCommand {
                 kind: kind as i32,
                 payload: Some(payload),
@@ -628,71 +657,80 @@ fn ensure_bulk_size(name: &'static str, len: usize) -> Result<(), Error> {
     }
 }
 
-fn register_server_handle(reply: &MxCommandReply) -> i32 {
+fn register_server_handle(reply: &MxCommandReply) -> Result<i32, Error> {
     match reply.payload.as_ref() {
-        Some(mx_command_reply::Payload::Register(register)) => register.server_handle,
+        Some(mx_command_reply::Payload::Register(register)) => Ok(register.server_handle),
         _ => reply
             .return_value
             .as_ref()
             .and_then(int32_reply_value)
-            .unwrap_or_default(),
+            .ok_or_else(|| Error::MalformedReply {
+                detail: "register reply lacked a server_handle payload or int32 return_value"
+                    .to_owned(),
+            }),
     }
 }
 
-fn add_item_handle(reply: &MxCommandReply) -> i32 {
+fn add_item_handle(reply: &MxCommandReply) -> Result<i32, Error> {
     match reply.payload.as_ref() {
-        Some(mx_command_reply::Payload::AddItem(add_item)) => add_item.item_handle,
+        Some(mx_command_reply::Payload::AddItem(add_item)) => Ok(add_item.item_handle),
         _ => reply
             .return_value
             .as_ref()
             .and_then(int32_reply_value)
-            .unwrap_or_default(),
+            .ok_or_else(|| Error::MalformedReply {
+                detail: "add_item reply lacked an item_handle payload or int32 return_value"
+                    .to_owned(),
+            }),
     }
 }
 
-fn add_item2_handle(reply: &MxCommandReply) -> i32 {
+fn add_item2_handle(reply: &MxCommandReply) -> Result<i32, Error> {
     match reply.payload.as_ref() {
-        Some(mx_command_reply::Payload::AddItem2(add_item)) => add_item.item_handle,
+        Some(mx_command_reply::Payload::AddItem2(add_item)) => Ok(add_item.item_handle),
         _ => reply
             .return_value
             .as_ref()
             .and_then(int32_reply_value)
-            .unwrap_or_default(),
+            .ok_or_else(|| Error::MalformedReply {
+                detail: "add_item2 reply lacked an item_handle payload or int32 return_value"
+                    .to_owned(),
+            }),
     }
 }
 
 enum BulkReplyKind {
-    AddItemBulk,
-    AdviseItemBulk,
-    RemoveItemBulk,
-    UnAdviseItemBulk,
-    SubscribeBulk,
-    UnsubscribeBulk,
+    AddItem,
+    AdviseItem,
+    RemoveItem,
+    UnAdviseItem,
+    Subscribe,
+    Unsubscribe,
 }
 
-fn bulk_results(reply: MxCommandReply, kind: BulkReplyKind) -> Vec<SubscribeResult> {
+fn bulk_results(reply: MxCommandReply, kind: BulkReplyKind) -> Result<Vec<SubscribeResult>, Error> {
     match (reply.payload, kind) {
-        (Some(mx_command_reply::Payload::AddItemBulk(reply)), BulkReplyKind::AddItemBulk) => {
-            reply.results
+        (Some(mx_command_reply::Payload::AddItemBulk(reply)), BulkReplyKind::AddItem) => {
+            Ok(reply.results)
         }
-        (Some(mx_command_reply::Payload::AdviseItemBulk(reply)), BulkReplyKind::AdviseItemBulk) => {
-            reply.results
+        (Some(mx_command_reply::Payload::AdviseItemBulk(reply)), BulkReplyKind::AdviseItem) => {
+            Ok(reply.results)
         }
-        (Some(mx_command_reply::Payload::RemoveItemBulk(reply)), BulkReplyKind::RemoveItemBulk) => {
-            reply.results
+        (Some(mx_command_reply::Payload::RemoveItemBulk(reply)), BulkReplyKind::RemoveItem) => {
+            Ok(reply.results)
         }
-        (
-            Some(mx_command_reply::Payload::UnAdviseItemBulk(reply)),
-            BulkReplyKind::UnAdviseItemBulk,
-        ) => reply.results,
-        (Some(mx_command_reply::Payload::SubscribeBulk(reply)), BulkReplyKind::SubscribeBulk) => {
-            reply.results
+        (Some(mx_command_reply::Payload::UnAdviseItemBulk(reply)), BulkReplyKind::UnAdviseItem) => {
+            Ok(reply.results)
         }
-        (
-            Some(mx_command_reply::Payload::UnsubscribeBulk(reply)),
-            BulkReplyKind::UnsubscribeBulk,
-        ) => reply.results,
-        _ => Vec::new(),
+        (Some(mx_command_reply::Payload::SubscribeBulk(reply)), BulkReplyKind::Subscribe) => {
+            Ok(reply.results)
+        }
+        (Some(mx_command_reply::Payload::UnsubscribeBulk(reply)), BulkReplyKind::Unsubscribe) => {
+            Ok(reply.results)
+        }
+        _ => Err(Error::MalformedReply {
+            detail: "bulk subscribe reply did not carry the expected payload arm".to_owned(),
+        }),
     }
 }
 
@@ -703,23 +741,28 @@ enum BulkWriteReplyKind {
     WriteSecured2,
 }
 
-fn bulk_write_results(reply: MxCommandReply, kind: BulkWriteReplyKind) -> Vec<BulkWriteResult> {
+fn bulk_write_results(
+    reply: MxCommandReply,
+    kind: BulkWriteReplyKind,
+) -> Result<Vec<BulkWriteResult>, Error> {
     match (reply.payload, kind) {
         (Some(mx_command_reply::Payload::WriteBulk(reply)), BulkWriteReplyKind::Write) => {
-            reply.results
+            Ok(reply.results)
         }
         (Some(mx_command_reply::Payload::Write2Bulk(reply)), BulkWriteReplyKind::Write2) => {
-            reply.results
+            Ok(reply.results)
         }
         (
             Some(mx_command_reply::Payload::WriteSecuredBulk(reply)),
             BulkWriteReplyKind::WriteSecured,
-        ) => reply.results,
+        ) => Ok(reply.results),
         (
             Some(mx_command_reply::Payload::WriteSecured2Bulk(reply)),
             BulkWriteReplyKind::WriteSecured2,
-        ) => reply.results,
-        _ => Vec::new(),
+        ) => Ok(reply.results),
+        _ => Err(Error::MalformedReply {
+            detail: "bulk write reply did not carry the expected payload arm".to_owned(),
+        }),
     }
 }
 

clients/rust/tests/client_behavior.rs

@@ -20,16 +20,19 @@ use zb_mom_ww_mxgateway_client::generated::mxaccess_gateway::v1::mx_access_gatew
 use zb_mom_ww_mxgateway_client::generated::mxaccess_gateway::v1::mx_command_reply;
 use zb_mom_ww_mxgateway_client::generated::mxaccess_gateway::v1::mx_value::Kind;
 use zb_mom_ww_mxgateway_client::generated::mxaccess_gateway::v1::{
-    AcknowledgeAlarmReply, AcknowledgeAlarmRequest, ActiveAlarmSnapshot, AddItemReply,
-    AlarmFeedMessage, BulkSubscribeReply, CloseSessionReply, CloseSessionRequest, MxCommandKind,
-    MxCommandReply, MxDataType, MxEvent, MxEventFamily, MxStatusCategory, MxStatusProxy,
-    MxStatusSource, MxValue, OpenSessionReply, OpenSessionRequest, ProtocolStatus,
-    ProtocolStatusCode, QueryActiveAlarmsRequest, SessionState, StreamAlarmsRequest,
-    StreamEventsRequest, SubscribeResult,
+    alarm_feed_message, AcknowledgeAlarmReply, AcknowledgeAlarmRequest, ActiveAlarmSnapshot,
+    AddItem2Reply, AddItemReply, AlarmConditionState, AlarmFeedMessage, AlarmTransitionKind,
+    BulkReadReply, BulkReadResult, BulkSubscribeReply, BulkWriteReply, BulkWriteResult,
+    CloseSessionReply, CloseSessionRequest, MxCommandKind, MxCommandReply, MxDataType, MxEvent,
+    MxEventFamily, MxStatusCategory, MxStatusProxy, MxStatusSource, MxValue,
+    OnAlarmTransitionEvent, OpenSessionReply, OpenSessionRequest, ProtocolStatus,
+    ProtocolStatusCode, QueryActiveAlarmsRequest, RegisterReply, SessionState, StreamAlarmsRequest,
+    StreamEventsRequest, SubscribeResult, Write2BulkEntry, WriteBulkEntry, WriteSecured2BulkEntry,
+    WriteSecuredBulkEntry,
 };
 use zb_mom_ww_mxgateway_client::{
-    ApiKey, ClientOptions, CommandError, Error, GatewayClient, MxStatus, MxValue as ClientMxValue,
-    MxValueProjection,
+    next_correlation_id, ApiKey, ClientOptions, CommandError, Error, GatewayClient, MxStatus,
+    MxValue as ClientMxValue, MxValueProjection,
 };
 
 #[tokio::test]
@@ -272,11 +275,414 @@ fn command_error_display_keeps_raw_reply_accessible() {
     assert!(error.to_string().contains("MxaccessFailure"));
 }
 
+// ---- Client.Rust-022 / 024 regression coverage ---------------------------
+
+#[tokio::test]
+async fn register_returns_malformed_reply_when_ok_reply_has_no_payload() {
+    let state = Arc::new(FakeState::default());
+    *state.invoke_override.lock().await = Some(InvokeOverride::OkWithoutPayload);
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let error = session.register("client").await.unwrap_err();
+
+    assert!(
+        matches!(error, Error::MalformedReply { .. }),
+        "expected MalformedReply, got {error:?}"
+    );
+}
+
+#[tokio::test]
+async fn add_item_returns_malformed_reply_when_ok_reply_has_no_payload() {
+    let state = Arc::new(FakeState::default());
+    *state.invoke_override.lock().await = Some(InvokeOverride::OkWithoutPayload);
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let error = session.add_item(12, "Plant.Area.Tag").await.unwrap_err();
+
+    assert!(
+        matches!(error, Error::MalformedReply { .. }),
+        "expected MalformedReply, got {error:?}"
+    );
+}
+
+#[tokio::test]
+async fn add_item2_returns_malformed_reply_when_ok_reply_has_no_payload() {
+    let state = Arc::new(FakeState::default());
+    *state.invoke_override.lock().await = Some(InvokeOverride::OkWithoutPayload);
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let error = session
+        .add_item2(12, "Plant.Area.Tag", "ctx")
+        .await
+        .unwrap_err();
+
+    assert!(
+        matches!(error, Error::MalformedReply { .. }),
+        "expected MalformedReply, got {error:?}"
+    );
+}
+
+#[tokio::test]
+async fn subscribe_bulk_returns_malformed_reply_on_mismatched_payload_arm() {
+    let state = Arc::new(FakeState::default());
+    *state.invoke_override.lock().await = Some(InvokeOverride::OkWithMismatchedPayload);
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let error = session
+        .subscribe_bulk(12, vec!["Area001.Pump001.Speed".to_owned()])
+        .await
+        .unwrap_err();
+
+    assert!(
+        matches!(error, Error::MalformedReply { .. }),
+        "expected MalformedReply, got {error:?}"
+    );
+}
+
+#[tokio::test]
+async fn read_bulk_returns_malformed_reply_on_mismatched_payload_arm() {
+    let state = Arc::new(FakeState::default());
+    *state.invoke_override.lock().await = Some(InvokeOverride::OkWithMismatchedPayload);
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let error = session
+        .read_bulk(12, &["Area001.Pump001.Speed".to_owned()], 1000)
+        .await
+        .unwrap_err();
+
+    assert!(
+        matches!(error, Error::MalformedReply { .. }),
+        "expected MalformedReply, got {error:?}"
+    );
+}
+
+#[tokio::test]
+async fn write_bulk_returns_malformed_reply_on_mismatched_payload_arm() {
+    let state = Arc::new(FakeState::default());
+    *state.invoke_override.lock().await = Some(InvokeOverride::OkWithMismatchedPayload);
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let error = session
+        .write_bulk(
+            12,
+            vec![WriteBulkEntry {
+                item_handle: 34,
+                value: Some(ClientMxValue::int32(1).into_proto()),
+                user_id: 0,
+            }],
+        )
+        .await
+        .unwrap_err();
+
+    assert!(
+        matches!(error, Error::MalformedReply { .. }),
+        "expected MalformedReply, got {error:?}"
+    );
+}
+
+#[tokio::test]
+async fn unary_invoke_maps_status_unavailable_to_error_unavailable() {
+    let state = Arc::new(FakeState::default());
+    *state.invoke_override.lock().await =
+        Some(InvokeOverride::Unavailable("gateway restarting".to_owned()));
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let error = session.add_item(12, "Plant.Area.Tag").await.unwrap_err();
+
+    assert!(
+        matches!(error, Error::Unavailable { .. }),
+        "expected Unavailable, got {error:?}"
+    );
+}
+
+#[tokio::test]
+async fn read_bulk_round_trips_through_the_fake_gateway() {
+    let state = Arc::new(FakeState::default());
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let results = session
+        .read_bulk(12, &["Area001.Pump001.Speed".to_owned()], 1000)
+        .await
+        .unwrap();
+
+    assert_eq!(results.len(), 1);
+    assert!(results[0].was_successful);
+    assert!(results[0].was_cached);
+}
+
+#[tokio::test]
+async fn write_bulk_round_trips_through_the_fake_gateway() {
+    let state = Arc::new(FakeState::default());
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let results = session
+        .write_bulk(
+            12,
+            vec![WriteBulkEntry {
+                item_handle: 34,
+                value: Some(ClientMxValue::int32(1).into_proto()),
+                user_id: 0,
+            }],
+        )
+        .await
+        .unwrap();
+
+    assert_eq!(results.len(), 1);
+    assert!(results[0].was_successful);
+    let last_command = state.last_command_kind.lock().await;
+    assert_eq!(*last_command, Some(MxCommandKind::WriteBulk as i32));
+}
+
+#[tokio::test]
+async fn write2_bulk_round_trips_through_the_fake_gateway() {
+    let state = Arc::new(FakeState::default());
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let results = session
+        .write2_bulk(
+            12,
+            vec![Write2BulkEntry {
+                item_handle: 34,
+                value: Some(ClientMxValue::int32(1).into_proto()),
+                timestamp_value: Some(ClientMxValue::string("2026-05-24T00:00:00Z").into_proto()),
+                user_id: 0,
+            }],
+        )
+        .await
+        .unwrap();
+
+    assert_eq!(results.len(), 1);
+    assert!(results[0].was_successful);
+    let last_command = state.last_command_kind.lock().await;
+    assert_eq!(*last_command, Some(MxCommandKind::Write2Bulk as i32));
+}
+
+#[tokio::test]
+async fn write_secured_bulk_round_trips_through_the_fake_gateway() {
+    let state = Arc::new(FakeState::default());
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let results = session
+        .write_secured_bulk(
+            12,
+            vec![WriteSecuredBulkEntry {
+                item_handle: 34,
+                value: Some(ClientMxValue::int32(1).into_proto()),
+                current_user_id: 0,
+                verifier_user_id: 0,
+            }],
+        )
+        .await
+        .unwrap();
+
+    assert_eq!(results.len(), 1);
+    assert!(results[0].was_successful);
+    let last_command = state.last_command_kind.lock().await;
+    assert_eq!(*last_command, Some(MxCommandKind::WriteSecuredBulk as i32));
+}
+
+#[tokio::test]
+async fn write_secured2_bulk_round_trips_through_the_fake_gateway() {
+    let state = Arc::new(FakeState::default());
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+    let session = client.session("session-fixture");
+
+    let results = session
+        .write_secured2_bulk(
+            12,
+            vec![WriteSecured2BulkEntry {
+                item_handle: 34,
+                value: Some(ClientMxValue::int32(1).into_proto()),
+                timestamp_value: Some(ClientMxValue::string("2026-05-24T00:00:00Z").into_proto()),
+                current_user_id: 0,
+                verifier_user_id: 0,
+            }],
+        )
+        .await
+        .unwrap();
+
+    assert_eq!(results.len(), 1);
+    assert!(results[0].was_successful);
+    let last_command = state.last_command_kind.lock().await;
+    assert_eq!(*last_command, Some(MxCommandKind::WriteSecured2Bulk as i32));
+}
+
+#[tokio::test]
+async fn stream_alarms_emits_snapshot_then_complete_then_transition_in_order() {
+    let state = Arc::new(FakeState::default());
+    *state.stream_alarms_script.lock().await = Some(vec![
+        AlarmFeedMessage {
+            payload: Some(alarm_feed_message::Payload::ActiveAlarm(
+                ActiveAlarmSnapshot {
+                    alarm_full_reference: "Tank01.Level.HiHi".to_owned(),
+                    current_state: AlarmConditionState::Active as i32,
+                    ..ActiveAlarmSnapshot::default()
+                },
+            )),
+        },
+        AlarmFeedMessage {
+            payload: Some(alarm_feed_message::Payload::SnapshotComplete(true)),
+        },
+        AlarmFeedMessage {
+            payload: Some(alarm_feed_message::Payload::Transition(
+                OnAlarmTransitionEvent {
+                    alarm_full_reference: "Tank01.Level.HiHi".to_owned(),
+                    transition_kind: AlarmTransitionKind::Raise as i32,
+                    ..OnAlarmTransitionEvent::default()
+                },
+            )),
+        },
+    ]);
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+
+    let mut stream = client
+        .stream_alarms(StreamAlarmsRequest {
+            client_correlation_id: next_correlation_id("test-stream-alarms"),
+            alarm_filter_prefix: String::new(),
+        })
+        .await
+        .unwrap();
+
+    let first = stream.next().await.unwrap().unwrap();
+    let second = stream.next().await.unwrap().unwrap();
+    let third = stream.next().await.unwrap().unwrap();
+
+    assert!(matches!(
+        first.payload,
+        Some(alarm_feed_message::Payload::ActiveAlarm(_))
+    ));
+    assert!(matches!(
+        second.payload,
+        Some(alarm_feed_message::Payload::SnapshotComplete(true))
+    ));
+    assert!(matches!(
+        third.payload,
+        Some(alarm_feed_message::Payload::Transition(_))
+    ));
+}
+
+#[tokio::test]
+async fn cli_subcommands_propagate_unique_correlation_ids_from_next_correlation_id() {
+    // The CLI's `stream-alarms` and `acknowledge-alarm` paths used to
+    // hard-code their correlation ids (Client.Rust-023). Verify the
+    // resolution end-to-end through `next_correlation_id`: every call
+    // observed at the fake gateway has a unique id that embeds the
+    // `cli-...` label, so concurrent CLI smokes can tell collisions apart.
+    let state = Arc::new(FakeState::default());
+    let endpoint = spawn_fake_gateway(state.clone()).await;
+    let client = GatewayClient::connect(ClientOptions::new(endpoint))
+        .await
+        .unwrap();
+
+    let first_corr = next_correlation_id("cli-stream-alarms");
+    let _ = client
+        .stream_alarms(StreamAlarmsRequest {
+            client_correlation_id: first_corr.clone(),
+            alarm_filter_prefix: String::new(),
+        })
+        .await
+        .unwrap();
+    assert_eq!(
+        *state.last_correlation_id.lock().await,
+        Some(first_corr.clone())
+    );
+
+    let second_corr = next_correlation_id("cli-stream-alarms");
+    assert_ne!(first_corr, second_corr);
+    assert!(second_corr.contains("cli-stream-alarms"));
+
+    let third_corr = next_correlation_id("cli-acknowledge-alarm");
+    let _ = client
+        .acknowledge_alarm(AcknowledgeAlarmRequest {
+            client_correlation_id: third_corr.clone(),
+            alarm_full_reference: "Tank01.Level.HiHi".to_owned(),
+            comment: String::new(),
+            operator_user: String::new(),
+        })
+        .await
+        .unwrap();
+    assert_eq!(*state.last_correlation_id.lock().await, Some(third_corr));
+}
+
 #[derive(Default)]
 struct FakeState {
     authorization: Mutex<Option<String>>,
     last_command_kind: Mutex<Option<i32>>,
+    last_correlation_id: Mutex<Option<String>>,
     stream_dropped: Arc<AtomicBool>,
+    /// Optional per-test override that pins the fake's `Invoke` handler to
+    /// a specific reply shape (or `Err(Status)`). The default of `None`
+    /// keeps the existing happy-path dispatcher.
+    invoke_override: Mutex<Option<InvokeOverride>>,
+    /// Optional per-test override that pins the fake's `StreamAlarms`
+    /// handler to emit a synthetic ConditionRefresh -> snapshot_complete
+    /// -> transition sequence.
+    stream_alarms_script: Mutex<Option<Vec<AlarmFeedMessage>>>,
+}
+
+/// Per-test override for the fake's `Invoke` handler.
+#[allow(dead_code)]
+enum InvokeOverride {
+    /// Reply with `protocol_status = Ok` and no `payload` set.
+    OkWithoutPayload,
+    /// Reply with `protocol_status = Ok` and a deliberately wrong payload
+    /// arm — e.g. an `AddItemReply` body when the caller invoked a bulk
+    /// command. The variant carries the kind to recognise in tests but the
+    /// reply itself is the mismatched-payload shape.
+    OkWithMismatchedPayload,
+    /// Fail the unary call with `Status::unavailable(...)` so the client's
+    /// `Code::Unavailable` -> `Error::Unavailable` mapping is exercised.
+    Unavailable(String),
 }
 
 #[derive(Clone)]
@@ -331,6 +737,35 @@ impl MxAccessGateway for FakeGateway {
             .map(|command| command.kind)
             .unwrap_or_default();
         *self.state.last_command_kind.lock().await = Some(kind);
+        *self.state.last_correlation_id.lock().await = Some(request.client_correlation_id.clone());
+
+        // Honour any per-test override before falling through to the
+        // happy-path dispatcher.
+        if let Some(override_) = self.state.invoke_override.lock().await.take() {
+            return match override_ {
+                InvokeOverride::OkWithoutPayload => Ok(Response::new(MxCommandReply {
+                    session_id: request.session_id,
+                    correlation_id: "fake-correlation".to_owned(),
+                    kind,
+                    protocol_status: Some(ok_status("command ok")),
+                    payload: None,
+                    ..MxCommandReply::default()
+                })),
+                InvokeOverride::OkWithMismatchedPayload => Ok(Response::new(MxCommandReply {
+                    session_id: request.session_id,
+                    correlation_id: "fake-correlation".to_owned(),
+                    kind,
+                    protocol_status: Some(ok_status("command ok")),
+                    // Deliberately the wrong payload arm — `AddItemReply`
+                    // for whatever command was actually invoked.
+                    payload: Some(mx_command_reply::Payload::AddItem(AddItemReply {
+                        item_handle: 99,
+                    })),
+                    ..MxCommandReply::default()
+                })),
+                InvokeOverride::Unavailable(message) => Err(Status::unavailable(message)),
+            };
+        }
 
         if kind == MxCommandKind::Write as i32 {
             return Ok(Response::new(mxaccess_failure_reply()));
@@ -357,6 +792,92 @@ impl MxAccessGateway for FakeGateway {
             }));
         }
 
+        if kind == MxCommandKind::Register as i32 {
+            return Ok(Response::new(MxCommandReply {
+                session_id: request.session_id,
+                correlation_id: "fake-correlation".to_owned(),
+                kind,
+                protocol_status: Some(ok_status("command ok")),
+                payload: Some(mx_command_reply::Payload::Register(RegisterReply {
+                    server_handle: 12,
+                })),
+                ..MxCommandReply::default()
+            }));
+        }
+
+        if kind == MxCommandKind::AddItem2 as i32 {
+            return Ok(Response::new(MxCommandReply {
+                session_id: request.session_id,
+                correlation_id: "fake-correlation".to_owned(),
+                kind,
+                protocol_status: Some(ok_status("command ok")),
+                payload: Some(mx_command_reply::Payload::AddItem2(AddItem2Reply {
+                    item_handle: 56,
+                })),
+                ..MxCommandReply::default()
+            }));
+        }
+
+        if kind == MxCommandKind::ReadBulk as i32 {
+            return Ok(Response::new(MxCommandReply {
+                session_id: request.session_id,
+                correlation_id: "fake-correlation".to_owned(),
+                kind,
+                protocol_status: Some(ok_status("command ok")),
+                payload: Some(mx_command_reply::Payload::ReadBulk(BulkReadReply {
+                    results: vec![BulkReadResult {
+                        server_handle: 12,
+                        tag_address: "Area001.Pump001.Speed".to_owned(),
+                        item_handle: 34,
+                        was_successful: true,
+                        was_cached: true,
+                        ..BulkReadResult::default()
+                    }],
+                })),
+                ..MxCommandReply::default()
+            }));
+        }
+
+        if kind == MxCommandKind::WriteBulk as i32 {
+            return Ok(Response::new(write_bulk_reply_for(
+                request.session_id,
+                kind,
+                mx_command_reply::Payload::WriteBulk(BulkWriteReply {
+                    results: vec![bulk_write_result_ok(12, 34)],
+                }),
+            )));
+        }
+
+        if kind == MxCommandKind::Write2Bulk as i32 {
+            return Ok(Response::new(write_bulk_reply_for(
+                request.session_id,
+                kind,
+                mx_command_reply::Payload::Write2Bulk(BulkWriteReply {
+                    results: vec![bulk_write_result_ok(12, 34)],
+                }),
+            )));
+        }
+
+        if kind == MxCommandKind::WriteSecuredBulk as i32 {
+            return Ok(Response::new(write_bulk_reply_for(
+                request.session_id,
+                kind,
+                mx_command_reply::Payload::WriteSecuredBulk(BulkWriteReply {
+                    results: vec![bulk_write_result_ok(12, 34)],
+                }),
+            )));
+        }
+
+        if kind == MxCommandKind::WriteSecured2Bulk as i32 {
+            return Ok(Response::new(write_bulk_reply_for(
+                request.session_id,
+                kind,
+                mx_command_reply::Payload::WriteSecured2Bulk(BulkWriteReply {
+                    results: vec![bulk_write_result_ok(12, 34)],
+                }),
+            )));
+        }
+
         Ok(Response::new(MxCommandReply {
             session_id: request.session_id,
             correlation_id: "fake-correlation".to_owned(),
@@ -387,8 +908,10 @@ impl MxAccessGateway for FakeGateway {
 
     async fn acknowledge_alarm(
         &self,
-        _request: Request<AcknowledgeAlarmRequest>,
+        request: Request<AcknowledgeAlarmRequest>,
     ) -> Result<Response<AcknowledgeAlarmReply>, Status> {
+        *self.state.last_correlation_id.lock().await =
+            Some(request.into_inner().client_correlation_id);
         Ok(Response::new(AcknowledgeAlarmReply {
             correlation_id: "corr-1".to_owned(),
             protocol_status: Some(ok_status("ack ok")),
@@ -407,9 +930,18 @@ impl MxAccessGateway for FakeGateway {
 
     async fn stream_alarms(
         &self,
-        _request: Request<StreamAlarmsRequest>,
+        request: Request<StreamAlarmsRequest>,
     ) -> Result<Response<Self::StreamAlarmsStream>, Status> {
-        let (_sender, receiver) = mpsc::channel::<Result<AlarmFeedMessage, Status>>(1);
+        *self.state.last_correlation_id.lock().await =
+            Some(request.into_inner().client_correlation_id);
+        let script = self.state.stream_alarms_script.lock().await.take();
+        let (sender, receiver) =
+            mpsc::channel::<Result<AlarmFeedMessage, Status>>(script.as_ref().map_or(1, Vec::len));
+        if let Some(messages) = script {
+            for message in messages {
+                sender.send(Ok(message)).await.unwrap();
+            }
+        }
         let stream = ReceiverStream::new(receiver);
         Ok(Response::new(Box::pin(stream)))
     }
@@ -469,6 +1001,32 @@ async fn spawn_fake_gateway(state: Arc<FakeState>) -> String {
     format!("http://{address}")
 }
 
+fn write_bulk_reply_for(
+    session_id: String,
+    kind: i32,
+    payload: mx_command_reply::Payload,
+) -> MxCommandReply {
+    MxCommandReply {
+        session_id,
+        correlation_id: "fake-correlation".to_owned(),
+        kind,
+        protocol_status: Some(ok_status("command ok")),
+        payload: Some(payload),
+        ..MxCommandReply::default()
+    }
+}
+
+fn bulk_write_result_ok(server_handle: i32, item_handle: i32) -> BulkWriteResult {
+    BulkWriteResult {
+        server_handle,
+        item_handle,
+        was_successful: true,
+        hresult: Some(0),
+        statuses: Vec::new(),
+        error_message: String::new(),
+    }
+}
+
 fn ok_status(message: &str) -> ProtocolStatus {
     ProtocolStatus {
         code: ProtocolStatusCode::Ok as i32,