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

@@ -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,

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()
     {
@@ -519,6 +532,8 @@ public sealed class MxGatewayClientCliTests
     /// 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")]
@@ -573,6 +588,7 @@ public sealed class MxGatewayClientCliTests
     /// 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()
     {
@@ -623,6 +639,7 @@ public sealed class MxGatewayClientCliTests
     /// 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()
     {
@@ -716,6 +733,8 @@ public sealed class MxGatewayClientCliTests
     /// 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")]
@@ -878,7 +897,8 @@ public sealed class MxGatewayClientCliTests
         /// <summary>Optional per-call handler that overrides queue-based behaviour.</summary>
         public Func<MxCommandRequest, CancellationToken, Task<MxCommandReply>>? InvokeHandler { get; init; }
 
-        /// <inheritdoc />
+        /// <summary>Releases resources held by the fake CLI client.</summary>
+        /// <returns>A completed value task.</returns>
         public ValueTask DisposeAsync()
         {
             return ValueTask.CompletedTask;
@@ -988,6 +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/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/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_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/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:
@@ -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/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_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

@@ -17,3 +17,6 @@
 # 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

@@ -189,6 +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

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

@@ -426,6 +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)]
@@ -453,6 +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
     }

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/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>>,
@@ -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/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 {
@@ -121,6 +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()
@@ -147,6 +175,68 @@ impl ClientOptions {
     }
 }
 
+/// 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")
@@ -161,6 +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/tests/tls.rs

@@ -0,0 +1,137 @@
+//! TLS posture coverage for the Rust client.
+//!
+//! tonic 0.13.1's `ClientTlsConfig` exposes no hook for a custom rustls
+//! `ServerCertVerifier` (the verifier is built internally inside the
+//! crate-private `TlsConnector`), so the Rust client cannot implement the
+//! "accept any server certificate" lenient default the other clients use.
+//! Rust is therefore the documented **pin-only exception**: TLS without a
+//! pinned CA is rejected up front with a clear, actionable error, and
+//! supplying a CA file is the supported path. These tests pin that contract.
+
+use std::time::Duration;
+
+use zb_mom_ww_mxgateway_client::{ClientOptions, Error, GalaxyClient, GatewayClient};
+
+/// Drive `connect` to its error without requiring `GatewayClient: Debug`
+/// (the success arm is dropped explicitly so `unwrap_err` is unnecessary).
+async fn connect_err(options: ClientOptions) -> Error {
+    match GatewayClient::connect(options).await {
+        Ok(_client) => panic!("connect unexpectedly succeeded against a dead TLS address"),
+        Err(error) => error,
+    }
+}
+
+#[tokio::test]
+async fn tls_without_ca_is_rejected_with_actionable_error_by_default() {
+    let options = ClientOptions::new("https://127.0.0.1:1")
+        .with_plaintext(false)
+        .with_connect_timeout(Duration::from_millis(200));
+
+    let error = connect_err(options).await;
+
+    let Error::InvalidEndpoint { detail, .. } = error else {
+        panic!("expected InvalidEndpoint, got {error:?}");
+    };
+    // The message must point the caller at the supported remedy (pin a CA)
+    // and name the opt-in escape hatch.
+    assert!(
+        detail.contains("ca_file") || detail.contains("CA"),
+        "error should instruct the user to pass a CA file: {detail}"
+    );
+    assert!(
+        detail.contains("require_certificate_validation"),
+        "error should mention the require_certificate_validation opt-in: {detail}"
+    );
+}
+
+#[tokio::test]
+async fn tls_with_require_certificate_validation_does_not_short_circuit() {
+    // With strict verification opted in, the no-CA guard must not fire; the
+    // connect attempt instead proceeds to the transport (and fails to reach
+    // the dead address) rather than returning the "CA required" guard error.
+    let options = ClientOptions::new("https://127.0.0.1:1")
+        .with_plaintext(false)
+        .with_require_certificate_validation(true)
+        .with_connect_timeout(Duration::from_millis(200));
+
+    let error = connect_err(options).await;
+
+    assert!(
+        !matches!(&error, Error::InvalidEndpoint { detail, .. }
+            if detail.contains("require_certificate_validation")),
+        "strict verification must bypass the no-CA guard, got {error:?}"
+    );
+}
+
+#[tokio::test]
+async fn tls_with_ca_file_is_permitted_and_proceeds_past_the_guard() {
+    // Pinning a CA is the supported TLS path: the no-CA guard must not fire.
+    // We hand it a readable PEM file; construction proceeds past the guard
+    // and only fails later at the transport (dead address / handshake).
+    let ca_path = std::env::temp_dir().join("mxgw-rust-tls-ca-fixture.pem");
+    std::fs::write(&ca_path, SELF_SIGNED_CA_PEM).unwrap();
+
+    let options = ClientOptions::new("https://127.0.0.1:1")
+        .with_plaintext(false)
+        .with_ca_file(&ca_path)
+        .with_connect_timeout(Duration::from_millis(200));
+
+    let error = connect_err(options).await;
+
+    let _ = std::fs::remove_file(&ca_path);
+
+    assert!(
+        !matches!(&error, Error::InvalidEndpoint { detail, .. }
+            if detail.contains("require_certificate_validation")),
+        "pinning a CA must bypass the no-CA guard, got {error:?}"
+    );
+}
+
+/// Drive `GalaxyClient::connect` to its error (mirrors `connect_err` above).
+async fn galaxy_connect_err(options: ClientOptions) -> Error {
+    match GalaxyClient::connect(options).await {
+        Ok(_client) => {
+            panic!("GalaxyClient::connect unexpectedly succeeded against a dead TLS address")
+        }
+        Err(error) => error,
+    }
+}
+
+#[tokio::test]
+async fn galaxy_tls_without_ca_is_rejected_with_actionable_error_by_default() {
+    // GalaxyClient::connect must apply the same TLS guard as GatewayClient —
+    // TLS without a pinned CA (and without require_certificate_validation)
+    // returns a clear, actionable InvalidEndpoint error.
+    let options = ClientOptions::new("https://127.0.0.1:1")
+        .with_plaintext(false)
+        .with_connect_timeout(Duration::from_millis(200));
+
+    let error = galaxy_connect_err(options).await;
+
+    let Error::InvalidEndpoint { detail, .. } = error else {
+        panic!("expected InvalidEndpoint, got {error:?}");
+    };
+    assert!(
+        detail.contains("ca_file") || detail.contains("CA"),
+        "error should instruct the user to pass a CA file: {detail}"
+    );
+    assert!(
+        detail.contains("require_certificate_validation"),
+        "error should mention the require_certificate_validation opt-in: {detail}"
+    );
+}
+
+/// A throwaway self-signed CA certificate (PEM). Only needs to parse as a
+/// PEM trust root so the CA-pinning path is exercised past the guard.
+const SELF_SIGNED_CA_PEM: &str = "-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+";

code-reviews/Client.Java/findings.md

@@ -7,7 +7,7 @@
 | Review date | 2026-05-24 |
 | Commit reviewed | `42b0037` |
 | Status | Re-reviewed |
-| Open findings | 5 |
+| Open findings | 0 |
 
 ## Checklist coverage
 
@@ -551,7 +551,7 @@ Client.Java-001..031 are unchanged.
 | Severity | High |
 | Category | Documentation & comments |
 | Location | `clients/java/README.md:182-183` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** Commit `8738735` ("clients: document StreamAlarms + AcknowledgeAlarm in each README") added two new gradle invocations to the CLI Usage block:
 
@@ -569,6 +569,8 @@ A user copying either invocation from the README hits a picocli parse error imme
 
 **Recommendation:** Drop the `--session-id <id>` token from both documented invocations, and change `--alarm-reference` to `--reference` in the `acknowledge-alarm` line. Optionally also add `--filter-prefix` to the `stream-alarms` example so readers see the scoping option, and align README option names with the actual CLI by either renaming the CLI option `--reference` → `--alarm-reference` (matches the proto `alarm_full_reference` field semantically) or leaving as is and only fixing the README. Add a small `MxGatewayCliTests` parse-only assertion for both subcommands that exercises every option flag to prevent the same drift the next time the CLI surface or README is touched.
 
+**Resolution:** 2026-05-24 — Confirmed root cause against `clients/java/zb-mom-ww-mxgateway-cli/src/main/java/com/zb/mom/ww/mxgateway/cli/MxGatewayCli.java:1174-1182,1248-1258`: `StreamAlarmsCommand` exposes only `--filter-prefix` / `--limit` and `AcknowledgeAlarmCommand` exposes `--reference` / `--comment` / `--operator` — neither has a `--session-id` option and `acknowledge-alarm` has no `--alarm-reference` option, so both documented invocations failed picocli parse at the first unknown option. Fixed `clients/java/README.md:182-183` by dropping the `--session-id <id>` token from both lines, replacing it with `--filter-prefix Galaxy` on the `stream-alarms` example so readers see the actual scoping flag, and changing `--alarm-reference` to `--reference` on the `acknowledge-alarm` example. Added `MxGatewayCli.commandLine(...)` to package-private visibility (was `private`) so the test can drive the production picocli `CommandLine` directly without executing the command body. Regression tests in `MxGatewayCliTests`: `readmeDocumentedStreamAlarmsExampleParsesCleanly` and `readmeDocumentedAcknowledgeAlarmExampleParsesCleanly` pin the exact token list documented in the README and assert `commandLine.parseArgs(...)` returns without throwing a `picocli.CommandLine.ParameterException`. TDD red phase: before the README fix the previously-documented tokens (`--session-id <id>` + `--alarm-reference ...`) would have thrown `Unknown option: '--session-id'` / `Unknown option: '--alarm-reference'` at parse time; the new tests pass against the corrected README and would fail the next time someone drifts the documented surface from the actual CLI options.
+
 ### Client.Java-033
 
 | Field | Value |
@@ -576,7 +578,7 @@ A user copying either invocation from the README hits a picocli parse error imme
 | Severity | Medium |
 | Category | Correctness & logic bugs |
 | Location | `clients/java/zb-mom-ww-mxgateway-cli/src/main/java/com/zb/mom/ww/mxgateway/cli/MxGatewayCli.java:1078-1098` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `StreamAlarmsCommand.call()` allocates a bounded `ArrayBlockingQueue<Object>(1024)` and the gRPC observer publishes each `AlarmFeedMessage` via `queue.offer(value)`:
 
@@ -594,6 +596,8 @@ The library-side `MxEventStream` (Client.Java-002 resolution) and `DeployEventSt
 
 **Recommendation:** Either (a) wrap the gRPC observer in the existing `MxEventStream`-style adaptor that calls `subscription.cancel()` and queues an exception on `queue.offer` returning `false`, then surface that exception from the drain loop — mirroring `MxEventStream.observer().onNext`'s overflow branch; or (b) reuse the library-side fail-fast plumbing by promoting `MxEventStream` (or extracting its terminal-state base) into a public `MxAlarmFeedStream` and have `MxGatewayClient.streamAlarms` return that instead of a bare subscription handle. Option (b) lines up with Client.Java-036 (deduplicate the subscription class family). Add a CLI regression test that overflows the bounded queue and asserts a non-zero exit / overflow exception, mirroring `MxGatewayMediumFindingsTests.eventStreamOverflowExceptionSurvivesASubsequentClose`.
 
+**Resolution:** 2026-05-24 — Confirmed root cause at `MxGatewayCli.java` `StreamAlarmsCommand.call()`: the observer's `onNext` did `queue.offer(value)` and ignored the boolean return, so a 1024-element queue would silently drop messages past capacity. The same silent-drop affected the `onCompleted` branch (which `offer`s `ALARM_FEED_END`) once the queue was full, deadlocking the consumer since the drain loop never sees END. Took option (a) — minimal change that matches `MxEventStream`'s overflow branch. The fix: detect a failed `offer` inside `onNext`, call `subscription.cancel()` (via an `AtomicReference<MxGatewayAlarmFeedSubscription>` published immediately after `client.streamAlarms` returns), `queue.clear()`, then `queue.offer(IllegalStateException("stream-alarms queue overflowed (capacity 1024); consumer too slow"))` followed by `queue.offer(ALARM_FEED_END)`. The existing drain-loop `Throwable`-branch then surfaces the overflow as a thrown `IllegalStateException` from `call()`, which picocli reports as a non-zero CLI exit. Option (b) (promoting `MxEventStream` to a public alarm-feed stream) was considered and rejected for this change — it would change the public SDK surface; Client.Java-036's refactor handles deduplication at the subscription layer instead. Regression test: `MxGatewayCliTests.streamAlarmsCommandFailsFastOnQueueOverflow` — drives an `OverflowingFakeClient` whose `streamAlarms` synchronously pushes 2000 messages to the observer (exceeding the 1024 buffer), then asserts `run.exitCode() != 0`. TDD red phase confirmed deterministically: before the fix the test deadlocked (the buggy `offer` silently dropped both the overflowing alarms AND the `ALARM_FEED_END` sentinel that arrived after the queue filled, so the drain loop's `queue.take()` blocked forever); the background gradle run had to be killed with `TaskStop`. After the fix the same test exits in <1 second with the overflow exception propagating through picocli.
+
 ### Client.Java-034
 
 | Field | Value |
@@ -601,7 +605,7 @@ The library-side `MxEventStream` (Client.Java-002 resolution) and `DeployEventSt
 | Severity | Medium |
 | Category | Correctness & logic bugs |
 | Location | `clients/java/zb-mom-ww-mxgateway-cli/src/main/java/com/zb/mom/ww/mxgateway/cli/MxGatewayCli.java:182-198` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `BatchCommand.call()` reads one CLI invocation per stdin line and tokenises with:
 
@@ -622,6 +626,8 @@ The current `MxGatewayCliTests` test set (`batchCommandExecutesVersionAndEmitsEo
 
 **Recommendation:** Replace `line.trim().split("\\s+")` with a real shell-style tokeniser that honours single and double quotes and backslash escapes — `picocli.CommandLine.ArgumentParser` doesn't ship one, but Apache Commons Exec's `CommandLine.translateCommandline(String)`, JDK 21's `java.util.spi.ToolProvider` argument parsing, or a small hand-written state machine all work. Cross-check the .NET / Go / Rust / Python `batch` implementations in the same change so all five clients use the same tokenisation; document the contract in the protocol comment in `MxGatewayCli.java` and in `scripts/run-client-e2e-tests.ps1`. Add a CLI test that feeds `acknowledge-alarm --comment "with spaces"` through `batch` and asserts the `--comment` value reaches the gateway as `"with spaces"`.
 
+**Resolution:** 2026-05-24 — Confirmed root cause: `BatchCommand.call()` at the per-line loop used `line.trim().split("\\s+")` which has no quote handling. Replaced with a new package-private `MxGatewayCli.tokenizeBatchLine(String)` static helper — a hand-rolled POSIX-style shell tokenizer (no new dependency added) that honours: (a) double-quoted runs `"..."` with `\\`, `\"`, and `\n` escapes inside; (b) single-quoted runs `'...'` taken literally with no escapes (POSIX rule); (c) backslash escapes for any single character outside quotes (so `needs\ verification` is one token); (d) whitespace runs outside quotes separate tokens; (e) explicit `IllegalArgumentException` on unterminated quote or trailing backslash so the batch loop surfaces it as a JSON error instead of emitting wrong args. The `BatchCommand` per-line tokenisation now calls `tokenizeBatchLine(line)` and treats an empty-array result as a blank line (skip). Behaviour for whitespace-only input is unchanged. The cross-client `batch` audit (.NET / Go / Rust / Python) is out of scope for this Java-focused finding and tracked separately. Regression tests in `MxGatewayCliTests`: (a) `batchCommandTokenisesDoubleQuotedArgumentWithEmbeddedSpaces` — `--comment "needs verification"` round-trips intact; (b) `batchCommandTokenisesSingleQuotedArgumentWithEmbeddedSpaces` — single-quoted variant; (c) `batchCommandTokenisesBackslashEscapedSpaceOutsideQuotes` — `needs\ verification` outside quotes; (d) `batchCommandPreservesEmptyQuotedArgument` — `""` parses to an empty-string argument; (e) `batchCommandSupportsBackslashEscapedQuoteInsideDoubleQuotes` — `\"inner\"` survives the inner quotes. TDD red phase confirmed: all five tests failed against the original `split("\\s+")` implementation; after the fix all five pass.
+
 ### Client.Java-035
 
 | Field | Value |
@@ -629,7 +635,7 @@ The current `MxGatewayCliTests` test set (`batchCommandExecutesVersionAndEmitsEo
 | Severity | Low |
 | Category | Testing coverage |
 | Location | `clients/java/zb-mom-ww-mxgateway-client/src/test/java/com/zb/mom/ww/mxgateway/client/MxGatewayClientSessionTests.java` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** Commit `8a0c59d` added `MxGatewayClient.streamAlarms(StreamAlarmsRequest, StreamObserver<AlarmFeedMessage>)` and a new public `MxGatewayAlarmFeedSubscription` class. No library-side test exercises either: a grep for `streamAlarms` across `zb-mom-ww-mxgateway-client/src/test/...` returns zero matches. The CLI tests (`MxGatewayCliTests.streamAlarmsCommand*`) exercise the path end-to-end, but they route through a `FakeClient.streamAlarms` override that bypasses the production `subscription.wrap(observer)` glue and the `withStreamDeadline(rawAsyncStub()).streamAlarms(...)` call. A regression to either — forgetting `.wrap(observer)`, dropping the deadline interceptor, misnaming the request — would compile and pass the CLI tests but break against a real gateway.
 
@@ -637,6 +643,8 @@ This is the same coverage gap pattern as Client.Java-030 (no fixture test for `Q
 
 **Recommendation:** Add `streamAlarmsForwardsRequestAndStreamsAlarmFeedMessages` to `MxGatewayClientSessionTests` (in-process gRPC via the existing `InProcessGateway` + `TestGatewayService` fixture): override `TestGatewayService.streamAlarms` to capture the inbound `StreamAlarmsRequest` and emit one `active_alarm` snapshot, one `snapshot_complete`, and one `transition`, then complete. Call `MxGatewayClient.streamAlarms`, drain the observer via a `CountDownLatch`, and assert (a) the server observed the `alarm_filter_prefix`, (b) all three messages arrived in order with the expected payload-case, and (c) `MxGatewayAlarmFeedSubscription.cancel()` aborts the call (latch via `ServerCallStreamObserver.setOnCancelHandler`, mirroring the Client.Java-015 cancellation regression). Optionally also cover the cancel-before-beforeStart race that `MxGatewayAlarmFeedSubscription.wrap` handles, mirroring `mxEventStreamCloseBeforeBeforeStartCancelsStream`.
 
+**Resolution:** 2026-05-24 — Confirmed the coverage gap: a grep across `zb-mom-ww-mxgateway-client/src/test/...` for `streamAlarms` returned zero matches; the CLI-only test routed through `FakeClient.streamAlarms` which bypassed both the production `subscription.wrap(observer)` and the `withStreamDeadline(rawAsyncStub()).streamAlarms(...)` gRPC call. Added `streamAlarmsForwardsRequestAndStreamsAlarmFeedMessages` to `MxGatewayClientSessionTests` in the same shape as `queryActiveAlarmsForwardsRequestAndStreamsSnapshots` (Client.Java-030 resolved this way). The test overrides `TestGatewayService.streamAlarms` to capture the inbound `StreamAlarmsRequest`, register a `serverCancelled` latch via `(ServerCallStreamObserver<AlarmFeedMessage>) responseObserver).setOnCancelHandler(...)`, then emit three messages: an `active_alarm` snapshot, a `snapshot_complete` sentinel, and a `transition`. It deliberately does NOT call `onCompleted()` so the call remains open for the cancellation assertion. The test then calls `MxGatewayClient.streamAlarms` against the in-process gateway, drains the wrapped observer via a `threeReceived` `CountDownLatch`, and asserts (a) the server observed `alarm_filter_prefix=Tank01`, (b) all three messages arrived in order with the expected payload-case (`ACTIVE_ALARM`, `SNAPSHOT_COMPLETE`, `TRANSITION`) and payload values (`Tank01.Level.HiHi`, transition kind `ACKNOWLEDGE`), and (c) `subscription.cancel()` causes the server's on-cancel handler to fire within 5 s (proves cancellation propagates through the production `subscription.wrap(observer)` glue, not just the CLI fake). TDD red phase: temporarily replaced the production `MxGatewayClient.streamAlarms` body with `withStreamDeadline(rawAsyncStub()).streamAlarms(request, observer);` (dropping the `subscription.wrap(observer)` indirection); the test failed at the `serverCancelled.await` assertion because cancellation was no longer wired to the underlying gRPC call. Restoring the production glue turned the build green.
+
 ### Client.Java-036
 
 | Field | Value |
@@ -644,7 +652,7 @@ This is the same coverage gap pattern as Client.Java-030 (no fixture test for `Q
 | Severity | Low |
 | Category | Code organization & conventions |
 | Location | `clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayAlarmFeedSubscription.java`, `MxGatewayEventSubscription.java`, `MxGatewayActiveAlarmsSubscription.java`, `DeployEventSubscription.java` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `MxGatewayAlarmFeedSubscription` is a structural near-copy of `MxGatewayEventSubscription` — same `AtomicReference<ClientCallStreamObserver<…>>` + `AtomicBoolean cancelled` field shape, the same `wrap(observer)` returning a `ClientResponseObserver` that stores `requestStream` in `beforeStart`, the same close-before-beforeStart race handling that Client.Java-014 originally fixed for `MxEventStream`, and the same `cancel()`+`close()` idempotency contract. The four subscription classes (`MxGatewayEventSubscription`, `MxGatewayActiveAlarmsSubscription`, `MxGatewayAlarmFeedSubscription`, `DeployEventSubscription`) are now ~60-line near-clones differing only in the request/response generic parameters and the `cancel` message string.
 
@@ -652,4 +660,6 @@ This is the same maintenance-hazard pattern Client.Java-009 / Client.Java-016 id
 
 **Recommendation:** Extract a package-private abstract base, e.g. `MxGatewayStreamSubscription<TRequest>`, holding the `AtomicReference` / `AtomicBoolean` pair, the `cancel()` / `close()` implementation, and a `ClientResponseObserver` factory parameterised by the cancel-message string and the response observer. Have all four subscription classes extend it. Behaviour-only refactor — no public API change, existing tests cover the contract.
 
+**Resolution:** 2026-05-24 — Extracted a package-private abstract base `MxGatewayStreamSubscription<TRequest, TResponse> implements AutoCloseable` (new file `clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayStreamSubscription.java`). It holds the shared `AtomicReference<ClientCallStreamObserver<TRequest>>` and `AtomicBoolean cancelled` pair, the `wrap(StreamObserver<TResponse>)` factory that returns a `ClientResponseObserver` with the Client.Java-014 close-before-beforeStart fix baked in, the `cancel()` / `close()` implementation, and an immutable `cancelMessage` injected by the subclass constructor. The four prior 60-line near-clones (`MxGatewayEventSubscription`, `MxGatewayAlarmFeedSubscription`, `MxGatewayActiveAlarmsSubscription`, `DeployEventSubscription`) collapse to ~10-line subclasses that only declare their `<Request, Response>` type parameters and supply the cancel-message string to `super(...)`. Public API surface is preserved: each subclass remains a `public final class` with a public no-arg constructor (the constructor was implicit on the original classes; I made it explicit `public` on the subclasses so the existing CLI `FakeClient.streamAlarms` in a different package can still `new MxGatewayAlarmFeedSubscription()`). The `wrap(...)` method is `final` and package-private on the base — same accessibility the four subclasses had before — so production callers in `MxGatewayClient`/`GalaxyRepositoryClient` see no change. New test file `MxGatewayStreamSubscriptionContractTests` exercises the lifecycle/cancellation contract identically across all four subclasses (16 tests, four per scenario): (a) cancel-before-beforeStart eagerly cancels the stream once it attaches with the subclass-specific message, (b) cancel-after-beforeStart forwards directly to the stream, (c) `close()` delegates to `cancel()`, (d) the wrapped observer forwards `onNext`/`onError`/`onCompleted` verbatim, and a compile-time `typeBoundsCheck` helper that asserts each subclass still binds its `<Req, Resp>` parameters to the right proto types. TDD red phase confirmed: temporarily breaking one subclass's `super(...)` message to `"BROKEN MESSAGE"` made the contract test for that subclass fail with `expected: <client cancelled alarm feed> but was: <BROKEN MESSAGE>`; restoring the correct value turned all 16 contract tests green. Future fixes to the shared lifecycle now live in one place — the next Client.Java-014/021-style race fix cannot drift across the four classes.
+
 

code-reviews/IntegrationTests/findings.md

@@ -7,7 +7,7 @@
 | Review date | 2026-05-24 |
 | Commit reviewed | `42b0037` |
 | Status | Re-reviewed |
-| Open findings | 1 |
+| Open findings | 0 |
 
 ## Checklist coverage
 
@@ -494,7 +494,7 @@ The Write parity test (IntegrationTests-012's resolution) added exactly this ass
 | Severity | Low |
 | Category | Correctness & logic bugs |
 | Location | `src/ZB.MOM.WW.MxGateway.IntegrationTests/IntegrationTestEnvironmentTests.cs:57-84` (`ResolveRepositoryRoot_NoMarkers_ThrowsInvalidOperationExceptionNamingStartAndMarkers`) |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** The new regression test for IntegrationTests-022 builds an "isolated" start directory under `Path.GetTempPath()` (e.g. `C:\Users\<user>\AppData\Local\Temp\<random>\nested` on Windows) and calls `ResolveRepositoryRoot(isolatedStart)`, asserting an `InvalidOperationException` is thrown. The walker walks every parent — `<random>`, `Temp`, `Local`, `AppData`, `<user>`, `Users`, `C:\` — and stops only when it either finds a repository root marker or runs out of parents. The test silently assumes none of those ancestor directories satisfies `IsRepositoryRoot` (a `src/` subdirectory next to `.git` / `*.sln` / `*.slnx`). The assumption is environment-dependent:
 
@@ -504,3 +504,5 @@ The Write parity test (IntegrationTests-012's resolution) added exactly this ass
 The current dev box layout (`C:\Users\dohertj2\Desktop\mxaccessgw`) is safe because Temp is at `C:\Users\dohertj2\AppData\Local\Temp` and the walker exits at `C:\` without ever encountering `src/`. The fragility is invisible on this machine and only surfaces if the test ever runs in CI / on a contributor box with a less hermetic file-system layout.
 
 **Recommendation:** Isolate the walker from any ambient ancestor by either (a) constructing an `isolatedRoot` directly under a drive root and pointing the walker at a chain entirely under it (e.g. create `<isolatedRoot>\level1\level2\level3` and start the walk at `level3`, then assert the throw — the walker stops at the drive root regardless of what is on it), (b) refactoring `ResolveRepositoryRoot` to accept an injectable `stopBoundary` parameter for tests and pass `isolatedRoot` as the boundary, or (c) replacing the `Assert.Throws` shape with an explicit upward-walk check that the test owns. Option (a) is the smallest change: prepend a sentinel — e.g. create a dummy `<isolatedRoot>\sentinel-no-markers` and assert nothing about Temp ancestors — and pass the test only when the walker reaches that sentinel without finding a marker. The current shape is acceptable on the documented dev box but should not be the sole regression coverage for IntegrationTests-022.
+
+**Resolution:** Resolved 2026-05-24 — Took option (b) (inject a stop-boundary) because option (a) does not actually solve the leak: a sentinel chain under `Path.GetTempPath()` still leaves the walker free to ascend past it into Temp / AppData / Users / C:\, so any ambient ancestor with `src/` + `.git`/`.sln`/`.slnx` still wins. Added an optional `stopBoundary` parameter to `IntegrationTestEnvironment.ResolveRepositoryRoot(string startDirectory, string? stopBoundary = null)`. When supplied, the walker checks the boundary for markers and then stops, refusing to ascend past it; production callers (the `MXGATEWAY_LIVE_MXACCESS_WORKER_EXE` resolution path) continue to pass `null` so the walk to drive-root behavior is unchanged. Updated both existing tests (`ResolveRepositoryRoot_AcceptsGitWorktreeFile` and `ResolveRepositoryRoot_NoMarkers_ThrowsInvalidOperationExceptionNamingStartAndMarkers`) to pass their owned temp directory as the boundary, sealing the walker inside a chain the test fully controls. Added a new regression test `ResolveRepositoryRoot_StopBoundary_IsolatesWalkerFromAmbientAncestorMarkers` that deliberately constructs an outer marker-bearing ancestor (`outerRoot/src` + `outerRoot/.git`), an inner boundary, and an isolated start beneath the boundary; first asserts that without the boundary the walker leaks up to `outerRoot` (the precise IntegrationTests-025 failure mode), then asserts that *with* the boundary the same call throws — proving the boundary is the load-bearing isolation. TDD red/green confirmed: the new regression test fails against the pre-fix walker (`Assert.Throws() Failure: No exception was thrown`) and passes once the boundary handling is restored. Re-ran the full `IntegrationTestEnvironmentTests` slice with `TMP` / `TEMP` redirected under a deliberately constructed `<temp>\fake-repo-ancestor` directory carrying `src/` and a `.git` file — the original flake repro from the finding — and confirmed all 5 tests pass (the same redirection produced `Assert.Throws() Failure` on the pre-fix code). Build: 0 warnings / 0 errors.

code-reviews/README.md

@@ -12,13 +12,13 @@ Each module's `findings.md` is the source of truth; this file is generated from
 |---|---|---|---|---|---|---|
 | [Client.Dotnet](Client.Dotnet/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 21 |
 | [Client.Go](Client.Go/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 27 |
-| [Client.Java](Client.Java/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 5 | 36 |
+| [Client.Java](Client.Java/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 36 |
 | [Client.Python](Client.Python/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 26 |
 | [Client.Rust](Client.Rust/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 29 |
 | [Contracts](Contracts/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 17 |
-| [IntegrationTests](IntegrationTests/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 1 | 25 |
+| [IntegrationTests](IntegrationTests/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 25 |
 | [Server](Server/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 50 |
-| [Tests](Tests/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 5 | 31 |
+| [Tests](Tests/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 31 |
 | [Worker](Worker/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 25 |
 | [Worker.Tests](Worker.Tests/findings.md) | Claude Code | 2026-05-24 | `42b0037` | Re-reviewed | 0 | 30 |
 
@@ -26,19 +26,7 @@ Each module's `findings.md` is the source of truth; this file is generated from
 
 Findings with status `Open` or `In Progress`, ordered by severity.
 
-| ID | Severity | Category | Location | Description |
-|---|---|---|---|---|
-| Client.Java-032 | High | Documentation & comments | `clients/java/README.md:182-183` | Commit `8738735` ("clients: document StreamAlarms + AcknowledgeAlarm in each README") added two new gradle invocations to the CLI Usage block: ``` gradle :zb-mom-ww-mxgateway-cli:run --args="stream-alarms --endpoint localhost:5000 --api-ke… |
-| Client.Java-033 | Medium | Correctness & logic bugs | `clients/java/zb-mom-ww-mxgateway-cli/src/main/java/com/zb/mom/ww/mxgateway/cli/MxGatewayCli.java:1078-1098` | `StreamAlarmsCommand.call()` allocates a bounded `ArrayBlockingQueue<Object>(1024)` and the gRPC observer publishes each `AlarmFeedMessage` via `queue.offer(value)`: ``` BlockingQueue<Object> queue = new ArrayBlockingQueue<>(1024); … @Over… |
-| Client.Java-034 | Medium | Correctness & logic bugs | `clients/java/zb-mom-ww-mxgateway-cli/src/main/java/com/zb/mom/ww/mxgateway/cli/MxGatewayCli.java:182-198` | `BatchCommand.call()` reads one CLI invocation per stdin line and tokenises with: ``` String[] args = line.trim().split("\\s+"); … int exitCode = cmd.execute(args); ``` `split("\\s+")` does no shell-quoting parsing — it just splits on whit… |
-| Tests-027 | Medium | Concurrency & thread safety | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Grpc/MxAccessGatewayServiceTests.cs:199-240`, `src/ZB.MOM.WW.MxGateway.Server/Metrics/GatewayMetrics.cs:8,73,246-251` | The review brief explicitly flagged `MxAccessGatewayServiceTests.StreamEvents_WhenEventIsWritten_RecordsSendDuration` as a known flake that "passed solo on rerun". The root cause is the `MeterListener` subscribes by `instrument.Meter.Name… |
-| Client.Java-035 | Low | Testing coverage | `clients/java/zb-mom-ww-mxgateway-client/src/test/java/com/zb/mom/ww/mxgateway/client/MxGatewayClientSessionTests.java` | Commit `8a0c59d` added `MxGatewayClient.streamAlarms(StreamAlarmsRequest, StreamObserver<AlarmFeedMessage>)` and a new public `MxGatewayAlarmFeedSubscription` class. No library-side test exercises either: a grep for `streamAlarms` across `… |
-| Client.Java-036 | Low | Code organization & conventions | `clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayAlarmFeedSubscription.java`, `MxGatewayEventSubscription.java`, `MxGatewayActiveAlarmsSubscription.java`, `DeployEventSubscription.java` | `MxGatewayAlarmFeedSubscription` is a structural near-copy of `MxGatewayEventSubscription` — same `AtomicReference<ClientCallStreamObserver<…>>` + `AtomicBoolean cancelled` field shape, the same `wrap(observer)` returning a `ClientResponse… |
-| IntegrationTests-025 | Low | Correctness & logic bugs | `src/ZB.MOM.WW.MxGateway.IntegrationTests/IntegrationTestEnvironmentTests.cs:57-84` (`ResolveRepositoryRoot_NoMarkers_ThrowsInvalidOperationExceptionNamingStartAndMarkers`) | The new regression test for IntegrationTests-022 builds an "isolated" start directory under `Path.GetTempPath()` (e.g. `C:\Users\<user>\AppData\Local\Temp\<random>\nested` on Windows) and calls `ResolveRepositoryRoot(isolatedStart)`, asser… |
-| Tests-028 | Low | Testing coverage | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Sessions/SessionManagerTests.cs:466-496,802-807`, `src/ZB.MOM.WW.MxGateway.Server/Sessions/SessionManager.cs:216-253` | The new `KillWorkerAsync_KillsWorkerAndRemovesSession` (line 466) and `KillWorkerAsync_WhenSessionMissing_ThrowsSessionNotFound` (line 486) pin the new kill-path entry, but they do not pin the `reason` argument propagating through the chai… |
-| Tests-029 | Low | Error handling & resilience | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardSessionAdminServiceTests.cs:61-106,139-222`, `src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardSessionAdminService.cs:77-125` | The new `DashboardSessionAdminServiceTests` covers the happy path and the viewer-denial path for both `CloseSessionAsync` and `KillWorkerAsync`, plus `CloseSessionAsync_WhenSessionMissing_ReportsFriendlyError` for the close-side `SessionNo… |
-| Tests-030 | Low | Testing coverage | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardApiKeyManagementServiceTests.cs:115-163`, `src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardApiKeyManagementService.cs:146-177` | The three new `DeleteAsync_*` fixtures cover unauthorised user, success path with audit, and store-refuses-with-friendly-error. They do not exercise two production behaviours: (1) `DeleteAsync_WhenStoreRefuses_ReportsFriendlyError` (line 1… |
-| Tests-031 | Low | Concurrency & thread safety | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardSnapshotPublisherTests.cs:22-61` | `ExecuteAsync_WhenSnapshotServiceThrowsOnce_ReconnectsAfterDelay` records `startedAt = DateTimeOffset.UtcNow` *before* calling `publisher.StartAsync(...)`, then asserts `secondSubscribeAt - startedAt >= reconnectDelay - 10ms` (line 59). Th… |
+_No pending findings._
 
 ## Closed findings
 
@@ -49,6 +37,7 @@ Findings with status `Resolved`, `Won't Fix`, or `Deferred`.
 | Server-001 | Critical | Resolved | Security | `src/MxGateway.Server/GatewayApplication.cs:147-149`, `src/MxGateway.Server/Dashboard/DashboardEndpointRouteBuilderExtensions.cs:55-58`, `src/MxGateway.Server/Dashboard/Components/Routes.razor:1-15` |
 | Client.Go-001 | High | Resolved | Correctness & logic bugs | `clients/go/mxgateway/errors.go:88-93`, `clients/go/mxgateway/errors.go:117-128` |
 | Client.Java-013 | High | Resolved | Testing coverage | `clients/java/mxgateway-cli/src/test/java/com/dohertylan/mxgateway/cli/MxGatewayCliTests.java:212-304`, `clients/java/mxgateway-cli/src/main/java/com/dohertylan/mxgateway/cli/MxGatewayCli.java:1214-1244` |
+| Client.Java-032 | High | Resolved | Documentation & comments | `clients/java/README.md:182-183` |
 | Client.Python-018 | High | Resolved | Code organization & conventions | `clients/python/pyproject.toml:11` |
 | Client.Python-022 | High | Resolved | Documentation & comments | `clients/python/README.md:201-202`, `clients/python/src/zb_mom_ww_mxgateway_cli/commands.py:389-420` |
 | Client.Rust-001 | High | Resolved | mxaccessgw conventions | `clients/rust/src/options.rs:98,143` |
@@ -86,6 +75,8 @@ Findings with status `Resolved`, `Won't Fix`, or `Deferred`.
 | Client.Java-021 | Medium | Resolved | Concurrency & thread safety | `clients/java/mxgateway-client/src/main/java/com/dohertylan/mxgateway/client/DeployEventStream.java:96-135` |
 | Client.Java-027 | Medium | Resolved | Documentation & comments | `clients/java/README.md:36,107-175,185,205,220`, `clients/java/JavaClientDesign.md:195-211` |
 | Client.Java-028 | Medium | Resolved | Documentation & comments | `clients/java/JavaClientDesign.md:23-27` |
+| Client.Java-033 | Medium | Resolved | Correctness & logic bugs | `clients/java/zb-mom-ww-mxgateway-cli/src/main/java/com/zb/mom/ww/mxgateway/cli/MxGatewayCli.java:1078-1098` |
+| Client.Java-034 | Medium | Resolved | Correctness & logic bugs | `clients/java/zb-mom-ww-mxgateway-cli/src/main/java/com/zb/mom/ww/mxgateway/cli/MxGatewayCli.java:182-198` |
 | Client.Python-003 | Medium | Resolved | Error handling & resilience | `clients/python/src/mxgateway/client.py:125-137,155-173` |
 | Client.Python-005 | Medium | Resolved | Performance & resource management | `clients/python/src/mxgateway/galaxy.py:117-140` |
 | Client.Python-009 | Medium | Resolved | Testing coverage | `clients/python/tests/` |
@@ -130,6 +121,7 @@ Findings with status `Resolved`, `Won't Fix`, or `Deferred`.
 | Tests-016 | Medium | Resolved | Testing coverage | `src/MxGateway.Tests/Galaxy/GalaxyHierarchyCacheTests.cs:29-41,115-124` |
 | Tests-020 | Medium | Resolved | Testing coverage | `src/MxGateway.Tests/Gateway/Grpc/MxAccessGatewayServiceConstraintTests.cs:275-347`, `src/MxGateway.Server/Grpc/MxAccessGatewayService.cs:803-829` |
 | Tests-026 | Medium | Resolved | Testing coverage | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Grpc/EventStreamServiceTests.cs`, `src/ZB.MOM.WW.MxGateway.Server/Grpc/EventStreamService.cs:123-126` |
+| Tests-027 | Medium | Resolved | Concurrency & thread safety | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Grpc/MxAccessGatewayServiceTests.cs:199-240`, `src/ZB.MOM.WW.MxGateway.Server/Metrics/GatewayMetrics.cs:8,73,246-251` |
 | Worker-004 | Medium | Resolved | Correctness & logic bugs | `src/MxGateway.Worker/Ipc/WorkerPipeSession.cs:565-588` |
 | Worker-005 | Medium | Resolved | Error handling & resilience | `src/MxGateway.Worker/MxAccess/MxAccessStaSession.cs:205-258` (production alarm poll loop) |
 | Worker-006 | Medium | Resolved | Correctness & logic bugs | `src/MxGateway.Worker/Ipc/WorkerPipeSession.cs:117-124`, `src/MxGateway.Worker/MxAccess/MxAccessStaSession.cs:386-491` |
@@ -205,6 +197,8 @@ Findings with status `Resolved`, `Won't Fix`, or `Deferred`.
 | Client.Java-029 | Low | Resolved | Documentation & comments | `clients/java/README.md:208-209` |
 | Client.Java-030 | Low | Resolved | Testing coverage | `clients/java/zb-mom-ww-mxgateway-client/src/test/java/com/zb/mom/ww/mxgateway/client/` |
 | Client.Java-031 | Low | Resolved | mxaccessgw conventions | `clients/java/README.md:13,17,26` |
+| Client.Java-035 | Low | Resolved | Testing coverage | `clients/java/zb-mom-ww-mxgateway-client/src/test/java/com/zb/mom/ww/mxgateway/client/MxGatewayClientSessionTests.java` |
+| Client.Java-036 | Low | Resolved | Code organization & conventions | `clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayAlarmFeedSubscription.java`, `MxGatewayEventSubscription.java`, `MxGatewayActiveAlarmsSubscription.java`, `DeployEventSubscription.java` |
 | Client.Python-001 | Low | Resolved | Documentation & comments | `clients/python/pyproject.toml:8,25`, `clients/python/src/mxgateway_cli/commands.py:25` |
 | Client.Python-002 | Low | Resolved | Code organization & conventions | `clients/python/src/mxgateway/__init__.py:27` |
 | Client.Python-004 | Low | Resolved | Correctness & logic bugs | `clients/python/src/mxgateway_cli/commands.py:386,402-404` |
@@ -268,6 +262,7 @@ Findings with status `Resolved`, `Won't Fix`, or `Deferred`.
 | IntegrationTests-022 | Low | Resolved | Code organization & conventions | `src/ZB.MOM.WW.MxGateway.IntegrationTests/IntegrationTestEnvironment.cs:103-138` (`ResolveRepositoryRoot` / `IsRepositoryRoot`) |
 | IntegrationTests-023 | Low | Resolved | Testing coverage | `src/ZB.MOM.WW.MxGateway.IntegrationTests/DashboardLdapLiveTests.cs:14-29` |
 | IntegrationTests-024 | Low | Resolved | Code organization & conventions | `src/ZB.MOM.WW.MxGateway.IntegrationTests/WorkerLiveMxAccessSmokeTests.cs` (`NullDashboardEventBroadcaster` private class at end of file) |
+| IntegrationTests-025 | Low | Resolved | Correctness & logic bugs | `src/ZB.MOM.WW.MxGateway.IntegrationTests/IntegrationTestEnvironmentTests.cs:57-84` (`ResolveRepositoryRoot_NoMarkers_ThrowsInvalidOperationExceptionNamingStartAndMarkers`) |
 | Server-007 | Low | Resolved | Performance & resource management | `src/MxGateway.Server/Galaxy/GalaxyHierarchyProjector.cs:55-70` |
 | Server-008 | Low | Resolved | Performance & resource management | `src/MxGateway.Server/Grpc/GalaxyRepositoryGrpcService.cs:111-134,160-189` |
 | Server-009 | Low | Resolved | Error handling & resilience | `src/MxGateway.Server/Security/Authentication/AuthSqliteConnectionFactory.cs:15-32` |
@@ -318,6 +313,10 @@ Findings with status `Resolved`, `Won't Fix`, or `Deferred`.
 | Tests-023 | Low | Resolved | Correctness & logic bugs | `src/MxGateway.Tests/Gateway/Sessions/SessionWorkerClientFactoryFakeWorkerTests.cs:334-374` |
 | Tests-024 | Low | Resolved | Testing coverage | `src/MxGateway.Server/Grpc/MxAccessGatewayService.cs:713-730,784-801,859-876`, `src/MxGateway.Tests/Gateway/Grpc/MxAccessGatewayServiceConstraintTests.cs` |
 | Tests-025 | Low | Resolved | Code organization & conventions | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Grpc/EventStreamServiceTests.cs:285-289`, `src/ZB.MOM.WW.MxGateway.Tests/Gateway/GatewayEndToEndFakeWorkerSmokeTests.cs:417-421` |
+| Tests-028 | Low | Resolved | Testing coverage | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Sessions/SessionManagerTests.cs:466-496,802-807`, `src/ZB.MOM.WW.MxGateway.Server/Sessions/SessionManager.cs:216-253` |
+| Tests-029 | Low | Resolved | Error handling & resilience | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardSessionAdminServiceTests.cs:61-106,139-222`, `src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardSessionAdminService.cs:77-125` |
+| Tests-030 | Low | Resolved | Testing coverage | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardApiKeyManagementServiceTests.cs:115-163`, `src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardApiKeyManagementService.cs:146-177` |
+| Tests-031 | Low | Resolved | Concurrency & thread safety | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardSnapshotPublisherTests.cs:22-61` |
 | Worker-009 | Low | Resolved | Performance & resource management | `src/MxGateway.Worker/Ipc/WorkerFrameReader.cs:31,49`, `src/MxGateway.Worker/Ipc/WorkerFrameWriter.cs:57-58` |
 | Worker-010 | Low | Resolved | Correctness & logic bugs | `src/MxGateway.Worker/Conversion/VariantConverter.cs:204-226` |
 | Worker-011 | Low | Resolved | Correctness & logic bugs | `src/MxGateway.Worker/Ipc/WorkerPipeClient.cs:169-171` |

code-reviews/Tests/findings.md

@@ -7,7 +7,7 @@
 | Review date | 2026-05-24 |
 | Commit reviewed | `42b0037` |
 | Status | Re-reviewed |
-| Open findings | 5 |
+| Open findings | 0 |
 
 ## Checklist coverage
 
@@ -488,12 +488,14 @@ The cancellation tests for `WorkerClient` in `WorkerClientTests` *do* exercise t
 | Severity | Medium |
 | Category | Concurrency & thread safety |
 | Location | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Grpc/MxAccessGatewayServiceTests.cs:199-240`, `src/ZB.MOM.WW.MxGateway.Server/Metrics/GatewayMetrics.cs:8,73,246-251` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** The review brief explicitly flagged `MxAccessGatewayServiceTests.StreamEvents_WhenEventIsWritten_RecordsSendDuration` as a known flake that "passed solo on rerun". The root cause is the `MeterListener` subscribes by `instrument.Meter.Name == GatewayMetrics.MeterName` (a *process-shared* constant `"MxGateway.Server"`), not by the specific `GatewayMetrics` instance constructed in the test. Tests-012 made the xUnit parallelism policy explicit (`parallelizeTestCollections: true`, `maxParallelThreads: -1`), and every other test that builds its own `GatewayMetrics()` and exercises `MxAccessGatewayService.StreamEvents` or `EventStreamService.StreamEventsAsync` (e.g. the new `StreamEventsAsync_*` family added by Tests-026 and Server-041, plus the pre-existing `StreamEventsAsync_YieldsEventsInWorkerOrder` etc.) routes through `GatewayMetrics.RecordEventStreamSend` → the same histogram name `mxgateway.events.stream_send.duration`. When two such tests run concurrently in the same xUnit process, the `MeterListener` in this test sees measurements from *both* meters and `families.Count` grows to >1, breaking `Assert.Equal([MxEventFamily.OnDataChange.ToString()], families)`. Solo reruns pass because no other producer is alive. This is exactly the cross-test mutable-state pattern Tests-012 set the guardrail comment against.
 
 **Recommendation:** Either (a) filter the `MeterListener` callback by the specific `Meter` instance — capture `metrics._meter` (or expose `GatewayMetrics.Meter`) and compare with `ReferenceEquals(instrument.Meter, expectedMeter)` instead of comparing `Meter.Name`; or (b) place this test in a single-threaded `[Collection("GatewayMetrics-Listener")]` so no other `RecordEventStreamSend` producer runs concurrently. Option (a) is preferred because it removes the cross-talk vector permanently and lets the test stay parallelisable.
 
+**Resolution:** 2026-05-24 — Applied option (a). Added an `internal Meter Meter => _meter;` accessor on `GatewayMetrics` (visible to the Tests project via the existing `InternalsVisibleTo`) and changed both the `InstrumentPublished` filter and the `SetMeasurementEventCallback<double>` filter in `StreamEvents_WhenEventIsWritten_RecordsSendDuration` from `instrument.Meter.Name == GatewayMetrics.MeterName` to `ReferenceEquals(instrument.Meter, metrics.Meter)`. Added a companion regression `StreamEvents_RecordSendDurationListener_IgnoresMeasurementsFromOtherMetersWithSameName` that constructs a second `GatewayMetrics`, records an `OnWriteComplete` measurement on it before the test-under-test publishes, and asserts the listener captures only the test-under-test's `OnDataChange` family. Confirmed the regression catches the original `Meter.Name`-only filter (got `["OnWriteComplete", "OnDataChange"]` for `["OnDataChange"]`) by temporarily reverting the filter shape; restored ReferenceEquals after. Suite green 3/3 (512/512); the two Tests-027 tests pass 5/5 solo. The cross-talk vector is permanently closed without giving up parallelism.
+
 ### Tests-028
 
 | Field | Value |
@@ -501,12 +503,14 @@ The cancellation tests for `WorkerClient` in `WorkerClientTests` *do* exercise t
 | Severity | Low |
 | Category | Testing coverage |
 | Location | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Sessions/SessionManagerTests.cs:466-496,802-807`, `src/ZB.MOM.WW.MxGateway.Server/Sessions/SessionManager.cs:216-253` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** The new `KillWorkerAsync_KillsWorkerAndRemovesSession` (line 466) and `KillWorkerAsync_WhenSessionMissing_ThrowsSessionNotFound` (line 486) pin the new kill-path entry, but they do not pin the `reason` argument propagating through the chain. `SessionManager.KillWorkerAsync(sessionId, reason, ct)` validates `reason` with `ArgumentException.ThrowIfNullOrWhiteSpace(reason)` (line 221), calls `session.KillWorker(reason)` (line 229), and logs `reason={Reason}` (line 251); but the `FakeWorkerClient.Kill(string reason)` discards the argument (line 803-807) and the assertion is only `Assert.Equal(1, workerClient.KillCount)`. A regression that (a) hard-coded an internal `"unspecified"` reason between `SessionManager` and `GatewaySession`, (b) swapped to a different overload that dropped the reason, or (c) deleted the `ThrowIfNullOrWhiteSpace` guard would all pass the current tests. The dashboard caller (`DashboardSessionAdminService.KillWorkerAsync`) passes a hard-coded `"dashboard-admin-kill"` reason and the only test that observes it (`KillWorkerAsync_AdminKillsWorker`) asserts `!string.IsNullOrWhiteSpace(LastKillReason)` rather than pinning the value — so the same-class drift is also untested.
 
 **Recommendation:** (1) Capture `LastKillReason` on `FakeWorkerClient.Kill` and assert `KillWorkerAsync_KillsWorkerAndRemovesSession` propagates the test-supplied `"test-kill"` string end-to-end. (2) Add `KillWorkerAsync_WithBlankReason_ThrowsArgumentException` (parameterised over `null`, `""`, `"   "`) to pin the `ArgumentException.ThrowIfNullOrWhiteSpace` guard. (3) Tighten `DashboardSessionAdminServiceTests.KillWorkerAsync_AdminKillsWorker` to `Assert.Equal("dashboard-admin-kill", sessionManager.LastKillReason)` so a future reason-string change is a deliberate test update.
 
+**Resolution:** 2026-05-24 — Added `LastKillReason` to `FakeWorkerClient` in `SessionManagerTests.cs` and set it inside `Kill(string reason)`. Tightened `KillWorkerAsync_KillsWorkerAndRemovesSession` to assert `workerClient.LastKillReason == "test-kill"`, pinning the end-to-end propagation from `SessionManager.KillWorkerAsync` → `session.KillWorker(reason)` → `IWorkerClient.Kill(reason)`. Added `KillWorkerAsync_WithBlankReason_ThrowsArgumentException` as a `[Theory]` over `""`, `" "`, `"\t"` plus a separate `KillWorkerAsync_WithNullReason_ThrowsArgumentNullException` fact (xUnit `InlineData` cannot carry `null` for a non-nullable string, and `ArgumentException.ThrowIfNullOrWhiteSpace` throws `ArgumentNullException` for `null`). Both new tests confirm `KillCount == 0` and the session remains registered, proving the guard fires before any lookup or worker call. Tightened `DashboardSessionAdminServiceTests.KillWorkerAsync_AdminKillsWorker` to `Assert.Equal("dashboard-admin-kill", sessionManager.LastKillReason)`. All affected tests pass; suite green.
+
 ### Tests-029
 
 | Field | Value |
@@ -514,12 +518,16 @@ The cancellation tests for `WorkerClient` in `WorkerClientTests` *do* exercise t
 | Severity | Low |
 | Category | Error handling & resilience |
 | Location | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardSessionAdminServiceTests.cs:61-106,139-222`, `src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardSessionAdminService.cs:77-125` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** The new `DashboardSessionAdminServiceTests` covers the happy path and the viewer-denial path for both `CloseSessionAsync` and `KillWorkerAsync`, plus `CloseSessionAsync_WhenSessionMissing_ReportsFriendlyError` for the close-side `SessionNotFound` catch — but the kill-side error branches are not tested. The product code's `KillWorkerAsync` (lines 111-114) has the same `SessionNotFound` catch returning `"Session {id} was not found."` and (lines 115-124) a generic `SessionManagerException` catch returning `"Kill failed: {message}"`; neither is exercised. The fake's `KillWorkerAsync` (lines 200-209) only succeeds — there is no `KillThrowsNotFound` / `KillThrowsGeneric` configuration option matching the existing `CloseThrowsNotFound`. Symmetrically, `CloseSessionAsync` has the same `IsNullOrWhiteSpace(sessionId)` guard (line 37-40) but no blank-id test even though `KillWorkerAsync_BlankSessionId_ReturnsFailure` exists for the parallel kill guard — a guard-removal regression on close would slip through.
 
 **Recommendation:** Mirror the existing close-side fixtures onto the kill side: add `KillThrowsNotFound` / `KillThrowsGeneric` init-flags to the `FakeSessionManager`, then `KillWorkerAsync_WhenSessionMissing_ReportsFriendlyError`, `KillWorkerAsync_WhenSessionManagerThrows_ReportsKillFailedMessage`, and `CloseSessionAsync_BlankSessionId_ReturnsFailure`. These are mechanical copies of the existing patterns and bring close/kill coverage into symmetry.
 
+**Re-triage note:** The Server batch already added `CloseSessionAsync_WhenManagerThrowsUnexpected_ReturnsFriendlyFail` and `KillWorkerAsync_WhenManagerThrowsUnexpected_ReturnsFriendlyFail` (the Server-050 regressions visible at HEAD lines 125-162 of the test file), so the kill-side `SessionManagerException` general-catch branch and the close-side parallel are both covered there in a generic-exception shape. The only remaining asymmetry was the blank-session-id guard, per the prompt scope.
+
+**Resolution:** 2026-05-24 — Added `CloseSessionAsync_BlankSessionId_ReturnsFailure` to `DashboardSessionAdminServiceTests`. The new test invokes `service.CloseSessionAsync(adminUser, "   ", ct)` and asserts `Succeeded == false` and `sessionManager.CloseCount == 0`, pinning the `string.IsNullOrWhiteSpace(sessionId)` guard at `DashboardSessionAdminService.cs:52-55`. This brings close/kill blank-id coverage into symmetry with the existing `KillWorkerAsync_BlankSessionId_ReturnsFailure`. The `KillThrowsNotFound` / `KillThrowsGeneric` extensions from the original recommendation are not needed because the unexpected-throw branches are already covered by the Server-050 regressions noted above. All tests pass; suite green.
+
 ### Tests-030
 
 | Field | Value |
@@ -527,12 +535,14 @@ The cancellation tests for `WorkerClient` in `WorkerClientTests` *do* exercise t
 | Severity | Low |
 | Category | Testing coverage |
 | Location | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardApiKeyManagementServiceTests.cs:115-163`, `src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardApiKeyManagementService.cs:146-177` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** The three new `DeleteAsync_*` fixtures cover unauthorised user, success path with audit, and store-refuses-with-friendly-error. They do not exercise two production behaviours: (1) `DeleteAsync_WhenStoreRefuses_ReportsFriendlyError` (line 151-163) does not construct or inject a `FakeApiKeyAuditStore`, so it never observes that the product code still emits an audit entry with `EventType = "dashboard-delete-key"` and `Details = "not-found-or-active"` on the failure branch (`AppendAuditAsync` runs unconditionally at line 167-172). A regression that placed the `AppendAuditAsync` call inside the `if (deleted)` branch would silently drop the audit trail for refused deletes — a real audit-completeness gap. (2) There is no `DeleteAsync_BlankKeyId_ReturnsFailure` or `DeleteAsync_InvalidKeyId_ReturnsFailure` test, even though `ValidateKeyId(keyId)` (line 156-160) guards on the same conditions as Create/Revoke/Rotate. The `Revoke`/`Rotate` paths have equivalent fixtures (the file's earlier tests cover them); only Delete is missing them.
 
 **Recommendation:** (1) Add a `FakeApiKeyAuditStore` to `DeleteAsync_WhenStoreRefuses_ReportsFriendlyError` and assert it contains exactly one entry with `EventType == "dashboard-delete-key"` and `Details == "not-found-or-active"`. (2) Add `DeleteAsync_BlankKeyId_ReturnsFailure` (parameterised over `null`, `""`, `"   "`) and `DeleteAsync_InvalidKeyId_ReturnsFailure` (a keyId with characters the `ValidateKeyId` rules reject) to pin the validation branch end-to-end.
 
+**Resolution:** 2026-05-24 — Renamed `DeleteAsync_WhenStoreRefuses_ReportsFriendlyError` to `DeleteAsync_WhenStoreRefuses_ReportsFriendlyErrorAndAudits` and extended it to inject a `FakeApiKeyAuditStore`; the test now asserts the single audit entry has `EventType == "dashboard-delete-key"`, `KeyId == "operator01"`, and `Details == "not-found-or-active"`. This pins the unconditional-audit invariant at `DashboardApiKeyManagementService.cs:167-172` — a regression moving the `AppendAuditAsync` call inside `if (deleted)` would now fail the test. Added `DeleteAsync_BlankKeyId_ReturnsFailure` as a `[Theory]` over `""`, `" "`, `"\t"` that asserts `Succeeded == false`, `adminStore.DeleteCount == 0`, AND `auditStore.Entries` is empty — pinning that the `ValidateKeyId` guard at line 156-160 fires before any store or audit work. All tests pass; suite green.
+
 ### Tests-031
 
 | Field | Value |
@@ -540,8 +550,10 @@ The cancellation tests for `WorkerClient` in `WorkerClientTests` *do* exercise t
 | Severity | Low |
 | Category | Concurrency & thread safety |
 | Location | `src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardSnapshotPublisherTests.cs:22-61` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `ExecuteAsync_WhenSnapshotServiceThrowsOnce_ReconnectsAfterDelay` records `startedAt = DateTimeOffset.UtcNow` *before* calling `publisher.StartAsync(...)`, then asserts `secondSubscribeAt - startedAt >= reconnectDelay - 10ms` (line 59). The measured gap is *not* the reconnect delay in isolation — it is `(StartAsync scheduling) + (first WatchSnapshotsAsync setup + Task.Yield) + (throw) + reconnect delay + (second WatchSnapshotsAsync setup)`. On a slow/contended CI agent the first three terms easily dominate (favouring the assertion); but on a fast machine, Windows `Task.Delay(50ms)` rounds up to the next ~15.6 ms tick boundary and may return at ~46-50 ms relative to schedule, while the first three terms can be sub-millisecond — so the gap measurement can land within 1-2 ms of the lower bound, and the 10 ms slack may not absorb a single missed quantum. This is a latent flake of the same flavour as Tests-006 (heartbeat timing) but on a wall-clock dependency the test cannot inject around because `DashboardSnapshotPublisher` uses `Task.Delay(_reconnectDelay)` directly. Tests-006 / Tests-017 moved heartbeat tests onto `ManualTimeProvider`; this test cannot do that without a product change to use a `TimeProvider`-aware delay.
 
 **Recommendation:** (a) The cheap fix: have `ThrowOnceThenYieldSnapshotService` record `_firstThrowAt = DateTimeOffset.UtcNow` immediately before the `throw`, and change the assertion to `secondSubscribeAt - firstThrowAt >= reconnectDelay - 10ms` — the gap then measures only the reconnect delay, eliminating the variable scheduling baseline. (b) The deeper fix: extend `DashboardSnapshotPublisher` to accept an `ITimeProvider`-style delay seam (or a virtual `DelayAsync` hook) so a `ManualTimeProvider` could advance time deterministically. (a) is preferred for now; (b) belongs as a follow-up if more reconnect-loop tests are added.
+
+**Resolution:** 2026-05-24 — Applied option (a). Added `FirstThrowAt` to `ThrowOnceThenYieldSnapshotService` and set it via `FirstThrowAt = DateTimeOffset.UtcNow;` immediately before the first-call `throw`. Removed the pre-`StartAsync` `startedAt` baseline; the assertion now reads `gap = secondSubscribeAt - firstThrowAt` (both timestamps captured inside the fake), and the 10 ms slack absorbs the Windows `Task.Delay` quantum without the variable `StartAsync` / scheduling overhead in the baseline. This is the same flake-isolation pattern Tests-006 / Tests-017 used (measuring only the production delay, not test-side setup). Suite green; the test passes deterministically across repeated runs.

docs/CrossLanguageSmokeMatrix.md

@@ -51,6 +51,19 @@ The shared inputs are:
 The commands in the matrix use `MXGATEWAY_API_KEY` through each CLI's
 `api-key-env` flag. They must not embed bearer tokens or raw API keys.
 
+### TLS variant
+
+The matrix runs over plaintext (`h2c`) by default. A TLS variant exists but stays
+a manual/opt-in run, consistent with the gate above, because it needs the gateway
+started with an HTTPS endpoint (an `https://` `MXGATEWAY_ENDPOINT`) and each CLI
+switched to its TLS flag (`--tls` / `-tls` / `--plaintext=false` /
+`plaintext=False`). The clients are lenient by default and accept the gateway's
+auto-generated self-signed certificate without extra trust setup, except the Rust
+CLI, which is pin-only and needs `--ca-file` or `--require-certificate-validation`
+(and Python uses trust-on-first-use). See
+[Gateway Configuration — Automatic self-signed certificate](./GatewayConfiguration.md#automatic-self-signed-certificate)
+and each client README for the per-client TLS flags.
+
 ## JSON Comparison
 
 Every command in the matrix requests JSON output. A runner can compare the

docs/DesignDecisions.md

@@ -362,6 +362,55 @@ Dashboard access should require API-key-backed dashboard authentication with
 is enabled by default through `Dashboard:AllowAnonymousLocalhost`; the bypass is
 limited to loopback requests.
 
+## Lazy Browse Is Wire-Only
+
+Decision: the gateway continues to pull the full Galaxy hierarchy on each
+deploy. `BrowseChildren` and the lazy dashboard render only avoid sending and
+DOM-materializing the full tree — they do not push laziness into SQL or cache
+loading.
+
+Rationale: snapshot persistence and the dashboard summary both depend on a
+fully-materialized cache. Lazy SQL would increase per-click latency on a
+deployment-heavy box, multiply per-session SQL connections, and complicate the
+cold-start path. Wire-side laziness solves the actual pain (oversized gRPC
+replies and a heavy DOM) without disturbing the materialization model.
+
+## TLS Auto-Certificate and Lenient Client Trust
+
+Decision: when a Kestrel `https://` endpoint is configured without a certificate
+of its own (and no `Kestrel:Certificates:Default` is set), the gateway generates
+and persists a self-signed certificate rather than failing to start. Clients
+connecting over TLS without a pinned CA accept whatever certificate the server
+presents by default; pinning a CA restores full verification.
+
+Rationale: `mxaccessgw` is an internal tool with no PKI to issue or distribute
+certificates. The prior behavior — an `https` endpoint with no certificate
+fails at startup with Kestrel's opaque "no server certificate was specified"
+error — pushed operators toward plaintext (`h2c`), exposing the API key and
+request payloads on the wire. Auto-generating a long-lived, persisted, reused
+certificate lets TLS "just work" with zero certificate management, while the
+lenient client default means clients connect to that self-signed certificate
+without a manual trust step. Both choices are deliberate, not oversights:
+strict-by-default would force PKI work this tool does not warrant. Plaintext-only
+deployments are untouched — no certificate or key material is written for them —
+and an operator who supplies a real certificate transparently overrides the
+generated one.
+
+Two clients diverge from "accept any certificate" because their gRPC stacks lack
+a per-channel skip-verify hook:
+
+- Python uses trust-on-first-use: it fetches the server's presented certificate
+  over a separate unverified probe and pins it for the channel, and defaults the
+  SNI/target-name override to `localhost` (the generated certificate always
+  carries a `localhost` SAN).
+- Rust is pin-only: tonic exposes no public hook to inject a custom certificate
+  verifier, so TLS over Rust requires either a pinned CA or an explicit opt-in to
+  system-trust verification; otherwise connecting returns a clear, actionable
+  error.
+
+See [Gateway Configuration — Automatic self-signed certificate](./GatewayConfiguration.md#automatic-self-signed-certificate)
+and the per-client READMEs for the as-built behavior.
+
 ## Later Revisit Items
 
 These are explicit post-v1 revisit items, not open blockers:

docs/GalaxyRepository.md

@@ -36,6 +36,7 @@ The service is defined in
 | `GetLastDeployTime` | Returns the cached `galaxy.time_of_last_deploy`. Served from the shared hierarchy cache; refreshed in the background. |
 | `DiscoverHierarchy` | Returns one page of the deployed hierarchy plus each returned object's attributes (configured and built-in — see [Built-in vs configured attributes](#built-in-vs-configured-attributes)). **Served from cache** — see [Hierarchy Cache](#hierarchy-cache). |
 | `WatchDeployEvents` | **Server-streaming.** The server emits the current state immediately on subscribe (so clients can bootstrap without waiting), then emits one event per detected deploy change. See [Deploy Notifications](#deploy-notifications). |
+| `BrowseChildren` | Returns the direct children of one parent object (or root objects when `parent` is unset). Filters mirror `DiscoverHierarchy`. Includes a per-child `has_children` hint so UIs can draw expand triangles without an extra round trip. **Served from cache.** |
 
 `DiscoverHierarchy` is a paged unary RPC. The raw request accepts `page_size`
 and `page_token`; the server defaults omitted page size to 1000 objects and
@@ -52,6 +53,57 @@ alarm-only, historized-only, and `include_attributes = false` for a skeleton
 tree. All filters are applied with AND semantics, and `total_object_count`
 reports the post-filter count.
 
+### BrowseChildren
+
+`BrowseChildren` is an OPC UA-style lazy expand: clients that walk one level at
+a time — UI trees, OPC UA address-space bridges — call it instead of paging the
+full hierarchy with `DiscoverHierarchy`.
+
+**Parent selection.** The `parent` oneof accepts `parent_gobject_id`,
+`parent_tag_name`, or `parent_contained_path`. An empty oneof returns root
+objects — those whose `parent_gobject_id` is 0.
+
+**Filters.** Category ids, template-chain substring, tag-name glob, alarm-only,
+historized-only, and `include_attributes` all behave identically to
+`DiscoverHierarchy` and are AND-combined. One important difference applies to
+`alarm_bearing_only` and `historized_only`: an ancestor that does not itself
+carry a matching attribute is still returned when one of its descendants does.
+This is intentional — without it a UI tree cannot navigate to the matching
+leaves. `DiscoverHierarchy`'s flat-list semantics filter out such intermediate
+ancestors; `BrowseChildren` retains them so the path to each match remains
+traversable.
+
+**`child_has_children` hint.** The reply carries a boolean parallel to
+`children`, set true when the child has at least one matching descendant under
+the same filter set. UIs can use this to decide whether to draw an expand
+triangle without issuing a follow-up `BrowseChildren` call. Because the hint is
+computed against the *filtered* descendant set, a branch that contains no
+matching objects gets `false`, not `true`.
+
+**Paging.** Default page size is 500; the server caps any requested size at
+5000. Page tokens encode `(cache_sequence, parent_id, filter_signature,
+offset)`. A token from a different cache generation or a different filter set
+returns `InvalidArgument`. The error messages reference "DiscoverHierarchy
+page_token" because `BrowseChildren` reuses the same encoding and validation
+path — if you see that wording in a `BrowseChildren` context it is expected.
+
+**Errors.**
+
+| Condition | Status code |
+|-----------|-------------|
+| Unknown parent | `NotFound` |
+| First load not yet complete after 5 s | `Unavailable` |
+| Stale or filter-mismatched page token | `InvalidArgument` |
+| Missing `metadata:read` scope | `PermissionDenied` |
+| No API key | `Unauthenticated` |
+
+**Authorization.** Same `metadata:read` scope as the other Galaxy RPCs.
+`browse_subtrees` API-key constraints intersect with the result set.
+
+**Sort order.** Areas first, then `OrdinalIgnoreCase` by display name
+(`browse_name` → `contained_name` → `tag_name`). Matches the dashboard tree so
+server and dashboard views are consistent.
+
 ## Hierarchy Cache
 
 The gateway holds a single shared `IGalaxyHierarchyCache`
@@ -271,9 +323,13 @@ fields cannot express null. Use it to distinguish "no dimension reported" from
 ```text
 gRPC client(s)
   -> GalaxyRepositoryGrpcService (src/ZB.MOM.WW.MxGateway.Server/Grpc/)
-    DiscoverHierarchy, GetLastDeployTime  -> IGalaxyHierarchyCache.Current
-    WatchDeployEvents                     -> IGalaxyDeployNotifier
-    TestConnection                        -> GalaxyRepository  (direct SQL)
+    DiscoverHierarchy, GetLastDeployTime, BrowseChildren -> IGalaxyHierarchyCache.Current
+    WatchDeployEvents                                    -> IGalaxyDeployNotifier
+    TestConnection                                       -> GalaxyRepository  (direct SQL)
+
+Dashboard (Blazor)
+  -> IDashboardBrowseService (DashboardBrowseService)
+    -> GalaxyBrowseProjector over IGalaxyHierarchyCache.Current
 
 GalaxyHierarchyRefreshService (BackgroundService)
   -> IGalaxyHierarchyCache.RefreshAsync
@@ -309,9 +365,17 @@ Component breakdown:
   (`src/ZB.MOM.WW.MxGateway.Server/Grpc/GalaxyProtoMapper.cs`) converts row models to
   proto messages. Used by the cache during refresh to materialize the reply
   once.
+- `GalaxyBrowseProjector`
+  (`src/ZB.MOM.WW.MxGateway.Server/Galaxy/GalaxyBrowseProjector.cs`) projects one level
+  of children out of an immutable cache entry. Memoizes the filtered child list
+  per cache-entry instance so repeated paging is an O(pageSize) slice rather than an
+  O(siblings) filter scan. The memo is keyed on the cache entry reference, so a new
+  entry from the background refresh makes the stale memo unreachable and it is
+  collected with it. `DashboardBrowseService` wraps this projector to drive the
+  dashboard's lazy-expand tree.
 - `GalaxyRepositoryGrpcService`
   (`src/ZB.MOM.WW.MxGateway.Server/Grpc/GalaxyRepositoryGrpcService.cs`) implements
-  the four RPCs.
+  the five RPCs.
 
 ## Configuration
 

docs/GatewayConfiguration.md

@@ -46,6 +46,7 @@ paths, timeouts, queue sizes, enum values, or protocol values are invalid.
     "Dashboard": {
       "Enabled": true,
       "AllowAnonymousLocalhost": true,
+      "RequireHttpsCookie": true,
       "SnapshotIntervalMilliseconds": 1000,
       "RecentFaultLimit": 100,
       "RecentSessionLimit": 200,
@@ -146,6 +147,7 @@ the affected stream while the MXAccess session remains active.
 |--------|---------|-------------|
 | `MxGateway:Dashboard:Enabled` | `true` | Enables Blazor Server dashboard route mapping. The dashboard mounts at the host root (`/`); there is no separate path-base prefix. |
 | `MxGateway:Dashboard:AllowAnonymousLocalhost` | `true` | Allows loopback dashboard requests to bypass the dashboard cookie requirement for local development. Remote requests still require dashboard authentication. |
+| `MxGateway:Dashboard:RequireHttpsCookie` | `true` | Sets the dashboard auth cookie's secure policy. `true` keeps `CookieSecurePolicy.Always` — the cookie is only sent over HTTPS, which matches a production HTTPS deployment. Set to `false` for plain-HTTP dev deployments to use `CookieSecurePolicy.SameAsRequest`; the cookie is still flagged Secure on HTTPS requests, but it can round-trip over HTTP. Browsers drop Secure cookies set over HTTP from non-localhost hosts, so leaving this `true` while serving the dashboard over plain HTTP will break login from any remote browser. |
 | `MxGateway:Dashboard:SnapshotIntervalMilliseconds` | `1000` | Dashboard snapshot refresh interval used by the snapshot SignalR hub and the pages that subscribe to it. |
 | `MxGateway:Dashboard:RecentFaultLimit` | `100` | Maximum number of fault summaries projected into each dashboard snapshot. |
 | `MxGateway:Dashboard:RecentSessionLimit` | `200` | Maximum number of session summaries projected into each dashboard snapshot. |
@@ -227,6 +229,185 @@ behavior.
 The alarm monitor is independent of client sessions: `AcknowledgeAlarm` and
 `StreamAlarms` are session-less RPCs served by the monitor.
 
+## Host Endpoints and Transport Security (Kestrel)
+
+The listening endpoints are **not** part of the `MxGateway` section. The gateway
+uses the stock ASP.NET Core host (`WebApplication.CreateBuilder`) with no
+`ConfigureKestrel` call in code, so endpoints come entirely from the standard
+`Kestrel` configuration section. On the deployed hosts these values are supplied
+as NSSM environment variables (`Kestrel__Endpoints__...`), not from
+`appsettings.json`.
+
+Two named endpoints are bound:
+
+| Endpoint name | Purpose | Protocol requirement |
+|---|---|---|
+| `Http` | Public gRPC API (sessions, invoke, events, Galaxy browse) | HTTP/2 |
+| `Dashboard` | Blazor dashboard and SignalR hubs | HTTP/1.1 (HTTP/2 optional) |
+
+Both endpoints share one routing pipeline; the names only select which TCP port
+serves which traffic. The gRPC endpoint must negotiate **HTTP/2**, which drives
+the protocol settings below.
+
+### Plaintext (current deployments)
+
+Both running hosts (`10.100.0.48` and `wonder-app-vd03`) serve the gRPC port in
+**cleartext HTTP/2 (`h2c`)**. Because cleartext HTTP/2 has no ALPN to negotiate
+the protocol, the gRPC endpoint must be pinned to `Http2` with prior knowledge:
+
+```text
+Kestrel__Endpoints__Http__Url=http://0.0.0.0:5120
+Kestrel__Endpoints__Http__Protocols=Http2
+Kestrel__Endpoints__Dashboard__Url=http://0.0.0.0:5130
+```
+
+In this mode all client↔gateway traffic — including the
+`authorization: Bearer mxgw_...` API key and any `WriteSecured` / `AuthenticateUser`
+payloads — crosses the network **unencrypted**. This is acceptable only on a
+trusted/isolated network segment. Prefer TLS for anything else.
+
+### TLS
+
+To encrypt the gRPC channel, give the `Http` endpoint an `https://` URL and a
+certificate. Over TLS, ALPN negotiates HTTP/2, so the explicit `Protocols=Http2`
+pin is no longer required (the default `Http1AndHttp2` works for gRPC over TLS).
+
+`appsettings.json` form:
+
+```json
+{
+  "Kestrel": {
+    "Endpoints": {
+      "Http": {
+        "Url": "https://0.0.0.0:5120",
+        "Certificate": {
+          "Path": "C:\\ProgramData\\MxGateway\\certs\\gateway.pfx",
+          "Password": "<pfx-password>"
+        }
+      },
+      "Dashboard": {
+        "Url": "https://0.0.0.0:5130",
+        "Certificate": {
+          "Path": "C:\\ProgramData\\MxGateway\\certs\\gateway.pfx",
+          "Password": "<pfx-password>"
+        }
+      }
+    }
+  }
+}
+```
+
+Equivalent NSSM environment-variable form (how config is delivered on the hosts —
+see [server deploy mechanics in the project notes]):
+
+```text
+Kestrel__Endpoints__Http__Url=https://0.0.0.0:5120
+Kestrel__Endpoints__Http__Certificate__Path=C:\ProgramData\MxGateway\certs\gateway.pfx
+Kestrel__Endpoints__Http__Certificate__Password=<pfx-password>
+Kestrel__Endpoints__Dashboard__Url=https://0.0.0.0:5130
+Kestrel__Endpoints__Dashboard__Certificate__Path=C:\ProgramData\MxGateway\certs\gateway.pfx
+Kestrel__Endpoints__Dashboard__Certificate__Password=<pfx-password>
+```
+
+Certificate sourcing options (any standard ASP.NET Core form is accepted):
+
+| Form | Keys |
+|---|---|
+| PFX file | `Certificate:Path` (+ `Certificate:Password` if encrypted) |
+| PEM pair | `Certificate:Path` (cert) + `Certificate:KeyPath` (private key) |
+| Windows cert store | `Certificate:Subject`, `Certificate:Store` (e.g. `My`), `Certificate:Location` (`LocalMachine`), `Certificate:AllowInvalid` |
+
+The certificate's CN/SAN must cover the host name clients dial (or clients must
+set a server-name override — see below). The dashboard endpoint can keep its own
+certificate independent of the gRPC endpoint; pair this with
+`MxGateway:Dashboard:RequireHttpsCookie` (`true`) for production HTTPS.
+
+### Automatic self-signed certificate
+
+`mxaccessgw` is an internal tool with no PKI to issue certificates, so requiring
+an operator to supply one before TLS works pushed deployments toward plaintext.
+To avoid that, the gateway fills in a self-signed certificate when an HTTPS
+endpoint is configured without one.
+
+**Trigger.** At startup the gateway inspects `Kestrel:Endpoints:*`. If any
+endpoint has an `https://` URL and no `Certificate` subsection of its own, and no
+`Kestrel:Certificates:Default` is set, the gateway generates (or loads) a
+persisted self-signed certificate and wires it in as the HTTPS *default* via
+`ConfigureHttpsDefaults`. All-plaintext deployments are untouched: when no HTTPS
+endpoint is configured, no certificate or key material is generated or written.
+
+**Generated certificate.** ECDSA P-256, `serverAuth` EKU, validity ≈
+`ValidityYears` (default 10 years, with one day of clock-skew slack before
+`notBefore`). SANs cover `localhost`, the machine name (and its FQDN when
+resolvable), each entry in `AdditionalDnsNames`, and the loopback addresses
+`127.0.0.1` and `::1`.
+
+**`MxGateway:Tls:*` options.** All optional; the zero-config path needs none of
+them.
+
+| Option | Default | Purpose |
+|---|---|---|
+| `Tls:SelfSignedCertPath` | `C:\ProgramData\MxGateway\certs\gateway-selfsigned.pfx` | Where the generated certificate is persisted |
+| `Tls:ValidityYears` | `10` | Lifetime of the generated certificate (validated 1–100) |
+| `Tls:AdditionalDnsNames` | `[]` | Extra DNS SANs (e.g. a load-balancer name) |
+| `Tls:RegenerateIfExpired` | `true` | Replace an expired persisted certificate instead of failing |
+
+`ValidityYears` is validated by `GatewayOptionsValidator` (range 1–100); the
+"HTTPS endpoint configured but no certificate available" fail-fast lives in the
+bootstrap/provider, because the validator only sees the `MxGateway` section, not
+`Kestrel:Endpoints`.
+
+**Persistence.** The PFX is written with an **empty** export password — a random
+in-memory password could not be reused across restarts, which the
+persist-and-reuse model requires. The private key is instead protected at rest by
+filesystem permissions: a restrictive ACL on Windows (SYSTEM + Administrators,
+inherited ACEs stripped) on the `certs` directory and file, and mode `0600` on
+non-Windows. The write is atomic (hardened temp file, then move). The persisted
+certificate is reused across restarts (stable thumbprint, so CA-pinning clients
+keep working) and regenerated only when it is missing, expired (and
+`RegenerateIfExpired` is `true`), or unreadable/corrupt. If the directory is not
+writable or the ACL cannot be applied, the gateway fails fast with a diagnostic
+naming the path rather than falling back to an in-memory certificate.
+
+**Logging.** On generate or load, the gateway logs the certificate thumbprint,
+SAN list, and `notAfter` at Information. The PFX bytes, export password, and
+private key are never logged.
+
+**Operator override.** The generated certificate is only the HTTPS *default*. To
+use a real certificate, configure one explicitly — either per endpoint via
+`Kestrel:Endpoints:<name>:Certificate` (`Path`/`Subject`/`Thumbprint`, etc., as
+in the table above) or globally via `Kestrel:Certificates:Default`. An
+explicitly-configured certificate takes precedence, and the gateway then writes
+no self-signed material.
+
+### Client side
+
+Each official client opts into TLS explicitly. For the .NET client
+(`MxGatewayClientOptions`):
+
+| Option | Effect |
+|---|---|
+| `UseTls` (default `false`) | Enables TLS. Requires an `https://` endpoint; an `https://` endpoint without `UseTls` fails validation, and vice versa. |
+| `CaCertificatePath` | Pins a custom root (self-signed / private CA) using `CustomRootTrust` chain validation instead of the OS trust store; the .NET client also enforces the certificate hostname/SAN match on this path. |
+| `RequireCertificateValidation` (default `false`) | Forces OS/system-trust verification on a TLS connection with no pinned CA. Leave `false` for the lenient default. |
+| `ServerNameOverride` | SNI / certificate host name override when the dialed host differs from the certificate CN/SAN. |
+
+To pair with the auto-generated self-signed certificate above, the clients are
+**lenient by default**: a TLS connection with no pinned CA accepts whatever
+certificate the gateway presents. Pin `CaCertificatePath` to verify, or set
+`RequireCertificateValidation` to force system-trust verification without
+pinning. The other language clients expose the equivalent options; the exact
+behavior differs per stack — Python uses trust-on-first-use and Rust is pin-only.
+See each client README for the as-built behavior.
+
+### Gateway↔worker IPC
+
+Transport security here applies only to the public gRPC channel. The
+gateway↔worker link is a per-session **named pipe**
+(`mxaccess-gateway-{gatewayPid}-{sessionId}`), not a network socket. It is not
+TLS-encrypted and does not need to be: it never leaves the local Windows host and
+is secured by the OS pipe ACL. See [Worker Frame Protocol](./WorkerFrameProtocol.md).
+
 ## Related Documentation
 
 - [Gateway Process Detailed Design](./GatewayProcessDesign.md)

docs/Grpc.md

@@ -243,9 +243,27 @@ services.AddGrpc(options => options.Interceptors.Add<GatewayGrpcAuthorizationInt
 
 Because the interceptor runs before any handler, `MxAccessGatewayService` can safely assume the call has been authorized and that `IGatewayRequestIdentityAccessor.Current` is populated. The handler's only responsibility is to read the identity for `OpenSession` so the session is owned by the authenticated principal; it does not perform any authorization checks of its own. See [Authorization](./Authorization.md) for the policy and identity model.
 
+## Transport Security
+
+The gRPC endpoint runs over HTTP/2, in cleartext (`h2c`) or TLS depending on the
+Kestrel endpoint configuration. The current deployments serve it in cleartext, so
+the API key and request payloads cross the network unencrypted. The endpoint,
+protocol pinning, and TLS certificate configuration — plus the corresponding
+client `UseTls` / `CaCertificatePath` options — are documented in
+[Host Endpoints and Transport Security](./GatewayConfiguration.md#host-endpoints-and-transport-security-kestrel).
+
+To make TLS usable without PKI, the gateway can auto-generate and persist a
+self-signed certificate when an HTTPS endpoint is configured without one, and the
+language clients are lenient by default — a TLS connection with no pinned CA
+accepts the presented certificate (with per-stack nuances: Python is
+trust-on-first-use, Rust is pin-only). See
+[Automatic self-signed certificate](./GatewayConfiguration.md#automatic-self-signed-certificate)
+and each client README for the as-built behavior.
+
 ## Related Documentation
 
 - [Contracts](./Contracts.md)
 - [Sessions](./Sessions.md)
 - [Authorization](./Authorization.md)
+- [Gateway Configuration](./GatewayConfiguration.md)
 - [Gateway Process Design](./GatewayProcessDesign.md)

docs/Metrics.md

@@ -4,7 +4,7 @@ The metrics subsystem exposes counters, histograms, and observable gauges that d
 
 ## Overview
 
-`GatewayMetrics` is a singleton (registered in `GatewayApplication.cs`) that owns a single `Meter` named `ZB.MOM.WW.MxGateway.Server` and a set of synchronised counters, histograms, and observable gauges. Subsystems call typed mutator methods (`SessionOpened`, `CommandFailed`, `EventReceived`, etc.) rather than touching the `Meter` directly, which keeps the OpenTelemetry instrument names and tag conventions in one place. A `lock (_syncRoot)` block guards the scalar fields used by `GetSnapshot`, while per-event maps use `ConcurrentDictionary<string, long>` so the hot event path avoids the lock.
+`GatewayMetrics` is a singleton (registered in `GatewayApplication.cs`) that owns a single `Meter` named `ZB.MOM.WW.MxGateway` and a set of synchronised counters, histograms, and observable gauges. Subsystems call typed mutator methods (`SessionOpened`, `CommandFailed`, `EventReceived`, etc.) rather than touching the `Meter` directly, which keeps the OpenTelemetry instrument names and tag conventions in one place. A `lock (_syncRoot)` block guards the scalar fields used by `GetSnapshot`, while per-event maps use `ConcurrentDictionary<string, long>` so the hot event path avoids the lock.
 
 ## Meter and OpenTelemetry Compatibility
 
@@ -13,7 +13,7 @@ The meter name is exposed as a constant so that hosting code can register it wit
 ```csharp
 public sealed class GatewayMetrics : IDisposable
 {
-    public const string MeterName = "ZB.MOM.WW.MxGateway.Server";
+    public const string MeterName = "ZB.MOM.WW.MxGateway";
 
     public GatewayMetrics()
     {
@@ -50,12 +50,12 @@ All counters are `Counter<long>`. Tag values come from the call sites listed und
 
 ### Histograms
 
-Histograms record durations in milliseconds (the `unit` argument on `CreateHistogram`):
+Histograms record durations in seconds (the `unit` argument on `CreateHistogram`):
 
 ```csharp
-_workerStartupLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.workers.startup.duration", "ms");
-_commandLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.commands.duration", "ms");
-_eventStreamSendLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.events.stream_send.duration", "ms");
+_workerStartupLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.workers.startup.duration", "s");
+_commandLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.commands.duration", "s");
+_eventStreamSendLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.events.stream_send.duration", "s");
 ```
 
 | Instrument | Tags | What it measures |