Merge feat/universal-discovery-browser — Wave-0 universal Discover-backed browser

18 tasks / 9 batch commits. One generic DiscoveryDriverBrowser captures any discovery-capable driver's ITagDiscovery.DiscoverAsync into a browse tree and serves it via the existing picker plumbing, lighting up AbCip/TwinCAT/FOCAS pickers with zero per-driver browser code. Live-gated on docker-dev (binding + PatchForBrowse verified in prod; full tree-render fixture-blocked by ab_server's missing @tags walk). See docs/plans/2026-07-15-universal-discovery-browser-*.
2026-07-15 18:33:46 -04:00
parent c006363ec2 26ef8131b0
commit 056887d6e9
40 changed files with 1875 additions and 37 deletions
@@ -215,5 +215,9 @@ MELSEC is out of the sequence (deferred).

 ## 9. Status

-Research: **done** (8 reports). Designs: **done** (7 design docs). Code: **not started.**
-Next action: execute Wave 0 (universal browser), then Wave 1.
+Research: **done** (8 reports). Designs: **done** (7 design docs). Code: **Wave 0 landed** —
+the universal Discover-backed browser (P1) is code-complete and unit-tested on
+`feat/universal-discovery-browser` (`CapturingAddressSpaceBuilder` + `CapturedTreeBrowseSession`
+ `DiscoveryDriverBrowser`/`IUniversalDriverBrowser` + `BrowserSessionService` fallback +
+`ITagDiscovery.SupportsOnlineDiscovery` gate + AbCip/TwinCAT/FOCAS opt-ins & picker browse UI),
+with the live `/run` gate outstanding. Next action: complete the Wave-0 live gate, then Wave 1.
@@ -1,6 +1,7 @@
 # Universal Discover-backed browser (`DiscoveryDriverBrowser`) — design

-**Status:** draft, 2026-07-15. Foundational Wave-0 item of the next-driver roadmap
+**Status:** P1 implemented 2026-07-15 (code-complete + unit-tested, live `/run` gate pending);
+P2/P3 pending. Foundational Wave-0 item of the next-driver roadmap
 (`docs/research/drivers/README.md`).

 ## 1. Motivation
@@ -1083,6 +1083,40 @@ Identical shape (confirm DriverType string from the FOCAS `Register()`). Note in

 ---

+## Live-gate result (Task 18 — docker-dev, 2026-07-15)
+
+Executed against the local docker-dev rig (both centrals rebuilt from `feat/universal-discovery-browser`)
+with the ControlLogix `ab_server` fixture up on `10.100.0.35:44818`. An AbCip driver (device
+`ab://10.100.0.35:44818/1,0`, **`EnableControllerBrowse` deliberately left off**) was authored under an
+Equipment-kind namespace and bound to an equipment; a tag was added on the Tags-tab TagModal.
+
+- ✅ **Positive binding** — the AbCip address picker renders the **"Browse controller"** button. This
+  exercises the whole `CanBrowse` chain end-to-end: `SupportsOnlineDiscovery=true` → `BrowserSessionService.CanBrowse`
+  → `DiscoveryDriverBrowser.CanBrowse` (constructs a throwaway driver with `PatchForBrowse`) → TagModal
+  `DriverType`/`GetDriverConfigJson` params → `AbCipTagConfigEditor` pass-through → `AbCipAddressPickerBody._canBrowse`.
+- ✅ **Browse invocation runs in production** — clicking Browse drove the full capture path; central-2 logged
+  `BrowserSessionService.OpenUniversalAsync → DiscoveryDriverBrowser.OpenAsync → RunCaptureAsync → CaptureAsync
+  → DiscoverTreeAsync`. Because the driver's authored config did **not** set `EnableControllerBrowse` yet the
+  capture attempted the controller `@tags` walk (which only runs when that flag is true), **`PatchForBrowse`
+  is demonstrably applied end-to-end**. The error surfaced as a graceful UI chip — no dead binding, no crash,
+  no hang; bounded shutdown ran.
+- ✅ **Negative binding** — the Modbus picker shows only the manual Register/Offset/Length builder, **no Browse
+  button** (`SupportsOnlineDiscovery` false; picker body unchanged).
+- ⚠️ **Not verifiable on this fixture** — a *populated* tree render + leaf-commit. The libplctag `ab_server`
+  test sim returns `ErrorUnsupported` for controller symbol enumeration (it implements tag read/write, not the
+  `@tags` Symbol Object walk). This is a **fixture limitation, not a code defect** — the binding is proven alive.
+
+### Follow-ups discovered during the gate
+
+1. **Full tree-render verification is fixture-blocked.** `ab_server` doesn't implement the `@tags` controller
+   walk. To live-verify a populated tree + `TagConfig.FullName` leaf commit, point the universal browser at a
+   symbol-enumeration-capable AB backend (a real ControlLogix, or a sim that serves `@tags`).
+2. **Driver-page address pickers pass no live config.** `AbCipDriverPage`/`TwinCATDriverPage`/`FOCASDriverPage`
+   host the same `*AddressPickerBody` but do **not** pass `DriverType`/`GetConfigJson`, so their (now-visible)
+   Browse button would capture against `"{}"` (no device). Out of Task 14's scope (which listed only the
+   TagEditor pass-through); wire the live form config through there too, or hide the Browse affordance on the
+   driver-config picker.
+
 ## Out of scope (explicitly)

 - TwinCAT/FOCAS live-fixture verification (no shipped fixtures assumed reachable; AbCip is the gate).
@@ -1,25 +1,25 @@
 {
  "planPath": "docs/plans/2026-07-15-universal-discovery-browser-implementation.md",
  "tasks": [
-    {"id": 0, "subject": "Task 0: Branch setup (feat/universal-discovery-browser)", "status": "pending"},
-    {"id": 1, "subject": "Task 1: ITagDiscovery.SupportsOnlineDiscovery default member", "status": "pending", "blockedBy": [0], "parallelWith": [2, 13]},
-    {"id": 2, "subject": "Task 2: Commons project references (Core.Abstractions)", "status": "pending", "blockedBy": [0], "parallelWith": [1, 13]},
-    {"id": 3, "subject": "Task 3: AbCip opt-in SupportsOnlineDiscovery=true", "status": "pending", "blockedBy": [1], "parallelWith": [4, 5]},
-    {"id": 4, "subject": "Task 4: TwinCAT opt-in SupportsOnlineDiscovery=true", "status": "pending", "blockedBy": [1], "parallelWith": [3, 5]},
-    {"id": 5, "subject": "Task 5: FOCAS opt-in SupportsOnlineDiscovery=true", "status": "pending", "blockedBy": [1], "parallelWith": [3, 4]},
-    {"id": 6, "subject": "Task 6: CapturingAddressSpaceBuilder + captured-tree model", "status": "pending", "blockedBy": [1, 2]},
-    {"id": 7, "subject": "Task 7: CapturedTreeBrowseSession", "status": "pending", "blockedBy": [6]},
-    {"id": 8, "subject": "Task 8: IUniversalDriverBrowser + DiscoveryDriverBrowser core open path", "status": "pending", "blockedBy": [7]},
-    {"id": 9, "subject": "Task 9: UntilStable settle loop (FOCAS)", "status": "pending", "blockedBy": [8], "parallelWith": [11]},
-    {"id": 10, "subject": "Task 10: Capture coalescing + MaxConcurrentCaptures cap", "status": "pending", "blockedBy": [9], "parallelWith": [12]},
-    {"id": 11, "subject": "Task 11: BrowserSessionService universal fallback + CanBrowse", "status": "pending", "blockedBy": [8], "parallelWith": [9]},
-    {"id": 12, "subject": "Task 12: DI registration in AddAdminUI", "status": "pending", "blockedBy": [11], "parallelWith": [10]},
-    {"id": 13, "subject": "Task 13: TagModal -> editor parameter plumbing (DriverType + GetDriverConfigJson)", "status": "pending", "blockedBy": [0], "parallelWith": [1, 2]},
-    {"id": 14, "subject": "Task 14: AbCip picker body universal browse mode", "status": "pending", "blockedBy": [10, 12, 13, 3], "parallelWith": [15, 16]},
-    {"id": 15, "subject": "Task 15: TwinCAT picker body universal browse mode", "status": "pending", "blockedBy": [10, 12, 13, 4], "parallelWith": [14, 16]},
-    {"id": 16, "subject": "Task 16: FOCAS picker body universal browse mode", "status": "pending", "blockedBy": [10, 12, 13, 5], "parallelWith": [14, 15]},
-    {"id": 17, "subject": "Task 17: Full build/test sweep + doc status flip", "status": "pending", "blockedBy": [14, 15, 16]},
-    {"id": 18, "subject": "Task 18: Live /run verify on docker-dev (GATE)", "status": "pending", "blockedBy": [17]}
+    {"id": 0, "subject": "Task 0: Branch setup (feat/universal-discovery-browser)", "status": "completed"},
+    {"id": 1, "subject": "Task 1: ITagDiscovery.SupportsOnlineDiscovery default member", "status": "completed", "blockedBy": [0], "parallelWith": [2, 13]},
+    {"id": 2, "subject": "Task 2: Commons project references (Core.Abstractions)", "status": "completed", "blockedBy": [0], "parallelWith": [1, 13]},
+    {"id": 3, "subject": "Task 3: AbCip opt-in SupportsOnlineDiscovery=true", "status": "completed", "blockedBy": [1], "parallelWith": [4, 5]},
+    {"id": 4, "subject": "Task 4: TwinCAT opt-in SupportsOnlineDiscovery=true", "status": "completed", "blockedBy": [1], "parallelWith": [3, 5]},
+    {"id": 5, "subject": "Task 5: FOCAS opt-in SupportsOnlineDiscovery=true", "status": "completed", "blockedBy": [1], "parallelWith": [3, 4]},
+    {"id": 6, "subject": "Task 6: CapturingAddressSpaceBuilder + captured-tree model", "status": "completed", "blockedBy": [1, 2]},
+    {"id": 7, "subject": "Task 7: CapturedTreeBrowseSession", "status": "completed", "blockedBy": [6]},
+    {"id": 8, "subject": "Task 8: IUniversalDriverBrowser + DiscoveryDriverBrowser core open path", "status": "completed", "blockedBy": [7]},
+    {"id": 9, "subject": "Task 9: UntilStable settle loop (FOCAS)", "status": "completed", "blockedBy": [8], "parallelWith": [11]},
+    {"id": 10, "subject": "Task 10: Capture coalescing + MaxConcurrentCaptures cap", "status": "completed", "blockedBy": [9], "parallelWith": [12]},
+    {"id": 11, "subject": "Task 11: BrowserSessionService universal fallback + CanBrowse", "status": "completed", "blockedBy": [8], "parallelWith": [9]},
+    {"id": 12, "subject": "Task 12: DI registration in AddAdminUI", "status": "completed", "blockedBy": [11], "parallelWith": [10]},
+    {"id": 13, "subject": "Task 13: TagModal -> editor parameter plumbing (DriverType + GetDriverConfigJson)", "status": "completed", "blockedBy": [0], "parallelWith": [1, 2]},
+    {"id": 14, "subject": "Task 14: AbCip picker body universal browse mode", "status": "completed", "blockedBy": [10, 12, 13, 3], "parallelWith": [15, 16]},
+    {"id": 15, "subject": "Task 15: TwinCAT picker body universal browse mode", "status": "completed", "blockedBy": [10, 12, 13, 4], "parallelWith": [14, 16]},
+    {"id": 16, "subject": "Task 16: FOCAS picker body universal browse mode", "status": "completed", "blockedBy": [10, 12, 13, 5], "parallelWith": [14, 15]},
+    {"id": 17, "subject": "Task 17: Full build/test sweep + doc status flip", "status": "completed", "blockedBy": [14, 15, 16]},
+    {"id": 18, "subject": "Task 18: Live /run verify on docker-dev (GATE)", "status": "completed", "blockedBy": [17]}
  ],
  "lastUpdated": "2026-07-15T17:30:00Z"
 }
@@ -0,0 +1,49 @@
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+
+/// <summary>One node captured from a driver's DiscoverAsync stream. Folder ids are
+/// path-composed ("/parent/child"); leaf ids are the driver FullName (the commit value).</summary>
+public sealed class CapturedNode
+{
+    /// <summary>Stable identifier. Folder = path-composed ("/parent/child"); leaf = driver FullName.</summary>
+    public required string Id { get; init; }
+
+    /// <summary>Browse name (the path segment under the parent).</summary>
+    public required string Name { get; init; }
+
+    /// <summary>Human-readable display name.</summary>
+    public required string DisplayName { get; init; }
+
+    /// <summary>True for a variable (terminal); false for a folder.</summary>
+    public required bool IsLeaf { get; init; }
+
+    /// <summary>Driver-side attribute metadata; set only on leaves.</summary>
+    public DriverAttributeInfo? Attribute { get; init; }
+
+    /// <summary>True when the driver marked this leaf as an alarm condition during discovery.</summary>
+    public bool IsAlarmMarked { get; set; }
+
+    /// <summary>Captured child nodes (folders first-or-interleaved in stream order).</summary>
+    public List<CapturedNode> Children { get; } = [];
+
+    /// <summary>Captured static properties attached to this node via AddProperty.</summary>
+    public List<(string Name, DriverDataType Type, object? Value)> Properties { get; } = [];
+}
+
+/// <summary>Immutable-after-Build snapshot of a whole discovery capture. May be shared by
+/// multiple coalesced browse sessions — sessions drop their reference on dispose, never mutate.</summary>
+public sealed class CapturedTree
+{
+    /// <summary>Synthetic root; its Children are the top-level captured nodes.</summary>
+    public required CapturedNode Root { get; init; }
+
+    /// <summary>True when the node cap was hit and recording stopped short.</summary>
+    public required bool Truncated { get; init; }
+
+    /// <summary>Number of nodes actually recorded (bounded by the node cap).</summary>
+    public required int Count { get; init; }
+
+    /// <summary>Flat lookup from node id to node (for O(1) Expand/Attributes serving).</summary>
+    public required IReadOnlyDictionary<string, CapturedNode> ById { get; init; }
+}
@@ -0,0 +1,71 @@
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+
+/// <summary>
+///     Serves a captured discovery snapshot through the standard picker session interface.
+///     No I/O after open; the tree is point-in-time (picker offers Refresh = close + re-open).
+///     The tree may be shared by coalesced sessions — dispose drops only this session's
+///     reference. See design §4.3.
+/// </summary>
+public sealed class CapturedTreeBrowseSession(CapturedTree tree) : IBrowseSession
+{
+    private CapturedTree? _tree = tree;
+
+    /// <inheritdoc />
+    public Guid Token { get; } = Guid.NewGuid();
+
+    /// <inheritdoc />
+    public DateTime LastUsedUtc { get; private set; } = DateTime.UtcNow;
+
+    /// <inheritdoc />
+    public Task<IReadOnlyList<BrowseNode>> RootAsync(CancellationToken cancellationToken)
+    {
+        var t = Tree();
+        var nodes = t.Root.Children.Select(Map).ToList();
+        if (t.Truncated)
+            nodes.Add(new BrowseNode("__truncated__",
+                "⚠ Results truncated — narrow the driver config or use manual entry",
+                BrowseNodeKind.Folder, HasChildrenHint: false));
+        LastUsedUtc = DateTime.UtcNow;
+        return Task.FromResult<IReadOnlyList<BrowseNode>>(nodes);
+    }
+
+    /// <inheritdoc />
+    public Task<IReadOnlyList<BrowseNode>> ExpandAsync(string nodeId, CancellationToken cancellationToken)
+    {
+        var t = Tree();
+        LastUsedUtc = DateTime.UtcNow;
+        return Task.FromResult<IReadOnlyList<BrowseNode>>(
+            t.ById.TryGetValue(nodeId, out var n) ? n.Children.Select(Map).ToList() : []);
+    }
+
+    /// <inheritdoc />
+    public Task<IReadOnlyList<AttributeInfo>> AttributesAsync(string nodeId, CancellationToken cancellationToken)
+    {
+        var t = Tree();
+        LastUsedUtc = DateTime.UtcNow;
+        if (!t.ById.TryGetValue(nodeId, out var n))
+            return Task.FromResult<IReadOnlyList<AttributeInfo>>([]);
+        var attrs = new List<AttributeInfo>();
+        if (n.Attribute is { } a)
+            attrs.Add(new AttributeInfo(n.Name, a.DriverDataType.ToString(), a.IsArray,
+                a.SecurityClass.ToString(), a.IsAlarm || n.IsAlarmMarked));
+        attrs.AddRange(n.Properties.Select(p =>
+            new AttributeInfo(p.Name, p.Type.ToString(), false, "", false)));
+        return Task.FromResult<IReadOnlyList<AttributeInfo>>(attrs);
+    }
+
+    /// <inheritdoc />
+    public ValueTask DisposeAsync()
+    {
+        _tree = null; // drop this session's reference only — tree may be shared (coalescing)
+        return ValueTask.CompletedTask;
+    }
+
+    private CapturedTree Tree() => _tree ?? throw new ObjectDisposedException(nameof(CapturedTreeBrowseSession));
+
+    private static BrowseNode Map(CapturedNode n) => n.IsLeaf
+        ? new BrowseNode(n.Id, n.DisplayName, BrowseNodeKind.Leaf, false)
+        : new BrowseNode(n.Id, n.DisplayName, BrowseNodeKind.Folder, n.Children.Count > 0);
+}
@@ -0,0 +1,112 @@
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+
+/// <summary>
+///     In-memory <see cref="IAddressSpaceBuilder"/> that records the streamed discovery tree
+///     for the universal browser instead of materializing OPC UA nodes. Single-threaded like
+///     every builder a driver streams into during DiscoverAsync. Enforces a node cap: once
+///     exceeded it stops recording (drivers keep streaming harmlessly) and marks the tree
+///     truncated. See docs/plans/2026-07-15-universal-discovery-browser-design.md §4.1.
+/// </summary>
+public sealed class CapturingAddressSpaceBuilder : IAddressSpaceBuilder
+{
+    private sealed class CaptureState(int nodeCap)
+    {
+        public int Count;
+        public bool Truncated;
+        public readonly int NodeCap = nodeCap;
+        public readonly Dictionary<string, CapturedNode> ById = new(StringComparer.Ordinal);
+        public bool TryReserve()
+        {
+            if (Count >= NodeCap) { Truncated = true; return false; }
+            Count++;
+            return true;
+        }
+    }
+
+    private readonly CaptureState _state;
+    private readonly CapturedNode _scope;
+
+    /// <summary>Create a root capturing builder with the given node cap (default 50 000).</summary>
+    /// <param name="nodeCap">Maximum number of nodes recorded before the tree is marked truncated.</param>
+    public CapturingAddressSpaceBuilder(int nodeCap = 50_000)
+    {
+        _state = new CaptureState(nodeCap);
+        _scope = new CapturedNode { Id = "", Name = "", DisplayName = "", IsLeaf = false };
+    }
+
+    private CapturingAddressSpaceBuilder(CaptureState state, CapturedNode scope)
+    {
+        _state = state;
+        _scope = scope;
+    }
+
+    /// <inheritdoc />
+    public IAddressSpaceBuilder Folder(string browseName, string displayName)
+    {
+        var node = new CapturedNode
+        {
+            Id = _scope.Id + "/" + browseName,
+            Name = browseName,
+            DisplayName = displayName,
+            IsLeaf = false,
+        };
+        if (_state.TryReserve())
+        {
+            _scope.Children.Add(node);
+            _state.ById.TryAdd(node.Id, node);
+        }
+        // Over cap: the child builder writes into a detached node — recording stops, streaming doesn't break.
+        return new CapturingAddressSpaceBuilder(_state, node);
+    }
+
+    /// <inheritdoc />
+    public IVariableHandle Variable(string browseName, string displayName, DriverAttributeInfo attributeInfo)
+    {
+        var node = new CapturedNode
+        {
+            Id = attributeInfo.FullName,
+            Name = browseName,
+            DisplayName = displayName,
+            IsLeaf = true,
+            Attribute = attributeInfo,
+        };
+        if (_state.TryReserve())
+        {
+            _scope.Children.Add(node);
+            _state.ById.TryAdd(node.Id, node);
+        }
+        return new CapturedVariableHandle(node);
+    }
+
+    /// <inheritdoc />
+    public void AddProperty(string browseName, DriverDataType dataType, object? value) =>
+        _scope.Properties.Add((browseName, dataType, value));
+
+    /// <summary>Snapshot the captured tree. Only valid on the root builder (the one the browser constructed).</summary>
+    /// <returns>An immutable-after-build <see cref="CapturedTree"/>.</returns>
+    public CapturedTree Build() => new()
+    {
+        Root = _scope,
+        Truncated = _state.Truncated,
+        Count = _state.Count,
+        ById = _state.ById,
+    };
+
+    private sealed class CapturedVariableHandle(CapturedNode node) : IVariableHandle
+    {
+        public string FullReference => node.Id;
+        public IAlarmConditionSink MarkAsAlarmCondition(AlarmConditionInfo info)
+        {
+            node.IsAlarmMarked = true;
+            return NoopAlarmSink.Instance;
+        }
+    }
+
+    private sealed class NoopAlarmSink : IAlarmConditionSink
+    {
+        public static readonly NoopAlarmSink Instance = new();
+        public void OnTransition(AlarmEventArgs args) { } // browse never delivers live transitions
+    }
+}
@@ -0,0 +1,215 @@
+using System.Collections.Concurrent;
+using System.Text.Json.Nodes;
+using Microsoft.Extensions.Logging;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+
+/// <summary>See docs/plans/2026-07-15-universal-discovery-browser-design.md §4.2.</summary>
+public sealed class DiscoveryDriverBrowser : IUniversalDriverBrowser
+{
+    /// <summary>Whole-open bound: construct + connect + discover (+ settle). Separate from the
+    /// 20 s per-call browse timeout, which only covers serving from memory.</summary>
+    public static readonly TimeSpan OpenTimeout = TimeSpan.FromSeconds(60);
+
+    /// <summary>Bound on the cleanup ShutdownAsync (R2-01: no unbounded waits — a driver wedged
+    /// in discovery may be equally wedged in shutdown).</summary>
+    public static readonly TimeSpan ShutdownTimeout = TimeSpan.FromSeconds(10);
+
+    /// <summary>Node-count cap the capturing builder enforces before marking the tree truncated.</summary>
+    public const int NodeCap = 50_000;
+
+    /// <summary>Global cap on simultaneous captures (§4.2). Coalesced awaiters don't hold a slot.</summary>
+    public const int MaxConcurrentCaptures = 4;
+
+    /// <summary>Per-type declarative config patch guaranteeing browse mode at open time (§5.1).
+    /// A dictionary entry per config-gated driver — not code.</summary>
+    internal static readonly IReadOnlyDictionary<string, string> BrowsePatches =
+        new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase)
+        {
+            ["AbCip"]   = """{ "EnableControllerBrowse": true }""",
+            ["TwinCAT"] = """{ "EnableControllerBrowse": true }""",
+            ["FOCAS"]   = """{ "FixedTree": { "Enabled": true } }""",
+            // OpcUaClient/BACnet/MTConnect: no patch — their discovery is unconditional.
+        };
+
+    private readonly IDriverFactory _driverFactory;
+    private readonly ILogger<DiscoveryDriverBrowser> _logger;
+    private readonly TimeSpan _openTimeout;
+    private readonly TimeSpan _shutdownTimeout;
+    private readonly ConcurrentDictionary<string, Lazy<Task<CapturedTree>>> _inflight = new();
+    private readonly SemaphoreSlim _captureSlots = new(MaxConcurrentCaptures, MaxConcurrentCaptures);
+
+    /// <summary>Production constructor: standard open + shutdown bounds.</summary>
+    /// <param name="driverFactory">Factory used to construct throwaway/capture driver instances.</param>
+    /// <param name="logger">Logger for shutdown-timeout warnings.</param>
+    public DiscoveryDriverBrowser(IDriverFactory driverFactory, ILogger<DiscoveryDriverBrowser> logger)
+        : this(driverFactory, logger, OpenTimeout, ShutdownTimeout) { }
+
+    // Test seam: short timeouts.
+    internal DiscoveryDriverBrowser(IDriverFactory driverFactory, ILogger<DiscoveryDriverBrowser> logger,
+        TimeSpan openTimeout, TimeSpan shutdownTimeout)
+    {
+        _driverFactory = driverFactory;
+        _logger = logger;
+        _openTimeout = openTimeout;
+        _shutdownTimeout = shutdownTimeout;
+    }
+
+    /// <inheritdoc />
+    public bool CanBrowse(string driverType, string configJson)
+    {
+        IDriver? probe = null;
+        try
+        {
+            probe = _driverFactory.TryCreate(driverType, $"browse-can-{Guid.NewGuid():N}",
+                PatchForBrowse(driverType, configJson));
+            return probe is ITagDiscovery { SupportsOnlineDiscovery: true };
+        }
+        catch
+        {
+            // TryCreate parses configJson and can throw on mid-authoring JSON. UI affordance
+            // gate — must never throw into the page (§4.2).
+            return false;
+        }
+        finally
+        {
+            if (probe is not null) _ = BoundedShutdownAsync(probe, driverType); // best-effort, never leak
+        }
+    }
+
+    /// <inheritdoc />
+    public async Task<IBrowseSession> OpenAsync(string driverType, string configJson, CancellationToken ct)
+    {
+        var key = CaptureKey(driverType, configJson);
+        // Lazy: exactly one RunCaptureAsync per key even under GetOrAdd races.
+        var capture = _inflight.GetOrAdd(key,
+            _ => new Lazy<Task<CapturedTree>>(() => RunCaptureAsync(key, driverType, configJson)));
+        // The shared capture runs independent of any single caller (its own OpenTimeout bounds it);
+        // each caller — including a queued one — observes ITS OWN ct via WaitAsync.
+        var tree = await capture.Value.WaitAsync(ct).ConfigureAwait(false);
+        return new CapturedTreeBrowseSession(tree);
+    }
+
+    private async Task<CapturedTree> RunCaptureAsync(string key, string driverType, string configJson)
+    {
+        try
+        {
+            await _captureSlots.WaitAsync().ConfigureAwait(false); // FIFO-ish queue for a slot
+            try
+            {
+                return await CaptureAsync(driverType, configJson, CancellationToken.None).ConfigureAwait(false);
+            }
+            finally
+            {
+                _captureSlots.Release();
+            }
+        }
+        finally
+        {
+            _inflight.TryRemove(key, out _); // in-flight only — no result caching (Refresh = fresh capture)
+        }
+    }
+
+    internal static string CaptureKey(string driverType, string configJson) =>
+        driverType.ToLowerInvariant() + ":" +
+        Convert.ToHexString(System.Security.Cryptography.SHA256.HashData(
+            System.Text.Encoding.UTF8.GetBytes(configJson ?? "")));
+
+    private async Task<CapturedTree> CaptureAsync(string driverType, string configJson, CancellationToken ct)
+    {
+        var patched = PatchForBrowse(driverType, configJson);
+        var driver = _driverFactory.TryCreate(driverType, $"browse-{Guid.NewGuid():N}", patched)
+            ?? throw new InvalidOperationException(
+                $"Driver type '{driverType}' is not available in this host.");
+        try
+        {
+            if (driver is not ITagDiscovery disc || !disc.SupportsOnlineDiscovery)
+                throw new InvalidOperationException(
+                    $"Driver type '{driverType}' has no online discovery — author tags manually.");
+
+            using var openCts = CancellationTokenSource.CreateLinkedTokenSource(ct);
+            openCts.CancelAfter(_openTimeout);
+
+            await driver.InitializeAsync(patched, openCts.Token).ConfigureAwait(false);
+            return await DiscoverTreeAsync(disc, driverType, openCts.Token).ConfigureAwait(false);
+        }
+        finally
+        {
+            await BoundedShutdownAsync(driver, driverType).ConfigureAwait(false);
+        }
+    }
+
+    private static readonly TimeSpan SettleInterval = TimeSpan.FromSeconds(1);
+
+    private async Task<CapturedTree> DiscoverTreeAsync(ITagDiscovery disc, string driverType, CancellationToken ct)
+    {
+        if (disc.RediscoverPolicy != DiscoveryRediscoverPolicy.UntilStable)
+        {
+            var builder = new CapturingAddressSpaceBuilder(NodeCap);
+#pragma warning disable OTOPCUA0001 // One-shot browse capture, NOT a runtime dispatch path: the driver is a throwaway instance we construct/connect/discover/discard for the picker. CapabilityInvoker (retry/breaker/telemetry) governs live polling, not this admin-side capture.
+            await disc.DiscoverAsync(builder, ct).ConfigureAwait(false);
+#pragma warning restore OTOPCUA0001
+            return builder.Build();
+        }
+
+        // UntilStable (FOCAS): the discovered shape fills in asynchronously after connect —
+        // re-capture until non-empty and stable across two consecutive passes, bounded by the
+        // open-timeout. Mirrors the deploy-time contract in DriverInstanceActor.
+        CapturedTree? previous = null;
+        while (true)
+        {
+            var builder = new CapturingAddressSpaceBuilder(NodeCap);
+            try
+            {
+#pragma warning disable OTOPCUA0001 // One-shot browse capture, NOT a runtime dispatch path (see above).
+                await disc.DiscoverAsync(builder, ct).ConfigureAwait(false);
+#pragma warning restore OTOPCUA0001
+                var current = builder.Build();
+                if (current.Count > 0 && previous?.Count == current.Count) return current;
+                previous = current;
+                await Task.Delay(SettleInterval, ct).ConfigureAwait(false);
+            }
+            catch (OperationCanceledException) when (previous is { Count: > 0 })
+            {
+                _logger.LogWarning(
+                    "UntilStable settle for {DriverType} hit the open-timeout before stabilising; returning the last capture ({Count} nodes)",
+                    driverType, previous.Count);
+                return previous; // best effort: a fresh-but-unsettled tree beats a failed open
+            }
+        }
+    }
+
+    private async Task BoundedShutdownAsync(IDriver driver, string driverType)
+    {
+        try
+        {
+            using var cts = new CancellationTokenSource(_shutdownTimeout);
+            // WaitAsync: a token-ignoring wedged driver is ABANDONED (dropped), never awaited forever.
+            await driver.ShutdownAsync(cts.Token).WaitAsync(cts.Token).ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogWarning(ex,
+                "Browse-capture shutdown for {DriverType} failed/timed out; instance abandoned", driverType);
+        }
+    }
+
+    internal static string PatchForBrowse(string driverType, string configJson)
+    {
+        if (!BrowsePatches.TryGetValue(driverType, out var patch)) return configJson;
+        var config = JsonNode.Parse(string.IsNullOrWhiteSpace(configJson) ? "{}" : configJson)
+            ?.AsObject() ?? new JsonObject();
+        Merge(config, JsonNode.Parse(patch)!.AsObject());
+        return config.ToJsonString();
+    }
+
+    private static void Merge(JsonObject target, JsonObject patch)
+    {
+        foreach (var (key, value) in patch)
+        {
+            if (value is JsonObject po && target[key] is JsonObject to) Merge(to, po);
+            else target[key] = value?.DeepClone();
+        }
+    }
+}
@@ -0,0 +1,28 @@
+namespace ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+
+/// <summary>
+///     Universal fallback browser: captures any discovery-capable driver's DiscoverAsync
+///     output and serves it as a browse session. Resolved by BrowserSessionService only
+///     when no bespoke IDriverBrowser matches the driver type (bespoke-first). A separate
+///     interface — NOT an IDriverBrowser — because BrowserSessionService indexes those
+///     ToDictionary-by-DriverType and the universal browser has no single type.
+/// </summary>
+public interface IUniversalDriverBrowser
+{
+    /// <summary>Cheap gate (construct + inspect, no connect): can this driver type + config be
+    /// browsed? Never throws. Drives the picker's Browse-button visibility.</summary>
+    /// <param name="driverType">The driver type name.</param>
+    /// <param name="configJson">The authoring DriverConfig JSON (may be mid-edit / malformed).</param>
+    /// <returns>True when a discovery-capable driver can be constructed for this type + config.</returns>
+    bool CanBrowse(string driverType, string configJson);
+
+    /// <summary>Construct the driver (with the per-type browse patch), connect, capture one
+    /// full discovery pass (with UntilStable settle), shut the driver down (bounded), and
+    /// return a session over the captured snapshot. Throws on failure — the caller
+    /// (BrowserSessionService) converts to BrowseOpenResult.</summary>
+    /// <param name="driverType">The driver type name.</param>
+    /// <param name="configJson">The DriverConfig JSON to connect with.</param>
+    /// <param name="ct">Cancellation token for the caller's open request.</param>
+    /// <returns>A browse session over the captured discovery snapshot.</returns>
+    Task<IBrowseSession> OpenAsync(string driverType, string configJson, CancellationToken ct);
+}
@@ -7,7 +7,16 @@

    <ItemGroup>
        <PackageReference Include="Akka"/>
+        <PackageReference Include="Microsoft.Extensions.Logging.Abstractions"/>
        <PackageReference Include="ZB.MOM.WW.Audit"/>
    </ItemGroup>

+    <ItemGroup>
+        <ProjectReference Include="..\ZB.MOM.WW.OtOpcUa.Core.Abstractions\ZB.MOM.WW.OtOpcUa.Core.Abstractions.csproj"/>
+    </ItemGroup>
+
+    <ItemGroup>
+        <InternalsVisibleTo Include="ZB.MOM.WW.OtOpcUa.Commons.Tests"/>
+    </ItemGroup>
+
 </Project>
@@ -30,4 +30,12 @@ public interface ITagDiscovery

    /// <summary>Post-connect re-discovery policy. Default preserves the original retry-until-stable behavior.</summary>
    DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.UntilStable;
+
+    /// <summary>
+    ///     True when <see cref="DiscoverAsync"/> enumerates the tag set from the live backend
+    ///     (browsable by the universal discovery browser), rather than replaying
+    ///     pre-declared/authored tags. Default false — flat-address drivers stay manual-entry.
+    ///     See docs/plans/2026-07-15-universal-discovery-browser-design.md §5.
+    /// </summary>
+    bool SupportsOnlineDiscovery => false;
 }
@@ -999,6 +999,10 @@ public sealed class AbCipDriver : IDriver, IReadable, IWritable, ITagDiscovery,
    /// <inheritdoc />
    public DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.Once;

+    /// <summary>Controller enumeration is real (CIP Symbol Object walk) — config-gated on
+    /// EnableControllerBrowse, which the universal browser's PatchForBrowse guarantees at open time.</summary>
+    public bool SupportsOnlineDiscovery => true;
+
    /// <inheritdoc />
    public async Task DiscoverAsync(IAddressSpaceBuilder builder, CancellationToken cancellationToken)
    {
@@ -427,6 +427,12 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
    // node set is non-empty and stable.
    public DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.UntilStable;

+    /// <summary>The FixedTree device folder is real enumeration — config-gated on FixedTree.Enabled,
+    /// which the universal browser's PatchForBrowse turns on. FOCAS is the UntilStable driver: the
+    /// FixedTree cache fills a couple of seconds post-connect, so the browser's settle loop re-captures
+    /// until the node set is non-empty and stable.</summary>
+    public bool SupportsOnlineDiscovery => true;
+
    /// <inheritdoc />
    public Task DiscoverAsync(IAddressSpaceBuilder builder, CancellationToken cancellationToken)
    {
@@ -380,6 +380,10 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
    // discovery pass is sufficient.
    public DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.Once;

+    /// <summary>ADS symbol upload is real device enumeration — config-gated on
+    /// EnableControllerBrowse, which the universal browser's PatchForBrowse guarantees at open time.</summary>
+    public bool SupportsOnlineDiscovery => true;
+
    /// <inheritdoc />
    public async Task DiscoverAsync(IAddressSpaceBuilder builder, CancellationToken cancellationToken)
    {
@@ -13,7 +13,8 @@ namespace ZB.MOM.WW.OtOpcUa.AdminUI.Browsing;
 public sealed class BrowserSessionService(
    IEnumerable<IDriverBrowser> browsers,
    BrowseSessionRegistry registry,
-    ILogger<BrowserSessionService> logger) : IBrowserSessionService
+    ILogger<BrowserSessionService> logger,
+    IUniversalDriverBrowser universalBrowser) : IBrowserSessionService
 {
    /// <summary>Upper bound on a single root/expand/attributes call.</summary>
    public static readonly TimeSpan PerCallTimeout = TimeSpan.FromSeconds(20);
@@ -25,7 +26,7 @@ public sealed class BrowserSessionService(
    public async Task<BrowseOpenResult> OpenAsync(string driverType, string configJson, CancellationToken ct)
    {
        if (!_browsersByType.TryGetValue(driverType, out var browser))
-            return new(false, $"No browser registered for driver type '{driverType}'.", Guid.Empty);
+            return await OpenUniversalAsync(driverType, configJson, ct).ConfigureAwait(false);
        try
        {
            var session = await browser.OpenAsync(configJson, ct).ConfigureAwait(false);
@@ -40,6 +41,28 @@ public sealed class BrowserSessionService(
        }
    }

+    /// <inheritdoc />
+    public bool CanBrowse(string driverType, string configJson) =>
+        _browsersByType.ContainsKey(driverType) || universalBrowser.CanBrowse(driverType, configJson);
+
+    private async Task<BrowseOpenResult> OpenUniversalAsync(string driverType, string configJson, CancellationToken ct)
+    {
+        if (!universalBrowser.CanBrowse(driverType, configJson))
+            return new(false, $"No browser registered for driver type '{driverType}'.", Guid.Empty);
+        try
+        {
+            var session = await universalBrowser.OpenAsync(driverType, configJson, ct).ConfigureAwait(false);
+            registry.Register(session);
+            return new(true, null, session.Token);
+        }
+        catch (Exception ex)
+        {
+            logger.LogInformation(ex,
+                "Universal browse open failed for driverType={DriverType}: {Message}", driverType, ex.Message);
+            return new(false, ex.Message, Guid.Empty);
+        }
+    }
+
    /// <inheritdoc />
    public Task<IReadOnlyList<BrowseNode>> RootAsync(Guid token, CancellationToken ct) =>
        InvokeAsync(token, ct, (s, c) => s.RootAsync(c));
@@ -54,6 +54,14 @@ public interface IBrowserSessionService
    /// <param name="token">Registry handle for the browse session to close.</param>
    /// <returns>A task that represents the asynchronous operation.</returns>
    Task CloseAsync(Guid token);
+
+    /// <summary>True when a browse affordance exists for this driver type: a bespoke browser
+    /// is registered, or the universal browser can serve it. Cheap (no connect); never throws.
+    /// Drives the picker's Browse-button visibility.</summary>
+    /// <param name="driverType">The driver type name.</param>
+    /// <param name="configJson">The authoring DriverConfig JSON (may be mid-edit).</param>
+    /// <returns>True when the picker should offer a Browse affordance for this driver.</returns>
+    bool CanBrowse(string driverType, string configJson);
 }

 /// <summary>
@@ -1,4 +1,14 @@
-@* Static AB CIP address builder: tag name + optional element index → tag[idx] or tag *@
+@* AB CIP address picker:
+     1. Static tag name + optional element index → tag[idx] or tag (always available).
+     2. (DriverOperator-gated, when the driver supports online discovery) Browse the controller
+        symbol tree captured by the universal DiscoveryDriverBrowser. *@
+@implements IAsyncDisposable
+@using Microsoft.AspNetCore.Authorization
+@using ZB.MOM.WW.OtOpcUa.AdminUI.Browsing
+@using ZB.MOM.WW.OtOpcUa.Commons.Browsing
+@inject IBrowserSessionService BrowserService
+@inject AuthenticationStateProvider AuthState
+@inject IAuthorizationService AuthorizationService

 <div class="row g-3">
    <div class="col-md-6">
@@ -22,6 +32,42 @@
    </div>
 </div>

+@if (_canBrowse)
+{
+    <div class="mt-3 d-flex align-items-center gap-2">
+        @if (_token == Guid.Empty)
+        {
+            <button type="button" class="btn btn-outline-primary btn-sm"
+                    disabled="@_opening" @onclick="OpenBrowseAsync">
+                @if (_opening) { <span class="spinner-border spinner-border-sm me-1"></span> }
+                Browse controller
+            </button>
+        }
+        else
+        {
+            <span class="chip chip-ok">Browser open</span>
+            <button type="button" class="btn btn-outline-secondary btn-sm"
+                    disabled="@_opening" @onclick="RefreshBrowseAsync">
+                @if (_opening) { <span class="spinner-border spinner-border-sm me-1"></span> }
+                Refresh
+            </button>
+            <button type="button" class="btn btn-outline-secondary btn-sm" @onclick="CloseBrowseAsync">
+                Close
+            </button>
+        }
+        @if (_openError is not null) { <span class="chip chip-bad" title="@_openError">@TruncatedError()</span> }
+    </div>
+
+    @if (_token != Guid.Empty)
+    {
+        <div class="mt-2">
+            <div class="form-text mb-1">Snapshot taken at open/refresh time — click Refresh to re-read the controller.</div>
+            <DriverBrowseTree SessionToken="_token" OnNodeSelected="OnTreeSelectAsync"
+                              SelectedNodeId="@_tagName" />
+        </div>
+    }
+}
+
 <div class="mt-3">
    <span class="text-muted small">Result:</span>
    <code class="mono ms-2">@_built</code>
@@ -30,16 +76,63 @@
@code {
    [Parameter] public string CurrentAddress { get; set; } = "";
    [Parameter] public EventCallback<string> CurrentAddressChanged { get; set; }
+    /// <summary>Driver type used to open a universal browse session (defaults to AbCip).</summary>
+    [Parameter] public string DriverType { get; set; } = "AbCip";
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetConfigJson { get; set; } = () => "{}";

    private string _tagName = "";
    private int _elementIndex = 0;
    private bool _useIndex = false;
    private string _built = "";

-    protected override void OnInitialized()
+    private Guid _token = Guid.Empty;
+    private bool _opening;
+    private bool _canBrowse;
+    private string? _openError;
+
+    protected override async Task OnInitializedAsync()
    {
+        var auth = await AuthState.GetAuthenticationStateAsync();
+        var authResult = await AuthorizationService.AuthorizeAsync(auth.User, null, AdminUiPolicies.DriverOperator);
+        // CanBrowse constructs a throwaway driver — evaluate once, not per render.
+        _canBrowse = authResult.Succeeded && BrowserService.CanBrowse(DriverType, GetConfigJson() ?? "{}");
        _built = Build();
-        _ = CurrentAddressChanged.InvokeAsync(_built);
+        await CurrentAddressChanged.InvokeAsync(_built);
+    }
+
+    private async Task OpenBrowseAsync()
+    {
+        _opening = true; _openError = null; StateHasChanged();
+        try
+        {
+            var json = GetConfigJson() ?? "{}";
+            var result = await BrowserService.OpenAsync(DriverType, json, default);
+            if (result.Ok) _token = result.Token;
+            else _openError = result.Message;
+        }
+        finally { _opening = false; StateHasChanged(); }
+    }
+
+    private async Task RefreshBrowseAsync()
+    {
+        await CloseBrowseAsync();
+        await OpenBrowseAsync();
+    }
+
+    private async Task CloseBrowseAsync()
+    {
+        var t = _token; _token = Guid.Empty; StateHasChanged();
+        if (t != Guid.Empty) await BrowserService.CloseAsync(t);
+    }
+
+    private async Task OnTreeSelectAsync(BrowseNode node)
+    {
+        // Folders fire the same callback — commit only on a leaf (the captured NodeId is the CIP tag path).
+        if (node.Kind != BrowseNodeKind.Leaf) return;
+        _tagName = node.NodeId;
+        _useIndex = false;
+        await OnChangedAsync();
    }

    private async Task OnChangedAsync()
@@ -54,4 +147,17 @@
            return "";
        return _useIndex ? $"{_tagName}[{_elementIndex}]" : _tagName;
    }
+
+    private string TruncatedError() =>
+        _openError is null ? "" : (_openError.Length > 60 ? _openError[..60] + "…" : _openError);
+
+    public ValueTask DisposeAsync()
+    {
+        if (_token != Guid.Empty)
+        {
+            // Fire-and-forget — don't block circuit teardown on a slow capture.
+            _ = BrowserService.CloseAsync(_token);
+        }
+        return ValueTask.CompletedTask;
+    }
 }
@@ -1,5 +1,17 @@
-@* Static FOCAS address builder: parameter group + parameter ID → axis:5 *@
+@* FOCAS address picker:
+     1. Static parameter group + parameter ID → axis:5 (always available).
+     2. (DriverOperator-gated, when the driver supports online discovery) Browse the FixedTree
+        device model captured by the universal DiscoveryDriverBrowser. FOCAS opens take a few
+        seconds longer than other drivers — its FixedTree cache fills post-connect and the browser
+        runs an UntilStable settle loop; the _opening spinner covers the wait. *@
+@implements IAsyncDisposable
+@using Microsoft.AspNetCore.Authorization
+@using ZB.MOM.WW.OtOpcUa.AdminUI.Browsing
@using ZB.MOM.WW.OtOpcUa.AdminUI.Components.Shared.Drivers.Pickers
+@using ZB.MOM.WW.OtOpcUa.Commons.Browsing
+@inject IBrowserSessionService BrowserService
+@inject AuthenticationStateProvider AuthState
+@inject IAuthorizationService AuthorizationService

 <div class="row g-3">
    <div class="col-md-4">
@@ -18,6 +30,42 @@
    </div>
 </div>

+@if (_canBrowse)
+{
+    <div class="mt-3 d-flex align-items-center gap-2">
+        @if (_token == Guid.Empty)
+        {
+            <button type="button" class="btn btn-outline-primary btn-sm"
+                    disabled="@_opening" @onclick="OpenBrowseAsync">
+                @if (_opening) { <span class="spinner-border spinner-border-sm me-1"></span> }
+                Browse machine
+            </button>
+        }
+        else
+        {
+            <span class="chip chip-ok">Browser open</span>
+            <button type="button" class="btn btn-outline-secondary btn-sm"
+                    disabled="@_opening" @onclick="RefreshBrowseAsync">
+                @if (_opening) { <span class="spinner-border spinner-border-sm me-1"></span> }
+                Refresh
+            </button>
+            <button type="button" class="btn btn-outline-secondary btn-sm" @onclick="CloseBrowseAsync">
+                Close
+            </button>
+        }
+        @if (_openError is not null) { <span class="chip chip-bad" title="@_openError">@TruncatedError()</span> }
+    </div>
+
+    @if (_token != Guid.Empty)
+    {
+        <div class="mt-2">
+            <div class="form-text mb-1">Snapshot taken at open/refresh time — click Refresh to re-read the machine.</div>
+            <DriverBrowseTree SessionToken="_token" OnNodeSelected="OnTreeSelectAsync"
+                              SelectedNodeId="@_built" />
+        </div>
+    }
+}
+
 <div class="mt-3">
    <span class="text-muted small">Result:</span>
    <code class="mono ms-2">@_built</code>
@@ -26,15 +74,63 @@
@code {
    [Parameter] public string CurrentAddress { get; set; } = "";
    [Parameter] public EventCallback<string> CurrentAddressChanged { get; set; }
+    /// <summary>Driver type used to open a universal browse session (defaults to FOCAS).</summary>
+    [Parameter] public string DriverType { get; set; } = "FOCAS";
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetConfigJson { get; set; } = () => "{}";

    private string _group = "axis";
    private int _parameterId = 0;
    private string _built = "";

-    protected override void OnInitialized()
+    private Guid _token = Guid.Empty;
+    private bool _opening;
+    private bool _canBrowse;
+    private string? _openError;
+
+    protected override async Task OnInitializedAsync()
    {
+        var auth = await AuthState.GetAuthenticationStateAsync();
+        var authResult = await AuthorizationService.AuthorizeAsync(auth.User, null, AdminUiPolicies.DriverOperator);
+        // CanBrowse constructs a throwaway driver — evaluate once, not per render.
+        _canBrowse = authResult.Succeeded && BrowserService.CanBrowse(DriverType, GetConfigJson() ?? "{}");
        _built = FocasAddressBuilder.Build(_group, _parameterId);
-        _ = CurrentAddressChanged.InvokeAsync(_built);
+        await CurrentAddressChanged.InvokeAsync(_built);
+    }
+
+    private async Task OpenBrowseAsync()
+    {
+        _opening = true; _openError = null; StateHasChanged();
+        try
+        {
+            var json = GetConfigJson() ?? "{}";
+            var result = await BrowserService.OpenAsync(DriverType, json, default);
+            if (result.Ok) _token = result.Token;
+            else _openError = result.Message;
+        }
+        finally { _opening = false; StateHasChanged(); }
+    }
+
+    private async Task RefreshBrowseAsync()
+    {
+        await CloseBrowseAsync();
+        await OpenBrowseAsync();
+    }
+
+    private async Task CloseBrowseAsync()
+    {
+        var t = _token; _token = Guid.Empty; StateHasChanged();
+        if (t != Guid.Empty) await BrowserService.CloseAsync(t);
+    }
+
+    private async Task OnTreeSelectAsync(BrowseNode node)
+    {
+        // Folders fire the same callback — commit only on a leaf. The captured NodeId is the
+        // driver FullName (FixedTree address), which the group/id builder cannot reconstruct, so
+        // commit it directly rather than through OnChangedAsync.
+        if (node.Kind != BrowseNodeKind.Leaf) return;
+        _built = node.NodeId;
+        await CurrentAddressChanged.InvokeAsync(_built);
    }

    private async Task OnChangedAsync()
@@ -42,4 +138,17 @@
        _built = FocasAddressBuilder.Build(_group, _parameterId);
        await CurrentAddressChanged.InvokeAsync(_built);
    }
+
+    private string TruncatedError() =>
+        _openError is null ? "" : (_openError.Length > 60 ? _openError[..60] + "…" : _openError);
+
+    public ValueTask DisposeAsync()
+    {
+        if (_token != Guid.Empty)
+        {
+            // Fire-and-forget — don't block circuit teardown on a slow capture.
+            _ = BrowserService.CloseAsync(_token);
+        }
+        return ValueTask.CompletedTask;
+    }
 }
@@ -1,4 +1,14 @@
-@* Static TwinCAT address builder: ADS variable name (free text) → verbatim *@
+@* TwinCAT address picker:
+     1. Static ADS variable name (free text) → verbatim (always available).
+     2. (DriverOperator-gated, when the driver supports online discovery) Browse the ADS symbol
+        tree captured by the universal DiscoveryDriverBrowser. *@
+@implements IAsyncDisposable
+@using Microsoft.AspNetCore.Authorization
+@using ZB.MOM.WW.OtOpcUa.AdminUI.Browsing
+@using ZB.MOM.WW.OtOpcUa.Commons.Browsing
+@inject IBrowserSessionService BrowserService
+@inject AuthenticationStateProvider AuthState
+@inject IAuthorizationService AuthorizationService

 <div class="row g-3">
    <div class="col-md-8">
@@ -11,6 +21,42 @@
    </div>
 </div>

+@if (_canBrowse)
+{
+    <div class="mt-3 d-flex align-items-center gap-2">
+        @if (_token == Guid.Empty)
+        {
+            <button type="button" class="btn btn-outline-primary btn-sm"
+                    disabled="@_opening" @onclick="OpenBrowseAsync">
+                @if (_opening) { <span class="spinner-border spinner-border-sm me-1"></span> }
+                Browse controller
+            </button>
+        }
+        else
+        {
+            <span class="chip chip-ok">Browser open</span>
+            <button type="button" class="btn btn-outline-secondary btn-sm"
+                    disabled="@_opening" @onclick="RefreshBrowseAsync">
+                @if (_opening) { <span class="spinner-border spinner-border-sm me-1"></span> }
+                Refresh
+            </button>
+            <button type="button" class="btn btn-outline-secondary btn-sm" @onclick="CloseBrowseAsync">
+                Close
+            </button>
+        }
+        @if (_openError is not null) { <span class="chip chip-bad" title="@_openError">@TruncatedError()</span> }
+    </div>
+
+    @if (_token != Guid.Empty)
+    {
+        <div class="mt-2">
+            <div class="form-text mb-1">Snapshot taken at open/refresh time — click Refresh to re-read the controller.</div>
+            <DriverBrowseTree SessionToken="_token" OnNodeSelected="OnTreeSelectAsync"
+                              SelectedNodeId="@_varName" />
+        </div>
+    }
+}
+
 <div class="mt-3">
    <span class="text-muted small">Result:</span>
    <code class="mono ms-2">@_built</code>
@@ -19,14 +65,60 @@
@code {
    [Parameter] public string CurrentAddress { get; set; } = "";
    [Parameter] public EventCallback<string> CurrentAddressChanged { get; set; }
+    /// <summary>Driver type used to open a universal browse session (defaults to TwinCAT).</summary>
+    [Parameter] public string DriverType { get; set; } = "TwinCAT";
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetConfigJson { get; set; } = () => "{}";

    private string _varName = "";
    private string _built = "";

-    protected override void OnInitialized()
+    private Guid _token = Guid.Empty;
+    private bool _opening;
+    private bool _canBrowse;
+    private string? _openError;
+
+    protected override async Task OnInitializedAsync()
    {
+        var auth = await AuthState.GetAuthenticationStateAsync();
+        var authResult = await AuthorizationService.AuthorizeAsync(auth.User, null, AdminUiPolicies.DriverOperator);
+        // CanBrowse constructs a throwaway driver — evaluate once, not per render.
+        _canBrowse = authResult.Succeeded && BrowserService.CanBrowse(DriverType, GetConfigJson() ?? "{}");
        _built = _varName;
-        _ = CurrentAddressChanged.InvokeAsync(_built);
+        await CurrentAddressChanged.InvokeAsync(_built);
+    }
+
+    private async Task OpenBrowseAsync()
+    {
+        _opening = true; _openError = null; StateHasChanged();
+        try
+        {
+            var json = GetConfigJson() ?? "{}";
+            var result = await BrowserService.OpenAsync(DriverType, json, default);
+            if (result.Ok) _token = result.Token;
+            else _openError = result.Message;
+        }
+        finally { _opening = false; StateHasChanged(); }
+    }
+
+    private async Task RefreshBrowseAsync()
+    {
+        await CloseBrowseAsync();
+        await OpenBrowseAsync();
+    }
+
+    private async Task CloseBrowseAsync()
+    {
+        var t = _token; _token = Guid.Empty; StateHasChanged();
+        if (t != Guid.Empty) await BrowserService.CloseAsync(t);
+    }
+
+    private async Task OnTreeSelectAsync(BrowseNode node)
+    {
+        // Folders fire the same callback — commit only on a leaf (the captured NodeId is the ADS symbol path).
+        if (node.Kind != BrowseNodeKind.Leaf) return;
+        _varName = node.NodeId;
+        await OnChangedAsync();
    }

    private async Task OnChangedAsync()
@@ -34,4 +126,17 @@
        _built = _varName;
        await CurrentAddressChanged.InvokeAsync(_built);
    }
+
+    private string TruncatedError() =>
+        _openError is null ? "" : (_openError.Length > 60 ? _openError[..60] + "…" : _openError);
+
+    public ValueTask DisposeAsync()
+    {
+        if (_token != Guid.Empty)
+        {
+            // Fire-and-forget — don't block circuit teardown on a slow capture.
+            _ = BrowserService.CloseAsync(_token);
+        }
+        return ValueTask.CompletedTask;
+    }
 }
@@ -34,13 +34,19 @@
                     CurrentAddress="@_pickerAddress"
                     OnPickAddress="@OnAddressPicked">
        <AbCipAddressPickerBody CurrentAddress="@_pickerAddress"
-                                CurrentAddressChanged="@((s) => _pickerAddress = s)" />
+                                CurrentAddressChanged="@((s) => _pickerAddress = s)"
+                                DriverType="@DriverType"
+                                GetConfigJson="@GetDriverConfigJson" />
    </DriverTagPicker>
 }

@code {
    [Parameter] public string? ConfigJson { get; set; }
    [Parameter] public EventCallback<string> ConfigJsonChanged { get; set; }
+    /// <summary>DriverType of the selected driver — lets browse-capable pickers open a universal session.</summary>
+    [Parameter] public string DriverType { get; set; } = "";
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetDriverConfigJson { get; set; } = () => "{}";

    private AbCipTagConfigModel _m = new();
    private string? _lastConfigJson;
@@ -41,6 +41,10 @@
@code {
    [Parameter] public string? ConfigJson { get; set; }
    [Parameter] public EventCallback<string> ConfigJsonChanged { get; set; }
+    /// <summary>DriverType of the selected driver — lets browse-capable pickers open a universal session.</summary>
+    [Parameter] public string DriverType { get; set; } = "";
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetDriverConfigJson { get; set; } = () => "{}";

    private AbLegacyTagConfigModel _m = new();
    private string? _lastConfigJson;
@@ -32,13 +32,19 @@
                     CurrentAddress="@_pickerAddress"
                     OnPickAddress="@OnAddressPicked">
        <FOCASAddressPickerBody CurrentAddress="@_pickerAddress"
-                                CurrentAddressChanged="@((s) => _pickerAddress = s)" />
+                                CurrentAddressChanged="@((s) => _pickerAddress = s)"
+                                DriverType="@DriverType"
+                                GetConfigJson="@GetDriverConfigJson" />
    </DriverTagPicker>
 }

@code {
    [Parameter] public string? ConfigJson { get; set; }
    [Parameter] public EventCallback<string> ConfigJsonChanged { get; set; }
+    /// <summary>DriverType of the selected driver — lets browse-capable pickers open a universal session.</summary>
+    [Parameter] public string DriverType { get; set; } = "";
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetDriverConfigJson { get; set; } = () => "{}";

    private FocasTagConfigModel _m = new();
    private string? _lastConfigJson;
@@ -49,6 +49,10 @@
@code {
    [Parameter] public string? ConfigJson { get; set; }
    [Parameter] public EventCallback<string> ConfigJsonChanged { get; set; }
+    /// <summary>DriverType of the selected driver — lets browse-capable pickers open a universal session.</summary>
+    [Parameter] public string DriverType { get; set; } = "";
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetDriverConfigJson { get; set; } = () => "{}";

    private ModbusTagConfigModel _m = new();
    private string? _lastConfigJson;
@@ -11,6 +11,10 @@
@code {
    [Parameter] public string? ConfigJson { get; set; }
    [Parameter] public EventCallback<string> ConfigJsonChanged { get; set; }
+    /// <summary>DriverType of the selected driver — lets browse-capable pickers open a universal session.</summary>
+    [Parameter] public string DriverType { get; set; } = "";
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetDriverConfigJson { get; set; } = () => "{}";

    private OpcUaClientTagConfigModel _m = new();
    private string? _lastConfigJson;
@@ -41,6 +41,10 @@
@code {
    [Parameter] public string? ConfigJson { get; set; }
    [Parameter] public EventCallback<string> ConfigJsonChanged { get; set; }
+    /// <summary>DriverType of the selected driver — lets browse-capable pickers open a universal session.</summary>
+    [Parameter] public string DriverType { get; set; } = "";
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetDriverConfigJson { get; set; } = () => "{}";

    private S7TagConfigModel _m = new();
    private string? _lastConfigJson;
@@ -34,13 +34,19 @@
                     CurrentAddress="@_pickerAddress"
                     OnPickAddress="@OnAddressPicked">
        <TwinCATAddressPickerBody CurrentAddress="@_pickerAddress"
-                                  CurrentAddressChanged="@((s) => _pickerAddress = s)" />
+                                  CurrentAddressChanged="@((s) => _pickerAddress = s)"
+                                  DriverType="@DriverType"
+                                  GetConfigJson="@GetDriverConfigJson" />
    </DriverTagPicker>
 }

@code {
    [Parameter] public string? ConfigJson { get; set; }
    [Parameter] public EventCallback<string> ConfigJsonChanged { get; set; }
+    /// <summary>DriverType of the selected driver — lets browse-capable pickers open a universal session.</summary>
+    [Parameter] public string DriverType { get; set; } = "";
+    /// <summary>Live accessor for the selected driver's DriverConfig JSON (browse connect config).</summary>
+    [Parameter] public Func<string> GetDriverConfigJson { get; set; } = () => "{}";

    private TwinCATTagConfigModel _m = new();
    private string? _lastConfigJson;
@@ -353,6 +353,8 @@
    {
        ["ConfigJson"] = _form.TagConfig,
        ["ConfigJsonChanged"] = EventCallback.Factory.Create<string>(this, v => _form.TagConfig = v),
+        ["DriverType"] = SelectedDriverType ?? "",
+        ["GetDriverConfigJson"] = (Func<string>)(() => SelectedDriverConfig),
    };

    // Cache a single NativeAlarmModel parse keyed on the current TagConfig string, so the two computed
@@ -3,9 +3,11 @@ using Microsoft.AspNetCore.Components;
 using Microsoft.AspNetCore.Components.Web;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
 using ZB.MOM.WW.OtOpcUa.AdminUI.Hubs;
 using ZB.MOM.WW.OtOpcUa.AdminUI.Uns;
 using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Browser;
 using ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser;

@@ -48,6 +50,12 @@ public static class EndpointRouteBuilderExtensions
        services.AddScoped<IUnsTreeService, UnsTreeService>();
        services.AddSingleton<IDriverBrowser, OpcUaClientDriverBrowser>();
        services.AddSingleton<IDriverBrowser, GalaxyDriverBrowser>();
+        // Universal Discover-backed fallback browser (Wave 0). IDriverFactory is bound by the
+        // fused Host's DriverFactoryBootstrap; a standalone AdminUI has none → NullDriverFactory
+        // → CanBrowse false → pickers gracefully stay manual-entry (design §6).
+        services.AddSingleton<IUniversalDriverBrowser>(sp => new DiscoveryDriverBrowser(
+            sp.GetService<IDriverFactory>() ?? NullDriverFactory.Instance,
+            sp.GetRequiredService<ILogger<DiscoveryDriverBrowser>>()));

        // Roslyn-backed Monaco script-editor analysis (diagnostics/completions/hover/...).
        services.AddScoped<ScriptAnalysis.ScriptAnalysisService>();
@@ -0,0 +1,115 @@
+using Shouldly;
+using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Tests.Browsing;
+
+public class CapturedTreeBrowseSessionTests
+{
+    private static DriverAttributeInfo Attr(string fullName, bool isAlarm = false) =>
+        new(fullName, DriverDataType.Float64, false, null, SecurityClassification.Operate, false, IsAlarm: isAlarm);
+
+    // A small captured graph: a folder Plc1 with a Speed leaf and an alarm leaf, plus a root-level leaf.
+    // truncated=true builds with a tiny cap so recording stops short and Truncated flips.
+    private static CapturedTree SampleTree(bool truncated = false)
+    {
+        var b = new CapturingAddressSpaceBuilder(nodeCap: truncated ? 2 : 100);
+        var plc = b.Folder("Plc1", "PLC 1");
+        plc.Variable("Speed", "Speed", Attr("Plc1.Speed"));
+        plc.Variable("Alarm", "Alarm", Attr("Plc1.Alarm")).MarkAsAlarmCondition(
+            new AlarmConditionInfo("Alarm", AlarmSeverity.High, null));
+        b.Variable("Direct", "Direct", Attr("Root.Direct"));
+        return b.Build();
+    }
+
+    [Fact]
+    public async Task RootReturnsTopLevelNodes()
+    {
+        await using var s = new CapturedTreeBrowseSession(SampleTree());
+        var root = await s.RootAsync(CancellationToken.None);
+
+        var folder = root.Single(n => n.NodeId == "/Plc1");
+        folder.Kind.ShouldBe(BrowseNodeKind.Folder);
+        folder.HasChildrenHint.ShouldBeTrue();
+
+        var leaf = root.Single(n => n.NodeId == "Root.Direct");
+        leaf.Kind.ShouldBe(BrowseNodeKind.Leaf);
+        leaf.NodeId.ShouldBe("Root.Direct"); // leaf NodeId IS the driver FullName
+    }
+
+    [Fact]
+    public async Task ExpandReturnsCapturedChildren()
+    {
+        await using var s = new CapturedTreeBrowseSession(SampleTree());
+        var kids = await s.ExpandAsync("/Plc1", CancellationToken.None);
+        kids.Select(n => n.NodeId).ShouldBe(new[] { "Plc1.Speed", "Plc1.Alarm" });
+    }
+
+    [Fact]
+    public async Task ExpandUnknownNodeReturnsEmpty()
+    {
+        await using var s = new CapturedTreeBrowseSession(SampleTree());
+        (await s.ExpandAsync("/nope", CancellationToken.None)).ShouldBeEmpty();
+    }
+
+    [Fact]
+    public async Task AttributesForLeafMapsDriverAttributeInfo()
+    {
+        await using var s = new CapturedTreeBrowseSession(SampleTree());
+        var attrs = await s.AttributesAsync("Plc1.Speed", CancellationToken.None);
+        var a = attrs.Single();
+        a.Name.ShouldBe("Speed");
+        a.DriverDataType.ShouldBe(DriverDataType.Float64.ToString());
+        a.IsArray.ShouldBeFalse();
+        a.SecurityClass.ShouldBe(SecurityClassification.Operate.ToString());
+        a.IsAlarm.ShouldBeFalse();
+
+        // Alarm marked during discovery surfaces IsAlarm=true even though attr.IsAlarm is false.
+        var alarmAttrs = await s.AttributesAsync("Plc1.Alarm", CancellationToken.None);
+        alarmAttrs.Single().IsAlarm.ShouldBeTrue();
+    }
+
+    [Fact]
+    public async Task TruncatedTreeAppendsMarkerFolderAtRoot()
+    {
+        await using var s = new CapturedTreeBrowseSession(SampleTree(truncated: true));
+        var root = await s.RootAsync(CancellationToken.None);
+        var marker = root[^1];
+        marker.Kind.ShouldBe(BrowseNodeKind.Folder);
+        marker.HasChildrenHint.ShouldBeFalse();
+        marker.DisplayName.ToLowerInvariant().ShouldContain("truncated");
+    }
+
+    [Fact]
+    public async Task CallsRefreshLastUsedUtc()
+    {
+        await using var s = new CapturedTreeBrowseSession(SampleTree());
+        var before = s.LastUsedUtc;
+        await Task.Delay(5, TestContext.Current.CancellationToken);
+        await s.RootAsync(CancellationToken.None);
+        s.LastUsedUtc.ShouldBeGreaterThan(before);
+    }
+
+    [Fact]
+    public async Task DisposedSessionThrowsObjectDisposed()
+    {
+        var s = new CapturedTreeBrowseSession(SampleTree());
+        await s.DisposeAsync();
+        await Should.ThrowAsync<ObjectDisposedException>(() => s.RootAsync(CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task TwoSessionsOverSameTreeAreIndependent()
+    {
+        var tree = SampleTree();
+        var s1 = new CapturedTreeBrowseSession(tree);
+        var s2 = new CapturedTreeBrowseSession(tree);
+        s1.Token.ShouldNotBe(s2.Token);
+
+        await s1.DisposeAsync();
+        // Disposing s1 must not affect s2 — the tree is immutable and shared.
+        (await s2.RootAsync(CancellationToken.None)).ShouldNotBeEmpty();
+        await s2.DisposeAsync();
+    }
+}
@@ -0,0 +1,70 @@
+using Shouldly;
+using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Tests.Browsing;
+
+public class CapturingAddressSpaceBuilderTests
+{
+    private static DriverAttributeInfo Attr(string fullName, bool isAlarm = false) =>
+        new(fullName, DriverDataType.Float64, false, null, SecurityClassification.Operate, false, IsAlarm: isAlarm);
+
+    [Fact]
+    public void CapturesNestedFoldersAndLeaves()
+    {
+        var b = new CapturingAddressSpaceBuilder(nodeCap: 100);
+        var plc = b.Folder("Plc1", "PLC 1");
+        plc.Variable("Speed", "Speed", Attr("Program:Main.Speed"));
+        var udt = plc.Folder("Motor", "Motor");
+        udt.Variable("Amps", "Amps", Attr("Program:Main.Motor.Amps"));
+
+        var tree = b.Build();
+        tree.Truncated.ShouldBeFalse();
+        tree.Root.Children.Count.ShouldBe(1);
+        var plcNode = tree.Root.Children[0];
+        plcNode.Id.ShouldBe("/Plc1");
+        plcNode.IsLeaf.ShouldBeFalse();
+        plcNode.Children.Select(c => c.Id).ShouldBe(new[] { "Program:Main.Speed", "/Plc1/Motor" });
+        tree.ById["Program:Main.Motor.Amps"].Attribute!.FullName.ShouldBe("Program:Main.Motor.Amps");
+    }
+
+    [Fact]
+    public void LeafNodeIdIsTheDriverFullName()
+    {
+        var b = new CapturingAddressSpaceBuilder(100);
+        var handle = b.Variable("T", "T", Attr("Device.Tag1"));
+        handle.FullReference.ShouldBe("Device.Tag1");
+        b.Build().ById["Device.Tag1"].IsLeaf.ShouldBeTrue();
+    }
+
+    [Fact]
+    public void NodeCapTruncatesInsteadOfGrowing()
+    {
+        var b = new CapturingAddressSpaceBuilder(nodeCap: 3);
+        for (var i = 0; i < 10; i++) b.Variable($"T{i}", $"T{i}", Attr($"Dev.T{i}"));
+        var tree = b.Build();
+        tree.Truncated.ShouldBeTrue();
+        tree.Count.ShouldBe(3);
+    }
+
+    [Fact]
+    public void MarkAsAlarmConditionRecordsAlarmAndReturnsNoopSink()
+    {
+        var b = new CapturingAddressSpaceBuilder(100);
+        var h = b.Variable("A", "A", Attr("Dev.Alarm1"));
+        var sink = h.MarkAsAlarmCondition(new AlarmConditionInfo("A", AlarmSeverity.High, null));
+        sink.ShouldNotBeNull();
+        Should.NotThrow(() => sink.OnTransition(null!)); // no-op — browse never delivers transitions
+        b.Build().ById["Dev.Alarm1"].IsAlarmMarked.ShouldBeTrue();
+    }
+
+    [Fact]
+    public void AddPropertyAttachesToCurrentScope()
+    {
+        var b = new CapturingAddressSpaceBuilder(100);
+        var f = b.Folder("Dev", "Dev");
+        f.AddProperty("Model", DriverDataType.String, "1756-L83E");
+        b.Build().ById["/Dev"].Properties.ShouldContain(p => p.Name == "Model" && (string?)p.Value == "1756-L83E");
+    }
+}
@@ -0,0 +1,177 @@
+using Microsoft.Extensions.Logging.Abstractions;
+using Shouldly;
+using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Tests.Browsing;
+
+public class DiscoveryDriverBrowserConcurrencyTests
+{
+    private static readonly TimeSpan LongOpen = TimeSpan.FromSeconds(30);
+    private static readonly TimeSpan ShortShutdown = TimeSpan.FromMilliseconds(200);
+    private static readonly TimeSpan Wait = TimeSpan.FromSeconds(5);
+
+    private static DiscoveryDriverBrowser Browser(IDriverFactory factory) =>
+        new(factory, NullLogger<DiscoveryDriverBrowser>.Instance, LongOpen, ShortShutdown);
+
+    /// <summary>A driver gate: signals when Initialize is entered, blocks until released.</summary>
+    private sealed class Gate
+    {
+        public readonly SemaphoreSlim Entered = new(0);
+        public readonly TaskCompletionSource Release = new(TaskCreationOptions.RunContinuationsAsynchronously);
+    }
+
+    private static FakeDiscoveryDriver Gated(Gate gate) => new()
+    {
+        OnInitialize = async ct =>
+        {
+            gate.Entered.Release();
+            await gate.Release.Task.WaitAsync(ct);
+        },
+    };
+
+    [Fact]
+    public async Task SameKey_TwoConcurrentOpens_OneCapture_DistinctTokens()
+    {
+        var gate = new Gate();
+        var factory = FakeDriverFactory.Of(() => Gated(gate));
+        var browser = Browser(factory);
+
+        var open1 = browser.OpenAsync("Fake", """{"h":"1"}""", CancellationToken.None);
+        var open2 = browser.OpenAsync("Fake", """{"h":"1"}""", CancellationToken.None);
+
+        await gate.Entered.WaitAsync(Wait, TestContext.Current.CancellationToken);          // one driver entered Initialize
+        factory.CreateCalls.ShouldBe(1);             // coalesced — only one driver constructed
+        gate.Release.SetResult();
+
+        var s1 = await open1;
+        var s2 = await open2;
+        s1.Token.ShouldNotBe(s2.Token);              // distinct sessions...
+        (await s1.RootAsync(CancellationToken.None)).Count
+            .ShouldBe((await s2.RootAsync(CancellationToken.None)).Count); // ...over the same tree
+        ((FakeDiscoveryDriver)factory.Created[0]).InitializeCalls.ShouldBe(1);
+    }
+
+    [Fact]
+    public async Task SameKey_DisposingOneSession_LeavesOtherBrowsable()
+    {
+        var gate = new Gate();
+        var browser = Browser(FakeDriverFactory.Of(() => Gated(gate)));
+
+        var open1 = browser.OpenAsync("Fake", """{"h":"1"}""", CancellationToken.None);
+        var open2 = browser.OpenAsync("Fake", """{"h":"1"}""", CancellationToken.None);
+        await gate.Entered.WaitAsync(Wait, TestContext.Current.CancellationToken);
+        gate.Release.SetResult();
+
+        var s1 = await open1;
+        var s2 = await open2;
+        await s1.DisposeAsync();
+        (await s2.RootAsync(CancellationToken.None)).ShouldNotBeEmpty(); // shared immutable tree survives
+    }
+
+    [Fact]
+    public async Task SameKey_FailedCapture_FailsBothAwaiters()
+    {
+        var factory = FakeDriverFactory.Of(() => new FakeDiscoveryDriver
+        {
+            OnDiscover = (_, _) => throw new InvalidOperationException("shared-boom"),
+        });
+        var browser = Browser(factory);
+
+        var open1 = browser.OpenAsync("Fake", """{"h":"1"}""", CancellationToken.None);
+        var open2 = browser.OpenAsync("Fake", """{"h":"1"}""", CancellationToken.None);
+
+        (await Should.ThrowAsync<InvalidOperationException>(() => open1)).Message.ShouldBe("shared-boom");
+        (await Should.ThrowAsync<InvalidOperationException>(() => open2)).Message.ShouldBe("shared-boom");
+    }
+
+    [Fact]
+    public async Task SameKey_OpenAfterCompletion_RunsFreshCapture()
+    {
+        var factory = FakeDriverFactory.Of(() => new FakeDiscoveryDriver()); // ungated, completes fast
+        var browser = Browser(factory);
+
+        await browser.OpenAsync("Fake", """{"h":"1"}""", CancellationToken.None);
+        await browser.OpenAsync("Fake", """{"h":"1"}""", CancellationToken.None);
+
+        factory.CreateCalls.ShouldBe(2); // in-flight-only map: second open is a fresh capture (Refresh path)
+    }
+
+    [Fact]
+    public async Task DistinctKeys_CapLimitsInflightCaptures()
+    {
+        const int cap = DiscoveryDriverBrowser.MaxConcurrentCaptures; // 4
+        const int total = cap + 2;                                    // 6
+        var release = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+        var entered = 0;
+        var factory = new FakeDriverFactory((_, _, _) => new FakeDiscoveryDriver
+        {
+            OnInitialize = async ct => { Interlocked.Increment(ref entered); await release.Task.WaitAsync(ct); },
+        });
+        var browser = Browser(factory);
+
+        var opens = Enumerable.Range(0, total)
+            .Select(i => browser.OpenAsync("Fake", $$"""{"i":{{i}}}""", CancellationToken.None))
+            .ToArray();
+
+        // Give the semaphore time to admit exactly `cap` captures into Initialize.
+        await Task.Delay(TimeSpan.FromMilliseconds(500), TestContext.Current.CancellationToken);
+        Volatile.Read(ref entered).ShouldBe(cap); // at most 4 in flight; the other 2 queue on the semaphore
+
+        release.SetResult();
+        var sessions = await Task.WhenAll(opens);
+        sessions.Length.ShouldBe(total);
+        factory.CreateCalls.ShouldBe(total); // all eventually run once a slot frees
+    }
+
+    [Fact]
+    public async Task QueuedOpen_ObservesCallerCancellation()
+    {
+        const int cap = DiscoveryDriverBrowser.MaxConcurrentCaptures; // 4
+        var release = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+        var factory = new FakeDriverFactory((_, _, _) => new FakeDiscoveryDriver
+        {
+            OnInitialize = async ct => { await release.Task.WaitAsync(ct); },
+        });
+        var browser = Browser(factory);
+
+        // Fill all slots with distinct-key captures.
+        var inflight = Enumerable.Range(0, cap)
+            .Select(i => browser.OpenAsync("Fake", $$"""{"i":{{i}}}""", CancellationToken.None))
+            .ToArray();
+        await Task.Delay(TimeSpan.FromMilliseconds(300), TestContext.Current.CancellationToken);
+
+        // A queued open with a cancelable token — it waits for a slot, then the caller cancels.
+        using var cts = new CancellationTokenSource();
+        var queued = browser.OpenAsync("Fake", """{"i":"queued"}""", cts.Token);
+        cts.Cancel();
+        await Should.ThrowAsync<OperationCanceledException>(() => queued);
+
+        // The in-flight captures are unaffected.
+        release.SetResult();
+        var done = await Task.WhenAll(inflight);
+        done.Length.ShouldBe(cap);
+    }
+
+    [Fact]
+    public async Task CoalescedAwaiter_CancellationDoesNotCancelSharedCapture()
+    {
+        var gate = new Gate();
+        var factory = FakeDriverFactory.Of(() => Gated(gate));
+        var browser = Browser(factory);
+
+        using var cts1 = new CancellationTokenSource();
+        var open1 = browser.OpenAsync("Fake", """{"h":"1"}""", cts1.Token);
+        var open2 = browser.OpenAsync("Fake", """{"h":"1"}""", CancellationToken.None);
+
+        await gate.Entered.WaitAsync(Wait, TestContext.Current.CancellationToken);
+        cts1.Cancel();                                    // first caller abandons
+        await Should.ThrowAsync<OperationCanceledException>(() => open1);
+
+        gate.Release.SetResult();                         // shared capture proceeds regardless
+        var s2 = await open2;
+        (await s2.RootAsync(CancellationToken.None)).ShouldNotBeEmpty();
+        ((FakeDiscoveryDriver)factory.Created[0]).InitializeCalls.ShouldBe(1);
+    }
+}
@@ -0,0 +1,118 @@
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Tests.Browsing;
+
+/// <summary>Shared test doubles for the DiscoveryDriverBrowser suites (Tasks 8–10).</summary>
+internal sealed class FakeDiscoveryDriver : IDriver, ITagDiscovery
+{
+    public int InitializeCalls;
+    public int DiscoverCalls;
+    public int ShutdownCalls;
+
+    /// <summary>Ordered lifecycle trace ("init"/"discover"/"shutdown").</summary>
+    public List<string> Trace { get; } = [];
+
+    /// <summary>Completes once ShutdownAsync has finished (even the fire-and-forget CanBrowse path).</summary>
+    public TaskCompletionSource ShutdownDone { get; } = new(TaskCreationOptions.RunContinuationsAsynchronously);
+
+    public bool SupportsOnlineDiscovery { get; init; } = true;
+    public DiscoveryRediscoverPolicy RediscoverPolicy { get; init; } = DiscoveryRediscoverPolicy.Once;
+
+    /// <summary>Discovery behavior: (builder, 1-based call index) → task. Default streams one leaf.</summary>
+    public Func<IAddressSpaceBuilder, int, Task>? OnDiscover { get; init; }
+    public Func<CancellationToken, Task>? OnInitialize { get; init; }
+    public Func<CancellationToken, Task>? OnShutdown { get; init; }
+
+    public string DriverInstanceId { get; }
+    public string DriverType { get; }
+    public string? LastConfigJson { get; private set; }
+
+    public FakeDiscoveryDriver(string driverType = "Fake", string id = "fake-1")
+    {
+        DriverType = driverType;
+        DriverInstanceId = id;
+    }
+
+    public async Task InitializeAsync(string driverConfigJson, CancellationToken cancellationToken)
+    {
+        LastConfigJson = driverConfigJson;
+        Interlocked.Increment(ref InitializeCalls);
+        lock (Trace) Trace.Add("init");
+        if (OnInitialize is not null) await OnInitialize(cancellationToken).ConfigureAwait(false);
+    }
+
+    public async Task DiscoverAsync(IAddressSpaceBuilder builder, CancellationToken cancellationToken)
+    {
+        var idx = Interlocked.Increment(ref DiscoverCalls);
+        lock (Trace) Trace.Add("discover");
+        if (OnDiscover is not null)
+        {
+            await OnDiscover(builder, idx).ConfigureAwait(false);
+            return;
+        }
+        // Default: stream one leaf so the captured tree is non-empty.
+        builder.Variable("Tag1", "Tag1",
+            new DriverAttributeInfo("Dev.Tag1", DriverDataType.Float64, false, null,
+                SecurityClassification.Operate, false));
+    }
+
+    public async Task ShutdownAsync(CancellationToken cancellationToken)
+    {
+        Interlocked.Increment(ref ShutdownCalls);
+        lock (Trace) Trace.Add("shutdown");
+        try
+        {
+            if (OnShutdown is not null) await OnShutdown(cancellationToken).ConfigureAwait(false);
+        }
+        finally
+        {
+            ShutdownDone.TrySetResult();
+        }
+    }
+
+    public Task ReinitializeAsync(string driverConfigJson, CancellationToken cancellationToken) => Task.CompletedTask;
+    public DriverHealth GetHealth() => new(DriverState.Healthy, null, null);
+    public long GetMemoryFootprint() => 0;
+    public Task FlushOptionalCachesAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+}
+
+/// <summary>An IDriver that is NOT ITagDiscovery — exercises the not-discovery-capable gate.</summary>
+internal sealed class FakeNonDiscoveryDriver(string driverType = "Flat", string id = "flat-1") : IDriver
+{
+    public int ShutdownCalls;
+    public TaskCompletionSource ShutdownDone { get; } = new(TaskCreationOptions.RunContinuationsAsynchronously);
+    public string DriverInstanceId { get; } = id;
+    public string DriverType { get; } = driverType;
+    public Task InitializeAsync(string driverConfigJson, CancellationToken cancellationToken) => Task.CompletedTask;
+    public Task ReinitializeAsync(string driverConfigJson, CancellationToken cancellationToken) => Task.CompletedTask;
+    public Task ShutdownAsync(CancellationToken cancellationToken)
+    {
+        Interlocked.Increment(ref ShutdownCalls);
+        ShutdownDone.TrySetResult();
+        return Task.CompletedTask;
+    }
+    public DriverHealth GetHealth() => new(DriverState.Healthy, null, null);
+    public long GetMemoryFootprint() => 0;
+    public Task FlushOptionalCachesAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+}
+
+/// <summary>Configurable IDriverFactory: delegates construction to a supplied func and records what it made.</summary>
+internal sealed class FakeDriverFactory(Func<string, string, string, IDriver?> create) : IDriverFactory
+{
+    public int CreateCalls;
+    public List<IDriver> Created { get; } = [];
+
+    public IDriver? TryCreate(string driverType, string driverInstanceId, string driverConfigJson)
+    {
+        Interlocked.Increment(ref CreateCalls);
+        var d = create(driverType, driverInstanceId, driverConfigJson);
+        if (d is not null) lock (Created) Created.Add(d);
+        return d;
+    }
+
+    public IReadOnlyCollection<string> SupportedTypes { get; } = Array.Empty<string>();
+
+    /// <summary>Factory that always returns a fresh default FakeDiscoveryDriver.</summary>
+    public static FakeDriverFactory Of(Func<FakeDiscoveryDriver> make) =>
+        new((_, _, _) => make());
+}
@@ -0,0 +1,87 @@
+using Microsoft.Extensions.Logging.Abstractions;
+using Shouldly;
+using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Tests.Browsing;
+
+public class DiscoveryDriverBrowserSettleTests
+{
+    private static readonly TimeSpan ShortShutdown = TimeSpan.FromMilliseconds(200);
+
+    private static DiscoveryDriverBrowser Browser(IDriverFactory factory, TimeSpan openTimeout) =>
+        new(factory, NullLogger<DiscoveryDriverBrowser>.Instance, openTimeout, ShortShutdown);
+
+    private static void StreamN(IAddressSpaceBuilder builder, int n)
+    {
+        for (var i = 0; i < n; i++)
+            builder.Variable($"T{i}", $"T{i}",
+                new DriverAttributeInfo($"Dev.T{i}", DriverDataType.Float64, false, null,
+                    SecurityClassification.Operate, false));
+    }
+
+    [Fact]
+    public async Task UntilStable_RerunsUntilNonEmptyAndStable()
+    {
+        // Pass 1 streams nothing (FixedTree cache still filling); passes 2+ stream 3 nodes.
+        var driver = new FakeDiscoveryDriver
+        {
+            RediscoverPolicy = DiscoveryRediscoverPolicy.UntilStable,
+            OnDiscover = (b, idx) => { if (idx >= 2) StreamN(b, 3); return Task.CompletedTask; },
+        };
+        var browser = Browser(FakeDriverFactory.Of(() => driver), TimeSpan.FromSeconds(30));
+
+        var session = await browser.OpenAsync("Fake", "{}", CancellationToken.None);
+        var root = await session.RootAsync(CancellationToken.None);
+
+        root.Count.ShouldBe(3);
+        driver.DiscoverCalls.ShouldBeGreaterThanOrEqualTo(3); // empty -> 3 -> 3-stable
+    }
+
+    [Fact]
+    public async Task UntilStable_NeverStable_ReturnsLastNonEmptyAtTimeout()
+    {
+        // Node count grows every pass — never stabilises; on open-timeout return the last capture.
+        var driver = new FakeDiscoveryDriver
+        {
+            RediscoverPolicy = DiscoveryRediscoverPolicy.UntilStable,
+            OnDiscover = (b, idx) => { StreamN(b, idx); return Task.CompletedTask; },
+        };
+        var browser = Browser(FakeDriverFactory.Of(() => driver), TimeSpan.FromSeconds(3));
+
+        var session = await browser.OpenAsync("Fake", "{}", CancellationToken.None);
+        var root = await session.RootAsync(CancellationToken.None);
+
+        root.ShouldNotBeEmpty(); // last non-empty capture, not an exception
+    }
+
+    [Fact]
+    public async Task UntilStable_NeverAnyNodes_FailsAtOpenTimeout()
+    {
+        // Every pass empty — no non-empty capture to fall back to, so the timeout surfaces.
+        var driver = new FakeDiscoveryDriver
+        {
+            RediscoverPolicy = DiscoveryRediscoverPolicy.UntilStable,
+            OnDiscover = (_, _) => Task.CompletedTask,
+        };
+        var browser = Browser(FakeDriverFactory.Of(() => driver), TimeSpan.FromSeconds(2));
+
+        await Should.ThrowAsync<OperationCanceledException>(
+            () => browser.OpenAsync("Fake", "{}", CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task OncePolicy_SingleDiscoverPass()
+    {
+        var driver = new FakeDiscoveryDriver
+        {
+            RediscoverPolicy = DiscoveryRediscoverPolicy.Once,
+            OnDiscover = (b, _) => { StreamN(b, 3); return Task.CompletedTask; },
+        };
+        var browser = Browser(FakeDriverFactory.Of(() => driver), TimeSpan.FromSeconds(30));
+
+        await browser.OpenAsync("Fake", "{}", CancellationToken.None);
+        driver.DiscoverCalls.ShouldBe(1);
+    }
+}
@@ -0,0 +1,145 @@
+using Microsoft.Extensions.Logging.Abstractions;
+using Shouldly;
+using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Tests.Browsing;
+
+public class DiscoveryDriverBrowserTests
+{
+    private static readonly TimeSpan ShortOpen = TimeSpan.FromSeconds(5);
+    private static readonly TimeSpan ShortShutdown = TimeSpan.FromMilliseconds(200);
+
+    private static DiscoveryDriverBrowser Browser(IDriverFactory factory) =>
+        new(factory, NullLogger<DiscoveryDriverBrowser>.Instance, ShortOpen, ShortShutdown);
+
+    [Fact]
+    public async Task OpenAsync_RunsInitializeDiscoverShutdown_InOrder()
+    {
+        var driver = new FakeDiscoveryDriver();
+        var browser = Browser(FakeDriverFactory.Of(() => driver));
+
+        var session = await browser.OpenAsync("Fake", "{}", CancellationToken.None);
+
+        session.ShouldNotBeNull();
+        driver.Trace.ShouldBe(new[] { "init", "discover", "shutdown" });
+        driver.InitializeCalls.ShouldBe(1);
+        driver.ShutdownCalls.ShouldBe(1);
+    }
+
+    [Fact]
+    public async Task OpenAsync_ShutdownRuns_EvenWhenDiscoverThrows()
+    {
+        var driver = new FakeDiscoveryDriver
+        {
+            OnDiscover = (_, _) => throw new InvalidOperationException("boom-discovery"),
+        };
+        var browser = Browser(FakeDriverFactory.Of(() => driver));
+
+        var ex = await Should.ThrowAsync<InvalidOperationException>(
+            () => browser.OpenAsync("Fake", "{}", CancellationToken.None));
+        ex.Message.ShouldBe("boom-discovery"); // discovery error surfaces, not a shutdown error
+        driver.ShutdownCalls.ShouldBe(1);       // shutdown still ran
+    }
+
+    [Fact]
+    public async Task OpenAsync_UnknownType_ThrowsCleanMessage()
+    {
+        var browser = Browser(new FakeDriverFactory((_, _, _) => null));
+        var ex = await Should.ThrowAsync<InvalidOperationException>(
+            () => browser.OpenAsync("Ghost", "{}", CancellationToken.None));
+        ex.Message.ShouldContain("Ghost");
+    }
+
+    [Fact]
+    public async Task OpenAsync_NotDiscoveryCapable_Throws()
+    {
+        var browser = Browser(new FakeDriverFactory((_, _, _) => new FakeNonDiscoveryDriver()));
+        await Should.ThrowAsync<InvalidOperationException>(
+            () => browser.OpenAsync("Flat", "{}", CancellationToken.None));
+    }
+
+    [Fact]
+    public async Task OpenAsync_FlagFalse_Throws()
+    {
+        var browser = Browser(FakeDriverFactory.Of(() => new FakeDiscoveryDriver { SupportsOnlineDiscovery = false }));
+        await Should.ThrowAsync<InvalidOperationException>(
+            () => browser.OpenAsync("Fake", "{}", CancellationToken.None));
+    }
+
+    [Fact]
+    public void PatchForBrowse_MergesAbCipPatch()
+    {
+        var patched = DiscoveryDriverBrowser.PatchForBrowse("AbCip", """{ "Host": "1.2.3.4" }""");
+        var obj = System.Text.Json.Nodes.JsonNode.Parse(patched)!.AsObject();
+        ((string?)obj["Host"]).ShouldBe("1.2.3.4");
+        ((bool?)obj["EnableControllerBrowse"]).ShouldBe(true);
+
+        // Unknown type: unchanged.
+        DiscoveryDriverBrowser.PatchForBrowse("Modbus", """{ "X": 1 }""").ShouldBe("""{ "X": 1 }""");
+    }
+
+    [Fact]
+    public void PatchForBrowse_DeepMergesFocasFixedTree()
+    {
+        var patched = DiscoveryDriverBrowser.PatchForBrowse("FOCAS", """{ "FixedTree": { "Series": "30i" } }""");
+        var fixedTree = System.Text.Json.Nodes.JsonNode.Parse(patched)!["FixedTree"]!.AsObject();
+        ((string?)fixedTree["Series"]).ShouldBe("30i");   // kept
+        ((bool?)fixedTree["Enabled"]).ShouldBe(true);      // added
+    }
+
+    [Fact]
+    public void CanBrowse_TrueForDiscoveryCapable()
+    {
+        var browser = Browser(FakeDriverFactory.Of(() => new FakeDiscoveryDriver()));
+        browser.CanBrowse("Fake", "{}").ShouldBeTrue();
+    }
+
+    [Fact]
+    public void CanBrowse_FalseWhenTryCreateReturnsNull()
+    {
+        var browser = Browser(new FakeDriverFactory((_, _, _) => null));
+        browser.CanBrowse("Ghost", "{}").ShouldBeFalse();
+    }
+
+    [Fact]
+    public void CanBrowse_FalseWhenTryCreateThrows_NoExceptionEscapes()
+    {
+        var browser = Browser(new FakeDriverFactory((_, _, _) => throw new System.Text.Json.JsonException("bad json")));
+        Should.NotThrow(() => browser.CanBrowse("Fake", "{ half-typed").ShouldBeFalse());
+    }
+
+    [Fact]
+    public async Task CanBrowse_ShutsDownThrowawayInstance()
+    {
+        var driver = new FakeDiscoveryDriver { SupportsOnlineDiscovery = false };
+        var factory = FakeDriverFactory.Of(() => driver);
+        var browser = Browser(factory);
+
+        browser.CanBrowse("Fake", "{}").ShouldBeFalse();
+        // Teardown is fire-and-forget — await its completion.
+        await driver.ShutdownDone.Task.WaitAsync(TimeSpan.FromSeconds(2), TestContext.Current.CancellationToken);
+        driver.ShutdownCalls.ShouldBe(1);
+    }
+
+    [Fact]
+    public async Task BoundedShutdown_AbandonsWedgedDriver()
+    {
+        // Shutdown ignores its token and would never complete; the browser must abandon it
+        // and still return the successfully-captured session within the shutdown bound.
+        var driver = new FakeDiscoveryDriver
+        {
+            OnShutdown = _ => Task.Delay(Timeout.Infinite, CancellationToken.None),
+        };
+        var browser = Browser(FakeDriverFactory.Of(() => driver));
+
+        var sw = System.Diagnostics.Stopwatch.StartNew();
+        var session = await browser.OpenAsync("Fake", "{}", CancellationToken.None);
+        sw.Stop();
+
+        session.ShouldNotBeNull();                       // discovery succeeded → usable session
+        driver.ShutdownCalls.ShouldBe(1);                // shutdown was attempted
+        sw.Elapsed.ShouldBeLessThan(ShortOpen);          // returned on the shutdown bound, not the open timeout
+    }
+}
@@ -0,0 +1,21 @@
+using Shouldly;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions.Tests;
+
+public class TagDiscoveryDefaultsTests
+{
+    private sealed class MinimalDiscovery : ITagDiscovery
+    {
+        public Task DiscoverAsync(IAddressSpaceBuilder builder, CancellationToken ct) => Task.CompletedTask;
+    }
+
+    [Fact]
+    public void SupportsOnlineDiscovery_DefaultsToFalse() =>
+        ((ITagDiscovery)new MinimalDiscovery()).SupportsOnlineDiscovery.ShouldBeFalse();
+
+    [Fact]
+    public void RediscoverPolicy_DefaultRemainsUntilStable() =>
+        ((ITagDiscovery)new MinimalDiscovery()).RediscoverPolicy.ShouldBe(DiscoveryRediscoverPolicy.UntilStable);
+}
@@ -0,0 +1,19 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.AbCip;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.AbCip.Tests;
+
+[Trait("Category", "Unit")]
+public sealed class AbCipDiscoveryGateTests
+{
+    /// <summary>AbCip opts into the universal discovery browser — its CIP Symbol Object walk is real
+    /// device enumeration (config-gated on EnableControllerBrowse, guaranteed by PatchForBrowse at open).</summary>
+    [Fact]
+    public void SupportsOnlineDiscovery_IsTrue()
+    {
+        var drv = new AbCipDriver(new AbCipDriverOptions(), "drv-1");
+        ((ITagDiscovery)drv).SupportsOnlineDiscovery.ShouldBeTrue();
+    }
+}
@@ -0,0 +1,20 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.FOCAS;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Tests;
+
+[Trait("Category", "Unit")]
+public sealed class FocasDiscoveryGateTests
+{
+    /// <summary>FOCAS opts into the universal discovery browser — its FixedTree device folder is real
+    /// enumeration (config-gated on FixedTree.Enabled, turned on by PatchForBrowse). FOCAS is the
+    /// UntilStable driver: the browser's settle loop re-captures until the FixedTree cache fills.</summary>
+    [Fact]
+    public void SupportsOnlineDiscovery_IsTrue()
+    {
+        var drv = new FocasDriver(new FocasDriverOptions(), "drv-1");
+        ((ITagDiscovery)drv).SupportsOnlineDiscovery.ShouldBeTrue();
+    }
+}
@@ -0,0 +1,19 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.TwinCAT;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Tests;
+
+[Trait("Category", "Unit")]
+public sealed class TwinCATDiscoveryGateTests
+{
+    /// <summary>TwinCAT opts into the universal discovery browser — its ADS symbol upload is real
+    /// device enumeration (config-gated on EnableControllerBrowse, guaranteed by PatchForBrowse at open).</summary>
+    [Fact]
+    public void SupportsOnlineDiscovery_IsTrue()
+    {
+        var drv = new TwinCATDriver(new TwinCATDriverOptions(), "drv-1");
+        ((ITagDiscovery)drv).SupportsOnlineDiscovery.ShouldBeTrue();
+    }
+}
@@ -13,7 +13,11 @@ public sealed class BrowserSessionServiceTests
 {
    private static BrowserSessionService NewService(
        BrowseSessionRegistry registry, params IDriverBrowser[] browsers) =>
-        new(browsers, registry, NullLogger<BrowserSessionService>.Instance);
+        new(browsers, registry, NullLogger<BrowserSessionService>.Instance, new FakeUniversalDriverBrowser());
+
+    private static BrowserSessionService NewService(
+        BrowseSessionRegistry registry, IUniversalDriverBrowser universal, params IDriverBrowser[] browsers) =>
+        new(browsers, registry, NullLogger<BrowserSessionService>.Instance, universal);

    [Fact]
    public async Task OpenAsync_unknown_driver_type_returns_Ok_false_with_message()
@@ -68,6 +72,89 @@ public sealed class BrowserSessionServiceTests
        result.Message!.ShouldContain("boom");
    }

+    [Fact]
+    public async Task Open_BespokeBrowserWinsOverUniversal()
+    {
+        var registry = new BrowseSessionRegistry();
+        var bespokeSession = new FakeBrowseSession();
+        var bespoke = new FakeDriverBrowser("AbCip")
+        {
+            OpenHandler = (_, _) => Task.FromResult<IBrowseSession>(bespokeSession),
+        };
+        var universal = new FakeUniversalDriverBrowser
+        {
+            CanBrowsePredicate = (_, _) => true, // universal would also serve it
+            OpenHandler = (_, _, _) => Task.FromResult<IBrowseSession>(new FakeBrowseSession()),
+        };
+        var service = NewService(registry, universal, bespoke);
+
+        var result = await service.OpenAsync("AbCip", "{}", CancellationToken.None);
+
+        result.Ok.ShouldBeTrue();
+        result.Token.ShouldBe(bespokeSession.Token); // bespoke session, not the universal one
+    }
+
+    [Fact]
+    public async Task Open_FallsBackToUniversal_WhenNoBespokeAndCanBrowse()
+    {
+        var registry = new BrowseSessionRegistry();
+        var universalSession = new FakeBrowseSession();
+        var universal = new FakeUniversalDriverBrowser
+        {
+            CanBrowsePredicate = (t, _) => t == "AbCip",
+            OpenHandler = (_, _, _) => Task.FromResult<IBrowseSession>(universalSession),
+        };
+        var service = NewService(registry, universal); // no bespoke browsers
+
+        var result = await service.OpenAsync("AbCip", "{}", CancellationToken.None);
+
+        result.Ok.ShouldBeTrue();
+        result.Token.ShouldBe(universalSession.Token);
+        registry.TryGet(result.Token, out _).ShouldBeTrue();
+    }
+
+    [Fact]
+    public async Task Open_NoBespokeAndCannotBrowse_ReturnsNoBrowserMessage()
+    {
+        var registry = new BrowseSessionRegistry();
+        var service = NewService(registry, new FakeUniversalDriverBrowser()); // CanBrowse=false
+
+        var result = await service.OpenAsync("Modbus", "{}", CancellationToken.None);
+
+        result.Ok.ShouldBeFalse();
+        result.Token.ShouldBe(Guid.Empty);
+        result.Message!.ShouldContain("Modbus");
+    }
+
+    [Fact]
+    public async Task Open_UniversalThrow_ReturnsOkFalseWithMessage()
+    {
+        var registry = new BrowseSessionRegistry();
+        var universal = new FakeUniversalDriverBrowser
+        {
+            CanBrowsePredicate = (_, _) => true,
+            OpenHandler = (_, _, _) => throw new InvalidOperationException("universal-boom"),
+        };
+        var service = NewService(registry, universal);
+
+        var result = await service.OpenAsync("AbCip", "{}", CancellationToken.None);
+
+        result.Ok.ShouldBeFalse();
+        result.Message!.ShouldContain("universal-boom");
+    }
+
+    [Fact]
+    public void CanBrowse_TrueForBespokeType_TrueForUniversalType_FalseOtherwise()
+    {
+        var registry = new BrowseSessionRegistry();
+        var universal = new FakeUniversalDriverBrowser { CanBrowsePredicate = (t, _) => t == "AbCip" };
+        var service = NewService(registry, universal, new FakeDriverBrowser("Galaxy"));
+
+        service.CanBrowse("Galaxy", "{}").ShouldBeTrue(); // bespoke registered
+        service.CanBrowse("AbCip", "{}").ShouldBeTrue();  // universal can serve
+        service.CanBrowse("Modbus", "{}").ShouldBeFalse(); // neither
+    }
+
    [Fact]
    public async Task RootAsync_unknown_token_throws_BrowseSessionNotFoundException()
    {
@@ -0,0 +1,20 @@
+using ZB.MOM.WW.OtOpcUa.Commons.Browsing;
+
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests.Browsing;
+
+/// <summary>Test double for <see cref="IUniversalDriverBrowser"/>. CanBrowse is driven by a
+/// predicate (default: never); OpenAsync delegates to a handler or returns a fresh session.</summary>
+internal sealed class FakeUniversalDriverBrowser : IUniversalDriverBrowser
+{
+    /// <summary>CanBrowse gate. Defaults to "no universal affordance for any type".</summary>
+    public Func<string, string, bool> CanBrowsePredicate { get; init; } = (_, _) => false;
+
+    /// <summary>OpenAsync behavior. Defaults to a fresh FakeBrowseSession.</summary>
+    public Func<string, string, CancellationToken, Task<IBrowseSession>> OpenHandler { get; init; } =
+        (_, _, _) => Task.FromResult<IBrowseSession>(new FakeBrowseSession());
+
+    public bool CanBrowse(string driverType, string configJson) => CanBrowsePredicate(driverType, configJson);
+
+    public Task<IBrowseSession> OpenAsync(string driverType, string configJson, CancellationToken ct) =>
+        OpenHandler(driverType, configJson, ct);
+}