Merge campaign-hover-ui-round: #417 logout audio fix, reveal-timing probe, #418 landblock build pool (login speedup in progress)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/ISSUES.md

@@ -24,6 +24,54 @@ What does NOT go here:
 - Every session: scan OPEN issues at start; promote/close anything we touched during the session before ending.
 - Promoting to a Phase: mark as `DONE (promoted to Phase X)` + commit SHA where the Phase entry landed.
 
+## #418 — Login world load takes ~27 s: publication advances at a flat 32 blocks/s
+
+**Status:** IN-PROGRESS 2026-08-17 — producer half landed (this commit's
+striped `LandblockStreamer` worker pool); the pacer measurably remains on the
+consumer side. **Symptom:** login holds the portal tunnel ~27 s while the
+25×25 window (625 landblocks) drips in at exactly 32 blocks/s
+(`ACDREAM_PROBE_REVEAL_TIMING=1`, probe `695a27b4`; baseline
+totalMs=26728), then render/composites/collision/gate/materialization all
+flip ready in the same millisecond. **Evidence chain:** an A/B with every
+`StreamingWorkBudgetOptions` env ceiling cranked 25–64x changed nothing →
+read as producer-limited (ONE `acdream.streaming.worker` thread,
+~31 ms/block serial). This commit parallelized the producer
+(min(cores−2, 8) striped workers, per-landblock ordering preserved) and
+**disproved that reading**: with 8 workers ALL 625 builds complete in
+~203 ms of wall clock (`ACDREAM_PROBE_TELEPORT=1` BUILD lines
+t=3475390→3475593, dat-lock waited ≤ 12 ms, held 0–13 ms), yet `loaded=`
+still advances at exactly +32/1000 ms and totalMs measured 27395 / 27503
+across two runs of the new binary. **Hypothesis:** the 32/s cadence lives in
+the update-thread admission/publication path (`StreamingController` meter →
+`LandblockPresentationPipeline`), is frame-quantized (an exactly-integer
+per-second rate held for 14+ consecutive seconds — N update ticks per
+landblock at a stable tick rate, e.g. 2 ticks × 64 Hz), and is NOT governed
+by the budget env ceilings (the original A/B and this change now agree on
+that). **Next step:** instrument per-frame meter operations/yields + the
+tunnel frame rate, find which operation stage eats the ensured-progress
+floor, then lift the actual limiter. The producer pool stays: it takes the
+builds off the critical path (23 s → 0.2 s) and is quality-neutral
+(per-landblock ordering, ClearLoads, priority, and disposal semantics
+preserved; a pool of 1 reproduces the old serial behavior,
+regression-tested in `LandblockStreamerPoolTests`).
+
+**Lead-review refinement (2026-08-17, same day):** the identical ~31 ms
+period across BOTH configurations is unlikely to be a coincidence of two
+different limiters — the sharper hypothesis is that ONE ADMITTED
+LANDBLOCK'S update-thread publication itself costs ~31 ms (GPU upload +
+registration + typed-budget accounting as one indivisible admission).
+The 2 ms `MaxUpdateMilliseconds` floor guarantees exactly one admission
+per frame; that admission stretches the frame to ~31 ms; the hold
+therefore runs at ~32 fps and 1 admission/frame × 32 fps = the measured
+flat 32/s — in the OLD binary the serial builder happened to produce at
+the same ~31 ms/block, which masked the admission cost entirely. This
+predicts: (a) tunnel frame time during the hold is ~31 ms (measurable
+from the existing frame profiler), and (b) the fix is splitting or
+off-threading the per-landblock publication cost — NOT raising budgets
+(already disproved twice). `MaxCompletionsPerFrame = 4` (the quality
+line) is a profile SCALE of the same env-tunable options, so it is also
+already exonerated. Verify (a) first next session.
+
 ## #417 — World ambience keeps playing (and re-firing) on the character-select screen after the in-world logoff
 
 **Status:** ✅ FIXED 2026-08-17 (logout-audio round; fix + tests in the same

src/AcDream.App/Composition/SessionPlayerComposition.cs

@@ -425,7 +425,8 @@ internal sealed class SessionPlayerCompositionPhase
             spawnClaimClassifier.IsUnhydratable,
             worldQuiescence,
             streaming,
-            revealRenderResources);
+            revealRenderResources,
+            () => live.WorldState.LoadedLandblockCount);
         Fault(SessionPlayerCompositionPoint.WorldRevealCreated);
 
         return CompleteSessionPlayer(

src/AcDream.App/Streaming/GpuWorldState.cs

@@ -198,6 +198,10 @@ public sealed class GpuWorldState : ILiveEntitySpatialQuery
     /// that need to enumerate entities before the landblock is dropped
     /// (e.g. unregistering dynamic lights on a RemoveLandblock).
     /// </summary>
+    /// <summary>Resident landblock count — reveal-timing probe progress
+    /// lines only (<see cref="RevealTimingProbe"/>).</summary>
+    public int LoadedLandblockCount => _loaded.Count;
+
     public bool TryGetLandblock(uint landblockId, out LoadedLandblock? lb)
     {
         if (_loaded.TryGetValue(landblockId, out var found))

src/AcDream.App/Streaming/LandblockStreamer.cs

@@ -16,19 +16,24 @@ namespace AcDream.App.Streaming;
 /// per OnUpdate.
 ///
 /// <para>
-/// <b>Thread model (Phase A.5 T11+):</b> <see cref="Start"/> spawns a
-/// dedicated background worker thread. <see cref="EnqueueLoad"/> and
-/// <see cref="EnqueueUnload"/> write non-blocking to the inbox
-/// <see cref="Channel{T}"/>; the worker drains it and posts
-/// <see cref="LandblockStreamResult"/> records to the outbox.
+/// <b>Thread model (#418):</b> <see cref="Start"/> spawns a small pool of
+/// dedicated background worker threads (default
+/// <see cref="DefaultWorkerCount"/>; the single-worker degenerate case is
+/// the pre-#418 Phase A.5 T11+ shape). Jobs are striped across per-worker
+/// lanes by landblock id, so every job for one landblock id executes on
+/// one lane in enqueue order — a Load and Unload for the same id can never
+/// race on two workers. <see cref="EnqueueLoad"/> and
+/// <see cref="EnqueueUnload"/> write non-blocking to the owning lane's
+/// inbox <see cref="Channel{T}"/>; each worker drains its lane and posts
+/// <see cref="LandblockStreamResult"/> records to the shared outbox.
 /// </para>
 ///
 /// <para>
 /// <b>DatCollection thread safety</b> is provided by the caller:
 /// GameWindow's <c>_datLock</c> (Phase A.5 T10) serialises all
 /// <c>DatCollection.Get&lt;T&gt;</c> calls. Both factory closures passed at
-/// construction acquire that lock before reading dats. The worker never
-/// touches <c>DatCollection</c> directly — it only calls the factories.
+/// construction acquire that lock before reading dats. The workers never
+/// touch <c>DatCollection</c> directly — they only call the factories.
 /// </para>
 ///
 /// <para>
@@ -40,7 +45,10 @@ namespace AcDream.App.Streaming;
 /// <remarks>
 /// Threading: <see cref="DrainCompletions"/> must be called from a single
 /// consumer thread (the render thread in production). All other public
-/// methods are thread-safe.
+/// methods are thread-safe. Completion arrival order is preserved per
+/// landblock id (per lane); across different landblocks it is arbitrary,
+/// which the single consumer already tolerates — the StreamingController's
+/// admission classifies each result independently into per-priority FIFOs.
 /// </remarks>
 /// </summary>
 public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
@@ -52,14 +60,23 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
     /// </summary>
     public const int DefaultDrainBatchSize = 4;
 
+    /// <summary>
+    /// Default build worker pool size: leave two cores for the render and
+    /// update threads, cap at 8 (the login window's ~625 builds saturate
+    /// well before that), floor 1 (the pre-#418 single-worker shape).
+    /// </summary>
+    public static int DefaultWorkerCount =>
+        Math.Max(1, Math.Min(Environment.ProcessorCount - 2, 8));
+
     private readonly Func<LandblockBuildRequest, LandblockBuild?> _loadLandblock;
     private readonly bool _supportsRequestOrigin;
     private readonly Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?> _buildMeshOrNull;
-    private readonly Channel<LandblockStreamJob> _inbox;
+    private readonly Channel<LandblockStreamJob>[] _lanes;
     private readonly Channel<LandblockStreamResult> _outbox;
     private readonly CancellationTokenSource _cancel = new();
     private readonly object _inboxGate = new();
-    private Thread? _worker;
+    private Thread[]? _workers;
+    private int _activeWorkers;
     private Exception? _workerFailure;
     private int _completionBacklog;
     private int _disposed;
@@ -74,17 +91,31 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
     private LandblockStreamer(
         Func<LandblockBuildRequest, LandblockBuild?> loadLandblock,
         Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull,
-        bool supportsRequestOrigin)
+        bool supportsRequestOrigin,
+        int? workerCount)
     {
+        if (workerCount is < 1)
+        {
+            throw new ArgumentOutOfRangeException(
+                nameof(workerCount),
+                workerCount,
+                "The landblock build pool needs at least one worker.");
+        }
         _loadLandblock = loadLandblock;
         _supportsRequestOrigin = supportsRequestOrigin;
         // Default: no mesh build (returns null → Failed result). Production
         // wires in LandblockMesh.Build via the T12 construction site.
         _buildMeshOrNull = buildMeshOrNull ?? ((_, _) => null);
-        _inbox = Channel.CreateUnbounded<LandblockStreamJob>(
-            new UnboundedChannelOptions { SingleReader = true, SingleWriter = false });
+        int lanes = workerCount ?? DefaultWorkerCount;
+        _lanes = new Channel<LandblockStreamJob>[lanes];
+        for (int i = 0; i < lanes; i++)
+        {
+            _lanes[i] = Channel.CreateUnbounded<LandblockStreamJob>(
+                new UnboundedChannelOptions { SingleReader = true, SingleWriter = false });
+        }
+        // SingleWriter = false: every pool worker posts completions.
         _outbox = Channel.CreateUnbounded<LandblockStreamResult>(
-            new UnboundedChannelOptions { SingleReader = true, SingleWriter = true });
+            new UnboundedChannelOptions { SingleReader = true, SingleWriter = false });
     }
 
     /// <summary>
@@ -94,8 +125,9 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
     /// </summary>
     public static LandblockStreamer CreateForRequests(
         Func<LandblockBuildRequest, LandblockBuild?> loadLandblock,
-        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null) =>
-        new(loadLandblock, buildMeshOrNull, supportsRequestOrigin: true);
+        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null,
+        int? workerCount = null) =>
+        new(loadLandblock, buildMeshOrNull, supportsRequestOrigin: true, workerCount);
 
     /// <summary>
     /// Compatibility constructor for build factories that predate the
@@ -103,13 +135,15 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
     /// </summary>
     public LandblockStreamer(
         Func<uint, LandblockStreamJobKind, LandblockBuild?> loadLandblock,
-        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null)
+        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null,
+        int? workerCount = null)
         : this(
             request => loadLandblock(request.LandblockId, request.Kind) is { } build
                 ? build
                 : null,
             buildMeshOrNull,
-            supportsRequestOrigin: false)
+            supportsRequestOrigin: false,
+            workerCount)
     {
     }
 
@@ -120,13 +154,15 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
     /// </summary>
     public LandblockStreamer(
         Func<uint, LandblockStreamJobKind, LoadedLandblock?> loadLandblock,
-        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null)
+        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null,
+        int? workerCount = null)
         : this(
             request => loadLandblock(request.LandblockId, request.Kind) is { } landblock
                 ? new LandblockBuild(landblock, Origin: request.Origin)
                 : null,
             buildMeshOrNull,
-            supportsRequestOrigin: false)
+            supportsRequestOrigin: false,
+            workerCount)
     {
     }
 
@@ -138,19 +174,40 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
     /// </summary>
     public LandblockStreamer(
         Func<uint, LoadedLandblock?> loadLandblock,
-        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null)
+        Func<uint, LoadedLandblock?, AcDream.Core.Terrain.LandblockMeshData?>? buildMeshOrNull = null,
+        int? workerCount = null)
         : this(
             request => loadLandblock(request.LandblockId) is { } landblock
                 ? new LandblockBuild(landblock, Origin: request.Origin)
                 : null,
             buildMeshOrNull,
-            supportsRequestOrigin: false)
+            supportsRequestOrigin: false,
+            workerCount)
     {
     }
 
+    /// <summary>Configured pool size (also the lane count).</summary>
+    internal int WorkerCount => _lanes.Length;
+
     /// <summary>
-    /// Activate the dedicated background worker thread. Idempotent and
-    /// thread-safe: concurrent callers will only spawn one worker; subsequent
+    /// Lane (worker) that owns every job for <paramref name="landblockId"/>.
+    /// Landblock ids carry their identity in the high 16 bits (0xXXYYFFFF —
+    /// the low word is constant across ids), so the id is mixed with a
+    /// Knuth multiplicative hash before reduction; a bare modulo would map
+    /// every id to one lane. Internal so tests can construct deterministic
+    /// per-lane contention.
+    /// </summary>
+    internal int LaneFor(uint landblockId)
+    {
+        if (_lanes.Length == 1)
+            return 0;
+        uint mixed = (landblockId >> 16) * 2654435761u;
+        return (int)(mixed % (uint)_lanes.Length);
+    }
+
+    /// <summary>
+    /// Activate the dedicated background worker threads. Idempotent and
+    /// thread-safe: concurrent callers will only spawn one pool; subsequent
     /// calls are no-ops. Serialized with disposal so a worker can never start
     /// after the owning DAT lifetime has been released.
     /// </summary>
@@ -160,16 +217,27 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
         {
             if (System.Threading.Volatile.Read(ref _disposed) != 0)
                 throw new ObjectDisposedException(nameof(LandblockStreamer));
-            if (_worker is not null)
+            if (_workers is not null)
                 return;
 
-            var worker = new Thread(WorkerLoop)
+            var workers = new Thread[_lanes.Length];
+            // Armed before any worker can run so the last worker to exit —
+            // however fast — is the one that completes the outbox.
+            System.Threading.Volatile.Write(ref _activeWorkers, workers.Length);
+            for (int i = 0; i < workers.Length; i++)
             {
-                IsBackground = true,
-                Name = "acdream.streaming.worker",
-            };
-            worker.Start();
-            _worker = worker;
+                int lane = i;
+                workers[i] = new Thread(() => WorkerLoop(lane))
+                {
+                    IsBackground = true,
+                    Name = workers.Length == 1
+                        ? "acdream.streaming.worker"
+                        : $"acdream.streaming.worker.{lane}",
+                };
+            }
+            foreach (Thread worker in workers)
+                worker.Start();
+            _workers = workers;
         }
     }
 
@@ -236,12 +304,15 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
 
     /// <summary>
     /// Cancel every queued-but-not-started Load. Posts a
-    /// <see cref="LandblockStreamJob.ClearLoads"/> control job which the worker
-    /// honours at read time, dropping all pending Loads from both priority
-    /// queues (Unloads survive). Used on the dungeon-entry edge to abort the
-    /// in-flight 25×25 neighbor window so the ~129 ocean-grid dungeons never
-    /// finish loading (#133 FPS). Loads the worker has ALREADY dequeued still
-    /// complete; the StreamingController's collapsed-sweep unloads those few.
+    /// <see cref="LandblockStreamJob.ClearLoads"/> control job to EVERY lane
+    /// (one atomic broadcast under the enqueue gate, so a load enqueued
+    /// before this call is ordered ahead of its lane's ClearLoads copy and
+    /// dropped) which each worker honours at read time, dropping all pending
+    /// Loads from both of its priority queues (Unloads survive). Used on the
+    /// dungeon-entry edge to abort the in-flight 25×25 neighbor window so the
+    /// ~129 ocean-grid dungeons never finish loading (#133 FPS). Loads a
+    /// worker has ALREADY dequeued still complete (up to one per worker);
+    /// the StreamingController's collapsed-sweep unloads those few.
     /// </summary>
     public void ClearPendingLoads()
     {
@@ -250,18 +321,28 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
 
     private void WriteJob(LandblockStreamJob job)
     {
-        // Serialize the writer's terminal transition with enqueue. Without
-        // this small lifecycle gate a worker crash could complete the channel
+        // Serialize the writers' terminal transition with enqueue. Without
+        // this small lifecycle gate a worker crash could complete a lane
         // between the caller's state check and TryWrite, silently dropping a
-        // landblock request. Enqueues are destination-boundary events, not a
-        // per-frame hot path.
+        // landblock request. The same gate makes the ClearLoads broadcast
+        // atomic with respect to concurrent enqueues. Enqueues are
+        // destination-boundary events, not a per-frame hot path.
         lock (_inboxGate)
         {
             if (System.Threading.Volatile.Read(ref _disposed) != 0)
                 throw new ObjectDisposedException(nameof(LandblockStreamer));
             if (_workerFailure is { } failure)
-                throw new InvalidOperationException("The landblock streaming worker has terminated.", failure);
-            if (!_inbox.Writer.TryWrite(job))
+                throw new InvalidOperationException("A landblock streaming worker has terminated.", failure);
+            if (job is LandblockStreamJob.ClearLoads)
+            {
+                foreach (Channel<LandblockStreamJob> lane in _lanes)
+                {
+                    if (!lane.Writer.TryWrite(job))
+                        throw new InvalidOperationException("The landblock streaming inbox is no longer accepting work.");
+                }
+                return;
+            }
+            if (!_lanes[LaneFor(job.LandblockId)].Writer.TryWrite(job))
                 throw new InvalidOperationException("The landblock streaming inbox is no longer accepting work.");
         }
     }
@@ -308,8 +389,9 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
             System.Threading.Interlocked.Increment(ref _completionBacklog);
     }
 
-    private void WorkerLoop()
+    private void WorkerLoop(int laneIndex)
     {
+        ChannelReader<LandblockStreamJob> inbox = _lanes[laneIndex].Reader;
         var highPriority = new Queue<LandblockStreamJob>();
         var lowPriority = new Queue<LandblockStreamJob>();
 
@@ -325,12 +407,12 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
             {
                 if (highPriority.Count == 0 &&
                     lowPriority.Count == 0 &&
-                    !_inbox.Reader.WaitToReadAsync(_cancel.Token).AsTask().GetAwaiter().GetResult())
+                    !inbox.WaitToReadAsync(_cancel.Token).AsTask().GetAwaiter().GetResult())
                 {
                     break;
                 }
 
-                while (_inbox.Reader.TryRead(out var job))
+                while (inbox.TryRead(out var job))
                 {
                     if (job is LandblockStreamJob.ClearLoads)
                     {
@@ -358,17 +440,39 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
         catch (Exception ex)
         {
             // Last-ditch: surface via outbox so the caller at least sees
-            // something. We never retry a crashed worker.
+            // something. We never retry a crashed worker; any worker crash
+            // terminates the pool (matching the single-worker contract that
+            // a crash ends all job processing). A sibling that merely
+            // observed the crashed worker's lane completion (the wrapped
+            // ChannelClosedException) exits quietly instead of reporting a
+            // second, spurious crash.
+            bool cascade;
             lock (_inboxGate)
             {
-                _workerFailure = ex;
-                _inbox.Writer.TryComplete(ex);
+                cascade = _workerFailure is not null && ex is ChannelClosedException;
+                _workerFailure ??= ex;
+                foreach (Channel<LandblockStreamJob> lane in _lanes)
+                    lane.Writer.TryComplete(ex);
+            }
+            if (!cascade)
+            {
+                PublishResult(new LandblockStreamResult.WorkerCrashed(
+                    _lanes.Length == 1
+                        ? ex.ToString()
+                        : $"worker {laneIndex}: {ex}"));
+                // Stop the sibling workers. Safe against Dispose: its
+                // CTS disposal only happens after every worker (this one
+                // included) has been joined.
+                _cancel.Cancel();
             }
-            PublishResult(new LandblockStreamResult.WorkerCrashed(ex.ToString()));
         }
         finally
         {
-            _outbox.Writer.TryComplete();
+            // The outbox has N writers; only the last worker out may
+            // complete it, or a crashed worker would silently drop the
+            // still-running workers' completions.
+            if (Interlocked.Decrement(ref _activeWorkers) == 0)
+                _outbox.Writer.TryComplete();
         }
     }
 
@@ -386,8 +490,9 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
             // older queued LoadFar for the same landblock: LoadNear obviously
             // loads everything, and PromoteToNear now carries mesh data so the
             // render thread can run the full near-tier apply side effects. If a
-            // LoadFar is already being processed, the single worker naturally
-            // finishes it before the promotion is dequeued.
+            // LoadFar is already being processed, the owning lane's worker
+            // naturally finishes it before the promotion is dequeued (every
+            // job for one landblock id lives on one lane).
             RemoveLowPriorityJobsForLandblock(
                 lowPriority,
                 high.LandblockId,
@@ -540,11 +645,18 @@ public sealed class LandblockStreamer : IDisposable, ILandblockCompletionSource
             System.Threading.Interlocked.Exchange(ref _disposed, 1);
             _cancel.Cancel();
             lock (_inboxGate)
-                _inbox.Writer.TryComplete();
+            {
+                foreach (Channel<LandblockStreamJob> lane in _lanes)
+                    lane.Writer.TryComplete();
+            }
             // The owner releases the memory-mapped DAT immediately after this
-            // object. Join the actual worker without a grace-period timeout so
-            // no native read can survive into that teardown.
-            _worker?.Join();
+            // object. Join every actual worker without a grace-period timeout
+            // so no native read can survive into that teardown.
+            if (_workers is { } workers)
+            {
+                foreach (Thread worker in workers)
+                    worker.Join();
+            }
             _cancel.Dispose();
             _disposeCompleted = true;
         }

src/AcDream.App/Streaming/RevealTimingProbe.cs

@@ -0,0 +1,155 @@
+using System.Diagnostics;
+using AcDream.Runtime;
+
+namespace AcDream.App.Streaming;
+
+/// <summary>
+/// <c>ACDREAM_PROBE_REVEAL_TIMING=1</c> (see
+/// <see cref="StreamingDiagnostics.ProbeRevealTiming"/>): wall-clock
+/// attribution of one login/portal hold. Emits <c>[reveal-timing]</c> lines:
+///
+/// <list type="bullet">
+/// <item><c>event=begin</c> — the hold starts, with the required window and
+/// its landblock count.</item>
+/// <item><c>event=render-ready / composites-ready / collision-ready /
+/// gate-ready / materialized</c> — first-true edges with elapsed ms. The
+/// readiness barrier OBSERVES the dimensions serially (composites are only
+/// evaluated once render is ready, collision once both are), so each edge's
+/// delta over the previous one is that dimension's observed TAIL, not its
+/// total concurrent cost — the progress lines carry the concurrency
+/// shape.</item>
+/// <item>1 Hz progress — elapsed, the three flags, and the resident
+/// landblock count, so a budget-paced linear drip is visually obvious in the
+/// log.</item>
+/// <item><c>SUMMARY</c> once at the viewport reveal — the per-edge
+/// timeline on one line.</item>
+/// </list>
+///
+/// Diagnostic-only: never constructed unless the probe env is set, changes
+/// no behavior, and costs one branch per <c>Evaluate</c> poll otherwise.
+/// </summary>
+internal sealed class RevealTimingProbe
+{
+    private readonly Func<int>? _loadedLandblockCount;
+    private readonly Stopwatch _clock = new();
+    private long _generation;
+    private string _kind = "";
+    private int _windowLandblocks;
+    private bool _render;
+    private bool _composites;
+    private bool _collision;
+    private bool _gateReady;
+    private bool _materialized;
+    private bool _summarized;
+    private long _renderMs = -1;
+    private long _compositesMs = -1;
+    private long _collisionMs = -1;
+    private long _gateReadyMs = -1;
+    private long _materializedMs = -1;
+    private long _lastProgressMs;
+
+    public RevealTimingProbe(Func<int>? loadedLandblockCount) =>
+        _loadedLandblockCount = loadedLandblockCount;
+
+    public void Begin(
+        string kind,
+        long generation,
+        uint destinationCell,
+        in StreamingRevealWindow window)
+    {
+        _generation = generation;
+        _kind = kind;
+        int side = window.FarRadius * 2 + 1;
+        _windowLandblocks = side * side;
+        _render = false;
+        _composites = false;
+        _collision = false;
+        _gateReady = false;
+        _materialized = false;
+        _summarized = false;
+        _renderMs = -1;
+        _compositesMs = -1;
+        _collisionMs = -1;
+        _gateReadyMs = -1;
+        _materializedMs = -1;
+        _lastProgressMs = 0;
+        _clock.Restart();
+        Console.WriteLine(
+            $"[reveal-timing] event=begin kind={kind} gen={generation} "
+            + $"cell=0x{destinationCell:X8} window={window.NearRadius}/"
+            + $"{window.FarRadius} landblocks={_windowLandblocks} "
+            + $"loaded={_loadedLandblockCount?.Invoke() ?? -1}");
+    }
+
+    public void Observe(
+        in WorldRevealReadinessSnapshot readiness,
+        in RuntimePortalSnapshot portal)
+    {
+        if (_generation == 0 || portal.Generation != _generation)
+            return;
+
+        long elapsed = _clock.ElapsedMilliseconds;
+        if (!_render && readiness.IsRenderNeighborhoodReady)
+        {
+            _render = true;
+            _renderMs = elapsed;
+            Edge("render-ready", elapsed);
+        }
+        if (!_composites && readiness.AreCompositeTexturesReady)
+        {
+            _composites = true;
+            _compositesMs = elapsed;
+            Edge("composites-ready", elapsed);
+        }
+        if (!_collision && readiness.IsCollisionReady)
+        {
+            _collision = true;
+            _collisionMs = elapsed;
+            Edge("collision-ready", elapsed);
+        }
+        if (!_gateReady && readiness.IsReady)
+        {
+            _gateReady = true;
+            _gateReadyMs = elapsed;
+            Edge("gate-ready", elapsed);
+        }
+        if (!_materialized && portal.Materialized)
+        {
+            _materialized = true;
+            _materializedMs = elapsed;
+            Edge("materialized", elapsed);
+        }
+
+        if (!_summarized && portal.WorldViewportObserved)
+        {
+            _summarized = true;
+            Console.WriteLine(
+                $"[reveal-timing] SUMMARY kind={_kind} gen={_generation} "
+                + $"totalMs={elapsed} renderMs={_renderMs} "
+                + $"compositesMs={_compositesMs} collisionMs={_collisionMs} "
+                + $"gateReadyMs={_gateReadyMs} "
+                + $"materializedMs={_materializedMs} "
+                + $"landblocks={_windowLandblocks}");
+            return;
+        }
+
+        if (!_summarized && elapsed - _lastProgressMs >= 1000)
+        {
+            _lastProgressMs = elapsed;
+            Console.WriteLine(
+                $"[reveal-timing] elapsedMs={elapsed} "
+                + $"render={(_render ? 1 : 0)} "
+                + $"composites={(_composites ? 1 : 0)} "
+                + $"collision={(_collision ? 1 : 0)} "
+                + $"loaded={_loadedLandblockCount?.Invoke() ?? -1}"
+                + $"/{_windowLandblocks}");
+        }
+    }
+
+    private void Edge(string name, long elapsed) =>
+        Console.WriteLine(
+            $"[reveal-timing] event={name} kind={_kind} gen={_generation} "
+            + $"elapsedMs={elapsed} "
+            + $"loaded={_loadedLandblockCount?.Invoke() ?? -1}"
+            + $"/{_windowLandblocks}");
+}

src/AcDream.App/Streaming/StreamingDiagnostics.cs

@@ -51,6 +51,19 @@ internal static class StreamingDiagnostics
             far);
     }
 
+    /// <summary>
+    /// Login-load measurement probe (2026-08-17): when set, the reveal
+    /// coordinator emits a <c>[reveal-timing]</c> wall-clock timeline for
+    /// every login/portal hold — per-dimension first-ready edges
+    /// (render neighborhood, composite textures, collision), 1 Hz progress
+    /// with the resident-landblock count, and one summary line at the
+    /// viewport reveal — so optimization targets the measured dominant
+    /// phase instead of a guess. Diagnostic-only: not a user setting, not
+    /// persisted, no behavior change.
+    /// </summary>
+    public static bool ProbeRevealTiming { get; } =
+        Environment.GetEnvironmentVariable("ACDREAM_PROBE_REVEAL_TIMING") == "1";
+
     /// <summary>
     /// The floor is 1, not 0. An outdoor destination's acknowledgement must
     /// carry <c>RequiredRenderRadius &gt;= 1</c> or

src/AcDream.App/Streaming/WorldRevealCoordinator.cs

@@ -68,6 +68,7 @@ internal sealed class WorldRevealCoordinator
     private readonly IWorldRevealStreamingScheduler? _streaming;
     private readonly IWorldRevealRenderResourceScheduler? _renderResources;
     private readonly List<HostProjection> _hostProjections = [];
+    private readonly RevealTimingProbe? _timing;
     private bool _hostRetryActive;
     private bool _hostRetryRequested;
 
@@ -83,7 +84,8 @@ internal sealed class WorldRevealCoordinator
         Func<uint, bool> isSpawnClaimUnhydratable,
         WorldGenerationQuiescence? quiescence = null,
         IWorldRevealStreamingScheduler? streaming = null,
-        IWorldRevealRenderResourceScheduler? renderResources = null)
+        IWorldRevealRenderResourceScheduler? renderResources = null,
+        Func<int>? loadedLandblockCount = null)
     {
         _transit = transit ?? throw new ArgumentNullException(nameof(transit));
         _readiness = new WorldRevealReadinessBarrier(
@@ -98,6 +100,8 @@ internal sealed class WorldRevealCoordinator
         _quiescence = quiescence;
         _streaming = streaming;
         _renderResources = renderResources;
+        if (StreamingDiagnostics.ProbeRevealTiming)
+            _timing = new RevealTimingProbe(loadedLandblockCount);
     }
 
     public RuntimePortalSnapshot Snapshot => _transit.Snapshot;
@@ -117,6 +121,11 @@ internal sealed class WorldRevealCoordinator
             _quiescence?.CaptureBegin() ?? default;
         _readiness.Begin();
         long generation = _transit.BeginLoginReveal(destinationCell);
+        _timing?.Begin(
+            "login",
+            generation,
+            destinationCell,
+            _readiness.RequiredWindow(destinationCell));
         BeginHostLifetime(
             generation,
             destinationCell,
@@ -151,6 +160,11 @@ internal sealed class WorldRevealCoordinator
         }
 
         _readiness.Begin();
+        _timing?.Begin(
+            "portal",
+            generation,
+            destinationCell,
+            _readiness.RequiredWindow(destinationCell));
         BeginHostLifetime(
             generation,
             destinationCell,
@@ -195,6 +209,7 @@ internal sealed class WorldRevealCoordinator
         WorldRevealReadinessSnapshot snapshot = _readiness.Evaluate(destinationCell);
         ReconcileDestinationReservationRadius(snapshot);
         RuntimePortalSnapshot portal = _transit.Snapshot;
+        _timing?.Observe(snapshot, portal);
         if (portal.Generation != 0)
         {
             _transit.AcknowledgeDestinationReadiness(

tests/AcDream.App.Tests/Streaming/LandblockBuildOriginTests.cs

@@ -118,13 +118,17 @@ public sealed class LandblockBuildOriginTests
         var observed = new List<LandblockBuildRequest>();
         var firstOrigin = new LandblockBuildOrigin(0xA9, 0xB4);
         var secondOrigin = new LandblockBuildOrigin(0x71, 0xEC);
+        // workerCount: 1 — the ordered `observed`/completion asserts span two
+        // DIFFERENT landblock ids; only the serial degenerate pool (#418)
+        // guarantees that global order (per-id order is the pool contract).
         using var streamer = LandblockStreamer.CreateForRequests(
             loadLandblock: request =>
             {
                 observed.Add(request);
                 return EmptyBuild(request.LandblockId, request.Origin);
             },
-            buildMeshOrNull: (_, _) => EmptyMesh());
+            buildMeshOrNull: (_, _) => EmptyMesh(),
+            workerCount: 1);
 
         streamer.EnqueueLoad(new LandblockBuildRequest(
             0xA9B4FFFFu,

tests/AcDream.App.Tests/Streaming/LandblockStreamerPoolTests.cs

@@ -0,0 +1,431 @@
+using System.Collections.Concurrent;
+using AcDream.App.Streaming;
+using AcDream.Core.World;
+using DatReaderWriter.DBObjs;
+
+namespace AcDream.App.Tests.Streaming;
+
+/// <summary>
+/// #418 build-worker-pool contract tests. The pool stripes jobs across
+/// per-worker lanes by landblock id, so the contract is: per-landblock
+/// enqueue order is execution (and completion-arrival) order, ClearLoads
+/// supersedes every load queued before it on every lane, Near-tier jobs run
+/// before Far-tier ones within a lane, a pool of one reproduces the serial
+/// pre-#418 behavior, and disposal joins every worker.
+/// </summary>
+public sealed class LandblockStreamerPoolTests
+{
+    private const int SpinTimeoutMs = 10_000;
+    private const int SpinStepMs = 10;
+
+    private static AcDream.Core.Terrain.LandblockMeshData StubMesh() =>
+        new(
+            Array.Empty<AcDream.Core.Terrain.TerrainVertex>(),
+            Array.Empty<uint>());
+
+    private static LoadedLandblock StubLandblock(uint id) =>
+        new(id, new LandBlock(), Array.Empty<WorldEntity>());
+
+    /// <summary>
+    /// Produce a landblock id (retail 0xXXYYFFFF shape) owned by
+    /// <paramref name="lane"/>, distinct from every id in
+    /// <paramref name="taken"/>.
+    /// </summary>
+    private static uint IdInLane(LandblockStreamer streamer, int lane, HashSet<uint> taken)
+    {
+        for (uint x = 0; x < 256; x++)
+        {
+            for (uint y = 0; y < 256; y++)
+            {
+                uint id = (x << 24) | (y << 16) | 0xFFFFu;
+                if (streamer.LaneFor(id) == lane && taken.Add(id))
+                    return id;
+            }
+        }
+        throw new InvalidOperationException($"No landblock id maps to lane {lane}.");
+    }
+
+    private static async Task<List<LandblockStreamResult>> DrainCountAsync(
+        LandblockStreamer streamer,
+        int count,
+        int timeoutMs = SpinTimeoutMs)
+    {
+        var results = new List<LandblockStreamResult>(count);
+        for (int i = 0; i < timeoutMs / SpinStepMs && results.Count < count; i++)
+        {
+            results.AddRange(streamer.DrainCompletions(count - results.Count));
+            if (results.Count < count)
+                await Task.Delay(SpinStepMs);
+        }
+
+        Assert.Equal(count, results.Count);
+        return results;
+    }
+
+    [Fact]
+    public void WorkerCount_DefaultsBoundedFloorsAtOneAndRejectsZero()
+    {
+        Assert.InRange(LandblockStreamer.DefaultWorkerCount, 1, 8);
+
+        using var defaulted = new LandblockStreamer(loadLandblock: _ => null);
+        Assert.Equal(LandblockStreamer.DefaultWorkerCount, defaulted.WorkerCount);
+
+        using var explicitThree = new LandblockStreamer(
+            loadLandblock: _ => null,
+            buildMeshOrNull: null,
+            workerCount: 3);
+        Assert.Equal(3, explicitThree.WorkerCount);
+
+        Assert.Throws<ArgumentOutOfRangeException>(() => new LandblockStreamer(
+            loadLandblock: _ => null,
+            buildMeshOrNull: null,
+            workerCount: 0));
+    }
+
+    [Fact]
+    public void LaneAssignment_SpreadsRealWindowIdsAcrossLanes()
+    {
+        // Landblock ids carry their identity in the high word (0xXXYYFFFF);
+        // a bare modulo of the raw id would put EVERY id in one lane. Guard
+        // the mixed hash: a realistic 25x25 login window must engage more
+        // than one lane of an 8-lane pool.
+        using var streamer = new LandblockStreamer(
+            loadLandblock: _ => null,
+            buildMeshOrNull: null,
+            workerCount: 8);
+
+        var lanes = new HashSet<int>();
+        for (uint x = 0xA0; x < 0xA0 + 25; x++)
+            for (uint y = 0xB0; y < 0xB0 + 25; y++)
+                lanes.Add(streamer.LaneFor((x << 24) | (y << 16) | 0xFFFFu));
+
+        Assert.True(
+            lanes.Count > 1,
+            $"25x25 window ids collapsed into {lanes.Count} lane(s).");
+    }
+
+    [Fact]
+    public async Task PerLandblockJobs_ExecuteInEnqueueOrder_UnderPoolContention()
+    {
+        const int idCount = 12;
+        const int jobsPerId = 8; // alternating LoadFar / Unload
+        int loaderCalls = 0;
+
+        using var streamer = new LandblockStreamer(
+            loadLandblock: (uint id, LandblockStreamJobKind _) =>
+            {
+                // Shake worker scheduling so a per-landblock ordering bug
+                // would actually interleave.
+                if (Interlocked.Increment(ref loaderCalls) % 3 == 0)
+                    Thread.Sleep(1);
+                return StubLandblock(id);
+            },
+            buildMeshOrNull: (_, _) => StubMesh(),
+            workerCount: 4);
+        streamer.Start();
+
+        var ids = new uint[idCount];
+        for (uint i = 0; i < idCount; i++)
+            ids[i] = ((0x30u + i) << 24) | ((0x40u + i) << 16) | 0xFFFFu;
+
+        // Round-robin across ids while the pool is already running, so jobs
+        // for the same id repeatedly queue behind and race with other lanes.
+        ulong generation = 0;
+        for (int job = 0; job < jobsPerId; job++)
+        {
+            foreach (uint id in ids)
+            {
+                generation++;
+                if (job % 2 == 0)
+                    streamer.EnqueueLoad(id, LandblockStreamJobKind.LoadFar, generation);
+                else
+                    streamer.EnqueueUnload(id, generation);
+            }
+        }
+
+        List<LandblockStreamResult> results =
+            await DrainCountAsync(streamer, idCount * jobsPerId);
+
+        foreach (uint id in ids)
+        {
+            var perId = results.Where(result => result.LandblockId == id).ToList();
+            Assert.Equal(jobsPerId, perId.Count);
+            // Completion arrival order per landblock id must be the enqueue
+            // order: alternating Loaded/Unloaded with strictly increasing
+            // generations.
+            for (int i = 0; i < perId.Count; i++)
+            {
+                if (i % 2 == 0)
+                    Assert.IsType<LandblockStreamResult.Loaded>(perId[i]);
+                else
+                    Assert.IsType<LandblockStreamResult.Unloaded>(perId[i]);
+                if (i > 0)
+                {
+                    Assert.True(
+                        perId[i].Generation > perId[i - 1].Generation,
+                        $"LB 0x{id:X8}: result {i} (gen {perId[i].Generation}) arrived " +
+                        $"after gen {perId[i - 1].Generation} out of enqueue order.");
+                }
+            }
+        }
+    }
+
+    [Fact]
+    public async Task ClearPendingLoads_DropsQueuedLoadsAcrossAllLanes()
+    {
+        const int workerCount = 4;
+        using var release = new ManualResetEventSlim();
+        using var entered = new CountdownEvent(workerCount);
+        var loadedIds = new ConcurrentBag<uint>();
+        var blockerIds = new HashSet<uint>();
+
+        using var streamer = new LandblockStreamer(
+            loadLandblock: (uint id, LandblockStreamJobKind _) =>
+            {
+                loadedIds.Add(id);
+                bool isBlocker;
+                lock (blockerIds)
+                    isBlocker = blockerIds.Contains(id);
+                if (isBlocker)
+                {
+                    entered.Signal();
+                    release.Wait();
+                }
+                return StubLandblock(id);
+            },
+            buildMeshOrNull: (_, _) => StubMesh(),
+            workerCount: workerCount);
+
+        var taken = new HashSet<uint>();
+        var victimIds = new List<uint>();
+        var unloadIds = new List<uint>();
+        var survivorIds = new List<uint>();
+        lock (blockerIds)
+        {
+            for (int lane = 0; lane < workerCount; lane++)
+            {
+                blockerIds.Add(IdInLane(streamer, lane, taken));
+                victimIds.Add(IdInLane(streamer, lane, taken));
+                victimIds.Add(IdInLane(streamer, lane, taken));
+                unloadIds.Add(IdInLane(streamer, lane, taken));
+                survivorIds.Add(IdInLane(streamer, lane, taken));
+            }
+        }
+
+        streamer.Start();
+        lock (blockerIds)
+        {
+            foreach (uint id in blockerIds)
+                streamer.EnqueueLoad(id, LandblockStreamJobKind.LoadFar);
+        }
+        // Every worker is now inside its blocker build; everything below
+        // queues behind them, one lane each.
+        Assert.True(entered.Wait(TimeSpan.FromSeconds(5)));
+
+        foreach (uint id in victimIds)
+            streamer.EnqueueLoad(id, LandblockStreamJobKind.LoadFar);
+        foreach (uint id in unloadIds)
+            streamer.EnqueueUnload(id);
+
+        // Must supersede every load queued above on EVERY lane, while the
+        // queued unloads survive.
+        streamer.ClearPendingLoads();
+
+        foreach (uint id in survivorIds)
+            streamer.EnqueueLoad(id, LandblockStreamJobKind.LoadFar);
+
+        release.Set();
+
+        // Expected completions: 4 blocker Loaded + 4 Unloaded + 4 survivor
+        // Loaded. The victims produce nothing.
+        List<LandblockStreamResult> results =
+            await DrainCountAsync(streamer, workerCount * 3);
+
+        var loadedResultIds = results
+            .OfType<LandblockStreamResult.Loaded>()
+            .Select(result => result.LandblockId)
+            .ToHashSet();
+        var unloadedResultIds = results
+            .OfType<LandblockStreamResult.Unloaded>()
+            .Select(result => result.LandblockId)
+            .ToHashSet();
+
+        lock (blockerIds)
+        {
+            foreach (uint id in blockerIds)
+                Assert.Contains(id, loadedResultIds);
+        }
+        foreach (uint id in survivorIds)
+            Assert.Contains(id, loadedResultIds);
+        foreach (uint id in unloadIds)
+            Assert.Contains(id, unloadedResultIds);
+        foreach (uint id in victimIds)
+        {
+            Assert.DoesNotContain(id, loadedResultIds);
+            Assert.DoesNotContain(id, loadedIds);
+        }
+    }
+
+    [Fact]
+    public async Task NearTierJobs_RunBeforeQueuedFarJobs_WithinEachLane()
+    {
+        const int workerCount = 3;
+        using var release = new ManualResetEventSlim();
+        using var entered = new CountdownEvent(workerCount);
+        var executionOrder = new ConcurrentQueue<uint>();
+        var blockerIds = new HashSet<uint>();
+
+        using var streamer = new LandblockStreamer(
+            loadLandblock: (uint id, LandblockStreamJobKind _) =>
+            {
+                bool isBlocker;
+                lock (blockerIds)
+                    isBlocker = blockerIds.Contains(id);
+                if (isBlocker)
+                {
+                    entered.Signal();
+                    release.Wait();
+                }
+                else
+                {
+                    executionOrder.Enqueue(id);
+                }
+                return StubLandblock(id);
+            },
+            buildMeshOrNull: (_, _) => StubMesh(),
+            workerCount: workerCount);
+
+        var taken = new HashSet<uint>();
+        var farIds = new uint[workerCount];
+        var nearIds = new uint[workerCount];
+        lock (blockerIds)
+        {
+            for (int lane = 0; lane < workerCount; lane++)
+            {
+                blockerIds.Add(IdInLane(streamer, lane, taken));
+                farIds[lane] = IdInLane(streamer, lane, taken);
+                nearIds[lane] = IdInLane(streamer, lane, taken);
+            }
+        }
+
+        streamer.Start();
+        lock (blockerIds)
+        {
+            foreach (uint id in blockerIds)
+                streamer.EnqueueLoad(id, LandblockStreamJobKind.LoadFar);
+        }
+        Assert.True(entered.Wait(TimeSpan.FromSeconds(5)));
+
+        // Far first, near second — the near job must still run first once
+        // the lane's blocker completes.
+        for (int lane = 0; lane < workerCount; lane++)
+        {
+            streamer.EnqueueLoad(farIds[lane], LandblockStreamJobKind.LoadFar);
+            streamer.EnqueueLoad(nearIds[lane], LandblockStreamJobKind.LoadNear);
+        }
+
+        release.Set();
+
+        await DrainCountAsync(streamer, workerCount * 3);
+
+        var observed = executionOrder.ToList();
+        for (int lane = 0; lane < workerCount; lane++)
+        {
+            int nearIndex = observed.IndexOf(nearIds[lane]);
+            int farIndex = observed.IndexOf(farIds[lane]);
+            Assert.True(nearIndex >= 0 && farIndex >= 0);
+            Assert.True(
+                nearIndex < farIndex,
+                $"lane {lane}: near 0x{nearIds[lane]:X8} (index {nearIndex}) ran " +
+                $"after far 0x{farIds[lane]:X8} (index {farIndex}).");
+        }
+    }
+
+    [Fact]
+    public async Task SingleWorkerPool_ReproducesSerialGlobalOrdering()
+    {
+        // The degenerate pool of one must be today's (pre-#418) behavior
+        // exactly: one worker thread, global near-first execution order
+        // across DIFFERENT landblock ids.
+        var callOrder = new List<uint>();
+        var loaderThreads = new HashSet<int>();
+
+        using var streamer = new LandblockStreamer(
+            loadLandblock: (uint id, LandblockStreamJobKind _) =>
+            {
+                callOrder.Add(id);
+                loaderThreads.Add(System.Environment.CurrentManagedThreadId);
+                return StubLandblock(id);
+            },
+            buildMeshOrNull: (_, _) => StubMesh(),
+            workerCount: 1);
+        Assert.Equal(1, streamer.WorkerCount);
+
+        streamer.EnqueueLoad(0xAAAAFFFFu, LandblockStreamJobKind.LoadFar);
+        streamer.EnqueueLoad(0xBBBBFFFFu, LandblockStreamJobKind.LoadFar);
+        streamer.EnqueueLoad(0xCCCCFFFFu, LandblockStreamJobKind.LoadNear);
+        streamer.Start();
+
+        List<LandblockStreamResult> results = await DrainCountAsync(streamer, 3);
+
+        Assert.Equal(
+            new[] { 0xCCCCFFFFu, 0xAAAAFFFFu, 0xBBBBFFFFu },
+            callOrder);
+        Assert.Single(loaderThreads);
+        var first = Assert.IsType<LandblockStreamResult.Loaded>(results[0]);
+        Assert.Equal(0xCCCCFFFFu, first.LandblockId);
+    }
+
+    [Fact]
+    public async Task Dispose_JoinsEveryWorkerInThePool()
+    {
+        const int workerCount = 3;
+        using var release = new ManualResetEventSlim();
+        using var entered = new CountdownEvent(workerCount);
+        var loaderThreads = new ConcurrentDictionary<int, byte>();
+        var blockerIds = new HashSet<uint>();
+
+        var streamer = new LandblockStreamer(
+            loadLandblock: (uint id, LandblockStreamJobKind _) =>
+            {
+                loaderThreads.TryAdd(System.Environment.CurrentManagedThreadId, 0);
+                entered.Signal();
+                release.Wait();
+                return StubLandblock(id);
+            },
+            buildMeshOrNull: (_, _) => StubMesh(),
+            workerCount: workerCount);
+
+        try
+        {
+            var taken = new HashSet<uint>();
+            for (int lane = 0; lane < workerCount; lane++)
+                blockerIds.Add(IdInLane(streamer, lane, taken));
+
+            streamer.Start();
+            foreach (uint id in blockerIds)
+                streamer.EnqueueLoad(id, LandblockStreamJobKind.LoadFar);
+            Assert.True(entered.Wait(TimeSpan.FromSeconds(5)));
+            Assert.Equal(workerCount, loaderThreads.Count);
+
+            Task dispose = Task.Run(streamer.Dispose);
+            await Task.Delay(100);
+            // Dispose must be blocked on the still-building workers.
+            Assert.False(dispose.IsCompleted);
+
+            release.Set();
+            await dispose.WaitAsync(TimeSpan.FromSeconds(5));
+
+            Assert.Throws<ObjectDisposedException>(
+                () => streamer.EnqueueLoad(0x1234FFFFu, LandblockStreamJobKind.LoadFar));
+            Assert.Throws<ObjectDisposedException>(
+                () => streamer.EnqueueUnload(0x1234FFFFu));
+            Assert.Throws<ObjectDisposedException>(streamer.ClearPendingLoads);
+        }
+        finally
+        {
+            release.Set();
+            streamer.Dispose();
+        }
+    }
+}

tests/AcDream.Core.Tests/Streaming/LandblockStreamerTests.cs

@@ -55,13 +55,19 @@ public class LandblockStreamerTests
             System.Array.Empty<AcDream.Core.Terrain.TerrainVertex>(),
             System.Array.Empty<uint>());
 
+        // workerCount: 1 — this test asserts a GLOBAL execution order across
+        // four DIFFERENT landblock ids, which only the serial degenerate pool
+        // guarantees (#418). The pool contract orders jobs per landblock id
+        // and prefers Near-tier per lane; the cross-lane variant lives in
+        // AcDream.App.Tests LandblockStreamerPoolTests.
         using var streamer = new LandblockStreamer(
             loadLandblock: (id, kind) =>
             {
                 callOrder.Add((id, kind));
                 return new LoadedLandblock(id, new LandBlock(), System.Array.Empty<WorldEntity>());
             },
-            buildMeshOrNull: (_, _) => stubMesh);
+            buildMeshOrNull: (_, _) => stubMesh,
+            workerCount: 1);
 
         streamer.EnqueueLoad(0xAAAAFFFFu, LandblockStreamJobKind.LoadFar);
         streamer.EnqueueLoad(0xBBBBFFFFu, LandblockStreamJobKind.LoadFar);