Harden movie playback lifecycle and diagnostics

2026-07-22 09:44:57 -04:00
parent 5b66cb2cd2
commit 740e10c550
25 changed files with 1145 additions and 147 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -16,6 +16,8 @@ __pycache__/
 # .NET (engine/) build output
 engine/**/bin/
 engine/**/obj/
+tools/**/bin/
+tools/**/obj/
 .vs/

 # Godot / C# (future)
--- a/docs/PROJECT-STRUCTURE.md
+++ b/docs/PROJECT-STRUCTURE.md
@@ -45,6 +45,7 @@ S:\Game Hacking\Eushully\Himegari\           ← workspace root (three siblings)
    │   ├── extract_phase2.py                   batch: disasm + text + data extraction
    │   ├── extract_init.py, global_map.py …    *INIT parsers, global-var map builder
    │   ├── validate_opcode_table*.py           decode-coverage validators
+    │   ├── movie-corpus-gate/                  C# full-corpus FFmpeg decode/lifecycle acceptance tool
    │   └── probe_*.py                          format reverse-engineering probes (historical)
    │
    ├── bin/                                  3rd-party binaries we use (not ours, not the game's)
--- a/docs/asset-resolution-re.md
+++ b/docs/asset-resolution-re.md
@@ -361,12 +361,15 @@ same completed state so a backend that starts but never signals EOF cannot hold
 reported combat stall survives this guard, capture the VM/service coordinate after `0x2518` and treat it as
 a separate BTL timed-presentation bug.

-The remaining implementation boundary is the already-planned decoder interface/factory plus a software
-MPEG backend that handles the installed non-16-aligned effects, and preservation of the destination
-surface's created dimensions instead of replacing every movie surface with the SC0000-specific 800x600
-value. Failure is now nonblocking and suppresses bogus still-AGF fallback. Regressions must cover at
-least a 280x352 effect (`MVB001`), a 400x400 effect (`MVB914`), immediate `0x23f` stop time, RGBA frame
-publication, completion, failure completion, and release.
+The FFmpeg replacement and destination-surface work are recorded in `docs/platform-portability.md` and
+`docs/phase-b-framework.md`. Movie identity also remains typed across the entire retained-surface lifecycle.
+The packed catalog is immutable while mounted, so once an id enters the movie path its `.AGF`-named MPEG
+payload cannot fall through to the ACGF still decoder before the first frame or after the last live binding
+is detached. The latter guard closes a real cross-thread cleanup window: BTL clears `GfxState` and releases
+the host surface in one VM instruction, while the compositor may hold a snapshot from immediately before
+that pair. Without remembered movie typing, the snapshot briefly attempted to decode MVB955/MVB004/MVB914
+as still images after successful playback and printed false `expected an ACGF image` warnings. This does not
+retain a frame or playback instance; it only prevents an immutable movie resource from being reclassified.

 ### Modal startup/ending movie resources (implemented 2026-07-20)

--- a/docs/phase-b-framework.md
+++ b/docs/phase-b-framework.md
@@ -605,7 +605,7 @@ dependency pin, corpus codec inventory, timing contract, and packaging rules liv
   and a monotonic clock, publish only due frames, delay EOF completion through the final presentation interval,
   and retain the existing watchdog. Make FFmpeg the default with no dimension/effect dispatch and exercise both
   non-modal `0x236` and modal/cancellable `0x20f` paths.
-4. **Next — run the installed-corpus gate.** Every one of the 213 MPEG payloads must open, report its expected display
+4. **Completed — run the installed-corpus gate.** Every one of the 213 MPEG payloads must open, report its expected display
   dimensions and a positive stop time, produce a correctly sized RGBA frame, maintain nondecreasing timestamps,
   reach EOF, and dispose within a bound. Normal tests use small project-authored 280-wide and aligned MPEG
   fixtures so decoder behavior is never disabled when the original install is absent; the full local sweep is
@@ -643,9 +643,47 @@ clock tests cover due-frame publication, final completion, cancellation, and fai
 formerly failing 280x352 `MVB961` and aligned `MVB908`. A natural headless SYSTEM4 smoke played and released
 `LOGO.AGF` at its reported 7288 ms, then opened 106919 ms `OP.AGF` and published its first frame before bounded
 shutdown. The user then confirmed the opening movies play correctly in a normal windowed run. The complete suite
-is 318 tests, the Godot build is warning-free, and threaded selftest passes. **NEXT:** run the 213-payload
-installed-corpus gate, then validate SC0000 CHAPTER and the original battle exchange before removing DirectShow
-or judging the tabled combat stall.
+is 318 tests, the Godot build is warning-free, and threaded selftest passes. That established the prerequisite
+for the installed-corpus gate recorded below.
+
+Step 4 completed on 2026-07-22. `tools/movie-corpus-gate` selects MPEG program streams by signature from the
+complete native-order VFS catalog and runs the unpaced FFmpeg session to EOF. The acceptance run discovered the
+expected 213 assets and passed all 213 under the 30-second per-item bound; every stream reported independent
+matching dimensions, positive duration/frame rate, correctly sized RGBA frames, nondecreasing timestamps,
+changing imagery, EOF, and clean teardown. The run decoded 15,788 frames across all twelve installed dimension
+variants in 8.1 seconds; the longest item, 263-second `ED.AGF`, decoded in 4.4 seconds. Detailed compatibility
+evidence lives in `docs/platform-portability.md`, and reproduction/report options live in
+`docs/tools-reference.md`. This moved acceptance to step 5's windowed SC0000 `CHAPTER`, aligned plus 280-wide
+combat effects, combat cleanup, and prior-stall checks. DirectShow remains unselected but in-tree until those
+manual checks pass.
+
+The first post-corpus combat recheck still stalled after an apparently absent effect. The ordinary Godot log
+ruled out an FFmpeg decode/EOF failure: both reached battle batches opened, published first frames, and stopped
+(`MVB005`/`MVB952`/`MVB913`, then `MVB921`/`MVB126`/`MVB953`) with no decoder failure or watchdog. F6 was added as
+an observe-only bounded JSON snapshot of the current/recent VM path, host waits, movie/surface lifecycle, and
+blocking finite gfx channels.
+
+The first F6 capture localized the stall exactly to BTL's `0x2492..0x2515` movie polling loop, parked at the
+16 ms sleep `BTL@0x250a`. Gfx had no blocking timed presentation, and the only real decoder (`MVB033`, surface
+44) was complete. Surfaces 7 and 8 nevertheless retained incomplete/no-frame registrations for already stopped
+`MVB953` and `MVB126`, so op `0x23a` could never clear. The user's observation that the last effect frame remained
+until replacement was the same ownership defect: movie frames, completion, and decoder dictionaries were keyed
+by shared resource id even though BTL can bind/restart one asset through multiple surfaces. Releasing one binding
+removed shared state while another surface registration survived forever.
+
+Movie ownership is now keyed by a unique playback instance; resource id is asset identity only. Each surface
+resolves its own instance frame/completion, replacing a surface invalidates late callbacks from only its prior
+instance, and releasing one of two same-resource playbacks cannot affect the other. Blank pre-roll surfaces no
+longer borrow a concurrent instance's frame, and console/timeline diagnostics include playback ids. Duplicate-
+resource and replacement regressions pass, as do all 327 engine tests, the zero-warning Godot build, threaded
+selftest, and the 213/213 unpaced corpus gate. A quick repeat of the same combat exchange no longer stalled.
+The run did expose false `AGF decode failed ... expected an ACGF image` lines after successful first frames and
+immediately before teardown. This was not FFmpeg failure: the compositor could retain a pre-release `GfxState`
+snapshot for one frame after the host detached the movie binding, then send the `.AGF`-named MPEG id through the
+still-image fallback. Runtime-learned movie resource typing now survives instance teardown and suppresses only
+that invalid fallback; it does not retain the frame or decoder. The focused cleanup regression, all 328 engine
+tests, zero-warning Godot build, and threaded selftest pass. **NEXT:** perform a longer combat/return-to-FIELD
+acceptance run, then delete DirectShow if the remaining live gate stays clean.

 **Mutable-surface fill/blend regression corrected.** The first visual recheck exposed BUNKI's menu interior
 as transparent. SYSTEM4 creates 800x600 surface 3 and fills it opaque white through `0x20b`; the metadata-only
--- a/docs/platform-portability.md
+++ b/docs/platform-portability.md
@@ -25,8 +25,8 @@ replaced before claiming portable exports.

 | Area | Current dependency | Runtime impact | Portability status / future action |
 |---|---|---|---|
-| AGE movie decode (`0x236` scene movies; `0x20f` modal LOGO/OP/ED) | `FfmpegMovieDecoder` is the selected live factory over the project-owned `native/age_movie_ffmpeg` ABI; `DirectShowMovieDecoder` remains unselected pending deletion | Windows-x64 live playback now covers formerly rejected 280-wide effects, but other native targets and the full 213-payload gate remain | Run the corpus and windowed live gates, then delete DirectShow and add target-specific native builds |
-| Movie integration | `MovieRuntime` owns `IMovieDecoder` from an injected factory; the FFmpeg worker paces PTS against a monotonic clock and supports cancellation/failure completion | Backend ownership is portable, while `Main` remains annotated Windows because only the win-x64 bundle is available | Add Linux/macOS builds and remove the Windows annotation after DirectShow is deleted |
+| AGE movie decode (`0x236` scene movies; `0x20f` modal LOGO/OP/ED) | `FfmpegMovieDecoder` is the selected live factory over the project-owned `native/age_movie_ffmpeg` ABI; `DirectShowMovieDecoder` remains unselected pending deletion | Windows-x64 passes the complete 213-payload installed-corpus gate; other native targets and the remaining windowed CHAPTER/combat checks are pending | Run the windowed live gates, then delete DirectShow and add target-specific native builds |
+| Movie integration | Each surface owns a unique playback-instance id; `MovieRuntime` owns `IMovieDecoder` from an injected factory, and the FFmpeg worker paces PTS against a monotonic clock with cancellation/failure completion | Concurrent/restarted uses of one asset have independent frame/completion/teardown state; `Main` remains annotated Windows because only the win-x64 bundle is available | Recheck the corrected combat lifecycle, then add Linux/macOS builds and remove the Windows annotation after DirectShow is deleted |
 | Movie audio | FFmpeg detects the audio stream but the current ABI returns video frames only | MPEG movie audio remains intentionally silent | Extend the ABI with timestamped PCM and select an audio/presentation clock; separate feature slice |
 | ADV font discovery | `godot/Main.cs` probes `C:/Windows/Fonts` for Japanese fonts | Harmless fallback today, but appearance depends on host fonts | Bundle/configure a redistributable font or add platform-specific discovery |
 | Filesystem semantics | Several filename and containment comparisons use `OrdinalIgnoreCase`; installed assets are conventionally uppercase | Needs validation on case-sensitive filesystems; may hide casing or containment mistakes | Add Linux/macOS tests with mixed-case synthetic roots and use filesystem-appropriate containment rules |
@@ -135,6 +135,16 @@ smoke completed 7288 ms `LOGO.AGF`, opened 106919 ms `OP.AGF`, and published fra
 DirectShow; the user subsequently confirmed both opening movies work in normal windowed playback. Full
 export/source-offer packaging and non-Windows builds remain outstanding.

+The Windows-x64 installed-corpus gate passed on 2026-07-22 with the pinned dependency: all 213 signature-selected
+MPEG payloads opened and reached EOF under a 30-second per-item bound. It decoded all 15,788 frames across twelve
+display sizes (120x120 through 800x600), independently matched sequence-header dimensions, found positive
+duration and frame-rate metadata, verified tightly packed RGBA size and nondecreasing timestamps, observed
+changing imagery in every asset, and closed every session. The set includes all 184 video-only and 29 audio-bearing
+streams; audio presence is detected but PCM remains intentionally undelivered. The 263-second `ED.AGF` was the
+slowest decode at 4.4 seconds in the deliberately unpaced gate, so its prior 30-second failure was test-harness
+whole-frame hashing overhead rather than a decoder incompatibility. The disposable machine report is
+`build/movie-corpus-ffmpeg.json`; invocation and report semantics are canonical in `docs/tools-reference.md`.
+
 ## Cross-platform validation gates

 Before advertising a platform as supported:
--- a/docs/tools-reference.md
+++ b/docs/tools-reference.md
@@ -72,6 +72,13 @@ All opcode knowledge (ABI, semantics, provenance, `depends_on`) is hand-edited *
 |---|---|---|---|
 | `locate_page.py` | Resolve a run-relative ADV page number to its canonical wait script/offset, last show-text instruction, call stack, and nearby disassembly. Pure selection/window logic is tested by `test_locate_page.py`. | `py -3.11 -X utf8 tools/locate_page.py SC0000 14 [--map <jsonl>] [--context N]` | `build/page-map-<SCENE>.jsonl` + script corpus → stdout |

+In a live Godot run, **F6** writes an observe-only stall snapshot under
+`user://diagnostics/stall-<timestamp>.json`, prints the absolute path, and copies
+`SCRIPT@offset · stall snapshot <path>` to the clipboard. The JSON contains the current call stack, a bounded
+128-instruction ring, VM/host wait flags, surface/movie completion state, decoder state, and the exact finite
+graphics channels capable of holding an op-`0x21c` presentation wait. Press it while the apparent stall is still
+active; unlike `--timeline-log`, it does not require a special launch or emit a continuous per-op stream.
+
 ## Native FFmpeg movie shim (Windows x64)

 These PowerShell tools build the selected Windows-x64 live movie backend. The dependency manifest pins an
@@ -81,6 +88,7 @@ immutable LGPL shared FFmpeg archive and SHA-256.
 |---|---|---|---|
 | `native/age_movie_ffmpeg/bootstrap-win64.ps1` | Download, hash-check, extract, and version-check the pinned FFmpeg SDK. Returns the resolved SDK root. | `.\\native\\age_movie_ffmpeg\\bootstrap-win64.ps1 [-Destination <dir>]` | `dependency-win64.json`, network/archive cache → disposable `build/downloads/`, `build/ffmpeg-sdk/` |
 | `native/age_movie_ffmpeg/build-win64.ps1` | Discover the MSVC x64 toolchain, build `age_movie_ffmpeg.dll`, and stage its exact shared-library/license dependencies. | `.\\native\\age_movie_ffmpeg\\build-win64.ps1 -SdkRoot <bootstrap-output> [-OutputDirectory <dir>]` | C ABI source + FFmpeg SDK → disposable `build/native/win-x64/` by default |
+| `tools/movie-corpus-gate` | Discover every MPEG program stream stored under an `.AGF` catalog entry, decode every video frame through the unpaced FFmpeg session, validate independent sequence dimensions, metadata, RGBA size, timestamps, EOF, timeout, and teardown, then emit a per-asset JSON report. Exit 0 means the expected corpus count and every asset passed; exit 1 is a gate failure; exit 2 means the native shim is absent. | `dotnet run --project tools/movie-corpus-gate -- --output build/movie-corpus-ffmpeg.json --expected-count 213 --max-item-ms 30000` · optional `--native-dir <dir>` | `SYS4INI.BIN` + loose/ALF VFS assets + staged FFmpeg shim → stdout progress + disposable `build/movie-corpus-ffmpeg.json` |

 The managed isolated probes load from `AGE_FFMPEG_NATIVE_DIR` when set, then application-local and
 `runtimes/win-x64/native` locations. Build the shim before running the `FfmpegShim*` tests; no original-game
@@ -88,6 +96,10 @@ movie is copied into the repository or native output. When `build/native/win-x64
 `dotnet build godot/Himegari.csproj` also stages the shim, its five DLL dependencies, and `FFmpeg-LICENSE.txt`
 beside `Himegari.dll` for development playback.

+The corpus gate intentionally bypasses presentation waits: it validates decode compatibility and lifecycle,
+not wall-clock playback pacing. `--expected-count` makes additions, omissions, or profile changes explicit;
+changing the pinned FFmpeg dependency requires rerunning this gate.
+
 ## Engine (C#) — VM core, CLI, Godot frontend

 The `engine/` .NET solution (`AgeEngine.sln`) is the runtime VM; `godot/` is the ADV frontend. Not
--- a/engine/Age.Engine.Tests/Age.Engine.Tests.csproj
+++ b/engine/Age.Engine.Tests/Age.Engine.Tests.csproj
@@ -26,6 +26,11 @@
    <Compile Include="..\..\godot\MovieRuntime.cs" Link="MovieRuntime.cs" />
    <Compile Include="..\..\godot\FfmpegMovieNative.cs" Link="FfmpegMovieNative.cs" />
    <Compile Include="..\..\godot\FfmpegMovieDecoder.cs" Link="FfmpegMovieDecoder.cs" />
+    <Compile Include="..\..\godot\PageLocatorState.cs" Link="PageLocatorState.cs" />
+    <Compile Include="..\..\godot\GodotTimelineLog.cs" Link="GodotTimelineLog.cs" />
+    <Compile Include="..\..\godot\GodotTraceSink.cs" Link="GodotTraceSink.cs" />
+    <Compile Include="..\..\godot\MovieSurfaceRegistry.cs" Link="MovieSurfaceRegistry.cs" />
+    <Compile Include="..\..\tools\movie-corpus-gate\MovieCorpusGate.cs" Link="MovieCorpusGate.cs" />
    <Compile Include="..\..\godot\DirectShowMovieDecoder.cs" Link="DirectShowMovieDecoder.cs" />
  </ItemGroup>

--- a/engine/Age.Engine.Tests/GfxDiagnosticSnapshotTests.cs
+++ b/engine/Age.Engine.Tests/GfxDiagnosticSnapshotTests.cs
@@ -0,0 +1,24 @@
+using Age.Engine.Model;
+
+public class GfxDiagnosticSnapshotTests
+{
+    [Fact]
+    public void SnapshotIdentifiesOnlyChannelsThatCanBlockPresentationWait()
+    {
+        var gfx = new GfxState();
+        gfx.BindDraw(0x100, 7, 0, 0, 32, 32, 0, 0);
+        gfx.SetTranslationChannel(0x100, 25, 300, (20, 30, 0));
+        gfx.BindDraw(0x200, 8, 0, 0, 32, 32, 0, 0);
+        gfx.SetScaleChannel(0x200, 0, 500, (200, 200, 100));
+        gfx.SetOneShotAnimationControl(0x200, 1);
+
+        GfxDiagnosticSnapshot snapshot = gfx.CaptureDiagnosticSnapshot(1000);
+
+        Assert.True(snapshot.HasActiveTimedPresentation);
+        var blocking = Assert.Single(snapshot.BlockingObjects);
+        Assert.Equal(0x100, blocking.Handle);
+        Assert.True(blocking.TranslationEnabled);
+        Assert.Equal(25, blocking.TranslationDelayMs);
+        Assert.Equal(300, blocking.TranslationDurationMs);
+    }
+}
--- a/engine/Age.Engine.Tests/GodotTraceSinkTests.cs
+++ b/engine/Age.Engine.Tests/GodotTraceSinkTests.cs
@@ -0,0 +1,31 @@
+using Age.Engine.Diagnostics;
+using Age.Engine.Model;
+
+public class GodotTraceSinkTests
+{
+    [Fact]
+    public void SnapshotRetainsCurrentStackAndBoundedRecentSteps()
+    {
+        using var locator = new PageLocatorState("SYSTEM4", null);
+        var sink = new GodotTraceSink(locator);
+        sink.Emit(TraceEvent.FrameEnter("SYSTEM4.BIN", 0, FrameCause.TopScene));
+        sink.Emit(TraceEvent.FrameEnter("BTL.BIN", 1, FrameCause.CallScript, 0x2b10));
+
+        for (int index = 0; index < 140; index++)
+        {
+            var instruction = new Instruction(0x2400 + index, 0x100 + index,
+                                              Array.Empty<Operand>());
+            sink.Emit(TraceEvent.Step(index, instruction, 1));
+        }
+
+        GodotTraceSnapshot snapshot = sink.Snapshot();
+
+        Assert.Equal("BTL.BIN", snapshot.CurrentScript);
+        Assert.Equal(0x2400 + 139, snapshot.CurrentOffset);
+        Assert.Equal(0x100 + 139, snapshot.CurrentOpcode);
+        Assert.Equal(new[] { "SYSTEM4.BIN", "BTL.BIN" }, snapshot.CallStack);
+        Assert.Equal(128, snapshot.RecentSteps.Count);
+        Assert.Equal(0x2400 + 12, snapshot.RecentSteps[0].Offset);
+        Assert.Equal(0x2400 + 139, snapshot.RecentSteps[^1].Offset);
+    }
+}
--- a/engine/Age.Engine.Tests/MovieCorpusGateTests.cs
+++ b/engine/Age.Engine.Tests/MovieCorpusGateTests.cs
@@ -0,0 +1,102 @@
+using Age.Engine.Sys4;
+
+public class MovieCorpusGateTests
+{
+    private sealed class FakeFrameSource(FfmpegMovieInfo info,
+                                         params FfmpegVideoFrame[] frames) : IFfmpegFrameSource
+    {
+        private readonly Queue<FfmpegVideoFrame> _frames = new(frames);
+        public FfmpegMovieInfo Info { get; } = info;
+        public bool Disposed { get; private set; }
+        public bool TryDecodeNextVideoFrame(out FfmpegVideoFrame frame)
+            => _frames.TryDequeue(out frame!);
+        public void Dispose() => Disposed = true;
+    }
+
+    [Fact]
+    public void SequenceHeaderProbeReadsIndependentDimensions()
+    {
+        byte[] payload = SyntheticPayload(320, 240);
+
+        Assert.True(MovieCorpusDiscovery.TryReadSequenceDimensions(payload, out int width, out int height));
+        Assert.Equal(320, width);
+        Assert.Equal(240, height);
+        Assert.False(MovieCorpusDiscovery.TryReadSequenceDimensions(new byte[] { 0, 0, 1, 0xba }, out _, out _));
+    }
+
+    [Fact]
+    public void GateReportsFramesMetadataTimingAndTeardown()
+    {
+        var source = new FakeFrameSource(new FfmpegMovieInfo(16, 16, 100, 20, 1, false),
+            Frame(16, 16, 1, 0), Frame(16, 16, 2, 50));
+        var input = new MovieCorpusInput(0x2bc2, "SYNTH.AGF", () =>
+            new MoviePayload("SYNTH.AGF", SyntheticPayload(16, 16)));
+
+        MovieCorpusReport report = new MovieCorpusGate(_ => source).Run([input], 1, 1000);
+
+        Assert.True(report.Passed);
+        var item = Assert.Single(report.Movies);
+        Assert.True(item.Passed);
+        Assert.Equal("0x2bc2", item.PackedIdHex);
+        Assert.Equal(16, item.ExpectedWidth);
+        Assert.Equal(2, item.FrameCount);
+        Assert.Equal(0, item.FirstPresentationTimeMs);
+        Assert.Equal(50, item.LastPresentationTimeMs);
+        Assert.True(item.FramesChanged);
+        Assert.True(source.Disposed);
+    }
+
+    [Fact]
+    public void GateContinuesAfterValidationFailureAndReportsCountMismatch()
+    {
+        var badDimensions = new FakeFrameSource(new FfmpegMovieInfo(8, 16, 100, 20, 1, false),
+            Frame(8, 16, 1, 0));
+        var decreasingTimestamps = new FakeFrameSource(new FfmpegMovieInfo(16, 16, 100, 20, 1, false),
+            Frame(16, 16, 1, 50), Frame(16, 16, 2, 40));
+        var sources = new Queue<IFfmpegFrameSource>([badDimensions, decreasingTimestamps]);
+        MovieCorpusInput[] inputs =
+        [
+            new(1, "BAD-DIMS.AGF", () => new MoviePayload("BAD-DIMS.AGF", SyntheticPayload(16, 16))),
+            new(2, "BAD-PTS.AGF", () => new MoviePayload("BAD-PTS.AGF", SyntheticPayload(16, 16))),
+        ];
+
+        MovieCorpusReport report = new MovieCorpusGate(_ => sources.Dequeue()).Run(inputs, 3, 1000);
+
+        Assert.False(report.Passed);
+        Assert.Equal(2, report.FailedCount);
+        Assert.Contains("expected 3", Assert.Single(report.SelectionErrors));
+        Assert.Contains("differ", report.Movies[0].Error);
+        Assert.Contains("timestamp", report.Movies[1].Error);
+        Assert.True(badDimensions.Disposed);
+        Assert.True(decreasingTimestamps.Disposed);
+    }
+
+    [Fact]
+    public void GateRejectsInvalidFrameRateMetadata()
+    {
+        var source = new FakeFrameSource(new FfmpegMovieInfo(16, 16, 100, 0, 1, false),
+            Frame(16, 16, 1, 0));
+        var input = new MovieCorpusInput(1, "BAD-RATE.AGF", () =>
+            new MoviePayload("BAD-RATE.AGF", SyntheticPayload(16, 16)));
+
+        MovieCorpusReport report = new MovieCorpusGate(_ => source).Run([input], 1, 1000);
+
+        Assert.False(report.Passed);
+        Assert.Contains("rate 0/1", Assert.Single(report.Movies).Error);
+        Assert.True(source.Disposed);
+    }
+
+    private static byte[] SyntheticPayload(int width, int height) =>
+    [
+        0, 0, 1, 0xba,
+        0, 0, 1, 0xb3,
+        (byte)(width >> 4),
+        (byte)(((width & 0x0f) << 4) | (height >> 8)),
+        (byte)height,
+        0,
+    ];
+
+    private static FfmpegVideoFrame Frame(int width, int height, byte value, long timestamp)
+        => new(new RgbaImage(width, height,
+            Enumerable.Repeat(value, checked(width * height * 4)).ToArray()), timestamp);
+}
--- a/engine/Age.Engine.Tests/MovieOpcodeTests.cs
+++ b/engine/Age.Engine.Tests/MovieOpcodeTests.cs
@@ -100,10 +100,11 @@ public class MovieOpcodeTests
        var factory = new FakeMovieDecoderFactory(decoder);
        var payload = new MoviePayload("TEST.AGF", new byte[] { 0, 0, 1, 0xba });

-        var runtime = MovieRuntime.Open("TEST.AGF", 7, payload, factory);
+        var runtime = MovieRuntime.Open("TEST.AGF", 7, 0x123, payload, factory);

        Assert.Same(payload, factory.OpenedPayload);
        Assert.Same(decoder, runtime.Decoder);
+        Assert.Equal(0x123, runtime.ResourceId);
        Assert.Equal(1876, runtime.Decoder.StopTimeMs);
        Assert.Equal(5000, runtime.WatchdogMs);
        Assert.True(runtime.Decoder.TryTakeFrame(out var frame));
@@ -120,7 +121,7 @@ public class MovieOpcodeTests
    public void MovieRuntimeComputesBoundedWatchdogFromDecoderMetadata(long? stopTimeMs, long expected)
    {
        var decoder = new FakeMovieDecoder { StopTimeMs = stopTimeMs };
-        var runtime = MovieRuntime.Open("TEST.AGF", 7,
+        var runtime = MovieRuntime.Open("TEST.AGF", 7, 0x123,
            new MoviePayload("TEST.AGF", new byte[] { 0, 0, 1, 0xba }),
            new FakeMovieDecoderFactory(decoder));

--- a/engine/Age.Engine.Tests/MovieSurfaceRegistryTests.cs
+++ b/engine/Age.Engine.Tests/MovieSurfaceRegistryTests.cs
@@ -0,0 +1,65 @@
+using Age.Engine.Sys4;
+
+public class MovieSurfaceRegistryTests
+{
+    [Fact]
+    public void SameResourceOnTwoSurfacesHasIndependentFramesCompletionAndRelease()
+    {
+        var registry = new MovieSurfaceRegistry();
+        MovieSurfaceBinding first = registry.Begin(7, 0x2b42, out _);
+        MovieSurfaceBinding second = registry.Begin(8, 0x2b42, out _);
+        var firstFrame = Frame(1);
+        var secondFrame = Frame(2);
+
+        Assert.True(registry.PublishFrame(first.PlaybackId, firstFrame, "MVB126.AGF", 0x2b42));
+        Assert.True(registry.PublishFrame(second.PlaybackId, secondFrame, "MVB126.AGF", 0x2b42));
+        Assert.True(registry.Complete(first.PlaybackId));
+
+        MovieSurfaceRelease released = registry.ReleaseIfCompleted(7);
+
+        Assert.Equal(MovieSurfaceReleaseKind.Released, released.Kind);
+        Assert.False(registry.IsBound(7));
+        Assert.True(registry.IsActive(8));
+        Assert.True(registry.TryResolveSurface(8, out MovieSurfaceFrame? remaining));
+        Assert.Same(secondFrame, remaining!.Image);
+        Assert.True(registry.Complete(second.PlaybackId));
+        Assert.Equal(MovieSurfaceReleaseKind.Released, registry.ReleaseIfCompleted(8).Kind);
+        Assert.False(registry.HasActivePlayback);
+    }
+
+    [Fact]
+    public void ReplacingSurfaceInvalidatesLateEventsFromPriorPlayback()
+    {
+        var registry = new MovieSurfaceRegistry();
+        MovieSurfaceBinding prior = registry.Begin(7, 0x2bdc, out _);
+
+        MovieSurfaceBinding current = registry.Begin(7, 0x2bad, out MovieSurfaceBinding? replaced);
+
+        Assert.Equal(prior, replaced);
+        Assert.False(registry.Complete(prior.PlaybackId));
+        Assert.False(registry.PublishFrame(prior.PlaybackId, Frame(1), "OLD.AGF", 1));
+        Assert.True(registry.IsActive(7));
+        Assert.True(registry.PublishFrame(current.PlaybackId, Frame(2), "NEW.AGF", 2));
+        Assert.True(registry.TryResolveSurface(7, out MovieSurfaceFrame? frame));
+        Assert.Equal("NEW.AGF", frame!.Name);
+    }
+
+    [Fact]
+    public void ReleasedMovieResourceRemainsTypedAsMovieForCleanupFrame()
+    {
+        var registry = new MovieSurfaceRegistry();
+        MovieSurfaceBinding binding = registry.Begin(7, 0x2bde, out _);
+
+        Assert.True(registry.IsKnownMovieResource(0x2bde));
+        Assert.True(registry.Complete(binding.PlaybackId));
+        Assert.Equal(MovieSurfaceReleaseKind.Released, registry.ReleaseIfCompleted(7).Kind);
+
+        Assert.False(registry.IsBound(7));
+        Assert.False(registry.TryResolveResource(0x2bde, out _));
+        Assert.True(registry.IsKnownMovieResource(0x2bde));
+        Assert.False(registry.IsKnownMovieResource(0x2af5));
+    }
+
+    private static RgbaImage Frame(byte value)
+        => new(1, 1, new[] { value, value, value, (byte)255 });
+}
--- a/engine/Age.Engine.Tests/Sys4AssetStoreTests.cs
+++ b/engine/Age.Engine.Tests/Sys4AssetStoreTests.cs
@@ -39,6 +39,23 @@ public class Sys4AssetStoreTests
        Assert.Equal("23F0C104A45C099CEFB7D333362716EDE6F20B9EC53E4C3705A8E3A87063708E", digest);
    }

+    [Fact]
+    public void CompletePackedAssetEnumerationPreservesBaseThenAppendOrder()
+    {
+        var catalog = Sys4AssetCatalog.Load(Paths.Sys4Ini);
+        var append = Assert.Single(catalog.AppendPacks).Value;
+
+        var assets = catalog.EnumerateAssets();
+
+        Assert.Equal(catalog.Files.Count + append.Files.Count, assets.Count);
+        Assert.Equal(0, assets[0].PackedId);
+        Assert.Same(catalog.Files[0], assets[0].Asset);
+        Assert.Equal(0x01000000, assets[catalog.Files.Count].PackedId);
+        Assert.Same(append.Files[0], assets[catalog.Files.Count].Asset);
+        Assert.Equal(catalog.EnumerateScripts(), assets.Where(entry =>
+            entry.Asset.Name.EndsWith(".BIN", StringComparison.OrdinalIgnoreCase)));
+    }
+
    [Fact]
    public void CompleteAppendDirectoryAndPayloadsMatchBinExtractAlf()
    {
--- a/engine/Age.Engine/Model/GfxState.cs
+++ b/engine/Age.Engine/Model/GfxState.cs
@@ -31,6 +31,22 @@ public readonly record struct NumericGlyphStyle(int SurfaceSlot, int AtlasX, int
    public bool Registered => SurfaceSlot != 0;
 }

+public sealed record BlockingGfxObjectDiagnostic(
+    long Handle, int SourceSlot, long StartMs, long ControlFlags,
+    bool ColorEnabled, long ColorDelayMs, long ColorDurationMs,
+    bool ScaleEnabled, long ScaleDelayMs, long ScaleDurationMs,
+    bool RotationEnabled, long RotationDelayMs, long RotationDurationMs,
+    bool TranslationEnabled, long TranslationDelayMs, long TranslationDurationMs);
+
+public sealed record GfxDiagnosticSnapshot(
+    long NowMs, bool HasActiveTimedPresentation, int ObjectCount, int VisibleObjectCount,
+    int ActiveSurfaceTransitionCount, long AnimationServiceFlags,
+    long AnimClockDurationTicks, long AnimClockGeneration,
+    uint PreviousFrameTimeMilliseconds, uint CurrentFrameTimeMilliseconds,
+    long RangeTransformFirst, long RangeTransformCount,
+    BlockingGfxObjectDiagnostic? BlockingRangeTransform,
+    IReadOnlyList<BlockingGfxObjectDiagnostic> BlockingObjects);
+
 /// <summary>A renderable view of one visible gfx object — the host composites these in ascending-handle order
 /// (= the engine's z-order) each frame. Built by <see cref="GfxState.SnapshotVisibleObjects"/>; the surface
 /// resId/colorkey are resolved from the object's live source slot at snapshot time (see docs/engine-re.md,
@@ -545,6 +561,51 @@ public sealed class GfxState
                                             o.RotationChannelEnabled || o.TranslationEnabled));
    }

+    /// <summary>Observe-only state for a runtime stall capture. It identifies the exact finite channels
+    /// which can keep the host's op-0x21c presentation wait active.</summary>
+    public GfxDiagnosticSnapshot CaptureDiagnosticSnapshot(long nowMs)
+    {
+        lock (_lock)
+        {
+            BlockingGfxObjectDiagnostic? range = HasBlockingChannels(_rangeTransform)
+                ? DescribeBlockingObject(-1, _rangeTransform)
+                : null;
+            var objects = _objects
+                .Where(pair => pair.Value.Visible
+                    && (pair.Value.OneShotAnimationControlFlags & 1) == 0
+                    && HasBlockingChannels(pair.Value))
+                .OrderBy(pair => pair.Key)
+                .Select(pair => DescribeBlockingObject(pair.Key, pair.Value))
+                .ToArray();
+            return new GfxDiagnosticSnapshot(
+                nowMs,
+                _surfaceTransitions.Values.Any(t => TransitionProgress(t, nowMs) < 1.0)
+                    || range != null || objects.Length != 0,
+                _objects.Count,
+                _objects.Values.Count(o => o.Visible),
+                _surfaceTransitions.Values.Count(t => TransitionProgress(t, nowMs) < 1.0),
+                AnimationServiceFlags,
+                AnimClockDurationTicks,
+                AnimClockGeneration,
+                PreviousFrameTimeMilliseconds,
+                CurrentFrameTimeMilliseconds,
+                _rangeTransformFirst,
+                _rangeTransformCount,
+                range,
+                objects);
+        }
+    }
+
+    private static bool HasBlockingChannels(GfxObject o)
+        => o.OneShotColorEnabled || o.ScaleEnabled || o.RotationChannelEnabled || o.TranslationEnabled;
+
+    private static BlockingGfxObjectDiagnostic DescribeBlockingObject(long handle, GfxObject o)
+        => new(handle, o.SourceSlot, o.OneShotStartMs, o.OneShotAnimationControlFlags,
+            o.OneShotColorEnabled, o.ColorDelayMs, o.ColorDurationMs,
+            o.ScaleEnabled, o.ScaleDelayMs, o.ScaleDurationMs,
+            o.RotationChannelEnabled, o.RotationDelayMs, o.RotationDurationMs,
+            o.TranslationEnabled, o.TranslationDelayMs, o.TranslationDurationMs);
+
    /// <summary>Op 0x242: replace the retained object's animation-control word. Native bit 0 makes its
    /// finite one-shot channels nonblocking and immune to op 0x243 forced completion.</summary>
    public void SetOneShotAnimationControl(long handle, long flags)
--- a/engine/Age.Engine/Sys4/Sys4AssetCatalog.cs
+++ b/engine/Age.Engine/Sys4/Sys4AssetCatalog.cs
@@ -179,23 +179,27 @@ public sealed class Sys4AssetCatalog
        .Where(f => f.Name.EndsWith(".BIN", StringComparison.OrdinalIgnoreCase))
        .Select(f => f.Name.ToUpperInvariant()).ToArray();

+    /// <summary>Enumerate every real asset in native packed-id order, including mounted append packs.</summary>
+    public IReadOnlyList<PackedAssetEntry> EnumerateAssets()
+    {
+        var assets = new List<PackedAssetEntry>();
+        AddAssets(this, assets);
+        foreach (var append in _appendPacks.OrderBy(pair => pair.Key).Select(pair => pair.Value))
+            AddAssets(append, assets);
+        return assets;
+    }
+
    /// <summary>Enumerate every script in native packed-id order, including mounted append packs.
    /// Placeholder slots and non-script assets are excluded without collapsing raw indices.</summary>
    public IReadOnlyList<PackedAssetEntry> EnumerateScripts()
-    {
-        var scripts = new List<PackedAssetEntry>();
-        AddScripts(this, scripts);
-        foreach (var append in _appendPacks.OrderBy(pair => pair.Key).Select(pair => pair.Value))
-            AddScripts(append, scripts);
-        return scripts;
-    }
+        => EnumerateAssets().Where(entry =>
+            entry.Asset.Name.EndsWith(".BIN", StringComparison.OrdinalIgnoreCase)).ToArray();

-    private static void AddScripts(Sys4AssetCatalog catalog, List<PackedAssetEntry> scripts)
+    private static void AddAssets(Sys4AssetCatalog catalog, List<PackedAssetEntry> assets)
    {
        long selector = (long)catalog.PackId << 24;
        foreach (var entry in catalog.Files)
-            if (entry.Name.EndsWith(".BIN", StringComparison.OrdinalIgnoreCase))
-                scripts.Add(new PackedAssetEntry(selector | (uint)entry.RawIndex, entry));
+            assets.Add(new PackedAssetEntry(selector | (uint)entry.RawIndex, entry));
    }

    private static Dictionary<string, (int Start, int End)> BuildSceneRanges(IReadOnlyList<AssetEntry> files)
--- a/godot/FfmpegMovieDecoder.cs
+++ b/godot/FfmpegMovieDecoder.cs
@@ -4,12 +4,6 @@ using System.IO;
 using System.Threading;
 using Age.Engine.Sys4;

-internal interface IFfmpegFrameSource : IDisposable
-{
-    FfmpegMovieInfo Info { get; }
-    bool TryDecodeNextVideoFrame(out FfmpegVideoFrame frame);
-}
-
 internal interface IMoviePacingClock
 {
    bool WaitUntil(long elapsedMilliseconds, WaitHandle cancellation);
--- a/godot/FfmpegMovieNative.cs
+++ b/godot/FfmpegMovieNative.cs
@@ -14,6 +14,12 @@ internal readonly record struct FfmpegMovieInfo(

 internal sealed record FfmpegVideoFrame(RgbaImage Image, long PresentationTimeMs);

+internal interface IFfmpegFrameSource : IDisposable
+{
+    FfmpegMovieInfo Info { get; }
+    bool TryDecodeNextVideoFrame(out FfmpegVideoFrame frame);
+}
+
 /// <summary>Sequential, unpaced access to the project-owned FFmpeg C ABI for isolated probes and playback.</summary>
 internal sealed class FfmpegMovieSession : IFfmpegFrameSource
 {
--- a/godot/GodotAdvHost.cs
+++ b/godot/GodotAdvHost.cs
@@ -22,9 +22,7 @@ public sealed class GodotAdvHost : IHost
    private readonly Dictionary<int, RgbaImage> _surfaceImages = new();
    private readonly Dictionary<int, long> _surfaceColorKeys = new();
    private readonly Dictionary<int, long> _surfaceResources = new();    // surface slot -> packed catalog id
-    private readonly Dictionary<long, (RgbaImage Image, string Name, int AssetId)> _movieFrames = new();
-    private readonly Dictionary<int, long> _movieBySurface = new();
-    private readonly HashSet<long> _completedMovies = new();
+    private readonly MovieSurfaceRegistry _movieSurfaces = new();
    private readonly string?[] _sfxNames = new string?[10];              // SC0000 native channel subset
    // slot -> dimensions of the currently allocated surface. Slot 0 begins as the engine's 800x600
    // primary surface, but op 0x1fa releases it like any other slot; subsequent size queries must return 0x0.
@@ -869,15 +867,13 @@ public sealed class GodotAdvHost : IHost
    /// loose-first asset store.</summary>
    public (RgbaImage Image, string Name, int AssetId, bool IsDynamic)? ResolveResIdTexture(long resId)
    {
-        lock (_imageLock)
-        {
-            if (_movieFrames.TryGetValue(resId, out var movie))
-                return (movie.Image, movie.Name, movie.AssetId, true);
-            // Movie payloads use the same .AGF extension as still images. While the decoder is opening
-            // (or before its first frame arrives), keep the already-created surface blank
-            // instead of falling through to AgfDecoder and misclassifying the MPEG program stream.
-            if (_movieBySurface.Values.Contains(resId)) return null;
-        }
+        if (_movieSurfaces.TryResolveResource(resId, out var movie) && movie != null)
+            return (movie.Image, movie.Name, movie.AssetId, true);
+        // Movie payloads use the same .AGF extension as still images. Do not misclassify the MPEG program
+        // stream before its first frame or during the cleanup frame after its surface binding is detached.
+        // Packed catalog identity is immutable, so a resource which entered the typed movie path remains
+        // a movie even when it has no live playback.
+        if (_movieSurfaces.IsKnownMovieResource(resId)) return null;
        var asset = _res.ResolveTexture(resId);
        var image = asset != null ? Decode(asset) : null;
        return asset != null && image != null ? (image, asset.Name, asset.PackedId, false) : null;
@@ -886,27 +882,49 @@ public sealed class GodotAdvHost : IHost
    public (RgbaImage Image, string Name, int AssetId, bool IsDynamic)? ResolveSurfaceTexture(
        int surfaceSlot, long fallbackResourceId)
    {
+        if (_movieSurfaces.TryResolveSurface(surfaceSlot, out var movie) && movie != null)
+            return (movie.Image, movie.Name, movie.AssetId, true);
+        if (_movieSurfaces.IsBound(surfaceSlot)) return null;
        lock (_imageLock)
            if (_surfaceImages.TryGetValue(surfaceSlot, out var surface))
                return (surface, $"<surface:{surfaceSlot}>", int.MinValue + surfaceSlot, true);
        return fallbackResourceId != 0 ? ResolveResIdTexture(fallbackResourceId) : null;
    }

+    public bool IsMovieSurfaceBound(int surfaceSlot) => _movieSurfaces.IsBound(surfaceSlot);
+
    public long? PlayMovieToSurface(long resourceId, int surfaceSlot, long movieFlags, long syncMask)
    {
        string scene = CurrentScene;
        var asset = _res.ResolveMovie(resourceId);
        if (asset == null) { Godot.GD.Print($"movie unresolved {scene}:0x{resourceId:x}"); return null; }
        StartMovie(asset, resourceId, surfaceSlot, movieFlags, syncMask, modal: false,
-                   out long? stopTimeMs);
+                   out long? stopTimeMs, out _);
        return stopTimeMs ?? 0;
    }

    public bool IsMovieSurfaceActive(int surfaceSlot)
+        => _movieSurfaces.IsActive(surfaceSlot);
+
+    public GodotHostDiagnosticSnapshot CaptureDiagnosticSnapshot()
    {
-        lock (_imageLock)
-            return _movieBySurface.TryGetValue(surfaceSlot, out long resourceId)
-                && !_completedMovies.Contains(resourceId);
+        IReadOnlyList<MovieSurfaceDiagnostic> movies = _movieSurfaces.Snapshot();
+        IReadOnlyList<long> completed = _movieSurfaces.CompletedPlaybackIds();
+        bool screenTransitionActive;
+        lock (_screenTransitionLock) screenTransitionActive = _screenTransition != null;
+        return new GodotHostDiagnosticSnapshot(
+            CurrentScene,
+            IsWaiting,
+            IsTransitionWaiting,
+            IsSleeping,
+            IsTextRevealing,
+            _modalMovieWaiting,
+            _advPagePresentationSuspended,
+            _messageSkipActive,
+            screenTransitionActive,
+            TransitionStartedAtMs,
+            movies,
+            completed);
    }

    public void PlayModalMovieToSurface(long resourceId, int surfaceSlot, long movieFlags)
@@ -923,22 +941,22 @@ public sealed class GodotAdvHost : IHost
        try
        {
            if (!StartMovie(asset, resourceId, surfaceSlot, movieFlags, 0, modal: true,
-                            out _)) return;
+                            out _, out long playbackId)) return;
            _timeline?.State("modal-movie-wait", new()
            {
-                ["resource"] = resourceId, ["surface"] = surfaceSlot, ["file"] = asset.Name,
+                ["resource"] = resourceId, ["playback"] = playbackId,
+                ["surface"] = surfaceSlot, ["file"] = asset.Name,
            });
            while (!_stopping && !_modalMovieCancelled)
            {
-                lock (_imageLock)
-                    if (_completedMovies.Contains(resourceId)) break;
+                if (!_movieSurfaces.IsActive(surfaceSlot)) break;
                _frameSignal.WaitOne(50);
            }

            // Cancellation is a completed modal presentation from the script's perspective. The
            // wrapper's following surface-release opcode performs the ordinary decoder teardown.
            if (_modalMovieCancelled)
-                lock (_imageLock) _completedMovies.Add(resourceId);
+                _movieSurfaces.Complete(playbackId);
            _timeline?.State("running", new()
            {
                ["modal_movie_complete"] = !_modalMovieCancelled,
@@ -953,16 +971,18 @@ public sealed class GodotAdvHost : IHost
    }

    private bool StartMovie(AssetEntry asset, long resourceId, int surfaceSlot, long movieFlags,
-                            long syncMask, bool modal, out long? stopTimeMs)
+                            long syncMask, bool modal, out long? stopTimeMs, out long playbackId)
    {
        stopTimeMs = null;
-        // Publish the movie identity before the potentially long VFS read and synchronous decoder setup.
-        // The compositor can therefore distinguish a legitimate blank pre-roll surface from a still AGF.
-        ReleaseSurface(surfaceSlot);
+        // A playback is a surface-owned instance, not the shared resource id. BTL can schedule the same
+        // asset on multiple surfaces; replacing one binding must not erase another binding's completion.
+        MovieSurfaceBinding binding = _movieSurfaces.Begin(surfaceSlot, resourceId, out var replaced);
+        playbackId = binding.PlaybackId;
+        if (replaced is { } prior) _main.CallDeferred("StopMovie", prior.PlaybackId);
        lock (_imageLock)
        {
-            _movieBySurface[surfaceSlot] = resourceId;
-            _completedMovies.Remove(resourceId);
+            _surfaceImages.Remove(surfaceSlot);
+            _surfaceColorKeys.Remove(surfaceSlot);
        }
        _slotDims[surfaceSlot] = (800, 600); // SC0000 creates this native-sized surface immediately beforehand.
        try
@@ -970,30 +990,24 @@ public sealed class GodotAdvHost : IHost
            var movie = _res.ReadMovie(asset);
            _timeline?.Event("movie-start", new()
            {
-                ["resource"] = resourceId, ["surface"] = surfaceSlot, ["file"] = movie.Name,
+                ["resource"] = resourceId, ["playback"] = playbackId,
+                ["surface"] = surfaceSlot, ["file"] = movie.Name,
                ["flags"] = movieFlags, ["sync_mask"] = syncMask, ["modal"] = modal,
            });
-            bool started = _main.TryPlayMovie(movie.Bytes, movie.Name, resourceId, asset.PackedId,
+            bool started = _main.TryPlayMovie(movie.Bytes, movie.Name, playbackId, resourceId, asset.PackedId,
                                              out stopTimeMs);
            if (!started)
            {
                stopTimeMs = 0;
-                NotifyMovieCompleted(resourceId);
+                NotifyMovieCompleted(playbackId);
            }
            return started;
        }
        catch (System.Exception e)
        {
-            lock (_imageLock)
-            {
-                if (_movieBySurface.TryGetValue(surfaceSlot, out long registered) && registered == resourceId)
-                    _movieBySurface.Remove(surfaceSlot);
-                _movieFrames.Remove(resourceId);
-                _completedMovies.Remove(resourceId);
-            }
+            _movieSurfaces.Abandon(playbackId, out _);
            _slotDims.Remove(surfaceSlot);
            stopTimeMs = 0;
-            NotifyMovieCompleted(resourceId);
            Godot.GD.Print($"movie read failed {asset.Name}: {e.Message}");
            return false;
        }
@@ -1002,28 +1016,11 @@ public sealed class GodotAdvHost : IHost
    public void ReleaseSurface(int slot)
    {
        lock (_screenTransitionLock) _renderTargetSnapshots.Remove(slot);
-        long resourceId;
+        MovieSurfaceRelease movieRelease = _movieSurfaces.ReleaseIfCompleted(slot);
+        if (movieRelease.Kind == MovieSurfaceReleaseKind.Active)
+            return; // Static surface setup before 0x21c must not evict an active movie playback.
        lock (_imageLock)
        {
-            if (!_movieBySurface.Remove(slot, out resourceId))
-            {
-                _surfaceImages.Remove(slot);
-                _surfaceColorKeys.Remove(slot);
-                lock (_textLock)
-                {
-                    _surfaceText.Remove(slot);
-                    _surfaceResources.Remove(slot);
-                }
-                _slotDims.Remove(slot);
-                return;
-            }
-            if (!_completedMovies.Contains(resourceId))
-            {
-                _movieBySurface[slot] = resourceId;
-                return; // SC0000 prepares following static surfaces before 0x21c; the movie remains retained.
-            }
-            _movieFrames.Remove(resourceId);
-            _completedMovies.Remove(resourceId);
            _surfaceImages.Remove(slot);
            _surfaceColorKeys.Remove(slot);
        }
@@ -1033,8 +1030,17 @@ public sealed class GodotAdvHost : IHost
            _surfaceResources.Remove(slot);
        }
        _slotDims.Remove(slot);
-        _timeline?.Event("movie-stop", new() { ["resource"] = resourceId, ["surface"] = slot });
-        _main.CallDeferred("StopMovie", resourceId);
+        if (movieRelease.Kind == MovieSurfaceReleaseKind.Released)
+        {
+            var binding = movieRelease.Binding;
+            _timeline?.Event("movie-stop", new()
+            {
+                ["resource"] = binding.ResourceId,
+                ["playback"] = binding.PlaybackId,
+                ["surface"] = slot,
+            });
+            _main.CallDeferred("StopMovie", binding.PlaybackId);
+        }
    }

    public void ClearRenderTarget(int surfaceSlot)
@@ -1049,7 +1055,7 @@ public sealed class GodotAdvHost : IHost

    public void ReleaseSurfaceRange(int firstSlot, int count)
    {
-        var stoppedMovies = new System.Collections.Generic.HashSet<long>();
+        IReadOnlyList<MovieSurfaceBinding> stoppedMovies = _movieSurfaces.ReleaseRange(firstSlot, count);
        int end = checked(firstSlot + count);
        lock (_screenTransitionLock)
            for (int slot = firstSlot; slot < end; slot++) _renderTargetSnapshots.Remove(slot);
@@ -1057,12 +1063,6 @@ public sealed class GodotAdvHost : IHost
        {
            for (int slot = firstSlot; slot < end; slot++)
            {
-                if (_movieBySurface.Remove(slot, out long resourceId))
-                {
-                    stoppedMovies.Add(resourceId);
-                    _movieFrames.Remove(resourceId);
-                    _completedMovies.Remove(resourceId);
-                }
                _surfaceImages.Remove(slot);
                _surfaceColorKeys.Remove(slot);
                _slotDims.Remove(slot);
@@ -1076,37 +1076,36 @@ public sealed class GodotAdvHost : IHost
                _surfaceResources.Remove(slot);
            }
        }
-        foreach (long resourceId in stoppedMovies)
+        foreach (MovieSurfaceBinding binding in stoppedMovies)
        {
-            _timeline?.Event("movie-stop", new() { ["resource"] = resourceId, ["range_release"] = true });
-            _main.CallDeferred("StopMovie", resourceId);
+            _timeline?.Event("movie-stop", new()
+            {
+                ["resource"] = binding.ResourceId,
+                ["playback"] = binding.PlaybackId,
+                ["range_release"] = true,
+            });
+            _main.CallDeferred("StopMovie", binding.PlaybackId);
        }
        _timeline?.Event("surface-range-release", new() { ["first"] = firstSlot, ["count"] = count });
    }

    // Main-thread decoder handoff. Replacing the newest frame mirrors the native texture renderer's
    // sample callback: the retained object keeps its surface binding while only the surface pixels change.
-    public void PublishMovieFrame(long resourceId, string name, int assetId, RgbaImage frame)
+    public void PublishMovieFrame(long playbackId, string name, int assetId, RgbaImage frame)
    {
-        lock (_imageLock) _movieFrames[resourceId] = (frame, name, assetId);
-        System.Threading.Interlocked.Exchange(ref _presentRequested, 1);
+        if (_movieSurfaces.PublishFrame(playbackId, frame, name, assetId))
+            System.Threading.Interlocked.Exchange(ref _presentRequested, 1);
    }

-    public void NotifyMovieCompleted(long resourceId)
+    public void NotifyMovieCompleted(long playbackId)
    {
-        lock (_imageLock)
-            if (!_completedMovies.Add(resourceId)) return;
-        _timeline?.Event("movie-complete", new() { ["resource"] = resourceId });
+        if (!_movieSurfaces.Complete(playbackId)) return;
+        _timeline?.Event("movie-complete", new() { ["playback"] = playbackId });
        _frameSignal.Set();
    }

    private bool HasActiveMoviePresentation()
-    {
-        lock (_imageLock)
-            foreach (long resourceId in _movieBySurface.Values)
-                if (!_completedMovies.Contains(resourceId)) return true;
-        return false;
-    }
+        => _movieSurfaces.HasActivePlayback;

    private RgbaImage? Decode(AssetEntry asset)
    {
@@ -1254,6 +1253,11 @@ public sealed class GodotAdvHost : IHost
 }

 public readonly record struct SurfaceTextDraw(int X, int Y, string Text, AdvTextStyle Style);
+public sealed record GodotHostDiagnosticSnapshot(
+    string CurrentScene, bool IsInputWaiting, bool IsTransitionWaiting, bool IsSleeping,
+    bool IsTextRevealing, bool IsModalMovieWaiting, bool IsAdvPagePresentationSuspended,
+    bool IsMessageSkipActive, bool IsScreenTransitionActive, long TransitionStartedAtMs,
+    IReadOnlyList<MovieSurfaceDiagnostic> MovieSurfaces, IReadOnlyList<long> CompletedMoviePlaybackIds);
 public readonly record struct LegacyScreenTransitionSnapshot(
    IReadOnlyList<RenderObject> Source, IReadOnlyList<RenderObject> Target, double Progress);

--- a/godot/GodotTraceSink.cs
+++ b/godot/GodotTraceSink.cs
@@ -8,9 +8,13 @@ using Age.Engine.Diagnostics;
 // engine fact delivered over the trace seam.
 public sealed class GodotTraceSink : ITraceSink
 {
+    private const int RecentStepCapacity = 128;
    private readonly GodotTimelineLog? _timeline;
    private readonly PageLocatorState _locator;
+    private readonly object _snapshotLock = new();
    private readonly Stack<string> _scripts = new();
+    private readonly Queue<GodotTraceStepSnapshot> _recentSteps = new();
+    private GodotTraceStepSnapshot? _latestStep;
    public GodotTraceSink(PageLocatorState locator, GodotTimelineLog? timeline = null)
    { _locator = locator; _timeline = timeline; }
    // The page locator needs the exact script/offset even when the heavier timeline log is disabled.
@@ -28,8 +32,13 @@ public sealed class GodotTraceSink : ITraceSink
        }
        if (e.Kind == TraceEventKind.FrameEnter && e.Name != null)
        {
-            _scripts.Push(e.Name);
-            PublishCallStack();
+            string[] callStack;
+            lock (_snapshotLock)
+            {
+                _scripts.Push(e.Name);
+                callStack = CurrentCallStackLocked();
+            }
+            _locator.CallStack(callStack);
            _timeline?.Event("frame-enter", new()
            {
                ["name"] = e.Name, ["depth"] = e.Depth,
@@ -42,12 +51,25 @@ public sealed class GodotTraceSink : ITraceSink
            {
                ["name"] = e.Name, ["depth"] = e.Depth, ["outcome"] = e.Text,
            });
-            _scripts.Pop();
-            PublishCallStack();
+            string[] callStack;
+            lock (_snapshotLock)
+            {
+                if (_scripts.Count > 0) _scripts.Pop();
+                callStack = CurrentCallStackLocked();
+            }
+            _locator.CallStack(callStack);
        }
        else if (e.Kind == TraceEventKind.Step && e.Ins != null)
        {
-            string script = _scripts.Count > 0 ? _scripts.Peek() : "<unknown>";
+            string script;
+            lock (_snapshotLock)
+            {
+                script = _scripts.Count > 0 ? _scripts.Peek() : "<unknown>";
+                if (_recentSteps.Count == RecentStepCapacity) _recentSteps.Dequeue();
+                var step = new GodotTraceStepSnapshot(script, e.Ins.Offset, e.Opcode, e.Depth);
+                _latestStep = step;
+                _recentSteps.Enqueue(step);
+            }
            _locator.Step(script, e.Ins.Offset);
            _timeline?.Step(script, e.Ins.Offset, e.Opcode, e.Depth);
        }
@@ -60,10 +82,31 @@ public sealed class GodotTraceSink : ITraceSink
            _timeline?.State("halted", new() { ["reason"] = e.Text, ["steps"] = e.Steps });
    }

-    private void PublishCallStack()
+    public GodotTraceSnapshot Snapshot()
+    {
+        lock (_snapshotLock)
+        {
+            GodotTraceStepSnapshot? current = _latestStep;
+            return new GodotTraceSnapshot(
+                current?.Script ?? (_scripts.Count > 0 ? _scripts.Peek() : "<unknown>"),
+                current?.Offset ?? -1,
+                current?.Opcode ?? -1,
+                current?.Depth ?? System.Math.Max(0, _scripts.Count - 1),
+                CurrentCallStackLocked(),
+                _recentSteps.ToArray());
+        }
+    }
+
+    private string[] CurrentCallStackLocked()
    {
        var stack = _scripts.ToArray();
        System.Array.Reverse(stack);
-        _locator.CallStack(stack);
+        return stack;
    }
 }
+
+public sealed record GodotTraceStepSnapshot(string Script, int Offset, int Opcode, int Depth);
+
+public sealed record GodotTraceSnapshot(string CurrentScript, int CurrentOffset, int CurrentOpcode,
+                                        int CurrentDepth, IReadOnlyList<string> CallStack,
+                                        IReadOnlyList<GodotTraceStepSnapshot> RecentSteps);
--- a/godot/Main.cs
+++ b/godot/Main.cs
@@ -393,6 +393,12 @@ public partial class Main : Godot.Control
            GetViewport().SetInputAsHandled();
            return;
        }
+        if (e is InputEventKey diagnosticKey && diagnosticKey.Keycode == Key.F6)
+        {
+            if (diagnosticKey.Pressed && !diagnosticKey.Echo) CaptureStallDiagnostic();
+            GetViewport().SetInputAsHandled();
+            return;
+        }
        if (_debugSceneLauncher?.Visible == true)
        {
            if (e is InputEventKey escape && escape.Pressed && !escape.Echo && escape.Keycode == Key.Escape)
@@ -501,6 +507,86 @@ public partial class Main : Godot.Control
    private static bool IsAdvanceAction(int action) => action is 4 or 5;
    private static bool HasAdvanceAction(int mask) => (mask & ((1 << 4) | (1 << 5))) != 0;

+    private void CaptureStallDiagnostic()
+    {
+        try
+        {
+            long nowMs = _clock.NowMs;
+            GodotTraceSnapshot trace = _trace.Snapshot();
+            var activeMovies = _movies
+                .OrderBy(pair => pair.Key)
+                .Select(pair => new
+                {
+                    playback_id = pair.Key,
+                    resource_id = pair.Value.ResourceId,
+                    name = pair.Value.Name,
+                    asset_id = pair.Value.AssetId,
+                    stop_time_ms = pair.Value.Decoder.StopTimeMs,
+                    decoder_completed = pair.Value.Decoder.IsCompleted,
+                    decoder_failure = pair.Value.Decoder.Failure,
+                    frame_seen = _movieFrameSeen.Contains(pair.Key),
+                    completion_notified = _movieCompletionNotified.Contains(pair.Key),
+                    watchdog_ms = pair.Value.WatchdogMs,
+                    elapsed_ms = (long)Stopwatch.GetElapsedTime(pair.Value.StartedAtTimestamp).TotalMilliseconds,
+                })
+                .ToArray();
+            var pendingMovies = _pendingMovies
+                .OrderBy(pair => pair.Key)
+                .Select(pair => new
+                {
+                    playback_id = pair.Key,
+                    resource_id = pair.Value.ResourceId,
+                    name = pair.Value.Name,
+                    asset_id = pair.Value.AssetId,
+                    stop_time_ms = pair.Value.Decoder.StopTimeMs,
+                    decoder_completed = pair.Value.Decoder.IsCompleted,
+                    decoder_failure = pair.Value.Decoder.Failure,
+                })
+                .ToArray();
+            var snapshot = new
+            {
+                format_version = 1,
+                captured_utc = System.DateTimeOffset.UtcNow.ToString("O"),
+                render_frame = _timelineFrame,
+                clock_ms = nowMs,
+                vm = new
+                {
+                    steps = _vm.Steps,
+                    halt_reason = _vm.HaltReason,
+                    done = _done,
+                    trace,
+                },
+                host = _host.CaptureDiagnosticSnapshot(),
+                gfx = _vm.Gfx.CaptureDiagnosticSnapshot(nowMs),
+                active_movies = activeMovies,
+                pending_movies = pendingMovies,
+            };
+
+            string directory = ProjectSettings.GlobalizePath("user://diagnostics");
+            System.IO.Directory.CreateDirectory(directory);
+            string path = System.IO.Path.Combine(directory,
+                $"stall-{System.DateTimeOffset.Now:yyyyMMdd-HHmmss-fff}.json");
+            var jsonOptions = new JsonSerializerOptions
+            {
+                WriteIndented = true,
+                PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+            };
+            System.IO.File.WriteAllText(path, JsonSerializer.Serialize(snapshot, jsonOptions));
+            string coordinate = trace.CurrentOffset >= 0
+                ? $"{System.IO.Path.GetFileNameWithoutExtension(trace.CurrentScript).ToUpperInvariant()}@0x{trace.CurrentOffset:x}"
+                : trace.CurrentScript;
+            string clipboard = $"{coordinate} · stall snapshot {path}";
+            DisplayServer.ClipboardSet(clipboard);
+            _status.Text = $"Diagnostic saved: {coordinate} (path copied)";
+            GD.Print($"[diagnostic] stall snapshot {coordinate} -> {path}");
+        }
+        catch (System.Exception exception)
+        {
+            _status.Text = "Diagnostic capture failed; see Godot log.";
+            GD.Print($"[diagnostic] stall snapshot failed: {exception}");
+        }
+    }
+
    private void ToggleDebugSceneLauncher()
    {
        if (_debugSceneLauncher == null) return;
@@ -680,6 +766,7 @@ public partial class Main : Godot.Control
            var surfaceTexture = rawObject != null
                ? _host.ResolveSurfaceTexture(rawObject.SourceSlot, v.SurfaceResId)
                : null;
+            bool movieSurfaceBound = rawObject != null && _host.IsMovieSurfaceBound(rawObject.SourceSlot);
            string outcome;
            if (v.SurfaceTransition is { } transition)
            {
@@ -709,7 +796,8 @@ public partial class Main : Godot.Control
            }
            else
            {
-                var texture = surfaceTexture ?? _host.ResolveResIdTexture(v.SurfaceResId);
+                var texture = surfaceTexture
+                    ?? (movieSurfaceBound ? null : _host.ResolveResIdTexture(v.SurfaceResId));
                if (texture == null) outcome = $"SKIP(resId=0x{v.SurfaceResId:x} UNRESOLVED)";
                else
                {
@@ -889,6 +977,7 @@ public partial class Main : Godot.Control
            var texture = rawObject != null
                ? _host.ResolveSurfaceTexture(rawObject.SourceSlot, source.SurfaceResId)
                : null;
+            bool movieSurfaceBound = rawObject != null && _host.IsMovieSurfaceBound(rawObject.SourceSlot);
            if (source.SurfaceResId == 0 && texture == null)
            {
                if (source.Blend == BlendKind.Opaque) continue;
@@ -897,7 +986,7 @@ public partial class Main : Godot.Control
            }
            else
            {
-                texture ??= _host.ResolveResIdTexture(source.SurfaceResId);
+                if (!movieSurfaceBound) texture ??= _host.ResolveResIdTexture(source.SurfaceResId);
                if (texture == null) continue;
                BlitLayer(texture.Value.Image, texture.Value.AssetId, source.ColorKey, source.Tint, source.TintStrength / 255f,
                          source.SrcX, source.SrcY, source.W, source.H, affine, opacity, source.MultiplyTint,
@@ -1177,17 +1266,18 @@ public partial class Main : Godot.Control
        CreateTween().TweenProperty(_bgm, "volume_db", targetDb, realDurationSeconds);
    }

-    public bool TryPlayMovie(byte[] mpegBytes, string assetName, long resourceId, int assetId,
+    public bool TryPlayMovie(byte[] mpegBytes, string assetName, long playbackId,
+                             long resourceId, int assetId,
                             out long? stopTimeMs)
    {
        stopTimeMs = null;
        try
        {
            var payload = new Age.Engine.Sys4.MoviePayload(assetName, mpegBytes);
-            var runtime = MovieRuntime.Open(assetName, assetId, payload, _movieDecoderFactory);
+            var runtime = MovieRuntime.Open(assetName, assetId, resourceId, payload, _movieDecoderFactory);
            stopTimeMs = runtime.Decoder.StopTimeMs;
-            while (!_pendingMovies.TryAdd(resourceId, runtime))
-                if (_pendingMovies.TryRemove(resourceId, out var prior)) prior.Decoder.Dispose();
+            while (!_pendingMovies.TryAdd(playbackId, runtime))
+                if (_pendingMovies.TryRemove(playbackId, out var prior)) prior.Decoder.Dispose();
            return true;
        }
        catch (System.Exception e)
@@ -1199,50 +1289,52 @@ public partial class Main : Godot.Control

    private void AdoptPendingMovies()
    {
-        foreach (var (resourceId, _) in _pendingMovies)
+        foreach (var (playbackId, _) in _pendingMovies)
        {
-            if (!_pendingMovies.TryRemove(resourceId, out var movie)) continue;
-            if (_movies.Remove(resourceId, out var prior)) prior.Decoder.Dispose();
-            _movies[resourceId] = movie;
-            _movieCompletionNotified.Remove(resourceId);
-            GD.Print($"movie started {movie.Name} ({movie.Decoder.StopTimeMs?.ToString() ?? "unknown"} ms from VFS)");
+            if (!_pendingMovies.TryRemove(playbackId, out var movie)) continue;
+            if (_movies.Remove(playbackId, out var prior)) prior.Decoder.Dispose();
+            _movies[playbackId] = movie;
+            _movieCompletionNotified.Remove(playbackId);
+            GD.Print($"movie started {movie.Name} playback={playbackId} " +
+                     $"({movie.Decoder.StopTimeMs?.ToString() ?? "unknown"} ms from VFS)");
        }
    }

    private void UpdateMovieFrames()
    {
        if (_host == null) return;
-        foreach (var (resourceId, movie) in _movies)
+        foreach (var (playbackId, movie) in _movies)
        {
            if (movie.Decoder.TryTakeFrame(out var frame))
            {
-                _host.PublishMovieFrame(resourceId, movie.Name, movie.AssetId, frame);
-                if (_movieFrameSeen.Add(resourceId))
-                    GD.Print($"movie first frame {movie.Name}: {frame.Width}x{frame.Height} RGBA8 at render frame {_timelineFrame}");
+                _host.PublishMovieFrame(playbackId, movie.Name, movie.AssetId, frame);
+                if (_movieFrameSeen.Add(playbackId))
+                    GD.Print($"movie first frame {movie.Name} playback={playbackId}: " +
+                             $"{frame.Width}x{frame.Height} RGBA8 at render frame {_timelineFrame}");
            }
            bool watchdogExpired = Stopwatch.GetElapsedTime(movie.StartedAtTimestamp).TotalMilliseconds
                                   >= movie.WatchdogMs;
-            if ((movie.Decoder.IsCompleted || watchdogExpired) && _movieCompletionNotified.Add(resourceId))
+            if ((movie.Decoder.IsCompleted || watchdogExpired) && _movieCompletionNotified.Add(playbackId))
            {
                if (movie.Decoder.Failure is { } failure)
                    GD.Print($"movie decode failed {movie.Name}: {failure}");
                if (watchdogExpired && !movie.Decoder.IsCompleted)
                    GD.Print($"movie completion watchdog {movie.Name}: forcing completion after {movie.WatchdogMs} ms");
-                _host.NotifyMovieCompleted(resourceId);
+                _host.NotifyMovieCompleted(playbackId);
            }
        }
    }

-    public void StopMovie(long resourceId)
+    public void StopMovie(long playbackId)
    {
-        if (_pendingMovies.TryRemove(resourceId, out var pending)) pending.Decoder.Dispose();
-        if (_movies.Remove(resourceId, out var movie))
+        if (_pendingMovies.TryRemove(playbackId, out var pending)) pending.Decoder.Dispose();
+        if (_movies.Remove(playbackId, out var movie))
        {
            movie.Decoder.Dispose();
-            GD.Print($"movie stopped {movie.Name} at render frame {_timelineFrame}");
+            GD.Print($"movie stopped {movie.Name} playback={playbackId} at render frame {_timelineFrame}");
        }
-        _movieFrameSeen.Remove(resourceId);
-        _movieCompletionNotified.Remove(resourceId);
+        _movieFrameSeen.Remove(playbackId);
+        _movieCompletionNotified.Remove(playbackId);
    }

    public void AppendLine(string text) => _text.Text += text + "\n";
--- a/godot/MovieRuntime.cs
+++ b/godot/MovieRuntime.cs
@@ -3,15 +3,15 @@ using System.Diagnostics;
 using Age.Engine.Sys4;

 /// <summary>Presentation-side ownership for one decoder plus its fail-safe completion deadline.</summary>
-internal sealed record MovieRuntime(string Name, int AssetId, IMovieDecoder Decoder,
+internal sealed record MovieRuntime(string Name, int AssetId, long ResourceId, IMovieDecoder Decoder,
                                    long StartedAtTimestamp, long WatchdogMs)
 {
-    public static MovieRuntime Open(string name, int assetId, MoviePayload payload,
+    public static MovieRuntime Open(string name, int assetId, long resourceId, MoviePayload payload,
                                    IMovieDecoderFactory factory)
    {
        ArgumentNullException.ThrowIfNull(factory);
        IMovieDecoder decoder = factory.Open(payload);
-        return new MovieRuntime(name, assetId, decoder, Stopwatch.GetTimestamp(),
+        return new MovieRuntime(name, assetId, resourceId, decoder, Stopwatch.GetTimestamp(),
            decoder.StopTimeMs is >= 0 and var stopTime
                ? Math.Clamp(stopTime + 2000, 5000, 300000)
                : 30000);
--- a/godot/MovieSurfaceRegistry.cs
+++ b/godot/MovieSurfaceRegistry.cs
@@ -0,0 +1,182 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Age.Engine.Sys4;
+
+internal readonly record struct MovieSurfaceBinding(long PlaybackId, long ResourceId, int SurfaceSlot);
+internal sealed record MovieSurfaceFrame(RgbaImage Image, string Name, int AssetId);
+public sealed record MovieSurfaceDiagnostic(int SurfaceSlot, long PlaybackId, long ResourceId,
+                                            bool Completed, bool HasFrame, string? Name);
+internal enum MovieSurfaceReleaseKind { NotBound, Active, Released }
+internal readonly record struct MovieSurfaceRelease(MovieSurfaceReleaseKind Kind,
+                                                    MovieSurfaceBinding Binding);
+
+/// <summary>Instance-keyed movie/surface ownership. A resource may be played more than once concurrently;
+/// completion and frames therefore belong to a playback, never to the shared asset id.</summary>
+internal sealed class MovieSurfaceRegistry
+{
+    private readonly object _lock = new();
+    private readonly Dictionary<int, MovieSurfaceBinding> _bySurface = new();
+    private readonly Dictionary<long, MovieSurfaceBinding> _byPlayback = new();
+    private readonly Dictionary<long, MovieSurfaceFrame> _frames = new();
+    private readonly HashSet<long> _completed = new();
+    private readonly HashSet<long> _knownMovieResources = new();
+    private long _nextPlaybackId;
+
+    public MovieSurfaceBinding Begin(int surfaceSlot, long resourceId,
+                                     out MovieSurfaceBinding? replaced)
+    {
+        lock (_lock)
+        {
+            replaced = _bySurface.TryGetValue(surfaceSlot, out var prior) ? prior : null;
+            if (replaced.HasValue) RemoveLocked(prior);
+            var binding = new MovieSurfaceBinding(++_nextPlaybackId, resourceId, surfaceSlot);
+            _knownMovieResources.Add(resourceId);
+            _bySurface[surfaceSlot] = binding;
+            _byPlayback[binding.PlaybackId] = binding;
+            return binding;
+        }
+    }
+
+    public bool PublishFrame(long playbackId, RgbaImage image, string name, int assetId)
+    {
+        lock (_lock)
+        {
+            if (!_byPlayback.ContainsKey(playbackId)) return false;
+            _frames[playbackId] = new MovieSurfaceFrame(image, name, assetId);
+            return true;
+        }
+    }
+
+    public bool Complete(long playbackId)
+    {
+        lock (_lock)
+            return _byPlayback.ContainsKey(playbackId) && _completed.Add(playbackId);
+    }
+
+    public bool IsActive(int surfaceSlot)
+    {
+        lock (_lock)
+            return _bySurface.TryGetValue(surfaceSlot, out var binding)
+                && !_completed.Contains(binding.PlaybackId);
+    }
+
+    public bool IsBound(int surfaceSlot)
+    {
+        lock (_lock) return _bySurface.ContainsKey(surfaceSlot);
+    }
+
+    public bool HasActivePlayback
+    {
+        get
+        {
+            lock (_lock)
+                return _byPlayback.Keys.Any(playbackId => !_completed.Contains(playbackId));
+        }
+    }
+
+    public bool TryResolveSurface(int surfaceSlot, out MovieSurfaceFrame? frame)
+    {
+        lock (_lock)
+        {
+            if (_bySurface.TryGetValue(surfaceSlot, out var binding)
+                && _frames.TryGetValue(binding.PlaybackId, out var found))
+            {
+                frame = found;
+                return true;
+            }
+            frame = null;
+            return false;
+        }
+    }
+
+    public bool TryResolveResource(long resourceId, out MovieSurfaceFrame? frame)
+    {
+        lock (_lock)
+        {
+            foreach (var binding in _byPlayback.Values
+                         .Where(binding => binding.ResourceId == resourceId)
+                         .OrderByDescending(binding => binding.PlaybackId))
+            {
+                if (!_frames.TryGetValue(binding.PlaybackId, out var found)) continue;
+                frame = found;
+                return true;
+            }
+            frame = null;
+            return false;
+        }
+    }
+
+    /// <summary>Catalog ids are immutable within a mounted resource set. Remembering that an id entered
+    /// the typed movie path prevents a cleanup-frame render snapshot from treating its .AGF-named MPEG
+    /// payload as a still image after the last live surface binding has been detached.</summary>
+    public bool IsKnownMovieResource(long resourceId)
+    {
+        lock (_lock) return _knownMovieResources.Contains(resourceId);
+    }
+
+    public MovieSurfaceRelease ReleaseIfCompleted(int surfaceSlot)
+    {
+        lock (_lock)
+        {
+            if (!_bySurface.TryGetValue(surfaceSlot, out var binding))
+                return new MovieSurfaceRelease(MovieSurfaceReleaseKind.NotBound, default);
+            if (!_completed.Contains(binding.PlaybackId))
+                return new MovieSurfaceRelease(MovieSurfaceReleaseKind.Active, binding);
+            RemoveLocked(binding);
+            return new MovieSurfaceRelease(MovieSurfaceReleaseKind.Released, binding);
+        }
+    }
+
+    public bool Abandon(long playbackId, out MovieSurfaceBinding binding)
+    {
+        lock (_lock)
+        {
+            if (!_byPlayback.TryGetValue(playbackId, out binding)) return false;
+            RemoveLocked(binding);
+            return true;
+        }
+    }
+
+    public IReadOnlyList<MovieSurfaceBinding> ReleaseRange(int firstSlot, int count)
+    {
+        int end = checked(firstSlot + count);
+        lock (_lock)
+        {
+            var released = _bySurface.Values
+                .Where(binding => binding.SurfaceSlot >= firstSlot && binding.SurfaceSlot < end)
+                .OrderBy(binding => binding.SurfaceSlot)
+                .ToArray();
+            foreach (var binding in released) RemoveLocked(binding);
+            return released;
+        }
+    }
+
+    public IReadOnlyList<MovieSurfaceDiagnostic> Snapshot()
+    {
+        lock (_lock)
+            return _bySurface.Values
+                .OrderBy(binding => binding.SurfaceSlot)
+                .Select(binding => new MovieSurfaceDiagnostic(
+                    binding.SurfaceSlot,
+                    binding.PlaybackId,
+                    binding.ResourceId,
+                    _completed.Contains(binding.PlaybackId),
+                    _frames.ContainsKey(binding.PlaybackId),
+                    _frames.TryGetValue(binding.PlaybackId, out var frame) ? frame.Name : null))
+                .ToArray();
+    }
+
+    public IReadOnlyList<long> CompletedPlaybackIds()
+    {
+        lock (_lock) return _completed.OrderBy(id => id).ToArray();
+    }
+
+    private void RemoveLocked(MovieSurfaceBinding binding)
+    {
+        _bySurface.Remove(binding.SurfaceSlot);
+        _byPlayback.Remove(binding.PlaybackId);
+        _frames.Remove(binding.PlaybackId);
+        _completed.Remove(binding.PlaybackId);
+    }
+}
--- a/tools/movie-corpus-gate/Age.MovieCorpusGate.csproj
+++ b/tools/movie-corpus-gate/Age.MovieCorpusGate.csproj
@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <NuGetAudit>false</NuGetAudit>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\engine\Age.Engine\Age.Engine.csproj" />
+    <Compile Include="..\..\godot\FfmpegMovieNative.cs" Link="FfmpegMovieNative.cs" />
+  </ItemGroup>
+</Project>
--- a/tools/movie-corpus-gate/MovieCorpusGate.cs
+++ b/tools/movie-corpus-gate/MovieCorpusGate.cs
@@ -0,0 +1,228 @@
+using System.Diagnostics;
+using Age.Engine.Sys4;
+
+internal sealed record MovieCorpusInput(long PackedId, string Name, Func<MoviePayload> ReadPayload);
+
+internal sealed record MovieCorpusItemResult(
+    long PackedId,
+    string PackedIdHex,
+    string Name,
+    long PayloadBytes,
+    int ExpectedWidth,
+    int ExpectedHeight,
+    int Width,
+    int Height,
+    long StopTimeMs,
+    int FrameRateNumerator,
+    int FrameRateDenominator,
+    bool HasAudio,
+    long FrameCount,
+    long FirstPresentationTimeMs,
+    long LastPresentationTimeMs,
+    bool FramesChanged,
+    long ReadMilliseconds,
+    long OpenMilliseconds,
+    long DecodeMilliseconds,
+    long DisposeMilliseconds,
+    bool Passed,
+    string? Error);
+
+internal sealed record MovieCorpusReport(
+    string StartedUtc,
+    string CompletedUtc,
+    int ExpectedCount,
+    int CandidateCount,
+    int PassedCount,
+    int FailedCount,
+    long ElapsedMilliseconds,
+    bool Passed,
+    IReadOnlyList<string> SelectionErrors,
+    IReadOnlyList<MovieCorpusItemResult> Movies);
+
+internal static class MovieCorpusDiscovery
+{
+    private static ReadOnlySpan<byte> MpegPackStart => [0, 0, 1, 0xba];
+
+    public static IReadOnlyList<PackedAssetEntry> DiscoverMpegMovies(
+        Sys4AssetCatalog catalog, IAssetStore store)
+    {
+        var movies = new List<PackedAssetEntry>();
+        Span<byte> signature = stackalloc byte[4];
+        foreach (var packed in catalog.EnumerateAssets())
+        {
+            if (!packed.Asset.Name.EndsWith(".AGF", StringComparison.OrdinalIgnoreCase)) continue;
+            using Stream stream = store.Open(packed.Asset);
+            int length = 0;
+            while (length < signature.Length)
+            {
+                int read = stream.Read(signature[length..]);
+                if (read == 0) break;
+                length += read;
+            }
+            if (length == signature.Length && signature.SequenceEqual(MpegPackStart)) movies.Add(packed);
+        }
+        return movies;
+    }
+
+    public static bool TryReadSequenceDimensions(ReadOnlySpan<byte> payload, out int width, out int height)
+    {
+        for (int offset = 0; offset <= payload.Length - 7; offset++)
+        {
+            if (payload[offset] != 0 || payload[offset + 1] != 0
+                || payload[offset + 2] != 1 || payload[offset + 3] != 0xb3) continue;
+            width = (payload[offset + 4] << 4) | (payload[offset + 5] >> 4);
+            height = ((payload[offset + 5] & 0x0f) << 8) | payload[offset + 6];
+            return width > 0 && height > 0;
+        }
+        width = 0;
+        height = 0;
+        return false;
+    }
+}
+
+internal sealed class MovieCorpusGate
+{
+    private readonly Func<MoviePayload, IFfmpegFrameSource> _open;
+
+    public MovieCorpusGate(Func<MoviePayload, IFfmpegFrameSource> open)
+        => _open = open ?? throw new ArgumentNullException(nameof(open));
+
+    public MovieCorpusReport Run(IReadOnlyList<MovieCorpusInput> inputs, int expectedCount,
+                                 long maximumItemMilliseconds,
+                                 Action<int, int, MovieCorpusItemResult>? progress = null)
+    {
+        if (expectedCount < 0) throw new ArgumentOutOfRangeException(nameof(expectedCount));
+        if (maximumItemMilliseconds <= 0) throw new ArgumentOutOfRangeException(nameof(maximumItemMilliseconds));
+        DateTimeOffset started = DateTimeOffset.UtcNow;
+        var total = Stopwatch.StartNew();
+        var selectionErrors = new List<string>();
+        if (inputs.Count != expectedCount)
+            selectionErrors.Add($"expected {expectedCount} MPEG movies, discovered {inputs.Count}");
+
+        var results = new List<MovieCorpusItemResult>(inputs.Count);
+        for (int index = 0; index < inputs.Count; index++)
+        {
+            MovieCorpusItemResult result = RunOne(inputs[index], maximumItemMilliseconds);
+            results.Add(result);
+            progress?.Invoke(index + 1, inputs.Count, result);
+        }
+
+        total.Stop();
+        int passed = results.Count(result => result.Passed);
+        int failed = results.Count - passed;
+        return new MovieCorpusReport(
+            started.ToString("O"), DateTimeOffset.UtcNow.ToString("O"), expectedCount, inputs.Count,
+            passed, failed, total.ElapsedMilliseconds, selectionErrors.Count == 0 && failed == 0,
+            selectionErrors, results);
+    }
+
+    private MovieCorpusItemResult RunOne(MovieCorpusInput input, long maximumItemMilliseconds)
+    {
+        long payloadBytes = 0;
+        int expectedWidth = 0, expectedHeight = 0, width = 0, height = 0;
+        long stopTimeMs = 0, frameCount = 0, firstPts = -1, lastPts = -1;
+        int frameRateNumerator = 0, frameRateDenominator = 0;
+        bool hasAudio = false, framesChanged = false;
+        long readMs = 0, openMs = 0, decodeMs = 0, disposeMs = 0;
+        string? error = null;
+        IFfmpegFrameSource? source = null;
+        var itemTime = Stopwatch.StartNew();
+
+        try
+        {
+            var phase = Stopwatch.StartNew();
+            MoviePayload payload = input.ReadPayload();
+            phase.Stop();
+            readMs = phase.ElapsedMilliseconds;
+            payloadBytes = payload.Bytes.LongLength;
+            if (!MovieCorpusDiscovery.TryReadSequenceDimensions(payload.Bytes, out expectedWidth, out expectedHeight))
+                throw new InvalidDataException("MPEG sequence header was not found");
+
+            phase.Restart();
+            source = _open(payload);
+            phase.Stop();
+            openMs = phase.ElapsedMilliseconds;
+            FfmpegMovieInfo info = source.Info;
+            width = info.Width;
+            height = info.Height;
+            stopTimeMs = info.StopTimeMs;
+            frameRateNumerator = info.FrameRateNumerator;
+            frameRateDenominator = info.FrameRateDenominator;
+            hasAudio = info.HasAudio;
+            if (width != expectedWidth || height != expectedHeight)
+                throw new InvalidDataException(
+                    $"decoder dimensions {width}x{height} differ from MPEG sequence {expectedWidth}x{expectedHeight}");
+            if (width <= 0 || height <= 0 || stopTimeMs <= 0
+                || frameRateNumerator <= 0 || frameRateDenominator <= 0)
+                throw new InvalidDataException(
+                    $"invalid metadata {width}x{height}, {stopTimeMs} ms, " +
+                    $"rate {frameRateNumerator}/{frameRateDenominator}");
+
+            var decodeTime = Stopwatch.StartNew();
+            byte[]? firstPixels = null;
+            try
+            {
+                while (source.TryDecodeNextVideoFrame(out FfmpegVideoFrame frame))
+                {
+                    if (frame.Image.Width != width || frame.Image.Height != height)
+                        throw new InvalidDataException(
+                            $"frame {frameCount} dimensions are {frame.Image.Width}x{frame.Image.Height}, expected {width}x{height}");
+                    int expectedBytes = checked(width * height * 4);
+                    if (frame.Image.Pixels.Length != expectedBytes)
+                        throw new InvalidDataException(
+                            $"frame {frameCount} has {frame.Image.Pixels.Length} RGBA bytes, expected {expectedBytes}");
+                    if (frame.PresentationTimeMs < 0 || frame.PresentationTimeMs < lastPts)
+                        throw new InvalidDataException(
+                            $"frame {frameCount} timestamp {frame.PresentationTimeMs} follows {lastPts}");
+
+                    if (frameCount == 0)
+                    {
+                        firstPts = frame.PresentationTimeMs;
+                        firstPixels = frame.Image.Pixels;
+                    }
+                    else if (!framesChanged && !frame.Image.Pixels.AsSpan().SequenceEqual(firstPixels))
+                        framesChanged = true;
+                    lastPts = frame.PresentationTimeMs;
+                    frameCount++;
+                    if (itemTime.ElapsedMilliseconds > maximumItemMilliseconds)
+                        throw new TimeoutException($"item exceeded {maximumItemMilliseconds} ms before EOF");
+                }
+            }
+            finally
+            {
+                decodeTime.Stop();
+                decodeMs = decodeTime.ElapsedMilliseconds;
+            }
+            if (frameCount == 0) throw new InvalidDataException("decoder reached EOF without a video frame");
+        }
+        catch (Exception exception)
+        {
+            error = exception.Message;
+        }
+        finally
+        {
+            if (source != null)
+            {
+                var disposeTime = Stopwatch.StartNew();
+                try { source.Dispose(); }
+                catch (Exception exception)
+                {
+                    error = error == null ? $"dispose failed: {exception.Message}"
+                                          : $"{error}; dispose failed: {exception.Message}";
+                }
+                disposeTime.Stop();
+                disposeMs = disposeTime.ElapsedMilliseconds;
+            }
+        }
+
+        itemTime.Stop();
+        if (error == null && itemTime.ElapsedMilliseconds > maximumItemMilliseconds)
+            error = $"item took {itemTime.ElapsedMilliseconds} ms, limit is {maximumItemMilliseconds} ms";
+        return new MovieCorpusItemResult(
+            input.PackedId, $"0x{input.PackedId:x}", input.Name, payloadBytes,
+            expectedWidth, expectedHeight, width, height, stopTimeMs,
+            frameRateNumerator, frameRateDenominator, hasAudio, frameCount, firstPts, lastPts,
+            framesChanged, readMs, openMs, decodeMs, disposeMs, error == null, error);
+    }
+
+}
--- a/tools/movie-corpus-gate/Program.cs
+++ b/tools/movie-corpus-gate/Program.cs
@@ -0,0 +1,60 @@
+using System.Text.Json;
+using Age.Engine.Sys4;
+
+static string? Option(string[] arguments, string name)
+{
+    int index = Array.IndexOf(arguments, name);
+    return index >= 0 && index + 1 < arguments.Length ? arguments[index + 1] : null;
+}
+
+if (args.Contains("--help"))
+{
+    Console.WriteLine("usage: dotnet run --project tools/movie-corpus-gate -- [--output <json>] [--native-dir <dir>] [--expected-count 213] [--max-item-ms 30000]");
+    return 0;
+}
+
+string output = Path.GetFullPath(Option(args, "--output")
+                                 ?? Path.Combine(Paths.Build, "movie-corpus-ffmpeg.json"));
+string nativeDirectory = Path.GetFullPath(Option(args, "--native-dir")
+                                          ?? Path.Combine(Paths.Build, "native", "win-x64"));
+int expectedCount = int.Parse(Option(args, "--expected-count") ?? "213");
+long maximumItemMilliseconds = long.Parse(Option(args, "--max-item-ms") ?? "30000");
+string nativeLibrary = Path.Combine(nativeDirectory, OperatingSystem.IsWindows()
+    ? "age_movie_ffmpeg.dll" : OperatingSystem.IsMacOS()
+        ? "libage_movie_ffmpeg.dylib" : "libage_movie_ffmpeg.so");
+if (!File.Exists(nativeLibrary))
+{
+    Console.Error.WriteLine($"native movie shim not found: {nativeLibrary}");
+    return 2;
+}
+Environment.SetEnvironmentVariable("AGE_FFMPEG_NATIVE_DIR", nativeDirectory);
+
+var catalog = Sys4AssetCatalog.Load(Paths.Sys4Ini);
+var store = new Sys4AssetStore(catalog, Paths.GameDir, Paths.GameDir);
+var resources = new ResourceMap(catalog, store);
+Console.WriteLine("discovering MPEG program streams from .AGF catalog entries...");
+var discovered = MovieCorpusDiscovery.DiscoverMpegMovies(catalog, store);
+var inputs = discovered.Select(packed => new MovieCorpusInput(
+    packed.PackedId, packed.Asset.Name, () => resources.ReadMovie(packed.Asset))).ToArray();
+Console.WriteLine($"discovered {inputs.Length} movies; decoding every frame without presentation waits");
+
+var gate = new MovieCorpusGate(payload => new FfmpegMovieSession(payload));
+MovieCorpusReport report = gate.Run(inputs, expectedCount, maximumItemMilliseconds,
+    (index, count, item) => Console.WriteLine(
+        $"[{index,3}/{count}] {(item.Passed ? "PASS" : "FAIL")} {item.PackedIdHex,-10} {item.Name,-16} " +
+        $"{item.Width}x{item.Height} {item.FrameCount}f {item.StopTimeMs}ms decode={item.DecodeMilliseconds}ms" +
+        (item.Error == null ? "" : $" :: {item.Error}")));
+
+string? parent = Path.GetDirectoryName(output);
+if (!string.IsNullOrEmpty(parent)) Directory.CreateDirectory(parent);
+var jsonOptions = new JsonSerializerOptions
+{
+    WriteIndented = true,
+    PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+};
+File.WriteAllText(output, JsonSerializer.Serialize(report, jsonOptions));
+Console.WriteLine($"summary: {report.PassedCount}/{report.CandidateCount} passed, " +
+                  $"{report.FailedCount} failed in {report.ElapsedMilliseconds} ms");
+foreach (string error in report.SelectionErrors) Console.Error.WriteLine("selection: " + error);
+Console.WriteLine("report: " + output);
+return report.Passed ? 0 : 1;