diff --git a/engine/Age.Cli/Program.cs b/engine/Age.Cli/Program.cs
index babe1cb..eb0655b 100644
--- a/engine/Age.Cli/Program.cs
+++ b/engine/Age.Cli/Program.cs
@@ -250,6 +250,7 @@ sealed class AudioTraceHost : IHost
     }
     public void ShowText(int offset, string text) { }
     public void WaitForInput() { }
+    public void Sleep(long duration) { }
     public void CreateTexture(int slot, int width, int height) { }
     public void SetTexture(long resourceId, int slot) { }
     public void DrawTexture(int slot, int srcX, int srcY, int width, int height, int dstX, int dstY) { }
@@ -298,6 +299,7 @@ sealed class GfxTraceHost : IHost
     }
     public void ShowText(int offset, string text) { }
     public void WaitForInput() { }
+    public void Sleep(long duration) { }
     public void PlayBgm(long id) { }
     public void PlayVoice(long id) { }
 }
diff --git a/engine/Age.Engine.Tests/CallScriptIntegrationTests.cs b/engine/Age.Engine.Tests/CallScriptIntegrationTests.cs
index 593337b..9e9ebe8 100644
--- a/engine/Age.Engine.Tests/CallScriptIntegrationTests.cs
+++ b/engine/Age.Engine.Tests/CallScriptIntegrationTests.cs
@@ -9,6 +9,7 @@ public class CallScriptIntegrationTests
     {
         public void ShowText(int o, string t) { }
         public void WaitForInput() { }
+        public void Sleep(long duration) { }
         public void CreateTexture(int s, int w, int h) { }
         public void SetTexture(long r, int s) { }
         public void DrawTexture(int s, int sx, int sy, int w, int h, int dx, int dy) { }
diff --git a/engine/Age.Engine.Tests/CallScriptIntegrationTests.cs.bak b/engine/Age.Engine.Tests/CallScriptIntegrationTests.cs.bak
new file mode 100644
index 0000000..593337b
--- /dev/null
+++ b/engine/Age.Engine.Tests/CallScriptIntegrationTests.cs.bak
@@ -0,0 +1,49 @@
+using Age.Engine.Hosting;
+using Age.Engine.Sys4;
+using Age.Engine.Vm;
+using Xunit;
+
+public class CallScriptIntegrationTests
+{
+    private sealed class NullHost : IHost
+    {
+        public void ShowText(int o, string t) { }
+        public void WaitForInput() { }
+        public void CreateTexture(int s, int w, int h) { }
+        public void SetTexture(long r, int s) { }
+        public void DrawTexture(int s, int sx, int sy, int w, int h, int dx, int dy) { }
+        public (int Width, int Height) GetTextureSize(int s) => (0, 0);
+        public void PlayBgm(long id) { }
+        public void PlayVoice(long id) { }
+    }
+
+    [Fact]
+    public void RealScriptExecutesRealSubroutinesAndReturns()
+    {
+        // ADDILL.BIN unconditionally call-scripts ADDILLSUB then CALCREVISE at entry, then exits.
+        // With execution on, both subroutines load, run, and return, so ADDILL reaches its own exit.
+        var t = OpcodeTableJson.Load(Paths.OpcodesJson);
+        var provider = Sys4ScriptProvider.Load(t);
+        var script = Sys4Loader.Load(Paths.Scripts()["ADDILL.BIN"], t);
+        var host = new NullHost();
+        var vm = new VirtualMachine(script, t, host, null, provider);
+        vm.Run();
+        Assert.Equal(2, vm.CallScriptDispatches); // ADDILLSUB + CALCREVISE both dispatched
+        Assert.Equal("exit", vm.HaltReason);      // subroutines returned; ADDILL reached its own exit
+    }
+
+    [Fact]
+    public void BunkiTopLevelRetReturnsCleanlyAsSubroutine()
+    {
+        // BUNKI.BIN ends with a top-level `ret` (empty intra-call stack). Called as a subroutine it
+        // must return to the caller, not underflow-halt. Drive it directly.
+        var t = OpcodeTableJson.Load(Paths.OpcodesJson);
+        var provider = Sys4ScriptProvider.Load(t);
+        var bunki = provider.GetById(0x143);   // BUNKI.BIN
+        Assert.NotNull(bunki);
+        var vm = new VirtualMachine(bunki!, t, new NullHost(), null, provider);
+        vm.Run();
+        // Reaching a frame-return at the top = clean "exit"; never "ret-underflow".
+        Assert.NotEqual("ret-underflow", vm.HaltReason);
+    }
+}
diff --git a/engine/Age.Engine.Tests/CallScriptTests.cs b/engine/Age.Engine.Tests/CallScriptTests.cs
index b3a83b6..07ef8bb 100644
--- a/engine/Age.Engine.Tests/CallScriptTests.cs
+++ b/engine/Age.Engine.Tests/CallScriptTests.cs
@@ -15,6 +15,7 @@ public class CallScriptTests
     {
         public void ShowText(int o, string t) { }
         public void WaitForInput() { }
+        public void Sleep(long duration) { }
         public void CreateTexture(int s, int w, int h) { }
         public void SetTexture(long r, int s) { }
         public void DrawTexture(int s, int sx, int sy, int w, int h, int dx, int dy) { }
diff --git a/engine/Age.Engine.Tests/CallScriptTests.cs.bak b/engine/Age.Engine.Tests/CallScriptTests.cs.bak
new file mode 100644
index 0000000..b3a83b6
--- /dev/null
+++ b/engine/Age.Engine.Tests/CallScriptTests.cs.bak
@@ -0,0 +1,106 @@
+using System.Collections.Generic;
+using Age.Engine.Hosting;
+using Age.Engine.Model;
+using Age.Engine.Sys4;
+using Age.Engine.Vm;
+using Xunit;
+
+public class CallScriptTests
+{
+    // Opcodes (from build/opcodes.json): exit=0x2, call-script=0x3(argc1), mov=0x55(argc2).
+    // Operand types: imm=0, global-int=3, local-int=9.
+    private const uint OP_EXIT = 0x2, OP_CALLSCRIPT = 0x3, OP_MOV = 0x55;
+
+    private sealed class NullHost : IHost
+    {
+        public void ShowText(int o, string t) { }
+        public void WaitForInput() { }
+        public void CreateTexture(int s, int w, int h) { }
+        public void SetTexture(long r, int s) { }
+        public void DrawTexture(int s, int sx, int sy, int w, int h, int dx, int dy) { }
+        public (int Width, int Height) GetTextureSize(int s) => (0, 0);
+        public void PlayBgm(long id) { }
+        public void PlayVoice(long id) { }
+    }
+
+    private sealed class MapProvider : IScriptProvider
+    {
+        private readonly Dictionary<long, Script> _m;
+        public MapProvider(Dictionary<long, Script> m) => _m = m;
+        public Script? GetById(long id) => _m.TryGetValue(id, out var s) ? s : null;
+    }
+
+    // Build a Script from raw dwords via the real loader (guarantees identical decode).
+    private static Script Asm(OpcodeTable t, string name, params uint[] body)
+    {
+        var bytes = new byte[0x3C + body.Length * 4];
+        System.Text.Encoding.ASCII.GetBytes("SYS4422 ").CopyTo(bytes, 0);
+        // fields[8] (F8 = code end) at header offset 8 + 8*4 = 0x28; set to body length (all code).
+        System.BitConverter.GetBytes(body.Length).CopyTo(bytes, 8 + 8 * 4);
+        for (int i = 0; i < body.Length; i++) System.BitConverter.GetBytes(body[i]).CopyTo(bytes, 0x3C + i * 4);
+        return Sys4Loader.Parse(bytes, t, name);
+    }
+
+    private static OpcodeTable Table() => OpcodeTableJson.Load(Paths.OpcodesJson);
+
+    [Fact]
+    public void CalleeRunsAndControlResumesAfterTheCall()
+    {
+        var t = Table();
+        // Callee (id 5): mov g[0x10] = 7, then exit.
+        var callee = Asm(t, "CALLEE", OP_MOV, 3, 0x10, 0, 7, OP_EXIT);
+        // Caller: call-script 5 ; mov g[0x11] = g[0x10] ; exit.
+        var caller = Asm(t, "CALLER",
+            OP_CALLSCRIPT, 0, 5,
+            OP_MOV, 3, 0x11, 3, 0x10,
+            OP_EXIT);
+        var host = new NullHost();
+        var sink = new RecordingTraceSink();
+        var vm = new VirtualMachine(caller, t, host, null, new MapProvider(new() { [5] = callee }), sink);
+        vm.Run();
+        Assert.Equal(7, vm.Globals[0x10]);           // callee wrote a shared global
+        Assert.Equal(7, vm.Globals[0x11]);           // caller read it AFTER the call returned
+        Assert.Equal("exit", vm.HaltReason);         // top-level exit
+        Assert.Contains(5L, sink.CallScriptIds);     // dispatch observed via the trace sink
+    }
+
+    [Fact]
+    public void MissingProviderFallsBackToStub()
+    {
+        var t = Table();
+        var caller = Asm(t, "CALLER", OP_CALLSCRIPT, 0, 5, OP_EXIT);
+        var host = new NullHost();
+        var sink = new RecordingTraceSink();
+        var vm = new VirtualMachine(caller, t, host, null, null, sink);   // no provider
+        vm.Run();
+        Assert.Equal("exit", vm.HaltReason);        // did not halt on the call; stub + continue
+        Assert.Contains(5L, sink.CallScriptIds);
+    }
+
+    [Fact]
+    public void UnresolvedIdHalts()
+    {
+        var t = Table();
+        var caller = Asm(t, "CALLER", OP_CALLSCRIPT, 0, 99, OP_EXIT);
+        var vm = new VirtualMachine(caller, t, new NullHost(), null, new MapProvider(new()));
+        vm.Run();
+        Assert.StartsWith("callscript-unresolved", vm.HaltReason);
+    }
+
+    [Fact]
+    public void LocalsDoNotLeakBetweenCallerAndCallee()
+    {
+        var t = Table();
+        // Callee writes LOCAL-int 0 = 42 (mov to local-int, type 9), then exit.
+        var callee = Asm(t, "CALLEE", OP_MOV, 9, 0, 0, 42, OP_EXIT);
+        // Caller sets local-int 0 = 1, calls, then copies its own local-int 0 to global 0x20.
+        var caller = Asm(t, "CALLER",
+            OP_MOV, 9, 0, 0, 1,                  // l[0] = 1
+            OP_CALLSCRIPT, 0, 5,                 // call-script 5 (callee sets ITS local 0 = 42)
+            OP_MOV, 3, 0x20, 9, 0,               // g[0x20] = l[0]
+            OP_EXIT);
+        var vm = new VirtualMachine(caller, t, new NullHost(), null, new MapProvider(new() { [5] = callee }));
+        vm.Run();
+        Assert.Equal(1, vm.Globals[0x20]);   // caller's local 0 unchanged by callee's local 0
+    }
+}
diff --git a/engine/Age.Engine.Tests/GameSessionTests.cs b/engine/Age.Engine.Tests/GameSessionTests.cs
index bfd440e..a7b9d12 100644
--- a/engine/Age.Engine.Tests/GameSessionTests.cs
+++ b/engine/Age.Engine.Tests/GameSessionTests.cs
@@ -29,6 +29,7 @@ public class GameSessionTests
         public List<int> Emitted = new();
         public void ShowText(int o, string t) => Emitted.Add(o);
         public void WaitForInput() { }
+        public void Sleep(long duration) { }
         public void CreateTexture(int s, int w, int h) { }
         public void SetTexture(long r, int s) { }
         public void DrawTexture(int s, int sx, int sy, int w, int h, int dx, int dy) { }
diff --git a/engine/Age.Engine.Tests/GameSessionTests.cs.bak b/engine/Age.Engine.Tests/GameSessionTests.cs.bak
new file mode 100644
index 0000000..bfd440e
--- /dev/null
+++ b/engine/Age.Engine.Tests/GameSessionTests.cs.bak
@@ -0,0 +1,132 @@
+using System.Collections.Generic;
+using System.Linq;
+using Age.Engine.Hosting;
+using Age.Engine.Model;
+using Age.Engine.Sys4;
+using Age.Engine.Vm;
+using Xunit;
+
+public class GameSessionTests
+{
+    private const int T_IMM = 0, T_GINT = 3;
+    private static readonly OpcodeTable Table = OpcodeTableJson.Load(Paths.OpcodesJson);
+
+    // A minimal one-instruction script: `mov (global-int dst) src`. Halts pc-out-of-range after.
+    private static Script MovScript(int dst, int srcType, long srcVal) => new()
+    {
+        Header = new ScriptHeader(0, 0, 0, 0, 0, 0),
+        Instructions = new[]
+        {
+            new Instruction(0, 0x55, new[] { new Operand(T_GINT, dst), new Operand(srcType, srcVal) }),
+        },
+        IndexByOffset = new Dictionary<int, int> { { 0, 0 } },
+        Strings = new Dictionary<int, string>(),
+    };
+
+    private sealed class VoiceCountHost : IHost
+    {
+        public int Voices;
+        public List<int> Emitted = new();
+        public void ShowText(int o, string t) => Emitted.Add(o);
+        public void WaitForInput() { }
+        public void CreateTexture(int s, int w, int h) { }
+        public void SetTexture(long r, int s) { }
+        public void DrawTexture(int s, int sx, int sy, int w, int h, int dx, int dy) { }
+        public (int Width, int Height) GetTextureSize(int slot) => (0, 0);
+        public void PlayBgm(long id) { }
+        public void PlayVoice(long id) => Voices++;
+    }
+
+    [Fact]
+    public void StatePersistsAcrossScenes()
+    {
+        var session = new GameSession();
+        // Scene A writes G[0x5000] = 42.
+        session.RunScene(MovScript(0x5000, T_IMM, 0x2a), Table, new CaptureHost());
+        Assert.Equal(0x2a, session.Globals[0x5000]);
+        // Scene B copies G[0x5000] -> G[0x5001]; it must SEE A's write.
+        session.RunScene(MovScript(0x5001, T_GINT, 0x5000), Table, new CaptureHost());
+        Assert.Equal(0x2a, session.Globals[0x5001]);
+    }
+
+    [Fact]
+    public void SeedIsVisibleToTheScene()
+    {
+        var session = new GameSession();
+        session.Seed(0x5000, 99);
+        session.RunScene(MovScript(0x5001, T_GINT, 0x5000), Table, new CaptureHost());
+        Assert.Equal(99, session.Globals[0x5001]);
+    }
+
+    [Fact]
+    public void SC0000ViaSessionMatchesSingleRun()
+    {
+        var script = Sys4Loader.Load(Paths.Scripts()["SC0000.BIN"], Table);
+        // single run
+        var host1 = new CaptureHost();
+        new VirtualMachine(script, Table, host1).Run();
+        var single = host1.Emitted.Select(e => e.Offset).ToList();
+        // via session
+        var host2 = new CaptureHost();
+        var r = new GameSession().RunScene(Sys4Loader.Load(Paths.Scripts()["SC0000.BIN"], Table), Table, host2);
+        var viaSession = r.Emitted.Select(e => e.Offset).ToList();
+        Assert.Equal(single, viaSession);
+        Assert.Equal("exit", r.Halt);
+    }
+
+    [Fact]
+    public void BootingSkinitPopulatesDataTableGlobals()
+    {
+        // Running the SKINIT data script through the session populates the real skill table into the
+        // global bank (the game's boot behavior). Cross-check vs the static extraction (build/data/SKINIT.json):
+        // skill 0 = "飛行" at global-string 0x23a3, field G[0xa6e5b] = 30.
+        var session = new GameSession();
+        var r = session.RunScene(Sys4Loader.Load(Paths.Scripts()["SKINIT.BIN"], Table), Table, new CaptureHost());
+        Assert.Equal("exit", r.Halt);
+        Assert.Equal("飛行", session.GlobalStrings[0x23a3]);
+        Assert.Equal(30, session.Globals[0xa6e5b]);
+        Assert.True(session.Globals.Count > 1000, $"SKINIT should populate the skill table (got {session.Globals.Count})");
+    }
+
+    [Fact]
+    public void SnapshotRoundTripsState()
+    {
+        var s = new GameSession();
+        s.Seed(0x10, 42); s.Seed(0x20, -7); s.SeedString(0x30, "リリィ");
+        var t = GameSession.FromJson(s.ToJson());
+        Assert.Equal(42, t.Globals[0x10]);
+        Assert.Equal(-7, t.Globals[0x20]);
+        Assert.Equal("リリィ", t.GlobalStrings[0x30]);
+        Assert.Equal(s.Globals.Count, t.Globals.Count);
+    }
+
+    [Fact]
+    public void BootedStateSurvivesSnapshot()
+    {
+        var s = new GameSession();
+        s.RunScene(Sys4Loader.Load(Paths.Scripts()["SKINIT.BIN"], Table), Table, new CaptureHost());
+        var t = GameSession.FromJson(s.ToJson());   // snapshot the expensive booted state, rebuild
+        Assert.Equal("飛行", t.GlobalStrings[0x23a3]);
+        Assert.Equal(30, t.Globals[0xa6e5b]);
+        Assert.Equal(s.Globals.Count, t.Globals.Count);
+        Assert.Equal(s.GlobalStrings.Count, t.GlobalStrings.Count);
+    }
+
+    [Fact]
+    public void SeedingFormFlagChangesBehavior()
+    {
+        // Lily's lines are gated on form flags G[0xa57/8/9]; unseeded => all skipped (0 voices on her lines).
+        // Seeding form A (0xa57=1) makes her lines execute -> more play-voice calls. Proven finding (audio).
+        var scriptPath = Paths.Scripts()["SC0000.BIN"];
+        var unseeded = new VoiceCountHost();
+        new GameSession().RunScene(Sys4Loader.Load(scriptPath, Table), Table, unseeded);
+
+        var s = new GameSession();
+        s.Seed(0xa57, 1);
+        var seeded = new VoiceCountHost();
+        s.RunScene(Sys4Loader.Load(scriptPath, Table), Table, seeded);
+
+        Assert.True(seeded.Voices > unseeded.Voices,
+            $"seeding form flag should fire more voices: unseeded={unseeded.Voices} seeded={seeded.Voices}");
+    }
+}
diff --git a/engine/Age.Engine.Tests/SleepDispatchTests.cs b/engine/Age.Engine.Tests/SleepDispatchTests.cs
new file mode 100644
index 0000000..c2153a0
--- /dev/null
+++ b/engine/Age.Engine.Tests/SleepDispatchTests.cs
@@ -0,0 +1,27 @@
+using System.Collections.Generic;
+using Age.Engine.Model;
+using Age.Engine.Sys4;
+using Age.Engine.Vm;
+using Xunit;
+
+public class SleepDispatchTests
+{
+    [Fact]
+    public void SleepOp_ForwardsRawOperand_ToHost_AndAdvancesLikeNoop()
+    {
+        var table = OpcodeTableJson.Load(Paths.OpcodesJson);
+        (int, Operand[]) Sleep(long ms) => (0xc8, new[] { new Operand(0, ms) });
+        (int, Operand[]) Show(int s) => (0x6e, new[] { new Operand(2, s), new Operand(0, 0) });
+        (int, Operand[]) Exit() => (0x2, System.Array.Empty<Operand>());
+
+        var script = ScriptAssembler.Assemble(table, "SLEEPTEST",
+            new List<(int, Operand[])> { Sleep(200), Show(0), Sleep(1000), Exit() }, new[] { "hi" });
+
+        var host = new RecordingHost();
+        var vm = new VirtualMachine(script, table, host);
+        vm.Run();
+
+        Assert.Equal(new List<long> { 200, 1000 }, host.SleptDurations);
+        Assert.Single(host.Lines);                        // the show-text between the sleeps still ran
+    }
+}
diff --git a/engine/Age.Engine.Tests/TestSupport.cs b/engine/Age.Engine.Tests/TestSupport.cs
index 2ff20e3..5eb70e4 100644
--- a/engine/Age.Engine.Tests/TestSupport.cs
+++ b/engine/Age.Engine.Tests/TestSupport.cs
@@ -10,8 +10,10 @@ internal sealed class RecordingHost : IHost
 {
     public int Waits;
     public readonly List<(int Offset, string Text)> Lines = new();
+    public readonly List<long> SleptDurations = new();
     public void ShowText(int offset, string text) => Lines.Add((offset, text));
     public void WaitForInput() => Waits++;
+    public void Sleep(long duration) => SleptDurations.Add(duration);
     public void CreateTexture(int slot, int w, int h) { }
     public void SetTexture(long resId, int slot) { }
     public void DrawTexture(int slot, int sx, int sy, int w, int h, int dx, int dy) { }
diff --git a/engine/Age.Engine.Tests/TextureGeometryTests.cs b/engine/Age.Engine.Tests/TextureGeometryTests.cs
index 2ee9eba..19dc63a 100644
--- a/engine/Age.Engine.Tests/TextureGeometryTests.cs
+++ b/engine/Age.Engine.Tests/TextureGeometryTests.cs
@@ -11,6 +11,7 @@ public class TextureGeometryTests
     {
         public void ShowText(int o, string t) { }
         public void WaitForInput() { }
+        public void Sleep(long duration) { }
         public void CreateTexture(int slot, int w, int h) { }
         public void SetTexture(long resId, int slot) { }
         public void DrawTexture(int slot, int sx, int sy, int w, int h, int dx, int dy) { }
diff --git a/engine/Age.Engine.Tests/TextureGeometryTests.cs.bak b/engine/Age.Engine.Tests/TextureGeometryTests.cs.bak
new file mode 100644
index 0000000..2ee9eba
--- /dev/null
+++ b/engine/Age.Engine.Tests/TextureGeometryTests.cs.bak
@@ -0,0 +1,44 @@
+using System.Collections.Generic;
+using Age.Engine.Hosting;
+using Age.Engine.Model;
+using Age.Engine.Sys4;
+using Age.Engine.Vm;
+using Xunit;
+
+public class TextureGeometryTests
+{
+    private sealed class FakeSizeHost : IHost
+    {
+        public void ShowText(int o, string t) { }
+        public void WaitForInput() { }
+        public void CreateTexture(int slot, int w, int h) { }
+        public void SetTexture(long resId, int slot) { }
+        public void DrawTexture(int slot, int sx, int sy, int w, int h, int dx, int dy) { }
+        public void PlayBgm(long id) { }
+        public void PlayVoice(long id) { }
+        public (int Width, int Height) GetTextureSize(int slot) => (0x140, 0xC8);
+    }
+
+    [Fact]
+    public void GetTextureSizeWritesHostDimsIntoOutputGlobals()
+    {
+        var table = OpcodeTableJson.Load(Paths.OpcodesJson);
+        // 0x208 (global-int 50)(global-int 60)(global-int 61): slot=50, out_w=G[60], out_h=G[61]
+        const int T_GINT = 3;
+        var ins = new Instruction(0, 0x208, new[]
+        {
+            new Operand(T_GINT, 50), new Operand(T_GINT, 60), new Operand(T_GINT, 61),
+        });
+        var script = new Script
+        {
+            Header = new ScriptHeader(0, 0, 0, 0, 0, 0),
+            Instructions = new[] { ins },
+            IndexByOffset = new Dictionary<int, int> { { 0, 0 } },
+            Strings = new Dictionary<int, string>(),
+        };
+        var vm = new VirtualMachine(script, table, new FakeSizeHost());
+        vm.Run();
+        Assert.Equal(0x140, vm.Globals[60]);
+        Assert.Equal(0xC8, vm.Globals[61]);
+    }
+}
diff --git a/engine/Age.Engine.Tests/TextureOpsTests.cs b/engine/Age.Engine.Tests/TextureOpsTests.cs
index b2dbb92..ed61920 100644
--- a/engine/Age.Engine.Tests/TextureOpsTests.cs
+++ b/engine/Age.Engine.Tests/TextureOpsTests.cs
@@ -13,6 +13,7 @@ public class TextureOpsTests
         public int Creates;
         public void ShowText(int o, string t) { }
         public void WaitForInput() { }
+        public void Sleep(long duration) { }
         public void CreateTexture(int slot, int w, int h) => Creates++;
         public void SetTexture(long resId, int slot) => Sets.Add((resId, slot));
         public void DrawTexture(int slot, int srcX, int srcY, int w, int h, int dstX, int dstY) => Draws.Add((slot, w, h));
diff --git a/engine/Age.Engine.Tests/TextureOpsTests.cs.bak b/engine/Age.Engine.Tests/TextureOpsTests.cs.bak
new file mode 100644
index 0000000..b2dbb92
--- /dev/null
+++ b/engine/Age.Engine.Tests/TextureOpsTests.cs.bak
@@ -0,0 +1,36 @@
+using System.Collections.Generic;
+using Age.Engine.Hosting;
+using Age.Engine.Sys4;
+using Age.Engine.Vm;
+using Xunit;
+
+public class TextureOpsTests
+{
+    private sealed class RecHost : IHost
+    {
+        public List<(long resId, int slot)> Sets = new();
+        public List<(int slot, int w, int h)> Draws = new();
+        public int Creates;
+        public void ShowText(int o, string t) { }
+        public void WaitForInput() { }
+        public void CreateTexture(int slot, int w, int h) => Creates++;
+        public void SetTexture(long resId, int slot) => Sets.Add((resId, slot));
+        public void DrawTexture(int slot, int srcX, int srcY, int w, int h, int dstX, int dstY) => Draws.Add((slot, w, h));
+        public (int Width, int Height) GetTextureSize(int slot) => (0, 0);
+        public void PlayBgm(long id) { }
+        public void PlayVoice(long id) { }
+    }
+
+    [Fact]
+    public void SC0000FiresTextureOpsWithSlot0FullScreenSlideshow()
+    {
+        var table = OpcodeTableJson.Load(Paths.OpcodesJson);
+        var script = Sys4Loader.Load(Paths.Scripts()["SC0000.BIN"], table);
+        var host = new RecHost();
+        new VirtualMachine(script, table, host).Run();
+        Assert.True(host.Creates > 0, "create-texture should fire");
+        // The intro loads a sequence of full-screen images into slot 0; res 0x23 is the first bg.
+        Assert.Contains(host.Sets, s => s.resId == 0x23 && s.slot == 0);
+        Assert.Contains(host.Draws, d => d.slot == 0 && d.w == 0x320 && d.h == 0x258);
+    }
+}
diff --git a/engine/Age.Engine/Hosting/CaptureHost.cs b/engine/Age.Engine/Hosting/CaptureHost.cs
index e7195cd..42a5c48 100644
--- a/engine/Age.Engine/Hosting/CaptureHost.cs
+++ b/engine/Age.Engine/Hosting/CaptureHost.cs
@@ -4,6 +4,7 @@ public sealed class CaptureHost : IHost
     public List<(int Offset, string Text)> Emitted { get; } = new();
     public void ShowText(int offset, string text) => Emitted.Add((offset, text));
     public void WaitForInput() { }
+    public void Sleep(long duration) { }
     public void CreateTexture(int slot, int width, int height) { }
     public void SetTexture(long resourceId, int slot) { }
     public void DrawTexture(int slot, int srcX, int srcY, int width, int height, int dstX, int dstY) { }
diff --git a/engine/Age.Engine/Hosting/IHost.cs b/engine/Age.Engine/Hosting/IHost.cs
index ccc04f5..55022b1 100644
--- a/engine/Age.Engine/Hosting/IHost.cs
+++ b/engine/Age.Engine/Hosting/IHost.cs
@@ -3,6 +3,7 @@ public interface IHost
 {
     void ShowText(int offset, string text);
     void WaitForInput();
+    void Sleep(long duration);
     void CreateTexture(int slot, int width, int height);
     void SetTexture(long resourceId, int slot);
     void DrawTexture(int slot, int srcX, int srcY, int width, int height, int dstX, int dstY);
diff --git a/engine/Age.Engine/Vm/VirtualMachine.cs b/engine/Age.Engine/Vm/VirtualMachine.cs
index 5d761c4..e0aa0d9 100644
--- a/engine/Age.Engine/Vm/VirtualMachine.cs
+++ b/engine/Age.Engine/Vm/VirtualMachine.cs
@@ -208,6 +208,8 @@ public sealed class VirtualMachine
                 }
                 return pc + 1;
             case "wait-for-input": _host.WaitForInput(); return pc + 1;
+            case "sleep":   // 0xc8 (duration) — pause the host duration ms; headless hosts no-op (parity). Frame pacing.
+                _host.Sleep(Read(a[0])); return pc + 1;
             case "end-text-line": case "set-font":
             case "comment": case "display-furigana": case "dev_ukn":
                 return pc + 1;