Preserve iOS screen audio during stream startup

PROGRESS.md

@@ -49,8 +49,11 @@ An explicit disconnect now pauses the prepared iOS graph and releases the audio
 next connection resumes that graph before attempting a rebuild. A signed iOS 26 simulator gate
 verified guest-to-account editing, saved-password login after a process restart, two voice joins,
 and a screen-audio stream started before the microphone. Screen sharing no longer forces a graph
-rebuild, and its pump subscribes before announcing the stream. An idle shared broadcast ring is
-no longer held mapped through suspension. A TestFlight report from build 2026092504 was an iOS
+rebuild, and its pump subscribes before announcing the stream. The pump retains up to 120 ms of
+screen PCM captured during stream negotiation; the simulator gate now checks that this PCM
+reaches the encoder and passed on iOS 26. Audible screen sharing was confirmed on an iPhone 16
+Pro Max after deployment. An idle shared broadcast ring is no longer held mapped through suspension. A
+TestFlight report from build 2026092504 was an iOS
 `0xdead10cc` shared-file-lock termination; physical-device validation of that mitigation remains
 open.
 

clients/apple/README.md

@@ -24,7 +24,10 @@ require `VOICECAT_CODESIGN_IDENTITY`; optional notarization uses `APPLE_ID`, `AP
 For a physical iOS device, use `build-ios-device.sh` and `deploy-ios-device.sh`. The host and
 ReplayKit extension require signing profiles with App Group `group.me.iamtalon.voicecat`.
 Hardware validation must cover VoiceOver, background and lock behavior, interruptions, route
-changes, Bluetooth, ReplayKit, and iOS 27 ScreenCaptureKit audio.
+changes, Bluetooth, ReplayKit, and iOS 27 ScreenCaptureKit audio. The opt-in simulator share
+smoke gate checks that ring PCM captured during stream startup reaches the encoder; audible
+screen sharing was confirmed on an iPhone 16 Pro Max. The iOS 27 capture path still needs a
+device check.
 For iOS voice stability, leave a call joined with the microphone active for at least 30 minutes
 and confirm speech stays clear and `VC_AUDIO` reports no growing `feedDrops`. While still joined,
 toggle Wi-Fi off and on, switch between Wi-Fi and cellular, and confirm the app stays open,

clients/apple/VoiceCat.iOS/AppModel.cs

@@ -53,6 +53,7 @@ internal sealed class AppModel
     internal bool ScreenSharing => broadcast?.IsActive == true;
 #if DEBUG
     internal bool ScreenRingMapped => broadcast?.IsMappingOpen == true;
+    internal long ScreenEncodedPackets => broadcast?.EncodedPackets ?? 0;
 #endif
     internal bool IsBackgrounded => backgrounded;
     internal float MicrophoneLevel { get; private set; }

clients/apple/VoiceCat.iOS/BroadcastAudioPump.cs

@@ -26,6 +26,7 @@ internal sealed class BroadcastAudioPump : IAsyncDisposable
     internal bool IsActive => active;
 #if DEBUG
     internal bool IsMappingOpen => view is not null;
+    internal long EncodedPackets => streamId == 0 ? 0 : client?.Audio.GetLocalDiagnostics(streamId).EncodedPackets ?? 0;
 #endif
 
     internal void Start(VoiceCatClient owner)
@@ -82,7 +83,13 @@ internal sealed class BroadcastAudioPump : IAsyncDisposable
                 try { owner.StopStream(stream.StreamId); } catch (Exception exception) when (exception is IOException or InvalidOperationException) { }
                 return;
             }
-            streamId = stream.StreamId; pages.Write(32, pages.ReadUInt64(24)); SetActive(true);
+            // Keep the newest 120 ms captured during stream negotiation. This covers the
+            // largest codec frame plus the input buffer target; dropping through the latest
+            // write loses short sounds before the first drain can feed them.
+            ulong latestWrite = pages.ReadUInt64(24);
+            ulong earliest = latestWrite > (ulong)(Frame * 12) ? latestWrite - (ulong)(Frame * 12) : 0;
+            pages.Write(32, Math.Max(pages.ReadUInt64(32), earliest));
+            streamId = stream.StreamId; SetActive(true);
         }
         ulong write = pages.ReadUInt64(24), read = pages.ReadUInt64(32);
         if (write - read > Capacity) read = write - Capacity;

clients/apple/VoiceCat.iOS/SimulatorSmoke.cs

@@ -46,10 +46,20 @@ internal static class SimulatorSmoke
                     await Task.Delay(300);
                     Require(!model.ScreenRingMapped && !model.ScreenSharing,
                         "An unchanged ring from a previous broadcast remained mapped.");
-                    WriteRing(ring, active: true, write: 3840);
+                    for (int frame = 0; frame < 6; frame++) WriteScreenPcm(ring);
                     await WaitUntil(() => model.ScreenSharing, "Screen stream did not start.");
                     Require(IosAudioEngine.Shared.IsRunning, "Screen sharing stopped the audio graph.");
-                    WriteRing(ring, active: false, write: 3840);
+                    await WaitUntil(() => model.ScreenEncodedPackets > 0,
+                        "Screen PCM captured before stream negotiation was discarded.");
+                    long encodedBefore = model.ScreenEncodedPackets;
+                    for (int frame = 0; frame < 12; frame++)
+                    {
+                        WriteScreenPcm(ring);
+                        await Task.Delay(20);
+                    }
+                    await WaitUntil(() => model.ScreenEncodedPackets > encodedBefore,
+                        "Screen PCM did not reach the encoder while the microphone was off.");
+                    WriteRing(ring, active: false);
                     await WaitUntil(() => !model.ScreenSharing, "Screen stream did not stop.");
                     Require(!model.ScreenRingMapped, "The stopped screen ring remained mapped.");
                     Console.Error.WriteLine("VC_SIM phase=screenSharePassed");
@@ -65,9 +75,9 @@ internal static class SimulatorSmoke
                     "Screen sharing recovery stopped the live audio graph.");
                 if (ring is not null)
                 {
-                    WriteRing(ring, active: true, write: 3840);
+                    WriteRing(ring, active: true);
                     await Task.Delay(300);
-                    WriteRing(ring, active: true, write: 5760);
+                    WriteScreenPcm(ring);
                     await WaitUntil(() => model.ScreenSharing, "Screen stream did not start during a voice call.");
                     Require(IosAudioEngine.Shared.IsRunning, "Starting screen sharing stopped the voice graph.");
                 }
@@ -75,7 +85,7 @@ internal static class SimulatorSmoke
                 if (ring is not null)
                 {
                     Require(model.ScreenSharing, "Leaving the microphone call unsubscribed active screen audio.");
-                    WriteRing(ring, active: false, write: 5760);
+                    WriteRing(ring, active: false);
                     await WaitUntil(() => !model.ScreenSharing, "The second screen stream did not stop.");
                 }
                 await model.DisconnectAsync();
@@ -123,16 +133,41 @@ internal static class SimulatorSmoke
         return path;
     }
 
-    private static void WriteRing(string path, bool active, ulong write)
+    private static void WriteRing(string path, bool active, ulong? write = null)
     {
         using var file = new FileStream(path, FileMode.Open, FileAccess.Write, FileShare.ReadWrite);
         byte[] value = new byte[8];
-        BinaryPrimitives.WriteUInt64LittleEndian(value, write);
-        file.Position = 24; file.Write(value);
+        if (write is { } position)
+        {
+            BinaryPrimitives.WriteUInt64LittleEndian(value, position);
+            file.Position = 24; file.Write(value);
+        }
         BinaryPrimitives.WriteUInt32LittleEndian(value, active ? 1u : 0u);
         file.Position = 16; file.Write(value, 0, 4);
     }
 
+    private static void WriteScreenPcm(string path)
+    {
+        using var file = new FileStream(path, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite);
+        Span<byte> index = stackalloc byte[8];
+        file.Position = 24; file.ReadExactly(index);
+        ulong write = BinaryPrimitives.ReadUInt64LittleEndian(index);
+        byte[] pcm = new byte[960 * 2 * sizeof(short)];
+        for (int sample = 0; sample < pcm.Length / sizeof(short); sample++)
+            BinaryPrimitives.WriteInt16LittleEndian(pcm.AsSpan(sample * sizeof(short)),
+                (short)(sample % 64 < 32 ? 6000 : -6000));
+        int start = (int)(write % 96_000), first = Math.Min(pcm.Length / sizeof(short), 96_000 - start);
+        file.Position = 64 + start * sizeof(short);
+        file.Write(pcm.AsSpan(0, first * sizeof(short)));
+        if (first < pcm.Length / sizeof(short))
+        {
+            file.Position = 64;
+            file.Write(pcm.AsSpan(first * sizeof(short)));
+        }
+        BinaryPrimitives.WriteUInt64LittleEndian(index, write + (ulong)(pcm.Length / sizeof(short)));
+        file.Position = 24; file.Write(index);
+    }
+
     private static async Task WaitUntil(Func<bool> condition, string error)
     {
         for (int attempt = 0; attempt < 30; attempt++)

docs/ios-deploy.md

@@ -158,9 +158,10 @@ Grant microphone access with `xcrun simctl privacy booted grant microphone
 me.iamtalon.voicecat`. Launch with `SIMCTL_CHILD_VOICECAT_SIM_SMOKE` set to
 `127.0.0.1:<port>:<smoke-account-password>` and
 `SIMCTL_CHILD_VOICECAT_SIM_SMOKE_MODE=share` using `xcrun simctl launch --console-pty booted
-me.iamtalon.voicecat`. The `share` mode checks that a stale ring stays unmapped, then exercises
-synthetic screen audio with the microphone off and during a voice call, voice join, disconnect,
-and reconnect. Look for
+me.iamtalon.voicecat`. The `share` mode checks that a stale ring stays unmapped, then verifies
+that screen PCM captured before stream negotiation reaches the encoder. It also exercises
+continuous synthetic screen audio with the microphone off and during a voice call, voice join,
+disconnect, and reconnect. Look for
 `VC_SIM phase=screenSharePassed` and `VC_SIM phase=passed`. Terminate the app, then launch
 again with mode `resume` to verify the saved account after a process restart. The simulator
 gate also accepts mode `stereo` to select the StereoMicrophone preset before login and voice join;