Wrap ObjC auto-async calls in explicit checked continuations

.changes/objc-async-checked-continuation

@@ -0,0 +1 @@
+patch type="fixed" "Wrap ObjC completion-handler async calls in explicit checked continuations (fixes mixed Swift 5/6 continuation-bridge EXC_BAD_ACCESS)"

AGENTS.md

@@ -130,6 +130,7 @@ private static let playAndRecordOptions: AVAudioSession.CategoryOptions = [.mixW
 - Only `Task.discarding` preserves caller actor isolation in its closure; other `Support/Async/` helpers (`Task.retrying`, `AsyncSerialDelegate.notifyAsync`, etc.) run their bodies nonisolated — hop explicitly with `await MainActor.run { ... }` when UI-bound work is needed
 - Use async primitives in `Support/Async` and `Support/Schedulers` when operation order matters
 - Prefer native Swift async/await over `Combine` for new code
+- Until the minimum supported compiler is Swift 6.3, wrap calls to imported Objective-C completion-handler methods made via their synthesized `async` overload in an explicit `withCheckedThrowingContinuation`, since the bare auto-bridge hits a mixed Swift 5/6 thunk-coalescing crash (swiftlang/swift#81846) fixed in 6.3
 
 ### Error Handling
 

Sources/LiveKit/Core/Transport.swift

@@ -68,7 +68,12 @@ actor Transport: NSObject, Loggable {
         guard let self else { return }
 
         do {
-            try await _pc.add(iceCandidate.toRTCType())
+            let rtcCandidate = iceCandidate.toRTCType()
+            try await withCheckedThrowingContinuation { (continuation: CheckedContinuation<Void, Error>) in
+                self._pc.add(rtcCandidate) { error in
+                    if let error { continuation.resume(throwing: error) } else { continuation.resume() }
+                }
+            }
         } catch {
             log("Failed to add(iceCandidate:) with error: \(error)", .error)
         }

Sources/LiveKit/Track/Capturers/CameraCapturer.swift

@@ -285,7 +285,11 @@ public class CameraCapturer: VideoCapturer, @unchecked Sendable {
 
         log("starting camera capturer device: \(device), format: \(selectedFormat), fps: \(selectedFps)(\(fpsRange))", .info)
 
-        try await capturer.startCapture(with: device, format: selectedFormat.format, fps: selectedFps)
+        try await withCheckedThrowingContinuation { (continuation: CheckedContinuation<Void, Error>) in
+            capturer.startCapture(with: device, format: selectedFormat.format, fps: selectedFps) { error in
+                if let error { continuation.resume(throwing: error) } else { continuation.resume() }
+            }
+        }
 
         // Update internal vars
         _cameraCapturerState.mutate {
@@ -305,7 +309,11 @@ public class CameraCapturer: VideoCapturer, @unchecked Sendable {
         // Already stopped
         guard didStop else { return false }
 
-        await capturer.stopCapture()
+        await withCheckedContinuation { (continuation: CheckedContinuation<Void, Never>) in
+            capturer.stopCapture {
+                continuation.resume()
+            }
+        }
 
         // Update internal vars
         set(dimensions: nil)

Sources/LiveKit/Track/Capturers/InAppCapturer.swift

@@ -39,11 +39,15 @@ public class InAppScreenCapturer: VideoCapturer, @unchecked Sendable {
         guard didStart else { return false }
 
         // TODO: force pixel format kCVPixelFormatType_420YpCbCr8BiPlanarFullRange
-        try await RPScreenRecorder.shared().startCapture { [weak self] sampleBuffer, type, _ in
-            guard let self else { return }
-            // Only process .video
-            if type == .video {
-                capture(sampleBuffer: sampleBuffer, capturer: capturer, options: options)
+        try await withCheckedThrowingContinuation { (continuation: CheckedContinuation<Void, Error>) in
+            RPScreenRecorder.shared().startCapture { [weak self] sampleBuffer, type, _ in
+                guard let self else { return }
+                // Only process .video
+                if type == .video {
+                    capture(sampleBuffer: sampleBuffer, capturer: capturer, options: options)
+                }
+            } completionHandler: { error in
+                if let error { continuation.resume(throwing: error) } else { continuation.resume() }
             }
         }