meeting-assistant/openspec/changes/add-macos-meeting-audio-capture/proposal.md

Why

The portable Meeting Assistant build runs on macOS, but starting a recording resolves UnavailableMeetingAudioSource and fails before any audio reaches transcription. macOS users need the same microphone-plus-computer-output capture contract without changing the established Windows NAudio implementation.

What Changes

• Add native macOS microphone capture through AVFoundation.
• Add native macOS computer-output capture through ScreenCaptureKit.
• Stream both sources as 16-bit PCM into the existing alignment, echo-cancellation, gain, mixing, recording, and transcription pipeline.
• Select the macOS sources only when the portable build is running on macOS; retain the existing compile-time Windows registrations unchanged.
• Package a small Swift capture helper in macOS build and publish output.
• Produce a short mixed WAV from live microphone and system PCM emitted by the implemented native capture helper as operational evidence.
• Verify the public recording endpoints, managed macOS adapters, mixer, and stop behavior together with deterministic process-boundary audio.

Capabilities

New Capabilities

None.

Modified Capabilities

• meeting-recording: Extend microphone and computer-output recording to macOS while preserving Windows behavior.

Impact

• Portable application dependency registration.
• A macOS-native helper executable built from Swift source.
• macOS Screen Recording/System Audio and Microphone privacy permissions.
• Recording behavior tests, build verification, and runtime documentation.