Transcription fails on macOS 26 (Tahoe) — AVAudioFile / FigAssetWriter errors

[karanb192]

Environment

• macOS: 26.2 (Tahoe), Build 25C56
• Chip: Apple Silicon (arm64)
• SpeakType: v1.0.21
• Model: Whisper Large v3 Turbo
• Mic: MacBook Pro Built-in Microphone (48kHz) — also tested with AirPods Pro 3 (Bluetooth, 24kHz)

Issue

Transcription fails every time with a generic "transcription failed" error in the UI. The app records audio (mic activates, capture session starts/stops) but the audio file is never written successfully.

Logs (from log show)

speaktype: (MediaToolbox) <<<< FigAssetWriter >>>> signalled err=-12142 at <>:2497
speaktype: (AVFCore) <<<< AVError >>>> AVLocalizedErrorWithUnderlyingOSStatus: Returning error (AVFoundationErrorDomain / -11800) status (-12142)
speaktype: (AVFAudio) AVAEInternal.h:104 [AVAudioFile.mm:287:AVAudioFileImpl: (ExtAudioFileOpenURL((__bridge CFURLRef)fileURL, &_extAudioFile)): error 2003334207

Analysis

• Error -12142 = FigAssetWriter fails to finalize the audio file
• Error 2003334207 ('typ?') = unsupported audio file type when trying to read the recorded file back
• Likely caused by AVFoundation audio format/codec changes in macOS 26 (Tahoe)

Steps to Reproduce

1. Install SpeakType v1.0.21 on macOS 26.2
2. Download any Whisper model
3. Hold hotkey, speak, release
4. → "Transcription failed"