Summary

• prevent macOS app crash when Voice Wake starts without a usable default audio input device
• add CoreAudio preflight for default input availability before installing AVAudioEngine tap
• keep failure in the recoverable runtime path (log + stop), avoiding SIGABRT process termination

Bug

On Macs with no usable input device (common on Mac mini/headless setups), enabling Voice Wake can crash:

• AVAudioNode.installTapOnBus throws Objective-C exception
• exception crosses into Swift runtime and aborts the app (SIGABRT)

Root Cause

VoiceWakeRuntime.start(with:) proceeded to installTap without verifying that the default input device is both present and input-capable/alive.

Changes

1. AudioInputDeviceObserver

• added hasUsableDefaultInputDevice()
• added inputAvailabilitySummary() for diagnostics
• added private helper for default UID vs alive input UID matching

2. VoiceWakeRuntime.start(with:)

• added startup guard using AudioInputDeviceObserver.hasUsableDefaultInputDevice() before installing tap
• throws normal NSError (with input summary) and exits via existing catch/stop flow

3. Tests

• added AudioInputDeviceObserverTests covering:
  • missing default UID
  • default UID not alive/input-capable
  • default UID valid/alive

Validation

• swift test --filter AudioInputDeviceObserverTests
• swift test --filter VoiceWakeRuntimeTests

Fixes

• Fixes macOS app crashes when opening VoiceWake tab (2026.2.14) #17484
• Fixes [Bug]: macOS app crashes (SIGABRT) when enabling Microphone / Voice Wake on Mac mini (no input mic) — AVAudioNode installTapOnBus throws #16418
• Fixes macOS App crashes on launch when no audio input device is available (VoiceWakeRuntime) #16118
• Fixes macOS app crashes on launch when no audio input device connected (VoiceWakeRuntime) #15740
• Fixes Mac app: SIGABRT crash when no audio input device available (voice wake) #12169

Greptile Summary

Prevents a crash (SIGABRT) on Macs without a usable audio input device (e.g., Mac mini/headless setups) by adding a CoreAudio preflight check before installing the AVAudioEngine tap in VoiceWakeRuntime.start(with:). The new AudioInputDeviceObserver.hasUsableDefaultInputDevice() method verifies the default input device UID is both present and alive before proceeding, converting what was a fatal ObjC exception into a recoverable error handled through the existing catch/stop flow.

• AudioInputDeviceObserver gains hasUsableDefaultInputDevice() and inputAvailabilitySummary() with a clean private helper that matches the default device UID against alive input UIDs
• VoiceWakeRuntime.start(with:) now guards on input device availability before engine creation, throwing a descriptive NSError that the existing catch block handles gracefully
• New AudioInputDeviceObserverTests cover nil UID, mismatched UID, and valid UID cases via a #if DEBUG test hook
• Note: VoiceWakeTester and MicLevelMonitor have similar installTap patterns without this preflight guard — they may benefit from the same protection in a follow-up, though they are less critical since they are user-initiated rather than automatic

Confidence Score: 5/5

• This PR is safe to merge — it adds a defensive guard that prevents a crash on the error path without changing any happy-path behavior.
• The change is small, well-scoped, and only adds a guard before existing code. The new check is purely additive — when a usable input device exists, behavior is identical to before. When no device exists, the code now takes a graceful error path instead of crashing. The logic is simple (UID lookup + set membership) and tested. No existing tests or behavior are affected.
• No files require special attention. Consider applying the same hasUsableDefaultInputDevice() guard to VoiceWakeTester.swift and MicLevelMonitor.swift in a follow-up.

_{Last reviewed commit: 680ec7d}

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