iMessage Voice Reply

Generate and send native iMessage voice messages using local Kokoro TTS. Voice messages appear as inline playable bubbles with waveforms — identical to voice messages recorded in Messages.app.

How It Works

Your text response → Kokoro TTS (local) → afconvert (native Apple encoder) → CAF/Opus → BlueBubbles → iMessage voice bubble

Setup

bash ${baseDir}/scripts/setup.sh

Installs: kokoro-onnx, soundfile, numpy. Downloads Kokoro models (~136MB) to ~/.cache/kokoro-onnx/.

Requires: BlueBubbles channel configured in OpenClaw (channels.bluebubbles).

Generating and Sending a Voice Reply

Step 1: Generate audio

Write the response text to a temp file, then pass it via --text-file to avoid shell injection:

echo "Your response text here" > /tmp/voice_text.txt
${baseDir}/.venv/bin/python ${baseDir}/scripts/generate_voice_reply.py --text-file /tmp/voice_text.txt --output /tmp/voice_reply.caf

Alternatively, pass text directly (ensure proper shell escaping):

${baseDir}/.venv/bin/python ${baseDir}/scripts/generate_voice_reply.py --text "Your response text here" --output /tmp/voice_reply.caf

Options:

• --voice af_heart — Kokoro voice (default: af_heart)
• --speed 1.15 — Playback speed (default: 1.15)
• --lang en-us — Language code (default: en-us)

Security note: The Python script uses argparse and subprocess.run with list arguments (no shell=True). Input is handled safely within the script. When calling from a shell, prefer --text-file for untrusted input to avoid shell metacharacter issues.

Step 2: Send via BlueBubbles

Use the message tool:

{
  "action": "sendAttachment",
  "channel": "bluebubbles",
  "target": "+1XXXXXXXXXX",
  "path": "/tmp/voice_reply.caf",
  "filename": "Audio Message.caf",
  "contentType": "audio/x-caf",
  "asVoice": true
}

Critical parameters for native voice bubble:

• filename must be "Audio Message.caf"
• contentType must be "audio/x-caf"
• asVoice must be true

All three are required for iMessage to render the message as an inline voice bubble with waveform instead of a file attachment.

Voice Options

When to Reply with Voice

Reply with a voice message when:

• The user sent you a voice message (voice-for-voice)
• The user explicitly asks for an audio/voice response

Always include a text reply alongside the voice message for accessibility.

Audio Format

• macOS: CAF container, Opus codec, 48kHz mono, 32kbps — encoded by Apple's native afconvert. Identical to what Messages.app produces.
• Fallback: MP3 via ffmpeg (works but may not render as native voice bubble on all iMessage versions).

Cost

$0. Kokoro TTS runs entirely locally. No API calls for voice generation.

Troubleshooting

Voice message shows as file attachment — Ensure all three parameters are set: filename="Audio Message.caf", contentType="audio/x-caf", asVoice=true.

First word clipped — The script prepends 150ms silence automatically. If still clipped, increase the silence pad in the script.

Kokoro model not found — Run bash ${baseDir}/scripts/setup.sh.

afconvert not found — Only available on macOS. Script falls back to ffmpeg/MP3 on Linux.