Jamie Pine
51c46cd89e
ClientIdMiddleware was running the SQLAlchemy SELECT/INSERT/UPDATE/COMMIT inline on the event loop after every /mcp/* and /speak request. SQLite serialises writes, so concurrent MCP traffic queued behind the stamp write — the response sat waiting on a side-effect that the client never needs in band, and SSE streams would stall briefly per request. The middleware now hands the stamp to asyncio.to_thread via a fire-and- forget create_task so the response returns immediately and the write runs on the default executor. A module-level set keeps strong refs to in-flight tasks (per asyncio docs) so the GC can't collect them mid- write. The fallback path runs the stamp inline if no loop is available (tests/oddball callers) rather than silently dropping it.
Voicebox MCP server
Local Model Context Protocol server — lets any MCP-aware agent (Claude Code, Cursor, Windsurf, VS Code MCP extensions, etc.) speak text in your cloned voices, transcribe audio, and browse captures.
The server runs inside the same uvicorn process as the rest of Voicebox
and is mounted at /mcp (Streamable HTTP transport).
Install into your agent
Preferred — direct HTTP:
{
"mcpServers": {
"voicebox": {
"url": "http://127.0.0.1:17493/mcp",
"headers": { "X-Voicebox-Client-Id": "claude-code" }
}
}
}
Fallback — stdio shim (when the client doesn't speak HTTP MCP). The
voicebox-mcp binary ships inside the Voicebox.app bundle:
{
"mcpServers": {
"voicebox": {
"command": "/Applications/Voicebox.app/Contents/MacOS/voicebox-mcp",
"env": { "VOICEBOX_CLIENT_ID": "claude-code" }
}
}
}
Claude Code one-liner:
claude mcp add voicebox \
--transport http \
--url http://127.0.0.1:17493/mcp \
--header "X-Voicebox-Client-Id: claude-code"
Tools
| Name | Purpose |
|---|---|
voicebox.speak |
Speak text in a voice profile. Returns a generation id you can poll. |
voicebox.transcribe |
Whisper transcription of a base64 blob or an absolute local path. |
voicebox.list_captures |
Recent captures (dictation / recording / file) with transcripts. |
voicebox.list_profiles |
Available voice profiles (cloned + preset). |
All tools resolve voice profiles in this precedence:
- Explicit
profilearg (name or id — case-insensitive) - Per-client binding keyed by
X-Voicebox-Client-Id capture_settings.default_playback_voice_id(global default)
Bindings are managed via GET|PUT /mcp/bindings or in the app under
Settings → MCP.
Debug with MCP Inspector
npx @modelcontextprotocol/inspector http://127.0.0.1:17493/mcp
Point it at the URL, hit "List tools," call voicebox.list_profiles
first to confirm wiring, then voicebox.speak for end-to-end.
Non-MCP REST surface
POST /speak is a thin wrapper on the same code path for callers that
don't speak MCP (shell scripts, ACP, A2A):
curl -X POST http://127.0.0.1:17493/speak \
-H 'Content-Type: application/json' \
-H 'X-Voicebox-Client-Id: claude-code' \
-d '{"text":"Build complete.","profile":"Morgan"}'
Code layout
backend/mcp_server/
├── __init__.py # re-export mount_into
├── server.py # build_mcp_server() + mount_into(app)
├── tools.py # @mcp.tool() implementations
├── context.py # ClientIdMiddleware + current_client_id ContextVar
├── resolve.py # profile resolution precedence
├── events.py # pub/sub queue for /events/speak pill SSE
└── README.md # you are here
backend/mcp_shim/ # stdio ↔ Streamable-HTTP proxy (see its README)
The package is mcp_server, not mcp, to avoid shadowing the
installed mcp PyPI package that FastMCP imports internally.