Apus integrates external CLIs via JSON-RPC. Two patterns are used today.

Pattern A: HTTP daemon (signal-cli)

• signal-cli runs as a daemon with JSON-RPC over HTTP.
• Event stream is SSE (/api/v1/events).
• Health check: /api/v1/check.
• Apus owns lifecycle when channels.signal.transport.kind="managed-native" (the default).

See Signal for setup and endpoints.

Pattern B: stdio child process (imsg)

• Apus spawns imsg rpc as a child process for iMessage.
• JSON-RPC is line-delimited over stdin/stdout (one JSON object per line).
• No TCP port, no daemon required.

Core methods used:

• watch.subscribe → notifications (method: "message")
• watch.unsubscribe
• send
• chats.list (check/diagnostics)

See iMessage for setup and addressing (chat_id preferred over display strings).

Adapter guidelines

• Gateway owns the process (start/stop tied to provider lifecycle).
• Keep RPC clients resilient: timeouts, restart on exit.
• Prefer stable IDs (e.g., chat_id) over display strings.

Related

• Gateway protocol