---
summary: "macOS IPC architecture for SKYKOI app, gateway node transport, and PeekabooBridge"
read_when:
  - Editing IPC contracts or menu bar app IPC
title: "macOS IPC"
---

# SKYKOI macOS IPC architecture

**Current model:** a local Unix socket connects the **node host service** to the **macOS app** for exec approvals + `system.run`. A `SKYKOI-mac` debug CLI exists for discovery/connect checks; koi actions still flow through the Gateway WebSocket and `node.invoke`. UI automation uses PeekabooBridge.

## Goals

- Single GUI app instance that owns all TCC-facing work (notifications, screen recording, mic, speech, AppleScript).
- A small surface for automation: Gateway + node commands, plus PeekabooBridge for UI automation.
- Predictable permissions: always the same signed bundle ID, launched by launchd, so TCC grants stick.

## How it works

### Gateway + node transport

- The app runs the Gateway (local mode) and connects to it as a node.
- Koi actions are performed via `node.invoke` (e.g. `system.run`, `system.notify`, `canvas.*`).

### Node service + app IPC

- A headless node host service connects to the Gateway WebSocket.
- `system.run` requests are forwarded to the macOS app over a local Unix socket.
- The app performs the exec in UI context, prompts if needed, and returns output.

Diagram (SCI):

```
Koi -> Gateway -> Node Service (WS)
                      |  IPC (UDS + token + HMAC + TTL)
                      v
                  Mac App (UI + TCC + system.run)
```

### PeekabooBridge (UI automation)

- UI automation uses a separate UNIX socket named `bridge.sock` and the PeekabooBridge JSON protocol.
- Host preference order (client-side): Peekaboo.app → Claude.app → SKYKOI.app → local execution.
- Security: bridge hosts require an allowed TeamID; DEBUG-only same-UID escape hatch is guarded by `PEEKABOO_ALLOW_UNSIGNED_SOCKET_CLIENTS=1` (Peekaboo convention).
- See: [PeekabooBridge usage](/platforms/mac/peekaboo) for details.

## Operational flows

- Restart/rebuild: `SIGN_IDENTITY="Apple Development: <Developer Name> (<TEAMID>)" scripts/restart-mac.sh`
  - Kills existing instances
  - Swift build + package
  - Writes/bootstraps/kickstarts the LaunchAgent
- Single instance: app exits early if another instance with the same bundle ID is running.

## Hardening notes

- Prefer requiring a TeamID match for all privileged surfaces.
- PeekabooBridge: `PEEKABOO_ALLOW_UNSIGNED_SOCKET_CLIENTS=1` (DEBUG-only) may allow same-UID callers for local development.
- All communication remains local-only; no network sockets are exposed.
- TCC prompts originate only from the GUI app bundle; keep the signed bundle ID stable across rebuilds.
- IPC hardening: socket mode `0600`, token, peer-UID checks, HMAC challenge/response, short TTL.
