Architecture

Sentinel is a monorepo with two shipping pieces — a Tauri desktop app and a Node.js daemon — plus shared types and a marketing site.

Claude Code  ──→  localhost:47284  ──→  api.anthropic.com
                  (sentinel daemon)
                        │
                        │  Unix socket / named pipe
                        ▼
                  Sentinel App
                  (Tauri v2 tray app)

The app (packages/app)

A Tauri v2 desktop tray application with a React frontend and a Rust backend.

• Bundles and supervises the daemon as a sidecar process. It spawns the daemon once on startup and does not auto-restart it — so the daemon’s lifetime is tied to the app session.
• Patches ~/.claude/settings.json on activation so Claude Code routes through the proxy (ANTHROPIC_BASE_URL), and unpatches it on uninstall.
• Hosts the UI: Accounts, Security, Alerts, Usage, Optimize, Metrics, and Logs tabs, plus the Settings panel.

The Rust side (src-tauri/src/) handles the system tray, the IPC bridge to the daemon, the sidecar spawn logic, window events, and the activate/deactivate settings patch.

The daemon (packages/daemon)

A Node.js process compiled into a single self-contained binary (via @yao-pkg/pkg) and embedded inside the app bundle. It is:

• an HTTP reverse proxy that forwards Claude Code’s requests to Anthropic, selecting the active account’s token per request and inspecting overage headers on responses;
• an OTLP telemetry receiver that aggregates the metrics powering the Metrics tab;
• an MCP server (used by the optimization features, e.g. mcp__sentinel__retrieve);
• a SQLite store for accounts, rate limits, alerts, notifications, permission rules, security events, and request logs.

How the two communicate

The app and daemon talk over a Unix domain socket (named pipe on Windows) created with owner-only permissions. Messages are typed (packages/shared):

• App → Daemon: account operations, settings reads/writes, alert CRUD, sync triggers, and admin commands.
• Daemon → App (broadcasts): account switches, rate-limit/usage updates, overage transitions, alert triggers, security events, sync status, and settings changes — which the UI turns into live updates and native notifications.

Request lifecycle

1. Claude Code sends a request to localhost:47284.
2. The proxy selects the active account’s token (or, in Auto mode, the rotator picks one) and forwards it to api.anthropic.com.
3. Detectors scan the request and response in flight; findings are persisted (redacted) and may block or hold the action.
4. The response’s rate-limit and overage headers update the SQLite store and trigger broadcasts.
5. The response is forwarded back to Claude Code unmodified — the proxy is transparent.

See Project structure for the file-level map.