Calendar Bridge

CalendarBridge is a Model Context Protocol (MCP) connector that lets ChatGPT work with your Apple Calendar. Reads execute locally and requested results pass through the authenticated relay — every action runs on your own Mac through a tiny local agent. The cloud piece is only a stateless relay that shuttles requests between ChatGPT and your Mac.

  ChatGPT  ──OAuth──►  CalendarBridge relay  ──job queue──►  calendar-agent  ──►  Calendar.app (connector)          (Vercel, stateless)      (your Mac, polls & executes)     (on your Mac)

Your Mac is the only place your events are ever read or written. The relay stores only short-lived job payloads and your account record; it never sees an event unless a job is in flight, and jobs expire in seconds.

For users — 3 steps

1. Create your account at calendarbridge.vercel.app and generate a pairing code.

2. Install the Mac agent (needs Node 18+):

npx calendar-agent pair <YOUR-CODE>   # link this Mac to your accountnpx calendar-agent install            # keep it running on every restart

The first time it touches Calendar, macOS asks "Terminal wants to control Calendar" — click OK (one time).

3. Connect ChatGPT: Settings → Plugins → turn on Developer mode (Security & login) → Create a custom plugin → paste the MCP Server URL https://calendarbridge.vercel.app/mcp → Authentication OAuth → sign in & Allow.

That's it. In a new chat: "Search my Apple Calendar for the dentist appointment" or "Add a Team Standup to my Work calendar tomorrow at 9am."

Your Mac must be awake with the agent running. npx calendar-agent install makes it start automatically at login and restart if it ever crashes.

Managing the agent

npx calendar-agent status      # is it paired & reachable?npx calendar-agent logs        # recent activitynpx calendar-agent uninstall   # stop auto-start

What ChatGPT can do

Self-hosting

You can run your own relay so nothing depends on the hosted instance.

Prereqs: a Vercel account and a Supabase project (free tiers are fine).

1. Storage — in your Supabase project's SQL editor, run supabase/schema.sql. It creates a tiny Redis-shaped KV + queue surface (nb_* functions) with RLS on.
2. Deploy the server/ directory to Vercel.
3. Set env vars (see server/.env.example):
   • SUPABASE_URL, SUPABASE_SERVICE_ROLE_KEY — your project + service-role key
   • JWT_SECRET — openssl rand -hex 32
4. Verify: curl https://YOUR-APP.vercel.app/api/health → redisConfigured, redisOk, jwtSecretSet all true.
5. Point the agent at it: npx calendar-agent pair <CODE> --server https://YOUR-APP.vercel.app.

How it works

• Auth — OAuth 2.1 with PKCE and Dynamic Client Registration (RFC 7591). ChatGPT registers itself, the user signs in on the CalendarBridge consent page, and ChatGPT gets a scoped MCP access token. JWTs are HMAC-signed; three kinds (session, agent, mcp) with distinct privileges. Optional email verification via Resend (RESEND_API_KEY); off unless configured, and enforcement is opt-in (REQUIRE_EMAIL_VERIFICATION).
• Relay — MCP tool call → job pushed to jobs:<user> (TTL ≤ the caller's wait window, so an abandoned job can't run late) → the Mac agent (holding a hanging long-poll) is handed the job within ~200ms, executes it, pushes the result → the MCP handler returns it. The long-poll means jobs are delivered on arrival rather than on a fixed interval, so relay overhead is ~300ms instead of ~1s. The agent is considered "online" only while it's actively connected.
• Agent — a dependency-free Node CLI. Tools run via JXA (osascript -l JavaScript) against Calendar.app; arguments are passed as JSON over argv (never shell-interpolated). A macOS LaunchAgent keeps it alive across logins and crashes.

Repository layout

server/    Vercel functions: OAuth + MCP endpoint + relay        (deploy this)agent/     calendar-agent — the npm-published Mac CLI                 (users npx this)kit/       Browser automations: register the dev-mode connector AND           fill the OpenAI directory submission (see kit/README.md)supabase/  schema.sql for self-hosting the storagetest/      end-to-end OAuth + MCP integration test

Development

# servercd server && cp .env.example .env.local   # fill in, then: vercel dev# end-to-end test against a live deployment (reads ../.env.local)node test/e2e-oauth.mjs# agent unit testsnode --test agent/test-agent-unit.mjs

Security & privacy

• Events are read/written only on your Mac. The relay temporarily stores requested content in short-lived job/result queues — job payloads live in Redis-shaped storage with a short TTL and are deleted on delivery.
• The agent token is stored at ~/.calendarbridge-agent.json (mode 600).
• No secrets are committed; see .gitignore and the .env.example files.
• Write tools are marked destructive so ChatGPT asks before changing an event.

License

MIT © Isaiah Dupree

Production storage and owner verification

Relay 1.4 uses isolated service-role-only tables/functions on the configured shared Supabase project. Production refuses missing storage configuration, bounds RPC requests to ten seconds, and returns HTTP 503 when storage or signing configuration is unavailable. Apply the checked-in isolated-storage migration before deploying this version; it does not replace another bridge's account tables or functions.

node --env-file=.env.local test/live-storage.mjs verifies the actual persistent store, FIFO, expiry and counters using temporary integration keys. BRIDGE_SESSION_FILE=/private/owner-session.json BRIDGE_READ_TOOL=READ_TOOL node test/live-relay.mjs verifies the actual owner session, PKCE OAuth, hosted MCP and paired-Mac read; choose this bridge's inventory tool. No reviewer data counts as a live acceptance. Credentials and sessions belong outside Git.