Calendar Bridge

CalendarBridge is a Model Context Protocol (MCP) connector that lets ChatGPT work with your Apple Calendar. It never uploads your events to a third party — 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.

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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 account
npx 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 activity
npx calendar-agent uninstall   # stop auto-start

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What ChatGPT can do

Tool	Action
list_calendars	List all your calendars (Work, Personal, Family, …)
list_events	List upcoming events in a date window (default next 7 days), optionally one calendar
search_events	Find events whose title contains a keyword
get_event	Read one event by id
create_event	Create an event (title, start, end, optional location, notes, calendar, all-day)
update_event	Edit an event's fields (overwrites the fields you pass — read it first)

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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.

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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 storage
test/      end-to-end OAuth + MCP integration test

Development

# server
cd 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 tests
node --test agent/test-agent-unit.mjs

Security & privacy

• Events are read/written only on your Mac. The relay never persists event content — 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