📅 CalendarBridge
Your Apple Calendar, in ChatGPT — on your own Mac.
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.
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>
npx calendar-agent install
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
npx calendar-agent logs
npx calendar-agent uninstall
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) |
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).
- 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.
- Deploy the
server/ directory to Vercel.
- Set env vars (see
server/.env.example):
SUPABASE_URL, SUPABASE_SERVICE_ROLE_KEY — your project + service-role keyJWT_SECRET — openssl rand -hex 32
- Verify:
curl https://YOUR-APP.vercel.app/api/health → redisConfigured, redisOk, jwtSecretSet all true.
- 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 storage
test/ end-to-end OAuth + MCP integration test
Development
cd server && cp .env.example .env.local
node test/e2e-oauth.mjs
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