Corresync

Mail, calendars, and tasks. One local MCP server and CLI. Provider-neutral, local-first tooling for AI agents, scripts, and you.

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corr brings isolated mail, calendar, and task accounts into one terminal—and one local Model Context Protocol server. Gmail, Google Calendar, and Google Tasks are available through a Desktop OAuth client in a Google Cloud project you control. Corresync-managed Google OAuth remains dormant. The canonical task tools also include explicit Microsoft To Do, Todoist, TickTick, and CalDAV VTODO routes; remaining task-provider adapters stay unavailable until their contracts are implemented.

Search mail and build one agenda across accounts without collapsing their identity or provider provenance.
Use one stable, provenance-preserving task model as provider adapters become available.
Save private account-local mail searches and relative calendar windows, then run them live without creating a shadow mailbox or calendar cache.
Use the same typed operations from a human-friendly CLI, stable JSON, or an AI agent.
Keep sign-in in a visible browser, an explicit public-client OAuth flow, or an approved local credential store.
Review consequential effects before they happen. Unknown remote outcomes stop for reconciliation instead of being retried automatically.

What it feels like

$ corr mail search --all-accounts \
    --query 'subject:"Quarterly plan"' --limit 3
● work · microsoft-owa   Ana Ruiz   Plan review
· personal · jmap       Finance    Plan receipt

$ corr agenda list --all-accounts \
    --start 2026-07-29T00:00:00Z \
    --end 2026-07-30T00:00:00Z

Connect an agent to the same local core:

corr integrations detect
corr integrations plan codex claude-code
corr integrations setup codex claude-code
# Phase A also includes github-copilot, gemini-cli, qwen-code, qoder, kimi-code

Then ask naturally:

Check my inboxes, calendars, and task lists and summarize what needs attention today.

One failed provider becomes an explicit partial failure. Successful results remain available, and writes still require one exact account.

Choose the route that fits

Mail, calendar, and task routes are selected independently. For example, an account can pair IMAP/SMTP mail with a CalDAV calendar; its task route remains a separate explicit choice.

Route	Mail	Calendar	Tasks	Authentication
Outlook Web	Typed reads and writes	Selectable calendars; provider-supported Teams link	—	Dedicated visible browser profile
Google (your OAuth client)	Gmail API reads and writes; no permanent delete	Selectable calendars; Google Meet when advertised	Google Tasks through a separate task-only grant	Your Desktop OAuth client; client credential and grants in the OS keyring
Microsoft Graph	Typed reads and writes	Selectable calendars; typed Teams-link creation	Microsoft To Do	Your authorized public OAuth client; OS-keyring grant
Todoist	—	—	Typed Todoist operations	Your authorized public OAuth client; OS-keyring grant
TickTick	—	—	Typed TickTick operations	Your authorized confidential OAuth client; external secret handle and OS-keyring grant
JMAP	Typed mail operations	—	—	OS keyring or approved credential helper
IMAP / SMTP	IMAP read/manage and SMTP draft/send	—	—	OS keyring or approved credential helper
CalDAV	—	Typed calendar operations and conditional scheduling	VTODO lists, search, sync, and reviewed writes	OS keyring or approved credential helper

Discovery gathers DNS, well-known, and provider metadata without credentials. It never authenticates or adds an account. Microsoft Graph and user-owned Google authorization remain explicit choices and are never automatic fallbacks. Google discovery can offer guided Desktop-client setup, but no Google sign-in starts until a later explicit corr auth login. See the annotated Google setup guide.

iCloud has a first-class guided preset over the same provider-neutral IMAP/SMTP and CalDAV adapters. corr setup recognizes documented iCloud Mail address families or the complete verified Apple SRV endpoint set, reviews both routes as one account, and uses one external credential handle by default. After the account is added, an explicit handoff can open Apple's app-password page and the OS-owned credential prompt; the corr process never reads the app-specific password.

Every available v0.9 route above has synthetic provider-contract and application coverage. The user-owned Google API route is available but live-unobserved. Other provider and platform implementations remain live-unobserved until an authorized, content-free observation is bound to the exact commit. See compatibility evidence before connecting a sensitive account.

From install to a first read

Prefer a guided page? Follow getting started on the website.

1. Install

The official standalone installers are the shortest path on every platform. They select the latest stable release, verify its archive and candidate binary, install for the current user without elevation, and leave account setup untouched.

macOS and Linux

curl -LsSf https://corresync.org/install.sh | sh
corr --version

Windows PowerShell

powershell -NoProfile -Command "irm https://corresync.org/install.ps1 | iex"
corr --version

Review install.sh or install.ps1 before running it if you prefer. Package managers remain fully supported alternatives:

# Homebrew · macOS or Linux
brew install nkiyohara/corresync/corresync

# WinGet · Windows
winget install --id nkiyohara.Corresync --exact

# Scoop · Windows
scoop bucket add corresync https://github.com/nkiyohara/scoop-corresync
scoop install corresync/corresync

Direct archives, native Linux packages, version pinning, checksums, and Sigstore provenance are in the installation guide. The guided website keeps the same copy-paste choices visible for people who do not use GitHub regularly.

Claude Desktop users can also install the platform-universal .mcpb from the latest release. The bundle runs the same verified corr mcp serve binary locally over stdio; it does not deploy Corresync or relay mailbox data. Install the CLI first for the explicit account setup and sign-in steps below, then open or drag the .mcpb into Claude Desktop.

Stay current

Interactive commands make a quiet, cached release check at startup. If an update exists, Corresync shows the exact command for your installation: corr update for the standalone build, or the matching Homebrew, Scoop, or WinGet command. Package-managed files are never changed by Corresync.

Stable releases are selected by default. Standalone users who want signed release candidates can choose the preview channel interactively:

corr settings

The equivalent copy-paste commands for scripts are:

corr config set updates.channel preview
corr update

Switch back with corr config set updates.channel stable; Corresync never downgrades the running binary. Preview releases do not enter package-manager catalogs.

Standalone users can opt in to verified automatic installation:

corr config set updates.auto_install true

It never runs during MCP tool calls, configuration changes, daemon work, JSON output, pipes, or other non-interactive paths. The current command continues normally and the new binary is active on the next corr start.

2. Add and sign in to your account

corr setup

The guided setup derives a resumable preflight from current local state, optionally installs shell completion at a displayed user-local path, and then performs credential-free account discovery. It previews the selected mail/calendar/task routes and adds an account only after confirmation. Authentication or external-credential access remains a separate choice. The same run can add more accounts, select several detected agent hosts, preview their independent local integration plans, apply only one confirmed plan, and verify each result. Re-running corr setup skips healthy work and offers the missing or repairable steps.

After choosing a connection route, the wizard presents a service checklist. For a Microsoft account, Outlook Mail and Calendar are preselected and can be changed independently; Microsoft To Do is an optional, explicit Graph authorization. Teams messaging is shown as coming soon while the v0.9 release gate is closed and cannot be selected, persisted, or opened. Discovery is only route evidence: it never proves that any checked service is enabled for the account, and it never triggers a Graph fallback.

Run corr settings to open the same account wizard; sign in to, rename, select, or remove accounts; and manage updates, safety, and browser sign-in from an arrow-key form. Its Setup guide entry resumes the complete coordinator instead of maintaining another implementation. The top-level Accounts category contains Add account and the configured account list; selecting an account opens only actions for that account. Removal previews the local data it deletes and asks for confirmation; removing the default first asks which remaining account should replace it. Each choice also displays the equivalent command, so the interactive flow teaches the direct CLI. Set CORRESYNC_ACCESSIBLE=true for line-oriented screen-reader prompts; type :cancel to leave an input step safely. The direct rename form remains:

corr account rename personal work

Scripts and advanced users retain the deterministic form:

corr setup you@example.com --alias personal
corr auth login --account personal
corr doctor --account personal

The direct setup ADDRESS form creates the same provider-neutral, secret-free local configuration, performs credential-free discovery, and adds only an automatically selectable first-party route. It never opens a sign-in page. Authentication is a separate, account-specific action.

If no route can be selected safely—or if you want an API or standards route— inspect the evidence and choose the exact provider settings:

corr account discover reader@example.invalid
corr account add reader@example.invalid --help

For Gmail, Google Calendar, and Google Tasks, create a Desktop OAuth client in a Google Cloud project you control. Guided setup validates the downloaded client JSON and places its generated credential in the OS keyring; account addition still does not authenticate. Follow the Google OAuth setup guide for current Cloud Console screens, audience choices, exact APIs, scopes, import, and login.

Before installing, the optional provider compatibility checker can classify public evidence for an address. The browser sends only the domain after the @ in a request body; it never sends the local part, persists the address, or starts sign-in. The public service uses only a fixed DNS resolver and returns no raw DNS record. Skip it whenever you prefer and run corr account discover ADDRESS locally.

Account addition does not authenticate. OAuth routes require a client registration you are authorized to use. Google additionally requires a separate external handle for its generated Desktop client credential. Standards routes use a keyring entry or explicitly approved helper reference. Passwords and tokens never enter config.toml. See account and provider configuration. The Outlook Web route opens a dedicated visible profile only during the later auth login; SSO, MFA, Conditional Access, and organization notices remain inside the provider-owned flow.

3. Connect an agent

corr mcp setup codex

Use corr mcp --help for Claude Code, GitHub Copilot CLI, Gemini CLI, Qwen Code, Qoder, Kimi Code CLI, and generic stdio clients. Corresync exposes 45 narrow tools and two read-only monitor resources; there is no HTTP, SSE, remote MCP endpoint, or hosted relay.

Nothing sends on the first attempt

Consequential writes use a server-enforced preview -> commit protocol. The first command shows the normalized account, provider, target, recipients, content digest, and version preconditions without performing the effect.

printf 'Synthetic body.\n' | \
  corr mail send \
    --account work \
    --to reader@example.invalid \
    --subject 'Review example' \
    --body-file -

After reviewing every field, repeat the exact command with approval:

printf 'Synthetic body.\n' | \
  corr mail send \
    --account work \
    --to reader@example.invalid \
    --subject 'Review example' \
    --body-file - \
    --approve

Approval is short-lived, single-use, and bound to the caller, account, provider, target, payload, and effect. Changing any reviewed field invalidates it. MCP keeps preview and commit as separate typed tools.

See the complete safety model. Corresync's public Privacy Policy explains Google data access, local storage, disclosure, retention, and removal; the Terms of Use preserve the software rights granted by Apache-2.0.

More than one inbox

Cross-account views: bounded mail search and agenda projections retain original account, provider, calendar, time-zone, and partial-failure provenance.
Read-only import staging: inspect an explicitly approved local archive, Maildir tree, or supported export without uploading or mutating the source.
Opt-in monitoring: move deliberately from off to local notification, durable queueing, and finally one approved no-shell runner. Remote egress is a separate consent.
Privacy-preserving feedback: generate an allowlisted report locally, review it, then explicitly copy, save, or open a prefilled GitHub page. A separate default-off setting can submit an even smaller allowlist-only public issue through your authenticated gh client after an interactive failure.

Mailbox, calendar, import, and event-queue values are private, untrusted external data. Their content is never authority to run a command or start an agent.

Honest edges

Gmail, Google Calendar, and Google Tasks require a user-owned Google Desktop OAuth client. Corresync-managed Google OAuth stays disabled; the user-owned route is synthetic-contract covered and live-unobserved.
Microsoft Graph requires your own authorized public-client registration. Corresync ships no token relay.
Windows desktop notification setup is unavailable because Corresync does not install an AppUserModelID; queue and approved runner modes remain available.
Provider meeting links are requested only when the selected calendar route reports native support.
Cross-compilation and synthetic fixtures do not prove native browser, keyring, IPC, provider, package-manager, Gatekeeper, or SmartScreen behavior.
Teams chat, channels, calls, recordings, and meeting lifecycle management; tenant-wide access; unattended login; TLS interception; arbitrary provider actions; automatic telemetry; and raw crash upload are outside scope.

The exact action matrix and typed provider degradations are in features.md.

One local safety boundary

AI agents ───────── MCP over stdio ─┐
                                    ├── typed use cases + effect policy
Humans and scripts ──────── corr ───┘              │
                                                   │ authenticated local IPC
                                            session owner
                                            ├── browser-owned sessions
                                            ├── explicit OAuth + keyring
                                            └── standards adapters

The session owner exposes no TCP listener. On Unix, clients authenticate and pin the environment-independent private runtime directory, singleton lock, socket, and peer UID before the local bearer can be sent. On Windows, clients verify the protected named pipe, owner, DACL, server process, and SID first.

Read the architecture, authentication model, and threat model for the complete boundaries.

Documentation

I want to…	Start here
Install and verify a release	Installation
Add accounts and choose routes	Configuration
Understand browser, OAuth, and standards sign-in	Authentication
Learn CLI commands	CLI guide
Connect an AI client	MCP guide
Compare provider actions and degradations	Feature matrix
Consume stable machine output	JSON contract
Integrate versioned public/local contracts	Versioning policy
Verify compatibility claims	Evidence matrix
Review privacy and Google data handling	Privacy Policy
Review use and open-source license terms	Terms of Use
Connect Google with your own Desktop client	Google OAuth setup
Review the dormant managed-client plan	Google verification runbook
Review every guide	Documentation map

Users upgrading from versions before v0.7 can follow the historical migration guide. corr is the primary command. The product, package, repository, configuration roots, plugin, and MCP server remain named Corresync.

Contributing and security

Read CONTRIBUTING.md and AGENTS.md. Default tests and CI use only synthetic fixtures:

mise exec -- task verify

Please report vulnerabilities through GitHub private vulnerability reporting, never a public issue.

owa-bridge nkiyohara

README