Corsair

Corsair is an open-source integration layer for AI agents and apps: secure multi-tenant OAuth, permission management, MCP support, webhooks, credential handling, caching and provider-specific error handling for Gmail, Slack, Notion, HubSpot, Airtable, Google Calendar, Stripe, Linear, GitHub and Discord — the services your users actually expect agents to touch.

The pitch is "add any integration in minutes" and the numbers back the credibility: 11.3k GitHub stars, self-host the SDK for free or use their managed cloud so you never maintain token rotation, webhook verification, API change tracking or rate-limit handling yourself. Anyone who has built OAuth flows for more than two providers knows exactly how much unpaid plumbing that is.

Who it's for: developers shipping AI agents or assistant products who want integrations as infrastructure instead of a permanent side project. Bring your own execution (hosted or self-hosted instances) and keep tenant credentials isolated. If your roadmap has "add Slack integration" penciled in for the third sprint in a row, this buys that time back — just review the self-host docs before committing your credential storage architecture to it.