mastra

Mastra is a TypeScript framework for building AI agents into a web app: agents with tools and memory, workflows that can pause for a human to approve and then resume, RAG, evals and tracing. It routes to 40+ model providers through one interface and drops into a Next.js or Node app, or runs as its own server. The core is Apache 2.0, from a Y Combinator company.

Self-hosting the framework just means deploying your app. The paid layer is Mastra Platform for tracing and hosted deployment: free for 100K events and 24 CPU hours a month, then Teams at $250/mo for 1M events, 250 CPU hours, six months of retention and SSO. Enterprise is custom.

TypeScript teams who don't want to live in Python: this is the most complete option. Solo and small teams: the free framework plus the free platform tier. Compare it with langchain-ai/langchainjs for a bigger ecosystem, or Vercel's AI SDK for something lower-level.

The catch is the ee folders. RBAC, SSO, fine-grained permissions and the visual agent builder sit under a separate Enterprise license: readable, but not for production without a paid key. Mastra has rewritten that license three times this year. Know which imports you're pulling in.