Mastra · The most-downloaded TypeScript agent framework there is — 1,240,131 weekly installs of @mastra/core — which makes it the reference point for anything we publish about what building an agent in TypeScript actually costs.

An open-source TypeScript framework for building agents — models, tools, memory and instructions in one object, typed multi-step workflows that survive restarts, and persistent conversation state — plus a hosted platform to run and watch them. The platform is now five named products: Framework, Factory ("issue to production, run by agents"), Studio, Observability, Agent Builder and Server. Apache 2.0 at the core, with enterprise features under a separate source-available Mastra Enterprise License.

Sector

Agent frameworks

Stage

Series A

On the roster since

15 Sept 2026