TypeScript developers building AI agents in 2025 had a problem: Python had LangChain, LlamaIndex, and a growing ecosystem. JavaScript had roughly nothing that felt production-ready.

Mastra changed that. Built by the team behind Gatsby and backed by Y Combinator (W25), Mastra shipped its 1.0 release in January 2026 and crossed 22,000 GitHub stars within 15 months of launch. By 1.0, weekly npm downloads had hit 300,000. As of May 2026, the package is at v1.8.1 — actively maintained, not a prototype.

This guide walks through what Mastra actually includes, how its core primitives work, and where it fits in the agent framework landscape.

What Mastra Is

Mastra is a TypeScript framework for building AI-powered applications and agents.…