Mastra

Mastra is an open-source TypeScript framework for building AI agents, workflows, and RAG applications, giving JavaScript/TypeScript developers agents, tools, memory, typed workflows, and evals in their native language. The core is free and self-hostable, with an optional Mastra Cloud for managed deployment and observability. It is young but well-funded, having raised a $22M Series A in April 2026.

Mastra brings agent development to the TypeScript ecosystem, positioning itself as something like 'Rails for AI agents.' It provides primitives for agents with tool calling and memory, typed workflows for multi-step and branching logic, RAG helpers, and built-in evaluation, all in idiomatic TypeScript so full-stack and front-end-leaning teams can build agents without switching to Python. It comes from the team behind Gatsby and has grown quickly in adoption and GitHub stars. The framework is open source and free to self-host. Mastra also offers Mastra Cloud, a managed deployment and observability layer for running agents in production without managing infrastructure. This creates the familiar open-source-core plus managed-cloud split: build and run locally for free, or pay for hosting and operational tooling as you scale. Mastra is young but well-funded, having raised a $22M Series A led by Spark Capital in April 2026 on top of a 2025 seed, and it shipped a 1.0 release. That momentum and its TypeScript-native design make it appealing for JS teams, though its relative newness means the ecosystem, integrations, and long-term API stability are still maturing compared with older frameworks.