$36.2M
+$36.2M this year1 filing since 2026 · latest Equity filed
Mastra, legally Kepler Software Inc., makes an open-source TypeScript framework for building AI agents, workflows, and RAG pipelines, plus a commercial cloud platform for deploying, observing, and evaluating those agents. The founders previously built Gatsby, and the company went through Y Combinator's Winter 2025 batch. It raised a $22M Series A led by Spark Capital in April 2026, bringing total funding to $35M. Customers include Brex, Sanity, Factorial, Indeed, and Marsh McLennan.
What sets it apart
A TypeScript-native, Apache-2.0 open-source agent framework that bundles agents, workflows, memory, a model router covering many providers, and built-in observability, with a hosted platform on top.
Open-source TypeScript framework for defining typed agents with instructions, models, and tools, and for composing multi-step workflows with retries and branching.
