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Mastra

Open-source TypeScript framework for AI agents

Raised to date

$36.2M

of $36.2M offered across 1 Form D filing

Investors
157
Last filed
May 15, 2026

About

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.

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.

Funding

  • EquityFiled May 15, 2026Form D
    $36.2M/ $36.2M

Product

Mastra Framework

Developer tools

Open-source TypeScript framework for defining typed agents with instructions, models, and tools, and for composing multi-step workflows with retries and branching.

  • Typed agents and multi-step workflows
  • Memory with conversation history and semantic recall
  • Model router covering 90+ AI providers

Built for

Engineering teams building customer-facing AI products, internal automation agents, and developer platforms

People on file