We're incredibly excited to announce a $13m seed round from 100+ of Silicon Valley's top investors for Mastra, the leading Typescript agent framework.
We spent the last decade building a framework (Gatsby) that hundreds of thousands of developers used to build with React.
We're spending the next decade building a framework (Mastra) that tens of millions of developers will use to build agents.
We believe that every developer should be able to build with AI — and AI allows everybody to be a developer.
How we got started
First off, we're Typescript guys. We spent the last decade with battle scars from building Gatsby. I was the cofounder, Abhi was the principal engineer, Shane was staff eng and head of product.
Last October, Shane, Abhi and I were struggling to build agents for sales. The tooling just sucked. After we got back from a weekend hackathon, the idea came up that we should build better tooling instead.
At that point, something magical happened. We sort of looked into each other's eyes, and saw the next decade of our lives flash before us.
We knew we could do it. But, we also knew what the task would demand from us.
So we started building. We came to YC, ground zero of vertical agents in Jan.
Around mid-February, we started to take off of, and since then, we've been furiously, frantically shipping to stay ahead of our community's needs.
Out: “party round”. In: “coalition round”
In March after YC, we raised a seed round.
We don't really keep score this way, but this is the largest post-YC cap table, as far as we can tell, in several years:
Our full list of investors is at the bottom.
Companies like Softbank, Adobe, PayPal, and Replit are building with Mastra
Since February, Mastra has evolved into a framework that's not just the easiest way to get started building with AI. It's the easiest way to ship into production. We have agent and workflow primitives, all integrated into a playground experience our users love. We have tool calling and memory, evals, tracing, and
Replit's Agent 3 builds Mastra agents at scale. Softbank announced a product on stage built with Mastra. March McLennan has 75,000 employees using an agentic search tool they built with Mastra.
Elastic and Docker wrote up blog posts about their Mastra usage. Companies like PayPal and Adobe are going into production with Mastra.
We're the third-fastest-growing JavaScript framework ever
NPM has data back to 2015, so we made a list of 100 well known packages and tracked growth from 10k weekly downloads (where growth becomes regular) to sustained 150k downloads.
We grouped them into frameworks, libraries, SDKs, and tools and we're the third-fastest growing JavaScript framework....ever.
Another way of looking at it: after four years of building Gatsby (May 2015 → May 2019) we were at ~190k weekly downloads.
That's where we are after one year of building Mastra (Oct 2024 → Oct 2025).
We got the band back together
One of the best parts: as we raised money, we called up the most talented engineers we'd worked with.
The number of people who are great at open-source JavaScript is somewhere around the Dunbar number. A lot of them work at Mastra.
We wrote a book and printed 70k+ copies
While we were in YC, we wrote a book called Principles of Building AI Agents.
The title is pretty explanatory: it covers all the key concepts: agents, workflows, tools, memory, evals, tracing, and so on.
We wrote it during YC because we found ourselves explaining the same concepts over and over in whiteboarding sessions. People tell us it's incredibly helpful when you're starting to build agents.
We've given over 70,000 physical copies out since March (and another 100k+ digital copies). We bring it to every meetup and conference we can. Our LinkedIn book posts go viral.
So if you haven't gotten your copy yet: mastra.ai/book.
We'll keep scaling book distribution until we get a copy to every engineer who writes JavaScript and is interested in AI.
We're throwing a Typescript AI conference in November
To have a place for the Typescript builders, we're throwing TS AI Conf this November in SF. We're going to have 300+ builders there and with speakers like David Cramer, Michael Grinich, Paul Klein, Dex Horthy, and swyx.
We'd love for you to come: https://tsconf.ai/
Get started building
So head over to your command line and get started:
npm create mastra@latestHappy building!
Full list of investors:
GOAT: Paul Graham (YC)
Unicorn+ founders: Arash Ferdowsi (Dropbox), Shay Banon (Elastic), Guillermo Rauch (Vercel), Amjad Masad (Replit), Tristan Handy (dbt), David Cramer (Sentry), Alex Atallah (OpenSea), Tracy Young, Ralph Gootee, Ryan Sutton-Gee, Kenny Stone (Plangrid), Ryan Noon (Material Security)
Exited founders: Balaji Srinivasan (Counsyl), Rafael Garcia (Clever), Kulveer Taggar (Zeus), Rich Aberman (WePay), Taro Fukayama (Fond), Samvit Ramadurgam (Forge), Adrien Treuille (Streamlit), Umur Cubukcu & Ozgun Erogan (Citus)
Current seed/A/B founders: Flo Crivello (Lindy), Michelle Valentine (Anrok), Alex Chantavy & Kunaal Sikka (Subimage), Henry Liu (Span), Trevor McKendrick (Seis), Alexey Taktarov (Fira), Manuj Mishra & Diogo Valdivieso (Waffle), Lorcan O Cathain (Lua), Gabriel Kho, Trent Hazy (Flax), Robin Choy (HireSweet), Matt Slotnick (Poggio), Dan Robinson (Detail), Josh Schlisserman (stealth), Bob Remeika (Ragie), Hari Raghavan (Autograph), John Laxson (Reveal), Ravi Chachra (8vdx), Matt Lenhard (Stealth), Rakesh Agarwal (Snapstream), Sara Du (Ando), Dex Horthy (HumanLayer), DC Posch (Daimo), Matt Slotnick (Poggio), Ranajay Sen (Plover), Pranay Srinivasan (Manufactured), David Mytton (Arcjet), Kuberan Marimuthu (Cypher), Benjamin Simon (Axilon)
Institutionals: YCombinator, Gradient Ventures, basecase capital, SVAngel, Terrence Rohan, Orange Collective, Palm Drive, Runa Capital, Pioneer Fund, Liquid2, Ritual, Garuda, Conversion, Defy, Lombardstreet, Founders Network, Ride Home Fund, Founders You Should Know, Script Capital, Broom Ventures, Scale Asia, Moonfire, Transpose, Founders Hobby Fund
Eng & product leaders: Jack McCloy (Snowflake), Dustin Schau (Postman), Amitav Chakravartty, Jon Natkins (Braintrust), Steven Li (Meta), Alex Andon (Meta)
Operators: Cailen D’Sa, Neel Murthy (Rippling), Coyne Lloyd, Nate Matherson (Numeral)
Investors: Oliver Jung, Kevin Moore, Laura Yao, Naomi Ionita, Ali Nahm, Michael Stuenkel, Lyon Wong, Jeff Chang, Chris Smoak, Chris Golda, Benjamin Bryant, Jonathan Golden, Patrick Deem, D'Arcy Rice
Friends: Eugieno Carnemolla, Sebastian Gutierrez, Christian Mathiesen, Walter Vulej, Ryan Oines, Adam Learing, Andrew Yang, Rami Khalaf, Mahir Kalra