from Hacker News

60–70% of YC X25 Agent Startups Are Using TypeScript

by Arindam1729 on 6/7/25, 8:50 PM with 17 comments

I recently saw a tweet from Sam Bhagwat (Mastra AI's Founder) which mentions that around 60–70% of YC X25 agent companies are building their AI agents in TypeScript.

This stat surprised me because early frameworks like LangChain were originally Python-first. So, why the shift toward TypeScript for building AI agents?

Here are a few possible reasons I’ve understood:

- Many early projects focused on stitching together tools and APIs. That pulled in a lot of frontend/full-stack devs who were already in the TypeScript ecosystem.

- TypeScript’s static types and IDE integration are a huge productivity boost when rapidly iterating on complex logic, chaining tools, or calling LLMs.

- Also, as Sam points out, full-stack devs can ship quickly using TS for both backend and frontend.

- Vercel's AI SDK also played a big role here.

I would love to know your take on this!

  • by ecesena on 6/7/25, 9:50 PM

    I'm not surprised, I don't think it has anything to do with AI, it's the same in blockchain and prob in all other fields.

    I think ppl underestimate the cost of context switch between languages, even if you're really proficient in more than one.

    If you're a team with 1-2 eng and have to build a frontend, you are forced to use js/ts. Now, if you can keep everything in a monorepo in the same language, you're simply moving faster. And I'm sure people will criticize and bring counter examples... but statistically 60-70% of the teams will just be faster working this way.

    My first startup was frontend php, backend python, 2 eng; soon we specialized one working on frontend, the other on backend, it's tedious to context switch. My last startup was typescript for everything, again 2 eng, same code base, same coding style, both iterating on all code. (And daily I work in rust & C, I'm definitely not a frontend eng nor a js/ts enthusiast, I'm just reflecting on efficiency.)

  • by foobarbaz33 on 6/8/25, 2:12 PM

    Web based UI's (javascript baked in) are the only cross platform GUI all the major tech players endorse. Companies like Apple are hostile to alternative GUI frameworks, except web browser. Flash? that threatens the walled gardens so the big tech cartel came together to squash it out. Java graphics? we will not ship a JVM becuase "security". The web was already ubiquitous so the big tech couldn't squash it without squashing their own foot.

    Typescript let's you start with a cross platform GUI right out of the gate. Text based HTML GUI is screen reader friendly, battle hardened for many years to get accessibility right.

    Type system is advanced and allows for that sweet IDE experience.

    And.... the Javascript ecosystem is the only game in town that gets close to the Lisp immediate feedback experience. (no Javascript is not as good as a lisp image, but it's better than nothing). Change a function, see the result instantly in the browser while you're app is still running. I'm not 100% sure this is true for Typescript as it must compile to javascript first, but compiling the TypeScript for 1 modified file with an on-save-hook could still be a pretty quick feedback loop.

    Do these reasons have anything to do with AI agents? no but it would explain why people are already using Typescirpt, and thus use it for AI agents.

  • by shams93 on 6/7/25, 9:03 PM

    The agent layer is a kind of client and since typescript thanks to node and the browser has become a universal language for client sides, whether the client is used by a human or used agent to agent.

  • by amazingamazing on 6/7/25, 11:33 PM

    Makes sense - for front-end there's really no alternative. For back-end node.js is more than fast enough for pretty much any startup.

  • by tomasen9987 on 6/7/25, 8:59 PM

    This is interesting, TBH the Ease of using FE & BE in Typescript is the reason I think. I'm also using TS for that.

  • by pianopatrick on 6/8/25, 8:06 AM

    Is there a recommended typescript library for building AI agents?

  • by iMax00 on 6/7/25, 9:05 PM

    much more easier to built UI

  • by rvz on 6/7/25, 9:11 PM

    > - Also, as Sam points out, full-stack devs can ship quickly using TS for both backend and frontend.

    Typescript (which is still "Javascript") is extremely immature for a "backend" language.

    I can't take anyone seriously if they believe or use such a pseudo-typed language like typescript and especially a weakly typed language with dynamic types on a costly runtime such as Javascript on the backend.

    Both of them should stay far away from anything backend.