Open source repo

What's inside simstudioai/sim

simstudioai/sim is a TypeScript repo with 4,073,540 lines written in 10,948 files. sim is built with Next.js, React, and FastAPI and uses Postgres, Redis, MongoDB, and 7 more. AI signed 5.3% of the 8,178 commits of sim.

Its description on GitHub: “Sim is the collaborative workspace to build, deploy, and monitor AI agents and workflows. Used by 100,000+ builders.”

TypeScriptApache-2.029,966

Read on November 2, 2026, at commit df7709b.

What the card proved: what it’s built with on the left, what it uses on the right.

See each one with its proof

Its folders

TechnologiesWhat is sim built with?sim is built with Next.js, React, and FastAPI and uses Postgres, Redis, MongoDB, and 7 more.

+5 Who writes itHow much of sim did AI write?5.3%AI signed 5.3% of the 8,178 commits of sim.

In figures

lines written: 4,073,540; The ones people and agents wrote: product, tests, schemas and tooling. Generated code doesn’t count.
files: 10,948; The product’s, not counting tests.
test files: 3,682; The files that test the code.
technologies: 13; Each service with the file and line that prove it.

SeeRepo read the facts in its code and kept none of it. AI only helps sort its packages and folders by their names, and never sees its code.

Frequently asked questions

What is simstudioai/sim?

simstudioai/sim is a TypeScript repo with 4,073,540 lines written in 10,948 files. Its description on GitHub: “Sim is the collaborative workspace to build, deploy, and monitor AI agents and workflows. Used by 100,000+ builders.”

The proof: its page on GitHub

What is sim built with?