Workers IO builds deterministic simulation environments for verifying mission-critical software.

Modern systems fail in ways no test suite catches: a retry lands during a partial outage, two writes interleave, a dependency times out at exactly the wrong moment. Teams find these bugs in production, after an incident, with no way to reproduce them.

We fix that. Workers IO runs your entire system inside deterministic virtual machines and searches through millions of interleaving, faults, and timings to find the exact conditions that break the promises you care about: no lost writes, no double fills, no split-brain.

Why now

Coding agents are writing more of the world's software, and they need a feedback loop stronger than "the tests passed." We give agents and engineers a way to verify a change against production reality.

Who we build for

Teams where 99.99% uptime is table stakes and someone is accountable for incidents: payments, trading, infrastructure, healthcare, and the platforms other companies run on.

Where we are

• Backed by Y Combinator and the Solo Founders Program, and some of the best angels.
• Small founding team, deep systems focus, high ownership

If you like operating systems, distributed systems, formal-ish thinking applied to real software, and you want your work to be the reason a payment system did not lose a write, we should talk.