The job
Square8 builds AI workers: agentic systems that hold down real jobs inside companies, follow the rules they’re given, and log every action they take. Our first worker is already live in production.
We build them with a small team directing large fleets of AI coding agents. Whether that works comes down to the machinery around the agents: the specifications they build from, the verifiers that check their work, the tests that catch what the verifiers miss, and the evaluation that tells you whether things are getting better or just changing.
That machinery is your job. You’d own how Square8 builds software.
It also sits closer to the product than internal tooling usually does. Verification, audit and bounded autonomy are what we sell. Solving them for our own engineering is a first pass at solving them for customers.
Ideal profile
You’ve built the harness other engineers reached for by choice. Now you want the bigger version of that problem: the machinery that lets a small team direct large fleets of AI agents and trust what comes back. That is where software engineering is going, and almost nobody has built it properly yet. You’d build it here, on a product where verification is the thing we sell.
What you’ll do
- Own the specification format. Everything the agents produce depends on it
- Build the orchestration: dispatch, isolation, parallelism, cost control
- Build the verifier agents that check AI-written code, and measure honestly what they catch and what they miss
- Build testing for systems that aren’t deterministic: replay, seeded runs, and flakiness you can act on
- Make correctness something the system establishes, rather than something a person has to go looking for
- Own verification inside the product itself, once you’ve solved it for us
What you’ll bring
- You’ve built infrastructure that other engineers used by choice
- Hands-on experience running coding agents at scale, and clear views on where they break
- Comfort with statistics: catch rates, base rates, and knowing when a number isn’t good enough to act on yet
- You’ll argue with our CTO, and we’d be worried if you didn’t
Nice to have: agent orchestration infrastructure, open evaluation frameworks, build systems at scale, developer-productivity work where you owned the metric.
What we offer
Compensation is a combination of cash and a share plan, worked out between you and the founders. You’d work alongside the CTO as a peer, with no layers in between. Direct work with a real enterprise customer from your first week. This is an in-person role, based in Zurich, Lisbon or London.
How we interview
Three conversations. First a short one, to see whether what you want to work on and what we need line up. Then a longer conversation about the system we’re building, where what interests us is how you think about it: what you would question, what you would expect to be hard. Then a deep dive with the whole early team.
Square8 is an equal-opportunity employer. If your background is unusual for this role, that may be exactly the point. Tell us why.