About Antithesis

We've been quietly reinventing how the world thinks about software reliability, and we're just getting started! At Antithesis, we start at the foundations – we run entire software systems inside a deterministic simulation and break them in every way imaginable. Every issue then comes with a perfect reproduction, so you can identify root causes fast instead of spending days trying to recreate what went wrong.

The rise of AI-generated code has made this work more urgent than ever. Agents can write code faster than any human, but speed doesn't matter much when the output is buggy, stuck in review, or slipping through undetected. The verification bottleneck is real, it's growing, and solving it is one of the most consequential problems in software right now. That's what you'd be working on.

We're well-funded and deeply technical, the kind of place where the hardest problems get the most attention and the best ideas win regardless of who has them. If you want to do work that actually moves the needle on how reliable software can be, keep reading.

About the Role:

This role, on a team based in London, is responsible for building out Hegel, our new family of property-based testing libraries. We are building open source libraries to provide top quality property-based testing in every language, both for the benefit of the community at large, and because it provides a natural on-ramp for potential customers to test their software in Antithesis.

Must have for this role:

• Experience using property-based testing (PBT). Experience with Hypothesis would be slightly preferred but experience with any other PBT library is fine too.

• We lean heavily on AI assistance in developing Hegel, with a lot of human review and care to maintain quality. You don’t need to have any experience with such workflows, but you should be comfortable with the idea of using them.
  

Nice to haves:

• Familiarity with at least one, ideally both, of Python and Rust.

• Willingness to work in a variety of languages.

• Expert-level in at least one language that you would be keen to be “tastemaker” for a Hegel implementation.

• Having maintained an active open source library is a strong plus.
  

The Tech:

• You can see most of the tech in question on https://github.com/hegeldev.

  • hegel-core is Python, and hegel-rust is our most mature client library. We also have go, typescript, C++, and OCaml (some not yet public). We’re not immediately planning to support more, but if there’s some language you’d be keen to add support for feel free to let us know.

  • We are heavy Claude Code users.

  • Antithesis more broadly are heavy Nix users, and it would be a plus to be familiar with that, but because Hegel integrates with existing language package managers we are not actually heavy users of it on this team in particular.

The Culture

Our team is composed of people with a variety of backgrounds: standard engineering degrees to philosophy degrees; big-tech backgrounds to scrappy startups. But we have at least one common skill: everyone on the team, including managers, is held to the same high standard of engineering competency. In addition, we value in-person work for its value in building trust and sharing knowledge and mentoring each other.

Note: This is an 5 days a week in-office job in London, UK