Senior Software Engineer

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

We're looking for engineers in the Senior to Staff levels to build the future of autonomous testing. No matter your particular field of experience, if you've been ambitiously building complex software and think you could be a fit; drop us a note.

In this role you will be part of the team that maintains our open-source project Bombadil (https://github.com/antithesishq/bombadil). This includes working with the specification language and verifier, Chromium automation, advanced property-based testing, frontend development, and much more.

Must have for this role:

• Proficient in Rust development

• Experience with property-based testing or fuzzing

• Comfortable with web technology (browsers, HTTP, HTML, Javascript, CSS)

Experience that would be a plus:

• Chrome Devtools Protocol, Playwright, Cypress, or Selenium

• Formal specification languages (e.g. TLA+ or some LTL)

• Implementing parsers, type systems, and interpreters

About Our Team

Our team spans CS degrees, philosophy, mathematics, and everything in between, or nothing formal at all. What everyone shares is a high bar for engineering quality. We work in-person because it's how we build trust and tackle hard problems together.

Location: This position is full time in the office in London, UK.

Visa Sponsorship: We are unable to provide visa sponsorship or immigration support for this position. Candidates must be authorized to work in the applicable country without current or future sponsorship requirements.