Senior Software Engineer - Fuzzer

At the heart of Antithesis is the Fuzzer, our autonomous search engine for bugs and one of the most technically ambitious components in our stack. It orchestrates actions and randomness, hunts for new system states and failure modes, and runs continuously without ever letting up. As a Senior Engineer on the Autonomous Search team, you'll own and evolve it.

The problem space is genuinely unsolved, we have more ideas than we could possibly execute on, and the work you do will directly shape how it all gets figured out.

- Own core Fuzzer functionality: orchestrating how systems under test are explored, injecting controlled chaos, and navigating the state space to find bugs in simulated environments.

- Make the Fuzzer smarter: improve code coverage, search efficiency, and expand the kinds of bugs it can discover.

- Design clean, stable interfaces so the rest of the product and external systems like ML models and AI agents can plug in and configure search.

- Build observability and benchmarking to measure Fuzzer behavior and guide development decisions.

- Write clear design docs, mentor engineers, and contribute to the long-term roadmap.

We want engineers who think deeply about correctness, aren't satisfied with "it mostly works," and find the problem space of software testing genuinely fascinating. If you've looked at the state of software reliability and thought we can do so much better , you'll fit right in.

- 5+ years of engineering experience working on complex systems, in industry or research.

- Strong proficiency in Rust, Go, C++, or equivalent systems programming experience; safe, performant, idiomatic code is second nature to you.

- Strong CS fundamentals in data structures, algorithms, and systems design, with a habit of solving problems from first principles.

- Experience designing clean interfaces between complex subsystems, and the ability to explain hard things clearly to any audience.

- A genuine passion for software testing and correctness is a must , whether through building testing infrastructure, contributing to tooling, or just spending too much time thinking about why software is so buggy.

Bonus: Experience with fuzz testing frameworks like libFuzzer, AFL, or Honggfuzz; property-based testing tools like QuickCheck, Hypothesis, or PropTest; program analysis or formal methods; ML/AI-driven search; deterministic replay; or open-source testing contributions.

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 in office in Vienna, VA.