Software Engineer

We are looking for experienced software engineers to help train and evaluate AI models on real-world programming work. You will build and validate coding tasks, review AI-generated code, and write the reference solutions and tests that models are measured against. Your engineering judgment directly shapes how reliably AI systems write, debug and refactor code.
Key Responsibilities
- Design realistic coding tasks (bug fixes, feature implementation, refactoring, performance optimisation) with clear specifications.
- Build reproducible environments (Git, Docker) and write automated test suites that verify solutions.
- Write high-quality reference solutions and explain the design decisions behind them.
- Evaluate AI-generated code for correctness, performance, security and readability.
- Rank and compare model outputs and justify your judgments in clear written rationale.
- Identify recurring failure patterns in model output and report them to the project team.
- Follow project guidelines, take part in calibration and review sessions, and incorporate feedback to keep quality consistent.

Required Qualifications
- Degree in computer science or a related field, or equivalent professional experience.
- 3+ years of professional software engineering experience.
- Strong Python, plus at least one of Java, C++, TypeScript, Go or Rust.
- Proficiency with Git, Docker and automated testing.
- Ability to read and navigate unfamiliar codebases.
- Fluent written English and clear technical communication.
- Reliable, detail-oriented, and able to work independently and meet deadlines in a remote setting.

Preferred Qualifications
- Open-source contributions or code-review experience.
- Experience with test automation, CI/CD or developer tooling.
- Prior LLM evaluation or data annotation experience.
- Experience with large or distributed codebases.

Legal and Compliance Notice
- All content you submit must be lawful, and you must have the right to share it.
- Do not submit confidential or proprietary material belonging to an employer, client or third party, or personal data without a lawful basis.
- Rex may verify identity, credentials, ownership and licensing; may reject or remove any submission; and may report unlawful submissions to the relevant authorities.
- Engagement and payment are subject to successful verification and to applicable sanctions, export-control, tax and employment laws.
- The contractor agreement will set out ownership and licence terms for the work you deliver (to be confirmed by Rex Legal).