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).

Where you can work

This role is 100% remote: you can work from anywhere in the world.