About the Position

AI Researcher - Post-Training

Location: London, United Kingdom

Employment Type: Full-Time, On-site

About the Company

Sonar is at the forefront of agent-centric software development, specializing in AI code verification and governance. We empower companies to build reliable, secure, and maintainable software generated by AI-assisted developers or autonomous agents. Our clients include industry giants like Nvidia, ServiceNow, Booking.com, Goldman Sachs, AstraZeneca, and Ford Motor Company.

Responsibilities

Outcome Driven Development: Collaborate with a team to develop advanced products that enable customers to post-train models for their agentic coding practices.
Translate Prototypes to Products: Work closely with researchers, engineers, and MLOps to design hypotheses, iterate proofs-of-concept, and develop successful prototypes into cutting-edge products.
Subject Matter Expert: Contribute and discuss ideas within our cross-disciplinary team, driving the next generation of coding model post-training for enterprises.
Spearhead Research & Innovation: Stay updated with the latest LLM and agentic developments, and explain complex technical details and concepts to both technical and non-technical audiences.

Requirements

Education: Advanced academic background (Master’s or PhD) in Computer Science, Machine Learning, or a related quantitative field.
Experience: 4+ years of industry experience in machine learning, with a solid understanding of modern software engineering practices and tools.
Technical Skills:
- Fluency with Python and core ML frameworks.
- Expertise in post-training of large language models, including:
  - Policy optimization algorithms (e.g., GRPO, PPO)
  - Verifier-based RL frameworks (RLVR)
  - Supervised fine-tuning (SFT)
  - Data-centric AI methods, including synthetic data and curation
  - Parameter-efficient fine-tuning (PEFT)
  - Preference and Safety Alignment
- Experience with Rust or any of SonarQube’s flagship languages (C#, C++, JS/TS, Java) is a plus.
Communication Skills: Excellent communication skills in English and a talent for explaining complex scientific topics clearly and concisely.

We Offer

In-office Culture: We believe in building the best teams in person. Our in-office culture is intentional, with three anchor days (Mondays, Tuesdays, and Thursdays) to foster collaboration.
Diversity, Equity, and Inclusion: We value and respect different backgrounds, perspectives, and cultures. We are committed to fostering a diverse and inclusive work environment.

Application Process

Candidates need to be genuinely based in the location the role is posted. We are happy to support relocation for the right person.

All offers of employment at Sonar are contingent upon the results of a comprehensive background check and reference verification conducted before the start date.

Applications submitted through agencies or third-party recruiters will not be considered.

We may use artificial intelligence (AI) tools to support parts of the hiring process, such as reviewing applications, analyzing resumes, or assessing responses and identifying potential inconsistencies or verification signals in application materials based on available information. These tools assist our recruitment team but do not replace human judgment. Final hiring decisions are ultimately made by humans.

If you need any accommodation, please reach out to us at [email protected].

For more information about how your data is processed, please contact us.

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AI Researcher - Post-Training

Job description