AI Researcher - Post-Training (f/m/d)

Who is Sonar?

Sonar enables organizations to ship agentic code with confidence. Code creation is abundant, but confidence is scarce. Our core platform, SonarQube, verifies over 750 billion lines of code every day, delivering agentic verification and governance for all code. Trusted by more than 7 million developers and 75% of the Fortune 100, including teams at Nvidia, ServiceNow, Booking.com, Goldman Sachs, AstraZeneca, and Ford Motor Company, Sonar enables organizations to reduce outages, improve security, and lower the cost and risk of agentic software development.

Founded in Geneva and now headquartered in Austin, Texas, Sonar has a global team working across offices and hubs, including Silicon Valley, London, Bochum, Barcelona, Singapore, Tokyo, and the Washington, D.C. area. At Sonar, we’re enabling enterprises to build agentic software factories that can move quickly while maintaining the control, consistency and evidence required to ship with confidence.

Position description

At Sonar, we are seeking an ambitious senior researcher to join our cross-disciplinary team, innovating and developing the next generation of solutions to build enterprise-grade coding agents and models. You will harness Sonar’s deep experience in static analysis, and combine it with your experience and leading techniques in large language model post-training. If you are interested in being hands-on with state-of-the-art research, building practical solutions that deliver high-impact for customers, and working within a team of innovative researchers and engineers, this role is for you.

What you will do

• Outcome Driven Development: Work in a team developing and implementing advanced products that enable customers to post-train models to power their agentic coding practices. These agents need to generate high-quality code that meets their enterprise standards and software development best practices.
• Translate Prototypes to Products: Collaborate closely with researchers, research engineers, MLOps and engineers within the team to design hypotheses and experiments, iterate proofs-of-concept quickly and develop successful prototypes into cutting-edge products.
• Subject Matter Expert: You will contribute and discuss ideas within our cross-disciplinary team, driving towards the next generation of coding model post-training for enterprises.
• Spearhead Research & Innovation: Stay up-to-date with the latest LLM and agentic developments; you are driven by learning and teaching others. You will need to explain complex technical details and concepts to both technical and non-technical audiences.

Experience and qualifications

The ideal candidate will have:

• An advanced academic background (Master’s or PhD) in Computer Science, Machine Learning, or a related quantitative field.
• 4+ years industry experience in machine learning, with a solid understanding of modern software engineering practices and tools.
• Fluency with Python including core ML frameworks, experience with Rust or any of SonarQube’s flagship languages (C#, C++, JS/TS, Java) is a plus.
• 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 of driving research projects, delivering valuable findings and prototypes, and then converting them into products.
• Excellent communication skills in English and a talent for explaining complex scientific topics clearly and concisely.

Additional comments

This role is based in Bochum. We are unable to consider candidates unwilling to be in this location, but we are willing to relocate the right candidate.

In-office culture

We're intentional about this. We believe the best teams are built in the room together. Three anchor days — Mondays, Tuesdays, and Thursdays — create the collaboration rhythm that makes a hub office worth having. Candidates need to be genuinely based in the location the role is posted — if that's not where you are today, we're happy to support relocation for the right person.

We value diversity, equity, and inclusion

At Sonar, we believe that our diversity is our strength. We are a global company that values and respects different backgrounds, perspectives, and cultures. We are committed to fostering a diverse and inclusive work environment where everyone feels valued and empowered to contribute their best. We are proud to be an equal opportunity employer and welcome all qualified applicants, regardless of race, color, religion, gender, gender identity or expression, sexual orientation, national origin, genetics, disability, age, or veteran status. If you need any accommodation, please reach out to us at recruiter contact. 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 that are submitted through agencies or third party recruiters will not be considered.