ML Research Engineer – Member of Technical Staff

About the role

Callosum is building an orchestration layer that co‑evolves models, workflows and silicon. As an ML Research Engineer you will advance the science behind agentic systems, turning experimental insights into scalable, cost‑effective AI infrastructure.

Key responsibilities

• Design and run experiments that isolate why agentic systems fail, then turn findings into interventions that improve intelligence, cost and reliability.
• Attack core research themes such as context and memory management, agent steering, task decomposition, continual learning, and inter‑agent communication.
• Build durable agent analysis and evaluation infrastructure – observability, behaviour analysis, evaluation harnesses and auditing tools.
• Publish evaluation results, methods and discoveries as both internal assets and public evidence.
• Collaborate across teams to scale domain‑specific applications and invent novel model/agent architectures that exploit emerging silicon.

Required profile

• Demonstrated ability to conduct independent research, formulate hypotheses, run controlled experiments and produce reproducible results.
• Deep hands‑on experience with large language models in agentic settings (multi‑step tasks, tool use, long horizons).
• Rigorous experimental discipline with clear hypotheses, ablations and honest uncertainty quantification.
• Strong engineering skills to write production‑grade code within a shared codebase.
• Excellent communication to translate research findings into actionable guidance for engineering teams.

Required skills

• Experience building evaluations, benchmarks or agent harnesses adopted by others.
• Reinforcement learning for long‑horizon, multi‑step or tool‑use tasks.
• Expertise in multi‑agent systems, planning, program synthesis or structured retrieval.
• Familiarity with inference serving frameworks such as SGLang, vLLM or comparable systems.

What we offer

• Competitive salary determined by skills and experience.
• Equity & ownership.
• Private healthcare.
• Visa sponsorship and relocation benefits.
• On‑site work in our London office with inclusive workplace culture.