Staff AI Engineer: RL, Agents & Long-Horizon Tasks

Stealth - AI x Bio; Greater London; In loco; GBP 120.000 - 180.000; Tempo pieno

Vantaggi offerti da questo lavoro

30 days annual leave

Private health cover (UK)

Pension / UK

Descrizione del lavoro

Stealth - AI x Bio is hiring a role focused on teaching our agents to learn through reinforcement learning. You will design harnesses and long-horizon tasks, train LLMs with RL, and build robust evaluation methods, often bridging biology and AI teams in London or San Francisco.

You will work with scientists and engineers to ensure careful reward design, detect reward hacking, and advance agent capabilities using Python and PyTorch in a collaborative, open development environment.

Competenze

• Hands-on experience training LLMs with reinforcement learning, using methods such as PPO or GRPO, including reward design and detecting reward hacking.
• Experience with RL training frameworks such as veRL, Miles or TRL, RL environment frameworks such as Harbor or Prime Intellect's verifiers, and inference engines such as vLLM or SGLang.
• Building agent harnesses and long-horizon tasks with tool use, such as search, code execution and external APIs.
• Designing learning signals for long trajectories, including verifiers, LLM judges, process reward models and credit assignment across steps.
• Rigorous comparisons, with matched compute, repeated runs, noise estimates, ablations and held-out problems.
• Clear writing and communication about experiment design, results and what they do and do not show.
• Strong Python and PyTorch, and daily use of coding agents.

Mansioni

• Own how our agents learn, including harnesses and RL environments.
• Design and implement tasks, rewards, and evaluations for long-horizon agent learning.
• Collaborate with Bio ML researchers, evaluation and infrastructure engineers, software engineers and scientists.
• Assess when improvements come from models vs. harness/tools/tests.

Conoscenze

LLM training with RL

PPO/GRPO reward design

RL frameworks (veRL, Miles, TRL)

Python

PyTorch

Agent harnesses and long-horizon tasks

Tool use: search, code execution, APIs

Experiment design and evaluation

Communication of results

Strumenti

veRL

Miles

TRL

Harbor

Verifiers

vLLM

SGLang

Descrizione del lavoro

Stealth - AI x Bio is hiring a role focused on teaching our agents to learn through reinforcement learning. You will design harnesses and long-horizon tasks, train LLMs with RL, and build robust evaluation methods, often bridging biology and AI teams in London or San Francisco.

You will work with scientists and engineers to ensure careful reward design, detect reward hacking, and advance agent capabilities using Python and PyTorch in a collaborative, open development environment.