Member of Technical Staff- Research Engineer (Harness Engineering and Agentic Orchestration)

At Tessl, we are building the context layer for AI coding agents, and a platform for AI-native software development. We're hiring a Research Engineer to join our AI Research (AIR) team. You'll work on the components that make the outer loop real: how agent harnesses orchestrate model behaviour, how we evaluate what's actually working, how pipelines turn production traces into the next round of improvement, and how we diagnose the failure modes that matter to real users. We expect you to sit close to customers — joining calls, watching sessions, reading traces — and to let real workflows shape your research priorities. You'll report to our AI Research Lead, and collaborate closely with engineering, product, and design.

Responsibilities

Sit in on a customer session, understand how their agents are failing, design an eval that captures it, and drive a fix through to shipped improvement; Close a piece of the outer loop end to end: production signal in, dataset out, eval scored, harness change shipped, metric moved; Own a slice of our eval infrastructure: dataset curation, harness configuration, runner, analysis, and the comms back to engineering; Prototype a new harness or context configuration and measure whether it actually moves the needle on real customer tasks; Dig through pages of agent traces, build the tooling you need to make sense of them, and brief the team on what you found; Partner with product and engineering on near-term shipping problems by bringing research rigour; Pull a recent paper apart, work out what's actually transferable to our platform, and turn it into a concrete experiment; Report to the AI Research Lead and collaborate closely with engineering, product, and design

Requirements

4+ years shipping AI/ML products in a startup or applied industry setting, with recent hands-on experience with LLMs and agentic systems; Demonstrated depth in at least one of the four skill areas: Agent harness and orchestration design, Agentic eval methodology, Outer-loop and pipeline thinking, Failure-mode analysis; Strong product and customer instincts: comfort joining customer calls, watching session recordings, and letting real workflows shape what you work on; Sharp evaluation judgement: benchmarks where they exist, vibes and quick prototypes where they don't, and the taste to know which is appropriate; Experience building datasets for evaluation or training, including the pipeline work that goes with it; Deeply curious about agents and excited about reshaping how software is built

Nice to have

A Masters or PhD in a relevant computational field; Direct experience with coding agents or code-generation systems; Background in RL, bandits, or other outer-loop optimisation frameworks applied to LLMs; Experience building synthetic data, dataset infrastructure, or internal tooling that other engineers actually used; A project you can show us (GitHub links welcome) and a thoughtful answer to "Why Tessl?"

Benefits

Health insurance extending to partners and dependents; Pension contributions; Pet friendly office near King's Cross; Regular team lunches, drinks, and socials; Hybrid working with Monday, Tuesday, and Thursday as primary in-office days