Senior Software Engineer - London

Hcompany; Greater London; Hybrid; GBP 85,000 - 125,000; Full time

Job summary

Hcompany is seeking a seasoned backend engineer to design and operate an evaluation framework for benchmarks across web apps, desktop, and CLI. You will own integration, testing tooling, and observability to ensure fast, reliable runs.

Join a team that scales benchmarks from dozens to hundreds, with hybrid London work options and collaboration with researchers, engineers, and customers to improve model evaluation and release decisions.

Qualifications

• 5+ years of backend development with production Python at the core.
• Experience building test, QA or evaluation tooling.
• Operated distributed systems on Kubernetes in a public cloud (AWS helpful).
• Built and shipped end-to-end systems including APIs (REST/GraphQL) and external integrations.
• Knowledge of relational and non-relational databases and message queues (SQS, RabbitMQ, Kafka).
• Instrument systems with metrics, tracing and monitoring from the start.

Responsibilities

• Integrate benchmarks into the evaluation framework with a streamlined path for researchers and engineers.
• Set the standard for how a benchmark enters the framework and enforce it with checks.
• Schedule and monitor evaluation jobs to optimize cluster capacity.
• Ensure reproducible results across trials to support release decisions.
• Collaborate with researchers and customers to understand measurement needs and automate data flow.

Skills

Backend development

Python

Distributed systems

APIs

Tools

Docker

Kubernetes

Temporal

Dask

PostgreSQL

Grafana

Datadog

Job description

About H:

When we released Holo4 on 28 September, we published every trajectory behind its public benchmark scores at trajectories.hcompany.ai. For OSWorld that's 369 desktop tasks, each run 3 times, with the steps, tokens and time of every attempt. This role builds and runs the evaluation framework that produces runs like these.

H builds computer-use agents and the models behind them. Developers use them through a managed API, and our forward deployed engineers take them into enterprise workflows.

What this team owns

The evaluation framework: orchestration, runtimes and observability. Researchers and forward deployed engineers bring the benchmarks, across web apps, desktop applications and the command line. Your job is to make the framework that runs them reliable, fast and cheap, and to make adding a new one quick. Research uses the results to choose checkpoints and decide whether a model ships. Product and the forward deployed engineers use them to measure agents on customer workflows. It carries roughly 50 benchmarks now. That number should be between 100 and 200 soon, and the framework has to keep up.

What you'd be doing

• Integration support for researchers and forward deployed engineers bringing in a benchmark, with a shorter path each time.
• Setting the standard for how a benchmark enters the framework, and building the checks that enforce it.
• Scheduling and observability, so cluster capacity isn't left idle while evaluation jobs queue.
• Reproducible results across trials, so a release decision rests on numbers that hold.
• Whatever stack a benchmark calls for. One week that's cluster tuning; the next it's a browser extension or desktop environments.
• Time with customers, from single developers to large companies, to find out what they want measured, then automating it so the results flow back into our harnesses and models.

The first few months

By 3 months you'll have helped researchers or forward deployed engineers integrate 5 benchmarks, and started fixing what slows the framework down. By 6 months one part of it is yours, for example scaling the runs, observability, or a group of related benchmarks, and a release will have gone out on your numbers. By 12 months you'll know the design and trade-offs of the whole evaluation system, and be the person the rest of H asks about evaluations.

Who you'd work with

Ceiran Chapman, our VP Engineering, is hiring for this role. You'd join the evaluation team. The people relying on your work day to day are H's researchers and forward deployed engineers.

What we think it takes

Likely a good fit if you

• Have spent 5+ years in backend development, with production Python at the core, and use coding agents to go faster without letting quality drop.
• Have built test, QA or evaluation tooling that other teams depended on, and care whether a number is right.
• Have operated distributed systems on Kubernetes in a public cloud. AWS experience helps most.
• Have built and shipped systems end to end, including APIs (REST or GraphQL) and integrations with outside services.
• Know relational and non-relational databases, and message queues such as SQS, RabbitMQ or Kafka.
• Instrument what you build, with metrics, tracing and monitoring from the start.

Stronger still if you have

• Measured LLM quality before, or built agents yourself.
• Packaged and run workloads in Docker and on virtual machines.
• Used Temporal, Dask, FastAPI, PostgreSQL, Grafana or Datadog.
• Automated web or desktop software with Playwright, Selenium or a browser extension you wrote.
• Set standards other engineers follow, through code review, design review or mentoring.

You do not need a background in machine learning. We'll work that out with you.

How we hire

A 30 minute call with our Talent team, a 60 minute technical challenge, a 60 minute system design interview, and a 30 minute final conversation with Ceiran. About 3.5 hours in total.

Practicalities

London posting: Hybrid in London. That means 3 office days a week and a Paris trip about once every 4 to 6 weeks. There is a Paris posting for the same role. We offer a competitive package.

Find more English Speaking Jobs in United Kingdom on Arbeitnow