Senior applied AI engineer
You’d own parts of Xapien’s due diligence report, from research agents and entity resolution through the version a customer uses. Recurring revenue grew more than 350% in two years.
- London, hybrid
- Full time
- Includes equity
- Pay not listed
This job is open.
Jack works for you and is free. Hiring companies pay us.
Jack’s take. Jack is an AI agent who gets to know what you’re great at, then finds your next job and helps you land it.
“The team uses Claude Code by default and rarely writes code by hand. The craft is prompting, evals, and catching a wrong answer.”
Who it suits
A good fit
- have shipped a language-model system a customer paid for
- have handled an incident in a production language-model system, and designed it so a bad answer fails safely
- want a small team where you help decide what gets built
Think twice
- haven’t shipped a language-model system
- want a large team
- don’t want a hybrid week in London
What you’d do
- Build for accuracy, speed, and cost.
- Design evals that show whether a change helped.
- Own part of the due diligence report from scoping through the version a customer uses.
- Trace a wrong answer and fix the retrieval, prompt, or agent that caused it.
What they ask for
- You have shipped a production language-model system a customer paid for, such as retrieval, prompting, or agents.
- You are fluent in Claude Code, Codex, or a similar coding agent.
- You can decide with incomplete information.
How it works
- The job is hybrid in London. The posting lists employee equity, private health insurance, life insurance, unlimited time off, and £1,000 a year for learning. It doesn’t list pay.
What to know about this job
Open at least 13 weeks. Half of London AI engineer jobs have closed by week 9.
- Week 9Half of London AI engineer jobs have closed
- Week 13This job has been open this long
In November 2026, Xapien had 8 jobs open, 5 in London and 3 in Boston. This was the only applied AI engineer job.
The product builder, the most common kind of AI engineer in London
- 46%The product builder (this job). Builds product features on large language models, from agents to search, and checks the answers hold up.
- 25%The platform builder. Builds the systems that train, serve and monitor models so they run fast and reliably at scale.
- 23%The model builder. Trains and fine-tunes their own models, such as recommendations, vision or fraud, and ships them into the product.
Shares of open AI engineer jobs in London.
Most new London AI engineers weren’t AI engineers before
- 71% of people who became AI engineers in London weren’t AI engineers in their last job.
- 47% of them came from a startup or scale-up.
Xapien doesn’t list pay for this job
The London AI engineer guide shows what AI engineers in London expect to earn.
What London AI engineers earnWorth asking the hiring team
- “How many days a week is the London office?”
- “How much of the week is prompting and evals, and how much is entity resolution and report generation?”
Jack’s take on Xapien
- Recurring revenue grew more than 350% in two years
- Spectrum Equity led its $56M Series B in September 2026
- Its UK team tripled from 20 to 63 people in three years
- Its two cofounders and its CEO all worked at BAE Systems
- Its small team works hybrid, and every employee has a stake in the company
- Based in London and Boston
- Founded 2018
- 8 open jobs
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About this page
Jack & Jill isn’t Xapien’s recruiter. We summarized this job from Xapien’s public careers page, where you can apply. We check whether it’s still open each time you open this page. The market numbers come from our London AI engineer guide and the company facts from Xapien’s page. We last checked this summary against the posting on November 9, 2026. Jack’s take is Jack & Jill’s own.