AI Research Engineer, Post-Training
You’d own Lovable’s post-training, from the data and the training run to a model users can feel.
- London, in the office
- Full time
- Post-training
- 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 posting says this is not an academic research job. Success is a model change that reaches users, measured in days or weeks.”
Who it suits
A good fit
- have run post-training at scale, including fine-tuning or preference optimization
- Like the training systems as much as the training recipe
- Want a model change to show up in the product quickly
Think twice
- Want an academic research job
- Haven’t run a post-training job
- don’t want to work from the London office
What you’d do
- You own post-training, from data curation and training runs through evaluation and deployment.
- You adapt reinforcement learning, preference optimization, and supervised fine-tuning for code generation and agents.
- You build the evaluation that shows whether a model change helps users, including helpfulness, safety, latency, and reliability.
- You run the production systems for training jobs, including GPU orchestration and data flows.
What they ask for
- You have done post-training at scale.
- You can run training jobs in production rather than only writing the recipe.
- You’ll work in the London office. Applications are in English.
How it works
- The job is on-site in London. The posting does not list pay.
What to know about this job
Open at least 19 weeks. Half of London AI engineer jobs have closed by week 9.
- Week 9Half of London AI engineer jobs have closed
- Week 19This job has been open this long
In November 2026, Lovable had 1 AI research engineer job open, in London.
The model builder, 23% of London AI engineer jobs
- 46%The product builder. 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 (this job). You run post-training for code generation and agents, and a change has to reach users.
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.
Lovable 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?”
- “Which post-training methods are already in use, and which would you introduce?”
Jack’s take on Lovable
- Revenue grew from $100M to $600M a year in 14 months
- Valuation rose from $1.8B to $13.3B in 13 months
- The team grew from 146 to 300 people in 5 months
- Its two cofounders run it, with leaders hired from Gusto, Notion and Meta
- A fast, in-person place to work
- Based in Stockholm, London, New York, Boston and San Francisco
- Founded 2023
- 79 open jobs
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Other open jobs at in-demand startups.
About this page
Jack & Jill isn’t Lovable’s recruiter. We summarized this job from Lovable’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 Lovable’s page. We last checked this summary against the posting on November 9, 2026. Jack’s take is Jack & Jill’s own.