Founding AI Engineer

Founding AI Engineer Kantrip - London (Bloomsbury) - On-site, 5 days - Full-time - £100,000-£150,000 + founding equity About Kantrip We're building a platform where agents build native mobile games. Not web toys, real games that ship to the App Store and Play Store. There are plenty of browser-based competitors and none of them build games at the quality or scale that mobile needs. We're small. The founder plus two engineers, building towards our first launch. The role You own the agent system that turns a game spec into a shipped game, along with the evals, the model routing and the runtime underneath it. We have a working system and we know it can be much better. Off-the-shelf agent infrastructure doesn't cut it here. Games need specific loops, specific context, and the economics matter when every run costs real money. Model releases lift everyone equally. You'll be building the system that turns those models into games people actually want to play. What you'll do

• Design, build and operate the pipeline that takes a game from spec to shipped build: planning, code generation, review and release
• Build evaluation and regression tooling that measures output quality and catches failures automatically
• Build the routing layer that picks a model for each pipeline step based on quality, latency and cost
• Replace third-party agent infrastructure with our own runtime where it improves quality, control or cost
• Build our retrieval and context systems, and lead fine-tuning on the data the platform generates What we're looking for
• You've built LLM systems in production: multi-step pipelines, tool-using agents, or eval infrastructure
• You've designed and run evals: test sets, benchmarks, regression tracking
• You've managed inference cost alongside quality and latency in a production system
• Strong systems engineering background. We work in TypeScript, deep experience in another language is fine
• You follow the field closely and test new models and techniques as they land
• Based in London and happy to work in person, five days a week The thing we care about most: you've built agents whose output had to run. Code, builds, tests, deployments. Something that either worked or broke, not text a person reads and judges. Nice to have
• Model routing or gateway infrastructure
• Fine-tuning, post-training, or retrieval systems
• A background in games How we hire Short, paid, and you know the bar at every stage. Two weeks end to end. 30-minute intro call 60-minute technical walkthrough of the best thing you've built, your code, your screen Paid exercise, £250, two to four hours in your own time. AI tools allowed and expected. Pass criteria stated upfront, followed by a 30-minute debrief Coffee in person, plus references Details £100,000-£150,000 depending on experience, plus founding equity through our EMI scheme. In person five days a week from our office in Bloomsbury. No visa sponsorship for this role.
• Apply at kantrip.dev/careers/founding-ai-engineer or email careers@kantrip.dev