Member of Technical Staff - AI Engineer

Tessl is a fast-growing Series A startup based in London, founded by Guy Podjarny. We’ve raised over $100M from world-class investors including Index Ventures, Accel, GV, and Boldstart, and in 2025 we were ranked #2 in Sifted EU’s B2B SaaS Rising 100 and #20 in Sifted's AI 100.

At Tessl, we are building the context layer for AI coding agents, and a platform for AI-native software development. As an early member of the team, you’ll help shape how we build, scale and support a company operating at the edge of AI and software development.

Overview of role

Join our AI Engineering team to explore the boundaries of LLMs and AI, shaping Tessl's direction and transforming the developer experience. You’ll be expected to be a versatile and entreprenurial Software Engineer who loves code and can make things work, using your skills both to build software in the team and to opine as a subject matter expert on how our AI generates code. You’ll collaborate closely with our wider engineering team as well as product and design. We have the resources to afford large experiments and push the state of the art, and our team has a wealth of experience in delivering tools for developers that work at scale.

What we’re looking for

We’re looking for someone who is as excited as we are to be part of a dynamic team that is shaping the future of AI and software development.

Essential

• 4+ years of experience as a Software Engineer. You care about code efficiency and quality and have firsthand experience in how software is built across teams and environments
• Equally comfortable contributing to a mature codebase with strict CI criteria or hacking up a quick notebook to prove/disprove something.
• Proven experience collaborating with researchers and bridging between research-focused and engineering-focused teams.
• Experience with the applied use of data and statistics, likely to spot and avoid bad data when you see it.
• Deeply curious about AI and excited about its potential to transform software engineering.
  
  

Nice to have

• Education or experience in ML/AI, ideally using unstructured data.
• Experience in rapid prototyping environments; Office of CTO, DevRel, etc.
• Programming polyglot experienced in several languages of different paradigms (e.g.: Java, JavaScript/TypeScript, Python, C or C++, Haskell or other functional).
• Have a cool project to show us (GitHub links welcome!) and a well articulated answer to the question “Why Tessl?”
  
  

What you’ll do

• Use a bit of jq and grep to quickly navigate a dataset, but recognise when it’s time to use a more robust approach and move the team to something like dbt or duckdb.
• Tune a prompt in our generation workflow, eval the results and write an experiment report on your findings. Leave the eval tooling better than when you found it.
• Rapidly prototype a new language integration for our code generation pipeline, then develop a plan for a scalable implementation.
• Factor out a piece of our pipeline to use FaaS, unlocking 1,000x larger evals to run in nearly constant time.
• Add support for a new model in our elegant model abstraction library, or rewrite it when new model capabilities prove our existing design wrong.
• Work with our platform team on the next generation of eval facilities, based on your understanding of what researchers need and where the platform is heading.
  
  

Salary and benefits

Office: Our brand new 10,000 sq. ft office is in the AI hub of Kings Cross, London. We have generous catering and have regular social events such as team lunches, drinks and more. We require all staff to be in our London HQ at least 3 days a week on our anchor days of Monday, Tuesday and Thursday.

Salary: We offer a competitive salary based on experience and skills, benchmarked against industry standards.

Benefits: 25 days holiday, health insurance, including dental and vision, which extends to partners and dependents, as well as a company-matched pension. We also provide a commuting stipend for those who live outside London, and a cycle to work scheme.

Application Process

Here’s an outline of what you can expect during our interview process:

• Introductory Call
• Take-Home Exercise
• On-site Technical Session
• Culture Conversation
• Leadership Discussion
  
  

We care deeply about the warm, inclusive environment we’re building at Tessl and we value diversity – we welcome applications from those typically underrepresented in tech. If you like the sound of this role but are not totally sure whether you’re the right person, do apply anyway!

Learn how we think and work

• On Tessl, The AI Native Development Startup
• Announcing skills on Tessl: the package manager for agent skills
• Podcast Episode: The End of Fragmented Agent Context, Guy Podjarny Tessl CEO