Tessl AI, London Office
In your first 3 months, you might have shipped a new eval suite for a real customer workflow, improved an agent harness based on trace analysis, or built a pipeline that turns production failures into reusable test cases.
We're explicitly building coverage across four skill areas. You don't need to be strong in all of them — but you should bring depth in at least one:
We're hiring a Research Engineer to join our AI Research (AIR) team. You'll work on the components that make the outer loop real: how agent harnesses orchestrate model behaviour, how we evaluate what's actually working, how pipelines turn production traces into the next round of improvement, and how we diagnose the failure modes that matter to real users.
These aren't four separate workstreams – they're parts of one system, and we want people who see them that way.
We expect you to sit close to customers – joining calls, watching sessions, reading traces — and to let real workflows shape your research priorities. You'll have meaningful autonomy and the resources to run substantial experiments where the bar for success is shipped impact.
You'll report to our AI Research Lead, and collaborate closely with engineering, product, and design.
We want Tessl to be a place where you can do meaningful work, keep learning and enjoy being part of the team. Alongside competitive compensation, we offer benefits designed to support you both inside and outside work.
Our office is in the heart of King's Cross, surrounded by London's growing AI and technology community.
We work together in person on Mondays, Tuesdays and Thursdays, giving us time to collaborate, exchange ideas and build relationships. You'll also enjoy catered lunches (Tuesday & Thursday), plenty of office snacks, regular team lunches and socials, plus a pet-friendly workplace.
AI isn't just what we're building – it's central to how we work every day, across every function. We actively use AI to improve how we work, solve problems and challenge traditional ways of doing things.
You don't need to be an AI expert to thrive at Tessl, but you do need curiosity, an appetite for experimentation and a willingness to embrace new ways of working. We expect everyone to use AI regularly, invest time in learning how to get the most from it and keep experimenting when something doesn't work the first time, rather than defaulting to manual approaches.
We're also big believers in sharing what we learn. We encourage transparency about how we're using AI, what's working, what isn't and how we can help each other improve. Being AI native doesn't mean removing human judgement, it means using AI thoughtfully, while taking ownership of the quality and outcomes of our work.
We're committed to building an inclusive environment where people from different backgrounds, experiences and perspectives can thrive.
We particularly welcome applications from people who are underrepresented in technology. If you're excited about the opportunity but don't meet every requirement, we'd still encourage you to apply.
If you need any adjustments or additional support during the recruitment process, please let us know. We're happy to work with you to make the process accessible and comfortable.
We're moving fast, experimenting boldly and figuring things out as we go. There's plenty to build, lots to learn and real opportunities to make your mark.
If you're excited by big ideas, enjoy getting stuck in and want to be part of something from the ground up, we'd love to hear from you!
AI is transforming how software is built, and at Tessl, we're building the infrastructure for what comes next.
We're developing a platform that enables engineering teams to build and run AI-powered software factories, where coding agents take on real development work, from picking up engineering tickets to implementing changes and creating pull requests.
By combining structured context, reusable agent skills, automated workflows and evaluations, we're making AI-powered development more reliable, repeatable and scalable, while keeping humans in control. We're tackling some of the biggest challenges in autonomous software development, from code quality and security to helping organisations confidently adopt AI agents at scale.
Founded by Guy Podjarny, previously founder of Snyk, Tessl is a fast-growing Series A startup backed by over $100 million in funding from investors including Index Ventures, Accel, GV and Boldstart.
Joining Tessl means helping define an entirely new category of technology, solving ambitious technical challenges and shaping the future of software development.
Our operating principles shape how we collaborate and make decisions. We move quickly and learn by doing, build on ideas before challenging them, get stuck in wherever we can help, and give people real ownership. We encourage thoughtful debate, curiosity and a willingness to try things that haven't been done before. Read our five operating principles https://tessl.io/careers.
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