Job Specifications
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 June 2025 we were ranked #2 in Sifted EU’s 2025 B2B SaaS Rising 100.
In September 2025, we launched our first products - the Tessl Framework and Tessl Spec Registry - which integrate with any agent to keep it on rails and well-informed through Spec-Driven Development.
At Tessl, we believe AI is transforming software development. AI Native Developers will define features, architecture, and workflows in specs, not code, guiding the work of AI agents. We’re building the pioneering platform for this new paradigm and leading the developer movement and ecosystem around it.
Joining Tessl means becoming an early team member with the opportunity to shape the future of how software is created and maintained. To learn more about our vision, visit ainativedev.io, our developer community and go-to resource for navigating the AI-driven software era.
Overview of role
Join our engineering team to build real-time AI Native workflows, tooling, and interfaces that will reshape how developers create and maintain software.
As a Software Engineer, you’ll be versatile and independent, excited to work with cutting-edge AI tools to build great products. We move quickly, but with purpose - balancing speed with collaboration and thoughtful execution. You’ll collaborate closely with product, design, and the wider Engineering team to bring AI Native development to life in a fast-paced, high-trust environment.
What you’ll do
No two days will be the same at Tessl! You’ll have a high level of autonomy and be able to make decisions based on what you believe will help you deliver the most success. Here’s an insight into just a few of the things you would be doing:
Design and implement new functionality that you discussed and reviewed with the product team
Spin up a proof of concept to showcase an innovative idea you’ve been thinking about
Rapidly prototype a new language integration for our code generation pipeline, then develop a plan for a scalable implementation.
Pair with a designer to fine-tune interactions in the UI, CLI or existing AI coding agents, making the user experience more intuitive and slick
Integrate a third-party service, e.g. for notifications, so we can focus our own cycles on Tessl’s core capabilities
Collaborate with other teams to plan an architecture that supports collaboration across the platform
Establish an end-to-end testing strategy to increase our confidence when deploying new features to production
Share your technical vision for a new product capability you’ll be leading with the wider engineering team for feedback and alignment
What we’re looking for
Essential
Proven experience (typically 5+ years or equivalent) as a Software Engineer. You care about code modularity, structure and aesthetics 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 prototype to prove/disprove an assumption
Proven experience leveraging the best AI coding tools and agents to accelerate and enhance your own work and efficiency
Comfortable with fast-paced, high-autonomy environments: you’ve ideally thrived in an early-stage startup before
You have demonstrated usage of AI tools in your day-to-day work, and be excited about experimenting, learning, and harnessing the potential of new AI tools and approaches to transform software engineering
Nice to have
Background in AI products or developer tools
Experience in rapid prototyping environments
Programming polyglot experienced in several languages of different paradigms (e.g.: JavaScript/TypeScript, Python, C or C++, Haskell, etc.)
Experience collaborating with AI researchers and bridging between research-focused and engineering-focused teams
Experience building & scaling REST APIs, particularly those conforming to JSON:API
Comfortable working on infrastructure (e.g., setting up CI pipelines, navigating Kubernetes)
If you have a personal or open-source project you’d like to share, we’d love to see it (GitHub links welcome!)
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 exp