Member of Technical Staff - Software Engineer

Department: R&D

Location: London Office

Employment Type: FullTime

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 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 expect during our interview process:

1. Introductory Call

2. Take-Home Exercise

3. On-site Technical Session

4. Culture Conversation

5. Leadership Discussion

Throughout the process, if you have any specific requirements or need adjustments, please let us know: we’re happy to accommodate.

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