Principal Engineer, Fin AI Agent in London

Fin is the AI Customer Agent company on a mission to help businesses provide perfect customer experiences. Our AI Agent Fin is the highest-performing AI Customer Agent on the market today, enabling businesses to deliver impeccable, always-on customer support across the customer journey – from service, to sales, to ecommerce. Powered by our own AI models, Fin resolves complex customer issues end-to-end across every channel, with minimal set-up and integration.

Founded in 2011, Fin became one of the fastest growing companies and remains one of the largest private software companies in the world with nearly 30,000 global businesses using our products to transform their customer support. Driven by our core values, we push boundaries, build with speed and intensity, and relentlessly deliver incredible value to our customers.

What’s the opportunity? Fin is the #1 AI agent for customer service. It resolves over 1M customer conversations every week, and we're just getting started. We're on the cutting edge of defining how AI agents should work — inventing paradigms that didn't exist six months ago and discovering entirely new problem spaces every time we push the technology further. This role sits at the heart of the Service Agent pillar — 12 teams and growing, building every capability that makes Fin work.

You’ll partner at the strategic pillar level: broad context across work streams, deep technical understanding of how Fin operates end-to-end, and the autonomy to decide where you need to go next. When we need a new work stream spun up from scratch — a brand new team, an ambiguous problem space, aggressive timelines — you're the person who makes that happen.

The competitive landscape is intense. Fast-moving AI-native startups are coming hard for this space, shipping aggressively and going after the same deals we are. We need someone who thrives under that pressure, who can maintain technical excellence while moving at startup speed within a company that has the resources and customer base to make that speed count.

What will you do?

• Partner at the strategic pillar level. You'll have broad context across work streams and use that to inform technical strategy and investment priorities.
• Spin up 0-to-1 work streams. Bring together engineers who've never worked as a team, disambiguate the problem space, build momentum under aggressive timelines, set high expectations, and drive execution.
• Execute on the most ambiguous, highest-stakes problems. You're hands-on. You write code, you ship features, you're deep in the weeds.
• Lead experimental work at the AI frontier. Run your own A/B tests, do prompt engineering, build evals, and calibrate accuracy, cost, and latency for LLM-powered features.
• Shape long-term technical strategy through execution. Your hands-on work informs the architecture.
• Work across the full stack in an AI-first development environment.
• Raise the bar for the people around you. Give direct, actionable feedback that changes outcomes.

What are we looking for?

• The core requirement: engineering depth and product thinking.
• Operated at real scale and has builder energy.
• AI fluency.
• Deep technical depth with breadth.
• Communication as a superpower.
• Extreme autonomy.
• Critical thinking about the business.
• At least ~10+ years of experience, with significant time as a technical leader driving complex projects across multiple teams and stakeholders.
• Stack agnostic.

Why Fin, why now? Fin is #1 — and the race is heating up. We built the leading AI agent for customer service, but fast-moving AI-native startups are coming for this space. This is one of the most consequential competitive moments in tech history, and the engineering decisions made in the next 12 months will determine who wins.

A rare pivot that actually worked. Fin has been building for 15 years — deep product, massive customer base, strong revenue. But unlike most legacy SaaS companies, we made a successful pivot to AI. While most of SaaS trends down, Fin trends up. We recently raised $250M to go even further even faster.

AI-first engineering culture. Every engineer gets Claude Code with unlimited Opus 4.6 tokens and 1M context. We're investing heavily in the platform capabilities — MCP servers, skills, shared tooling — that make AI-assisted development genuinely transformative.

The sweet spot. Big enough to have real resources, customers, and revenue. Small enough that you have genuine agency. Bold enough to make decisions that most companies of this size wouldn't. You come to Fin if you want the impact of a startup with the backing of a company that's been winning for 15 years.

Benefits

• Competitive salary and equity in a fast-growing start-up.
• We serve lunch every weekday, plus a variety of snack foods and a fully stocked kitchen.
• Regular compensation reviews - we reward great work!
• Pension scheme & match up to 4%.
• Peace of mind with life assurance, as well as comprehensive health and dental insurance for you and your dependents.
• Flexible paid time off policy.
• Paid maternity leave, as well as 6 weeks paternity leave for fathers.
• Cycle-to-Work Scheme with secure bike storage.
• MacBooks are our standard, but we also offer Windows for certain roles when needed.

#LI-Hybrid Policies

Fin has a hybrid working policy. We believe that working in person helps us stay connected, collaborate easier and create a great culture while still providing flexibility to work from home. We expect employees to be in the office at least three days per week.

We have a radically open and accepting culture at Fin. We avoid spending time on divisive subjects to foster a safe and cohesive work environment for everyone. As an organization, our policy is to not advocate on behalf of the company or our employees on any social or political topics out of our internal or external communications.

Fin values diversity and is committed to a policy of Equal Employment Opportunity. Fin will not discriminate against an applicant or employee on the basis of race, color, religion, creed, national origin, ancestry, sex, gender, age, physical or mental disability, veteran or military status, genetic information, sexual orientation, gender identity, gender expression, marital status, or any other legally recognized protected basis under federal, state, or local law.