Senior Engineer - Agents

About Buildkite Buildkite's CI platform is trusted by the world's leading engineering teams, helping ship software used by more than 1 billion people every day. Companies including Canva, Meta, Mistral AI, and NVIDIA rely on Buildkite to run builds, tests, and deployments on their infrastructure, ours, or both — giving them the speed, reliability, and flexibility to ship with confidence. About the Role Somewhere right now, an engineer has pushed a change and is watching a build run. What's doing that work is the Buildkite Agent — and that's what this team looks after. It’s the open-source agent that engineers around the world have running on their own machines, in their own clouds, in Buildkite’s own hosted agents, anywhere and everywhere Buildkite’s CI runs. It's a critical repo to own. The team sits at an exciting intersection — deeply technical infrastructure work on one side, the fast-moving world of AI agents on the other, and our own agent sandwiched in the middle. It's the piece everything else leans on, so the details count. The people relying on you are your fellow engineers shipping their own features. The systems you'll look after can't be paused or casually restarted. We need to constantly iterate and update. That's the nature of it, and it's most of what makes it interesting. You'll have work you can point at and be proud of, and a sharp, opinionated team who'll happily spend an afternoon in a hard problem with you. A few months in, we'd expect you to be fully owning something that matters. What You'll Do Ship • Break big problems into small things that go to production this week, rather than perfect things that go to production in eight months. • Own features end-to-end — from the idea, through the trade-offs, to the rollout, to what happens when it misbehaves in production. • Design for a world where things fail partially and constantly: careful rollouts, migrations you can reverse, and observability you'd actually want during an incident. Own • Take a problem and get obsessive about it. Dig as deep as it takes. Come back with an answer and a plan. • Rotate through Sweep — two weeks in every eight, protecting the team's project time by fielding what comes in, working with Support and Solutions Engineers, and getting people answers fast. It's the quick-hit, high-endorphin end of the job. • Bring ideas to the roadmap, not just execution against it. If it's more valuable than what's already planned, we'll swap it in. • Handle incidents and put out problem embers before they become problematic fires. Communicate • Explain what you're doing, what you found, and what you're worried about — clearly, in writing and out loud, to engineers and non-engineers alike. • Pair, review, and give feedback that makes the code and the person better. • Use AI tooling like a power tool, not autopilot: throw an agent at the problem, then verify what comes back. This Is You If... • You'd rather show us than tell us. You can point at things you've built, things you've changed, and things you've owned — and talk about them in the first person. • You ship small and often. Your instinct when facing an eight-month problem is to find the quick prototype and get it in front of people. • You get obsessive. When something's broken or slow or ugly, you can't leave it alone. You go find out why. • You do it anyway. You're comfortable saying "I hadn't done this before and it was uncomfortable, but I worked out how". And "that's not my job" isn't in your vocabulary. • You're a strong communicator. You keep people around you informed without being asked. You're comfortable having an opinion in a room full of people who also have opinions. • You have real production ownership behind you. Not "I was on the team" but, "I was responsible, and here's what broke and what I changed." • You are highly proficient with Go, or Ruby, and you're not precious about either. Go is our primary language across the agent and infrastructure. Ruby on Rails is the backbone of the platform. You'll need genuine experience in at least one — and the comfort to move between languages as the tooling landscape shifts underneath all of us. Bonus Points for experience with; • Kubernetes & AWS — we run cloud-native infrastructure at scale. • Terraform — we manage infrastructure as code and value reusable, maintainable modules. • PostgreSQL — query optimisation, schema design, or running relational databases under load. • React & GraphQL — our frontend and API layer. • You've worked on developer tooling, CI/CD, or anything where your users are engineers with strong opinions. • You've written publicly about a problem you chased down — a post-mortem, a deep dive, a "why is this slow" investigation. When You Apply — Come With a Story This conversation will come up early, so maybe be prepared for it: Tell us about something you built and shipped quickly. Not the biggest thing you've ever worked on, but maybe the one where you broke a problem down, made a call, and got something small and useful into production faster than anyone expected. What did you skip? What did you get wrong? What happened next? That conversation is the heart of our process. It's worth thinking about beforehand. Benefits • Work from anywhere in the world for up to 6 weeks a year, on top of a fully remote setup — great work doesn't have to happen from one desk. • 20 days paid annual leave plus 10 days sick & carer's leave — actively encouraged, we want you to be at your best and time off is a part of that. • 16 weeks paid parental leave for primary carers (6 for secondary) — becoming a parent is life changing and we're committed to supporting you and your family through it. • A remote-work allowance for home-office kit, co-working, or working elsewhere — we want you to have everything you need to be set up for success in your role. • Confidential EAP & mental health support — sometimes life gets hard. You should be able to access the resources and support you need. • Support for learning and growth — with time and budget for conferences, courses, and coaching so you have the opportunity to grow, improve your craft, and build mastery. • Retirement and health coverage (based on your region) — build towards your future, your way. Exact benefits may vary slightly by country. We'll walk through the specifics for your location. What Happens Next Every application gets a response. We aim to move quickly through our hiring process and make it as stress free as possible for everyone. If this sounds like how you already work, apply. If you've got questions first, reach out, we'd rather have the conversation. 🌈 Equal Opportunity Employer At Buildkite, we value diversity and celebrate all types of skills, backgrounds, and experiences. We’re dedicated to fostering an inclusive environment and providing reasonable accommodations throughout our recruitment process. If you need any accommodations or support during the application or interview process, please reach out to us at accommodations@buildkite.com.