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…