The current version is v3.36.1 as of 2022 July 2nd.
Official document: https://buildkite.com/docs/agent/v3
Buildkite Agent is the code runner that is a cross-platform binary written in Go. It is very small and consumes very little memory. Drop to your machine / comptuer, then you have your code runner.
buildkite-agent start --token='...' --endpoint https://agent.buildkite.com/v3 --name '🐻-%spawn' --spawn 10