Install and configure a Buildkite agent with custom queues and tags

Steps

1. Install the agent via the platform package manager (e.g., brew install buildkite/buildkite/buildkite-agent on macOS, or the Linux bash installer) and locate the configuration file at /etc/buildkite-agent/buildkite-agent.cfg
2. Set token to the agent token from your Buildkite cluster's agent token settings page; each cluster has its own token that scopes agent registration
3. Set tags (previously called metadata) to a comma-separated list of key=value pairs: tags="queue=linux-x86,env=production,docker=true" — the queue tag controls which pipeline steps dispatch to this agent
4. Start the agent with buildkite-agent start; multiple agents on one host can be started by running the command multiple times or setting spawn=N in the config to fork N workers
5. Target the agent in a pipeline step with agents: {queue: linux-x86, docker: 'true'} — all specified key=value pairs must match for the step to dispatch
6. Use Buildkite Clusters (Organization Settings > Clusters) to group agents and restrict which pipelines can use each cluster's agents for multi-tenant isolation