The Buildkite Agent

This page references the out-of-date Buildkite Agent v2.

For docs referencing the Buildkite Agent v3, see the latest version of this document.

The Buildkite agent is a small, reliable and cross-platform build runner that makes it easy to run automated builds on your own infrastructure. Its main responsibilities are polling for work, running build jobs, reporting back the status code and output log of the job, and uploading the job's artifacts.

How it works

The agent works by polling Buildkite's agent API over HTTPS. There is no need to forward ports or provide incoming firewall access, and the agents can be run across any number of machines and networks.

Diagram showing agent to agent API communication

The agent starts by registering itself with Buildkite, and once registered it's placed into your organization's agents pool. The agent periodically polls Buildkite looking for new work, waiting to accept an available job.

After accepting a build job the agent will execute the command, streaming back the build script's output and then posting the final exit status.

Whilst the job is running you can use the buildkite-agent meta-data command to set and get build-wide meta-data, and buildkite-agent artifact for fetching and retrieving binary build-wide artifacts. These two commands allow you to have completely isolated build jobs (similar to a 12 factor web application) but have access to shared state and data storage across any number of machines and networks.


You can install the agent on a wide variety of platforms, see the installation instructions for a full list and for information on how to get started.


$ buildkite-agent --help

  buildkite-agent  [arguments...]

Available commands are:

  start       Starts a Buildkite agent
  artifact    Upload/download artifacts from Buildkite jobs
  meta-data   Get/set data from Buildkite jobs
  pipeline   Make changes to the pipeline of the currently running build
  help, h     Shows a list of commands or help for one command

Use "buildkite-agent  --help" for more information about a command.

To start an agent you'll need your organization's agent token from the Agents page of your Buildkite dashboard. You pass the token to the agent using an environment variable or command line flag, and it will register itself with Buildkite and wait to accept jobs.


The agent has a standard configuration file format on all systems to set meta-data, priority, etc. See the configuration documentation for more details.

Customizing with hooks

The agent's behavior can be customized using hooks, which are shell scripts that exist on your build machines or in each pipeline's code repository. Hooks can be used to set up secrets as well as overriding default behavior. See the hooks documentation for full details.

Signal handling

When a build job is canceled the agent will send the build job process a SIGTERM signal to allow it to gracefully exit. If the process does not exit within 10 seconds it will be forcefully terminated with a SIGKILL signal.