stage

A stage is one step of a workflow. It declares four things:

• Who executes it. An agent, a human, or neither. An agent stage spawns the runner; a human stage waits.
• What it consumes. An issue, or an artifact produced by an earlier stage.
• What it produces. An artifact — a plan, a pull request, a report.
• What it may not do. Constraints, checked against the result.

- id: implement
  type: implement
  executor:
    agent: claude-code
  inputs:
    - artifact: plan
      from_stage: plan
  produces:
    - artifact: pull_request
  constraints:
    - forbidden_paths: [".github/workflows/**"]

Stage state

A stage is pending, then dispatched, then running, then terminal — succeeded, failed, or cancelled. A stage that produces an artifact does not reach succeeded until the artifact exists and its constraints pass.

Stages are ordered, and by default sequential: the next one does not start until the previous one is terminal and its gates are satisfied. A workflow may declare dependencies explicitly when the order is not a straight line.

Related

• gate — what holds a stage before or after it runs.
• constraint — what is checked against what it produced.