name: Cancel stale runs on PR close

# GitHub Actions has no direct "cancel in-flight runs when a PR closes/merges"
# trigger -- concurrency groups only cancel a running job/workflow when a NEW
# entrant joins the SAME group. These two jobs deliberately do nothing except
# join the exact concurrency groups that ci.yml and claude-code-review.yml
# already use, so a PR closing (merged or not) cancels any CI matrix -- and,
# more importantly, any still-running (money-costing) Claude review -- for a
# PR nobody can act on anymore. Concurrency groups are enforced repo-wide,
# not scoped to the workflow file that declares them, so joining the same
# group string from here works.
#
# COUPLING: these group strings are copies, not references -- if ci.yml's
# `name:` or its `concurrency.group:` formula, or claude-code-review.yml's
# `concurrency.group:` formula, ever changes, update the matching string
# below or cancellation here silently stops matching (no error, it just
# becomes its own no-op group). ci.yml's verify-cancel-on-close-coupling job
# guards this automatically on every push -- it fails CI if those files or
# fields drift, so this comment is a "why", not the only line of defense.
on:
  pull_request:
    types: [closed]

permissions: {}

jobs:
  cancel-ci:
    # Matches ci.yml's `group: ${{ github.workflow }}-${{ github.ref }}`,
    # where github.workflow is that file's `name: CI` and github.ref for a
    # pull_request-triggered run is refs/pull/<number>/merge.
    concurrency:
      group: CI-refs/pull/${{ github.event.pull_request.number }}/merge
      cancel-in-progress: true
    runs-on: ubuntu-latest
    steps:
      - run: echo "Cancelled any in-flight CI run for PR #${{ github.event.pull_request.number }}"

  cancel-claude-review:
    # Matches claude-code-review.yml's `group: claude-review-<pr-number>`.
    concurrency:
      group: claude-review-${{ github.event.pull_request.number }}
      cancel-in-progress: true
    runs-on: ubuntu-latest
    steps:
      - run: echo "Cancelled any in-flight Claude review for PR #${{ github.event.pull_request.number }}"