Dbochman/github-actions-cancel-on-pr-merge

Cancel GitHub Actions Workflows on PR Merge

Problem

GitHub Actions workflows triggered by pull_request events continue running even after the PR is merged or closed. The cancel-in-progress: true concurrency setting only cancels when new commits are pushed, not when the PR is closed.

Context / Trigger Conditions

• Slow CI jobs (like AI code reviews) continue running after PR merge
• You're paying for CI minutes that provide no value
• You have cancel-in-progress: true but it doesn't help on merge
• Workflow runs show as "in progress" after PR is already merged

Solution

Add closed to the PR event types and add a job condition to skip running on close:

name: PR Workflow

on:
  pull_request:
    branches: [main]
    types: [opened, synchronize, closed]  # Add 'closed'

# Cancel in-progress runs when PR is closed/merged
concurrency:
  group: workflow-name-${{ github.event.pull_request.number }}
  cancel-in-progress: true

jobs:
  my-job:
    runs-on: ubuntu-latest
    # Skip if PR is closed - concurrency cancels in-progress runs
    if: github.event.action != 'closed'
    steps:
      # ... job steps

How It Works

1. When a PR is merged/closed, GitHub fires the closed event
2. This triggers the workflow with github.event.action == 'closed'
3. The concurrency group matches any in-progress run for this PR
4. cancel-in-progress: true cancels the old run
5. The new run's job condition github.event.action != 'closed' causes it to skip
6. Net result: old run cancelled, no new run started

Verification

1. Open a PR and let CI start running
2. Merge the PR while CI is still in progress
3. Check the Actions tab - the in-progress run should be cancelled
4. Verify no new "closed" run is started (or it's skipped immediately)

Example

Before (workflows continue after merge):

on:
  pull_request:
    branches: [main]
    types: [opened, synchronize]

concurrency:
  group: ci-${{ github.event.pull_request.number }}
  cancel-in-progress: true

After (workflows cancel on merge):

on:
  pull_request:
    branches: [main]
    types: [opened, synchronize, closed]

concurrency:
  group: ci-${{ github.event.pull_request.number }}
  cancel-in-progress: true

jobs:
  build:
    if: github.event.action != 'closed'
    # ...

Notes

• The job-level if condition is important - without it, a new job would start and immediately succeed, which still wastes a runner startup
• This pattern works for any PR-triggered workflow (tests, reviews, deployments)
• For workflows that should run on close (like cleanup), use a separate job with if: github.event.action == 'closed'
• The concurrency group should include the PR number to scope cancellation correctly

References

• GitHub Actions: Events that trigger workflows
• GitHub Actions: Using concurrency