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Fixing a ‘detached HEAD’ state in CI

A detached HEAD state occurs when your CI provider checks out a specific commit instead of a branch, losing the Git context. This prevents Chromatic from finding the correct baseline to compare against.

Most CI providers

This can be caused by ephemeral merge commits (GitLab, Bitbucket) or a missing branch reference (Jenkins and others). Manually provide the Git context by setting environment variables to resolve the issue. Note that you must set all required Git variables for the fix to work correctly.

GitHub

On GitHub Actions, this issue happens when:

• You are running on a pull_request event trigger
• You are missing the ref tag on the checkout step in CI when running on pull_request