Why does every PR say a patch build is required?

Chromatic can’t find a build at the merge base for those pull requests. A patch build supplies that missing build so UI Review can compare the branches.

First, check that CI fetches enough Git history for Chromatic to identify the merge base. For GitHub Actions, set fetch-depth: 0 on the checkout step:

- uses: actions/checkout@v7
  with:
    fetch-depth: 0

Then check whether Chromatic has builds for the relevant commits on the base branch. A missing historical build is common when you first install Chromatic. Follow the patch build instructions in UI Review for an affected pull request. See Branching and baselines for how Chromatic chooses the merge base.

If the merge base is old, you can update the pull request branch from its base branch and run Chromatic again. This changes the merge base, but you may still need a patch build if no build exists there.

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