branch value in an API request must exist in the repository connected to your Mintlify project.
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Preview deployment not created for a fork branch
Why fork pull requests and fork branches passed to the preview API do not produce preview deployments, and how maintainers can preview fork changes.
If a pull request opened from a fork shows no preview deployment link, this is expected behavior. The same is true if a call to the Trigger preview deployment endpoint with a fork branch fails. Mintlify does not build preview deployments from fork branches.
The Mintlify GitHub App must be installed on a repository to build a preview. The app is installed on your main repository, not on contributor forks, so it cannot read a fork or build a preview against it. This applies to both automatic pull request previews and previews triggered through the API. The