Can't scope Preview env var to a branch anymore

Our project is not connected to a Git repository in Vercel. We deploy from GitHub Actions with the Vercel CLI (vercel --token ... --yes), and vercel.json has "github": { "enabled": false }.

Until recently we could scope Preview environment variables to a specific branch in the dashboard. For example, ALLOWED_ORIGINS has been set to Preview · staging since June 11. It is still there and is applied to our staging CLI deployments.

Now, when I add a new variable (SPAM_EMAIL, type Config, environment Preview) and type staging in the branch field, the dashboard shows:

"Branch "staging" not found in the connected Git repository."

and won't save it. The branch does exist on GitHub.

Was this validation added recently? Is branch scoping now only possible for projects with a connected Git repository?

Solved: it was caused by transferring the GitHub repository to another GitHub organization.

I had moved the repository to a different GitHub organization. In Vercel, Settings → Git still showed the repository as connected, with the original "Connected" date. The new organization name was displayed, but the repository link still pointed to the old organization. Apparently Vercel still used the old repository reference internally and couldn't look up its branches anymore.

As a result, every attempt to scope a Preview environment variable to a branch failed with:

Branch "staging" not found in the connected Git repository.

It failed the same way in the dashboard and in the CLI (vercel env add NAME preview staging), even though the branch exists on GitHub. Branch-scoped variables created before the transfer kept working.

Fix: Project → Settings → Git → Disconnect, then connect the repository again from its new organization. After that, branch-scoped Preview variables could be added normally.

Notes for anyone doing the same:

Make sure the Vercel GitHub App is installed in the new GitHub organization and has access to the repository.
Before disconnecting, write down your existing branch-scoped environment variables, and check afterwards that they are still there.
If several Vercel projects use the same repository, each one probably needs to be reconnected.