PR UI update branch with rebase broken on conflict-free branches

[serkansahin]

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Bug

Body

Hi all,

We’re seeing what looks like a new GitHub PR UI behaviour/regression around rebasing PR branches from the PR page.

What is happening

On conflict-free PRs that are simply behind the base branch, Update branch -> With rebase fails in the PR UI.

After enabling Allow rebase merging at repository level (to troubleshoot), the issue became explicit:

• The rebase action was greyed out in the PR Update branch menu and a yellow warning appeared: A problem occurred while generating the rebase commit

Important context

This is not isolated to one repository. We reproduced it on multiple repos. This behaviour appears new in our environment. Before Monday, March 3rd, we did not need this extra setting/workaround for the same workflow.

What we validated with git (no actual content conflict)

For affected branches, we checked:

• no merge commits on top of base branch
• no conflict markers involved
• branch topology is simple (normal commits ahead)
• local rebase works fine (git fetch <remote> then git rebase -i <remote>/<base>)

So from git’s perspective, branches are rebaseable.

Repro steps

• Use a repo where Allow rebase merging was initially disabled.
• Open a PR where head branch is behind master but conflict-free.
• Try Update branch -> Update with rebase in PR UI.
• Enable Allow rebase merging in repo settings for Pull Requests.
• Return to the same PR and retry Update branch -> Update with rebase

Observed result

• Yellow message appears: A problem occurred while generating the rebase commit
• Rebase action can be greyed out / unavailable

Expected result
GitHub should generate the rebased branch update (same as local git behavior)

Workaround that consistently worked for us

• Enable Allow rebase merging (if disabled).
• In the PR, temporarily change the base branch to another branch.
• Change base back to original target (ex: main branch or develop depending on your internal repo management).
• Refresh the PR page.

After this “base toggle,” the yellow message disappears and rebase update works again.

Why we think this may be platform-side

• Reproduced across multiple repos
• Local git rebase succeeds consistently
• UI behavior seems tied to PR metadata/state recomputation
• Base-branch toggle acts like a metadata refresh and resolves the issue

Questions

• Has anyone else seen this start recently?
• Is there a known backend/UI change in PR rebase generation around early March?
• Is this a known stale PR state issue with an official fix beyond base-branch toggle?

[bewuethr]

I (and others) noticed that the "Update with rebase" option is simply gone; enabling "allow rebase merges" didn't bring it back.

[adamdullenty]

At my employer we have also seen that the "Update with rebase" option disappeared entirely from the UI.

Oddly, enabling "allow rebase merges" temporarily did bring the "Update with rebase" option back, but some (including us) might not want to leave this enabled. It's not really a solution to this, even if it does work for some

[JulienMelissas]

Just commenting that I'm seeing this and our DevOps team has not made any changes to repo configuration that we know of.

[ebndev]

Hi all, we appreciate you reaching out to report this issue!

The GitHub team is aware of this and they are working on a solution. We'll provide details when they're available in this discussion.

Please subscribe to that post to receive real-time notifications on updates. If you have further questions or additional details about your experience, please comment directly there as well.