🏷️ Discussion Type

Bug

Body

Since about September 10, 2026 (between ~15:20 UTC Sep 10 and ~06:40 UTC Sep 11), auto-merge no longer adds pull requests to the merge queue for us. Nothing in our configuration changed during that window.

Expected: an author turns on auto-merge ("Merge when ready") while the PR is still waiting on review or required checks. When the last requirement is met, GitHub adds the PR to the merge queue automatically. This worked reliably for us for months; the median delay was about 30 seconds.

Actual: the PR becomes fully mergeable and stays there with auto-merge still enabled, but it is never added to the queue:

• mergeStateStatus: CLEAN
• reviewDecision: APPROVED
• all required checks are green
• autoMergeRequest is set, but isInMergeQueue is false

Some PRs sat like this for hours or days, the longest for 8 days. Everything moves again as soon as someone disables auto-merge and clicks "Merge when ready" again (the PR is added to the queue at once), or calls the enqueuePullRequest GraphQL mutation.

Impact (one repo, ~260 merged PRs/week):

These cases came from 75 different authors.

Setup:

• Merge queue on the default branch, configured with a repository ruleset:
  • merge method: rebase
  • grouping: ALLGREEN
  • build concurrency: 5
  • 1 PR merged per group
• Pull request rule:
  • 1 approval
  • dismiss stale approvals
  • require approval of the most recent push
  • allowed merge methods: rebase only
• One required status check from GitHub Actions.
• An organization ruleset that also requires code-owner review and resolved conversations.
• Repository settings:
  • squash and merge commits disabled, rebase enabled
  • "Allow auto-merge" was off at first; we turned it on during troubleshooting and it made no difference

What we've ruled out:

• No ruleset, branch protection, workflow or repository setting changes in the weeks around the onset. The last ruleset edit was about 2 weeks earlier.
• No incident on githubstatus.com for that window.
• Turning on "Allow auto-merge" in repository settings changed nothing.
• autoMergeRequest.mergeMethod is always SQUASH, even though only rebase is allowed. We tried to set REBASE through enablePullRequestAutoMerge, but GitHub stores SQUASH anyway. This was the same before the onset, so it probably isn't the cause.
• Adding PRs to the queue manually (UI or enqueuePullRequest) works every time; only the automatic step fails.

Possibly related: cli/cli#13398, where enablePullRequestAutoMerge behaves inconsistently when the merge queue is defined by a ruleset.

Is anyone else seeing this since ~Sep 10? Did something change in how auto-merge hands PRs to rulesets-based merge queues?