Required merge queue branch protection rule bypassed by REST merge API

[AgentAntelope]

🏷️ Discussion Type

Bug

Body

Setup

Our default branch main has “Require merge queue” enabled via a classic branch protection rule: admin-enforced, with no bypass actors and no push restrictions. There is also a repository ruleset targeting the same branch whose merge_queue rule is currently in evaluate mode, as we assess moving to rulesets.

Human merges through the web UI are correctly routed through the queue.

Expected

With “Require merge queue” active on the branch protection rule, no actor lacking an explicit bypass should be able to land a merge on main outside the queue, regardless of how they merge.

Actual

An account with only write permission and no bypass grant can merge pull requests directly via PUT /repos/OWNER/REPO/pulls/{n}/merge, landing on our protected branch without ever entering the queue.

Evidence

Comparing a bypassed merge (#NNN) with a normal UI merge (#MMM):

Bypassed merge queue PR: commit committer is web-flow; PR timeline shows a bare merged event with no added_to_merge_queue.
Normal PR (UI merge): timeline shows added_to_merge_queue -> github-merge-queue[bot], as expected.

The merging account has write (not admin); enforce_admins = true; the branch rule has no bypass_pull_request_allowances and no push restrictions.

Rule Insights rule-suite for #NNN: The evaluation in the suite came from our evaluate-mode ruleset (result fail: “Changes must be made through the merge queue”), which doesn’t block at the moment. It appears the branch protection rule merge queue requirement simply isn’t evaluated against the API merge.

Questions

• Why does the branch protection merge-queue requirement not surface as a rule evaluation in Rule Insights, while its other rules do? Is this related?

---

We will probably move to rulesets to solve this issue, as they seem to work as intended (at least based on the evaluation runs).

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