From c8aa4e5d2d9c852e33513e98082139bc1c3e610c Mon Sep 17 00:00:00 2001
From: Seongho Bae <me@seonghobae.me>
Date: Mon, 29 Jun 2026 23:11:51 +0900
Subject: [PATCH] Handle compare-behind update branch cases

---
 scripts/ci/pr_review_merge_scheduler.py |  3 ++-
 tests/test_pr_review_merge_scheduler.py | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/scripts/ci/pr_review_merge_scheduler.py b/scripts/ci/pr_review_merge_scheduler.py
index 3e54a1ddf..d79b99cbf 100644
--- a/scripts/ci/pr_review_merge_scheduler.py
+++ b/scripts/ci/pr_review_merge_scheduler.py
@@ -478,7 +478,8 @@ def compare_behind_by(pr: dict[str, Any]) -> int:
 
 def branch_outdated_by_base(pr: dict[str, Any], merge_state: str) -> int:
     """Return known count of base commits missing from the PR head."""
-    if merge_state == "BEHIND":
+    compare_status = (pr.get("compareStatus") or "").lower()
+    if merge_state == "BEHIND" or compare_status == "behind":
         return max(1, compare_behind_by(pr))
     return compare_behind_by(pr)
 
diff --git a/tests/test_pr_review_merge_scheduler.py b/tests/test_pr_review_merge_scheduler.py
index e1e198496..cbab58f43 100644
--- a/tests/test_pr_review_merge_scheduler.py
+++ b/tests/test_pr_review_merge_scheduler.py
@@ -1199,6 +1199,27 @@ def test_inspect_pr_blocks_and_waits_for_policy_states(monkeypatch):
     assert "existing auto-merge request remains queued" in blocked_without_opencode_decision.reason
     assert called == [("owner/repo", 1, True)]
     called.clear()
+    blocked_compare_behind_auto = make_pr(
+        mergeStateStatus="BLOCKED",
+        restMergeableState="BLOCKED",
+        compareStatus="behind",
+        autoMergeRequest={"enabledAt": "now"},
+        statusCheckRollup={
+            "contexts": {
+                "nodes": [
+                    {"__typename": "CheckRun", "name": "strix", "conclusion": "FAILURE"},
+                    {"__typename": "CheckRun", "name": "coverage-evidence", "conclusion": "FAILURE"},
+                ],
+            }
+        },
+    )
+    blocked_compare_behind_decision = inspect(blocked_compare_behind_auto)
+    assert blocked_compare_behind_decision.action == "update_branch"
+    assert "auto-merge already enabled" in blocked_compare_behind_decision.reason
+    assert "base branch is 1 commit(s) ahead" in blocked_compare_behind_decision.reason
+    assert "existing auto-merge request remains queued" in blocked_compare_behind_decision.reason
+    assert called == [("owner/repo", 1, True)]
+    called.clear()
     disabled.clear()
     assert (
         inspect(blocked_failed_behind_auto_without_opencode_approval, update_branches=False).reason