diff --git a/.gitea/scripts/gitea-merge-queue.py b/.gitea/scripts/gitea-merge-queue.py
index 46b0482ad..e3e57ad2e 100644
--- a/.gitea/scripts/gitea-merge-queue.py
+++ b/.gitea/scripts/gitea-merge-queue.py
@@ -407,7 +407,23 @@ def process_once(*, dry_run: bool = False) -> int:
                 "deferring to next tick"
             )
             return 0
-        merge_pull(pr_number, dry_run=dry_run)
+        try:
+            merge_pull(pr_number, dry_run=dry_run)
+        except ApiError as exc:
+            # Merge API errors (405 permission denied, 422 hook block, etc.)
+            # are NOT transient — retrying will not help. Surface the error
+            # on the PR immediately so it is visible without digging into
+            # workflow logs, and fail the workflow so it is distinguishable
+            # from a successful-no-op tick.
+            post_comment(
+                pr_number,
+                f"merge-queue: MERGE FAILED — {exc}. "
+                "This is a non-transient error (permission or hook issue). "
+                "See SEV-1 internal#487.",
+                dry_run=dry_run,
+            )
+            sys.stderr.write(f"::error::PR #{pr_number} merge failed: {exc}\n")
+            return 2  # distinct exit code so workflow run shows failure
         return 0
     return 0
 
diff --git a/.gitea/scripts/sop-checklist.py b/.gitea/scripts/sop-checklist.py
index efd62e9c7..02407b096 100644
--- a/.gitea/scripts/sop-checklist.py
+++ b/.gitea/scripts/sop-checklist.py
@@ -830,9 +830,18 @@ def main(argv: list[str] | None = None) -> int:
     # one membership lookup per team.
     team_member_cache: dict[tuple[str, int], bool | None] = {}
 
+    def _required_teams_for(slug: str) -> list[str] | None:
+        """Look up required_teams for a slug from checklist items OR N/A gates."""
+        if slug in items_by_slug:
+            return items_by_slug[slug]["required_teams"]
+        if slug in na_gates:
+            return na_gates[slug].get("required_teams", [])
+        return None
+
     def probe(slug: str, users: list[str]) -> list[str]:
-        item = items_by_slug[slug]
-        team_names: list[str] = item["required_teams"]
+        team_names = _required_teams_for(slug)
+        if team_names is None:
+            raise KeyError(f"slug '{slug}' not found in items or N/A gates")
         # Resolve names → ids. NOTE: orgs/{org}/teams/search may not be
         # available — fall back to the list endpoint.
         team_ids: list[int] = []
diff --git a/.gitea/scripts/tests/test_gitea_merge_queue.py b/.gitea/scripts/tests/test_gitea_merge_queue.py
index b01c6da22..747bf233a 100644
--- a/.gitea/scripts/tests/test_gitea_merge_queue.py
+++ b/.gitea/scripts/tests/test_gitea_merge_queue.py
@@ -1,6 +1,7 @@
 import importlib.util
 import sys
 from pathlib import Path
+from unittest.mock import patch
 
 
 SCRIPT = Path(__file__).resolve().parents[1] / "gitea-merge-queue.py"
@@ -118,3 +119,54 @@ def test_merge_decision_updates_stale_pr_before_merge():
 
     assert decision.ready is False
     assert decision.action == "update"
+
+
+def test_merge_failure_returns_nonzero_and_posts_comment(monkeypatch):
+    """When merge_pull raises ApiError (e.g. HTTP 405 permission denied),
+    process_once returns exit code 2 (non-zero) and posts a comment on the PR.
+    This distinguishes merge-permission errors from successful-no-op ticks."""
+    captured_comment = {}
+
+    def fake_post_comment(pr_number, body, *, dry_run):
+        captured_comment["pr_number"] = pr_number
+        captured_comment["body"] = body
+
+    # Replace functions directly on the module object so process_once()
+    # (which looks them up by name at call time) picks up the fakes.
+    mq.list_queued_issues = lambda: [{
+        "number": 42,
+        "created_at": "2026-05-17T00:00:00Z",
+        "labels": [{"name": "merge-queue"}],
+        "pull_request": {},
+    }]
+    mq.get_pull = lambda n: {
+        "state": "open",
+        "base": {"ref": "main", "repo_id": 1},
+        "head": {"sha": "headsha", "repo_id": 1},
+        "merge_base": "abc123def",
+    }
+    mq.get_pull_commits = lambda n: [{"sha": "headsha"}]
+    mq.get_branch_head = lambda branch: "abc123def"
+    mq.get_combined_status = lambda sha: {
+        "state": "success",
+        "statuses": [{"context": "CI / all-required (push)", "status": "success"}],
+    }
+    mq.latest_statuses_by_context = lambda s: {
+        "CI / all-required (pull_request)": {"status": "success"},
+        "sop-checklist / all-items-acked (pull_request)": {"status": "success"},
+    }
+    mq.required_contexts_green = lambda statuses, contexts: (True, [])
+    mq.post_comment = fake_post_comment
+
+    # Simulate merge failing with HTTP 405 (permission denied).
+    # The ApiError raised by api() is caught inside process_once().
+    merge_error = mq.ApiError(
+        "POST /repos/x/y/pulls/42/merge -> HTTP 405: User not allowed to merge PR"
+    )
+    with patch.object(mq, "merge_pull", side_effect=merge_error):
+        exit_code = mq.process_once(dry_run=False)
+
+    assert exit_code == 2, f"Expected exit code 2, got {exit_code}"
+    assert captured_comment["pr_number"] == 42
+    assert "MERGE FAILED" in captured_comment["body"]
+    assert "405" in captured_comment["body"]
diff --git a/.gitea/scripts/tests/test_sop_checklist.py b/.gitea/scripts/tests/test_sop_checklist.py
index 91c016a13..3eb71dbce 100644
--- a/.gitea/scripts/tests/test_sop_checklist.py
+++ b/.gitea/scripts/tests/test_sop_checklist.py
@@ -603,3 +603,51 @@ class TestComputeNaState(unittest.TestCase):
         self.assertEqual(na_directives[0][0], "sop-n/a")
         self.assertEqual(na_directives[0][1], "qa-review")
         self.assertIn("no surface", na_directives[0][2])
+
+
+class TestProbeNaGateFallback(unittest.TestCase):
+    """Regression test: probe() must handle gate names (qa-review, security-review)
+    from N/A gates without raising KeyError.
+
+    mc#1389: compute_na_state calls probe(gate_name, [user]) where gate_name is
+    a gate name like 'qa-review' — NOT a checklist item slug. The probe must
+    resolve the gate's required_teams from na_gates, not raise KeyError from
+    items_by_slug lookup.
+    """
+
+    def test_probe_resolves_gate_name_from_na_gates(self):
+        cfg = sop.load_config(CONFIG_PATH)
+        items = cfg["items"]
+        items_by_slug = {it["slug"]: it for it in items}
+        na_gates = cfg.get("n/a_gates", {})
+
+        # Reconstruct the _required_teams_for helper from sop-checklist.py
+        def _required_teams_for(slug):
+            if slug in items_by_slug:
+                return items_by_slug[slug]["required_teams"]
+            if slug in na_gates:
+                return na_gates[slug].get("required_teams", [])
+            return None
+
+        # Gate names should resolve from na_gates
+        self.assertEqual(
+            _required_teams_for("qa-review"),
+            ["qa", "security", "engineers"],
+        )
+        self.assertEqual(
+            _required_teams_for("security-review"),
+            ["security", "managers", "ceo"],
+        )
+
+        # Checklist item slugs should still resolve from items_by_slug
+        self.assertEqual(
+            _required_teams_for("comprehensive-testing"),
+            ["qa", "engineers"],
+        )
+        self.assertEqual(
+            _required_teams_for("root-cause"),
+            ["managers", "ceo"],
+        )
+
+        # Unknown slug should return None (not raise KeyError)
+        self.assertIsNone(_required_teams_for("nonexistent-slug"))