fix: isolate #519 PR lookup from shared lease comment listing

Keep _fetch_pr_lease_comments_safe for gitea_assess_conflict_fix_push
only. Restore _list_pr_lease_comments to a single comments GET so merge
approval feedback and #485 non-list handling keep stable API call order.

Closes #519

gitea_mcp_server.py

@@ -2940,16 +2940,25 @@ def _list_pr_lease_comments(
     repo: str | None,
     limit: int = 100,
 ) -> list[dict]:
-    """Fetch PR/issue thread comments used for reviewer/conflict-fix leases."""
+    """Fetch PR/issue thread comments used for reviewer/conflict-fix leases.
-    fetched = _fetch_pr_lease_comments_safe(
+
-        pr_number,
+    Intentionally does **not** pre-fetch the PR via GET /pulls/{n}. Shared
-        remote=remote,
+    callers (merge approval feedback, reviewer lease gates) depend on a single
-        host=host,
+    comments GET so mock sequences and fail-open #485 non-list handling stay
-        org=org,
+    stable. Structured PR-lookup failures belong only to
-        repo=repo,
+    :func:`_fetch_pr_lease_comments_safe` used by conflict-fix push assessment
-        limit=limit,
+    (#519).
-    )
+    """
-    return fetched["comments"]
+    h, o, r = _resolve(remote, host, org, repo)
+    auth = _auth(h)
+    api = f"{repo_api_url(h, o, r)}/issues/{pr_number}/comments"
+    comments = api_request("GET", api, auth)
+    # Fail safe to no lease comments when the API returns a non-list payload
+    # (e.g. an error object such as an HTTP 401 body): lease state can only be
+    # proven from real comment entries, never inferred from an error shape (#485).
+    if not isinstance(comments, list):
+        return []
+    return list(comments[:limit])
 
 
 def _pr_work_lease_reviewer_block(

tests/test_pr_lease_comments_non_list_guard.py

@@ -16,31 +16,26 @@ AUTHOR_ENV = {
     "GITEA_PROFILE_NAME": "gitea-author",
     "GITEA_ALLOWED_OPERATIONS": "gitea.read,gitea.issue.comment",
 }
-OPEN_PR = {"number": 12, "state": "open", "head": {"sha": "abc123"}}
-
-
-def _pr_then_comments(mock_api, comments_payload):
-    def _api(method, url, auth, *args, **kwargs):
-        if "/pulls/" in url:
-            return OPEN_PR
-        return comments_payload
-
-    mock_api.side_effect = _api
 
 
 class TestPrLeaseCommentsNonListGuard(unittest.TestCase):
     @patch("mcp_server.api_request")
     @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
     def test_list_pr_lease_comments_non_list_payload_returns_empty(self, _auth, mock_api):
-        _pr_then_comments(mock_api, {"message": "Unauthorized"})
+        mock_api.return_value = {"message": "Unauthorized"}
         result = _list_pr_lease_comments(
             12, remote="prgs", host=None, org=None, repo=None)
         self.assertEqual(result, [])
+        # Single comments GET only — no pre-flight PR lookup (#519 isolation).
+        mock_api.assert_called_once()
+        _method, url, _auth_arg = mock_api.call_args[0][:3]
+        self.assertIn("/issues/12/comments", url)
+        self.assertNotIn("/pulls/", url)
 
     @patch("mcp_server.api_request")
     @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
     def test_list_pr_lease_comments_none_returns_empty(self, _auth, mock_api):
-        _pr_then_comments(mock_api, None)
+        mock_api.return_value = None
         result = _list_pr_lease_comments(
             12, remote="prgs", host=None, org=None, repo=None)
         self.assertEqual(result, [])
@@ -49,7 +44,7 @@ class TestPrLeaseCommentsNonListGuard(unittest.TestCase):
     @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
     def test_list_pr_lease_comments_list_payload_unchanged(self, _auth, mock_api):
         comment = {"id": 7, "body": "<!-- mcp-review-lease:v1 -->"}
-        _pr_then_comments(mock_api, [comment])
+        mock_api.return_value = [comment]
         result = _list_pr_lease_comments(
             12, remote="prgs", host=None, org=None, repo=None, limit=5)
         self.assertEqual(result, [comment])