feat: auto-resolve merge failures instead of asking for manual merge (#253)

When a PR is still open after a merge attempt, query the Forgejo API for
mergeability: on conflicts spawn a rebase agent (pending-ci state); on no
conflicts retry up to 2 times; fall back to State/Question only if all
retries are exhausted. Applies to both the main pending-issue path and
the catch-up path.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/agent_loop.py

@@ -42,6 +42,7 @@ import re
 import shlex
 import subprocess
 import sys
+import time
 from datetime import datetime, timezone
 from pathlib import Path
 
@@ -278,6 +279,41 @@ def _merge_pr(pr_number: int) -> None:
     _fgj("pr", "merge", str(pr_number), "--repo", REPO, "--merge-method", "squash")
 
 
+def _handle_pr_still_open_after_merge(pr_number: int, branch: str, issue_num: int | None) -> str:
+    """Handle a PR that is still open after a successful _merge_pr() call.
+
+    Returns one of:
+      "rebase-spawned" — merge conflict detected; rebase agent started, state written
+      "merged"         — PR closed after a retry
+      "fallback"       — all options exhausted; caller should set State/Question
+    """
+    pr_data = _tea_get(f"repos/{REPO}/pulls/{pr_number}")
+    mergeable = (pr_data or {}).get("mergeable")
+
+    if mergeable is False:
+        prompt = (
+            f"Rebase branch `{branch}` onto main to resolve merge conflicts, then push. "
+            "Do not change any logic — only resolve conflicts and push."
+        )
+        session_name = f"rebase-pr-{pr_number}"
+        pid = _start_agent(prompt, session_name)
+        _write_state(pid, issue_num, "pending-ci", session_name=session_name)
+        print(f"PR #{pr_number} has merge conflicts — spawned rebase agent (pid={pid}).")
+        return "rebase-spawned"
+
+    for attempt in range(1, 3):
+        time.sleep(5)
+        try:
+            _merge_pr(pr_number)
+        except RuntimeError as e:
+            print(f"PR #{pr_number} merge retry {attempt} failed: {e}")
+        if not _find_pr_for_branch(branch):
+            print(f"PR #{pr_number} merged on retry {attempt}.")
+            return "merged"
+
+    return "fallback"
+
+
 # ── state file ────────────────────────────────────────────────────────────────
 
 
@@ -676,6 +712,13 @@ def _run_loop() -> int:
                 )
                 return 0
             if _find_pr_for_branch(branch):
+                merge_result = _handle_pr_still_open_after_merge(pr_number, branch, pending_issue)
+                if merge_result == "rebase-spawned":
+                    return 0
+                if merge_result == "merged":
+                    _close_issue(pending_issue)
+                    print(f"Merged PR #{pr_number} and closed {_issue_url(pending_issue)}.")
+                    return 0
                 print(f"PR #{pr_number} is still open after merge attempt — setting to State/Question.")
                 _set_labels(pending_issue, add=[LABEL_QUESTION], remove=[LABEL_IN_PROGRESS])
                 _comment_issue(
@@ -744,6 +787,16 @@ def _run_loop() -> int:
             # Verify the merge actually happened; fgj can exit 0 without merging
             # (e.g. branch-protection rules not satisfied).
             if _find_pr_for_branch(branch):
+                merge_result = _handle_pr_still_open_after_merge(pr_number, branch, issue_num)
+                if merge_result == "rebase-spawned":
+                    return 0
+                if merge_result == "merged":
+                    if issue_num:
+                        _close_issue(issue_num)
+                        print(f"Catch-up: merged PR #{pr_number} and closed issue #{issue_num} after retry.")
+                    else:
+                        print(f"Catch-up: merged PR #{pr_number} after retry.")
+                    return 0
                 print(
                     f"Catch-up: PR #{pr_number} is still open after merge attempt "
                     "— skipping to avoid infinite retry."

scripts/test_agent_loop.py

@@ -785,6 +785,90 @@ class TestCatchupSkipsQuestionIssues(unittest.TestCase):
         mock_merge.assert_called_once_with(50)
 
 
+class TestMergeFailsOpen(unittest.TestCase):
+    """Tests for auto-resolution when a PR is still open after the merge command."""
+
+    def _dead_state(self, issue: int, kind: str = "issue") -> dict:
+        return {
+            "pid": 999999999,
+            "issue": issue,
+            "started_at": "2026-01-01T00:00:00+00:00",
+            "type": kind,
+        }
+
+    def _open_pr(self, branch: str = "issue-10-fix") -> dict:
+        return {"number": 5, "head": {"ref": branch}, "created_at": "2026-01-01T00:00:00+00:00"}
+
+    def test_merge_fails_open_with_conflicts_spawns_rebase_agent(self):
+        """mergeable=false → rebase agent spawned, state written as pending-ci."""
+        written_state = {}
+
+        def fake_write_state(pid, issue, kind, issue_title=None, session_name=None, ci_run_id=None):
+            written_state["pid"] = pid
+            written_state["issue"] = issue
+            written_state["kind"] = kind
+            written_state["session_name"] = session_name
+
+        with patch("agent_loop._read_state", return_value=self._dead_state(10)), \
+             patch("agent_loop._find_pr_for_branch", side_effect=[self._open_pr(), self._open_pr()]), \
+             patch("agent_loop._latest_ci_run_for_branch", return_value={"id": 1, "status": "success"}), \
+             patch("agent_loop._merge_pr"), \
+             patch("agent_loop._tea_get", return_value={"mergeable": False}), \
+             patch("agent_loop._start_agent", return_value=77) as mock_start, \
+             patch("agent_loop._write_state", side_effect=fake_write_state), \
+             patch("agent_loop._clear_state"):
+            result = agent_loop._run_loop()
+
+        self.assertEqual(result, 0)
+        mock_start.assert_called_once()
+        prompt = mock_start.call_args[0][0]
+        self.assertIn("Rebase branch", prompt)
+        self.assertIn("issue-10-fix", prompt)
+        self.assertEqual(written_state.get("kind"), "pending-ci")
+        self.assertEqual(written_state.get("issue"), 10)
+
+    def test_merge_fails_open_no_conflicts_retries_and_succeeds(self):
+        """mergeable=true, second attempt succeeds → issue closed."""
+        with patch("agent_loop._read_state", return_value=self._dead_state(10)), \
+             patch("agent_loop._find_pr_for_branch",
+                   side_effect=[self._open_pr(), self._open_pr(), None]), \
+             patch("agent_loop._latest_ci_run_for_branch", return_value={"id": 1, "status": "success"}), \
+             patch("agent_loop._merge_pr"), \
+             patch("agent_loop._tea_get", return_value={"mergeable": True}), \
+             patch("agent_loop.time.sleep"), \
+             patch("agent_loop._close_issue") as mock_close, \
+             patch("agent_loop._clear_state"):
+            result = agent_loop._run_loop()
+
+        self.assertEqual(result, 0)
+        mock_close.assert_called_once_with(10)
+
+    def test_merge_fails_open_no_conflicts_all_retries_exhausted(self):
+        """All retries exhausted with PR still open → falls through to State/Question."""
+        with patch("agent_loop._read_state", return_value=self._dead_state(10)), \
+             patch("agent_loop._find_pr_for_branch",
+                   side_effect=[self._open_pr(), self._open_pr(),
+                                 self._open_pr(), self._open_pr()]), \
+             patch("agent_loop._latest_ci_run_for_branch", return_value={"id": 1, "status": "success"}), \
+             patch("agent_loop._merge_pr"), \
+             patch("agent_loop._tea_get", return_value={"mergeable": True}), \
+             patch("agent_loop.time.sleep"), \
+             patch("agent_loop._set_labels") as mock_labels, \
+             patch("agent_loop._comment_issue") as mock_comment, \
+             patch("agent_loop._close_issue") as mock_close, \
+             patch("agent_loop._clear_state"):
+            result = agent_loop._run_loop()
+
+        self.assertEqual(result, 0)
+        mock_close.assert_not_called()
+        mock_labels.assert_called_once_with(
+            10,
+            add=[agent_loop.LABEL_QUESTION],
+            remove=[agent_loop.LABEL_IN_PROGRESS],
+        )
+        mock_comment.assert_called_once()
+
+
 class TestHeartbeat(unittest.TestCase):
     """Tests for _update_heartbeat() and cmd_monitor()."""