fix: fall back to heuristic when bot open_id fetch fails

If _fetch_bot_open_id returns None the exact-match path would silently
disable all @mention detection. Restore the old heuristic as a fallback.
Add 6 unit tests for _is_bot_mentioned covering both paths.

Made-with: Cursor

nanobot/channels/feishu.py

@@ -431,8 +431,13 @@ class FeishuChannel(BaseChannel):
             if not mid:
                 continue
             mention_open_id = getattr(mid, "open_id", None) or ""
-            if self._bot_open_id and mention_open_id == self._bot_open_id:
-                return True
+            if self._bot_open_id:
+                if mention_open_id == self._bot_open_id:
+                    return True
+            else:
+                # Fallback heuristic when bot open_id is unavailable
+                if not getattr(mid, "user_id", None) and mention_open_id.startswith("ou_"):
+                    return True
         return False
 
     def _is_group_message_for_bot(self, message: Any) -> bool:

tests/channels/test_feishu_mention.py

@@ -0,0 +1,62 @@
+"""Tests for Feishu _is_bot_mentioned logic."""
+
+from types import SimpleNamespace
+
+import pytest
+
+from nanobot.channels.feishu import FeishuChannel
+
+
+def _make_channel(bot_open_id: str | None = None) -> FeishuChannel:
+    config = SimpleNamespace(
+        app_id="test_id",
+        app_secret="test_secret",
+        verification_token="",
+        event_encrypt_key="",
+        group_policy="mention",
+    )
+    ch = FeishuChannel.__new__(FeishuChannel)
+    ch.config = config
+    ch._bot_open_id = bot_open_id
+    return ch
+
+
+def _make_message(mentions=None, content="hello"):
+    return SimpleNamespace(content=content, mentions=mentions)
+
+
+def _make_mention(open_id: str, user_id: str | None = None):
+    mid = SimpleNamespace(open_id=open_id, user_id=user_id)
+    return SimpleNamespace(id=mid)
+
+
+class TestIsBotMentioned:
+    def test_exact_match_with_bot_open_id(self):
+        ch = _make_channel(bot_open_id="ou_bot123")
+        msg = _make_message(mentions=[_make_mention("ou_bot123")])
+        assert ch._is_bot_mentioned(msg) is True
+
+    def test_no_match_different_bot(self):
+        ch = _make_channel(bot_open_id="ou_bot123")
+        msg = _make_message(mentions=[_make_mention("ou_other_bot")])
+        assert ch._is_bot_mentioned(msg) is False
+
+    def test_at_all_always_matches(self):
+        ch = _make_channel(bot_open_id="ou_bot123")
+        msg = _make_message(content="@_all hello")
+        assert ch._is_bot_mentioned(msg) is True
+
+    def test_fallback_heuristic_when_no_bot_open_id(self):
+        ch = _make_channel(bot_open_id=None)
+        msg = _make_message(mentions=[_make_mention("ou_some_bot", user_id=None)])
+        assert ch._is_bot_mentioned(msg) is True
+
+    def test_fallback_ignores_user_mentions(self):
+        ch = _make_channel(bot_open_id=None)
+        msg = _make_message(mentions=[_make_mention("ou_user", user_id="u_12345")])
+        assert ch._is_bot_mentioned(msg) is False
+
+    def test_no_mentions_returns_false(self):
+        ch = _make_channel(bot_open_id="ou_bot123")
+        msg = _make_message(mentions=None)
+        assert ch._is_bot_mentioned(msg) is False