refactor(gateway): drop _append_to_jsonl from mirror

Mirror messages are persisted via _append_to_sqlite. JSONL writer was
a redundant dual-write. Updated test assertions from JSONL file checks
to SQLite mock verification.

gateway/mirror.py

@@ -64,7 +64,6 @@ def mirror_to_session(
             "mirror_source": source_label,
         }
 
-        _append_to_jsonl(session_id, mirror_msg)
         _append_to_sqlite(session_id, mirror_msg)
 
         logger.debug("Mirror: wrote to session %s (from %s)", session_id, source_label)
@@ -150,15 +149,6 @@ def _find_session_id(
     return best_entry.get("session_id")
 
 
-def _append_to_jsonl(session_id: str, message: dict) -> None:
-    """Append a message to the JSONL transcript file."""
-    transcript_path = _SESSIONS_DIR / f"{session_id}.jsonl"
-    try:
-        with open(transcript_path, "a", encoding="utf-8") as f:
-            f.write(json.dumps(message, ensure_ascii=False) + "\n")
-    except Exception as e:
-        logger.debug("Mirror JSONL write failed: %s", e)
-
 
 def _append_to_sqlite(session_id: str, message: dict) -> None:
     """Append a message to the SQLite session database."""

tests/gateway/test_mirror.py

@@ -8,7 +8,6 @@ import gateway.mirror as mirror_mod
 from gateway.mirror import (
     mirror_to_session,
     _find_session_id,
-    _append_to_jsonl,
 )
 
 
@@ -152,33 +151,6 @@ class TestFindSessionId:
         assert result == "sess_1"
 
 
-class TestAppendToJsonl:
-    def test_appends_message(self, tmp_path):
-        sessions_dir = tmp_path / "sessions"
-        sessions_dir.mkdir()
-
-        with patch.object(mirror_mod, "_SESSIONS_DIR", sessions_dir):
-            _append_to_jsonl("sess_1", {"role": "assistant", "content": "Hello"})
-
-        transcript = sessions_dir / "sess_1.jsonl"
-        lines = transcript.read_text().strip().splitlines()
-        assert len(lines) == 1
-        msg = json.loads(lines[0])
-        assert msg["role"] == "assistant"
-        assert msg["content"] == "Hello"
-
-    def test_appends_multiple_messages(self, tmp_path):
-        sessions_dir = tmp_path / "sessions"
-        sessions_dir.mkdir()
-
-        with patch.object(mirror_mod, "_SESSIONS_DIR", sessions_dir):
-            _append_to_jsonl("sess_1", {"role": "assistant", "content": "msg1"})
-            _append_to_jsonl("sess_1", {"role": "assistant", "content": "msg2"})
-
-        transcript = sessions_dir / "sess_1.jsonl"
-        lines = transcript.read_text().strip().splitlines()
-        assert len(lines) == 2
-
 
 class TestMirrorToSession:
     def test_successful_mirror(self, tmp_path):
@@ -192,15 +164,16 @@ class TestMirrorToSession:
 
         with patch.object(mirror_mod, "_SESSIONS_DIR", sessions_dir), \
              patch.object(mirror_mod, "_SESSIONS_INDEX", index_file), \
-             patch("gateway.mirror._append_to_sqlite"):
+             patch("gateway.mirror._append_to_sqlite") as mock_sqlite:
             result = mirror_to_session("telegram", "12345", "Hello!", source_label="cli")
 
         assert result is True
 
-        # Check JSONL was written
+        # Check SQLite writer was called with the mirror message
-        transcript = sessions_dir / "sess_abc.jsonl"
+        mock_sqlite.assert_called_once()
-        assert transcript.exists()
+        call_args = mock_sqlite.call_args
-        msg = json.loads(transcript.read_text().strip())
+        assert call_args[0][0] == "sess_abc"
+        msg = call_args[0][1]
         assert msg["content"] == "Hello!"
         assert msg["role"] == "assistant"
         assert msg["mirror"] is True
@@ -222,12 +195,12 @@ class TestMirrorToSession:
 
         with patch.object(mirror_mod, "_SESSIONS_DIR", sessions_dir), \
              patch.object(mirror_mod, "_SESSIONS_INDEX", index_file), \
-             patch("gateway.mirror._append_to_sqlite"):
+             patch("gateway.mirror._append_to_sqlite") as mock_sqlite:
             result = mirror_to_session("telegram", "-1001", "Hello topic!", source_label="cron", thread_id="10")
 
         assert result is True
-        assert (sessions_dir / "sess_topic_a.jsonl").exists()
+        mock_sqlite.assert_called_once()
-        assert not (sessions_dir / "sess_topic_b.jsonl").exists()
+        assert mock_sqlite.call_args[0][0] == "sess_topic_a"
 
     def test_successful_mirror_uses_user_id_for_group_session(self, tmp_path):
         sessions_dir, index_file = _setup_sessions(tmp_path, {
@@ -245,7 +218,7 @@ class TestMirrorToSession:
 
         with patch.object(mirror_mod, "_SESSIONS_DIR", sessions_dir), \
              patch.object(mirror_mod, "_SESSIONS_INDEX", index_file), \
-             patch("gateway.mirror._append_to_sqlite"):
+             patch("gateway.mirror._append_to_sqlite") as mock_sqlite:
             result = mirror_to_session(
                 "telegram",
                 "-1001",
@@ -255,8 +228,8 @@ class TestMirrorToSession:
             )
 
         assert result is True
-        assert (sessions_dir / "sess_alice.jsonl").exists()
+        mock_sqlite.assert_called_once()
-        assert not (sessions_dir / "sess_bob.jsonl").exists()
+        assert mock_sqlite.call_args[0][0] == "sess_alice"
 
     def test_no_matching_session(self, tmp_path):
         sessions_dir, index_file = _setup_sessions(tmp_path, {})