fix: preserve imported session lineage visibility

tests/test_session_import_cli_fallback_model.py

@@ -90,6 +90,7 @@ def test_session_import_cli_refresh_matches_messages_despite_timestamp_type_diff
             self.raw_source = "weixin"
             self.session_source = "messaging"
             self.source_label = "WeChat"
+            self.parent_session_id = None
 
         def compact(self):
             return {"session_id": session_id, "title": "Imported"}
@@ -141,6 +142,7 @@ def test_session_import_cli_refresh_rejects_prefix_if_non_timing_content_diverge
             self.session_source = "messaging"
             self.source_label = "Telegram"
             self.is_cli_session = True
+            self.parent_session_id = None
 
         def compact(self):
             return {"session_id": session_id, "title": "Imported"}
@@ -169,3 +171,113 @@ def test_session_import_cli_refresh_rejects_prefix_if_non_timing_content_diverge
     assert response["session"]["messages"] == existing.messages
     assert existing.messages[0]["content"] == "old-prefix"
     assert save_calls == []
+
+
+def test_session_import_cli_preserves_parent_metadata_on_existing_import(monkeypatch):
+    """Refreshing an already-imported CLI session must persist lineage metadata."""
+    import api.routes as routes
+
+    session_id = "existing_parent_lineage_001"
+    parent_id = "root_parent_lineage_001"
+
+    class FakeSession:
+        def __init__(self):
+            self.messages = [{"role": "user", "content": "hello", "timestamp": 1.0}]
+            self.source_tag = "telegram"
+            self.raw_source = "telegram"
+            self.session_source = "messaging"
+            self.source_label = "Telegram"
+            self.parent_session_id = None
+            self.is_cli_session = True
+
+        def compact(self):
+            return {"session_id": session_id, "title": "Imported", "parent_session_id": self.parent_session_id}
+
+        def save(self, touch_updated_at=False):
+            save_calls.append(touch_updated_at)
+
+    save_calls = []
+    existing = FakeSession()
+
+    monkeypatch.setattr(routes.Session, "load", classmethod(lambda _cls, sid: existing if sid == session_id else None))
+    monkeypatch.setattr(routes, "require", lambda body, *keys: None)
+    monkeypatch.setattr(routes, "j", lambda _handler, payload, status=200, extra_headers=None: payload)
+    monkeypatch.setattr(routes, "get_cli_session_messages", lambda sid: existing.messages if sid == session_id else [])
+    monkeypatch.setattr(
+        routes,
+        "get_cli_sessions",
+        lambda: [{
+            "session_id": session_id,
+            "source_tag": "telegram",
+            "raw_source": "telegram",
+            "session_source": "messaging",
+            "source_label": "Telegram",
+            "parent_session_id": parent_id,
+        }],
+    )
+
+    response = routes._handle_session_import_cli(object(), {"session_id": session_id})
+
+    assert response["imported"] is False
+    assert existing.parent_session_id == parent_id
+    assert response["session"]["parent_session_id"] == parent_id
+    assert save_calls == [False]
+
+
+def test_read_only_import_payload_includes_parent_session_id(monkeypatch):
+    """Read-only CLI/session imports should also expose lineage in the payload."""
+    import api.routes as routes
+
+    session_id = "readonly_parent_lineage_001"
+    parent_id = "readonly_root_lineage_001"
+    messages = [{"role": "user", "content": "hello", "timestamp": 1.0}]
+
+    monkeypatch.setattr(routes.Session, "load", classmethod(lambda _cls, sid: None))
+    monkeypatch.setattr(routes, "require", lambda body, *keys: None)
+    monkeypatch.setattr(routes, "bad", lambda _handler, msg, status=400: {"ok": False, "error": msg, "status": status})
+    monkeypatch.setattr(routes, "j", lambda _handler, payload, status=200, extra_headers=None: payload)
+    monkeypatch.setattr(routes, "get_cli_session_messages", lambda sid: messages if sid == session_id else [])
+    monkeypatch.setattr(
+        routes,
+        "get_cli_sessions",
+        lambda: [{
+            "session_id": session_id,
+            "title": "Read-only child",
+            "model": "test-model",
+            "created_at": 1.0,
+            "updated_at": 2.0,
+            "source_tag": "discord",
+            "raw_source": "discord",
+            "session_source": "messaging",
+            "source_label": "Discord",
+            "parent_session_id": parent_id,
+            "read_only": True,
+        }],
+    )
+
+    response = routes._handle_session_import_cli(object(), {"session_id": session_id})
+
+    assert response["imported"] is False
+    assert response["session"]["parent_session_id"] == parent_id
+    assert response["session"]["messages"] == messages
+
+
+def test_merge_cli_sidebar_metadata_keeps_larger_sidecar_message_count():
+    """Sidebar metadata merge should not shrink repaired aggregate sidecar counts."""
+    import api.routes as routes
+
+    merged = routes._merge_cli_sidebar_metadata(
+        {"session_id": "sid", "message_count": 535, "title": "Recovered"},
+        {"session_id": "sid", "message_count": 407, "source_tag": "discord"},
+    )
+
+    assert merged["message_count"] == 535
+
+
+def test_messaging_session_loader_prefers_longer_sidecar_transcript():
+    """Pin the /api/session invariant that repaired sidecars can be longer than state.db segments."""
+    handler = _extract_handler("handle_get")
+    old = "if is_messaging_session and cli_messages:\n                    _all_msgs = cli_messages"
+    assert old not in handler
+    assert "sidecar_messages = getattr(s, \"messages\", []) or []" in handler
+    assert "len(sidecar_messages) > len(cli_messages)" in handler