refactor(webui): keep sidebar index out of session manager

tests/agent/test_session_manager_history.py

@@ -96,48 +96,6 @@ def test_list_sessions_bounds_preview_scan(tmp_path):
     assert rows[0]["preview"] == "assistant trace 0"
 
 
-def test_list_sessions_reuses_valid_index_without_scanning_files(tmp_path, monkeypatch):
-    manager = SessionManager(tmp_path)
-    session = manager.get_or_create("websocket:indexed")
-    session.add_message("user", "indexed preview")
-    manager.save(session)
-
-    assert manager.list_sessions()[0]["preview"] == "indexed preview"
-
-    def fail_scan(path):
-        raise AssertionError(f"unexpected session file scan: {path}")
-
-    monkeypatch.setattr(manager, "_session_index_row_from_file", fail_scan)
-
-    rows = manager.list_sessions()
-
-    assert rows[0]["key"] == "websocket:indexed"
-    assert rows[0]["preview"] == "indexed preview"
-
-
-def test_list_sessions_index_updates_on_save_and_delete(tmp_path, monkeypatch):
-    manager = SessionManager(tmp_path)
-    session = manager.get_or_create("websocket:index-refresh")
-    session.add_message("user", "before")
-    manager.save(session)
-    session.messages.clear()
-    session.add_message("user", "after")
-    session.metadata["title"] = "fresh title"
-    manager.save(session)
-
-    def fail_scan(path):
-        raise AssertionError(f"unexpected session file scan: {path}")
-
-    monkeypatch.setattr(manager, "_session_index_row_from_file", fail_scan)
-
-    rows = manager.list_sessions()
-    assert rows[0]["title"] == "fresh title"
-    assert rows[0]["preview"] == "after"
-
-    assert manager.delete_session("websocket:index-refresh") is True
-    assert manager.list_sessions() == []
-
-
 # --- Original regression test (from PR 2075) ---
 
 def test_get_history_drops_orphan_tool_results_when_window_cuts_tool_calls():

tests/channels/test_websocket_channel.py

@@ -2618,15 +2618,16 @@ def test_parse_envelope_rejects_legacy_and_garbage() -> None:
     assert _parse_envelope('{"type":123}') is None
 
 
-def test_sessions_list_includes_active_run_started_at() -> None:
+def test_sessions_list_includes_active_run_started_at(monkeypatch) -> None:
     from websockets.datastructures import Headers
     from websockets.http11 import Request
 
     from nanobot.session import webui_turns as wth
+    from nanobot.webui import ws_http as ws_http_module
 
     bus = MagicMock()
     session_manager = MagicMock()
-    session_manager.list_sessions.return_value = [
+    sessions = [
         {
             "key": "websocket:chat-1",
             "created_at": "2026-05-19T10:00:00Z",
@@ -2641,6 +2642,7 @@ def test_sessions_list_includes_active_run_started_at() -> None:
             "updated_at": "2026-05-19T10:01:00Z",
         },
     ]
+    monkeypatch.setattr(ws_http_module, "list_webui_sessions", lambda _session_manager: sessions)
     channel = WebSocketChannel(
         {"enabled": True, "allowFrom": ["*"]},
         bus,

tests/webui/test_session_list_index.py

@@ -0,0 +1,75 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+import nanobot.webui.session_list_index as session_list_index
+from nanobot.session.manager import SessionManager
+
+
+def test_webui_session_list_reuses_valid_index_without_scanning_files(
+    tmp_path: Path,
+    monkeypatch,
+) -> None:
+    manager = SessionManager(tmp_path)
+    session = manager.get_or_create("websocket:indexed")
+    session.add_message("user", "indexed preview")
+    manager.save(session)
+
+    assert list_webui_sessions(manager)[0]["preview"] == "indexed preview"
+
+    def fail_scan(session_manager: SessionManager, path: Path) -> None:
+        raise AssertionError(f"unexpected session file scan: {path}")
+
+    monkeypatch.setattr(session_list_index, "_scan_session_row", fail_scan)
+
+    rows = list_webui_sessions(manager)
+
+    assert rows[0]["key"] == "websocket:indexed"
+    assert rows[0]["preview"] == "indexed preview"
+
+
+def test_webui_session_list_rescans_only_changed_file(tmp_path: Path, monkeypatch) -> None:
+    manager = SessionManager(tmp_path)
+    first = manager.get_or_create("websocket:first")
+    first.add_message("user", "first")
+    manager.save(first)
+    second = manager.get_or_create("websocket:second")
+    second.add_message("user", "second before")
+    manager.save(second)
+
+    assert {row["preview"] for row in list_webui_sessions(manager)} == {"first", "second before"}
+
+    second.messages.clear()
+    second.add_message("user", "second after")
+    manager.save(second)
+
+    original_scan = session_list_index._scan_session_row
+    scanned: list[str] = []
+
+    def record_scan(session_manager: SessionManager, path: Path) -> dict | None:
+        scanned.append(path.name)
+        return original_scan(session_manager, path)
+
+    monkeypatch.setattr(session_list_index, "_scan_session_row", record_scan)
+
+    rows = list_webui_sessions(manager)
+
+    assert scanned == [manager._get_session_path("websocket:second").name]
+    assert {row["preview"] for row in rows} == {"first", "second after"}
+
+
+def test_webui_session_list_drops_deleted_index_rows(tmp_path: Path) -> None:
+    manager = SessionManager(tmp_path)
+    session = manager.get_or_create("websocket:deleted")
+    session.add_message("user", "gone")
+    manager.save(session)
+
+    assert list_webui_sessions(manager)[0]["key"] == "websocket:deleted"
+
+    assert manager.delete_session("websocket:deleted") is True
+
+    assert list_webui_sessions(manager) == []
+
+
+def list_webui_sessions(manager: SessionManager) -> list[dict]:
+    return session_list_index.list_webui_sessions(manager)