feat(webui): add lightweight session messaging via mentions

tests/webui/test_session_list_index.py

@@ -80,6 +80,44 @@ def test_webui_session_index_uses_unique_temp_file(tmp_path: Path) -> None:
     assert not list(manager.sessions_dir.glob(".webui_session_index.json.*.tmp"))
 
 
+def test_webui_session_index_v7_rebuilds_session_handle_addressability(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    manager = SessionManager(tmp_path)
+    session = manager.get_or_create("websocket:upgrade")
+    session.metadata["webui"] = True
+    session.add_message("user", "upgrade me")
+    manager.save(session)
+    list_webui_sessions(manager)
+    index_path = manager.sessions_dir / ".webui_session_index.json"
+    stale = json.loads(index_path.read_text(encoding="utf-8"))
+    stale["version"] = 7
+    for row in stale["sessions"]:
+        row.pop("_persisted_webui", None)
+    index_path.write_text(json.dumps(stale), encoding="utf-8")
+    scanned: list[str] = []
+    original_scan = session_list_index._scan_session_row
+
+    def record_scan(
+        session_manager: SessionManager,
+        path: Path,
+        webui_dir: Path,
+    ) -> dict | None:
+        scanned.append(path.name)
+        return original_scan(session_manager, path, webui_dir)
+
+    monkeypatch.setattr(session_list_index, "_scan_session_row", record_scan)
+
+    [row] = list_webui_sessions(manager)
+
+    assert scanned == [manager._get_session_path(session.key).name]
+    assert session_list_index.is_persisted_webui_session_row(row)
+    rebuilt = json.loads(index_path.read_text(encoding="utf-8"))
+    assert rebuilt["version"] == 8
+    assert rebuilt["sessions"][0]["_persisted_webui"] is True
+
+
 def test_webui_session_list_indexes_workspace_scope_and_preserves_null(
     tmp_path: Path,
 ) -> None:
@@ -352,6 +390,7 @@ def test_webui_session_list_recovers_transcript_without_canonical_session(
     assert row["key"] == key
     assert row["preview"] == "original question"
     assert row["created_at"] == datetime.fromtimestamp(1785502800).isoformat()
+    assert not session_list_index.is_persisted_webui_session_row(row)
     assert not manager._get_session_path(key).exists()
     assert manager.list_sessions() == []
 
@@ -359,6 +398,22 @@ def test_webui_session_list_recovers_transcript_without_canonical_session(
     assert [row["key"] for row in list_webui_sessions(reloaded)] == [key]
 
 
+def test_webui_session_list_marks_only_canonical_webui_sessions_addressable(
+    tmp_path: Path,
+) -> None:
+    manager = SessionManager(tmp_path / "workspace")
+    webui = manager.get_or_create("websocket:webui")
+    webui.metadata["webui"] = True
+    manager.save(webui)
+    plain = manager.get_or_create("websocket:plain")
+    manager.save(plain)
+
+    rows = {row["key"]: row for row in list_webui_sessions(manager)}
+
+    assert session_list_index.is_persisted_webui_session_row(rows["websocket:webui"])
+    assert not session_list_index.is_persisted_webui_session_row(rows["websocket:plain"])
+
+
 def test_webui_session_list_recovers_colon_chat_id_from_transcript(
     tmp_path: Path,
     monkeypatch: pytest.MonkeyPatch,