Sidebar session groups/pins stop rendering after restart (backend data intact, confirmed via list_sessions)

Summary

The sidebar's custom session organization (groups/categories and pinned sessions) stops rendering correctly in the desktop app UI, even though the underlying data is fully intact on the backend. This has now happened three times and is not fixed by fully quitting and restarting the app.

Environment

• App: Claude desktop app (Windows)
• Version: 1.40609.1 (from config.json updaterLastSeenVersion / version_first_launch)
• OS: Windows 11 Pro 10.0.26100
• Locale: de-DE

Impact

The affected user has organized ~6 months of work (22 custom project groups, each containing multiple sessions) using the sidebar's group/pin features as their primary navigation system across many parallel projects. When this bug occurs, all of that visible organization appears to vanish from the UI, which reads as catastrophic data loss even though it is not.

Incidents

1. 2026-08-23: User noticed sidebar entries appeared shuffled/reorganized (moved entries, changed pins).
2. 2026-09-03, ~18:00: Same symptom recurred — all project categories/pins visually gone from the sidebar.
3. 2026-09-03, later same day: Recurred again. This time, fully closing the app (verified no lingering process) and restarting did NOT restore correct display.

Diagnosis so far

On each occurrence, we queried the session-management MCP tool (list_sessions) available to Claude Code sessions, which reads session metadata directly (not through the sidebar rendering layer). Every time, the group ({id, name}) and pinned fields for every session were fully intact and correct — all 22 groups present with their correct sessions, correct pin states, no renamed/lost groups.

This strongly suggests the bug is in the sidebar rendering/hydration logic on the client, not in the underlying stored data: the correct data is being fetched successfully (as proven by the MCP tool reading it correctly), but the sidebar UI fails to reflect it — and this failure now survives a full application restart, ruling out a simple in-memory cache issue.

We inspected %APPDATA%\Claude\ (config.json, Cache, IndexedDB, Local Storage, Session Storage, fcache) looking for an obvious stale local cache to clear, but found nothing we could confidently identify as the cause or safely clear without risking unrelated state (login, other settings).

Request

Please investigate the sidebar's group/pin hydration path for a rendering bug that can leave it stuck showing stale/empty state even after a full restart, while the actual session metadata (verifiable via the session-management MCP tool) remains correct. Given the impact on long-term project navigation, this would be great to prioritize.

Happy to provide more diagnostic detail if useful.