[BUG] Session-to-project-group memberships silently dropped after app update; groups survive but sessions fall into Ungrouped

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Environment

• App: Claude Code desktop (macOS)
• Version when observed: 1.18286.0 (also present on prior 1.17377.2)
• OS: macOS 15.5 (Darwin 25.5.0)
• Account tier: Max
• Surface: reproduces identically in the desktop app and in claude.ai in a browser on the same account

Summary

After a routine app update and relaunch, my manually created named project groups lost most of their session memberships. The group definitions themselves survived and still render, but the sessions that were filed into them were emptied out into Ungrouped. This is not a rendering glitch: it renders the same in the desktop app and in the browser, which indicates the assignment state was lost server-side or in synced storage, not just failed to display on one client.

Steps to reproduce

1. Create several named project groups in the sidebar and assign multiple sessions into each by dragging.
2. Quit the app fully (Cmd+Q) and relaunch, or take an app update and relaunch.
3. Observe the sidebar.

Note: I cannot pin the exact trigger to update vs. relaunch, because the flattening was already present when I first reopened the app, and it persisted through both a clean quit/relaunch and a subsequent version update.

Expected behavior

Each session remains in the group it was assigned to across restarts and updates.

Actual behavior

• All group headers persist (in my case: Taxes, Career Work, Dad Claude, Operari Consulting, Get shit done).
• Most session-to-group assignments are gone. Two groups retained a single session each; three groups are now empty ("Drag or move sessions here").
• The previously grouped sessions now appear under Ungrouped.
• The sessions themselves are all intact; only the group membership was lost.

Diagnostics already performed

• All local session files are present and intact on disk under a single project directory. No session data was lost.
• A full quit and relaunch did not restore the memberships.
• Updating from 1.17377.2 to 1.18286.0 did not restore the memberships.
• The desktop app's local IndexedDB store (https_claude.ai_0) contains no project-grouping keys, and the only IndexedDB backup present is a ~5KB near-empty snapshot, so the state is not locally recoverable. This points to the membership data being lost from synced or account-side storage.
• The broken grouping renders identically in a browser, confirming account-level or synced state rather than a desktop-only cache issue.

Impact

Users who rely on manually created named project groups to organize many sessions lose their entire filing structure on update, with no local recovery path. Refiling must be done by hand, session by session, and is at risk of being wiped again on the next update.

Related

• Distinct from #53340, but likely shares a root cause. That issue reports the automatic working-directory project folders disappearing entirely (flat "Recents" list, no folders). This issue is different: manually created named project groups keep their headers but lose their assigned sessions to Ungrouped. #53340's reporter traced theirs to IndexedDB project-organization metadata not persisting through the app update; the same non-persistence would explain the membership loss here, so these may be two surface manifestations of one bug.
• Possibly related: #46393 (project folder and branch selection do not persist).

What Should Happen?

Each session should stay in the named project group it was assigned to, and that assignment should persist across app restarts and app updates. Group memberships should not be silently dropped by an update.

Error Messages/Logs

Steps to Reproduce

1. In the Claude Code desktop app sidebar, create several named project groups (e.g., "Taxes," "Career Work").
2. Assign multiple sessions into those groups by dragging them in.
3. Confirm the sessions show nested under their groups.
4. Take an app update (or fully quit with Cmd+Q and relaunch).
5. Reopen the app and view the sidebar.

Result: the group headers still appear, but most sessions have been removed from their groups and now sit under "Ungrouped."

Note: I could not isolate whether the trigger is the update specifically or the relaunch, because the flattening was already present the first time I reopened the app, and it then persisted through both a clean quit/relaunch and a subsequent version update (1.17377.2 to 1.18286.0).

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown exact version. Grouping was already broken on desktop app 1.17377.2 (the build installed before I updated), so the last working version predates 1.17377.2. I did not capture the version immediately prior to the update that introduced it.

Claude Code Version

Desktop app 1.18286.0 (bug also present on 1.17377.2). CLI: claude 2.1.198.

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

This is a desktop-app sidebar / session-organization bug, not a code-execution bug.
Key diagnostics:

• The broken grouping renders identically in the desktop app and in claude.ai in a browser on the same account, which points to synced or account-side state rather than a local desktop cache.
• The app's local IndexedDB store (https_claude.ai_0) contains no project-grouping keys, and the only IndexedDB backup present is a ~5KB near-empty snapshot, so there is no local recovery path.
• All session files remain intact on disk; only the session-to-group memberships were lost.
• A full quit/relaunch and a version update (1.17377.2 to 1.18286.0) both failed to restore the memberships.
• Likely shares a root cause with #53340 (IndexedDB project-organization metadata not persisting through the app update), though the surface symptom differs: #53340 is the automatic working-directory folders vanishing entirely, whereas this is manually created named groups keeping their headers but losing their assigned sessions.