Silent data loss: app update wiped all session conversation content (IndexedDB reset without backup, no user warning)

[bpc-oss]

Summary

A silent app update on 2026-06-09 destroyed all session conversation content. Session titles and metadata are still visible in the session list, but opening any session shows no content. There was no warning, no migration notice, and no recovery option.

Platform: Windows 11 Pro 10.0.26200
App version: 1.11847.5
Date of data loss: 2026-06-09
Sessions affected: 20 sessions spanning 2026-05-16 to 2026-06-12

What happened

The app update on 2026-06-09 created .bak.20260609-* backups of all Electron/Chromium storage directories and then re-initialized them. The app_localhost_0.indexeddb.leveldb database (which stores session conversation content in the desktop app UI) was reset to an empty skeleton — only 969 bytes, no actual data.

Evidence: .bak directories created during the update

%APPDATA%\Claude\
  Cache.bak.20260609-112709             (created 2026-06-08 22:54)
  Code Cache.bak.20260609-112709        (created 2026-06-08 22:54)
  IndexedDB.bak.20260609-112916         (created 2026-06-08 22:55)
  Local Storage.bak.20260609-112916     (created 2026-06-08 22:54)
  Network.bak.20260609-112916           (created 2026-06-09 11:27)
  Session Storage.bak.20260609-112916   (created 2026-06-09 11:27)
  WebStorage.bak.20260609-112916        (created 2026-06-08 22:54)

Evidence: IndexedDB backup contains claude.ai data but NOT app_localhost data

IndexedDB.bak.20260609-112916\
  https_claude.ai_0.indexeddb.leveldb\   <- backed up (000004.log = 1,045,383 bytes)
  (NO app_localhost_0.indexeddb.leveldb) <- MISSING from backup — was wiped without backup

Evidence: Current app_localhost IndexedDB is essentially empty

IndexedDB\app_localhost_0.indexeddb.leveldb\
  000003.log   969 bytes   (2026-06-09 18:15)  <- empty skeleton, no data
  CURRENT       16 bytes
  LOCK           0 bytes
  LOG          307 bytes
  MANIFEST-000001  23 bytes

Compare: the https_claude.ai backup has a 000004.log of 1,045,383 bytes — over 1MB of actual conversation data.

Impact

Session conversation content is stored in two systems:

Storage	Content	Status
%APPDATA%\Claude\claude-code-sessions\	Session metadata (title, cwd, timestamps)	INTACT — 20 sessions visible
~/.claude/projects//.jsonl	Conversation JSONL files	PARTIAL — only 4 of 20 project dirs exist
IndexedDB\app_localhost_0	UI-side session content cache	WIPED to empty

Only 4 of 20 sessions have .jsonl files on disk. The other 16+ sessions have no recoverable content anywhere.

Projects with content still on disk (4):

• E:\AI XIAOSHUO — 282,483 bytes JSONL
• E:\ai-files\APP develop team
• E:\ai-files\Bobby
• E:\ai-files\Academic Research

Projects with content permanently lost (16+):

• D:\孔雀结题, E:\ai-files\freqtrade, E:\ai-files\In silico gut microbiota fermertion simulation, E:\ai-files\In silico digestion, E:\ai-files\Dry-lab, E:\ai-files\Literature Search, C:\Users\Administrator\Desktop, C:\Users\Administrator\Documents\New project, E:\ai-studio-bundle, plus multiple git worktree sessions

Root cause (hypothesis)

The update migration script backed up and reset Chromium-layer storage directories but:

1. Did NOT back up app_localhost_0.indexeddb.leveldb (only backed up https_claude.ai_0)
2. Did NOT migrate existing session content from the old IndexedDB into the new one
3. Did NOT warn the user that conversation history would be affected
4. .jsonl files in ~/.claude/projects/ only exist for recently active projects — older sessions have no local file fallback at all

Expected behavior

• App updates should never silently destroy user data
• If a data migration is required, the user should be warned before the update proceeds
• If conversation history cannot be migrated, the user should be offered an export option first
• app_localhost_0.indexeddb.leveldb should be included in the same backup as https_claude.ai_0.indexeddb.leveldb

Requested actions

1. Investigate whether the 2026-06-09 update migration had a bug that excluded app_localhost_0 from the backup
2. Check if other Windows users were affected by this update
3. Add a pre-update export/warning mechanism for session conversation history
4. Write .jsonl files for ALL sessions (not just active project dirs) so there is always a local fallback

[github-actions]

Found 3 possible duplicate issues:

1. [BUG] Session data lost after app update — "디스크에서 세션을 찾을 수 없음" #66775
2. [BUG] Windows: Claude Code Desktop app shows sessions in sidebar but all message content missing after auto-update — content not persisted to claude-code-sessions JSONL files #53717
3. [BUG] Auto-update DELETES sessiondata.vhdx — all Cowork projects, tasks and conversations destroyed (data loss, 2nd incident in 4 days, forensic evidence) #66997

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