Regression: sessions >30 days old lost history again after forced re-sign-in (previously fixed in 1.34493.0)

Describe the bug
Local Claude Code session transcripts for several projects (user reports ~8) disappeared from the desktop app sidebar, apparently triggered by a forced re-sign-in. Only the most recently active project's session survived. This looks like a regression of a bug that was already fixed once.

This looks like a regression of a previously-fixed bug
The August 20, 2026 changelog (v1.34493.0) lists this exact fix:

"Fixed sessions you hadn't opened for 30 days or more losing their conversation history even though the app was in regular use."

That is precisely the reported symptom: projects untouched for 30+ days lost their history while the app was in active daily use for a different (recent) project.

Likely trigger: forced re-sign-in
The September 17, 2026 changelog (v2.2553.0) lists:

"Fixed turns failing with 'OAuth token has expired' hours into a session; the token is now renewed in the background, and when a fresh sign-in is genuinely required the app asks before sending and keeps your message."

The user was forced to re-sign in to the desktop app this morning, immediately after which the old sessions were gone. This suggests the re-auth flow itself (or a related code path) re-triggered the class of bug the August fix addressed, rather than that fix being durable.

Forensic evidence gathered directly on the affected machine

• ~/.claude/.last-cleanup is timestamped 2026-09-18T22:06:27.146Z (= 2026-09-19 08:06 local AEST), matching the user's report of the re-sign-in / disappearance happening around 8:05am local time.
• The ~/.claude directory itself (not just its contents) has a filesystem creation timestamp of 2026-09-19 08:06:15 local — i.e. it did not exist before that moment on this machine's disk. This is not "old files were cleaned out"; the whole directory was recreated from scratch at that instant.
• ~/.claude.json (the top-level project registry, separate from the ~/.claude directory) still lists 3 project paths, but on disk ~/.claude/projects/ now only contains a directory (with .jsonl transcripts) for ONE of them — the one actively used yesterday evening. The other two registered projects have no transcript directory at all.
• Local APFS snapshots were checked going back to September 7 (the oldest available on this machine) via mount_apfs -s <snapshot> -o ro /dev/disk3s5 <mountpoint>. The ~/.claude directory is absent in every one of these snapshots, including ones from well before this morning (yesterday 6:03pm, yesterday 7:53am, and September 7th). tmutil isexcluded confirms the path is not Time-Machine-excluded. This means either (a) the directory has never persisted locally for more than a very short window before being wiped again, or (b) something is actively preventing this directory's contents from surviving across whatever event happens at sign-in/session-expiry boundaries.
• Actual project files unrelated to Claude Code (docs, csvs, etc.) on disk are untouched — this is chat-history loss only, not file loss.

Expected behavior
Per the intent of the August 20 fix, sessions should not lose their history regardless of how long they've been idle, and a forced/renewed sign-in should never cause local session data to be wiped or recreated from scratch.

Actual behavior
Multiple projects' full session/transcript history vanished, coincident with a forced re-sign-in, in a way that matches a previously-fixed bug.

Environment

• Claude Desktop app, Code tab
• macOS 14.0 (Build 23A344), Darwin 23.0.0
• No ~/.claude/settings.json existed prior to this (cleanupPeriodDays was at its default of 30, desktopSessionCleanupPeriodDays at its default of 0/no-ceiling — neither should have caused this given the directory's own creation timestamp postdates any plausible sweep)

Impact
Permanent loss of Claude conversation history for multiple long-running projects (~8) the user relied on for continuity/context, some clearly over 30 days old, lost right after a forced re-authentication.

Start with the forced re-sign-in flow and session cleanup or persistence paths, comparing the fixes documented in v1.34493.0 and v2.2553.0. Inspect ~/.claude, ~/.claude.json, ~/.claude/.last-cleanup, and the project transcript directories, then reproduce re-authentication with sessions idle for over 30 days. Done means old project transcripts remain available after sign-in.