Claude Desktop (Windows, Store package) app window exits silently while a session idles with background subagents; no crash dump, no event-log entry

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

• Claude desktop app 1.40609.1 (Microsoft Store / MSIX package), bundled Claude Code 2.1.255, unchanged before and after
• Windows 11 Home 10.0.26200, 16 GB RAM, ~3.4 GB free at the time of inspection
• Model in the affected session: claude-fable-5-1
• Command hooks configured (PreToolUse, UserPromptSubmit, Stop, SessionStart), python scripts, 5-10 s timeouts on most

What happened

On 2026-09-02 at roughly 22:19-22:22 UTC the desktop app window disappeared with no error dialog, no "not responding" state, and no crash dump. Session child processes (claude.exe) were left running orphaned; the user killed them and relaunched the app from the taskbar at 22:23:25 UTC (Electron parent process created 22:23:25, parent explorer.exe). The same session then resumed (SessionStart source=resume, first record 22:23:35 UTC). A second interactive session in the same app instance was lost at the same time and resumed 12 s later.

Affected session id: c0d1e541-587d-4d3d-aa7c-26b8229ed7df.

(An earlier exit the same afternoon, ~21:37-21:50 UTC, coincided with a manual Windows restart at 21:49:25 UTC and is not part of this report.)

Session state at the exit (from the .jsonl)

• Last assistant text 22:19:00 UTC: the model said it would idle until its background workers reported.
• Last record 22:19:01.712 UTC: Stop hook success, exit 0. Every Stop hook exited 0.
• 3 background subagents (Agent tool, run_in_background: true; two Opus, one Sonnet) were in flight. Another background subagent had been stopped at ~22:15 UTC. A fourth (Haiku) completed just before.
• No further records of any kind after 22:19:01 (no hook, no queue-operation, no user input) until the resume at 22:23:35.
• All in-flight subagents were lost; the SessionStart hook on resume reported them as outstanding.

Ruled out

• Windows Application/System logs 22:10-22:30 UTC: no 1000/1001/1002 for any image, no 1074/6005/6006/6008/41, no Resource-Exhaustion 2004, no RestartManager, no MSI/AppX deployment events. Win32_ReliabilityRecords: nothing in the window.
• Crashpad (%LOCALAPPDATA%\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\Crashpad): reports, pending, completed all empty; metadata touched only at relaunch. The app's own logs\ folder was last written 2026-08-20.
• Auto-update: Store package version identical before and after; no AppX deployment events; no side-by-side package.
• Defender: no detections (Get-MpThreatDetection empty).
• Our own automation: no scheduled task or script killed Claude processes before the exit; a settings.json hooks edit at 22:20:30 UTC is after the last transcript record, and docs say settings edits hot-reload.
• Nothing was written to the app's data directory between 22:19 and 22:23 UTC.

What Should Happen?

The desktop app stays open, or leaves a crash dump / event-log entry / debug log when it exits.

Error Messages/Logs

None captured — no error dialog, crash dump, or Windows event-log entry was produced. See "Ruled out" above for everything checked (Crashpad reports/pending/completed all empty, no relevant Application/System event IDs, no Defender detections).

Steps to Reproduce

Not deterministic; occurred while the main session idled with 3 background subagents running (see body).

Claude Model

Other

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.255 (desktop app 1.40609.1)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

Ask:

1. What would make the desktop app's main process exit with no dump and no event-log entry while a session idles with background subagents running?
2. Is there a way to enable persistent debug logging for sessions started from the desktop app (equivalent to claude --debug / CLAUDE_CODE_DEBUG_LOGS_DIR), so the next occurrence leaves a trace?
3. Is there a known 2.1.25x issue involving background subagents being stopped or completing while the parent session is idle?

Happy to provide the session .jsonl privately.