[Bug] Cowork VM sandbox disk exhaustion: yes.exe output unbounded to VHDX without size limits
Status Open
Reported on v2.1.278
Maintainer reply None cached
Activity 0 comments · opened Sep 20, 2026
Bug Description
bug | Area: Cowork VM sandbox (desktop app)
Details:
- What happened: System froze; yes.exe (Git-for-Windows MSYS2) ran with no manual invocation, wrote continuously until C: free space dropped from 20GB to 5-6GB (~14GB). No matching flat file found on host filesystem by extension/size/timestamp search.
- What the user said: "my system froze and yes.exe launched completely on its own in the background... continuously wrote data to disk... dropping my C: drive free space from 20GB down to 5-6GB." Then: "ur a agent, find out what happened for me."
- Repro: CoworkVMService (DisplayName "Claude", LocalSystem, cowork-svc.exe) installed/started at incident time. Boots Linux micro-VM (vmlinuz+initrd via Hyper-V vmcompute), root filesystem backed by dynamically-expanding rootfs.vhdx at %LOCALAPPDATA%\Packages\Claude_<pkg>\LocalCache\Roaming\Claude\vm_bundles\claudevm.bundle\rootfs.vhdx. VHDX write timestamps matched incident window (7.6GB now, after apparent auto-recovery already trimmed it). yes.exe LastAccessTime matched same window — yes ran inside a Cowork VM session, redirected to a file, and the VM's disk growth showed up on host as VHDX growth — invisible to normal big-file search since it's a virtual disk image, not a flat dump.
- Evidence: Service CoworkVMService, binary C:\Program Files\WindowsApps\Claude_2.2553.1.0_x64__pzs8sxrjxfjjc\app\resources\cowork-svc.exe; event log 2026-09-20 15:09:49-15:09:50 (service install/start), 15:11:17-15:11:28 (rootfs.vhdx + .origin rewrites); yes.exe LastAccessTime 15:13:54.
- Cause: Not fully confirmed (VM session contents gone after reset) but strongly indicated — agent/Cowork task inside sandbox ran yes redirected to a file instead of piped to a consumer, and the VHDX had no apparent size cap, letting it balloon before something reset the bundle.
Environment Info
- Platform: win32
- Terminal: null
- Version: 2.1.278
- Feedback ID: cb65f8a3-db37-456a-b309-4acb493c7cbd
Errors
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