Anthropic Cowork feature creates 10GB VM bundle on macOS without warning
Source: Hacker News
Description
After using the cowork feature, Claude Desktop becomes extremely slow—slow startup, UI lag, and slow responses. Performance degrades over time even during a single session.
Investigation
VM Bundle (10 GB)
The cowork feature creates a VM bundle at:
~/Library/Application Support/Claude/vm_bundles/claudevm.bundle/rootfs.imgThis file grows to 10 GB and is never cleaned up. It regenerates quickly after deletion (deleted one day, back to 10 GB the next).
Cleanup Test Results
Deleted vm_bundles, Cache, and Code Cache directories (reduced from 11 GB to 639 MB).
Result: ~75 % faster immediately after cleanup on tasks that previously failed or hung.
Performance Degradation Over Time
Even after cleanup (VM bundle at 0 bytes), performance degrades within minutes:
- Immediately after restart: ~24 % CPU at idle
- After several minutes of use: ~55 % CPU (renderer 24 %, main 21 %, GPU 7 %)
- Swap activity increases (swap‑ins climbing from 20 K to 24 K+)
This suggests a memory leak or accumulating work that causes degradation regardless of VM bundle state.
Environment
- macOS (Darwin 25.2.0)
- Claude Desktop (latest)
- 8 GB system RAM
Observed Behavior
- High CPU usage at idle (~24–55 % combined across processes)
- Heavy swap activity that increases over time
- Performance degrades within minutes of use
- 10 GB VM bundle regenerates after every cowork session
- Tasks that failed before cleanup now complete (75 % faster initially)
Workaround
Quit Claude Desktop and delete the VM bundle and related caches:
rm -rf ~/Library/Application\ Support/Claude/vm_bundles
rm -rf ~/Library/Application\ Support/Claude/Cache
rm -rf ~/Library/Application\ Support/Claude/Code\ CacheProvides ~75 % improvement but degrades again over time. Periodic restarts are required.
Expected Behavior
- Stable CPU usage that doesn’t degrade over time
- VM bundles cleaned up after cowork sessions
- Usable performance on 8 GB RAM systems