Anthropic Cowork feature creates 10GB VM bundle on macOS without warning

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 (10GB)

The cowork feature creates a VM bundle at:

~/Library/Application Support/Claude/vm_bundles/claudevm.bundle/rootfs.img

This file grows to 10GB and is never cleaned up. It regenerates quickly after deletion (deleted one day, back to 10GB the next).

Cleanup Test Results

Deleted vm_bundles, Cache, and Code Cache directories (reduced from 11GB to 639MB).

Result: ~75% faster immediately after cleanup on tasks that previously failed/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 at 24%, main at 21%, GPU at 7%)
• Swap activity increases (swapins climbing from 20K to 24K+)

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)
• 8GB system RAM

Observed Behavior

• High CPU at idle (~24-55% combined across processes)
• Heavy swap activity that increases over time
• Performance degrades within minutes of use
• 10GB 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:

rm -rf ~/Library/Application\ Support/Claude/vm_bundles
rm -rf ~/Library/Application\ Support/Claude/Cache
rm -rf ~/Library/Application\ Support/Claude/Code\ Cache

Provides ~75% improvement but degrades again over time. Must restart periodically.

Expected Behavior

• Stable CPU usage that doesn't degrade over time
• VM bundles cleaned up after cowork sessions
• Usable performance on 8GB RAM systems

Filed via Claude Code