Claude Desktop writes 8-13 GB to disk in under an hour, causing system-wide performance degradation

Environment

• Claude Desktop: v1.569.0 (also reproduced on v1.1.9310)
• macOS: 26.4 (25E246)
• Hardware: MacBook Pro M5, 24 GB RAM, 926 GB SSD (524 GB free)

Summary

Claude Desktop (com.anthropic.claudefordesktop) writes extreme amounts of data to disk during normal use, triggering macOS diagnostic reports and cascading system-wide performance issues. The system feels like it's panicking — UI lag, beachballs, and general unresponsiveness — despite 89% free memory and zero swap usage.

Evidence

Claude Desktop disk write diagnostics (all from a single night):

| Timestamp | Disk Writes | Duration | Write Rate | App Version |
|-----------|------------|----------|------------|-------------|
| 2026-04-04 03:22 | 2.1 GB | 16 min | 2.2 MB/s | v1.1.9310 |
| 2026-04-04 03:37 | ~2 GB | ~15 min | ~2 MB/s | v1.569.0 |
| 2026-04-04 04:04 | 8.6 GB | 27 min | 5.2 MB/s | v1.569.0 |

Total: ~13 GB of disk writes in under 1 hour.

macOS flagged all three as exceeding the system disk write limit (threshold: ~99 KB/s over 86400s; Claude was writing at 2,000-5,000 KB/s sustained).

Heaviest stack trace (from all 3 reports):

thread_start (libsystem_pthread.dylib)
  _pthread_start (libsystem_pthread.dylib)
    uv_cancel (Electron Framework + 43127800)
      write (libsystem_kernel.dylib)

The writes originate from libuv's I/O thread pool inside Electron, calling kernel write() syscalls.

On-disk footprint:

14 GB   ~/Library/Application Support/Claude/
├── 13 GB   vm_bundles/claudevm.bundle/
├── 941 MB  vm_bundles/warm/
├── 809 MB  Cache/
├── 218 MB  claude-code-vm/
├── 188 MB  claude-code/
└── 85 MB   Code Cache/

vm_bundles/ alone is 13 GB and appears to be the primary write target.

Cascading system effects:

The excessive writes trigger secondary issues that compound the performance degradation:

1. APFS daemon (apfsd) — 4 CPU resource violations in 2 days, hitting 76% CPU for 2+ minutes per incident. The filesystem daemon is struggling to keep up with write volume.

1. Spotlight (spotlightknowledged) — 6 CPU spikes in one week, triggered by attempting to index the rapidly changing Claude data directory.

1. suggestd — 5 CPU spikes in one week, same indexing cascade.

1. 9 system-level "disk writes" diagnostic reports generated in 8 days — macOS itself considers this write volume abnormal.

System resources are NOT the bottleneck:

• Memory: 89% free at time of diagnostics
• Swap: 0 bytes used
• Disk: 524 GB free (56% of total)
• Thermal: No thermal pressure

Impact

The system becomes sluggish and unresponsive during Claude Desktop use, requiring force-restarts. The user perceives this as system crashes/panics. The issue is reproducible across multiple Claude Desktop versions (tested v1.1.9310 and v1.569.0).

Workarounds applied

1. Excluding ~/Library/Application Support/Claude/ from Spotlight indexing
2. Periodically clearing vm_bundles/warm/ (941 MB, regenerates on launch)
3. Preferring Claude Code CLI over Desktop app for heavy sessions

Expected behavior

Claude Desktop should not write 8+ GB to disk in a 27-minute session. The vm_bundles/ directory should not accumulate 13 GB of data. Disk write rates should stay within macOS's acceptable thresholds for background processes.

Diagnostic files available

All three .diag files from /Library/Logs/DiagnosticReports/ are available if needed:

• Claude_2026-04-04-032223_Bashs-MacBook-Pro.diag
• Claude_2026-04-04-033722_Bashs-MacBook-Pro.diag
• Claude_2026-04-04-040449_Bashs-MacBook-Pro.diag