claude cowork: VM process spins CPU indefinitely on macOS 26.3 (Apple M5)

Description

claude cowork fails to start. The underlying com.apple.Virtualization.VirtualMachine process spawns but never reaches a usable state. Instead, it enters a CPU spin loop consuming ~316% CPU (4 vCPU threads) and 1.9GB RAM indefinitely.

Environment

• Claude Code version: 2.1.44
• macOS: 26.3 (Build 25D125)
• Hardware: Apple M5, 32GB RAM
• Virtualization framework: Version 1.0 (259.4.2)

Observed Behavior

1. Run claude cowork
2. The com.apple.Virtualization.VirtualMachine XPC service spawns with 4 vCPU threads, 10 disk I/O threads, 2 virtual clock threads
3. vCPU threads enter a tight Hv::Vcpu::run() → hv_trap loop (hypervisor trap handling + GIC interrupt state sync)
4. Process consumes ~316% CPU continuously and never completes startup
5. No crash reports generated — the VM doesn't crash, it just spin-loops

Process Sample (key threads)

The 4 vCPU threads (com.apple.virtualization.thread.cpu-0 through cpu-3) show:

• ~90% of samples in Hv::Vcpu::run_once() → hv_trap (hypervisor exit handling)
• Remaining samples in GIC interrupt state synchronization (sync_from_gic_state, compute_list_registers)
• Lock contention visible on os_unfair_lock in GIC list register computation
• No threads appear idle or in a healthy wait state

All disk I/O threads and the defrag thread are waiting on condition variables (idle), suggesting the VM guest OS never gets far enough to perform disk I/O.

System State

• System load average during reproduction: 31+ (system under heavy CPU pressure from the VM)
• No related crash reports in ~/Library/Logs/DiagnosticReports/

Expected Behavior

claude cowork should either start successfully or fail gracefully with an error message instead of consuming all available CPU cores indefinitely.

Workaround

Kill the runaway process:

killall "com.apple.Virtualization.VirtualMachine"