[BUG] 100% CPU due to busy-polling bug #11473
Description
Preflight Checklist
- I have searched existing issues and this hasn't been reported yet
- This is a single bug report (please file separate reports for different bugs)
- I am using the latest version of Claude Code
What's Wrong?
Just starting Claude Code will make it consume 100% CPU.
What Should Happen?
When it's idle, it shouldn't use a significant number of CPU cycles.
Error Messages/Logs
Steps to Reproduce
- Start Claude
- Monitor CPU usage
Claude Model
Sonnet (default)
Is this a regression?
I don't know
Last Working Version
No response
Claude Code Version
v2.0.37
Platform
Anthropic API
Operating System
macOS
Terminal/Shell
Terminal.app (macOS)
Additional Information
I ran sudo dtruss -p <claude-pid> | tail -n 20 to see what it's doing. It appears to be a classic busy-polling bug in the event loop.
recvfrom(0x27, 0x7F9E48078020, 0x80000) = -1 Err#35
kevent64(0x6, 0x0, 0x0) = 1 0
recvfrom(0x27, 0x7F9E48078020, 0x80000) = -1 Err#35
kevent64(0x6, 0x0, 0x0) = 1 0
recvfrom(0x27, 0x7F9E48078020, 0x80000) = -1 Err#35
kevent64(0x6, 0x0, 0x0) = 1 0
recvfrom(0x27, 0x7F9E48078020, 0x80000) = -1 Err#35
kevent64(0x6, 0x0, 0x0) = 1 0
recvfrom(0x27, 0x7F9E48078020, 0x80000) = -1 Err#35
kevent64(0x6, 0x0, 0x0) = 1 0
recvfrom(0x27, 0x7F9E48078020, 0x80000) = -1 Err#35
kevent64(0x6, 0x0, 0x0) = 1 0
recvfrom(0x27, 0x7F9E48078020, 0x80000) = -1 Err#35
kevent64(0x6, 0x0, 0x0) = 1 0
recvfrom(0x27, 0x7F9E48078020, 0x80000) = -1 Err#35
kevent64(0x6, 0x0, 0x0) = 1 0
recvfrom(0x27, 0x7F9E48078020, 0x80000) = -1 Err#35
kevent64(0x6, 0x0, 0x0) = 1 0
recvfrom(0x27, 0x7F9E48078020, 0x80000) = -1 Err#35
kevent64(0x0, 0x0, 0x0) = 1 0
Or this
recvfrom(0x13, 0x7FC6700A8020, 0x80000) = -1 Err#35
recvfrom(0x2B, 0x7FC6700A8020, 0x80000) = -1 Err#35
recvfrom(0x2A, 0x7FC6700A8020, 0x80000) = -1 Err#35
recvfrom(0x28, 0x7FC6700A8020, 0x80000) = -1 Err#35
recvfrom(0x2D, 0x7FC6700A8020, 0x80000) = -1 Err#35
recvfrom(0x24, 0x7FC6700A8020, 0x80000) = -1 Err#35
recvfrom(0x1C, 0x7FC6700A8020, 0x80000) = -1 Err#35
recvfrom(0x1B, 0x7FC6700A8020, 0x80000) = -1 Err#35
recvfrom(0x22, 0x7FC6700A8020, 0x80000) = -1 Err#35
recvfrom(0x2C, 0x7FC6700A8020, 0x80000) = -1 Err#35
The process is continuously calling recvfrom() on multiple sockets (file descriptors 0x13, 0x2B, etc.), getting 'no data yet', and immediately trying again — in a tight loop with no sleep.