[BUG]

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude Code CLI enters an infinite loop during normal chat interactions, consuming excessive CPU (70-80%) and becoming completely unresponsive to user input. The terminal displays rapidly flashing content that cannot be read or interrupted.

• CLI becomes completely unresponsive
• Input flashes too rapidly to read
• Unable to enter any commands or text
• CPU usage spikes to 70-80% per stuck process
• Only solution is to kill the process with kill -9 <PID>

What Should Happen?

Chat sessions should remain responsive and handle user input normally.

Error Messages/Logs

Debug logs reveal the `UserPromptSubmit` hook is executing in an infinite loop:

- **Loop iterations**: 4,046 executions in rapid succession (~100ms intervals)
- **Lock file errors**: 457 instances of "Lock file is already being held"
- **File write spam**: Repeatedly writing to `/Users/wbmccarty/.claude.json`

[DEBUG] Executing hooks for UserPromptSubmit
[DEBUG] Getting matching hook commands for UserPromptSubmit with query: undefined
[DEBUG] Found 0 hook matchers in settings
[DEBUG] Matched 0 unique hooks for query "no match query" (0 before deduplication)
[DEBUG] Found 0 hook commands to execute
[DEBUG] FileHistory: Making snapshot for message <uuid>
[DEBUG] FileHistory: Added snapshot for <uuid>, tracking 0 files
[ERROR] Failed to save config with lock: Error: Lock file is already being held
[DEBUG] Writing to temp file: /Users/wbmccarty/.claude.json.tmp.<PID>.<timestamp>
[DEBUG] Preserving file permissions: 100600
[DEBUG] Temp file written successfully, size: 83641 bytes
[DEBUG] Applied original permissions to temp file
[DEBUG] Renaming /Users/wbmccarty/.claude.json.tmp.<PID>.<timestamp> to /Users/wbmccarty/.claude.json
[DEBUG] File /Users/wbmccarty/.claude.json written atomically
[DEBUG] Hooks: getAsyncHookResponseAttachments called
[DEBUG] Hooks: checkForNewResponses called
[DEBUG] Hooks: Found 0 total hooks in registry
[DEBUG] Hooks: checkForNewResponses returning 0 responses
[DEBUG] Executing hooks for UserPromptSubmit
... [repeats indefinitely]


Full debug logs available if needed (4.4 MB log file for one stuck session).

Steps to Reproduce

1. Open multiple Claude Code CLI sessions
2. Engage in normal chat conversation (no special commands or tool usage)
3. After some time, one or more sessions will spontaneously enter an infinite loop

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.0.14

Claude Code Version

2.0.14 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Installation: npm-global

Root Cause Hypothesis

The UserPromptSubmit hook appears to be re-triggering itself, possibly due to:

1. Race condition in file locking mechanism
2. Hook system monitoring its own file changes
3. Event propagation bug causing hooks to recursively fire

Frequency

This has occurred multiple times over several days, affecting different chat sessions unpredictably.

Workaround

Kill the stuck process(es):

ps aux | grep claude  # Find stuck process PIDs with high CPU
kill -9 <PID>

Additional Notes

• No custom hooks are configured (debug logs show "Found 0 hook matchers in settings")
• Happens during normal chat, not related to any specific command or tool use
• Can affect multiple Claude Code sessions simultaneously