[BUG] PostToolUse Hook Exit Code 1 Blocks Claude Execution

Environment

• Platform: Anthropic API (via claude code max20)
• Claude CLI version: 1.0.64
• Operating System: macOS
• Terminal: Terminal App

Bug Description

PostToolUse hooks with exit code 1 block Claude's execution despite documentation stating they are "non-blocking" and "execution continues".

Steps to Reproduce

1. Create .claude/settings.json:

{
"hooks": {
"PostToolUse": [{
"matcher": "Read",
"hooks": [{
"type": "command",
"command": "./test-hook.sh"
}]
}]
}
}

1. Create test-hook.sh:

#!/bin/bash
echo "Warning: This is a non-blocking error" >&2
exit 1

1. Make it executable: chmod +x test-hook.sh
2. Ask Claude: "Read any file, then list the current directory"
3. Observe Claude is blocked after the Read operation

Expected Behavior

According to documentation: "Other exit codes: Non-blocking error. stderr is shown to the user and execution continues." https://docs.anthropic.com/en/docs/claude-code/hooks

Claude should:

1. Execute Read tool
2. Show hook's stderr to user
3. Continue with ls command

Actual Behavior

1. Read tool executes
2. User sees: PostToolUse:Read [./test-hook.sh] failed with non-blocking status code 1: Warning: This is a non-blocking error
3. Claude is blocked - cannot execute ls or any other command
4. User must type a response before Claude can continue

Additional Context

• Tested exit codes 0, 1, 2, 3 - only exit 0 and 2 allow Claude to continue
• This forces hooks to use exit 0 for all warnings/errors, losing the ability to show messages to users
• Documentation reference: https://docs.anthropic.com/en/docs/claude-code/hooks