[BUG] Claude hangs in "Caramelizing" state after completing task with background processes

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?

Title: Claude hangs in "Caramelizing" state after completing task with background processes

Description:
After starting background processes (backend/frontend servers) and responding that the task was complete, Claude Code remained in a waiting state ("Caramelizing") for 19+ minutes without returning control to the user. User had to
press Escape to interrupt.

Steps to reproduce:

1. Ask Claude to start backend and frontend servers using run_in_background: true
2. Claude starts both servers successfully and responds "The app is ready"
3. Claude does not return control - stays in "Caramelizing" state indefinitely
4. Background task notifications continue to arrive but Claude takes no action
5. User must press Escape to regain control

Expected behavior:
After completing the response, Claude should immediately return control to the user without requiring manual interruption.

Environment:

• Claude Code CLI
• Model: Claude Opus 4.5

What Should Happen?

o bug in the PWZ code - that was just me waiting for your next instruction after the servers started. The "Caramelizing" state means I had completed the task and was idle. The background task notifications were coming in (showing
the servers were active), but I had nothing more to do until you gave another command.

The servers are running and the app is working. What would you like me to do next?

❯ why should I have to press escape to take you out of this mode ?

⏺ You're right - you shouldn't have to. After I said "The app is ready and serving requests," my turn was complete and I should have returned control to you immediately.

The background task notifications kept coming in (showing server activity), but I had no action to take on them. Something in my processing kept me in a waiting state when I should have simply finished.

This isn't expected behavior. I apologize for the confusion - you shouldn't need to interrupt me after I've completed a task.

Error Messages/Logs

Steps to Reproduce

#!/usr/bin/env python3
"""
Reproduction script for Claude Code "Caramelizing" hang bug.

Bug: After starting background processes and completing a response,
Claude Code hangs in "Caramelizing" state instead of returning control
to the user. User must press Escape to interrupt.

To reproduce:

1. Open Claude Code in this directory
2. Ask: "Run the reproduction script in the background"
3. Claude will start the script and say it's running
4. Observe: Claude stays in "Caramelizing" state indefinitely
5. Press Escape to regain control

The script simulates a long-running server that periodically outputs,
similar to uvicorn/next.js dev servers.
"""

import time
import sys
from datetime import datetime

def simulate_server():
"""Simulate a dev server that outputs periodic status messages."""
print("=" * 60)
print("REPRODUCTION SCRIPT FOR CLAUDE CODE CARAMELIZING BUG")
print("=" * 60)
print(f"[{datetime.now().isoformat()}] Server starting...")
print(f"[{datetime.now().isoformat()}] Listening on http://localhost:9999")
print(f"[{datetime.now().isoformat()}] Server ready!")
print()

# Simulate periodic server activity (like request logs)
counter = 0
while True:
counter += 1
timestamp = datetime.now().isoformat()

# Output to stdout (like server request logs)
print(f"[{timestamp}] Heartbeat #{counter} - server is running")
sys.stdout.flush()

# Also output to stderr occasionally (like uvicorn does)
if counter % 3 == 0:
print(f"[{timestamp}] INFO: Background activity", file=sys.stderr)
sys.stderr.flush()

time.sleep(5) # Output every 5 seconds

if __name__ == "__main__":
try:
simulate_server()
except KeyboardInterrupt:
print("\nServer stopped.")
sys.exit(0)

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

2.1.5

Claude Code Version

2.1.17

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_