[BUG] UI freeze and uncontrollable scrolling when typing "/" character - Local DoS

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?

When typing the "/" character in the Claude Code CLI input, the interface enters an uncontrollable scrolling state that completely freezes the UI.

Issue manifestation:

1. Trigger: Typing "/" in the CLI input field
2. Effect: Uncontrollable continuous scrolling begins immediately
3. UI State: Interface becomes completely non-responsive
4. Recovery Failure: Ctrl+C does NOT work to interrupt
5. Only Solution: Must forcefully kill the terminal process
6. Data Loss: Entire session and unsaved work is lost

Security Impact Assessment - CVSS 3.1 Score: 5.5 (MEDIUM)

Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

| Metric | Value | Rationale |
|--------|-------|-----------|
| Attack Vector | Local | User must type "/" locally |
| Attack Complexity | Low | Simple single character input |
| Privileges Required | None | Any user can trigger |
| User Interaction | None | Automatic after "/" typed |
| Availability | High | Complete application DoS |

What Should Happen?

1. Typing "/" should display the slash commands autocomplete menu normally
2. The autocomplete should be dismissible via Escape key
3. Backspace should remove "/" and close the menu
4. UI should remain fully responsive at all times
5. User should maintain complete control of the interface
6. Ctrl+C should work as expected to interrupt any operation

Error Messages/Logs

No error messages displayed - the UI simply freezes with continuous uncontrollable scrolling.
Terminal becomes completely unresponsive to all input including Ctrl+C.
Only recovery method is to kill the terminal process externally.

Steps to Reproduce

1. Open Claude Code CLI in terminal (Windows Terminal, PowerShell, or WSL2 Bash)
2. Start a new session or continue an existing conversation
3. In the input prompt, type the "/" character
4. Observe: Uncontrollable scrolling begins immediately
5. Attempt recovery: Try pressing Ctrl+C - it does NOT stop the behavior
6. Only solution: Kill the terminal process externally (Task Manager, kill command, or close terminal window)
7. Result: All session data and unsaved work is lost

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

v2.0.76

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

Video Evidence: A screen recording demonstrating this bug has been captured. The video shows:

• Normal Claude Code operation
• Typing "/" character
• Immediate onset of uncontrollable scrolling
• Failed Ctrl+C attempts
• Necessity of killing terminal

Environment Details:

• Windows 11 Home (64-bit)
• WSL2 Ubuntu 24.04 LTS available
• Claude Max subscription (Anthropic API)
• RAM: 64 GB

Impact on Workflow:

• Developers lose all unsaved session context
• Disrupts active development workflows
• Requires restarting entire session
• Potential loss of complex multi-step conversations

Potential Root Cause Hypothesis:
The slash command autocomplete feature may be entering an infinite render loop or event handling deadlock when processing the "/" input, preventing normal keyboard interrupt handling (Ctrl+C).