[BUG] Misspelled slash command as first message in new conversation produces no response

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 starting a brand new conversation and the first message is a misspelled slash command (e.g., /simply instead of /simplify, or /comit instead of /commit), Claude Code appears to hang and produces no response. The conversation becomes unresponsive — no error message, no suggestion, just silence.

This only seems to occur when the misspelled slash command is the first message in a fresh conversation (no prior context).

What Should Happen?

Claude Code should gracefully handle unrecognized slash commands with a helpful error message, e.g.:

• "Unknown command /simply. Did you mean /simplify?"
• Or at minimum, treat the input as a regular message and respond normally.

The user should never be left with no feedback at all.

Error Messages/Logs

No error messages displayed — that's the problem. The conversation simply produces no output.

Steps to Reproduce

1. Open Claude Code in VS Code (Claude Code for VS Code extension)
2. Start a brand new conversation (no prior messages)
3. Type a misspelled slash command as the first message, e.g. /simply (instead of /simplify)
4. Press Enter/submit
5. Observe: no response is produced; the conversation appears to hang

Claude Model

Opus

Is this a regression?

I don't know

Claude Code Version

2.1.72 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

Tested using Claude Code for VS Code extension on Windows 11. The issue may also affect the CLI but has only been confirmed in the VS Code extension so far.