[BUG] Claude Code VSCode extension - Sessions get titled "Warmup" and have first prompt replaced with "Warmup"

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 VSCode extension - Sessions regularly get titled "Warmup" and have first message replaced with "Warmup".

This occured on Desktop VSCode on Windows using Claude Pro account as well as on code-server using Anthropic API.

To reproduce, try:

• Start new conversation, submit a single prompt like "This is a test to see if chat session titling works"
• Wait for a response

Try repeating the above a few times, keep checking the chat conversation dropdown to see what titles show up as, and there's a good chance you'll end up with one or more of these sessions end up getting titled "Warmup" and the initial prompt is replaced with "Warmup".

You can then try launching the CLI that comes bundled with the extension and there you'll likely NOT see those sessions named "Warmup" suggesting the problem is specific to the extension.

The title should instead be something like "Chat conversation test" or the like. And my initial prompt should remain unchanged.

What Should Happen?

<img width="1063" height="291" alt="Image" src="https://github.com/user-attachments/assets/22484d45-94cc-4050-b443-ef9fe12235fc" />

Error Messages/Logs

Steps to Reproduce

1. Start new conversation, submit a single prompt like "This is a test to see if chat session titling works"
2. Wait for a response
3. Try repeating the above a few times, keep checking the chat conversation dropdown to see what titles show up as, and there's a good chance you'll end up with one or more of these sessions end up getting titled "Warmup" and the initial prompt is replaced with "Warmup".

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.0.14

Claude Code Version

2.0.19

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_