[BUG] v2.1.20 can't read multiple files

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?

After I updated vsCode claude extension to v2.1.20 today, it can't read multiple files in parallel.
I have a skill to read 10 context fills, but it stopped working with API error 400

What Should Happen?

It should read multiple ifles in pararellel successfully.

Error Messages/Logs

Steps to Reproduce

1. Create a skill to so it can read all context.md files in a project with multiple folders. allowed-tools: Glob, Read
2. Observe the skill found all the files with Glob and try to read them with Read.
3. Observe the issue happens at latest version.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

v2.1.19

Claude Code Version

not sure, it is vscode extension

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_