[BUG] @-mention file references don't resolve in browser-based VSCode (extension), but work fine in terminal Claude Code

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?

Environment:
Claude Code VSCode extension (browser-based VSCode — code-server)
OS: Linux (Stanford Sherlock HPC cluster environment, if relevant)
Comparison: same files, same workspace, terminal-based Claude Code CLI works correctly

Description:
When using @ to reference a file in the Claude Code VSCode extension chat, the extension cannot see/resolve my files — the @-mention autocomplete either shows nothing or fails to attach the referenced file's content. The same @-mention syntax works correctly when I run Claude Code directly in a terminal within the same environment/workspace.

What Should Happen?

@-mention should resolve files identically regardless of whether VSCode is running natively (desktop) or in a browser-hosted context.

Error Messages/Logs

Steps to Reproduce

1. Open browser-based VSCode - code-server with the Claude Code extension installed
2. Open a workspace with existing files (e.g., a Python/notebook project)
3. In the extension's chat panel, type @ followed by a filename
4. Observe: No files found
5. Compare: run claude in the integrated terminal in the same workspace, use @filename — works as expected

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.246

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_