File Reference Autocomplete Broken in Claude Code Extension

Bug Description
Title: @ mentioning files not working in Claude Code
Description:
The @ symbol file mentioning feature in Claude Code is not functioning. When attempting to reference files using @filename syntax, the feature does not work as expected.
Newest Claude Code within VS Code Insiders.

Steps to reproduce:

Open Claude Code in a project directory
Try to use @ symbol to mention a file (e.g., @package.json)
Feature does not work

Environment Info

• Platform: macos
• Terminal: vscode
• Version: 1.0.21
• Feedback ID: bba8f20a-5e3d-4421-8f11-2db5bd929aa3

Errors

[{"error":"Error: Command failed: security find-generic-password -a $USER -w -s \"Claude Code\"\nsecurity: SecKeychainSearchCopyNext: The specified item could not be found in the keychain.\n\n    at genericNodeError (node:internal/errors:983:15)\n    at wrappedFn (node:internal/errors:537:14)\n    at checkExecSyncError (node:child_process:882:11)\n    at execSync (node:child_process:954:15)\n    at HZ (file:///Users/mibook/.npm-global/lib/node_modules/@anthropic-ai/claude-code/cli.js:659:3921)\n    at file:///Users/mibook/.npm-global/lib/node_modules/@anthropic-ai/claude-code/cli.js:582:11795\n    at Q (file:///Users/mibook/.npm-global/lib/node_modules/@anthropic-ai/claude-code/cli.js:526:17190)\n    at oJ (file:///Users/mibook/.npm-global/lib/node_modules/@anthropic-ai/claude-code/cli.js:582:10941)\n    at YS (file:///Users/mibook/.npm-global/lib/node_modules/@anthropic-ai/claude-code/cli.js:582:10022)\n    at R6 (file:///Users/mibook/.npm-global/lib/node_modules/@anthropic-ai/claude-code/cli.js:582:14134)","timestamp":"2025-06-12T15:21:07.931Z"}]