[BUG] File completion with @ symbol shows significant response delay (~500ms) after recent update

Bug Description

After updating to the latest version of Claude Code, the file completion feature using the @ symbol shows a noticeable response delay of approximately 500ms. Previously, file suggestions appeared instantly after typing one character following the @ symbol.

Expected Behavior

• File suggestions should appear immediately (within ~50ms) after typing a character following the @ symbol
• This was the behavior in previous versions

Actual Behavior

• File suggestions now take approximately 500ms to appear
• The delay is consistent and reproducible
• File completion still works correctly, but with noticeable latency

Environment Information

• OS: macOS 14.5 (Darwin 24.5.0)
• Claude Code Version: 1.0.24
• Project Size: ~50 files (small project)
• Terminal: Standard terminal
• Working Directory: Git repository

Steps to Reproduce

1. Open Claude Code in any project
2. Type @ followed by any character (e.g., @s)
3. Observe the delay before file suggestions appear
4. Compare with previous immediate response

Additional Context

• This issue occurs even in small projects (~50 files)
• The functionality works correctly, only the response time is affected
• No error messages are displayed
• The delay is consistent across different file patterns

Difference from Issue #1397

This issue is different from #1397 where file completion completely stops working. In this case:

• File completion works correctly but with added latency
• No broken functionality, only performance degradation
• Affects projects of all sizes, not just large monorepos

Impact

While not breaking functionality, this performance regression affects development workflow efficiency and user experience.