edit_file and search_replace tools fail to persist changes to .mdc files

Bug Reports
1

Describe the Bug

The edit_file and search_replace tools fail to persist changes to .mdc (Markdown Cursor) files in the .cursor/rules/ directory. The tools report success and the AI assistant can read the “changes”, but the modifications are not actually written to disk. Git shows no changes and the file content remains unchanged.

Steps to Reproduce

  1. Create or have an existing .mdc file (e.g., .cursor/rules/builder.mdc)
  2. Use the edit_file tool to modify the content with any changes
  3. The tool will report success with “The apply model made the following changes to the file”
  4. Run git status .cursor/rules/ - no changes are detected
  5. Check the file content with cat .cursor/rules/builder.mdc - original content remains unchanged
  6. Use read_file on the same file - it shows the “changes” that don’t exist on disk

This also occurs with the search_replace tool - it shows a diff but doesn’t persist changes.

Expected Behavior

  • Changes should be written to disk immediately
  • Git should detect the file as modified
  • File content on disk should reflect the edits
  • cat command should show the new content

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.0.0 (Universal)
VSCode Version: 1.96.2
Commit: 53b99ce608cba35127ae3a050c1738a959750860
Date: 2025-06-04T19:21:39.410Z
Electron: 34.5.1
Chromium: 132.0.6834.210
Node.js: 20.19.0
V8: 13.2.152.41-electron.0
OS: Darwin arm64 24.5.0

Additional Information

Workaround Found:

# 1. Create content in a regular .txt file
edit_file tmp-builder.txt [content]

# 2. Copy to .mdc file using terminal
cp tmp-builder.txt .cursor/rules/builder.mdc

# 3. Verify changes are now persisted
git status .cursor/rules/  # Now shows as modified

Does this stop you from using Cursor

No - Cursor works, but with this issue