Bug: edit_file and file operations fail silently in .cursor/rules directory

[batzel]

Bug: edit_file and file operations fail silently in .cursor/rules directory

Description

Two related issues have been discovered with file operations in the .cursor/rules directory:

1. The edit_file function fails silently when targeting files in .cursor/rules/
2. File copy operations to .cursor/rules/ create empty files

Steps to reproduce

1. Attempt to use edit_file to modify a file in .cursor/rules/:

edit_file("~/.cursor/rules/my-rule.mdc", "content")
# File is either not created or created empty

2. Try to copy files to .cursor/rules/:

cp existing-rule.mdc ~/.cursor/rules/
# Creates empty file

Expected behavior

• edit_file should successfully create/modify files in .cursor/rules/
• File copy operations should successfully copy content to .cursor/rules/
• If operations cannot be performed, clear error messages should be provided

Actual behavior

• Operations fail silently
• Empty files are created
• No error messages or warnings are shown
• Content appears in chat history but is not written to files

Impact

• Users cannot programmatically manage Cursor rules
• Manual workarounds are required (UI, external editors)
• Affects rule maintenance and automation
• Particularly problematic for global rules that apply across projects

Current workarounds

1. Use Cursor settings UI to create/edit rules
2. Write files to a different location then manually copy
3. Use symbolic links from writable locations
4. Edit files with external editors

Environment

• Cursor Version: 0.46.10
• OS: macOS Sonoma 14.3.1
• Architecture: Apple M1

Related issues

• GitHub Issue #2827 “edit_file function doesn’t work for files in .cursor/rules/”
• Forum thread: “Cursor agent cannot write to .cursor/rules files”

Reproduction Example

I encountered this while trying to create global rules for known Cursor issues. Here’s a minimal reproduction:

1. Create a directory for global rules:

mkdir -p ~/.cursor/rules/cursor-known-issues

2. Try to create a rule file:

edit_file("~/.cursor/rules/cursor-known-issues/test-rule.mdc", """---
description: Test rule
globs: ["**/*"]
alwaysApply: true
global: true
---

# Test Rule
- Test content
""")

3. Check the file:

cat ~/.cursor/rules/cursor-known-issues/test-rule.mdc
# File is empty

The same issue occurs with file copies and any other file operations targeting the .cursor/rules directory.