Bug? How to make Chat/Composer edit a cursor rule? MDC Editor gotchas

How To
1

I tried to make cursor edit a rule. I ask composer to edit a specific rule, it does so, I apply, but nothing shows up in the editor.

Nothing is written to the file, yet, chat/composer think it did update the file.

It seems to be because of the “MDC” editor… not sure how or why.

Steps:

  • Open .cursor/rules/my_rule.mdc (it opens with “MDC Editor” inside the IDE)
  • Ask Composer to make some changes to it, then apply
  • Nothing shows up in the editor
  • in the terminal cat .cursor/rules/my_rule.mdc shows empty file, or just with default mdc header
  • Reopen the same file with “Text Editor” within Cursor
  • Save it
  • Then the content shows up for real when I cat .cursor/rules/my_rule.mdc

WTF?

2

Forcing cursor to use “Text Editor” instead of “MDC Editor” for .mdc files fixed the issuse. Now I am able to see the rules updated by composer/chat and validate updates.

1 Like
3

And how do you configure that?

1 Like
4

@thomas-pedersen right-click on a rule file, “Open with…”, then, select at the bottom of the dialog “Configure default editor for…”

5

Hi there! I was having the exact same question and saw this post. I’m wondering now, what about the top part of the description, globs, and alwaysApply is it fine to leave as standard text on top of the document? Cursor will read them as well as they look for .mdc files?