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.

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…”