Feedback: Performance Issues and Suggestions for Cursor's Apply Feature on Large C# Files

Hello Cursor Development Team,

I am a Cursor editor user, primarily using it to edit C# code. I’ve noticed an issue: when working with very large single C# code files (.cs) – for example, those exceeding 20,000 lines – the editor’s “Apply” (Apply Changes) feature often seems to malfunction. It might become extremely slow, laggy, or even fail completely.

To continue editing in such situations, I’ve found a workaround:

  1. First, I manually select the specific code snippet I want to modify.
  2. Then, I switch to Chat mode and describe my required changes to the AI, or ask it to modify the selected code directly.
  3. The AI generates the modified code, usually maintaining correct indentation.
  4. Finally, I copy the AI-generated code and manually paste it, replacing the original code snippet in the editor.

I’ve found this manual process works quite well and has several advantages:

  • It seems to consume minimal resources: Even in very large files, this operation completes quickly without causing the editor to lag.
  • It doesn’t rely on the full file context: This method only processes the selected snippet and doesn’t appear to need to load or analyze the context of the entire large file.

This makes me wonder: Since this “select → chat → copy/paste” method can efficiently handle localized changes in large files with low resource demands, why can’t the “Apply” feature reference or adopt a similar processing model?

If the “Apply” feature could also adopt a more “localized” processing logic behind the scenes – focusing only on processing the changed code snippet and its necessary immediate context, rather than attempting to analyze or manipulate the entire massive file – perhaps it could overcome the current limitations and support smooth AI editing and application of changes for files of any size.

I hope this feedback is helpful for improving the Cursor editor, making it more robust and efficient when handling large projects and files.

Thank you!

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