Gemini 2.5 pro 06-05 has issues with Edit & Reapply

Bug Reports
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Hi everyone,

I’ve experienced similar issues with the edit_file tool, especially when using Gemini 2.5 pro in the Cursor editor. To address these problems, I’ve summarized a set of specific guidelines that I found very helpful. These rules are tailored for Gemini 2.5 pro and can significantly improve the reliability and predictability of your file edits.

Special edit_file Guide for Gemini 2.5 pro in Cursor

Golden Rule: Treat every edit as a “surgical, precise replacement,” not a “fuzzy adjustment.”

Principle 1: Replace, Don’t Modify

  • Action Guideline: Target the smallest, complete logical block and provide a brand new block to completely replace it.
  • DO:
    • Replace entire lines or whole methods/logical blocks.
    • Example:
      // ... existing code ...
public int CalculateTotalPrice() { /* new, improved logic */ }
// ... existing code ...
  • DON’T:
    • Try to only change part of a line or just rename a method in place.
    • Example:
      // ... existing code ...
CalculateNewTotalPrice() // Only changing the method name—very risky
// ... existing code ...

Principle 2: Anchors Must Be Unique

  • Action Guideline: The context you use as anchors (e.g., // ... existing code ...) must be unique within the file, just like a fingerprint.
  • DO:
    • Include enough surrounding context to ensure uniqueness.
    • Example:
      // ... existing code ...
var result = await _service.GetSpecificData(id);
return View(result); // <--- This context combination is likely unique
// ... existing code ...
  • DON’T:
    • Use generic or potentially repeated code as an anchor (e.g., just a closing bracket).
    • Example:
      // ... existing code ...
} // <--- Highly likely to be a repeated anchor
// ... existing code ...

Principle 3: Code Must Be Complete

  • Action Guideline: The submitted code_edit must be a syntactically correct, logically self-contained unit. Don’t make the model guess.
  • DO:
    • Make sure the code you submit can be copy-pasted into the IDE without syntax errors.
  • DON’T:
    • Submit incomplete statements.
    • Example:
      // ... existing code ...
var user = new User { Name = // <--- Incomplete code
// ... existing code ...

Principle 4: Decompose Complex Tasks

  • Action Guideline: Large refactors = multiple consecutive, simple, and safe small replacements.
  • DO:
    1. First edit_file: Add a new helper method.
    2. Second edit_file: Replace the old logic block with code that calls the new method.
  • DON’T:
    • Define a new method and change all its usages in multiple places within a single edit_file operation.

Principle 5: Instructions Must Accurately Describe

  • Action Guideline: The instructions parameter should be a one-sentence, precise summary of the code_edit.
  • DO:
    • Example: instructions: "I will replace the user validation logic with a call to the new AuthService."
  • DON’T:
    • Use vague instructions like instructions: "Fix bug" or instructions: "Update code" (too broad and not helpful).

Summary:
These guidelines are specifically for Gemini 2.5 pro in the Cursor editor. By following them, I’ve seen a significant improvement in the reliability of edit_file operations. Breaking down complex changes, providing clear and unique context, and making sure each edit is a full, valid code block really helps avoid the common issues mentioned in this thread.

Hope this helps others who are struggling with similar problems using Gemini 2.5 pro in Cursor!

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