Targeted Line-Range Mutation Protocol (replace_file_content Precision)

Overview

When tasked with fixing a bug in an existing file (e.g., adding an error check to src/services/billing.ts), naive agents re-emit the entire 500-line file from scratch using whole-file overwrite tools (write_to_file(Overwrite: true)).

Full-file rewriting causes severe operational problems:

1. Severe Token Waste: Emitting 500 lines to change 5 lines burns 3,500+ output tokens per edit turn.
2. Git Merge Conflicts: Re-writing the entire file touches timestamps and trailing whitespace on 495 unchanged lines, breaking git blame and creating merge conflicts.
3. Accidental Deletions: Long generation streams frequently truncate or hallucinate omissions in unchanged functions.

The Targeted Line-Range Mutation Protocol uses replace_file_content with precise [StartLine, EndLine] bounding, modifying strictly the target 5-to-10 line slice.

Full-File Overwrite vs. Line-Range Replacement