How Coding Agents Edit Files: Diffs, Snapshots, and Fast Apply

2026-09-21

Coding agents commonly fail at the file system boundary because strict diffs require line arithmetic, exact whitespace, and a current view of the file. This survey compares search-and-replace blocks, fallback matchers, snapshot hashes, AST codemods, and neural fast-apply models used across tools such as Aider, Claude Code, OpenCode, and Cursor.