The edit tool

Here's a key insight: Claude Code's Edit tool uses exact string matching, not regex. The model sends the exact old text to find and the exact new text to replace it with. This works because the model has already read the file and knows the exact content. No regex escaping, no line number fragility, no ambiguity.

This is the deepest insight in agent design: the model IS the agent. We don't need complex edit logic because the model handles the complexity. It reads the file, understands the code, and sends us the exact strings. Our job is just to be a reliable executor. Simple tools, smart model.