Harnesses exist to give models tools to do work beyond generating text. People install Claude Code and Codex to have models work inside their repositories and r

Harnesses exist to give models tools to do work beyond generating text. People install Claude Code and Codex to have models work inside their repositories and run the code or tests themselves instead of the user having to copypaste code between their IDE and a chat interface. The fact that there's some security built into the harnesses is just a practical consideration, not its primary function.