Workspace Isolation

A git worktree is a second working directory on its own branch that shares the repository's history. Work in one cannot disturb the files in another, so a plan can run without risking the user's checkout, and parallel agents cannot overwrite each other.

Core principle: detect existing isolation first, prefer the harness's own worktree mechanism, fall back to plain git, and never start work on a baseline you have not tested. A worktree created behind the harness's back is state it cannot see or clean up; a worktree started on a red baseline makes every later failure ambiguous.

The Prime Directive

NO IMPLEMENTATION WITHOUT AN ISOLATED WORKSPACE AND A KNOWN BASELINE

No exceptions. No workarounds. No shortcuts.

When to Use