Use when multiple sessions work the same repo in parallel — several agent/dev sessions, a long-running review or build that must not be disturbed, or a quick look at another branch or PR. git worktree gives every branch its own directory (own node_modules, own build output) over one shared object store, and git itself enforces that a branch is checked out in at most one place. Covers add/list/remove/prune, per-worktree installs, the rm -rf stale-registration gotcha, and why worktrees and scratch checkouts belong on disk-backed paths, never tmpfs /tmp.
