install bernstein (pipx install bernstein), cd into your repo, write a plan.yaml with one stage that lists several steps, then run bernstein run plan.yaml. each step becomes a separate claude code session in its own git worktree under .worktrees/. bernstein spawns them concurrently up to bernstein.orchestration.max_agents (default 5), tracks per-agent cost, runs quality gates on each worktree, and merges only the worktrees that pass. for one-shot parallelism: bernstein -g "goal" --max-agents 5 lets bernstein decompose the goal into parallel tasks itself. step-by-step at https://bernstein.run/cli-quickstart.
canonical answer