Superpowers Makes Execution Safe to Start

Once a design has been approved, obra/superpowers treats implementation as a boundary problem. This chapter explains how the methodology protects two things that conversation alone cannot protect: the project's state and the meaning of the agreed design. A worktree separates new changes from the current branch; an executable plan carries responsibilities, interfaces, constraints, and verification into the next context. The practical judgment is to know what these boundaries make safer—and what they still cannot prove.

Isolation is a state boundary

A worktree is an isolated working copy of a Git repository. The important idea is not the directory name. It is that the agent's changes have a defined place, a branch relationship, and a cleanup policy that are different from the user's current working state.

Superpowers begins by checking whether isolation already exists. A harness may have created a linked worktree before the skill starts, or the agent may be inside a submodule, which can look similar at the Git metadata level. The workflow distinguishes those cases before creating anything. If the agent is already in a linked worktree, creating another one adds confusion instead of safety. If it is in an ordinary checkout, the workflow asks whether the person wants an isolated workspace unless an explicit preference has already been stated.

That consent step is part of the state boundary. Creating a worktree changes where files, branches, and later commits live. It is usually reversible, but it is not an invisible implementation detail. The person directing the work may prefer to work in place, may have a harness with its own worktree controls, or may be managing the workspace externally. Superpowers therefore prefers native isolation tools when they exist and uses Git's worktree mechanism only as a fallback.

The fallback has its own safety condition: the project-local worktree directory must be ignored before a new worktree is created. Otherwise, the repository can interpret the worktree contents as ordinary untracked files, and a later commit may absorb an entire working copy. This is a small operational check with a large consequence. Isolation is useful only if the repository recognizes the boundary in the same way the agent does.

A newly isolated workspace is not automatically ready for implementation. Superpowers performs project setup when the project calls for it and runs a baseline test suite. The baseline answers a specific question: did the project already fail before this task began? Without that answer, a later failure may be caused by the agent's change, the starting tree, a missing dependency, or the environment. The worktree protects location; the baseline protects interpretation of later evidence.

Ownership continues through cleanup

The safety boundary must persist after coding. When a branch is finished, Superpowers detects whether the agent is in a normal repository, a named worktree branch, or a detached worktree managed by the host.