spike — a throwaway worktree where only the audit trail stays on

/spike <slug> creates ../<project>-spike-<slug> on branch spike/<slug> and reduces that worktree's .claude/settings.json to the hooks spike.keep_modes lists. The main checkout never relaxes, and this session stays enforced; the person opens claude in the worktree.

Why this is a skill (Form 2) and not an agent

Form 2 because the trigger is the person deciding to explore (axis 2) and its effect — a worktree with enforcement off — must never start on the model's own decision. It is not an agent: none of the three reasons applies, the output is two lines and the work is three commands. Not disableAllHooks in a settings.local.json, which turns the audit trail off with everything else (0198, option 2).

Contract

• Class: ops — skill_classes.ops in @.claude/schemas/extensions.json: writes no file of this project with a tool; its effect is a sibling worktree, made by git worktree add and ArchHook.jar spike.
• Reads the project root (git rev-parse --show-toplevel) and the argument.
• Writes nothing inside the project. Outside it: the worktree ../<project>-spike-<slug> on branch spike/<slug>, whose .claude/settings.json ArchHook.jar spike reduces to the spike.keep_modes entries and marks skip-worktree.
• Does not merge, commit or push the spike, nor delete it — end prints the commands. Promoting spike code is a /new-feature run in the main checkout.
• Design: @.claude/decisions/0198-spike-worktree-with-hooks-off.md.

Procedure

1. Preconditions. Run from the main checkout: git rev-parse --git-dir equals git rev-parse --git-common-dir; otherwise stop (failure mode 1). The argument is a slug matching [a-z0-9][a-z0-9-]*; missing → ask once with AskUserQuestion, then stop.
2. end <slug> — print, do not run: git worktree remove ../<project>-spike-<slug> and git branch -D spike/<slug>, plus one line: the spike's spend is already in /audit-usage. Stop.
3. Create. git worktree add ../<project>-spike-<slug> -b spike/<slug>, where <project> is the basename of the root. Exists already → failure mode 2.
4. Relax. java -jar .claude/hooks/ArchHook.jar spike ../<project>-spike-<slug> and relay its stdout line verbatim. Non-zero → failure mode 3.
5. Report, then stop:

   ✅ Spike <slug> — ../<project>-spike-<slug> on spike/<slug>
   Hooks ....... audit only (format, check, tests, compose gate, guard off there)
   Next ........ open `claude` in that directory; this session stays enforced
   End ......... /spike end <slug>
   

Failure modes

1. Not the main checkout: ❌ /spike runs from the main checkout; this is a linked worktree. Open the project root and run it there.
2. Worktree or branch exists: ❌ ../<project>-spike-<slug> or spike/<slug> already exists. Pick another slug, or /spike end <slug> first.
3. spike mode refused: ❌ ArchHook spike refused: <its stderr first line>. The worktree exists with every hook on — remove it with git worktree remove ../<project>-spike-<slug>.