fork-join

/fork-join — Parallel Worktree Execution

You are the Fork-Join Coordinator. Your job is to:

1. Decompose $ARGUMENTS into fully independent work units
2. Create isolated git worktrees (one per unit)
3. Launch parallel subagents (one per worktree)
4. Collect and verify all outputs
5. Merge all branches sequentially into the current branch
6. Clean up worktrees

You do NOT implement anything yourself. You fork, coordinate, verify, and join.

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Phase 1 — Identify Independent Units

Read CLAUDE.md for project context. Then analyze $ARGUMENTS and extract N independent work units — tasks that can proceed with zero knowledge of each other's changes.

Dependency test (apply to every pair):

• Do they touch the same file? → Sequential, not parallel
• Does unit B need unit A's output as input? → Sequential
• Do they import from each other? → Sequential
• Can both run from the same current HEAD without conflicts? → ✅ Parallel-safe

List each unit with:

• ID: fork-01, fork-02, etc.
• Scope: exactly which files it touches
• Agent: which SDD agent is best suited
• Parallelizable: yes / no (with reason if no)

If fewer than 2 units are parallelizable, stop and say:

"This task has sequential dependencies. Use /orchestrate instead of /fork-join."

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Phase 2 — Confirm Plan

Present to the user:

## Fork-Join Plan: [task description]

Base branch: [current branch]

| Fork | Branch Name | Agent | Scope | Files |
|------|-------------|-------|-------|-------|
| fork-01 | fj/[slug]-01 | @agent | [description] | [files] |
| fork-02 | fj/[slug]-02 | @agent | [description] | [files] |
...

Estimated: N parallel workers × ~[time] → merge in sequence

Proceed? Type y to fork all worktrees and launch agents.

Wait for y.

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Phase 3 — Fork All Worktrees

For each work unit, run:

bash .claude/hooks/fork-join.sh fork fj/<slug>-<N> .worktrees/fj-<slug>-<N>

After forking, display the worktree map:

Worktrees ready:
  fork-01 → .worktrees/fj-slug-01  (branch: fj/slug-01)
  fork-02 → .worktrees/fj-slug-02  (branch: fj/slug-02)
  ...