executing-parallel-phase

Executing Parallel Phase

Overview

Parallel phases enable TRUE concurrent execution via isolated git worktrees, not just logical independence.

Critical distinction: Worktrees are not an optimization to prevent file conflicts. They're the ARCHITECTURE that enables multiple subagents to work simultaneously.

When to Use

Use this skill when execute command encounters a phase marked "Parallel" in plan.md:

• ✅ Always use for N≥2 tasks
• ✅ Always use for N=1 (maintains architecture consistency)
• ✅ Even when files don't overlap
• ✅ Even under time pressure
• ✅ Even with disk space pressure

Never skip worktrees for parallel phases. No exceptions.

The Iron Law

PARALLEL PHASE = WORKTREES + SUBAGENTS

Violations of this law:

• ❌ Execute in main worktree ("files don't overlap")
• ❌ Skip worktrees for N=1 ("basically sequential")
• ❌ Use sequential strategy ("simpler")

All of these destroy the parallel execution architecture.

Multi-Repo Support

Receiving Multi-Repo Context

The orchestrator passes this context for multi-repo execution:

• WORKSPACE_MODE: "multi-repo" or "single-repo"
• WORKSPACE_ROOT: Absolute path to workspace
• Per-task TASK_REPO from plan

Multi-Repo Worktree Creation

In multi-repo mode, create worktrees INSIDE each task's repo:

Single-repo (current):

git worktree add .worktrees/${RUN_ID}-task-${PHASE}-${TASK} ...

Multi-repo (new):

# Worktree goes inside the task's repo
cd ${TASK_REPO}
git worktree add .worktrees/${RUN_ID}-task-${PHASE}-${TASK} ...
cd ${WORKSPACE_ROOT}

Per-Repo Setup Commands

In multi-repo mode, read setup commands from each task's repo:

# Single-repo: Read from project root CLAUDE.md
INSTALL_CMD=$(grep -A1 "**install**:" CLAUDE.md | tail -1)

# Multi-repo: Read from task's repo CLAUDE.md
INSTALL_CMD=$(grep -A1 "**install**:" ${TASK_REPO}/CLAUDE.md | tail -1)

Per-Repo Constitution

Pass the correct constitution path to subagents: