SKILL: Parallel Subagents

Purpose: Concurrent agent execution for independent tasks, 50-70% speedup Target: Orchestrators executing multiple independent SCs/tasks

Quick Start

When to Use This Skill

• Multiple independent SCs (no shared files, no dependencies)
• Independent code changes (different files/directories)
• Parallel verification (testing, type-check, linting)
• Multi-angle review (codereviewer, security-analyst in parallel)

Quick Reference

# Use per-SC dynamically selected agent type (from execute-plan Step 3)
Task:
  subagent_type: $SC_AGENT
  prompt: Implement SC-1: Create authentication service

Task:
  subagent_type: $SC_AGENT
  prompt: Implement SC-2: Create user service

Task:
  subagent_type: $SC_AGENT
  prompt: Implement SC-3: Create database migrations

Note: $SC_AGENT is selected per-SC (not per-plan) in execute-plan Step 3 based on each SC's file paths and keywords. Different SCs may use different specialized agents (e.g., SC-1 → frontend-engineer, SC-2 → backend-engineer).

⚠️ What "Parallel" Means (CRITICAL)

Parallel = Multiple Task calls in SAME response:

# ✅ TRUE PARALLEL (single response, multiple Task calls)
Task: subagent_type: coder, prompt: "Execute SC-1..."
Task: subagent_type: coder, prompt: "Execute SC-2..."
Task: subagent_type: coder, prompt: "Execute SC-3..."

Sequential = One Task per response (loop dispatch):

# ❌ NOT PARALLEL (even if called "parallel")
for SC in $SC_LIST; do
    Task: subagent_type: coder, prompt: "Execute $SC..."
done

If platform cannot true-parallelize: Rename to "batched delegation" (do not claim parallelism)

Core Concepts

Parallel Execution Patterns

Pattern 1: Independent SCs

Task: subagent_type: explorer, prompt: Search for auth patterns
Task: subagent_type: explorer, prompt: Search for database patterns
Task: subagent_type: explorer, prompt: Search for API patterns

Pattern 2: Parallel Verification

Task: subagent_type: tester, prompt: Run tests and verify coverage
Task: subagent_type: validator, prompt: Run type check and lint
Task: subagent_type: code-reviewer, prompt: Review for async bugs

Pattern 3: Multi-Angle Review

Task: subagent_type: plan-reviewer, prompt: Review plan completeness
Task: subagent_type: code-reviewer, prompt: Review code quality
Task: subagent_type: security-analyst, prompt: Review security issues

Dependency Analysis

Before launching parallel agents, check for conflicts:

1. File Overlap: Do SCs mention same files?
2. Dependency Keywords: "after", "depends", "requires", "follows"
3. ParallelGroup Annotation: Group independent SCs in plan

Coordination

Result Integration:

• Wait for all parallel agents to complete
• Check for file conflicts (rare if analysis correct)
• Update todos atomically (all parallel items together)

Performance: 50-70% faster for independent tasks

Anti-Patterns

Don't parallelize:

• Tasks with shared file modifications (causes merge conflicts)
• Tasks with dependencies (later task will fail)
• Sequential workflows (e.g., build then test)

Test Execution Concurrency

Critical: Multiple tester agents in parallel can cause worker explosion (6 agents × 16 workers = 96 processes, Load 85+)

Pattern: Test type-aware concurrency

• E2E/Integration: Sequential execution (one at a time)
• Unit/Lint/Type: Parallel allowed with --maxWorkers=50%

Detection (from execute-plan Step 3):

• Path: **/e2e/**, **/integration/**, **/*.e2e.*
• Keywords: "e2e", "integration", "playwright", "cypress"
• Fail-safe: Unknown → unit (parallel with worker limit)

Implementation: @.claude/agents/tester.md applies --maxWorkers=50% (Jest) or --workers=1 (Playwright E2E)

Full examples: See @.claude/skills/parallel-subagents/REFERENCE.md#test-execution-concurrency

Single Agent Delegation Pattern

When to Use

• Single SC execution (no parallelism needed)
• Sequential workflow steps
• Context protection for main orchestrator

Why Delegate Single Tasks

Main orchestrator context is limited (~200K tokens). By delegating:

• Subagent runs in isolated context (~80K tokens internally)
• Returns concise summary (~1K tokens) to orchestrator
• Orchestrator maintains clean context for coordination

Pattern

Task:
  subagent_type: [agent-type]
  prompt: |
    [Clear task description with all context needed]
    Skills to use: [skill1, skill2]
    Expected output: <MARKER_COMPLETE> or <MARKER_BLOCKED>

Examples

Single Coder Delegation:

Task:
  subagent_type: coder
  prompt: |
    Execute SC-1: Create authentication service
    Skills to use: tdd, ralph-loop, vibe-coding
    Expected output: <CODER_COMPLETE> or <CODER_BLOCKED>

Single Plan-Reviewer Delegation:

Task:
  subagent_type: plan-reviewer
  prompt: |
    Review plan at $PLAN_FILE for gaps and issues
    Review criteria: requirements coverage, success criteria clarity
    Expected output: <PLAN_COMPLETE> or <PLAN_BLOCKED>

Single Documenter Delegation:

Task:
  subagent_type: documenter
  prompt: |
    Invoke the three-tier-docs skill to sync documentation
    Project root: $PROJECT_ROOT
    Expected output: <DOCS_COMPLETE> or <DOCS_BLOCKED>

Verification

# Launch 3 independent tasks
Task: subagent_type: explorer, prompt: Find TypeScript files
Task: subagent_type: explorer, prompt: Find test files
Task: subagent_type: explorer, prompt: Find config files

# Verify all complete, no conflicts

Further Reading

Internal: @.claude/skills/parallel-subagents/REFERENCE.md - Detailed dependency analysis, command-specific patterns, coordination examples | @.claude/skills/using-git-worktrees/SKILL.md - Parallel development in isolated worktrees

External: None