Subagent Prompting Guide

# Subagent Prompting Guide

Subagents differ from skills: they run in isolation, receive delegated work from an orchestrator, and return results. Their output is consumed by the orchestrator, not a human. This constraint shapes everything below.

The deletion test: imagine removing a line from your subagent prompt. If behavior doesn't change, the line isn't earning its place.

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## Core — Apply to Every Subagent

### 1. Outcome-First with Phase Gates

Define what good looks like at each phase boundary. Trust the model to navigate within.

A subagent prompt should answer three questions:
- What does "done" look like? (outcome)
- What must be true before claiming done? (phase gates)
- What should never happen? (constraints)

Do not prescribe the path between gates unless sequence is the point. GPT-5.5 finds efficient solutions when given destination and constraints — process steps narrow its search space.