Flat SubAgents - Fused

Use a flat file for a small SubAgent that needs only its definition. From a managed ADK agent’s root, create the discovered starter:

harnest add subagent researcher

The command refuses to overwrite an existing definition. Use --project <agent-root> when running it from elsewhere. LangGraph graphs define SubAgent topology explicitly in agent.py; see framework behavior.

subagents/
└── researcher.py

subagents/researcher.py exports an Agent named researcher.

Flat SubAgent properties

Property	Rule
File	`subagents/<name>.py`
Export	Must match the filename
Instructions	Defined by the agent declaration
Private tools	Not supported
Private MCP	Not supported
Private Agent Skills	Not supported
Use from parent	Reference by name or as a graph node

Move the SubAgent into a folder when it needs private instructions or capabilities.

Folder-owned SubAgents

Create a separate capability boundary for the child agent.