SubAgent framework behavior

Use explicit graph nodes when the multi-agent flow must move between ADK and LangGraph.

Need	Use
Portable multi-agent flow	Explicit root graph nodes
Recursive folder discovery	ADK folder SubAgents
Nested LangGraph agents	Root graph topology
Native child target	`Agent.advanced(...)` as a node or SubAgent

Portable composition

A portable graph names the SubAgent as a node. Harnest lowers the same topology to the selected framework.

Benefit	Result
Explicit routing	The graph shows when each child runs
Framework portability	No recursive discovery dependency
Testability	Unit tests can target the compiled graph

An Agent.advanced(...) wrapper can appear as a managed SubAgent or graph node.

Constraint	Rule
Root adapters	Embedded targets cannot use root input/output adapters
ADK target	Must be `BaseAgent`, not `App`
ADK name	Wrapper name must match the native agent name
Native capabilities	Framework-owned and migrated manually

A nested LangGraph Agent cannot consume a discovered sibling subagents/ folder. Express that topology in the root graph.

Review the complete managed and advanced portability boundary.