ADK Architecture Guide
Core Interfaces (references/interfaces/)
- BaseNode — node contract, output/streaming, state/routing, HITL, configuration
- Workflow — graph orchestration, dynamic nodes (tracking/dedup/resume), transitive dynamic nodes, interrupt propagation, design rules for node authors
- Runner — The public interface for executing workflows and agents. Documents entrance methods
runandrun_async. - Agent — Blueprint defining identity, instructions, and tools. Documents that
runis the preferred entrance method. - BaseAgent — Base class for all agents. Defines the contract for subclassing with
_run_implas the primary override point. - Event — Core data structure for state reconstruction and communication. Represents a conversation turn or action.
Key Principles (references/principles/)
- API Principles — stability, backward compatibility, and self-containment. Use when making design choices that affect the public API surface.
Runtime Knowledge (references/architecture/)
- Context — 1:1 node-context mapping, InvocationContext singleton, property reference
- NodeRunner — two communication channels, execution flow, output delegation. Internal runtime details.
- Runner Roles — Runner vs NodeRunner vs Workflow separation. Explains why they are separate to avoid deadlocks.
- Checkpoint and Resume — HITL lifecycle,
rerun_on_resume,run_id - Observability — span-on-Context design, NodeRunner integration, correlated logs, metrics
- LLM Context Orchestration — relationship between events and LLM context, task delegation translation, branch isolation. Use when modifying event processing, context preparation for LLMs, or debugging context pollution issues.