Architecture

How the ADK fits together: the pipeline, the three type layers, the Runner loop, the LLM ABC, and the multi-agent composition primitives.

The big-picture pipeline. Every Runner.arun(...) call traverses this shape.

• Overview — The five-stage pipeline and where each subsystem plugs in.
• Type layers — LLMInputContentItem (Layer 1), ChatCompletion* (Layer 2 wire), RunItem (Layer 3 developer-facing).
• Runner — The agent loop, max_turns, retries, streaming.
• LLM ABC — Framework-owned LLM, not OpenAI's Model. One conversion per direction inside each provider.
• Handoffs & Swarms — Routing and iterative collaboration.
• Graphs — State-machine orchestration with checkpointers and HITL.
• Governance — Tenant routing, allowlists, audit, cost ledger.