3. Layered Architecture Map

The reference architecture has nine layers.

Layer	Name	Responsibility
8	Orchestration	Agent-as-tool, fan-out, delegation
7	Observability & Evaluation	Traces, spans, metrics, cost, failure diagnosis
6	Guardrails & Safety	Validation, sandboxing, permissions, limits, retries
5	Memory & State	Short-term context, working state, long-term retrieval
4	Control Loop	ReAct cycle, iteration caps, termination, error handling
3	Tools & Actions	Tool contracts, execution, observations, side effects
2	Structured Output	Output protocols, tool-call schemas, parsing
1	Context & Messages	Roles, task framing, token budget, context ordering
0	Model Engine	Stateless next-token prediction

Layer 8 (Orchestration) is out of scope for the current material. This manual covers Layers 0 through 7.

Each chapter follows the same pattern:

• Problem solved
• Service provided to the layer above
• Core components
• Design rules
• Failure modes