five-layer-architecture

Five-Layer Architecture

A layered architecture model for agentic systems that separates concerns and enables scalable, maintainable, production-ready systems.

The Five Layers

┌─────────────────────────────────────┐
│  Layer 5: Governance                │  Safety, compliance, audit
├─────────────────────────────────────┤
│  Layer 4: Runtime                   │  Execution, monitoring, scaling
├─────────────────────────────────────┤
│  Layer 3: Interaction               │  Tools, APIs, communication
├─────────────────────────────────────┤
│  Layer 2: Context                   │  Memory, state, knowledge
├─────────────────────────────────────┤
│  Layer 1: Cognition                 │  Reasoning, planning, decisions
└─────────────────────────────────────┘

Layer 1: Cognition

Core intelligence - reasoning, planning, and decision-making.

• Task understanding and decomposition
• Planning and strategy formulation
• Reasoning patterns (ReAct, Chain-of-Thought)
• Meta-cognition and self-reflection
• Anti-pattern: Mixing business logic into prompts, no separation between reasoning and action

Layer 2: Context

Memory, state, and knowledge management.

• Short-term working memory (conversation history)
• Long-term memory (persistent knowledge, vector search)
• State management and checkpointing
• Context window optimization and compression
• Anti-pattern: Passing entire history to every agent (context bloat)

Layer 3: Interaction

Tools, APIs, and communication channels.

• Tool/function registry and execution
• External API integration with error handling
• Multi-agent communication protocols
• Rate limiting, retry logic, serialization
• Anti-pattern: Tight coupling, no retry/timeout, missing input validation

Layer 4: Runtime

Execution environment, monitoring, and scaling.

• Agent lifecycle management (start, stop, restart)
• Concurrent execution and orchestration
• Observability (logging, tracing, metrics)
• Resource quotas, health checks, circuit breakers
• Anti-pattern: No observability, no resource limits, synchronous bottlenecks

Layer 5: Governance

Safety, compliance, and audit.

• Safety guardrails and action constraints
• Human-in-the-loop approval gates
• Audit logging, traceability, compliance
• PII detection, access control, rollback
• Anti-pattern: No approval gates, missing audit trails, no rollback

Layer Interaction Patterns

Bottom-Up Flow: Cognition decides → Context provides info → Interaction executes → Runtime monitors → Governance validates

Top-Down Constraints: Governance sets policies → Runtime enforces limits → Interaction restricts tools → Context filters sensitive data → Cognition operates within constraints

Cross-Layer: Observability, security, error handling, and performance optimization span all layers.

Designing a New System

1. Start with Cognition: What reasoning/planning capability do you need?
2. Add Context: What information must agents remember?
3. Define Interaction: What tools/APIs do agents need?
4. Build Runtime: How will you execute, monitor, scale?
5. Implement Governance: What safety/compliance is required?

Quick Reference

Layer	Focus	Key Question	Example Component
1. Cognition	Intelligence	"What should I do?"	LLM reasoning
2. Context	Memory	"What do I know?"	Vector database
3. Interaction	Tools	"How do I act?"	API clients
4. Runtime	Execution	"Is it working?"	Monitoring
5. Governance	Safety	"Is it safe?"	Approval gates

When to Use

• "How should I architect my agentic system?"
• "Where does [component] belong in the architecture?"
• "My system is getting messy and hard to maintain"
• "How do I separate concerns in my agent system?"

References

• refs/layers-cognition-context.md - Layer 1 (Cognition) and Layer 2 (Context) with implementation patterns
• refs/layers-interaction-runtime.md - Layer 3 (Interaction) and Layer 4 (Runtime) with implementation patterns
• refs/layers-governance-integration.md - Layer 5 (Governance) and cross-layer integration example
• refs/implementation-guide-layers-1-3.md - Building Layers 1-3 (Cognition, Context, Interaction)
• refs/implementation-guide-layers-4-5.md - Building Layers 4-5 (Runtime, Governance) and complete system