# Building Agentic Systems
All Building Agentic Systems notes →1. Agent Architecture
Covers: LLM, Tools, Memory, Planning, Execution Loop
2. Planner–Executor Pattern
How to wire a planner role and an executor role as two distinct LLM-call shapes inside a single agent process, and when that in-process split stops being the right call.
3. Router Pattern
Shows what the router pattern looks like wired into a single agent process -- one classification call that picks a specialized system prompt and tool set, with no sub-agent spawned and no service boundary crossed.
4. Workflow Agents
Covers agents that follow a predefined, deterministic sequence of steps rather than freely choosing their own next action, and when that constraint is the right engineering tradeoff.
5. Autonomous Agents
Covers agents that independently decide their own sequence of actions toward a goal, including the loop-control and stopping-condition problems that make them harder to bound than workflow agents.
6. Event-Driven Agents
Covers agents triggered by external events such as webhooks, message queues, or alerts rather than direct user prompts, and the design implications for statelessness and idempotency.
7. Human-in-the-Loop Systems
Covers patterns for pausing an agent to request human input or confirmation mid-task, and how to design the handoff so the agent resumes with full context.
8. Approval Workflows
Covers how to gate high-risk agent actions behind explicit human approval steps, including timeout handling and audit trail requirements.
9. Production-Ready Agent Design
Covers the checklist that separates a demo agent from a production one: retries, timeouts, cost controls, observability hooks, and graceful degradation under failure.