Video · 22 min
Agent architectures
Key takeaway: Use a fixed workflow when you know the steps; use an agent only when the path must be decided at run time.
The spectrum
- Single call — one prompt, one answer. Cheapest and most predictable.
- Chain — fixed sequence of calls. Still predictable, better quality.
- Router — a model picks one of several fixed branches.
- Agent loop — the model chooses tools repeatedly until a stop condition.
Cost of freedom
Every extra degree of freedom multiplies latency, token spend and failure modes. Production systems are mostly chains and routers with one narrow agent where genuine open-endedness is required.
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