OpenRouter breaks multi-model agent stacks into orchestration, model routing and provider routing

What changed

OpenRouter published a comparison on October 2 that separates commonly conflated multi-model agent behavior into three layers: workflow orchestration for planning, state, memory and delegation; model routing for choosing a model and handling fallbacks; and provider routing for choosing the backend that serves that model. The post stresses that OpenRouter's `models` fallback is error-driven and does not evaluate answer quality, while frameworks such as LangGraph or CrewAI remain useful for durable state, human review and agent delegation.