Quick note from re-reading Anthropic’s Building Effective Agents. The core split they draw:

• Workflows are LLM systems where the steps are orchestrated by code you write. Predictable, debuggable, cheaper.
• Agents are LLM systems where the model decides its own next step in a loop. More flexible, harder to reason about, more expensive.

The practical takeaway: don’t reach for an agent when a workflow will do. Most production use cases are workflows wearing an agent costume.