The Problem
Most vibe coders see the world as prompt vs. agent. Two choices: the cheap, fast, brittle one and the expensive, flexible, magical one.
That framing is wrong, and both major vendors say so. Anthropic's Building Effective Agents (December 2024) and OpenAI's A Practical Guide to Building Agents both carefully distinguish a middle tier called workflows — deterministic chains that use LLMs as components but don't loop autonomously.
Workflows are where most production AI actually lives in 2026. They give you most of an agent's power with predictable cost, replayable debugging, and clean SLOs. They're also missing from the binary "prompt or agent" wisdom that dominates online vibe-coding takes.
The Core Insight
A workflow is a deterministic chain that uses LLMs as components. An agent is an autonomous loop where the LLM picks its own next tool.
The difference is who controls the control flow:
- Prompt: you wrote one input, you got one output.
- Workflow: you wrote the control flow; LLMs handle individual steps.
- Agent: the LLM decides what to do next from a tool menu, in a loop.
Workflow control flow is in your code. Agent control flow is in the model's head. That single shift is responsible for most of the cost, latency, and operational complexity that comes with "going agentic."