---
title: "The control layer is the product, not the model"
url: https://daily.dev/posts/the-control-layer-is-the-product-not-the-model-kadj7ijuj
source_url: https://belderbos.dev/blog/control-layer-is-the-product
type: article
source: "Planet Python"
published: 2026-05-30T10:43:57.786Z
updated: 2026-05-30T10:44:19.894Z
tags: ["general-programming", "python", "llm", "ai-agents", "pydantic"]
reading_time: 6
upvotes: 1
comments: 0
language: en
---

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# The control layer is the product, not the model

**[Planet Python](https://daily.dev/sources/planetpython)** · 6 min read · 1 upvotes · 0 comments

## Summary

Gary Bernhardt's observation that developers are too fixated on LLM models rather than the control layer above them is used as a springboard to outline four engineering patterns for production-grade AI agents: (1) deterministic state machines that constrain the model to bounded tasks, (2) placing the model behind a typed Protocol boundary to make it swappable and testable, (3) a generator-evaluator split with guardrails between model output and user output, and (4) structured generation using Pydantic to enforce typed outputs. The core argument is that the control layer — routing, validation, state management, audit trails — is where the real product engineering happens, not in model selection.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://belderbos.dev/blog/control-layer-is-the-product>

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---

Tags: [#general-programming](https://daily.dev/tags/general-programming), [#python](https://daily.dev/tags/python), [#llm](https://daily.dev/tags/llm), [#ai-agents](https://daily.dev/tags/ai-agents), [#pydantic](https://daily.dev/tags/pydantic)

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