# How our agents build on-brand pages with design.md

Source: [Vercel](https://vercel.com/blog/how-our-agents-build-on-brand-pages-with-design-md)  
Feed7 permalink: https://feed7.dev/p/how-our-agents-build-on-brand-pages-with-design-md-2f54eb4a2e  
Published: 2026-08-31T00:00:00.000Z  
Trust: Official Source (official_source)

## Why Included

Pair written design guidance with fixed CSS primitives and frozen eval prompts to make agent-built interfaces more consistent.

## Source Summary

Vercel found that prose alone produced inconsistent agent-made pages, then paired design.md with fixed CSS primitives and repeatable evals to encode brand judgment.

## Practical Implication

For agent-built interfaces, encode reader intent and composition rules in context, move mechanical choices into reusable CSS, and rerun frozen prompts after every guidance change. Keep human review for hierarchy and deterministic checks for layout failures.

## Agent-Ready Context

Vercel built **design.md** as a public guidance file, paired it with a public stylesheet and an evaluation loop. It tests **seven fixed scenarios** across Claude Opus 4.8 and Codex with GPT-5.5.

For agent-built interfaces, encode reader intent and composition rules in context, move mechanical choices into reusable CSS, and rerun frozen prompts after every guidance change. Keep human review for hierarchy and deterministic checks for layout failures.

The reported comparison used one generation per condition with no rerolls. It shows that guidance changed one page's structure, but does not establish general reliability across models, prompts, or brands.

## Context Map

- Layer: agent
- Domains: coding
- Topics: skills, harness-engineering, design-engineering

## Uncertainty

- None recorded.

## Agent Instruction

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