References — Layout

Specifications

• CSS Flexible Box Layout Level 1 — including §4.5, the min-width: auto behaviour behind "my flex item won't shrink".
• CSS Grid Layout Level 2 — grid plus subgrid.
• CSS Box Sizing Level 3 — min-content, max-content, fit-content; the normative definitions behind experiment 2A.
• CSS Containment Level 3 — @container, container-type, container query units, and why containment is required.
• CSS Display Level 3 — formatting contexts.
• CSS Positioned Layout Level 3 — containing blocks and stacking.

Explanatory

• MDN — CSS Grid and Flexbox guides — Rachel Andrew's material; the most reliable on sizing.
• web.dev — Container queries
• Ahmad Shadeed — Container Queries and Min, Max, Fit-content
• CSS Tricks — Complete Guide to Grid / Flexbox — reference tables, not architecture advice.
• web.dev — Optimize CLS — the layout-stability half of this module.

Tooling

• Chrome DevTools — Inspect CSS grid and flexbox
• CDP — Performance domain

Deliberately excluded

Articles ranking layout methods by performance. Measured spread across six modes was 1.4×, with the usual "fast" recommendation slowest. Most such advice predates modern layout engines, and all of it is two orders of magnitude away from the decision that matters (content-visibility, fe-05).