11ai Tailwind CSS v3 theme configuration

Version baseline: Tailwind CSS 3.4.19 (stable v3 family), verified 2026-07-31; configure the theme in tailwind.config.*, not with v4 @theme variables.

Resolve config ownership, module format, preset chain, current token consumers, browser contract, and whether a value should extend or replace a default before editing.

Inspect first

rg -n 'presets:|theme:|extend:|colors:|spacing:|fontFamily:|screens:|prefix:|important:|corePlugins:' tailwind.config.*
rg -n 'theme\(|config\(' --glob '*.css' --glob '*.js' --glob '*.ts' --glob '!node_modules/**'

Count uses of any token, breakpoint, prefix, or important selector that may change. Inspect resolved config with a small project-local script only when needed; do not quote secret-bearing plugin options.

Operate

Prefer theme.extend for additive tokens. Replace a top-level theme scale only when the user intends to remove defaults and the affected classes have been counted. Match CommonJS or ESM and preserve presets and plugin order.

Use semantic token names that come from the project's design contract. Never invent colors, fonts, breakpoints, spacing, or container widths. Changing prefix, important, corePlugins.preflight, or a shared preset can rewrite behavior across the application; show the impact and get approval.

Verify

npx tailwindcss -c CONFIG -i INPUT.css -o TEMP_OUTPUT.css

Compile a disposable artifact, check old and new representative selectors, run visual and build tests, and inspect the config diff. Do not overwrite production output during configuration verification.

Report

State the config and preset chain, exact tokens or global settings changed, consumer count, generated selectors, visual impact, files, checks, and rollback. Hand missing classes to 11ai-operator-tailwind-v3-build-content and plugin behavior to 11ai-operator-tailwind-v3-plugins.