TailwindCSS v4 had an update to the way you configure theme fonts variables. See this pull request https://github.com/tailwindlabs/tailwindcss/pull/14885. The font family variable has been renamed from --font-family-* variables to --font-* Old way ``` @theme { --font-family-display: "Inter", "sans-serif"; } ``` New way ``` @theme { --font-display: "Inter", "sans-serif"; } ```