When you run npm run build inside a Docker build targeting a different architecture than your host (e.g., building linux/amd64 on an arm64 Mac), the bundled tailwindcss binary may silently fail or hang during postcss execution. It does not always error out—but it does stall the build.

Rather than relying on the postcss approach, try to install Tailwind CSS CLI inside your Docker build environment and run it explicitly with npx.