error with custom ssr webpack build

[dagda1]

I have a custom webpack 5 build that runs react in ssr.

I have a sprinkles file that looks like this:

import { defineProperties, createSprinkles, createMapValueFn } from '@vanilla-extract/sprinkles';

const responsiveAtomicProperties = defineProperties({
  conditions: {
    mobile: {},
    tablet: { '@media': `screen and (min-width: ${rem(breakpoints.tablet)})` },
    desktop: { '@media': `screen and (min-width: ${rem(breakpoints.desktop)})` },
    wide: { '@media': `screen and (min-width: ${rem(breakpoints.wide)})` },
  },

// etc.

The webpack compiler throws an error:

Cannot read properties of undefined (reading 'conditions')

The stack looks like this:

TypeError: Cannot read properties of undefined (reading 'conditions')\n" +
' at sprinklesFn (/Users/paulcowan/projects/cuttingedge/apps/website/src/components/Footer/Footer.css.ts:7116:58)\n' +
' at atoms (/Users/paulcowan/projects/cuttingedge/apps/website/src/components/Footer/Footer.css.ts:11817:12)\n' +
' at /Users/paulcowan/projects/cuttingedge/apps/website/src/components/Footer/Footer.css.ts:12407:17\n' +
' at /Users/paulcowan/projects/cuttingedge/apps/website/src/components/Footer/Footer.css.ts:12502:3\n' +
' at /Users/paulcowan/projects/cuttingedge/apps/website/src/components/Footer/Footer.css.ts:12505:12\n' +
' at Script.runInContext (node:vm:139:12)\n' +
' at Script.runInNewContext (node:vm:144:17)\n' +
' at Object.module.exports [as default] (/Users/paulcowan/projects/cuttingedge/node_modules/.pnpm/[email protected]/node_modules/eval/eval.js:74:12)\n' +
' at Object.processVanillaFile (/Users/paulcowan/projects/cuttingedge/node_modules/.pnpm/@Vanilla-Extract[email protected]/node_modules/@vanilla-extract/integration/dist/vanilla-extract-integration.cjs.prod.js:85:50)\n' +
' at /Users/paulcowan/projects/cuttingedge/node_modules/.pnpm/@Vanilla-Extract[email protected][email protected]/node_modules/@vanilla-extract/webpack-plugin/loader/dist/vanilla-extract-webpack-plugin-loader.cjs.prod.js:58:38'

The error is coming from the @vanilla-extract/webpack-plugin which basically evals the code:

  childCompiler
    .getCompiledSource(this)
    .then(async ({ source }) => {
      const result = await processVanillaFile({

Is there anything obvious that jumps out from this error or is there an easier way to debug this? I'm curious to know if it is something obvious like no window object when running ssr.