vercel/next.js · error

experimental.lightningCssFeatures is set but experimental.us

Error message

experimental.lightningCssFeatures is set but experimental.useLightningcss is not enabled. The lightningCssFeatures option has no effect without useLightningcss.

What it means

Config warning during load: experimental.lightningCssFeatures is set, but experimental.useLightningcss is not enabled (and the bundler is not Turbopack). The features object only customizes Lightning CSS processing; without Lightning CSS actually enabled the option is inert, so the warning explains it has no effect.

Source

Thrown at packages/next/src/server/config.ts:2164

    }

    if ((userConfig as any).target && (userConfig as any).target !== 'server') {
      throw new Error(
        `The "target" property is no longer supported in ${configFileName}.\n` +
          'See more info here https://nextjs.org/docs/messages/deprecated-target-config'
      )
    }

    if (reactProductionProfiling) {
      userConfig.reactProductionProfiling = reactProductionProfiling
    }

    if (
      userConfig.experimental?.lightningCssFeatures &&
      !userConfig.experimental?.useLightningcss &&
      bundler !== Bundler.Turbopack
    ) {
      curLog.warn(
        `experimental.lightningCssFeatures is set but experimental.useLightningcss is not enabled. ` +
          `The lightningCssFeatures option has no effect without useLightningcss.`
      )
    }

    if (
      phase !== PHASE_PRODUCTION_SERVER &&
      userConfig.experimental?.useLightningcss
    ) {
      const { loadBindings } =
        require('../build/swc') as typeof import('../build/swc')
      const isLightningSupported = (
        await loadBindings(userConfig.experimental?.useWasmBinary)
      )?.css?.lightning

      if (!isLightningSupported) {
        curLog.warn(
          `experimental.useLightningcss is set, but the setting is disabled because next-swc/wasm does not support it yet.`

View on GitHub (pinned to 258b1c1bc0)

Solutions

1. Enable `experimental.useLightningcss` to make lightningCssFeatures take effect, or remove lightningCssFeatures.

When it happens

Trigger: Thrown at packages/next/src/server/config.ts:2119 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of vercel/next.js@258b1c1bc0 (2026-08-19). Data as JSON: /api/errors/d81159574f35face. Report an issue: GitHub.