fix(core): allow assetPrefix to be an empty string

packages/core/src/helpers/url.ts

@@ -62,7 +62,8 @@ export const formatPublicPath = (
   withSlash = true,
 ): string => {
   // 'auto' is a magic value in Rspack and we should not add trailing slash
-  if (publicPath === 'auto') {
+  // Empty string is a valid value representing a relative path and should be preserved (important for node targets)
+  if (publicPath === 'auto' || publicPath === '') {
     return publicPath;
   }
 

packages/core/src/plugins/output.ts

@@ -16,22 +16,42 @@ import type {
 
 function getPublicPath({
   isDev,
+  isServer,
   config,
   context,
 }: {
   isDev: boolean;
+  isServer: boolean;
   config: NormalizedEnvironmentConfig;
   context: RsbuildContext;
 }) {
   const { dev, output, server } = config;
 
+  // For server targets (node), use empty string or explicit assetPrefix to enable relative paths
+  // This is important for worker_threads and other node-specific imports
+  // See: https://github.com/web-infra-dev/rsbuild/issues/6539
+  if (isServer) {
+    if (!isDev && typeof output.assetPrefix === 'string') {
+      return output.assetPrefix;
+    }
+    // For node targets in dev mode, use empty string by default
+    return '';
+  }
+
   let publicPath = DEFAULT_ASSET_PREFIX;
 
   // If `mode` is `production` or `none`, use `output.assetPrefix`
   if (!isDev) {
     if (typeof output.assetPrefix === 'string') {
       publicPath = output.assetPrefix;
     }
+  } else if (
+    typeof output.assetPrefix === 'string' &&
+    output.assetPrefix !== DEFAULT_ASSET_PREFIX
+  ) {
+    // In dev mode, prefer environment-specific `output.assetPrefix` over `dev.assetPrefix`
+    // but only if it's explicitly set to a non-default value
+    publicPath = output.assetPrefix;
   } else if (typeof dev.assetPrefix === 'string') {
     publicPath = dev.assetPrefix;
   } else if (dev.assetPrefix) {
@@ -83,6 +103,7 @@ export const pluginOutput = (): RsbuildPlugin => ({
         const publicPath = getPublicPath({
           config,
           isDev,
+          isServer,
           context: api.context,
         });