Patch is generated with @[email protected]. Put `@unocss__vite.patch` in `./patches` and change package.json and run `pnpm i`

@unocss__vite.patch

diff --git a/dist/index.mjs b/dist/index.mjs
index 3c21e0e7246b6ecd916df9602e1627a0685ec4b9..fa894e15c78a8b82bf1c3029c600e592ec69bb0b 100644
--- a/dist/index.mjs
+++ b/dist/index.mjs
@@ -361,14 +361,14 @@ const VIRTUAL_ENTRY_ALIAS = [
 ];
 const LAYER_MARK_ALL = "__ALL__";
 const RESOLVED_ID_WITH_QUERY_RE = /[/\\]__uno(_.*?)?\.css(\?.*)?$/;
-const RESOLVED_ID_RE = /[/\\]__uno(?:_(.*?))?\.css$/;
+const RESOLVED_ID_RE = /[/\\]__uno(?:_(.*?))?\.css(?=(?:\?.*)?$)/;
 function resolveId(id) {
   if (id.match(RESOLVED_ID_WITH_QUERY_RE))
     return id;
   for (const alias of VIRTUAL_ENTRY_ALIAS) {
     const match = id.match(alias);
     if (match) {
-      return match[1] ? `/__uno_${match[1]}.css` : "/__uno.css";
+      return (match[1] ? `/__uno_${match[1]}.css` : "/__uno.css") + (match[2] ?? '');
     }
   }
 }
@@ -549,6 +549,8 @@ function GlobalModeBuildPlugin(ctx) {
     return lastResult;
   }
   let replaced = false;
+  let inlined = false
+  let inliningCSS = ''
   return [
     {
       name: "unocss:global:build:scan",
@@ -579,6 +581,9 @@ function GlobalModeBuildPlugin(ctx) {
       resolveId(id, importer) {
         const entry = resolveId(id);
         if (entry) {
+          if (entry.match(RESOLVED_ID_WITH_QUERY_RE)[2]) {
+            inlined = true
+          }
           const layer = resolveLayer(entry);
           if (layer) {
             vfsLayers.add(layer);
@@ -639,7 +644,7 @@ function GlobalModeBuildPlugin(ctx) {
           return null;
         }
         let { css } = await generateAll();
-        const fakeCssId = `${viteConfig.root}/${chunk.fileName}-unocss-hash.css`;
+        const fakeCssId = `${viteConfig.root}/${chunk.fileName}-unocss-hash.css${inlined?'?inline':''}`;
         css = await applyCssTransform(css, fakeCssId, options.dir, this);
         const transformHandler = "handler" in cssPost.transform ? cssPost.transform.handler : cssPost.transform;
         if (isLegacy) {
@@ -683,7 +688,7 @@ function GlobalModeBuildPlugin(ctx) {
         }
         const result = await generateAll();
         const importsLayer = result.getLayer(LAYER_IMPORTS) ?? "";
-        const fakeCssId = `${viteConfig.root}/${chunk.fileName}-unocss-hash.css`;
+        const fakeCssId = `${viteConfig.root}/${chunk.fileName}-unocss-hash.css${inlined?'?inline':''}`;
         const preflightLayers = ctx.uno.config.preflights?.map((i) => i.layer).concat(LAYER_PREFLIGHTS).filter(Boolean);
         await Promise.all(preflightLayers.map((i) => result.setLayer(i, async (layerContent) => {
           const preTransform = await applyTransformers(ctx, layerContent, fakeCssId, "pre");
@@ -704,7 +709,7 @@ function GlobalModeBuildPlugin(ctx) {
         }));
         const css = await applyCssTransform(cssWithLayers.join(""), fakeCssId, options.dir, this);
         const transformHandler = "handler" in cssPost.transform ? cssPost.transform.handler : cssPost.transform;
-        await transformHandler.call({}, css, fakeCssId);
+        inliningCSS = await transformHandler.call({}, css, fakeCssId);
       }
     },
     {
@@ -713,7 +718,7 @@ function GlobalModeBuildPlugin(ctx) {
       enforce: "post",
       // rewrite the css placeholders
       async generateBundle(options, bundle) {
-        const checkJs = ["umd", "amd", "iife"].includes(options.format);
+        const checkJs = ["umd", "amd", "iife"].includes(options.format) || inlined;
         const files = Object.keys(bundle).filter((i) => i.endsWith(".css") || checkJs && i.endsWith(".js"));
         if (!files.length)
           return;
@@ -748,7 +753,11 @@ function GlobalModeBuildPlugin(ctx) {
             const js = chunk.code.replace(HASH_PLACEHOLDER_RE, "");
             chunk.code = await replaceAsync(js, LAYER_PLACEHOLDER_RE, async (_, layer) => {
               replaced = true;
-              const css = getLayer(layer.trim(), js);
+              if (inlined) {
+                css = getLayer(layer.trim(), inliningCSS.code);
+              } else {
+                css = getLayer(layer.trim(), js);
+              }
               return css.replace(/\n/g, "").replace(/(?<!\\)(['"])/g, "\\$1");
             });
             Array.from(vfsLayers).forEach((layer) => {
@@ -819,6 +828,10 @@ function GlobalModeDevPlugin({ uno, tokens, tasks, flushTasks, affectedModules,
           const mod = server.moduleGraph.getModuleById(id);
           if (!mod)
             return null;
+          const match = id.match(RESOLVED_ID_WITH_QUERY_RE)
+          if (match && match[2] && match[2].includes('inline')) {
+            server.reloadModule(mod)
+          }
           return {
             acceptedPath: mod.url,
             path: mod.url,

package.json

{
  // ...
  "pnpm": {
    "patchedDependencies": {
      "@unocss/vite": "patches/@unocss__vite.patch"
    }
  }
}

plugin.ts

import type { Plugin } from 'vite';
import { MagicString } from 'vue/compiler-sfc';

export default function createPlugin(): Plugin {
  return {
    name: 'vite-unocss:rexport:post',
    enforce: "post",
    apply(config, env) {
      return env.command === "serve" && !config.build?.ssr;
    },
    transform(code, id) {
      const layer = resolveLayer(getPath(id));
      if (layer) {
        let head = `const __vite__id = "/__uno.css";
const __vite__css = `;
        const s = new MagicString(code);
        s.replace('export default ', head)
        s.append(`
export default __vite__css
import.meta.hot.accept()`)
        return {
          code: s.toString(),
          map: s.generateMap()
        };
      }
    },
  }
}

function getPath(id: string) {
  return id.replace(/\?.*$/, "");
}

const LAYER_MARK_ALL = "__ALL__";
const RESOLVED_ID_RE = /[/\\]__uno(?:_(.*?))?\.css(?=(?:\?.*)?$)/;
function resolveLayer(id: string) {
  const match = id.match(RESOLVED_ID_RE);
  if (match)
    return match[1] || LAYER_MARK_ALL;
}

vite.config.ts

// ...
import Rexport from './plugin'

export default defineConfig((config)=>({
  plugins: [
    vue(),
    Rexport(), // put it before Unocss()
    UnoCSS(),
    // ...
  ],
}))