diff --git a/.esbuild/jison.js b/.esbuild/jison.js
index 40dda2cb5..7b68f9809 100644
--- a/.esbuild/jison.js
+++ b/.esbuild/jison.js
@@ -1,5 +1,5 @@
 // eslint-disable-next-line @typescript-eslint/no-var-requires
-const { transformJison } = require('./jisonTransformer');
+const { transformJison } = require('./jisonTransformer.cjs');
 const fileRegex = /\.(jison)$/;
 
 export default function jison() {
diff --git a/.vite/server.mjs b/.vite/server.mjs
new file mode 100644
index 000000000..38770ec8a
--- /dev/null
+++ b/.vite/server.mjs
@@ -0,0 +1,32 @@
+import express from 'express';
+import { createServer as createViteServer } from 'vite';
+
+async function createServer() {
+  const app = express();
+
+  // Create Vite server in middleware mode
+  const vite = await createViteServer({
+    configFile: './vite.config.cts',
+    server: { middlewareMode: true },
+    appType: 'custom', // don't include Vite's default HTML handling middlewares
+  });
+
+  app.use(express.static('demos'));
+  app.use(express.static('cypress/platform'));
+  // Use vite's connect instance as middleware
+  app.use(vite.middlewares);
+
+  app.use('*', async (req, res) => {
+    // Since `appType` is `'custom'`, should serve response here.
+    // Note: if `appType` is `'spa'` or `'mpa'`, Vite includes middlewares to handle
+    // HTML requests and 404s so user middlewares should be added
+    // before Vite's middlewares to take effect instead
+    res.end('Hello world!');
+  });
+
+  app.listen(9000, () => {
+    console.log(`Listening on http://localhost:9000`);
+  });
+}
+
+createServer();
diff --git a/demos/er.html b/demos/er.html
index 1e5d4062d..6d7f1033a 100644
--- a/demos/er.html
+++ b/demos/er.html
@@ -24,7 +24,7 @@ CUSTOMER }|..|{ DELIVERY-ADDRESS : uses
     </pre>
 
     <script type="module">
-      import mermaid from './mermaid.esm.mjs';
+      import mermaid from '../src/mermaid';
       mermaid.initialize({
         theme: 'forest',
         // themeCSS: '.node rect { fill: red; }',
diff --git a/vite.config.cts b/vite.config.cts
index 50f3faa83..a73864f19 100644
--- a/vite.config.cts
+++ b/vite.config.cts
@@ -1,32 +1,37 @@
-import { transformJison } from './.esbuild/jisonTransformer.cjs';
+import jison from './.esbuild/jison';
+import { resolve } from 'path';
 import { defineConfig } from 'vitest/config';
 
-const fileRegex = /\.jison$/;
-
-/** Transforms jison to js. */
-export function jisonPlugin() {
-  return {
-    name: 'transform-jison',
-
-    transform(src: string, id: string) {
-      if (fileRegex.test(id)) {
-        // eslint-disable-next-line no-console
-        console.log('Transforming', id);
-        return {
-          // @ts-ignore no typings for jison
-          code: transformJison(src),
-          map: null, // provide source map if available
-        };
-      }
-    },
-  };
-}
-
 export default defineConfig({
+  build: {
+    lib: {
+      entry: resolve(__dirname, 'src/mermaid.ts'),
+      name: 'mermaid',
+      // the proper extensions will be added
+      fileName: 'mermaid',
+    },
+    rollupOptions: {
+      // make sure to externalize deps that shouldn't be bundled
+      // into your library
+      external: ['require', 'fs', 'path'],
+      output: [
+        {
+          name: 'mermaid',
+          format: 'esm',
+          sourcemap: true,
+        },
+        {
+          name: 'mermaid',
+          format: 'umd',
+          sourcemap: true,
+        },
+      ],
+    },
+  },
   resolve: {
     extensions: ['.jison', '.js', '.ts', '.json'],
   },
-  plugins: [jisonPlugin()],
+  plugins: [jison()],
   test: {
     environment: 'jsdom',
     globals: true,
diff --git a/vite.config.js b/vite.config.js
deleted file mode 100644
index c947cae87..000000000
--- a/vite.config.js
+++ /dev/null
@@ -1,37 +0,0 @@
-import { resolve } from 'path';
-import { defineConfig } from 'vite';
-import jison from './.esbuild/jison';
-export default defineConfig({
-  plugins: [jison()],
-  resolve: {
-    extensions: ['.ts', '.js', '.json', '.jison'],
-  },
-  build: {
-    lib: {
-      entry: resolve(__dirname, 'src/mermaid.ts'),
-      name: 'mermaid',
-      // the proper extensions will be added
-      fileName: 'mermaid',
-    },
-    rollupOptions: {
-      // make sure to externalize deps that shouldn't be bundled
-      // into your library
-      external: ['require', 'fs', 'path'],
-      output: [
-        {
-          name: 'mermaid',
-          format: 'esm',
-          // Provide global variables to use in the UMD build
-          // for externalized deps
-        },
-        {
-          name: 'mermaid',
-          format: 'umd',
-
-          // Provide global variables to use in the UMD build
-          // for externalized deps
-        },
-      ],
-    },
-  },
-});