diff --git a/package.json b/package.json
index e92f23858..16506f1ad 100644
--- a/package.json
+++ b/package.json
@@ -36,11 +36,13 @@
   "dependencies": {
     "@swc/core": "1.3.39",
     "@vitejs/plugin-react": "^3.1.0",
+    "busboy": "^1.6.0",
     "vite": "^4.1.4"
   },
   "devDependencies": {
     "@swc/cli": "^0.1.62",
     "@types/babel__core": "^7.20.0",
+    "@types/busboy": "^1.5.0",
     "@types/node": "^18.15.0",
     "@types/react": "^18.0.28",
     "@types/react-dom": "^18.0.11",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 90a5ad37a..de623cd23 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -4,10 +4,12 @@ specifiers:
   '@swc/cli': ^0.1.62
   '@swc/core': 1.3.39
   '@types/babel__core': ^7.20.0
+  '@types/busboy': ^1.5.0
   '@types/node': ^18.15.0
   '@types/react': ^18.0.28
   '@types/react-dom': ^18.0.11
   '@vitejs/plugin-react': ^3.1.0
+  busboy: ^1.6.0
   nodemon: ^2.0.21
   react: 0.0.0-experimental-f828bad38-20230313
   react-dom: 0.0.0-experimental-f828bad38-20230313
@@ -18,11 +20,13 @@ specifiers:
 dependencies:
   '@swc/core': 1.3.39
   '@vitejs/plugin-react': 3.1.0_vite@4.1.4
+  busboy: 1.6.0
   vite: 4.1.4_@types+node@18.15.0
 
 devDependencies:
   '@swc/cli': 0.1.62_@swc+core@1.3.39
   '@types/babel__core': 7.20.0
+  '@types/busboy': 1.5.0
   '@types/node': 18.15.0
   '@types/react': 18.0.28
   '@types/react-dom': 18.0.11
@@ -690,6 +694,12 @@ packages:
       '@babel/types': 7.21.2
     dev: true
 
+  /@types/busboy/1.5.0:
+    resolution: {integrity: sha512-ncOOhwmyFDW76c/Tuvv9MA9VGYUCn8blzyWmzYELcNGDb0WXWLSmFi7hJq25YdRBYJrmMBB5jZZwUjlJe9HCjQ==}
+    dependencies:
+      '@types/node': 18.15.0
+    dev: true
+
   /@types/cacheable-request/6.0.3:
     resolution: {integrity: sha512-IQ3EbTzGxIigb1I3qPZc1rWJnH0BmSKv5QYTalEwweFvyBDLSAe24zP0le/hyi7ecGfZVlIVAg4BZqb8WBwKqw==}
     dependencies:
@@ -844,6 +854,13 @@ packages:
       update-browserslist-db: 1.0.10_browserslist@4.21.5
     dev: false
 
+  /busboy/1.6.0:
+    resolution: {integrity: sha512-8SFQbg/0hQ9xy3UNTB0YEnsNBbWfhf7RtnzpL7TkBiTBRfrQ9Fxcnz7VJsleJpyp6rVLvXiuORqjlHi5q+PYuA==}
+    engines: {node: '>=10.16.0'}
+    dependencies:
+      streamsearch: 1.1.0
+    dev: false
+
   /cacheable-lookup/5.0.4:
     resolution: {integrity: sha512-2/kNscPhpcxrOigMZzbiWF7dz8ilhb/nIHU3EyZiXWXpeq/au8qJ8VhdftMkty3n7Gj6HIGalQG8oiBNB3AJgA==}
     engines: {node: '>=10.6.0'}
@@ -1767,6 +1784,11 @@ packages:
     engines: {node: '>= 8'}
     dev: true
 
+  /streamsearch/1.1.0:
+    resolution: {integrity: sha512-Mcc5wHehp9aXz1ax6bZUyY5afg9u2rv5cqQI3mRrYkGC8rW2hM02jWuwjtL++LS5qinSyhj2QfLyNsuc+VsExg==}
+    engines: {node: '>=10.0.0'}
+    dev: false
+
   /string_decoder/1.3.0:
     resolution: {integrity: sha512-hkRX8U1WjJFd8LsDJ2yQ/wWWxaopEsABU1XfkM8A+j0+85JAGppt16cr1Whg6KIbb4okU6Mql6BOj+uup/wKeA==}
     dependencies:
diff --git a/src/client.ts b/src/client.ts
index 4bac492d2..83664fd7a 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -1,7 +1,7 @@
 import type { ReactNode } from "react";
 import RSDWClient from "react-server-dom-webpack/client";
 
-const { createFromFetch } = RSDWClient;
+const { createFromFetch, encodeReply } = RSDWClient;
 
 export function serve<Props>(rscId: string, render: (ele: ReactNode) => void) {
   return async (props: Props) => {
@@ -10,7 +10,8 @@ export function serve<Props>(rscId: string, render: (ele: ReactNode) => void) {
     searchParams.set("rsc_id", rscId);
     searchParams.set("props", serializedProps);
     const options = {
-      callServer(rsfId: string, args: unknown[]) {
+      async callServer(rsfId: string, args: unknown[]) {
+        const isMutating = !!mutationMode;
         const searchParams = new URLSearchParams();
         searchParams.set("rsf_id", rsfId);
         if (isMutating) {
@@ -19,7 +20,7 @@ export function serve<Props>(rscId: string, render: (ele: ReactNode) => void) {
         }
         const response = fetch(`/?${searchParams}`, {
           method: "POST",
-          body: JSON.stringify(args),
+          body: await encodeReply(args),
         });
         const data = createFromFetch(response, options);
         if (isMutating) {
@@ -38,13 +39,13 @@ export function serve<Props>(rscId: string, render: (ele: ReactNode) => void) {
   };
 }
 
-let isMutating = 0;
+let mutationMode = 0;
 
 export function mutate<Fn extends (...args: any[]) => any>(fn: Fn): Fn {
   return ((...args: unknown[]) => {
-    ++isMutating;
+    ++mutationMode;
     const result = fn(...args);
-    --isMutating;
+    --mutationMode;
     return result;
   }) as Fn;
 }
diff --git a/src/middleware/rscDev.ts b/src/middleware/rscDev.ts
index f72638c9f..f81fd3faa 100644
--- a/src/middleware/rscDev.ts
+++ b/src/middleware/rscDev.ts
@@ -5,10 +5,12 @@ import url from "node:url";
 import * as swc from "@swc/core";
 import RSDWRegister from "react-server-dom-webpack/node-register";
 import RSDWServer from "react-server-dom-webpack/server";
+import busboy from "busboy";
 
 import type { MiddlewareCreator } from "./common.ts";
 
-const { renderToPipeableStream } = RSDWServer;
+const { renderToPipeableStream, decodeReply, decodeReplyFromBusboy } =
+  RSDWServer;
 
 // TODO we would like a native solution without hacks
 // https://nodejs.org/api/esm.html#loaders
@@ -80,11 +82,21 @@ const rscDefault: MiddlewareCreator = (config) => {
     if (typeof rsfId === "string") {
       const [filePath, name] = rsfId.split("#");
       const fname = path.join(dir, filePath!);
-      let body = "";
-      for await (const chunk of req) {
-        body += chunk;
+      let args: unknown[] = [];
+      if (req.headers["content-type"]?.startsWith("multipart/form-data")) {
+        const bb = busboy({ headers: req.headers });
+        const reply = decodeReplyFromBusboy(bb);
+        req.pipe(bb);
+        args = await reply;
+      } else {
+        let body = "";
+        for await (const chunk of req) {
+          body += chunk;
+        }
+        if (body) {
+          args = await decodeReply(body);
+        }
       }
-      const args = body ? JSON.parse(body) : [];
       // TODO can we use node:vm?
       const mod = require(fname);
       const data = await (mod[name!] || mod)(...args);