make esbuild run serverless

package-lock.json

@@ -1872,6 +1872,18 @@
         "node": ">= 0.4"
       }
     },
+    "node_modules/esbuild-wasm": {
+      "version": "0.25.12",
+      "resolved": "https://registry.npmjs.org/esbuild-wasm/-/esbuild-wasm-0.25.12.tgz",
+      "integrity": "sha512-rZqkjL3Y6FwLpSHzLnaEy8Ps6veCNo1kZa9EOfJvmWtBq5dJH4iVjfmOO6Mlkv9B0tt9WFPFmb/VxlgJOnueNg==",
+      "license": "MIT",
+      "bin": {
+        "esbuild": "bin/esbuild"
+      },
+      "engines": {
+        "node": ">=18"
+      }
+    },
     "node_modules/escalade": {
       "version": "3.2.0",
       "resolved": "https://registry.npmjs.org/escalade/-/escalade-3.2.0.tgz",
@@ -3526,7 +3538,7 @@
       "license": "MIT",
       "dependencies": {
         "@mcp-ui/server": "^5.15.0",
-        "esbuild": "^0.25.0"
+        "esbuild-wasm": "^0.25.0"
       },
       "devDependencies": {
         "@types/node": "^20.10.0",
@@ -3539,6 +3551,9 @@
       "engines": {
         "node": ">=18.0.0"
       },
+      "optionalDependencies": {
+        "esbuild": "^0.25.0"
+      },
       "peerDependencies": {
         "react": ">=18.0.0",
         "react-dom": ">=18.0.0"
@@ -3584,6 +3599,7 @@
       "integrity": "sha512-bbPBYYrtZbkt6Os6FiTLCTFxvq4tt3JKall1vRwshA3fdVztsLAatFaZobhkBC8/BrPetoa0oksYoKXoG4ryJg==",
       "hasInstallScript": true,
       "license": "MIT",
+      "optional": true,
       "bin": {
         "esbuild": "bin/esbuild"
       },

packages/library/package.json

@@ -47,6 +47,9 @@
   "license": "MIT",
   "dependencies": {
     "@mcp-ui/server": "^5.15.0",
+    "esbuild-wasm": "^0.25.0"
+  },
+  "optionalDependencies": {
     "esbuild": "^0.25.0"
   },
   "peerDependencies": {

packages/library/server/bundle.ts

@@ -1,12 +1,38 @@
-import * as esbuild from 'esbuild';
-
 // Cache bundled JS per entry path (only used in production)
 const bundleCache = new Map<string, string>();
 
 // In development mode, skip cache to allow hot-reloading of component changes
 const isDev = process.env.NODE_ENV !== 'production';
 
-async function runBuild(entryPath: string): Promise<esbuild.BuildResult<{ write: false }>> {
+// Dynamic esbuild loader - tries native first, falls back to wasm for serverless
+let esbuildModule: typeof import('esbuild') | null = null;
+let wasmInitialized = false;
+
+async function getEsbuild(): Promise<typeof import('esbuild')> {
+    if (esbuildModule) return esbuildModule;
+
+    // Try native esbuild first (faster, works locally)
+    try {
+        esbuildModule = await import('esbuild');
+        // Test if native binary works
+        await esbuildModule.transform('', { loader: 'js' });
+        return esbuildModule;
+    } catch {
+        // Fall back to wasm (works on serverless without native binaries)
+        const wasm = await import('esbuild-wasm');
+        if (!wasmInitialized) {
+            await wasm.initialize({
+                wasmURL: `https://unpkg.com/esbuild-wasm@${wasm.version}/esbuild.wasm`,
+            });
+            wasmInitialized = true;
+        }
+        esbuildModule = wasm as typeof import('esbuild');
+        return esbuildModule;
+    }
+}
+
+async function runBuild(entryPath: string): Promise<import('esbuild').BuildResult<{ write: false }>> {
+    const esbuild = await getEsbuild();
     return esbuild.build({
         entryPoints: [entryPath],
         bundle: true,
@@ -27,7 +53,7 @@ export async function bundleComponent(entryPath: string): Promise<string> {
         return bundleCache.get(entryPath)!;
     }
 
-    let result: esbuild.BuildResult<{ write: false }>;
+    let result: import('esbuild').BuildResult<{ write: false }>;
 
     try {
         result = await runBuild(entryPath);
@@ -41,6 +67,7 @@ export async function bundleComponent(entryPath: string): Promise<string> {
         );
         if (isServiceError) {
             // Force stop the dead service, then retry - esbuild will start fresh
+            const esbuild = await getEsbuild();
             await esbuild.stop();
             result = await runBuild(entryPath);
         } else {