refactor(builder): add suppressUndefinedRejections

packages/builders/src/base-builder.ts

@@ -671,20 +671,26 @@ export const POST = workflowEntrypoint(workflowCode);`;
    * Creates a webhook handler bundle for resuming workflows via HTTP callbacks.
    *
    * @param bundle - If true, bundles dependencies (needed for Build Output API)
+   * @param suppressUndefinedRejections - If true, suppresses undefined rejections.
+   *                                      This is a workaround to avoid crashing in local
+   *                                      dev when context isn't set for waitUntil()
    */
   protected async createWebhookBundle({
     outfile,
     bundle = false,
+    suppressUndefinedRejections = false,
   }: {
     outfile: string;
     bundle?: boolean;
+    suppressUndefinedRejections?: boolean;
   }): Promise<void> {
     console.log('Creating webhook route');
     await mkdir(dirname(outfile), { recursive: true });
 
     // Create a static route that calls resumeWebhook
     // This route works for both Next.js and Vercel Build Output API
-    const routeContent = `import { resumeWebhook } from 'workflow/api';
+    const routeContent = `${suppressUndefinedRejections ? 'process.on("unhandledRejection", (reason) => { if (reason !== undefined) console.error("Unhandled rejection detected", reason); });\n' : ''}
+import { resumeWebhook } from 'workflow/api';
 
 async function handler(request) {
   const url = new URL(request.url);
@@ -725,7 +731,7 @@ export const OPTIONS = handler;`;
     const webhookBundleStart = Date.now();
     const result = await esbuild.build({
       banner: {
-        js: '// biome-ignore-all lint: generated file\n/* eslint-disable */\n',
+        js: `// biome-ignore-all lint: generated file\n/* eslint-disable */`,
       },
       stdin: {
         contents: routeContent,

packages/sveltekit/src/builder.ts

@@ -155,15 +155,12 @@ export const POST = async ({request}) => {
     await this.createWebhookBundle({
       outfile: webhookRouteFile,
       bundle: false, // SvelteKit will handle bundling
+      suppressUndefinedRejections: true,
     });
 
     // Post-process the generated file to wrap with SvelteKit request converter
     let webhookRouteContent = await readFile(webhookRouteFile, 'utf-8');
 
-    // NOTE: This is a workaround to avoid crashing in local dev when context isn't set for waitUntil()
-    webhookRouteContent = `process.on('unhandledRejection', (reason) => { if (reason !== undefined) console.error('Unhandled rejection detected', reason); });
-${webhookRouteContent}`;
-
     // Update handler signature to accept token as parameter
     webhookRouteContent = webhookRouteContent.replace(
       /async function handler\(request\) \{[\s\S]*?const token = decodeURIComponent\(pathParts\[pathParts\.length - 1\]\);/,