Fix build lags

src/functions/server/web-pages/handle-web-pages.tsx

@@ -34,6 +34,15 @@ export default async function handleWebPages({
             }
         }
 
+        // The dev server port opens before the one-time startup build
+        // finishes. First page render waits for it so we never serve HTML
+        // against half-built hydration/SSR modules.
+        if (is_dev && global.BUNEXT_INITIAL_BUILD_PROMISE) {
+            try {
+                await global.BUNEXT_INITIAL_BUILD_PROMISE;
+            } catch (error) {}
+        }
+
         const componentRes = await grabPageComponent({
             req,
         });