Fix build lags

dist/functions/server/web-pages/handle-web-pages.js

@@ -22,6 +22,15 @@ export default async function handleWebPages({ req, }) {
                 return new Response(existing_cache, res_opts);
             }
         }
+        // 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,
         });