fix cookie set in middleware on initial render

Author: sommeeeer

packages/open-next/src/core/requestHandler.ts

@@ -92,6 +92,8 @@ export async function openNextHandler(
         delete headers[rawKey];
       }
 
+      delete overwrittenResponseHeaders["x-middleware-set-cookie"];
+
       if (
         "isExternalRewrite" in routingResult &&
         routingResult.isExternalRewrite === true

packages/open-next/src/core/routing/middleware.ts

@@ -115,7 +115,6 @@ export async function handleMiddleware(
   // These are internal headers used by Next.js, we don't want to expose them to the client
   const filteredHeaders = [
     "x-middleware-override-headers",
-    "x-middleware-set-cookie",
     "x-middleware-next",
     "x-middleware-rewrite",
     // We need to drop `content-encoding` because it will be decoded