fix: Propogate the status code in middleware rewrites

.changeset/olive-buttons-allow.md

@@ -0,0 +1,5 @@
+---
+"@opennextjs/aws": patch
+---
+
+fix: Propagate the status code in middleware rewrites

packages/open-next/src/adapters/middleware.ts

@@ -20,6 +20,7 @@ import {
 import { constructNextUrl } from "../core/routing/util";
 import routingHandler, {
   INTERNAL_EVENT_REQUEST_ID,
+  INTERNAL_HEADER_REWRITE_STATUS_CODE,
   INTERNAL_HEADER_INITIAL_URL,
   INTERNAL_HEADER_RESOLVED_ROUTES,
 } from "../core/routingHandler";
@@ -86,6 +87,9 @@ const defaultHandler = async (
                   result.resolvedRoutes,
                 ),
                 [INTERNAL_EVENT_REQUEST_ID]: requestId,
+                [INTERNAL_HEADER_REWRITE_STATUS_CODE]: String(
+                  result.rewriteStatusCode,
+                ),
               },
             },
             isExternalRewrite: result.isExternalRewrite,

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

@@ -23,6 +23,7 @@ import {
 } from "./routing/util";
 import routingHandler, {
   INTERNAL_EVENT_REQUEST_ID,
+  INTERNAL_HEADER_REWRITE_STATUS_CODE,
   INTERNAL_HEADER_INITIAL_URL,
   INTERNAL_HEADER_RESOLVED_ROUTES,
   MIDDLEWARE_HEADER_PREFIX,
@@ -69,6 +70,9 @@ export async function openNextHandler(
         resolvedRoutes: initialHeaders[INTERNAL_HEADER_RESOLVED_ROUTES]
           ? JSON.parse(initialHeaders[INTERNAL_HEADER_RESOLVED_ROUTES])
           : ([] as ResolvedRoute[]),
+        rewriteStatusCode: Number.parseInt(
+          initialHeaders[INTERNAL_HEADER_REWRITE_STATUS_CODE],
+        ),
       };
 
       let routingResult: InternalResult | RoutingResult = {

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

@@ -28,6 +28,7 @@ const middleMatch = getMiddlewareMatch(
 type MiddlewareEvent = InternalEvent & {
   responseHeaders?: Record<string, string | string[]>;
   isExternalRewrite?: boolean;
+  rewriteStatusCode?: number;
 };
 
 type Middleware = (request: Request) => Response | Promise<Response>;
@@ -189,5 +190,6 @@ export async function handleMiddleware(
     cookies: internalEvent.cookies,
     remoteAddress: internalEvent.remoteAddress,
     isExternalRewrite,
+    rewriteStatusCode: statusCode,
   } satisfies MiddlewareEvent;
 }

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

@@ -413,6 +413,7 @@ export function createServerResponse(
     },
     responseStream,
     headers,
+    routingResult.rewriteStatusCode,
   );
 }
 

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

@@ -36,6 +36,7 @@ export const INTERNAL_HEADER_PREFIX = "x-opennext-";
 export const INTERNAL_HEADER_INITIAL_URL = `${INTERNAL_HEADER_PREFIX}initial-url`;
 export const INTERNAL_HEADER_LOCALE = `${INTERNAL_HEADER_PREFIX}locale`;
 export const INTERNAL_HEADER_RESOLVED_ROUTES = `${INTERNAL_HEADER_PREFIX}resolved-routes`;
+export const INTERNAL_HEADER_REWRITE_STATUS_CODE = `${INTERNAL_HEADER_PREFIX}rewrite-status-code`;
 export const INTERNAL_EVENT_REQUEST_ID = `${INTERNAL_HEADER_PREFIX}request-id`;
 
 // Geolocation headers starting from Nextjs 15
@@ -254,6 +255,7 @@ export default async function routingHandler(
       locale: NextConfig.i18n
         ? detectLocale(eventOrResult, NextConfig.i18n)
         : undefined,
+      rewriteStatusCode: middlewareEventOrResult.rewriteStatusCode,
     };
   } catch (e) {
     error("Error in routingHandler", e);

packages/open-next/src/http/openNextResponse.ts

@@ -71,8 +71,12 @@ export class OpenNextNodeResponse extends Transform implements ServerResponse {
     private onEnd: (headers: OutgoingHttpHeaders) => Promise<void>,
     private streamCreator?: StreamCreator,
     private initialHeaders?: OutgoingHttpHeaders,
+    statusCode?: number,
   ) {
     super();
+    if (statusCode !== undefined) {
+      this.statusCode = statusCode;
+    }
   }
 
   // Necessary for next 12

packages/open-next/src/types/open-next.ts

@@ -37,6 +37,7 @@ export type InternalResult = {
   headers: Record<string, string | string[]>;
   body: ReadableStream;
   isBase64Encoded: boolean;
+  rewriteStatusCode?: number;
 } & BaseEventOrResult<"core">;
 
 export interface StreamCreator {
@@ -151,6 +152,8 @@ export interface RoutingResult {
 
   // The resolved route after applying rewrites, if used with an external middleware will be defined in x-opennext-resolved-routes header as a json encoded array
   resolvedRoutes: ResolvedRoute[];
+  // The status code applied to a middleware rewrite
+  rewriteStatusCode?: number;
 }
 
 export interface MiddlewareResult