From ca71c1fad6555558cd120db8326ce9a69f8fc7bb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Samy=20Pess=C3=A9?= <samypesse@gmail.com>
Date: Fri, 12 Sep 2025 14:59:47 +0200
Subject: [PATCH] Fix MCP in production (#3647)

---
 .../[siteURL]/[siteData]/~gitbook/mcp/route.ts   | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/packages/gitbook/src/app/sites/static/[mode]/[siteURL]/[siteData]/~gitbook/mcp/route.ts b/packages/gitbook/src/app/sites/static/[mode]/[siteURL]/[siteData]/~gitbook/mcp/route.ts
index 77e6a11a5..b327be776 100644
--- a/packages/gitbook/src/app/sites/static/[mode]/[siteURL]/[siteData]/~gitbook/mcp/route.ts
+++ b/packages/gitbook/src/app/sites/static/[mode]/[siteURL]/[siteData]/~gitbook/mcp/route.ts
@@ -6,7 +6,10 @@ import { createMcpHandler } from 'mcp-handler';
 import type { NextRequest } from 'next/server';
 import { z } from 'zod';
 
-async function handler(request: NextRequest, { params }: { params: Promise<RouteLayoutParams> }) {
+async function handler(
+    nextRequest: NextRequest,
+    { params }: { params: Promise<RouteLayoutParams> }
+) {
     const { context } = await getStaticSiteContext(await params);
     const { dataFetcher, linker, site } = context;
 
@@ -66,9 +69,7 @@ async function handler(request: NextRequest, { params }: { params: Promise<Route
                 }
             );
         },
-        {
-            // Optional server options
-        },
+        {},
         {
             basePath: context.linker.toPathInSite('~gitbook/'),
             streamableHttpEndpoint: '/mcp',
@@ -78,6 +79,13 @@ async function handler(request: NextRequest, { params }: { params: Promise<Route
         }
     );
 
+    // Next.js request.url is the original URL and not the rewritten one from the middleware
+    const requestURL = new URL(
+        context.linker.toAbsoluteURL(context.linker.toPathInSite('~gitbook/mcp'))
+    );
+    requestURL.search = nextRequest.nextUrl.search;
+
+    const request = new Request(requestURL, nextRequest);
     return mcpHandler(request);
 }