From fceebdcf5a49837187b8436ccc323d1da4067287 Mon Sep 17 00:00:00 2001
From: Justin Spahr-Summers <justin@anthropic.com>
Date: Tue, 11 Feb 2025 17:58:58 +0000
Subject: [PATCH] Add `MCP-Protocol-Version` header

---
 src/client/auth.ts | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/client/auth.ts b/src/client/auth.ts
index 8b6eed7c..2c11ea8a 100644
--- a/src/client/auth.ts
+++ b/src/client/auth.ts
@@ -1,5 +1,6 @@
 import pkceChallenge from "pkce-challenge";
 import { z } from "zod";
+import { LATEST_PROTOCOL_VERSION } from "../types.js";
 
 export const OAuthMetadataSchema = z
   .object({
@@ -229,9 +230,15 @@ export async function auth(
  */
 export async function discoverOAuthMetadata(
   serverUrl: string | URL,
+  opts?: { protocolVersion?: string },
 ): Promise<OAuthMetadata | undefined> {
   const url = new URL("/.well-known/oauth-authorization-server", serverUrl);
-  const response = await fetch(url);
+  const response = await fetch(url, {
+    headers: {
+      "MCP-Protocol-Version": opts?.protocolVersion ?? LATEST_PROTOCOL_VERSION
+    }
+  });
+
   if (response.status === 404) {
     return undefined;
   }