From 0958510b2be039edaf7727c20b0b537167db9e40 Mon Sep 17 00:00:00 2001
From: cyq <15000851237@163.com>
Date: Mon, 25 May 2026 08:35:42 +0800
Subject: [PATCH 1/2] fix: align streamable HTTP onclose type

---
 packages/middleware/node/src/streamableHttp.ts            | 4 ++--
 packages/middleware/node/test/streamableHttp.typecheck.ts | 5 +++++
 packages/server/src/server/streamableHttp.ts              | 2 +-
 3 files changed, 8 insertions(+), 3 deletions(-)
 create mode 100644 packages/middleware/node/test/streamableHttp.typecheck.ts

diff --git a/packages/middleware/node/src/streamableHttp.ts b/packages/middleware/node/src/streamableHttp.ts
index 68a0c224f0..a70588d4d7 100644
--- a/packages/middleware/node/src/streamableHttp.ts
+++ b/packages/middleware/node/src/streamableHttp.ts
@@ -100,11 +100,11 @@ export class NodeStreamableHTTPServerTransport implements Transport {
     /**
      * Sets callback for when the transport is closed.
      */
-    set onclose(handler: (() => void) | undefined) {
+    set onclose(handler: Transport['onclose']) {
         this._webStandardTransport.onclose = handler;
     }
 
-    get onclose(): (() => void) | undefined {
+    get onclose(): Transport['onclose'] {
         return this._webStandardTransport.onclose;
     }
 
diff --git a/packages/middleware/node/test/streamableHttp.typecheck.ts b/packages/middleware/node/test/streamableHttp.typecheck.ts
new file mode 100644
index 0000000000..701d636ad6
--- /dev/null
+++ b/packages/middleware/node/test/streamableHttp.typecheck.ts
@@ -0,0 +1,5 @@
+import type { Transport } from '@modelcontextprotocol/core';
+import { NodeStreamableHTTPServerTransport } from '../src/streamableHttp.js';
+
+const transport: Transport = new NodeStreamableHTTPServerTransport({});
+transport.onclose = undefined;
diff --git a/packages/server/src/server/streamableHttp.ts b/packages/server/src/server/streamableHttp.ts
index fd3563a077..2f563c3d94 100644
--- a/packages/server/src/server/streamableHttp.ts
+++ b/packages/server/src/server/streamableHttp.ts
@@ -242,7 +242,7 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
     private _supportedProtocolVersions: string[];
 
     sessionId?: string;
-    onclose?: () => void;
+    onclose?: Transport['onclose'];
     onerror?: (error: Error) => void;
     onmessage?: (message: JSONRPCMessage, extra?: MessageExtraInfo) => void;
 

From 6693b49ce8ea3f3a45e35480f4ca4bce48b5b6ad Mon Sep 17 00:00:00 2001
From: cyq <15000851237@163.com>
Date: Mon, 25 May 2026 08:38:14 +0800
Subject: [PATCH 2/2] chore: add changeset for streamable HTTP onclose type

---
 .changeset/streamable-http-onclose-types.md | 6 ++++++
 1 file changed, 6 insertions(+)
 create mode 100644 .changeset/streamable-http-onclose-types.md

diff --git a/.changeset/streamable-http-onclose-types.md b/.changeset/streamable-http-onclose-types.md
new file mode 100644
index 0000000000..f10c204ab7
--- /dev/null
+++ b/.changeset/streamable-http-onclose-types.md
@@ -0,0 +1,6 @@
+---
+'@modelcontextprotocol/node': patch
+'@modelcontextprotocol/server': patch
+---
+
+Align Streamable HTTP onclose types with the shared Transport contract.