From 12012c869132e02c11e295ce411faceb8c48a3ca Mon Sep 17 00:00:00 2001
From: Adam Jamiu <adamjamiu@Adams-MacBook-Air.local>
Date: Sat, 24 Oct 2026 12:58:10 +0100
Subject: [PATCH 1/2] Fix client transport leak on reconnect

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 docs/client/connecting.md        |  2 ++
 src/Client.php                   |  2 ++
 tests/Unit/Client/ClientTest.php | 23 +++++++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/docs/client/connecting.md b/docs/client/connecting.md
index 14f6ea7af..c4e5a15ac 100644
--- a/docs/client/connecting.md
+++ b/docs/client/connecting.md
@@ -214,6 +214,8 @@ speaks revision `2026-07-28`, the connection is ready. If it doesn't, the client
 `initialize` handshake and offers `2025-11-25`, or the revision set with
 `setFallbackProtocolVersion()`. A server process that exits fails the connection instead.
 
+Calling `connect()` again on the same client closes its current transport before opening the new one.
+
 With `setFallbackProtocolVersion(null)`, `connect()` fails instead. See
 [How the client settles on an era](../protocol-versions.md#how-the-client-settles-on-an-era).
 
diff --git a/src/Client.php b/src/Client.php
index f70fdeee5..993511de7 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -92,6 +92,8 @@ public static function builder(): Builder
      */
     public function connect(TransportInterface $transport): void
     {
+        $this->disconnect();
+
         $this->transport = $transport;
         $this->protocol->connect($transport, $this->config);
 
diff --git a/tests/Unit/Client/ClientTest.php b/tests/Unit/Client/ClientTest.php
index 29d23ffeb..3c6da9a2a 100644
--- a/tests/Unit/Client/ClientTest.php
+++ b/tests/Unit/Client/ClientTest.php
@@ -21,6 +21,29 @@
 
 final class ClientTest extends TestCase
 {
+    public function testReconnectClosesPreviousTransport(): void
+    {
+        $client = Client::builder()->build();
+        $firstTransport = $this->createMock(TransportInterface::class);
+        $firstTransport->expects($this->once())->method('close');
+        $firstTransport->method('setState')->willReturnCallback(static function (ClientStateInterface $state): void {
+            $state->setInitialized(true);
+        });
+
+        $secondTransport = $this->createMock(TransportInterface::class);
+        $secondTransport->expects($this->once())->method('close');
+        $secondTransport->method('setState')->willReturnCallback(static function (ClientStateInterface $state): void {
+            $state->setInitialized(true);
+        });
+
+        $client->connect($firstTransport);
+        $client->connect($secondTransport);
+
+        $this->assertTrue($client->isConnected());
+
+        $client->disconnect();
+    }
+
     public function testSendRootsListChangedSendsNotificationWhenCapabilityDeclared(): void
     {
         $sent = [];

From 88ebb37d7a17537dbf570651b4b009cbe81933f0 Mon Sep 17 00:00:00 2001
From: Christopher Hertel <mail@christopher-hertel.de>
Date: Tue, 27 Oct 2026 22:09:58 +0100
Subject: [PATCH 2/2] Move reconnect note to Disconnecting and add changelog
 entry

---
 CHANGELOG.md              | 4 ++++
 docs/client/connecting.md | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index af2c10576..83668bccf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,10 @@ All notable changes to `mcp/sdk` will be documented in this file.
 * Fix tools with an array shape parameter whose keys are nullable or unions (e.g. `array{name: string, nickname: string|null}`) rejecting valid arguments with `-32602`: a `null` inside the shape no longer turns the parameter into `array|null`, and such keys get their own types instead of `object`, including lists and nested shapes (`string[]|null`, `array{x: int}|null`).
 * Fix `array<string|null>` and other generics with a union element getting `items` of type `object`. A `null` inside a generic no longer makes the parameter nullable, and neither does a DocBlock class whose name contains `null`.
 
+### Client
+
+* Fix `Client::connect()` leaving the previous transport open when called again: it closes the current transport first, so no stdio process or HTTP session is left behind.
+
 0.9.0
 -----
 
diff --git a/docs/client/connecting.md b/docs/client/connecting.md
index c4e5a15ac..206641184 100644
--- a/docs/client/connecting.md
+++ b/docs/client/connecting.md
@@ -214,8 +214,6 @@ speaks revision `2026-07-28`, the connection is ready. If it doesn't, the client
 `initialize` handshake and offers `2025-11-25`, or the revision set with
 `setFallbackProtocolVersion()`. A server process that exits fails the connection instead.
 
-Calling `connect()` again on the same client closes its current transport before opening the new one.
-
 With `setFallbackProtocolVersion(null)`, `connect()` fails instead. See
 [How the client settles on an era](../protocol-versions.md#how-the-client-settles-on-an-era).
 
@@ -250,6 +248,8 @@ try {
 }
 ```
 
+Calling `connect()` again on the same client closes its current transport before opening the new one.
+
 ## Server Information
 
 After successful connection, retrieve server metadata: