Add a way to stop the stdioTransport in a graceful way

src/Server/Transport/Stdio/RunnerControl.php

@@ -0,0 +1,28 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Server\Transport\Stdio;
+
+/**
+ * Default implementation of RunnerControlInterface. This will allow
+ * anyone to change the state of the runner.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+class RunnerControl implements RunnerControlInterface
+{
+    public static RunnerState $state = RunnerState::RUNNING;
+
+    public function getState(): RunnerState
+    {
+        return self::$state;
+    }
+}

src/Server/Transport/Stdio/RunnerControlInterface.php

@@ -0,0 +1,22 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Server\Transport\Stdio;
+
+/**
+ * Used by the transport to control the runner state.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+interface RunnerControlInterface
+{
+    public function getState(): RunnerState;
+}

src/Server/Transport/Stdio/RunnerState.php

@@ -0,0 +1,24 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Server\Transport\Stdio;
+
+/**
+ * State for the transport.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+enum RunnerState
+{
+    case RUNNING;
+    case STOP_AND_END_SESSION;
+    case STOP;
+}

src/Server/Transport/StdioTransport.php

@@ -12,6 +12,9 @@
 namespace Mcp\Server\Transport;
 
 use Mcp\Schema\JsonRpc\Error;
+use Mcp\Server\Transport\Stdio\RunnerControl;
+use Mcp\Server\Transport\Stdio\RunnerControlInterface;
+use Mcp\Server\Transport\Stdio\RunnerState;
 use Psr\Log\LoggerInterface;
 
 /**
@@ -21,6 +24,8 @@
  */
 class StdioTransport extends BaseTransport
 {
+    private RunnerControlInterface $runnerControl;
+
     /**
      * @param resource $input
      * @param resource $output
@@ -29,7 +34,9 @@ public function __construct(
         private $input = \STDIN,
         private $output = \STDOUT,
         ?LoggerInterface $logger = null,
+        ?RunnerControlInterface $runnerControl = null,
     ) {
+        $this->runnerControl = $runnerControl ?? new RunnerControl();
         parent::__construct($logger);
     }
 
@@ -47,14 +54,17 @@ public function listen(): int
         $this->logger->info('StdioTransport is listening for messages on STDIN...');
         stream_set_blocking($this->input, false);
 
-        while (!feof($this->input)) {
+        while (!feof($this->input) && RunnerState::RUNNING === $this->runnerControl->getState()) {
             $this->processInput();
             $this->processFiber();
             $this->flushOutgoingMessages();
         }
 
         $this->logger->info('StdioTransport finished listening.');
-        $this->handleSessionEnd($this->sessionId);
+        if (\in_array($this->runnerControl->getState(), [RunnerState::RUNNING, RunnerState::STOP_AND_END_SESSION], true)) {
+            $this->logger->info('StdioTransport end session.');
+            $this->handleSessionEnd($this->sessionId);
+        }
 
         return 0;
     }