Ability to set custom protocol version (#117)

src/Server/Builder.php

@@ -20,6 +20,7 @@ use Mcp\Capability\Registry\Loader\LoaderInterface;
 use Mcp\Capability\Registry\ReferenceHandler;
 use Mcp\JsonRpc\MessageFactory;
 use Mcp\Schema\Annotations;
+use Mcp\Schema\Enum\ProtocolVersion;
 use Mcp\Schema\Implementation;
 use Mcp\Schema\ServerCapabilities;
 use Mcp\Schema\ToolAnnotations;
@@ -63,6 +64,8 @@ final class Builder
 
     private ?string $instructions = null;
 
+    private ?ProtocolVersion $protocolVersion = null;
+
     /**
      * @var array<int, RequestHandlerInterface<mixed>>
      */
@@ -288,6 +291,13 @@ final class Builder
         return $this;
     }
 
+    public function setProtocolVersion(?ProtocolVersion $protocolVersion): self
+    {
+        $this->protocolVersion = $protocolVersion;
+
+        return $this;
+    }
+
     /**
      * Manually registers a tool handler.
      *
@@ -404,7 +414,7 @@ final class Builder
         $messageFactory = MessageFactory::make();
 
         $capabilities = $registry->getCapabilities();
-        $configuration = new Configuration($this->serverInfo, $capabilities, $this->paginationLimit, $this->instructions);
+        $configuration = new Configuration($this->serverInfo, $capabilities, $this->paginationLimit, $this->instructions, $this->protocolVersion);
         $referenceHandler = new ReferenceHandler($container);
 
         $requestHandlers = array_merge($this->requestHandlers, [

src/Server/Configuration.php

@@ -11,6 +11,7 @@
 
 namespace Mcp\Server;
 
+use Mcp\Schema\Enum\ProtocolVersion;
 use Mcp\Schema\Implementation;
 use Mcp\Schema\ServerCapabilities;
 
@@ -34,6 +35,7 @@ class Configuration
         public readonly ServerCapabilities $capabilities,
         public readonly int $paginationLimit = 50,
         public readonly ?string $instructions = null,
+        public readonly ?ProtocolVersion $protocolVersion = null,
     ) {
     }
 }

src/Server/Handler/Request/InitializeHandler.php

@@ -52,6 +52,8 @@ final class InitializeHandler implements RequestHandlerInterface
                 $this->configuration->capabilities ?? new ServerCapabilities(),
                 $this->configuration->serverInfo ?? new Implementation(),
                 $this->configuration?->instructions,
+                null,
+                $this->configuration?->protocolVersion,
             ),
         );
     }