diff --git a/README.md b/README.md
index 8707e6c..60f2e63 100644
--- a/README.md
+++ b/README.md
@@ -1073,6 +1073,74 @@ $server = Server::make()
     ->build();
 ```
 
+### Middleware Support
+
+Both `HttpServerTransport` and `StreamableHttpServerTransport` support PSR-7 compatible middleware for intercepting and modifying HTTP requests and responses. Middleware allows you to extract common functionality like authentication, logging, CORS handling, and request validation into reusable components.
+
+Middleware must be a valid PHP callable that accepts a PSR-7 `ServerRequestInterface` as the first argument and a `callable` as the second argument.
+
+```php
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Message\ResponseInterface;
+use React\Promise\PromiseInterface;
+
+class AuthMiddleware
+{
+    public function __invoke(ServerRequestInterface $request, callable $next)
+    {
+        $apiKey = $request->getHeaderLine('Authorization');
+        if (empty($apiKey)) {
+            return new Response(401, [], 'Authorization required');
+        }
+        
+        $request = $request->withAttribute('user_id', $this->validateApiKey($apiKey));
+        $result = $next($request);
+        
+        return match (true) {
+            $result instanceof PromiseInterface => $result->then(fn($response) => $this->handle($response)),
+            $result instanceof ResponseInterface => $this->handle($result),
+            default => $result
+        };
+    }
+    
+    private function handle($response)
+    {
+        return $response instanceof ResponseInterface
+            ? $response->withHeader('X-Auth-Provider', 'mcp-server')
+            : $response;
+    }
+}
+
+$middlewares = [
+    new AuthMiddleware(),
+    new LoggingMiddleware(),
+    function(ServerRequestInterface $request, callable $next) {
+        $result = $next($request);
+        return match (true) {
+            $result instanceof PromiseInterface => $result->then(function($response) {
+                return $response instanceof ResponseInterface 
+                    ? $response->withHeader('Access-Control-Allow-Origin', '*')
+                    : $response;
+            }),
+            $result instanceof ResponseInterface => $result->withHeader('Access-Control-Allow-Origin', '*'),
+            default => $result
+        };
+    }
+];
+
+$transport = new StreamableHttpServerTransport(
+    host: '127.0.0.1',
+    port: 8080,
+    middlewares: $middlewares
+);
+```
+
+**Important Considerations:**
+
+- **Response Handling**: Middleware must handle both synchronous `ResponseInterface` and asynchronous `PromiseInterface` returns from `$next($request)`, since ReactPHP operates asynchronously
+- **Invokable Pattern**: The recommended pattern is to use invokable classes with a separate `handle()` method to process responses, making the async logic reusable
+- **Execution Order**: Middleware executes in the order provided, with the last middleware being closest to your MCP handlers
+
 ### SSL Context Configuration
 
 For HTTPS deployments of `StreamableHttpServerTransport`, configure SSL context options:
diff --git a/src/Transports/HttpServerTransport.php b/src/Transports/HttpServerTransport.php
index 1965704..c609dab 100644
--- a/src/Transports/HttpServerTransport.php
+++ b/src/Transports/HttpServerTransport.php
@@ -62,17 +62,25 @@ class HttpServerTransport implements ServerTransportInterface, LoggerAwareInterf
      * @param  int  $port  Port to listen on (e.g., 8080).
      * @param  string  $mcpPathPrefix  URL prefix for MCP endpoints (e.g., 'mcp').
      * @param  array|null  $sslContext  Optional SSL context options for React SocketServer (for HTTPS).
+     * @param array<callable(\Psr\Http\Message\ServerRequestInterface, callable): (\Psr\Http\Message\ResponseInterface|\React\Promise\PromiseInterface)> $middlewares Middlewares to be applied to the HTTP server.
      */
     public function __construct(
         private readonly string $host = '127.0.0.1',
         private readonly int $port = 8080,
         private readonly string $mcpPathPrefix = 'mcp',
         private readonly ?array $sslContext = null,
+        private array $middlewares = []
     ) {
         $this->logger = new NullLogger();
         $this->loop = Loop::get();
         $this->ssePath = '/' . trim($mcpPathPrefix, '/') . '/sse';
         $this->messagePath = '/' . trim($mcpPathPrefix, '/') . '/message';
+
+        foreach ($this->middlewares as $mw) {
+            if (!is_callable($mw)) {
+                throw new \InvalidArgumentException('All provided middlewares must be callable.');
+            }
+        }
     }
 
     public function setLogger(LoggerInterface $logger): void
@@ -114,7 +122,8 @@ public function listen(): void
                 $this->loop
             );
 
-            $this->http = new HttpServer($this->loop, $this->createRequestHandler());
+            $handlers = array_merge($this->middlewares, [$this->createRequestHandler()]);
+            $this->http = new HttpServer($this->loop, ...$handlers);
             $this->http->listen($this->socket);
 
             $this->socket->on('error', function (Throwable $error) {
@@ -261,7 +270,10 @@ protected function handleMessagePostRequest(ServerRequestInterface $request): Re
             return new Response(400, ['Content-Type' => 'application/json'], json_encode($error, $jsonEncodeFlags));
         }
 
-        $this->emit('message', [$message, $sessionId]);
+        $context = [
+            'request' => $request,
+        ];
+        $this->emit('message', [$message, $sessionId, $context]);
 
         return new Response(202, ['Content-Type' => 'text/plain'], 'Accepted');
     }
diff --git a/src/Transports/StreamableHttpServerTransport.php b/src/Transports/StreamableHttpServerTransport.php
index a836e71..9d9a349 100644
--- a/src/Transports/StreamableHttpServerTransport.php
+++ b/src/Transports/StreamableHttpServerTransport.php
@@ -67,6 +67,9 @@ class StreamableHttpServerTransport implements ServerTransportInterface, LoggerA
 
     /**
      * @param bool $enableJsonResponse If true, the server will return JSON responses instead of starting an SSE stream.
+     * @param bool $stateless If true, the server will not emit client_connected events.
+     * @param EventStoreInterface $eventStore If provided, the server will replay events to the client.
+     * @param array<callable(\Psr\Http\Message\ServerRequestInterface, callable): (\Psr\Http\Message\ResponseInterface|\React\Promise\PromiseInterface)> $middlewares Middlewares to be applied to the HTTP server.
      * This can be useful for simple request/response scenarios without streaming.
      */
     public function __construct(
@@ -76,12 +79,19 @@ public function __construct(
         private ?array $sslContext = null,
         private readonly bool $enableJsonResponse = true,
         private readonly bool $stateless = false,
-        ?EventStoreInterface $eventStore = null
+        ?EventStoreInterface $eventStore = null,
+        private array $middlewares = []
     ) {
         $this->logger = new NullLogger();
         $this->loop = Loop::get();
         $this->mcpPath = '/' . trim($mcpPath, '/');
         $this->eventStore = $eventStore;
+
+        foreach ($this->middlewares as $mw) {
+            if (!is_callable($mw)) {
+                throw new \InvalidArgumentException('All provided middlewares must be callable.');
+            }
+        }
     }
 
     protected function generateId(): string
@@ -119,7 +129,8 @@ public function listen(): void
                 $this->loop
             );
 
-            $this->http = new HttpServer($this->loop, $this->createRequestHandler());
+            $handlers = array_merge($this->middlewares, [$this->createRequestHandler()]);
+            $this->http = new HttpServer($this->loop, ...$handlers);
             $this->http->listen($this->socket);
 
             $this->socket->on('error', function (Throwable $error) {
diff --git a/tests/Fixtures/General/RequestAttributeChecker.php b/tests/Fixtures/General/RequestAttributeChecker.php
new file mode 100644
index 0000000..a79861a
--- /dev/null
+++ b/tests/Fixtures/General/RequestAttributeChecker.php
@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpMcp\Server\Tests\Fixtures\General;
+
+use PhpMcp\Schema\Content\TextContent;
+use PhpMcp\Server\Context;
+
+class RequestAttributeChecker
+{
+    public function checkAttribute(Context $context): TextContent
+    {
+        $attribute = $context->request->getAttribute('middleware-attr');
+        if ($attribute === 'middleware-value') {
+            return TextContent::make('middleware-value-found: ' . $attribute);
+        }
+
+        return TextContent::make('middleware-value-not-found: ' . $attribute);
+    }
+}
diff --git a/tests/Fixtures/Middlewares/ErrorMiddleware.php b/tests/Fixtures/Middlewares/ErrorMiddleware.php
new file mode 100644
index 0000000..f2be79e
--- /dev/null
+++ b/tests/Fixtures/Middlewares/ErrorMiddleware.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpMcp\Server\Tests\Fixtures\Middlewares;
+
+use Psr\Http\Message\ServerRequestInterface;
+
+class ErrorMiddleware
+{
+    public function __invoke(ServerRequestInterface $request, callable $next)
+    {
+        if (str_contains($request->getUri()->getPath(), '/error-middleware')) {
+            throw new \Exception('Middleware error');
+        }
+        return $next($request);
+    }
+}
diff --git a/tests/Fixtures/Middlewares/FirstMiddleware.php b/tests/Fixtures/Middlewares/FirstMiddleware.php
new file mode 100644
index 0000000..31fb153
--- /dev/null
+++ b/tests/Fixtures/Middlewares/FirstMiddleware.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpMcp\Server\Tests\Fixtures\Middlewares;
+
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Message\ResponseInterface;
+use React\Promise\PromiseInterface;
+
+class FirstMiddleware
+{
+    public function __invoke(ServerRequestInterface $request, callable $next)
+    {
+        $result = $next($request);
+
+        return match (true) {
+            $result instanceof PromiseInterface => $result->then(fn($response) => $this->handle($response)),
+            $result instanceof ResponseInterface => $this->handle($result),
+            default => $result
+        };
+    }
+
+    private function handle($response)
+    {
+        if ($response instanceof ResponseInterface) {
+            $existing = $response->getHeaderLine('X-Middleware-Order');
+            $new = $existing ? $existing . ',first' : 'first';
+            return $response->withHeader('X-Middleware-Order', $new);
+        }
+        return $response;
+    }
+}
diff --git a/tests/Fixtures/Middlewares/HeaderMiddleware.php b/tests/Fixtures/Middlewares/HeaderMiddleware.php
new file mode 100644
index 0000000..bc8a456
--- /dev/null
+++ b/tests/Fixtures/Middlewares/HeaderMiddleware.php
@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpMcp\Server\Tests\Fixtures\Middlewares;
+
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Message\ResponseInterface;
+use React\Promise\PromiseInterface;
+
+class HeaderMiddleware
+{
+    public function __invoke(ServerRequestInterface $request, callable $next)
+    {
+        $result = $next($request);
+
+        return match (true) {
+            $result instanceof PromiseInterface => $result->then(fn($response) => $this->handle($response)),
+            $result instanceof ResponseInterface => $this->handle($result),
+            default => $result
+        };
+    }
+
+    private function handle($response)
+    {
+        return $response instanceof ResponseInterface
+            ? $response->withHeader('X-Test-Middleware', 'header-added')
+            : $response;
+    }
+}
diff --git a/tests/Fixtures/Middlewares/RequestAttributeMiddleware.php b/tests/Fixtures/Middlewares/RequestAttributeMiddleware.php
new file mode 100644
index 0000000..2b07f7a
--- /dev/null
+++ b/tests/Fixtures/Middlewares/RequestAttributeMiddleware.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpMcp\Server\Tests\Fixtures\Middlewares;
+
+use Psr\Http\Message\ServerRequestInterface;
+
+class RequestAttributeMiddleware
+{
+    public function __invoke(ServerRequestInterface $request, callable $next)
+    {
+        $request = $request->withAttribute('middleware-attr', 'middleware-value');
+        return $next($request);
+    }
+}
diff --git a/tests/Fixtures/Middlewares/SecondMiddleware.php b/tests/Fixtures/Middlewares/SecondMiddleware.php
new file mode 100644
index 0000000..275746e
--- /dev/null
+++ b/tests/Fixtures/Middlewares/SecondMiddleware.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpMcp\Server\Tests\Fixtures\Middlewares;
+
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Message\ResponseInterface;
+use React\Promise\PromiseInterface;
+
+class SecondMiddleware
+{
+    public function __invoke(ServerRequestInterface $request, callable $next)
+    {
+        $result = $next($request);
+
+        return match (true) {
+            $result instanceof PromiseInterface => $result->then(fn($response) => $this->handle($response)),
+            $result instanceof ResponseInterface => $this->handle($result),
+            default => $result
+        };
+    }
+
+    private function handle($response)
+    {
+        if ($response instanceof ResponseInterface) {
+            $existing = $response->getHeaderLine('X-Middleware-Order');
+            $new = $existing ? $existing . ',second' : 'second';
+            return $response->withHeader('X-Middleware-Order', $new);
+        }
+        return $response;
+    }
+}
diff --git a/tests/Fixtures/Middlewares/ShortCircuitMiddleware.php b/tests/Fixtures/Middlewares/ShortCircuitMiddleware.php
new file mode 100644
index 0000000..04ef518
--- /dev/null
+++ b/tests/Fixtures/Middlewares/ShortCircuitMiddleware.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpMcp\Server\Tests\Fixtures\Middlewares;
+
+use Psr\Http\Message\ServerRequestInterface;
+use React\Http\Message\Response;
+
+class ShortCircuitMiddleware
+{
+    public function __invoke(ServerRequestInterface $request, callable $next)
+    {
+        if (str_contains($request->getUri()->getPath(), '/short-circuit')) {
+            return new Response(418, [], 'Short-circuited by middleware');
+        }
+        return $next($request);
+    }
+}
diff --git a/tests/Fixtures/Middlewares/ThirdMiddleware.php b/tests/Fixtures/Middlewares/ThirdMiddleware.php
new file mode 100644
index 0000000..fe647c3
--- /dev/null
+++ b/tests/Fixtures/Middlewares/ThirdMiddleware.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpMcp\Server\Tests\Fixtures\Middlewares;
+
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Message\ResponseInterface;
+use React\Promise\PromiseInterface;
+
+class ThirdMiddleware
+{
+    public function __invoke(ServerRequestInterface $request, callable $next)
+    {
+        $result = $next($request);
+
+        return match (true) {
+            $result instanceof PromiseInterface => $result->then(fn($response) => $this->handle($response)),
+            $result instanceof ResponseInterface => $this->handle($result),
+            default => $result
+        };
+    }
+
+    private function handle($response)
+    {
+        if ($response instanceof ResponseInterface) {
+            $existing = $response->getHeaderLine('X-Middleware-Order');
+            $new = $existing ? $existing . ',third' : 'third';
+            return $response->withHeader('X-Middleware-Order', $new);
+        }
+        return $response;
+    }
+}
diff --git a/tests/Fixtures/ServerScripts/HttpTestServer.php b/tests/Fixtures/ServerScripts/HttpTestServer.php
index 07d66ae..9bd6b86 100755
--- a/tests/Fixtures/ServerScripts/HttpTestServer.php
+++ b/tests/Fixtures/ServerScripts/HttpTestServer.php
@@ -10,6 +10,14 @@
 use PhpMcp\Server\Tests\Fixtures\General\ToolHandlerFixture;
 use PhpMcp\Server\Tests\Fixtures\General\ResourceHandlerFixture;
 use PhpMcp\Server\Tests\Fixtures\General\PromptHandlerFixture;
+use PhpMcp\Server\Tests\Fixtures\General\RequestAttributeChecker;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\HeaderMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\RequestAttributeMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\ShortCircuitMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\FirstMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\SecondMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\ThirdMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\ErrorMiddleware;
 use Psr\Log\AbstractLogger;
 use Psr\Log\NullLogger;
 
@@ -32,11 +40,22 @@ public function log($level, \Stringable|string $message, array $context = []): v
         ->withServerInfo('HttpIntegrationTestServer', '0.1.0')
         ->withLogger($logger)
         ->withTool([ToolHandlerFixture::class, 'greet'], 'greet_http_tool')
+        ->withTool([RequestAttributeChecker::class, 'checkAttribute'], 'check_request_attribute_tool')
         ->withResource([ResourceHandlerFixture::class, 'getStaticText'], "test://http/static", 'static_http_resource')
         ->withPrompt([PromptHandlerFixture::class, 'generateSimpleGreeting'], 'simple_http_prompt')
         ->build();
 
-    $transport = new HttpServerTransport($host, $port, $mcpPathPrefix);
+    $middlewares = [
+        new HeaderMiddleware(),
+        new RequestAttributeMiddleware(),
+        new ShortCircuitMiddleware(),
+        new FirstMiddleware(),
+        new SecondMiddleware(),
+        new ThirdMiddleware(),
+        new ErrorMiddleware()
+    ];
+
+    $transport = new HttpServerTransport($host, $port, $mcpPathPrefix, null, $middlewares);
     $server->listen($transport);
 
     exit(0);
diff --git a/tests/Fixtures/ServerScripts/StreamableHttpTestServer.php b/tests/Fixtures/ServerScripts/StreamableHttpTestServer.php
index b7cdf6a..2c85436 100755
--- a/tests/Fixtures/ServerScripts/StreamableHttpTestServer.php
+++ b/tests/Fixtures/ServerScripts/StreamableHttpTestServer.php
@@ -10,6 +10,14 @@
 use PhpMcp\Server\Tests\Fixtures\General\ToolHandlerFixture;
 use PhpMcp\Server\Tests\Fixtures\General\ResourceHandlerFixture;
 use PhpMcp\Server\Tests\Fixtures\General\PromptHandlerFixture;
+use PhpMcp\Server\Tests\Fixtures\General\RequestAttributeChecker;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\HeaderMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\RequestAttributeMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\ShortCircuitMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\FirstMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\SecondMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\ThirdMiddleware;
+use PhpMcp\Server\Tests\Fixtures\Middlewares\ErrorMiddleware;
 use PhpMcp\Server\Defaults\InMemoryEventStore;
 use Psr\Log\AbstractLogger;
 use Psr\Log\NullLogger;
@@ -41,17 +49,29 @@ public function log($level, \Stringable|string $message, array $context = []): v
         ->withTool([ToolHandlerFixture::class, 'greet'], 'greet_streamable_tool')
         ->withTool([ToolHandlerFixture::class, 'sum'], 'sum_streamable_tool') // For batch testing
         ->withTool([ToolHandlerFixture::class, 'toolReadsContext'], 'tool_reads_context') // for Context testing
+        ->withTool([RequestAttributeChecker::class, 'checkAttribute'], 'check_request_attribute_tool')
         ->withResource([ResourceHandlerFixture::class, 'getStaticText'], "test://streamable/static", 'static_streamable_resource')
         ->withPrompt([PromptHandlerFixture::class, 'generateSimpleGreeting'], 'simple_streamable_prompt')
         ->build();
 
+    $middlewares = [
+        new HeaderMiddleware(),
+        new RequestAttributeMiddleware(),
+        new ShortCircuitMiddleware(),
+        new FirstMiddleware(),
+        new SecondMiddleware(),
+        new ThirdMiddleware(),
+        new ErrorMiddleware()
+    ];
+
     $transport = new StreamableHttpServerTransport(
         host: $host,
         port: $port,
         mcpPath: $mcpPath,
         enableJsonResponse: $enableJsonResponse,
         stateless: $stateless,
-        eventStore: $eventStore
+        eventStore: $eventStore,
+        middlewares: $middlewares
     );
 
     $server->listen($transport);
diff --git a/tests/Integration/HttpServerTransportTest.php b/tests/Integration/HttpServerTransportTest.php
index dab32bd..44534b4 100644
--- a/tests/Integration/HttpServerTransportTest.php
+++ b/tests/Integration/HttpServerTransportTest.php
@@ -259,7 +259,7 @@
 
     expect($toolListResponse['id'])->toBe('tool-list-http-1');
     expect($toolListResponse)->not->toHaveKey('error');
-    expect($toolListResponse['result']['tools'])->toBeArray()->toHaveCount(1);
+    expect($toolListResponse['result']['tools'])->toBeArray()->toHaveCount(2);
     expect($toolListResponse['result']['tools'][0]['name'])->toBe('greet_http_tool');
 
     $this->sseClient->close();
@@ -417,3 +417,96 @@
         $this->fail("Request to unknown path failed with unexpected error: " . $e->getMessage());
     }
 })->group('integration', 'http_transport');
+
+it('executes middleware that adds headers to response', function () {
+    $this->sseClient = new MockSseClient();
+    $sseBaseUrl = "http://" . HTTP_SERVER_HOST . ":" . $this->port . "/" . HTTP_MCP_PATH_PREFIX . "/sse";
+
+    // 1. Connect
+    await($this->sseClient->connect($sseBaseUrl));
+    await(delay(0.05, $this->loop));
+
+    // 2. Check that the middleware-added header is present in the response
+    expect($this->sseClient->lastConnectResponse->getHeaderLine('X-Test-Middleware'))->toBe('header-added');
+
+    $this->sseClient->close();
+})->group('integration', 'http_transport', 'middleware');
+
+it('executes middleware that modifies request attributes', function () {
+    $this->sseClient = new MockSseClient();
+    $sseBaseUrl = "http://" . HTTP_SERVER_HOST . ":" . $this->port . "/" . HTTP_MCP_PATH_PREFIX . "/sse";
+
+    // 1. Connect 
+    await($this->sseClient->connect($sseBaseUrl));
+    await(delay(0.05, $this->loop));
+
+    // 2. Initialize
+    await($this->sseClient->sendHttpRequest('init-middleware-attr', 'initialize', [
+        'protocolVersion' => Protocol::LATEST_PROTOCOL_VERSION,
+        'clientInfo' => ['name' => 'MiddlewareTestClient'],
+        'capabilities' => []
+    ]));
+    await($this->sseClient->getNextMessageResponse('init-middleware-attr'));
+    await($this->sseClient->sendHttpNotification('notifications/initialized'));
+    await(delay(0.05, $this->loop));
+
+    // 3. Call tool that checks for middleware-added attribute
+    await($this->sseClient->sendHttpRequest('tool-attr-check', 'tools/call', [
+        'name' => 'check_request_attribute_tool',
+        'arguments' => []
+    ]));
+    $toolResponse = await($this->sseClient->getNextMessageResponse('tool-attr-check'));
+
+    expect($toolResponse['result']['content'][0]['text'])->toBe('middleware-value-found: middleware-value');
+
+    $this->sseClient->close();
+})->group('integration', 'http_transport', 'middleware');
+
+it('executes middleware that can short-circuit request processing', function () {
+    $browser = new Browser($this->loop);
+    $shortCircuitUrl = "http://" . HTTP_SERVER_HOST . ":" . $this->port . "/" . HTTP_MCP_PATH_PREFIX . "/short-circuit";
+
+    $promise = $browser->get($shortCircuitUrl);
+
+    try {
+        $response = await(timeout($promise, HTTP_PROCESS_TIMEOUT_SECONDS - 2, $this->loop));
+        $this->fail("Expected a 418 status code response, but request succeeded");
+    } catch (ResponseException $e) {
+        expect($e->getResponse()->getStatusCode())->toBe(418);
+        $body = (string) $e->getResponse()->getBody();
+        expect($body)->toBe('Short-circuited by middleware');
+    } catch (\Throwable $e) {
+        $this->fail("Short-circuit middleware test failed: " . $e->getMessage());
+    }
+})->group('integration', 'http_transport', 'middleware');
+
+it('executes multiple middlewares in correct order', function () {
+    $this->sseClient = new MockSseClient();
+    $sseBaseUrl = "http://" . HTTP_SERVER_HOST . ":" . $this->port . "/" . HTTP_MCP_PATH_PREFIX . "/sse";
+
+    // 1. Connect
+    await($this->sseClient->connect($sseBaseUrl));
+    await(delay(0.05, $this->loop));
+
+    // 2. Check that headers from multiple middlewares are present in correct order
+    expect($this->sseClient->lastConnectResponse->getHeaderLine('X-Middleware-Order'))->toBe('third,second,first');
+
+    $this->sseClient->close();
+})->group('integration', 'http_transport', 'middleware');
+
+it('handles middleware that throws exceptions gracefully', function () {
+    $browser = new Browser($this->loop);
+    $errorUrl = "http://" . HTTP_SERVER_HOST . ":" . $this->port . "/" . HTTP_MCP_PATH_PREFIX . "/error-middleware";
+
+    $promise = $browser->get($errorUrl);
+
+    try {
+        await(timeout($promise, HTTP_PROCESS_TIMEOUT_SECONDS - 2, $this->loop));
+        $this->fail("Error middleware should have thrown an exception.");
+    } catch (ResponseException $e) {
+        expect($e->getResponse()->getStatusCode())->toBe(500);
+        $body = (string) $e->getResponse()->getBody();
+        // ReactPHP handles exceptions and returns a generic error message
+        expect($body)->toContain('Internal Server Error');
+    }
+})->group('integration', 'http_transport', 'middleware');
diff --git a/tests/Integration/StreamableHttpServerTransportTest.php b/tests/Integration/StreamableHttpServerTransportTest.php
index f7b7ebb..6d88c8d 100644
--- a/tests/Integration/StreamableHttpServerTransportTest.php
+++ b/tests/Integration/StreamableHttpServerTransportTest.php
@@ -217,7 +217,7 @@
         expect($toolListResult['statusCode'])->toBe(200);
         expect($toolListResult['body']['id'])->toBe('tool-list-json-1');
         expect($toolListResult['body']['result']['tools'])->toBeArray();
-        expect(count($toolListResult['body']['result']['tools']))->toBe(3);
+        expect(count($toolListResult['body']['result']['tools']))->toBe(4);
         expect($toolListResult['body']['result']['tools'][0]['name'])->toBe('greet_streamable_tool');
         expect($toolListResult['body']['result']['tools'][1]['name'])->toBe('sum_streamable_tool');
         expect($toolListResult['body']['result']['tools'][2]['name'])->toBe('tool_reads_context');
@@ -460,7 +460,7 @@
         expect($toolListResponse['id'])->toBe('tool-list-stream-1');
         expect($toolListResponse)->not->toHaveKey('error');
         expect($toolListResponse['result']['tools'])->toBeArray();
-        expect(count($toolListResponse['result']['tools']))->toBe(3);
+        expect(count($toolListResponse['result']['tools']))->toBe(4);
         expect($toolListResponse['result']['tools'][0]['name'])->toBe('greet_streamable_tool');
         expect($toolListResponse['result']['tools'][1]['name'])->toBe('sum_streamable_tool');
         expect($toolListResponse['result']['tools'][2]['name'])->toBe('tool_reads_context');
@@ -663,7 +663,7 @@
         expect($toolListResult['body']['id'])->toBe('tool-list-stateless-1');
         expect($toolListResult['body'])->not->toHaveKey('error');
         expect($toolListResult['body']['result']['tools'])->toBeArray();
-        expect(count($toolListResult['body']['result']['tools']))->toBe(3);
+        expect(count($toolListResult['body']['result']['tools']))->toBe(4);
         expect($toolListResult['body']['result']['tools'][0]['name'])->toBe('greet_streamable_tool');
         expect($toolListResult['body']['result']['tools'][1]['name'])->toBe('sum_streamable_tool');
         expect($toolListResult['body']['result']['tools'][2]['name'])->toBe('tool_reads_context');
@@ -862,3 +862,103 @@
         expect($decodedBody['error']['message'])->toContain('Invalid or expired session');
     }
 })->group('integration', 'streamable_http_json');
+
+it('executes middleware that adds headers to response', function () {
+    $this->process = new Process($this->jsonModeCommand, getcwd() ?: null, null, []);
+    $this->process->start();
+    $this->jsonClient = new MockJsonHttpClient(STREAMABLE_HTTP_HOST, $this->port, STREAMABLE_MCP_PATH);
+    await(delay(0.1));
+
+    // 1. Send a request and check that middleware-added header is present
+    $response = await($this->jsonClient->sendRequest('initialize', [
+        'protocolVersion' => Protocol::LATEST_PROTOCOL_VERSION,
+        'clientInfo' => ['name' => 'MiddlewareTestClient'],
+        'capabilities' => []
+    ], 'init-middleware-headers'));
+
+    // Check that the response has the header added by middleware
+    expect($this->jsonClient->lastResponseHeaders)->toContain('X-Test-Middleware: header-added');
+})->group('integration', 'streamable_http', 'middleware');
+
+it('executes middleware that modifies request attributes', function () {
+    $this->process = new Process($this->jsonModeCommand, getcwd() ?: null, null, []);
+    $this->process->start();
+    $this->jsonClient = new MockJsonHttpClient(STREAMABLE_HTTP_HOST, $this->port, STREAMABLE_MCP_PATH);
+    await(delay(0.1));
+
+    // 1. Initialize 
+    await($this->jsonClient->sendRequest('initialize', [
+        'protocolVersion' => Protocol::LATEST_PROTOCOL_VERSION,
+        'clientInfo' => ['name' => 'MiddlewareAttrTestClient', 'version' => '1.0'],
+        'capabilities' => []
+    ], 'init-middleware-attr'));
+    await($this->jsonClient->sendNotification('notifications/initialized'));
+
+    // 2. Call tool that checks for middleware-added attribute
+    $toolResponse = await($this->jsonClient->sendRequest('tools/call', [
+        'name' => 'check_request_attribute_tool',
+        'arguments' => []
+    ], 'tool-attr-check'));
+
+    expect($toolResponse['body']['result']['content'][0]['text'])->toBe('middleware-value-found: middleware-value');
+})->group('integration', 'streamable_http', 'middleware');
+
+it('executes middleware that can short-circuit request processing', function () {
+    $this->process = new Process($this->jsonModeCommand, getcwd() ?: null, null, []);
+    $this->process->start();
+    await(delay(0.1));
+
+    $browser = new Browser();
+    $shortCircuitUrl = "http://" . STREAMABLE_HTTP_HOST . ":" . $this->port . "/" . STREAMABLE_MCP_PATH . "/short-circuit";
+
+    $promise = $browser->get($shortCircuitUrl);
+
+    try {
+        $response = await(timeout($promise, STREAMABLE_HTTP_PROCESS_TIMEOUT - 2));
+        $this->fail("Expected a 418 status code response, but request succeeded");
+    } catch (ResponseException $e) {
+        expect($e->getResponse()->getStatusCode())->toBe(418);
+        $body = (string) $e->getResponse()->getBody();
+        expect($body)->toBe('Short-circuited by middleware');
+    } catch (\Throwable $e) {
+        $this->fail("Short-circuit middleware test failed: " . $e->getMessage());
+    }
+})->group('integration', 'streamable_http', 'middleware');
+
+it('executes multiple middlewares in correct order', function () {
+    $this->process = new Process($this->jsonModeCommand, getcwd() ?: null, null, []);
+    $this->process->start();
+    $this->jsonClient = new MockJsonHttpClient(STREAMABLE_HTTP_HOST, $this->port, STREAMABLE_MCP_PATH);
+    await(delay(0.1));
+
+    // 1. Send a request and check middleware order
+    await($this->jsonClient->sendRequest('initialize', [
+        'protocolVersion' => Protocol::LATEST_PROTOCOL_VERSION,
+        'clientInfo' => ['name' => 'MiddlewareOrderTestClient'],
+        'capabilities' => []
+    ], 'init-middleware-order'));
+
+    // Check that headers from multiple middlewares are present in correct order
+    expect($this->jsonClient->lastResponseHeaders)->toContain('X-Middleware-Order: third,second,first');
+})->group('integration', 'streamable_http', 'middleware');
+
+it('handles middleware that throws exceptions gracefully', function () {
+    $this->process = new Process($this->jsonModeCommand, getcwd() ?: null, null, []);
+    $this->process->start();
+    await(delay(0.1));
+
+    $browser = new Browser();
+    $errorUrl = "http://" . STREAMABLE_HTTP_HOST . ":" . $this->port . "/" . STREAMABLE_MCP_PATH . "/error-middleware";
+
+    $promise = $browser->get($errorUrl);
+
+    try {
+        await(timeout($promise, STREAMABLE_HTTP_PROCESS_TIMEOUT - 2));
+        $this->fail("Error middleware should have thrown an exception.");
+    } catch (ResponseException $e) {
+        expect($e->getResponse()->getStatusCode())->toBe(500);
+        $body = (string) $e->getResponse()->getBody();
+        // ReactPHP handles exceptions and returns a generic error message
+        expect($body)->toContain('Internal Server Error');
+    }
+})->group('integration', 'streamable_http', 'middleware');
diff --git a/tests/Mocks/Clients/MockJsonHttpClient.php b/tests/Mocks/Clients/MockJsonHttpClient.php
index 364c90b..cae47d7 100644
--- a/tests/Mocks/Clients/MockJsonHttpClient.php
+++ b/tests/Mocks/Clients/MockJsonHttpClient.php
@@ -13,6 +13,7 @@ class MockJsonHttpClient
     public Browser $browser;
     public string $baseUrl;
     public ?string $sessionId = null;
+    public array $lastResponseHeaders = []; // Store last response headers for testing
 
     public function __construct(string $host, int $port, string $mcpPath, int $timeout = 2)
     {
@@ -37,6 +38,14 @@ public function sendRequest(string $method, array $params = [], ?string $id = nu
 
         return $this->browser->post($this->baseUrl, $headers, $body)
             ->then(function (ResponseInterface $response) use ($method) {
+                // Store response headers for testing
+                $this->lastResponseHeaders = [];
+                foreach ($response->getHeaders() as $name => $values) {
+                    foreach ($values as $value) {
+                        $this->lastResponseHeaders[] = "{$name}: {$value}";
+                    }
+                }
+
                 $bodyContent = (string) $response->getBody()->getContents();
                 $statusCode = $response->getStatusCode();
 
diff --git a/tests/Mocks/Clients/MockSseClient.php b/tests/Mocks/Clients/MockSseClient.php
index ad54374..1423a6e 100644
--- a/tests/Mocks/Clients/MockSseClient.php
+++ b/tests/Mocks/Clients/MockSseClient.php
@@ -22,6 +22,7 @@ class MockSseClient
     private array $receivedSseEvents = []; // Stores raw SSE events (type, data, id)
     public ?string $endpointUrl = null; // The /message endpoint URL provided by server
     public ?string $clientId = null; // The clientId from the /message endpoint URL
+    public ?ResponseInterface $lastConnectResponse = null; // Last connect response for header testing
 
     public function __construct(int $timeout = 2)
     {
@@ -32,6 +33,7 @@ public function connect(string $sseBaseUrl): PromiseInterface
     {
         return $this->browser->requestStreaming('GET', $sseBaseUrl)
             ->then(function (ResponseInterface $response) {
+                $this->lastConnectResponse = $response; // Store response for header testing
                 if ($response->getStatusCode() !== 200) {
                     $body = (string) $response->getBody();
                     throw new \RuntimeException("SSE connection failed with status {$response->getStatusCode()}: {$body}");