diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 0b6a230..ece2bc5 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -1,38 +1,57 @@
 name: CI
 on:
-    - push
+    push:
+        branches:
+            - master
+    pull_request:
 jobs:
     phpstan:
         runs-on: ubuntu-latest
         steps:
             -   name: Checkout
-                uses: actions/checkout@v2
+                uses: actions/checkout@v4
 
             -   name: Setup PHP, with composer and extensions
                 uses: shivammathur/setup-php@v2
                 with:
-                    php-version: 7.3
+                    php-version: '8.0'
 
             -   name: Install dependencies with Composer
-                uses: ramsey/composer-install@v1
+                uses: ramsey/composer-install@v3
 
             -   name: Run phpstan
                 run: vendor/bin/phpstan analyse --level=6 src/
     tests:
         strategy:
+            fail-fast: false
             matrix:
                 dependencies:
                     - highest
                     - lowest
+                # PHP 7.3 and 7.4 are not built here: no laminas-diactoros release
+                # that Composer 2.10+ accepts as a psr/http-factory-implementation
+                # provider supports them, so the dev dependencies cannot even be
+                # installed on those versions.
                 php-versions:
-                    - 7.3
-                    - 7.4
-                    - 8.0
-                    - 8.1
+                    - '8.0'
+                    - '8.1'
+                    - '8.2'
+                    - '8.3'
+                exclude:
+                    # Lowest bounds of the dev dependencies (Slim 3.0, Pimple 3.0,
+                    # vfsStream 1.6.8) were released before PHP 8.1 and fatal on load
+                    # there. That is a limitation of those old releases, not of this
+                    # library: every tested PHP version is covered by the highest jobs.
+                    -   dependencies: lowest
+                        php-versions: '8.1'
+                    -   dependencies: lowest
+                        php-versions: '8.2'
+                    -   dependencies: lowest
+                        php-versions: '8.3'
         runs-on: ubuntu-latest
         steps:
             -   name: Checkout
-                uses: actions/checkout@v2
+                uses: actions/checkout@v4
 
             -   name: Setup PHP, with composer and extensions
                 uses: shivammathur/setup-php@v2
@@ -40,7 +59,7 @@ jobs:
                     php-version: ${{ matrix.php-versions }}
 
             -   name: Install dependencies with Composer
-                uses: ramsey/composer-install@v1
+                uses: ramsey/composer-install@v3
                 with:
                     dependency-versions: ${{ matrix.dependencies }}
 
diff --git a/README.md b/README.md
index cf9b6ff..63e4e7a 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,14 @@ Sometimes you want to have control when enable or disable PHP Debug Bar:
 We allow you to disable attaching phpdebugbar using `X-Enable-Debug-Bar: false` header, cookie or request attribute.
 To force enable just send request with `X-Enable-Debug-Bar` header, cookie or request attribute with `true` value.
 
+### AJAX requests
+
+Requests sent with `X-Requested-With: XMLHttpRequest` are attached to the debug bar
+already initialized by the main request: the middleware appends only the collected data
+of the AJAX request (rendered as a `(ajax)` dataset) instead of the initialization code
+and assets. Without it every AJAX response would create another debug bar on top of the
+existing one.
+
 ### PSR-17
 
 This package isn't require any PSR-7 implementation - you need to provide it by own. Middleware require ResponseFactory and StreamFactory interfaces. [List of existing interfaces](https://packagist.org/providers/psr/http-factory-implementation).
diff --git a/composer.json b/composer.json
index 77bcca9..974638e 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
     ],
     "require": {
         "php": "^7.3 || ^8.0",
-        "maximebf/debugbar": "^1.4",
+        "maximebf/debugbar": "^1.18",
         "psr/http-server-handler": "^1.0",
         "psr/http-server-middleware": "^1.0",
         "psr/container-implementation": "^1.0 || ^2.0",
@@ -23,6 +23,7 @@
     "require-dev": {
         "phpunit/phpunit": "^9.1.4",
         "mikey179/vfsstream": "^1.6.8",
+        "symfony/var-dumper": "^4.4.30",
         "slim/slim": "^3.0",
         "mezzio/mezzio": "^3.0",
         "mezzio/mezzio-fastroute": "^3.0.1",
diff --git a/src/PhpDebugBarMiddleware.php b/src/PhpDebugBarMiddleware.php
index 8d4a892..82d1a0f 100644
--- a/src/PhpDebugBarMiddleware.php
+++ b/src/PhpDebugBarMiddleware.php
@@ -62,7 +62,7 @@ public function process(ServerRequest $request, RequestHandler $handler): Respon
         }
 
         if ($this->isHtmlResponse($response)) {
-            return $this->attachDebugBarToHtmlResponse($response);
+            return $this->attachDebugBarToHtmlResponse($response, !$this->isXmlHttpRequest($request));
         }
 
         return $this->prepareHtmlResponseWithDebugBar($response);
@@ -122,10 +122,16 @@ private function prepareHtmlResponseWithDebugBar(Response $response): Response
             ->withAddedHeader('Content-type', 'text/html');
     }
 
-    private function attachDebugBarToHtmlResponse(Response $response): Response
+    /**
+     * @param bool $initialize Render the debug bar initialization code and assets.
+     *                         Must be false for responses attached to an already
+     *                         initialized debug bar (XMLHttpRequest), otherwise a
+     *                         second debug bar is created on top of the existing one.
+     */
+    private function attachDebugBarToHtmlResponse(Response $response, bool $initialize = true): Response
     {
-        $head = $this->debugBarRenderer->renderHead();
-        $body = $this->debugBarRenderer->render();
+        $head = $initialize ? $this->debugBarRenderer->renderHead() : '';
+        $body = $this->debugBarRenderer->render($initialize);
         $responseBody = $response->getBody();
 
         if (! $responseBody->eof() && $responseBody->isSeekable()) {
@@ -205,6 +211,11 @@ private function isHtml(MessageInterface $message, string $headerName): bool
         return strpos($message->getHeaderLine($headerName), 'text/html') !== false;
     }
 
+    private function isXmlHttpRequest(ServerRequest $request): bool
+    {
+        return strtolower($request->getHeaderLine('X-Requested-With')) === 'xmlhttprequest';
+    }
+
     private function isRedirect(Response $response): bool
     {
         $statusCode = $response->getStatusCode();
diff --git a/test/AbstractMiddlewareRunnerTest.php b/test/AbstractMiddlewareRunnerTest.php
index a7dd572..7723332 100644
--- a/test/AbstractMiddlewareRunnerTest.php
+++ b/test/AbstractMiddlewareRunnerTest.php
@@ -32,6 +32,27 @@ final public function testAppendJsIntoHtmlContent(): void
         $this->assertStringContainsString('"/phpdebugbar/debugbar.js"', $responseBody);
     }
 
+    final public function testNotAppendInitializationCodeIntoXmlHttpRequestContent(): void
+    {
+        $response = $this->dispatchApplication([
+            'REQUEST_URI' => '/hello',
+            'REQUEST_METHOD' => 'GET',
+            'HTTP_ACCEPT' => 'text/html',
+            'HTTP_X_REQUESTED_WITH' => 'XMLHttpRequest',
+        ], [
+            '/hello' => function (ServerRequestInterface $request) {
+                return new Response\HtmlResponse('Hello!');
+            },
+        ]);
+
+        $responseBody = (string) $response->getBody();
+
+        $this->assertStringContainsString('Hello!', $responseBody);
+        $this->assertStringContainsString('phpdebugbar.addDataSet(', $responseBody);
+        $this->assertStringNotContainsString('var phpdebugbar = new PhpDebugBar.DebugBar();', $responseBody);
+        $this->assertStringNotContainsString('"/phpdebugbar/debugbar.js"', $responseBody);
+    }
+
     final public function testGetStatics(): void
     {
         $response = $this->dispatchApplication([
diff --git a/test/MezzioTest.php b/test/MezzioTest.php
index f3e340d..92abd8f 100644
--- a/test/MezzioTest.php
+++ b/test/MezzioTest.php
@@ -22,6 +22,7 @@
 use Mezzio\Container\ServerRequestErrorResponseGeneratorFactory;
 use Mezzio\MiddlewareContainer;
 use Mezzio\MiddlewareFactory;
+use Mezzio\MiddlewareFactoryInterface;
 use Mezzio\Response\ServerRequestErrorResponseGenerator;
 use Mezzio\Router\FastRouteRouter;
 use Mezzio\Router\FastRouteRouterFactory;
@@ -34,6 +35,7 @@
 use Mezzio\Router\RouterInterface;
 use Laminas\HttpHandlerRunner\Emitter\EmitterInterface;
 use Laminas\HttpHandlerRunner\RequestHandlerRunner;
+use Laminas\HttpHandlerRunner\RequestHandlerRunnerInterface;
 use Laminas\ServiceManager\Factory\InvokableFactory;
 use Laminas\ServiceManager\ServiceManager;
 use Laminas\Stratigility\MiddlewarePipe;
@@ -104,6 +106,8 @@ private function createContainer(array $server): ContainerInterface
         $serviceManagerConfig['factories'][DispatchMiddleware::class] = DispatchMiddlewareFactory::class;
         $serviceManagerConfig['factories'][ResponseFactory::class] = InvokableFactory::class;
         $serviceManagerConfig['factories'][StreamFactory::class] = InvokableFactory::class;
+        $serviceManagerConfig['aliases'][MiddlewareFactoryInterface::class] = MiddlewareFactory::class;
+        $serviceManagerConfig['aliases'][RequestHandlerRunnerInterface::class] = RequestHandlerRunner::class;
         $serviceManagerConfig['aliases'][RouterInterface::class] = FastRouteRouter::class;
         $serviceManagerConfig['aliases'][\Mezzio\ApplicationPipeline::class] = MiddlewarePipe::class;
         $serviceManagerConfig['aliases'][ResponseFactoryInterface::class] = ResponseFactory::class;
diff --git a/test/PhpDebugBarMiddlewareTest.php b/test/PhpDebugBarMiddlewareTest.php
index 423b195..b9bc14b 100644
--- a/test/PhpDebugBarMiddlewareTest.php
+++ b/test/PhpDebugBarMiddlewareTest.php
@@ -29,7 +29,9 @@ protected function setUp(): void
         $this->debugbarRenderer = $this->getMockBuilder(JavascriptRenderer::class)->disableOriginalConstructor()->getMock();
         $this->debugbarRenderer->method('renderHead')->willReturn('RenderHead');
         $this->debugbarRenderer->method('getBaseUrl')->willReturn('/phpdebugbar');
-        $this->debugbarRenderer->method('render')->willReturn('RenderBody');
+        $this->debugbarRenderer->method('render')->willReturnCallback(function (bool $initialize = true): string {
+            return $initialize ? 'RenderBody' : 'RenderBodyWithoutInit';
+        });
         $responseFactory = new ResponseFactory();
         $streamFactory = new StreamFactory();
 
@@ -244,6 +246,45 @@ public function testForceNotAttachDebugbarIfAttributePresents(): void
         $this->assertSame('ResponseBody', (string) $result->getBody());
     }
 
+    public function testNotRenderInitializationCodeForXmlHttpRequest(): void
+    {
+        $request = new ServerRequest([], [], null, null, 'php://input', ['Accept' => 'text/html', 'X-Requested-With' => 'XMLHttpRequest']);
+        $response = new Response('php://memory', 200, ['Content-Type' => 'text/html']);
+        $response->getBody()->write('ResponseBody');
+        $requestHandler = new RequestHandlerStub($response);
+
+        $result = $this->middleware->process($request, $requestHandler);
+
+        $this->assertTrue($requestHandler->isCalled(), 'Request handler is not called');
+        $this->assertSame($response, $result);
+        $this->assertSame('ResponseBodyRenderBodyWithoutInit', (string) $result->getBody());
+    }
+
+    public function testNotRenderInitializationCodeForLowercasedXmlHttpRequestHeaderValue(): void
+    {
+        $request = new ServerRequest([], [], null, null, 'php://input', ['Accept' => 'text/html', 'X-Requested-With' => 'xmlhttprequest']);
+        $response = new Response('php://memory', 200, ['Content-Type' => 'text/html']);
+        $response->getBody()->write('ResponseBody');
+        $requestHandler = new RequestHandlerStub($response);
+
+        $result = $this->middleware->process($request, $requestHandler);
+
+        $this->assertSame('ResponseBodyRenderBodyWithoutInit', (string) $result->getBody());
+    }
+
+    public function testNotAttachDebugbarToXmlHttpRequestIfForceDisabled(): void
+    {
+        $request = new ServerRequest([], [], null, null, 'php://input', ['Accept' => 'text/html', 'X-Requested-With' => 'XMLHttpRequest', 'X-Enable-Debug-Bar' => 'false']);
+        $response = new Response('php://memory', 200, ['Content-Type' => 'text/html']);
+        $response->getBody()->write('ResponseBody');
+        $requestHandler = new RequestHandlerStub($response);
+
+        $result = $this->middleware->process($request, $requestHandler);
+
+        $this->assertSame($response, $result);
+        $this->assertSame('ResponseBody', (string) $result->getBody());
+    }
+
     public function testAppendsToEndOfHtmlResponse(): void
     {
         $html = '<html><head><title>Foo</title></head><body>Content</body>';