diff --git a/src/App.php b/src/App.php
index 3b7f3c1..4fcb4c8 100644
--- a/src/App.php
+++ b/src/App.php
@@ -2,12 +2,11 @@
 
 namespace FrameworkX;
 
-use FrameworkX\Io\LogStreamHandler;
 use FrameworkX\Io\MiddlewareHandler;
-use FrameworkX\Io\ReactiveHandler;
 use FrameworkX\Io\RedirectHandler;
 use FrameworkX\Io\RouteHandler;
-use FrameworkX\Io\SapiHandler;
+use FrameworkX\Runner\HttpServerRunner;
+use FrameworkX\Runner\SapiRunner;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use React\Http\Message\Response;
@@ -23,8 +22,8 @@ class App
     /** @var RouteHandler */
     private $router;
 
-    /** @var ReactiveHandler|SapiHandler */
-    private $sapi;
+    /** @var HttpServerRunner|SapiRunner */
+    private $runner;
 
     /**
      * Instantiate new X application
@@ -127,7 +126,7 @@ public function __construct(...$middleware)
 
         $this->router = $router;
         $this->handler = new MiddlewareHandler($handlers);
-        $this->sapi = $container->getSapi();
+        $this->runner = $container->getRunner();
     }
 
     /**
@@ -241,7 +240,7 @@ public function redirect(string $route, string $target, int $code = Response::ST
      * Runs the app to handle HTTP requests according to any registered routes and middleware.
      *
      * This is where the magic happens: When executed on the command line (CLI),
-     * this will run the powerful reactive request handler built on top of
+     * this will run the powerful reactive application runner built on top of
      * ReactPHP. This works by running the efficient built-in HTTP web server to
      * handle incoming HTTP requests through ReactPHP's HTTP and socket server.
      * This async execution mode is usually recommended as it can efficiently
@@ -252,14 +251,14 @@ public function redirect(string $route, string $target, int $code = Response::ST
      * When executed behind traditional PHP SAPIs (PHP-FPM, FastCGI, Apache, etc.),
      * this will handle a single request and run until a single response is sent.
      * This is particularly useful because it allows you to run the exact same
-     * app in any environment.
+     * application code in any environment.
      *
-     * @see ReactiveHandler::run()
-     * @see SapiHandler::run()
+     * @see HttpServerRunner::__invoke()
+     * @see SapiRunner::__invoke()
      */
     public function run(): void
     {
-        $this->sapi->run(\Closure::fromCallable([$this, 'handleRequest']));
+        ($this->runner)(\Closure::fromCallable([$this, 'handleRequest']));
     }
 
     /**
diff --git a/src/Container.php b/src/Container.php
index 507a20f..da97d50 100644
--- a/src/Container.php
+++ b/src/Container.php
@@ -3,9 +3,9 @@
 namespace FrameworkX;
 
 use FrameworkX\Io\LogStreamHandler;
-use FrameworkX\Io\ReactiveHandler;
 use FrameworkX\Io\RouteHandler;
-use FrameworkX\Io\SapiHandler;
+use FrameworkX\Runner\HttpServerRunner;
+use FrameworkX\Runner\SapiRunner;
 use Psr\Container\ContainerInterface;
 use Psr\Http\Message\ServerRequestInterface;
 
@@ -169,8 +169,8 @@ public function getObject(string $class) /*: object (PHP 7.2+) */
                 return $this; // @phpstan-ignore-line returns instanceof `T`
             } elseif ($class === RouteHandler::class) {
                 return new RouteHandler($this); // @phpstan-ignore-line returns instanceof `T`
-            } elseif ($class === ReactiveHandler::class) {
-                return new ReactiveHandler(new LogStreamHandler('php://output'), $this->getEnv('X_LISTEN')); // @phpstan-ignore-line returns instanceof `T`
+            } elseif ($class === HttpServerRunner::class) {
+                return new HttpServerRunner(new LogStreamHandler('php://output'), $this->getEnv('X_LISTEN')); // @phpstan-ignore-line returns instanceof `T`
             }
             return new $class();
         }
@@ -179,16 +179,16 @@ public function getObject(string $class) /*: object (PHP 7.2+) */
     }
 
     /**
-     * [Internal] Get SAPI handler from container
+     * [Internal] Get the app runner appropriate for this environment from container
      *
-     * @return ReactiveHandler|SapiHandler
+     * @return HttpServerRunner|SapiRunner
      * @throws \TypeError if container config or factory returns an unexpected type
      * @throws \Throwable if container factory function throws unexpected exception
      * @internal
      */
-    public function getSapi() /*: ReactiveHandler|SapiHandler (PHP 8.0+) */
+    public function getRunner() /*: HttpServerRunner|SapiRunner (PHP 8.0+) */
     {
-        return $this->getObject(\PHP_SAPI === 'cli' ? ReactiveHandler::class : SapiHandler::class);
+        return $this->getObject(\PHP_SAPI === 'cli' ? HttpServerRunner::class : SapiRunner::class);
     }
 
     /**
@@ -204,10 +204,10 @@ private function loadObject(string $name, int $depth = 64) /*: object (PHP 7.2+)
     {
         \assert(\is_array($this->container));
 
-        if ($name === ReactiveHandler::class && !\array_key_exists(ReactiveHandler::class, $this->container)) {
-            // special case: create ReactiveHandler with X_LISTEN environment variable
-            $this->container[ReactiveHandler::class] = static function (?string $X_LISTEN = null): ReactiveHandler {
-                return new ReactiveHandler(new LogStreamHandler('php://output'), $X_LISTEN);
+        if ($name === HttpServerRunner::class && !\array_key_exists(HttpServerRunner::class, $this->container)) {
+            // special case: create HttpServerRunner with X_LISTEN environment variable
+            $this->container[HttpServerRunner::class] = static function (?string $X_LISTEN = null): HttpServerRunner {
+                return new HttpServerRunner(new LogStreamHandler('php://output'), $X_LISTEN);
             };
         }
 
diff --git a/src/Io/ReactiveHandler.php b/src/Runner/HttpServerRunner.php
similarity index 85%
rename from src/Io/ReactiveHandler.php
rename to src/Runner/HttpServerRunner.php
index 2f26939..f3aa15f 100644
--- a/src/Io/ReactiveHandler.php
+++ b/src/Runner/HttpServerRunner.php
@@ -1,13 +1,15 @@
 <?php
 
-namespace FrameworkX\Io;
+namespace FrameworkX\Runner;
 
+use FrameworkX\Io\FiberHandler;
+use FrameworkX\Io\LogStreamHandler;
 use React\EventLoop\Loop;
 use React\Http\HttpServer;
 use React\Socket\SocketServer;
 
 /**
- * [Internal] Powerful reactive request handler built on top of ReactPHP.
+ * [Internal] Powerful reactive application runner built on top of ReactPHP.
  *
  * This is where the magic happens: The main `App` uses this class to run
  * ReactPHP's efficient HTTP server to handle incoming HTTP requests when
@@ -17,11 +19,11 @@
  * continue to run until it is interrupted by a signal.
  *
  * Note that this is an internal class only and nothing you should usually have
- * to care about. See also the `App` and `SapiHandler` for more details.
+ * to care about. See also the `App` and `SapiRunner` for more details.
  *
  * @internal
  */
-class ReactiveHandler
+class HttpServerRunner
 {
     /** @var LogStreamHandler */
     private $logger;
@@ -36,7 +38,11 @@ public function __construct(LogStreamHandler $logger, ?string $listenAddress)
         $this->listenAddress = $listenAddress ?? '127.0.0.1:8080';
     }
 
-    public function run(callable $handler): void
+    /**
+     * @param callable(\Psr\Http\Message\ServerRequestInterface):(\Psr\Http\Message\ResponseInterface|\React\Promise\PromiseInterface<\Psr\Http\Message\ResponseInterface>) $handler
+     * @return void
+     */
+    public function __invoke(callable $handler): void
     {
         $socket = new SocketServer($this->listenAddress);
 
diff --git a/src/Io/SapiHandler.php b/src/Runner/SapiRunner.php
similarity index 91%
rename from src/Io/SapiHandler.php
rename to src/Runner/SapiRunner.php
index 4f38426..c515d3d 100644
--- a/src/Io/SapiHandler.php
+++ b/src/Runner/SapiRunner.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace FrameworkX\Io;
+namespace FrameworkX\Runner;
 
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
@@ -11,21 +11,25 @@
 use React\Stream\ReadableStreamInterface;
 
 /**
- * [Internal] Request handler for traditional PHP SAPIs.
+ * [Internal] Application runner for traditional PHP SAPIs.
  *
- * This request handler will be used when executed behind traditional PHP SAPIs
+ * This application runner will be used when executed behind traditional PHP SAPIs
  * (PHP-FPM, FastCGI, Apache, etc.). It will handle a single request and run
  * until a single response is sent. This is particularly useful because it
- * allows you to run the exact same app in any environment.
+ * allows you to run the exact same application code in any environment.
  *
  * Note that this is an internal class only and nothing you should usually have
- * to care about. See also the `App` and `ReactiveHandler` for more details.
+ * to care about. See also the `App` and `HttpServerRunner` for more details.
  *
  * @internal
  */
-class SapiHandler
+class SapiRunner
 {
-    public function run(callable $handler): void
+    /**
+     * @param callable(ServerRequestInterface):(ResponseInterface|PromiseInterface<ResponseInterface>) $handler
+     * @return void
+     */
+    public function __invoke(callable $handler): void
     {
         $request = $this->requestFromGlobals();
 
diff --git a/tests/AppTest.php b/tests/AppTest.php
index b46f840..2efac15 100644
--- a/tests/AppTest.php
+++ b/tests/AppTest.php
@@ -7,8 +7,8 @@
 use FrameworkX\Container;
 use FrameworkX\ErrorHandler;
 use FrameworkX\Io\MiddlewareHandler;
-use FrameworkX\Io\ReactiveHandler;
 use FrameworkX\Io\RouteHandler;
+use FrameworkX\Runner\HttpServerRunner;
 use FrameworkX\Tests\Fixtures\InvalidAbstract;
 use FrameworkX\Tests\Fixtures\InvalidConstructorInt;
 use FrameworkX\Tests\Fixtures\InvalidConstructorIntersection;
@@ -92,7 +92,7 @@ public function testConstructWithContainerMockAssignsDefaultHandlersFromContaine
         $errorHandler = new ErrorHandler();
         $routeHandler = $this->createMock(RouteHandler::class);
 
-        $sapi = $this->createMock(ReactiveHandler::class);
+        $runner = $this->createMock(HttpServerRunner::class);
 
         $container = $this->createMock(Container::class);
         $container->expects($this->exactly(3))->method('getObject')->willReturnMap([
@@ -100,18 +100,18 @@ public function testConstructWithContainerMockAssignsDefaultHandlersFromContaine
             [ErrorHandler::class, $errorHandler],
             [RouteHandler::class, $routeHandler],
         ]);
-        $container->expects($this->once())->method('getSapi')->willReturn($sapi);
+        $container->expects($this->once())->method('getRunner')->willReturn($runner);
         assert($container instanceof Container);
 
         $app = new App($container);
 
-        $ref = new \ReflectionProperty($app, 'sapi');
+        $ref = new \ReflectionProperty($app, 'runner');
         if (PHP_VERSION_ID < 80100) {
             $ref->setAccessible(true);
         }
         $ret = $ref->getValue($app);
 
-        $this->assertSame($sapi, $ret);
+        $this->assertSame($runner, $ret);
 
         $ref = new ReflectionProperty($app, 'handler');
         if (PHP_VERSION_ID < 80100) {
@@ -138,13 +138,13 @@ public function testConstructWithContainerInstanceAssignsDefaultHandlersAndConta
         $container = new Container([]);
         $app = new App($container);
 
-        $ref = new \ReflectionProperty($app, 'sapi');
+        $ref = new \ReflectionProperty($app, 'runner');
         if (PHP_VERSION_ID < 80100) {
             $ref->setAccessible(true);
         }
         $ret = $ref->getValue($app);
 
-        $this->assertSame($container->getSapi(), $ret);
+        $this->assertSame($container->getRunner(), $ret);
 
         $ref = new ReflectionProperty($app, 'handler');
         if (PHP_VERSION_ID < 80100) {
@@ -893,7 +893,7 @@ public function testConstructWithRouteHandlerClassNameFollowedByMiddlewareThrows
         new App(RouteHandler::class, $middleware);
     }
 
-    public function testConstructWithContainerWithListenAddressWillPassListenAddressToReactiveHandler(): void
+    public function testConstructWithContainerWithListenAddressWillPassListenAddressToHttpServerRunner(): void
     {
         $container = new Container([
             'X_LISTEN' => '0.0.0.0:8081'
@@ -901,31 +901,31 @@ public function testConstructWithContainerWithListenAddressWillPassListenAddress
 
         $app = new App($container);
 
-        // $sapi = $app->sapi;
-        $ref = new \ReflectionProperty($app, 'sapi');
+        // $runner = $app->runner;
+        $ref = new \ReflectionProperty($app, 'runner');
         if (PHP_VERSION_ID < 80100) {
             $ref->setAccessible(true);
         }
-        $sapi = $ref->getValue($app);
-        assert($sapi instanceof ReactiveHandler);
+        $runner = $ref->getValue($app);
+        assert($runner instanceof HttpServerRunner);
 
-        // $listenAddress = $sapi->listenAddress;
-        $ref = new \ReflectionProperty($sapi, 'listenAddress');
+        // $listenAddress = $runner->listenAddress;
+        $ref = new \ReflectionProperty($runner, 'listenAddress');
         if (PHP_VERSION_ID < 80100) {
             $ref->setAccessible(true);
         }
-        $listenAddress = $ref->getValue($sapi);
+        $listenAddress = $ref->getValue($runner);
 
         $this->assertEquals('0.0.0.0:8081', $listenAddress);
     }
 
-    public function testRunWillExecuteRunOnSapiHandlerFromContainer(): void
+    public function testRunWillInvokeRunnerFromContainer(): void
     {
-        $sapi = $this->createMock(ReactiveHandler::class);
-        $sapi->expects($this->once())->method('run');
+        $runner = $this->createMock(HttpServerRunner::class);
+        $runner->expects($this->once())->method('__invoke');
 
         $container = new Container([
-            ReactiveHandler::class => $sapi
+            HttpServerRunner::class => $runner
         ]);
 
         $app = new App($container);
diff --git a/tests/ContainerTest.php b/tests/ContainerTest.php
index f4b01a4..da0374c 100644
--- a/tests/ContainerTest.php
+++ b/tests/ContainerTest.php
@@ -6,8 +6,8 @@
 use FrameworkX\Container;
 use FrameworkX\ErrorHandler;
 use FrameworkX\Io\LogStreamHandler;
-use FrameworkX\Io\ReactiveHandler;
 use FrameworkX\Io\RouteHandler;
+use FrameworkX\Runner\HttpServerRunner;
 use PHPUnit\Framework\TestCase;
 use Psr\Container\ContainerInterface;
 use Psr\Container\NotFoundExceptionInterface;
@@ -2825,85 +2825,85 @@ public function testGetObjectThrowsIfPsrContainerReturnsWrongType(): void
         $container->getObject(AccessLogHandler::class);
     }
 
-    public function testGetSapiReturnsDefaultReactiveHandlerInstance(): void
+    public function testGetRunnerReturnsDefaultHttpServerRunnerInstance(): void
     {
         $container = new Container([]);
 
-        $sapi = $container->getSapi();
+        $runner = $container->getRunner();
 
-        $this->assertInstanceOf(ReactiveHandler::class, $sapi);
+        $this->assertInstanceOf(HttpServerRunner::class, $runner);
 
-        $ref = new \ReflectionProperty($sapi, 'listenAddress');
+        $ref = new \ReflectionProperty($runner, 'listenAddress');
         if (PHP_VERSION_ID < 80100) {
             $ref->setAccessible(true);
         }
-        $listenAddress = $ref->getValue($sapi);
+        $listenAddress = $ref->getValue($runner);
 
         $this->assertEquals('127.0.0.1:8080', $listenAddress);
     }
 
-    public function testGetSapiReturnsDefaultReactiveHandlerInstanceWithCustomListenAddress(): void
+    public function testGetRunnerReturnsDefaultHttpServerRunnerInstanceWithCustomListenAddress(): void
     {
         $container = new Container([
             'X_LISTEN' => '127.0.0.1:8081'
         ]);
 
-        $sapi = $container->getSapi();
+        $runner = $container->getRunner();
 
-        $this->assertInstanceOf(ReactiveHandler::class, $sapi);
+        $this->assertInstanceOf(HttpServerRunner::class, $runner);
 
-        $ref = new \ReflectionProperty($sapi, 'listenAddress');
+        $ref = new \ReflectionProperty($runner, 'listenAddress');
         if (PHP_VERSION_ID < 80100) {
             $ref->setAccessible(true);
         }
-        $listenAddress = $ref->getValue($sapi);
+        $listenAddress = $ref->getValue($runner);
 
         $this->assertEquals('127.0.0.1:8081', $listenAddress);
     }
 
-    public function testGetSapiTwiceReturnsSameReactiveHandlerInstance(): void
+    public function testGetRunnerTwiceReturnsSameHttpServerRunnerInstance(): void
     {
         $container = new Container([]);
 
-        $sapi = $container->getSapi();
+        $runner = $container->getRunner();
 
-        $this->assertSame($sapi, $container->getSapi());
+        $this->assertSame($runner, $container->getRunner());
     }
 
-    public function testGetSapiReturnsReactiveHandlerInstanceFromConfig(): void
+    public function testGetRunnerReturnsHttpServerRunnerInstanceFromConfig(): void
     {
-        $sapi = new ReactiveHandler(new LogStreamHandler('php://output'), null);
+        $runner = new HttpServerRunner(new LogStreamHandler('php://output'), null);
 
         $container = new Container([
-            ReactiveHandler::class => $sapi
+            HttpServerRunner::class => $runner
         ]);
 
-        $ret = $container->getSapi();
+        $ret = $container->getRunner();
 
-        $this->assertSame($sapi, $ret);
+        $this->assertSame($runner, $ret);
     }
 
-    public function testGetSapiReturnsReactiveHandlerInstanceFromPsrContainer(): void
+    public function testGetRunnerReturnsHttpServerRunnerInstanceFromPsrContainer(): void
     {
-        $sapi = new ReactiveHandler(new LogStreamHandler('php://output'), null);
+        $runner = new HttpServerRunner(new LogStreamHandler('php://output'), null);
 
         $psr = $this->createMock(ContainerInterface::class);
-        $psr->expects($this->once())->method('has')->with(ReactiveHandler::class)->willReturn(true);
-        $psr->expects($this->once())->method('get')->with(ReactiveHandler::class)->willReturn($sapi);
+        $psr->expects($this->once())->method('has')->with(HttpServerRunner::class)->willReturn(true);
+        $psr->expects($this->once())->method('get')->with(HttpServerRunner::class)->willReturn($runner);
 
         assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
-        $ret = $container->getSapi();
+        $ret = $container->getRunner();
 
-        $this->assertSame($sapi, $ret);
+        $this->assertSame($runner, $ret);
     }
 
-    public function testGetSapiReturnsDefaultReactiveHandlerInstanceWithDefaultListenAddressIfPsrContainerHasNoEntry(): void
+    public function testGetRunnerReturnsDefaultHttpServerRunnerInstanceWithDefaultListenAddressIfPsrContainerHasNoEntry(): void
     {
         $psr = $this->createMock(ContainerInterface::class);
         $psr->expects($this->exactly(2))->method('has')->willReturnMap([
-            [ReactiveHandler::class, false],
+            [HttpServerRunner::class, false],
             ['X_LISTEN', false],
         ]);
         $psr->expects($this->never())->method('get');
@@ -2911,24 +2911,24 @@ public function testGetSapiReturnsDefaultReactiveHandlerInstanceWithDefaultListe
         assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
-        $sapi = $container->getSapi();
+        $runner = $container->getRunner();
 
-        $this->assertInstanceOf(ReactiveHandler::class, $sapi);
+        $this->assertInstanceOf(HttpServerRunner::class, $runner);
 
-        $ref = new \ReflectionProperty($sapi, 'listenAddress');
+        $ref = new \ReflectionProperty($runner, 'listenAddress');
         if (PHP_VERSION_ID < 80100) {
             $ref->setAccessible(true);
         }
-        $listenAddress = $ref->getValue($sapi);
+        $listenAddress = $ref->getValue($runner);
 
         $this->assertEquals('127.0.0.1:8080', $listenAddress);
     }
 
-    public function testGetSapiReturnsDefaultReactiveHandlerInstanceWithCustomListenAddressIfPsrContainerHasNoEntryButCustomListenAddress(): void
+    public function testGetRunnerReturnsDefaultHttpServerRunnerInstanceWithCustomListenAddressIfPsrContainerHasNoEntryButCustomListenAddress(): void
     {
         $psr = $this->createMock(ContainerInterface::class);
         $psr->expects($this->exactly(2))->method('has')->willReturnMap([
-            [ReactiveHandler::class, false],
+            [HttpServerRunner::class, false],
             ['X_LISTEN', true],
         ]);
         $psr->expects($this->once())->method('get')->with('X_LISTEN')->willReturn('127.0.0.1:8081');
@@ -2936,15 +2936,15 @@ public function testGetSapiReturnsDefaultReactiveHandlerInstanceWithCustomListen
         assert($psr instanceof ContainerInterface);
         $container = new Container($psr);
 
-        $sapi = $container->getSapi();
+        $runner = $container->getRunner();
 
-        $this->assertInstanceOf(ReactiveHandler::class, $sapi);
+        $this->assertInstanceOf(HttpServerRunner::class, $runner);
 
-        $ref = new \ReflectionProperty($sapi, 'listenAddress');
+        $ref = new \ReflectionProperty($runner, 'listenAddress');
         if (PHP_VERSION_ID < 80100) {
             $ref->setAccessible(true);
         }
-        $listenAddress = $ref->getValue($sapi);
+        $listenAddress = $ref->getValue($runner);
 
         $this->assertEquals('127.0.0.1:8081', $listenAddress);
     }
diff --git a/tests/Io/ReactiveHandlerTest.php b/tests/Runner/HttpServerRunnerTest.php
similarity index 78%
rename from tests/Io/ReactiveHandlerTest.php
rename to tests/Runner/HttpServerRunnerTest.php
index b63da1e..65a82ca 100644
--- a/tests/Io/ReactiveHandlerTest.php
+++ b/tests/Runner/HttpServerRunnerTest.php
@@ -1,9 +1,9 @@
 <?php
 
-namespace FrameworkX\Tests\Io;
+namespace FrameworkX\Tests\Runner;
 
 use FrameworkX\Io\LogStreamHandler;
-use FrameworkX\Io\ReactiveHandler;
+use FrameworkX\Runner\HttpServerRunner;
 use PHPUnit\Framework\TestCase;
 use React\EventLoop\Loop;
 use React\Http\Message\Response;
@@ -12,9 +12,9 @@
 use React\Socket\Connector;
 use function React\Async\await;
 
-class ReactiveHandlerTest extends TestCase
+class HttpServerRunnerTest extends TestCase
 {
-    public function testRunWillReportDefaultListeningAddressAndRunLoop(): void
+    public function testInvokeWillReportDefaultListeningAddressAndRunLoop(): void
     {
         $socket = @stream_socket_server('127.0.0.1:8080');
         if ($socket === false) {
@@ -27,7 +27,7 @@ public function testRunWillReportDefaultListeningAddressAndRunLoop(): void
         $logger->expects($this->atLeastOnce())->method('log')->withConsecutive(['Listening on http://127.0.0.1:8080']);
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, null);
+        $runner = new HttpServerRunner($logger, null);
 
         // lovely: remove socket server on next tick to terminate loop
         Loop::futureTick(function () {
@@ -41,10 +41,12 @@ public function testRunWillReportDefaultListeningAddressAndRunLoop(): void
             Loop::stop();
         });
 
-        $handler->run(function (): void { });
+        $runner(function (): void {
+            throw new \BadFunctionCallException('Should not be reached');
+        });
     }
 
-    public function testRunWillReportGivenListeningAddressAndRunLoop(): void
+    public function testInvokeWillReportGivenListeningAddressAndRunLoop(): void
     {
         $socket = stream_socket_server('127.0.0.1:0');
         assert(is_resource($socket));
@@ -56,7 +58,7 @@ public function testRunWillReportGivenListeningAddressAndRunLoop(): void
         $logger->expects($this->atLeastOnce())->method('log')->withConsecutive(['Listening on http://' . $addr]);
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, $addr);
+        $runner = new HttpServerRunner($logger, $addr);
 
         // lovely: remove socket server on next tick to terminate loop
         Loop::futureTick(function () {
@@ -70,16 +72,18 @@ public function testRunWillReportGivenListeningAddressAndRunLoop(): void
             Loop::stop();
         });
 
-        $handler->run(function (): void { });
+        $runner(function (): void {
+            throw new \BadFunctionCallException('Should not be reached');
+        });
     }
 
-    public function testRunWillReportGivenListeningAddressWithRandomPortAndRunLoop(): void
+    public function testInvokeWillReportGivenListeningAddressWithRandomPortAndRunLoop(): void
     {
         $logger = $this->createMock(LogStreamHandler::class);
         $logger->expects($this->atLeastOnce())->method('log')->withConsecutive([$this->matches('Listening on http://127.0.0.1:%d')]);
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, '127.0.0.1:0');
+        $runner = new HttpServerRunner($logger, '127.0.0.1:0');
 
         // lovely: remove socket server on next tick to terminate loop
         Loop::futureTick(function () {
@@ -93,15 +97,17 @@ public function testRunWillReportGivenListeningAddressWithRandomPortAndRunLoop()
             Loop::stop();
         });
 
-        $handler->run(function (): void { });
+        $runner(function (): void {
+            throw new \BadFunctionCallException('Should not be reached');
+        });
     }
 
-    public function testRunWillRestartLoopUntilSocketIsClosed(): void
+    public function testInvokeWillRestartLoopUntilSocketIsClosed(): void
     {
         $logger = $this->createMock(LogStreamHandler::class);
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, '127.0.0.1:0');
+        $runner = new HttpServerRunner($logger, '127.0.0.1:0');
 
         // lovely: remove socket server on next tick to terminate loop
         Loop::futureTick(function () use ($logger) {
@@ -120,10 +126,12 @@ public function testRunWillRestartLoopUntilSocketIsClosed(): void
             Loop::stop();
         });
 
-        $handler->run(function (): void { });
+        $runner(function (): void {
+            throw new \BadFunctionCallException('Should not be reached');
+        });
     }
 
-    public function testRunWillListenForHttpRequestAndSendBackHttpResponseOverSocket(): void
+    public function testInvokeWillListenForHttpRequestAndSendBackHttpResponseOverSocket(): void
     {
         $socket = stream_socket_server('127.0.0.1:0');
         assert(is_resource($socket));
@@ -134,7 +142,7 @@ public function testRunWillListenForHttpRequestAndSendBackHttpResponseOverSocket
         $logger = $this->createMock(LogStreamHandler::class);
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, $addr);
+        $runner = new HttpServerRunner($logger, $addr);
 
         Loop::futureTick(function () use ($addr): void {
             $connector = new Connector();
@@ -163,12 +171,12 @@ public function testRunWillListenForHttpRequestAndSendBackHttpResponseOverSocket
             });
         });
 
-        $handler->run(function (): Response {
+        $runner(function (): Response {
             return new Response(200, ['Date' => '', 'Server' => ''], "OK\n");
         });
     }
 
-    public function testRunWillOnlyRestartLoopAfterAwaitingWhenFibersAreNotAvailable(): void
+    public function testInvokeWillOnlyRestartLoopAfterAwaitingWhenFibersAreNotAvailable(): void
     {
         $socket = stream_socket_server('127.0.0.1:0');
         assert(is_resource($socket));
@@ -179,7 +187,7 @@ public function testRunWillOnlyRestartLoopAfterAwaitingWhenFibersAreNotAvailable
         $logger = $this->createMock(LogStreamHandler::class);
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, $addr);
+        $runner = new HttpServerRunner($logger, $addr);
 
         Loop::futureTick(function () use ($addr, $logger): void {
             $connector = new Connector();
@@ -216,7 +224,7 @@ public function testRunWillOnlyRestartLoopAfterAwaitingWhenFibersAreNotAvailable
         });
 
         $done = false;
-        $handler->run(function () use (&$done): Response {
+        $runner(function () use (&$done): Response {
             $promise = new Promise(function (callable $resolve) use (&$done): void {
                 Loop::futureTick(function () use ($resolve, &$done): void {
                     $resolve(null);
@@ -232,7 +240,7 @@ public function testRunWillOnlyRestartLoopAfterAwaitingWhenFibersAreNotAvailable
         $this->assertTrue($done);
     }
 
-    public function testRunWillReportHttpErrorForInvalidClientRequest(): void
+    public function testInvokeWillReportHttpErrorForInvalidClientRequest(): void
     {
         $socket = stream_socket_server('127.0.0.1:0');
         assert(is_resource($socket));
@@ -243,7 +251,7 @@ public function testRunWillReportHttpErrorForInvalidClientRequest(): void
         $logger = $this->createMock(LogStreamHandler::class);
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, $addr);
+        $runner = new HttpServerRunner($logger, $addr);
 
         Loop::futureTick(function () use ($addr, $logger): void {
             $connector = new Connector();
@@ -269,20 +277,22 @@ public function testRunWillReportHttpErrorForInvalidClientRequest(): void
             });
         });
 
-        $handler->run(function (): void { });
+        $runner(function (): void {
+            throw new \BadFunctionCallException('Should not be reached');
+        });
     }
 
     /**
      * @requires function pcntl_signal
      * @requires function posix_kill
      */
-    public function testRunWillStopWhenReceivingSigint(): void
+    public function testInvokeWillStopWhenReceivingSigint(): void
     {
         $logger = $this->createMock(LogStreamHandler::class);
         $logger->expects($this->exactly(2))->method('log');
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, '127.0.0.1:0');
+        $runner = new HttpServerRunner($logger, '127.0.0.1:0');
 
         Loop::futureTick(function () use ($logger) {
             $logger->expects($this->once())->method('log')->with('Received SIGINT, stopping loop');
@@ -293,19 +303,21 @@ public function testRunWillStopWhenReceivingSigint(): void
         });
 
         $this->expectOutputRegex("#^\r?$#");
-        $handler->run(function (): void { });
+        $runner(function (): void {
+            throw new \BadFunctionCallException('Should not be reached');
+        });
     }
 
     /**
      * @requires function pcntl_signal
      * @requires function posix_kill
      */
-    public function testRunWillStopWhenReceivingSigterm(): void
+    public function testInvokeWillStopWhenReceivingSigterm(): void
     {
         $logger = $this->createMock(LogStreamHandler::class);
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, '127.0.0.1:0');
+        $runner = new HttpServerRunner($logger, '127.0.0.1:0');
 
         Loop::futureTick(function () use ($logger) {
             $logger->expects($this->once())->method('log')->with('Received SIGTERM, stopping loop');
@@ -315,21 +327,25 @@ public function testRunWillStopWhenReceivingSigterm(): void
             posix_kill($pid, defined('SIGTERM') ? SIGTERM : 15);
         });
 
-        $handler->run(function (): void { });
+        $runner(function (): void {
+            throw new \BadFunctionCallException('Should not be reached');
+        });
     }
 
-    public function testRunWithEmptyAddressThrows(): void
+    public function testInvokeWithEmptyAddressThrows(): void
     {
         $logger = $this->createMock(LogStreamHandler::class);
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, '');
+        $runner = new HttpServerRunner($logger, '');
 
         $this->expectException(\InvalidArgumentException::class);
-        $handler->run(function (): void { });
+        $runner(function (): void {
+            throw new \BadFunctionCallException('Should not be reached');
+        });
     }
 
-    public function testRunWithBusyPortThrows(): void
+    public function testInvokeWithBusyPortThrows(): void
     {
         $socket = stream_socket_server('127.0.0.1:0');
         assert(is_resource($socket));
@@ -343,10 +359,12 @@ public function testRunWithBusyPortThrows(): void
         $logger = $this->createMock(LogStreamHandler::class);
         assert($logger instanceof LogStreamHandler);
 
-        $handler = new ReactiveHandler($logger, $addr);
+        $runner = new HttpServerRunner($logger, $addr);
 
         $this->expectException(\RuntimeException::class);
         $this->expectExceptionMessage('Failed to listen on');
-        $handler->run(function (): void { });
+        $runner(function (): void {
+            throw new \BadFunctionCallException('Should not be reached');
+        });
     }
 }
diff --git a/tests/Io/SapiHandlerTest.php b/tests/Runner/SapiRunnerTest.php
similarity index 93%
rename from tests/Io/SapiHandlerTest.php
rename to tests/Runner/SapiRunnerTest.php
index 8afd89e..a70048b 100644
--- a/tests/Io/SapiHandlerTest.php
+++ b/tests/Runner/SapiRunnerTest.php
@@ -1,18 +1,18 @@
 <?php
 
-namespace FrameworkX\Tests\Io;
+namespace FrameworkX\Tests\Runner;
 
-use FrameworkX\Io\SapiHandler;
+use FrameworkX\Runner\SapiRunner;
 use PHPUnit\Framework\TestCase;
 use React\Http\Message\Response;
 use React\Stream\ThroughStream;
 use function React\Promise\resolve;
 
-class SapiHandlerTest extends TestCase
+class SapiRunnerTest extends TestCase
 {
     public function testRequestFromGlobalsWithNoServerVariablesDefaultsToGetRequestToLocalhost(): void
     {
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $request = $sapi->requestFromGlobals();
 
         $this->assertEquals('GET', $request->getMethod());
@@ -31,7 +31,7 @@ public function testRequestFromGlobalsWithHeadRequest(): void
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.0';
         $_SERVER['HTTP_HOST'] = 'example.com';
 
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $request = $sapi->requestFromGlobals();
 
         $this->assertEquals('HEAD', $request->getMethod());
@@ -50,7 +50,7 @@ public function testRequestFromGlobalsWithGetRequestOverCustomPort(): void
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
         $_SERVER['HTTP_HOST'] = 'localhost:8080';
 
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $request = $sapi->requestFromGlobals();
 
         $this->assertEquals('GET', $request->getMethod());
@@ -70,7 +70,7 @@ public function testRequestFromGlobalsWithGetRequestOverHttps(): void
         $_SERVER['HTTP_HOST'] = 'localhost';
         $_SERVER['HTTPS'] = 'on';
 
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $request = $sapi->requestFromGlobals();
 
         $this->assertEquals('GET', $request->getMethod());
@@ -89,7 +89,7 @@ public function testRequestFromGlobalsWithOptionsAsterisk(): void
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
         $_SERVER['HTTP_HOST'] = 'localhost';
 
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $request = $sapi->requestFromGlobals();
 
         $this->assertEquals('OPTIONS', $request->getMethod());
@@ -109,7 +109,7 @@ public function testRequestFromGlobalsWithGetProxy(): void
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
         $_SERVER['HTTP_HOST'] = 'example.com';
 
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $request = $sapi->requestFromGlobals();
 
         $this->assertEquals('GET', $request->getMethod());
@@ -129,7 +129,7 @@ public function testRequestFromGlobalsWithConnectProxy(): void
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
         $_SERVER['HTTP_HOST'] = 'example.com:443';
 
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $request = $sapi->requestFromGlobals();
 
         $this->assertEquals('CONNECT', $request->getMethod());
@@ -149,7 +149,7 @@ public function testRequestFromGlobalsWithConnectProxyWithDefaultHttpPort(): voi
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
         $_SERVER['HTTP_HOST'] = 'example.com';
 
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $request = $sapi->requestFromGlobals();
 
         $this->assertEquals('CONNECT', $request->getMethod());
@@ -168,7 +168,7 @@ public function testRequestFromGlobalsWithConnectProxyWithoutHostHeader(): void
         $_SERVER['REQUEST_URI'] = 'example.com:8080';
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
 
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $request = $sapi->requestFromGlobals();
 
         $this->assertEquals('CONNECT', $request->getMethod());
@@ -189,7 +189,7 @@ public function testRequestFromGlobalsWithConnectProxyOverHttps(): void
         $_SERVER['HTTP_HOST'] = 'example.com:443';
         $_SERVER['HTTPS'] = 'on';
 
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $request = $sapi->requestFromGlobals();
 
         $this->assertEquals('CONNECT', $request->getMethod());
@@ -206,7 +206,7 @@ public function testSendResponseSendsEmptyResponseWithNoHeadersAndEmptyBodyAndAs
     {
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $response = new Response(200, [], '');
 
         $this->expectOutputString('');
@@ -226,7 +226,7 @@ public function testSendResponseSendsJsonResponseWithGivenHeadersAndBodyAndAssig
     {
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $response = new Response(200, ['Content-Type' => 'application/json'], '{}');
 
         $this->expectOutputString('{}');
@@ -247,7 +247,7 @@ public function testSendResponseSendsJsonResponseWithGivenHeadersAndMatchingCont
         header_remove();
         $_SERVER['REQUEST_METHOD'] = 'HEAD';
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $response = new Response(200, ['Content-Type' => 'application/json'], '{}');
 
         $this->expectOutputString('');
@@ -267,7 +267,7 @@ public function testSendResponseSendsEmptyBodyWithGivenHeadersAndAssignsNoConten
     {
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $response = new Response(204, ['Content-Type' => 'application/json'], '{}');
 
         $this->expectOutputString('');
@@ -287,7 +287,7 @@ public function testSendResponseSendsEmptyBodyWithGivenHeadersButWithoutExplicit
     {
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $response = new Response(204, ['Content-Type' => 'application/json', 'Content-Length' => '2'], '{}');
 
         $this->expectOutputString('');
@@ -307,7 +307,7 @@ public function testSendResponseSendsEmptyBodyWithGivenHeadersAndAssignsContentL
     {
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $response = new Response(304, ['Content-Type' => 'application/json'], 'null');
 
         $this->expectOutputString('');
@@ -327,7 +327,7 @@ public function testSendResponseSendsEmptyBodyWithGivenHeadersAndExplicitContent
     {
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $response = new Response(304, ['Content-Type' => 'application/json', 'Content-Length' => '2'], '');
 
         $this->expectOutputString('');
@@ -347,7 +347,7 @@ public function testSendResponseSendsStreamingResponseWithNoHeadersAndBodyFromSt
     {
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $body = new ThroughStream();
         $response = new Response(200, [], $body);
 
@@ -371,7 +371,7 @@ public function testSendResponseClosesStreamingResponseAndSendsResponseWithNoHea
         header_remove();
         $_SERVER['REQUEST_METHOD'] = 'HEAD';
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $body = new ThroughStream();
         $response = new Response(200, [], $body);
 
@@ -394,7 +394,7 @@ public function testSendResponseClosesStreamingResponseAndSendsResponseWithNoHea
     {
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $body = new ThroughStream();
         $response = new Response(304, [], $body);
 
@@ -417,7 +417,7 @@ public function testSendResponseClosesStreamingResponseAndSendsResponseWithNoHea
     {
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $body = new ThroughStream();
         $response = new Response(204, [], $body);
 
@@ -441,7 +441,7 @@ public function testSendResponseSendsStreamingResponseWithNoHeadersAndBodyFromSt
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
         $_SERVER['SERVER_SOFTWARE'] = 'nginx/1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $body = new ThroughStream();
         $response = new Response(200, [], $body);
 
@@ -464,7 +464,7 @@ public function testSendResponseSetsMultipleCookieHeaders(): void
     {
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
         $response = new Response(204, ['Set-Cookie' => ['1=1', '2=2']], '');
 
         $this->expectOutputString('');
@@ -480,15 +480,15 @@ public function testSendResponseSetsMultipleCookieHeaders(): void
     /**
      * @runInSeparateProcess
      */
-    public function testRunWillSendResponseHeadersFromHandler(): void
+    public function testInvokeWillSendResponseHeadersFromHandler(): void
     {
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
 
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
 
         $this->expectOutputString('');
-        $sapi->run(function () {
+        $sapi(function () {
             return new Response();
         });
 
@@ -502,15 +502,15 @@ public function testRunWillSendResponseHeadersFromHandler(): void
     /**
      * @runInSeparateProcess
      */
-    public function testRunWillSendResponseHeadersFromDeferredHandler(): void
+    public function testInvokeWillSendResponseHeadersFromDeferredHandler(): void
     {
-        $sapi = new SapiHandler();
+        $sapi = new SapiRunner();
 
         header_remove();
         $_SERVER['SERVER_PROTOCOL'] = 'http/1.1';
 
         $this->expectOutputString('');
-        $sapi->run(function () {
+        $sapi(function () {
             return resolve(new Response());
         });