diff --git a/composer.json b/composer.json
index 3e81bc5..0553bb4 100644
--- a/composer.json
+++ b/composer.json
@@ -33,10 +33,10 @@
         }
     ],
     "require": {
-        "php": ">=8"
+        "php": ">=8",
+        "ext-fiber": "*"
     },
     "require-dev": {
-        "ext-fiber": "*",
         "ext-json": "*",
         "amphp/phpunit-util": "^1",
         "amphp/php-cs-fixer-config": "dev-master",
@@ -51,8 +51,7 @@
         },
         "files": [
             "lib/functions.php",
-            "lib/Internal/functions.php",
-            "polyfill/ext-fiber.php"
+            "lib/Internal/functions.php"
         ]
     },
     "autoload-dev": {
diff --git a/lib/Coroutine.php b/lib/Coroutine.php
index c7c9328..a199f24 100644
--- a/lib/Coroutine.php
+++ b/lib/Coroutine.php
@@ -2,9 +2,9 @@
 
 namespace Amp;
 
-use React\Promise\PromiseInterface as ReactPromise;
-
 /**
+ * @deprecated Use {@see await()} and ext-fiber to await promises.
+ *
  * Creates a promise from a generator function yielding promises.
  *
  * When a promise is yielded, execution of the generator is interrupted until the promise is resolved. A success
@@ -18,44 +18,6 @@ final class Coroutine implements Promise
 {
     use Internal\Placeholder;
 
-    /**
-     * Attempts to transform the non-promise yielded from the generator into a promise, otherwise returns an instance
-     * `Amp\Failure` failed with an instance of `Amp\InvalidYieldError`.
-     *
-     * @param mixed      $yielded Non-promise yielded from generator.
-     * @param \Generator $generator No type for performance, we already know the type.
-     *
-     * @return Promise
-     */
-    private static function transform(mixed $yielded, \Generator $generator): Promise
-    {
-        $exception = null; // initialize here, see https://github.com/vimeo/psalm/issues/2951
-
-        try {
-            if (\is_array($yielded)) {
-                return Promise\all($yielded);
-            }
-
-            if ($yielded instanceof ReactPromise) {
-                return Promise\adapt($yielded);
-            }
-
-            // No match, continue to returning Failure below.
-        } catch (\Throwable $exception) {
-            // Conversion to promise failed, fall-through to returning Failure below.
-        }
-
-        return new Failure(new InvalidYieldError(
-            $generator,
-            \sprintf(
-                "Unexpected yield; Expected an instance of %s or %s or an array of such instances",
-                Promise::class,
-                ReactPromise::class
-            ),
-            $exception
-        ));
-    }
-
     /**
      * @param \Generator $generator
      * @psalm-param \Generator<mixed,Promise|ReactPromise|array<array-key,
@@ -63,98 +25,21 @@ final class Coroutine implements Promise
      */
     public function __construct(\Generator $generator)
     {
-        try {
+        $this->resolve(async(function () use ($generator): mixed {
             $yielded = $generator->current();
 
-            if (!$yielded instanceof Promise) {
-                if (!$generator->valid()) {
-                    $this->resolve($generator->getReturn());
-                    return;
-                }
-
-                $yielded = self::transform($yielded, $generator);
-            }
-        } catch (\Throwable $exception) {
-            $this->fail($exception);
-            return;
-        }
-
-        /**
-         * @param \Throwable|null $e Exception to be thrown into the generator.
-         * @param mixed           $v Value to be sent into the generator.
-         *
-         * @return void
-         *
-         * @psalm-suppress MissingClosureParamType
-         * @psalm-suppress MissingClosureReturnType
-         */
-        $onResolve = function (?\Throwable $e, mixed $v) use ($generator, &$onResolve): void {
-            /** @var bool $immediate Used to control iterative coroutine continuation. */
-            static $immediate = true;
-
-            /** @var \Throwable|null $exception Promise failure reason when executing next coroutine step, null at all other times. */
-            static $exception;
-
-            /** @var mixed $value Promise success value when executing next coroutine step, null at all other times. */
-            static $value;
-
-            $exception = $e;
-            /** @psalm-suppress MixedAssignment */
-            $value = $v;
-
-            if (!$immediate) {
-                $immediate = true;
-                return;
-            }
-
-            try {
+            while ($generator->valid()) {
                 try {
-                    do {
-                        if ($exception) {
-                            // Throw exception at current execution point.
-                            $yielded = $generator->throw($exception);
-                        } else {
-                            // Send the new value and execute to next yield statement.
-                            $yielded = $generator->send($value);
-                        }
-
-                        if (!$yielded instanceof Promise) {
-                            if (!$generator->valid()) {
-                                $this->resolve($generator->getReturn());
-                                $onResolve = null;
-                                return;
-                            }
-
-                            $yielded = self::transform($yielded, $generator);
-                        }
-
-                        $immediate = false;
-                        $yielded->onResolve($onResolve);
-                    } while ($immediate);
-
-                    $immediate = true;
+                    $value = await($yielded);
                 } catch (\Throwable $exception) {
-                    $this->fail($exception);
-                    $onResolve = null;
-                } finally {
-                    $exception = null;
-                    $value = null;
+                    $yielded = $generator->throw($exception);
+                    continue;
                 }
-            } catch (\Throwable $e) {
-                Loop::defer(static function () use ($e) {
-                    throw $e;
-                });
+
+                $yielded = $generator->send($value);
             }
-        };
 
-        try {
-            $yielded->onResolve($onResolve);
-
-            unset($generator, $yielded, $onResolve);
-        } catch (\Throwable $e) {
-            Loop::defer(static function () use ($e) {
-                throw $e;
-            });
-        }
+            return $generator->getReturn();
+        }));
     }
 }
diff --git a/polyfill/ext-fiber.php b/polyfill/ext-fiber.php
deleted file mode 100644
index d2432c2..0000000
--- a/polyfill/ext-fiber.php
+++ /dev/null
@@ -1,6 +0,0 @@
-<?php
-
-if (!\extension_loaded('fiber')) {
-    require __DIR__ . '/../stubs/Awaitable.php';
-    require __DIR__ . '/../stubs/FiberScheduler.php';
-}