diff --git a/src/platform/src/Bridge/Anthropic/ResultConverter.php b/src/platform/src/Bridge/Anthropic/ResultConverter.php
index 6916aa256..6d633df48 100644
--- a/src/platform/src/Bridge/Anthropic/ResultConverter.php
+++ b/src/platform/src/Bridge/Anthropic/ResultConverter.php
@@ -11,7 +11,7 @@
 
 namespace Symfony\AI\Platform\Bridge\Anthropic;
 
-use Symfony\AI\Platform\Exception\RateLimitExceededException;
+use Symfony\AI\Platform\Exception\HttpErrorHandler;
 use Symfony\AI\Platform\Exception\RuntimeException;
 use Symfony\AI\Platform\Model;
 use Symfony\AI\Platform\Result\RawHttpResult;
@@ -41,11 +41,7 @@ public function convert(RawHttpResult|RawResultInterface $result, array $options
     {
         $response = $result->getObject();
 
-        if (429 === $response->getStatusCode()) {
-            $retryAfter = $response->getHeaders(false)['retry-after'][0] ?? null;
-            $retryAfterValue = $retryAfter ? (float) $retryAfter : null;
-            throw new RateLimitExceededException($retryAfterValue);
-        }
+        HttpErrorHandler::handleHttpError($response);
 
         if ($options['stream'] ?? false) {
             return new StreamResult($this->convertStream($response));
diff --git a/src/platform/src/Bridge/Cerebras/ResultConverter.php b/src/platform/src/Bridge/Cerebras/ResultConverter.php
index b11f7576b..f9e4c40cd 100644
--- a/src/platform/src/Bridge/Cerebras/ResultConverter.php
+++ b/src/platform/src/Bridge/Cerebras/ResultConverter.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\AI\Platform\Bridge\Cerebras;
 
+use Symfony\AI\Platform\Exception\HttpErrorHandler;
 use Symfony\AI\Platform\Exception\RuntimeException;
 use Symfony\AI\Platform\Model as BaseModel;
 use Symfony\AI\Platform\Result\RawHttpResult;
@@ -36,8 +37,11 @@ public function supports(BaseModel $model): bool
 
     public function convert(RawHttpResult|RawResultInterface $result, array $options = []): ResultInterface
     {
+        $response = $result->getObject();
+        HttpErrorHandler::handleHttpError($response);
+
         if ($options['stream'] ?? false) {
-            return new StreamResult($this->convertStream($result->getObject()));
+            return new StreamResult($this->convertStream($response));
         }
 
         $data = $result->getData();
diff --git a/src/platform/src/Bridge/Gemini/Gemini/ResultConverter.php b/src/platform/src/Bridge/Gemini/Gemini/ResultConverter.php
index 9e7cafe1d..77fa85187 100644
--- a/src/platform/src/Bridge/Gemini/Gemini/ResultConverter.php
+++ b/src/platform/src/Bridge/Gemini/Gemini/ResultConverter.php
@@ -12,7 +12,7 @@
 namespace Symfony\AI\Platform\Bridge\Gemini\Gemini;
 
 use Symfony\AI\Platform\Bridge\Gemini\Gemini;
-use Symfony\AI\Platform\Exception\RateLimitExceededException;
+use Symfony\AI\Platform\Exception\HttpErrorHandler;
 use Symfony\AI\Platform\Exception\RuntimeException;
 use Symfony\AI\Platform\Model;
 use Symfony\AI\Platform\Result\ChoiceResult;
@@ -45,9 +45,7 @@ public function convert(RawResultInterface|RawHttpResult $result, array $options
     {
         $response = $result->getObject();
 
-        if (429 === $response->getStatusCode()) {
-            throw new RateLimitExceededException();
-        }
+        HttpErrorHandler::handleHttpError($response);
 
         if ($options['stream'] ?? false) {
             return new StreamResult($this->convertStream($response));
diff --git a/src/platform/src/Bridge/OpenAi/Gpt/ResultConverter.php b/src/platform/src/Bridge/OpenAi/Gpt/ResultConverter.php
index 43592cb27..86461204b 100644
--- a/src/platform/src/Bridge/OpenAi/Gpt/ResultConverter.php
+++ b/src/platform/src/Bridge/OpenAi/Gpt/ResultConverter.php
@@ -12,9 +12,8 @@
 namespace Symfony\AI\Platform\Bridge\OpenAi\Gpt;
 
 use Symfony\AI\Platform\Bridge\OpenAi\Gpt;
-use Symfony\AI\Platform\Exception\AuthenticationException;
 use Symfony\AI\Platform\Exception\ContentFilterException;
-use Symfony\AI\Platform\Exception\RateLimitExceededException;
+use Symfony\AI\Platform\Exception\HttpErrorHandler;
 use Symfony\AI\Platform\Exception\RuntimeException;
 use Symfony\AI\Platform\Model;
 use Symfony\AI\Platform\Result\ChoiceResult;
@@ -46,23 +45,7 @@ public function convert(RawResultInterface|RawHttpResult $result, array $options
     {
         $response = $result->getObject();
 
-        if (401 === $response->getStatusCode()) {
-            $errorMessage = json_decode($response->getContent(false), true)['error']['message'];
-            throw new AuthenticationException($errorMessage);
-        }
-
-        if (429 === $response->getStatusCode()) {
-            $headers = $response->getHeaders(false);
-            $resetTime = null;
-
-            if (isset($headers['x-ratelimit-reset-requests'][0])) {
-                $resetTime = self::parseResetTime($headers['x-ratelimit-reset-requests'][0]);
-            } elseif (isset($headers['x-ratelimit-reset-tokens'][0])) {
-                $resetTime = self::parseResetTime($headers['x-ratelimit-reset-tokens'][0]);
-            }
-
-            throw new RateLimitExceededException($resetTime);
-        }
+        HttpErrorHandler::handleHttpError($response);
 
         if ($options['stream'] ?? false) {
             return new StreamResult($this->convertStream($response));
@@ -208,25 +191,4 @@ private function convertToolCall(array $toolCall): ToolCall
 
         return new ToolCall($toolCall['id'], $toolCall['function']['name'], $arguments);
     }
-
-    /**
-     * Converts OpenAI's reset time format (e.g. "1s", "6m0s", "2m30s") into seconds.
-     *
-     * Supported formats:
-     * - "1s"
-     * - "6m0s"
-     * - "2m30s"
-     */
-    private static function parseResetTime(string $resetTime): float
-    {
-        $seconds = 0;
-
-        if (preg_match('/^(?:(\d+)m)?(?:(\d+)s)?$/', $resetTime, $matches)) {
-            $minutes = isset($matches[1]) ? (int) $matches[1] : 0;
-            $secs = isset($matches[2]) ? (int) $matches[2] : 0;
-            $seconds = ($minutes * 60) + $secs;
-        }
-
-        return (float) $seconds;
-    }
 }
diff --git a/src/platform/src/Bridge/Perplexity/ResultConverter.php b/src/platform/src/Bridge/Perplexity/ResultConverter.php
index 0a5cc7695..020fecb46 100644
--- a/src/platform/src/Bridge/Perplexity/ResultConverter.php
+++ b/src/platform/src/Bridge/Perplexity/ResultConverter.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\AI\Platform\Bridge\Perplexity;
 
+use Symfony\AI\Platform\Exception\HttpErrorHandler;
 use Symfony\AI\Platform\Exception\RuntimeException;
 use Symfony\AI\Platform\Metadata\Metadata;
 use Symfony\AI\Platform\Model;
@@ -38,8 +39,11 @@ public function supports(Model $model): bool
 
     public function convert(RawResultInterface|RawHttpResult $result, array $options = []): ResultInterface
     {
+        $response = $result->getObject();
+        HttpErrorHandler::handleHttpError($response);
+
         if ($options['stream'] ?? false) {
-            return new StreamResult($this->convertStream($result->getObject()));
+            return new StreamResult($this->convertStream($response));
         }
 
         $data = $result->getData();
diff --git a/src/platform/src/Exception/HttpErrorHandler.php b/src/platform/src/Exception/HttpErrorHandler.php
new file mode 100644
index 000000000..0c5f0849b
--- /dev/null
+++ b/src/platform/src/Exception/HttpErrorHandler.php
@@ -0,0 +1,107 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\AI\Platform\Exception;
+
+use Symfony\Contracts\HttpClient\ResponseInterface;
+
+/**
+ * @author Junaid Farooq <ulislam.junaid125@gmail.com>
+ */
+final class HttpErrorHandler
+{
+    public static function handleHttpError(ResponseInterface $response): void
+    {
+        $statusCode = $response->getStatusCode();
+
+        if ($statusCode >= 200 && $statusCode < 300) {
+            return;
+        }
+
+        $errorMessage = self::extractErrorMessage($response);
+
+        match ($statusCode) {
+            401 => throw new AuthenticationException($errorMessage),
+            404 => throw new NotFoundException($errorMessage),
+            429 => throw new RateLimitExceededException(self::extractRetryAfter($response)),
+            503 => throw new ServiceUnavailableException($errorMessage),
+            default => throw new RuntimeException(\sprintf('HTTP %d: %s', $statusCode, $errorMessage)),
+        };
+    }
+
+    private static function extractErrorMessage(ResponseInterface $response): string
+    {
+        $content = $response->getContent(false);
+
+        if ('' === $content) {
+            return \sprintf('HTTP %d error', $response->getStatusCode());
+        }
+
+        $data = json_decode($content, true);
+
+        if (!\is_array($data)) {
+            return $content;
+        }
+
+        if (isset($data['error']['message'])) {
+            return $data['error']['message'];
+        }
+
+        if (isset($data['error']) && \is_string($data['error'])) {
+            return $data['error'];
+        }
+
+        return $data['message'] ?? $data['detail'] ?? $content;
+    }
+
+    private static function extractRetryAfter(ResponseInterface $response): ?float
+    {
+        $headers = $response->getHeaders(false);
+
+        if (isset($headers['retry-after'][0])) {
+            return (float) $headers['retry-after'][0];
+        }
+
+        if (isset($headers['x-ratelimit-reset-requests'][0])) {
+            return self::parseResetTime($headers['x-ratelimit-reset-requests'][0]);
+        }
+
+        if (isset($headers['x-ratelimit-reset-tokens'][0])) {
+            return self::parseResetTime($headers['x-ratelimit-reset-tokens'][0]);
+        }
+
+        return null;
+    }
+
+    private static function parseResetTime(string $resetTime): ?float
+    {
+        if (is_numeric($resetTime)) {
+            return (float) $resetTime;
+        }
+
+        if (preg_match('/^(?:(\d+)h)?(?:(\d+)m)?(?:(\d+)s)?$/', $resetTime, $matches)) {
+            $hours = (int) ($matches[1] ?? 0);
+            $minutes = (int) ($matches[2] ?? 0);
+            $seconds = (int) ($matches[3] ?? 0);
+
+            return (float) ($hours * 3600 + $minutes * 60 + $seconds);
+        }
+
+        $timestamp = strtotime($resetTime);
+        if (false === $timestamp) {
+            return null;
+        }
+
+        $diff = $timestamp - time();
+
+        return $diff > 0 ? (float) $diff : null;
+    }
+}
diff --git a/src/platform/src/Exception/NotFoundException.php b/src/platform/src/Exception/NotFoundException.php
new file mode 100644
index 000000000..7143681d3
--- /dev/null
+++ b/src/platform/src/Exception/NotFoundException.php
@@ -0,0 +1,19 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\AI\Platform\Exception;
+
+/**
+ * @author Junaid Farooq <ulislam.junaid125@gmail.com>
+ */
+class NotFoundException extends InvalidArgumentException
+{
+}
diff --git a/src/platform/src/Exception/ServiceUnavailableException.php b/src/platform/src/Exception/ServiceUnavailableException.php
new file mode 100644
index 000000000..adb37ab41
--- /dev/null
+++ b/src/platform/src/Exception/ServiceUnavailableException.php
@@ -0,0 +1,19 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\AI\Platform\Exception;
+
+/**
+ * @author Junaid Farooq <ulislam.junaid125@gmail.com>
+ */
+class ServiceUnavailableException extends RuntimeException
+{
+}
diff --git a/src/platform/tests/Bridge/Cerebras/ResultConverterTest.php b/src/platform/tests/Bridge/Cerebras/ResultConverterTest.php
index a7185a137..7bb9852aa 100644
--- a/src/platform/tests/Bridge/Cerebras/ResultConverterTest.php
+++ b/src/platform/tests/Bridge/Cerebras/ResultConverterTest.php
@@ -16,22 +16,143 @@
 use PHPUnit\Framework\Attributes\UsesClass;
 use PHPUnit\Framework\TestCase;
 use Symfony\AI\Platform\Bridge\Cerebras\Model;
-use Symfony\AI\Platform\Bridge\Cerebras\ModelClient;
 use Symfony\AI\Platform\Bridge\Cerebras\ResultConverter;
-use Symfony\Component\HttpClient\MockHttpClient;
+use Symfony\AI\Platform\Exception\AuthenticationException;
+use Symfony\AI\Platform\Exception\NotFoundException;
+use Symfony\AI\Platform\Exception\RuntimeException;
+use Symfony\AI\Platform\Exception\ServiceUnavailableException;
+use Symfony\AI\Platform\Result\RawHttpResult;
+use Symfony\AI\Platform\Result\TextResult;
+use Symfony\Contracts\HttpClient\ResponseInterface;
 
 /**
  * @author Junaid Farooq <ulislam.junaid125@gmail.com>
  */
 #[CoversClass(ResultConverter::class)]
 #[UsesClass(Model::class)]
+#[UsesClass(TextResult::class)]
 #[Small]
 class ResultConverterTest extends TestCase
 {
-    public function testItSupportsTheCorrectModel()
+    public function testSupportsCorrectModel()
     {
-        $client = new ModelClient(new MockHttpClient(), 'csk-1234567890abcdef');
+        $converter = new ResultConverter();
+        $model = new Model(Model::GPT_OSS_120B);
 
-        $this->assertTrue($client->supports(new Model(Model::GPT_OSS_120B)));
+        $this->assertTrue($converter->supports($model));
+    }
+
+    public function testConvertSuccessfulTextResult()
+    {
+        $converter = new ResultConverter();
+        $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
+        $httpResponse->method('toArray')->willReturn([
+            'choices' => [
+                [
+                    'message' => [
+                        'content' => 'Hello from Cerebras!',
+                    ],
+                ],
+            ],
+        ]);
+
+        $result = $converter->convert(new RawHttpResult($httpResponse));
+
+        $this->assertInstanceOf(TextResult::class, $result);
+        $this->assertSame('Hello from Cerebras!', $result->getContent());
+    }
+
+    public function testThrowsAuthenticationException()
+    {
+        $converter = new ResultConverter();
+        $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(401);
+        $httpResponse->method('getContent')
+            ->with(false)
+            ->willReturn('{"error": {"message": "Invalid API key"}}');
+
+        $this->expectException(AuthenticationException::class);
+        $this->expectExceptionMessage('Invalid API key');
+
+        $converter->convert(new RawHttpResult($httpResponse));
+    }
+
+    public function testThrowsNotFoundException()
+    {
+        $converter = new ResultConverter();
+        $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(404);
+        $httpResponse->method('getContent')
+            ->with(false)
+            ->willReturn('{"error": {"message": "Model not found"}}');
+
+        $this->expectException(NotFoundException::class);
+        $this->expectExceptionMessage('Model not found');
+
+        $converter->convert(new RawHttpResult($httpResponse));
+    }
+
+    public function testThrowsServiceUnavailableException()
+    {
+        $converter = new ResultConverter();
+        $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(503);
+        $httpResponse->method('getContent')
+            ->with(false)
+            ->willReturn('{"error": {"message": "Service temporarily unavailable"}}');
+
+        $this->expectException(ServiceUnavailableException::class);
+        $this->expectExceptionMessage('Service temporarily unavailable');
+
+        $converter->convert(new RawHttpResult($httpResponse));
+    }
+
+    public function testThrowsRuntimeExceptionWhenNoContent()
+    {
+        $converter = new ResultConverter();
+        $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
+        $httpResponse->method('toArray')->willReturn([
+            'choices' => [
+                [
+                    'message' => [],
+                ],
+            ],
+        ]);
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Response does not contain output.');
+
+        $converter->convert(new RawHttpResult($httpResponse));
+    }
+
+    public function testThrowsCerebrasApiError()
+    {
+        $converter = new ResultConverter();
+        $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
+        $httpResponse->method('toArray')->willReturn([
+            'type' => 'api_error',
+            'message' => 'Something went wrong with the API',
+        ]);
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Cerebras API error: "Something went wrong with the API"');
+
+        $converter->convert(new RawHttpResult($httpResponse));
+    }
+
+    public function testThrowsGenericRuntimeExceptionForMissingChoices()
+    {
+        $converter = new ResultConverter();
+        $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
+        $httpResponse->method('toArray')->willReturn([]);
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('Response does not contain output.');
+
+        $converter->convert(new RawHttpResult($httpResponse));
     }
 }
diff --git a/src/platform/tests/Bridge/Gemini/CodeExecution/ResultConverterTest.php b/src/platform/tests/Bridge/Gemini/CodeExecution/ResultConverterTest.php
index 3bfd10efd..be0d84af8 100644
--- a/src/platform/tests/Bridge/Gemini/CodeExecution/ResultConverterTest.php
+++ b/src/platform/tests/Bridge/Gemini/CodeExecution/ResultConverterTest.php
@@ -28,9 +28,12 @@ final class ResultConverterTest extends TestCase
 {
     public function testItReturnsAggregatedTextOnSuccess()
     {
-        $response = $this->createStub(ResponseInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
         $responseContent = file_get_contents(\dirname(__DIR__, 6).'/fixtures/Bridge/Gemini/code_execution_outcome_ok.json');
 
+        $response
+            ->method('getStatusCode')
+            ->willReturn(200);
         $response
             ->method('toArray')
             ->willReturn(json_decode($responseContent, true));
@@ -45,9 +48,12 @@ public function testItReturnsAggregatedTextOnSuccess()
 
     public function testItThrowsExceptionOnFailure()
     {
-        $response = $this->createStub(ResponseInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
         $responseContent = file_get_contents(\dirname(__DIR__, 6).'/fixtures/Bridge/Gemini/code_execution_outcome_failed.json');
 
+        $response
+            ->method('getStatusCode')
+            ->willReturn(200);
         $response
             ->method('toArray')
             ->willReturn(json_decode($responseContent, true));
@@ -60,9 +66,12 @@ public function testItThrowsExceptionOnFailure()
 
     public function testItThrowsExceptionOnTimeout()
     {
-        $response = $this->createStub(ResponseInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
         $responseContent = file_get_contents(\dirname(__DIR__, 6).'/fixtures/Bridge/Gemini/code_execution_outcome_deadline_exceeded.json');
 
+        $response
+            ->method('getStatusCode')
+            ->willReturn(200);
         $response
             ->method('toArray')
             ->willReturn(json_decode($responseContent, true));
diff --git a/src/platform/tests/Bridge/OpenAi/Gpt/ResultConverterTest.php b/src/platform/tests/Bridge/OpenAi/Gpt/ResultConverterTest.php
index 447397b10..dbf51f5a9 100644
--- a/src/platform/tests/Bridge/OpenAi/Gpt/ResultConverterTest.php
+++ b/src/platform/tests/Bridge/OpenAi/Gpt/ResultConverterTest.php
@@ -18,7 +18,9 @@
 use Symfony\AI\Platform\Bridge\OpenAi\Gpt\ResultConverter;
 use Symfony\AI\Platform\Exception\AuthenticationException;
 use Symfony\AI\Platform\Exception\ContentFilterException;
+use Symfony\AI\Platform\Exception\NotFoundException;
 use Symfony\AI\Platform\Exception\RuntimeException;
+use Symfony\AI\Platform\Exception\ServiceUnavailableException;
 use Symfony\AI\Platform\Result\ChoiceResult;
 use Symfony\AI\Platform\Result\RawHttpResult;
 use Symfony\AI\Platform\Result\TextResult;
@@ -39,6 +41,7 @@ public function testConvertTextResult()
     {
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
         $httpResponse->method('toArray')->willReturn([
             'choices' => [
                 [
@@ -61,6 +64,7 @@ public function testConvertToolCallResult()
     {
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
         $httpResponse->method('toArray')->willReturn([
             'choices' => [
                 [
@@ -97,6 +101,7 @@ public function testConvertMultipleChoices()
     {
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
         $httpResponse->method('toArray')->willReturn([
             'choices' => [
                 [
@@ -129,6 +134,7 @@ public function testContentFilterException()
     {
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
 
         $httpResponse->expects($this->exactly(1))
             ->method('toArray')
@@ -161,11 +167,9 @@ public function testThrowsAuthenticationExceptionOnInvalidApiKey()
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
         $httpResponse->method('getStatusCode')->willReturn(401);
-        $httpResponse->method('getContent')->willReturn(json_encode([
-            'error' => [
-                'message' => 'Invalid API key provided: sk-invalid',
-            ],
-        ]));
+        $httpResponse->method('getContent')
+            ->with(false)
+            ->willReturn('{"error": {"message": "Invalid API key provided: sk-invalid"}}');
 
         $this->expectException(AuthenticationException::class);
         $this->expectExceptionMessage('Invalid API key provided: sk-invalid');
@@ -177,6 +181,7 @@ public function testThrowsExceptionWhenNoChoices()
     {
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
         $httpResponse->method('toArray')->willReturn([]);
 
         $this->expectException(RuntimeException::class);
@@ -189,6 +194,7 @@ public function testThrowsExceptionForUnsupportedFinishReason()
     {
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
         $httpResponse->method('toArray')->willReturn([
             'choices' => [
                 [
@@ -206,4 +212,32 @@ public function testThrowsExceptionForUnsupportedFinishReason()
 
         $converter->convert(new RawHttpResult($httpResponse));
     }
+
+    public function testThrowsNotFoundExceptionForMissingModel()
+    {
+        $converter = new ResultConverter();
+        $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(404);
+        $httpResponse->method('getContent')
+            ->with(false)
+            ->willReturn('{"error": {"message": "Model gpt-5 not found"}}');
+
+        $this->expectException(NotFoundException::class);
+        $this->expectExceptionMessage('Model gpt-5 not found');
+        $converter->convert(new RawHttpResult($httpResponse));
+    }
+
+    public function testThrowsServiceUnavailableExceptionFor503()
+    {
+        $converter = new ResultConverter();
+        $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(503);
+        $httpResponse->method('getContent')
+            ->with(false)
+            ->willReturn('{"error": {"message": "OpenAI servers are temporarily overloaded"}}');
+
+        $this->expectException(ServiceUnavailableException::class);
+        $this->expectExceptionMessage('OpenAI servers are temporarily overloaded');
+        $converter->convert(new RawHttpResult($httpResponse));
+    }
 }
diff --git a/src/platform/tests/Bridge/Perplexity/ResultConverterTest.php b/src/platform/tests/Bridge/Perplexity/ResultConverterTest.php
index 6d6bdb740..2910e0010 100644
--- a/src/platform/tests/Bridge/Perplexity/ResultConverterTest.php
+++ b/src/platform/tests/Bridge/Perplexity/ResultConverterTest.php
@@ -36,6 +36,7 @@ public function testConvertTextResult()
     {
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
         $httpResponse->method('toArray')->willReturn([
             'choices' => [
                 [
@@ -58,6 +59,7 @@ public function testConvertMultipleChoices()
     {
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
         $httpResponse->method('toArray')->willReturn([
             'choices' => [
                 [
@@ -90,6 +92,7 @@ public function testThrowsExceptionWhenNoChoices()
     {
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
         $httpResponse->method('toArray')->willReturn([]);
 
         $this->expectException(RuntimeException::class);
@@ -102,6 +105,7 @@ public function testThrowsExceptionForUnsupportedFinishReason()
     {
         $converter = new ResultConverter();
         $httpResponse = self::createMock(ResponseInterface::class);
+        $httpResponse->method('getStatusCode')->willReturn(200);
         $httpResponse->method('toArray')->willReturn([
             'choices' => [
                 [
diff --git a/src/platform/tests/Exception/HttpErrorHandlerTest.php b/src/platform/tests/Exception/HttpErrorHandlerTest.php
new file mode 100644
index 000000000..3ec53814d
--- /dev/null
+++ b/src/platform/tests/Exception/HttpErrorHandlerTest.php
@@ -0,0 +1,191 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\AI\Platform\Tests\Exception;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use Symfony\AI\Platform\Exception\AuthenticationException;
+use Symfony\AI\Platform\Exception\HttpErrorHandler;
+use Symfony\AI\Platform\Exception\NotFoundException;
+use Symfony\AI\Platform\Exception\RateLimitExceededException;
+use Symfony\AI\Platform\Exception\RuntimeException;
+use Symfony\AI\Platform\Exception\ServiceUnavailableException;
+use Symfony\Component\HttpClient\MockHttpClient;
+use Symfony\Component\HttpClient\Response\MockResponse;
+
+#[CoversClass(HttpErrorHandler::class)]
+class HttpErrorHandlerTest extends TestCase
+{
+    public function testHandleHttpErrorWithSuccessfulResponse()
+    {
+        $mockResponse = new MockResponse('{"success": true}', ['http_code' => 200]);
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectNotToPerformAssertions();
+        HttpErrorHandler::handleHttpError($response);
+    }
+
+    public function testHandleAuthenticationError()
+    {
+        $mockResponse = new MockResponse(
+            '{"error": {"message": "Invalid API key"}}',
+            ['http_code' => 401]
+        );
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectException(AuthenticationException::class);
+        $this->expectExceptionMessage('Invalid API key');
+        HttpErrorHandler::handleHttpError($response);
+    }
+
+    public function testHandleNotFoundError()
+    {
+        $mockResponse = new MockResponse(
+            '{"error": {"message": "Model not found"}}',
+            ['http_code' => 404]
+        );
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectException(NotFoundException::class);
+        $this->expectExceptionMessage('Model not found');
+        HttpErrorHandler::handleHttpError($response);
+    }
+
+    public function testHandleServiceUnavailableError()
+    {
+        $mockResponse = new MockResponse(
+            '{"error": {"message": "Service temporarily unavailable"}}',
+            ['http_code' => 503]
+        );
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectException(ServiceUnavailableException::class);
+        $this->expectExceptionMessage('Service temporarily unavailable');
+        HttpErrorHandler::handleHttpError($response);
+    }
+
+    public function testHandleGenericClientError()
+    {
+        $mockResponse = new MockResponse(
+            '{"error": {"message": "Bad request"}}',
+            ['http_code' => 400]
+        );
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('HTTP 400: Bad request');
+        HttpErrorHandler::handleHttpError($response);
+    }
+
+    public function testHandleErrorWithDifferentMessageFormats()
+    {
+        $mockResponse = new MockResponse(
+            '{"error": "Direct error message"}',
+            ['http_code' => 400]
+        );
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('HTTP 400: Direct error message');
+        HttpErrorHandler::handleHttpError($response);
+    }
+
+    public function testHandleErrorWithMessageField()
+    {
+        $mockResponse = new MockResponse(
+            '{"message": "Simple message format"}',
+            ['http_code' => 400]
+        );
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('HTTP 400: Simple message format');
+        HttpErrorHandler::handleHttpError($response);
+    }
+
+    public function testHandleErrorWithDetailField()
+    {
+        $mockResponse = new MockResponse(
+            '{"detail": "Detailed error information"}',
+            ['http_code' => 400]
+        );
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('HTTP 400: Detailed error information');
+        HttpErrorHandler::handleHttpError($response);
+    }
+
+    public function testHandleErrorWithInvalidJson()
+    {
+        $mockResponse = new MockResponse(
+            'Plain text error message',
+            ['http_code' => 500]
+        );
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('HTTP 500: Plain text error message');
+        HttpErrorHandler::handleHttpError($response);
+    }
+
+    public function testHandleErrorWithEmptyResponse()
+    {
+        $mockResponse = new MockResponse('', ['http_code' => 500]);
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('HTTP 500: HTTP 500 error');
+        HttpErrorHandler::handleHttpError($response);
+    }
+
+    public function testHandleRateLimitWithRetryAfterHeader()
+    {
+        $mockResponse = new MockResponse(
+            '{"error": "Rate limit exceeded"}',
+            ['http_code' => 429, 'response_headers' => ['Retry-After' => ['60']]]
+        );
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        try {
+            HttpErrorHandler::handleHttpError($response);
+            $this->fail('Expected RateLimitExceededException was not thrown');
+        } catch (RateLimitExceededException $e) {
+            $this->assertEquals(60.0, $e->getRetryAfter());
+        }
+    }
+
+    public function testHandleRateLimitWithoutRetryAfterHeader()
+    {
+        $mockResponse = new MockResponse(
+            '{"error": "Rate limit exceeded"}',
+            ['http_code' => 429]
+        );
+        $client = new MockHttpClient($mockResponse);
+        $response = $client->request('GET', 'https://example.com');
+
+        $this->expectException(RateLimitExceededException::class);
+        $this->expectExceptionMessage('Rate limit exceeded.');
+        HttpErrorHandler::handleHttpError($response);
+    }
+}