diff --git a/README.md b/README.md
index 91f0df9..381845e 100644
--- a/README.md
+++ b/README.md
@@ -26,6 +26,10 @@ _This library is not developed or endorsed by Google._
   - [Streaming Chat Session](#streaming-chat-session)
   - [Tokens counting](#tokens-counting)
   - [Listing models](#listing-models)
+  - [Advanced Usages](#advanced-usages)
+    - [Safety Settings and Generation Configuration](#safety-settings-and-generation-configuration)
+    - [Using your own HTTP client](#using-your-own-http-client)
+    - [Using your own HTTP client for streaming responses](#using-your-own-http-client-for-streaming-responses)
 
 ## Installation
 
@@ -173,7 +177,7 @@ $callback = function (GenerateContentResponse $response): void {
 
 $client->geminiPro()->generateContentStream(
     $callback,
-    new TextPart('PHP in less than 100 chars')
+    [new TextPart('PHP in less than 100 chars')],
 );
 // Response #0
 // PHP: a versatile, general-purpose scripting language for web development, popular for
@@ -287,3 +291,79 @@ print_r($response->models);
 //    )
 //]
 ```
+
+### Advanced Usages
+
+#### Safety Settings and Generation Configuration
+
+```php
+$client = new GeminiAPI\Client('GEMINI_API_KEY');
+$safetySetting = new GeminiAPI\SafetySetting(
+    HarmCategory::HARM_CATEGORY_HATE_SPEECH,
+    HarmBlockThreshold::BLOCK_LOW_AND_ABOVE,
+);
+$generationConfig = (new GeminiAPI\GenerationConfig())
+    ->withCandidateCount(1)
+    ->withMaxOutputTokens(40)
+    ->withTemperature(0.5)
+    ->withTopK(40)
+    ->withTopP(0.6)
+    ->withStopSequences(['STOP']);
+
+$response = $client->geminiPro()
+    ->withAddedSafetySetting($safetySetting)
+    ->withGenerationConfig($generationConfig)
+    ->generateContent(
+        new TextPart('PHP in less than 100 chars')
+    );
+```
+
+#### Using your own HTTP client
+
+```php
+$guzzle = new GuzzleHttp\Client([
+  'proxy' => 'http://localhost:8125',
+]);
+$client = new GeminiAPI\Client('GEMINI_API_KEY', $guzzle);
+
+$response = $client->geminiPro()->generateContent(
+    new TextPart('PHP in less than 100 chars')
+);
+```
+
+#### Using your own HTTP client for streaming responses
+
+> Requires `curl` extension to be enabled
+
+Since streaming responses are fetched using `curl` extension, they cannot use the custom HTTP client passed to the Gemini Client.
+You need to pass a `CurlHandler` if you want to override connection options.
+
+The following curl options will be overwritten by the Gemini Client.
+
+- `CURLOPT_URL`
+- `CURLOPT_POST`
+- `CURLOPT_POSTFIELDS`
+- `CURLOPT_WRITEFUNCTION`
+
+You can also pass the headers you want to be used in the requests.
+
+```php
+$client = new GeminiAPI\Client('GEMINI_API_KEY');
+
+$callback = function (GenerateContentResponse $response): void {
+    print $response->text();
+};
+
+$ch = curl_init();
+curl_setopt($ch, CURLOPT_PROXY, 'http://localhost:8125');
+
+$client->withRequestHeaders([
+        'User-Agent' => 'My Gemini-backed app'
+    ])
+    ->geminiPro()
+    ->generateContentStream(
+        $callback,
+        [new TextPart('PHP in less than 100 chars')],
+        $ch,
+    );
+```
diff --git a/src/Client.php b/src/Client.php
index 98701d7..9a034c5 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -27,6 +27,7 @@
 use Psr\Http\Message\StreamFactoryInterface;
 use RuntimeException;
 
+use function array_map;
 use function curl_close;
 use function curl_exec;
 use function curl_getinfo;
@@ -35,10 +36,17 @@
 use function extension_loaded;
 use function json_decode;
 use function sprintf;
+use function strtolower;
 
 class Client implements GeminiClientInterface
 {
     private string $baseUrl = 'https://generativelanguage.googleapis.com';
+
+    /**
+     * @var array<string, string>
+     */
+    private array $requestHeaders = [];
+
     public function __construct(
         private readonly string  $apiKey,
         private ?HttpClientInterface $client = null,
@@ -88,13 +96,16 @@ public function generateContent(GenerateContentRequest $request): GenerateConten
     }
 
     /**
+     * @param GenerateContentStreamRequest $request
      * @param callable(GenerateContentResponse): void $callback
+     * @param CurlHandle|null $curl
      * @throws BadMethodCallException
      * @throws RuntimeException
      */
     public function generateContentStream(
         GenerateContentStreamRequest $request,
         callable $callback,
+        ?CurlHandle $curl = null,
     ): void {
         if (!extension_loaded('curl')) {
             throw new BadMethodCallException('Gemini API requires `curl` extension for streaming responses');
@@ -120,18 +131,25 @@ public function generateContentStream(
                 );
         };
 
-        $ch = curl_init("{$this->baseUrl}/v1/{$request->getOperation()}");
+        $ch = $curl ?? curl_init();
 
         if ($ch === false) {
             throw new RuntimeException('Gemini API cannot initialize streaming content request');
         }
 
+        $headers = $this->requestHeaders + [
+            'content-type' => 'application/json',
+            self::API_KEY_HEADER_NAME => $this->apiKey,
+        ];
+        $headerLines = [];
+        foreach ($headers as $name => $value) {
+            $headerLines[] = "{$name}: {$value}";
+        }
+
+        curl_setopt($ch, CURLOPT_URL, "{$this->baseUrl}/v1/{$request->getOperation()}");
         curl_setopt($ch, CURLOPT_POST, true);
         curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($request));
-        curl_setopt($ch, CURLOPT_HTTPHEADER, [
-            'Content-type: application/json',
-            self::API_KEY_HEADER_NAME . ": {$this->apiKey}",
-        ]);
+        curl_setopt($ch, CURLOPT_HTTPHEADER, $headerLines);
         curl_setopt($ch, CURLOPT_WRITEFUNCTION, $writeFunction);
         curl_exec($ch);
         curl_close($ch);
@@ -179,6 +197,18 @@ public function withBaseUrl(string $baseUrl): self
         return $clone;
     }
 
+    /**
+     * @param array<string, string> $headers
+     * @return self
+     */
+    public function withRequestHeaders(array $headers): self
+    {
+        $clone = clone $this;
+        $clone->requestHeaders = array_map(strtolower(...), $headers);
+
+        return $clone;
+    }
+
     /**
      * @throws ClientExceptionInterface
      */
@@ -193,6 +223,10 @@ private function doRequest(RequestInterface $request): string
             ->createRequest($request->getHttpMethod(), $uri)
             ->withAddedHeader(self::API_KEY_HEADER_NAME, $this->apiKey);
 
+        foreach ($this->requestHeaders as $name => $value) {
+            $httpRequest = $httpRequest->withAddedHeader($name, $value);
+        }
+
         $payload = $request->getHttpPayload();
         if (!empty($payload)) {
             $stream = $this->streamFactory->createStream($payload);
diff --git a/src/GenerativeModel.php b/src/GenerativeModel.php
index 216a886..0108f35 100644
--- a/src/GenerativeModel.php
+++ b/src/GenerativeModel.php
@@ -5,6 +5,7 @@
 namespace GeminiAPI;
 
 use BadMethodCallException;
+use CurlHandle;
 use GeminiAPI\Enums\ModelName;
 use GeminiAPI\Enums\Role;
 use GeminiAPI\Requests\CountTokensRequest;
@@ -62,26 +63,33 @@ public function generateContentWithContents(array $contents): GenerateContentRes
 
     /**
      * @param callable(GenerateContentResponse): void $callback
-     * @param PartInterface ...$parts
+     * @param PartInterface[] $parts
+     * @param CurlHandle|null $ch
      * @return void
-     * @throws BadMethodCallException
      */
     public function generateContentStream(
         callable $callback,
-        PartInterface ...$parts,
+        array $parts,
+        ?CurlHandle $ch = null,
     ): void {
+        $this->ensureArrayOfType($parts, PartInterface::class);
+
         $content = new Content($parts, Role::User);
 
-        $this->generateContentStreamWithContents($callback, [$content]);
+        $this->generateContentStreamWithContents($callback, [$content], $ch);
     }
 
     /**
      * @param callable(GenerateContentResponse): void $callback
      * @param Content[] $contents
+     * @param CurlHandle|null $ch
      * @return void
      */
-    public function generateContentStreamWithContents(callable $callback, array $contents): void
-    {
+    public function generateContentStreamWithContents(
+        callable $callback,
+        array $contents,
+        ?CurlHandle $ch = null,
+    ): void {
         $this->ensureArrayOfType($contents, Content::class);
 
         $request = new GenerateContentStreamRequest(
@@ -91,7 +99,7 @@ public function generateContentStreamWithContents(callable $callback, array $con
             $this->generationConfig,
         );
 
-        $this->client->generateContentStream($request, $callback);
+        $this->client->generateContentStream($request, $callback, $ch);
     }
 
     public function startChat(): ChatSession