diff --git a/src/Libraries/FirebaseClient.php b/src/Libraries/FirebaseClient.php
index aaee89c..028c122 100644
--- a/src/Libraries/FirebaseClient.php
+++ b/src/Libraries/FirebaseClient.php
@@ -365,6 +365,60 @@ public function sendMulticast(
         return $results;
     }
 
+    /**
+     * Send FCM message to a topic
+     *
+     * @param string $topic        Topic name (without /topics/ prefix)
+     * @param array  $notification Notification payload (title, body)
+     * @param array  $data         Data payload
+     *
+     * @return ResponseInterface
+     *
+     * @throws \GuzzleHttp\Exception\GuzzleException On HTTP error
+     */
+    public function sendToTopic(
+        string $topic,
+        array $notification = [],
+        array $data = []
+    ): ResponseInterface {
+        $message = ['topic' => $topic];
+        if (!empty($notification)) {
+            $message['notification'] = $notification;
+        }
+        if (!empty($data)) {
+            $message['data'] = $data;
+        }
+
+        return $this->sendMessage($message);
+    }
+
+    /**
+     * Send FCM message to a topic condition
+     *
+     * @param string $condition    Topic condition expression (e.g. "'topicA' in topics && 'topicB' in topics")
+     * @param array  $notification Notification payload (title, body)
+     * @param array  $data         Data payload
+     *
+     * @return ResponseInterface
+     *
+     * @throws \GuzzleHttp\Exception\GuzzleException On HTTP error
+     */
+    public function sendToCondition(
+        string $condition,
+        array $notification = [],
+        array $data = []
+    ): ResponseInterface {
+        $message = ['condition' => $condition];
+        if (!empty($notification)) {
+            $message['notification'] = $notification;
+        }
+        if (!empty($data)) {
+            $message['data'] = $data;
+        }
+
+        return $this->sendMessage($message);
+    }
+
     /**
      * Generate JWT manually using OpenSSL
      *
@@ -375,8 +429,8 @@ public function sendMulticast(
      */
     private function createJWT(array $payload, string $privateKey): string
     {
-        $header = base64_encode(json_encode(['alg' => 'RS256', 'typ' => 'JWT']));
-        $payload = base64_encode(json_encode($payload));
+        $header = rtrim(strtr(base64_encode(json_encode(['alg' => 'RS256', 'typ' => 'JWT'])), '+/', '-_'), '=');
+        $payload = rtrim(strtr(base64_encode(json_encode($payload)), '+/', '-_'), '=');
 
         $signature = '';
         openssl_sign(
@@ -386,8 +440,8 @@ private function createJWT(array $payload, string $privateKey): string
             OPENSSL_ALGO_SHA256
         );
 
-        $signature = base64_encode($signature);
+        $signature = rtrim(strtr(base64_encode($signature), '+/', '-_'), '=');
 
-        return str_replace(['+', '/', '='], ['-', '_', ''], $header . '.' . $payload . '.' . $signature);
+        return $header . '.' . $payload . '.' . $signature;
     }
 }
diff --git a/tests/Libraries/FirebaseClientTest.php b/tests/Libraries/FirebaseClientTest.php
index 32927c2..5bf0201 100644
--- a/tests/Libraries/FirebaseClientTest.php
+++ b/tests/Libraries/FirebaseClientTest.php
@@ -273,6 +273,101 @@ public function testSendMulticastWithData(): void
         $this->assertEquals(0, $result['failure']);
     }
 
+    /** @test */
+    public function testSendToTopic(): void
+    {
+        $mockResponse = new Response(
+            200,
+            [],
+            json_encode(['name' => 'projects/test-project/messages/123'])
+        );
+
+        $guzzleMock = Mockery::mock(GuzzleClient::class);
+        $guzzleMock->shouldReceive('send')
+            ->once()
+            ->andReturn($mockResponse);
+
+        $client = $this->createMockedClient($guzzleMock);
+
+        $response = $client->sendToTopic(
+            'news',
+            ['title' => 'Breaking', 'body' => 'Something happened'],
+            ['key' => 'value']
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+    }
+
+    /** @test */
+    public function testSendToTopicWithNotificationOnly(): void
+    {
+        $mockResponse = new Response(
+            200,
+            [],
+            json_encode(['name' => 'projects/test-project/messages/123'])
+        );
+
+        $guzzleMock = Mockery::mock(GuzzleClient::class);
+        $guzzleMock->shouldReceive('send')
+            ->once()
+            ->andReturn($mockResponse);
+
+        $client = $this->createMockedClient($guzzleMock);
+
+        $response = $client->sendToTopic('news', ['title' => 'Test', 'body' => 'Body']);
+
+        $this->assertEquals(200, $response->getStatusCode());
+    }
+
+    /** @test */
+    public function testSendToCondition(): void
+    {
+        $mockResponse = new Response(
+            200,
+            [],
+            json_encode(['name' => 'projects/test-project/messages/123'])
+        );
+
+        $guzzleMock = Mockery::mock(GuzzleClient::class);
+        $guzzleMock->shouldReceive('send')
+            ->once()
+            ->andReturn($mockResponse);
+
+        $client = $this->createMockedClient($guzzleMock);
+
+        $response = $client->sendToCondition(
+            "'news' in topics || 'alerts' in topics",
+            ['title' => 'Update', 'body' => 'New update available'],
+            ['version' => '2.0']
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+    }
+
+    /** @test */
+    public function testSendToConditionWithNotificationOnly(): void
+    {
+        $mockResponse = new Response(
+            200,
+            [],
+            json_encode(['name' => 'projects/test-project/messages/123'])
+        );
+
+        $guzzleMock = Mockery::mock(GuzzleClient::class);
+        $guzzleMock->shouldReceive('send')
+            ->once()
+            ->andReturn($mockResponse);
+
+        $client = $this->createMockedClient($guzzleMock);
+
+        $response = $client->sendToCondition(
+            "'news' in topics && 'premium' in topics",
+            ['title' => 'Premium News', 'body' => 'Exclusive content']
+        );
+
+        $this->assertEquals(200, $response->getStatusCode());
+    }
+
     /** @test */
     public function testSetProxy(): void
     {