diff --git a/src/Data/ThinkingConfig.php b/src/Data/ThinkingConfig.php
index e0c0644..750978c 100644
--- a/src/Data/ThinkingConfig.php
+++ b/src/Data/ThinkingConfig.php
@@ -5,6 +5,7 @@
 namespace Gemini\Data;
 
 use Gemini\Contracts\Arrayable;
+use Gemini\Enums\ThinkingLevel;
 
 /**
  * Config for thinking features.
@@ -16,28 +17,37 @@ final class ThinkingConfig implements Arrayable
     /**
      * @param  bool  $includeThoughts  Indicates whether to include thoughts in the response. If true, thoughts are returned only when available.
      * @param  int  $thinkingBudget  The number of thoughts tokens that the model should generate.
+     * @param  ThinkingLevel|null  $thinkingLevel  Controls reasoning behavior.
      */
     public function __construct(
         public readonly bool $includeThoughts,
         public readonly int $thinkingBudget,
+        public readonly ?ThinkingLevel $thinkingLevel = null,
     ) {}
 
     /**
-     * @param  array{ includeThoughts: bool, thinkingBudget: int}  $attributes
+     * @param  array{ includeThoughts: bool, thinkingBudget: int, thinkingLevel: ?ThinkingLevel}  $attributes
      */
     public static function from(array $attributes): self
     {
         return new self(
             includeThoughts: $attributes['includeThoughts'],
             thinkingBudget: $attributes['thinkingBudget'],
+            thinkingLevel: $attributes['thinkingLevel'] ?? null
         );
     }
 
     public function toArray(): array
     {
-        return [
+        $items = [
             'includeThoughts' => $this->includeThoughts,
             'thinkingBudget' => $this->thinkingBudget,
         ];
+
+        if ($this->thinkingLevel) {
+            $items['thinkingLevel'] = $this->thinkingLevel->value;
+        }
+
+        return $items;
     }
 }
diff --git a/src/Enums/ThinkingLevel.php b/src/Enums/ThinkingLevel.php
new file mode 100644
index 0000000..355a091
--- /dev/null
+++ b/src/Enums/ThinkingLevel.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Gemini\Enums;
+
+/**
+ * Controls reasoning behavior.
+ *
+ * Gemini 3 Pro: low, high
+ * Gemini 3 Flash: minimal, low, medium, high
+ */
+enum ThinkingLevel: string
+{
+    case LOW = 'low';
+    case HIGH = 'high';
+    case MINIMAL = 'minimal';
+    case MEDIUM = 'medium';
+}