diff --git a/src/Data/ThinkingConfig.php b/src/Data/ThinkingConfig.php
index 750978c..8377b77 100644
--- a/src/Data/ThinkingConfig.php
+++ b/src/Data/ThinkingConfig.php
@@ -16,38 +16,33 @@ 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  int|null  $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 ?int $thinkingBudget = null,
         public readonly ?ThinkingLevel $thinkingLevel = null,
     ) {}
 
     /**
-     * @param  array{ includeThoughts: bool, thinkingBudget: int, thinkingLevel: ?ThinkingLevel}  $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'],
+            thinkingBudget: $attributes['thinkingBudget'] ?? null,
             thinkingLevel: $attributes['thinkingLevel'] ?? null
         );
     }
 
     public function toArray(): array
     {
-        $items = [
+        return array_filter([
             'includeThoughts' => $this->includeThoughts,
             'thinkingBudget' => $this->thinkingBudget,
-        ];
-
-        if ($this->thinkingLevel) {
-            $items['thinkingLevel'] = $this->thinkingLevel->value;
-        }
-
-        return $items;
+            'thinkingLevel' => $this->thinkingLevel?->value,
+        ], fn ($value) => $value !== null);
     }
 }
diff --git a/src/Enums/ThinkingLevel.php b/src/Enums/ThinkingLevel.php
index 355a091..afcf092 100644
--- a/src/Enums/ThinkingLevel.php
+++ b/src/Enums/ThinkingLevel.php
@@ -9,6 +9,8 @@
  *
  * Gemini 3 Pro: low, high
  * Gemini 3 Flash: minimal, low, medium, high
+ *
+ * https://ai.google.dev/gemini-api/docs/thinking#thinking-levels
  */
 enum ThinkingLevel: string
 {