diff --git a/src/proxy/google-ai.ts b/src/proxy/google-ai.ts
index 5ac7d9d..95365f3 100644
--- a/src/proxy/google-ai.ts
+++ b/src/proxy/google-ai.ts
@@ -178,27 +178,23 @@ const googleAIRouter = Router();
 googleAIRouter.get("/v1/models", handleModelRequest);
 googleAIRouter.get("/:apiVersion(v1alpha|v1beta)/models", handleNativeModelRequest);
 
-// Native Google AI chat completion endpoint
-googleAIRouter.post(
-  "/:apiVersion(v1alpha|v1beta)/models/:modelId:(generateContent|streamGenerateContent)",
-  ipLimiter,
-  createPreprocessorMiddleware(
-    { inApi: "google-ai", outApi: "google-ai", service: "google-ai" },
-    { beforeTransform: [maybeReassignModel], afterTransform: [setStreamFlag] }
-  ),
-  googleAIProxy
-);
-
-// OpenAI-to-Google AI compatibility endpoint.
-googleAIRouter.post(
-  "/v1/chat/completions",
-  ipLimiter,
-  createPreprocessorMiddleware(
-    { inApi: "openai", outApi: "google-ai", service: "google-ai" },
-    { afterTransform: [maybeReassignModel] }
-  ),
-  googleAIProxy
-);
+/**
+ * Processes the thinking budget for Gemini 2.5 Flash model.
+ * Ensures the budget is within the valid range of 0-24576 tokens.
+ */
+function processThinkingBudget(req: Request) {
+  if (req.body.generationConfig?.thinkingConfig?.thinkingBudget !== undefined) {
+    // Ensure thinkingBudget is within allowed range (0-24576)
+    const budget = req.body.generationConfig.thinkingConfig.thinkingBudget;
+    
+    // If it's a number, validate range
+    if (typeof budget === 'number') {
+      req.body.generationConfig.thinkingConfig.thinkingBudget = 
+        Math.max(0, Math.min(budget, 24576));
+    }
+    // If it's "auto", leave as is
+  }
+}
 
 function setStreamFlag(req: Request) {
   const isStreaming = req.url.includes("streamGenerateContent");
@@ -236,4 +232,26 @@ function maybeReassignModel(req: Request) {
   req.body.model = "gemini-1.5-pro-latest";
 }
 
+// Native Google AI chat completion endpoint
+googleAIRouter.post(
+  "/:apiVersion(v1alpha|v1beta)/models/:modelId:(generateContent|streamGenerateContent)",
+  ipLimiter,
+  createPreprocessorMiddleware(
+    { inApi: "google-ai", outApi: "google-ai", service: "google-ai" },
+    { beforeTransform: [maybeReassignModel], afterTransform: [setStreamFlag, processThinkingBudget] }
+  ),
+  googleAIProxy
+);
+
+// OpenAI-to-Google AI compatibility endpoint.
+googleAIRouter.post(
+  "/v1/chat/completions",
+  ipLimiter,
+  createPreprocessorMiddleware(
+    { inApi: "openai", outApi: "google-ai", service: "google-ai" },
+    { afterTransform: [maybeReassignModel, processThinkingBudget] }
+  ),
+  googleAIProxy
+);
+
 export const googleAI = googleAIRouter;
diff --git a/src/shared/api-schemas/google-ai.ts b/src/shared/api-schemas/google-ai.ts
index 4fb92f0..c4b7cf6 100644
--- a/src/shared/api-schemas/google-ai.ts
+++ b/src/shared/api-schemas/google-ai.ts
@@ -155,6 +155,12 @@ export const transformOpenAIToGoogleAI: APIFormatTransformer<
   stops.push(...Array.from(foundNames).map((name) => `\n${name}:`));
   stops = [...new Set(stops)].slice(0, 5);
 
+  // Handle thinking budget from the original request
+  let thinkingConfig = undefined;
+  if (body.generationConfig?.thinkingConfig || body.thinkingConfig) {
+    thinkingConfig = body.generationConfig?.thinkingConfig || body.thinkingConfig;
+  }
+
   return {
     model: req.body.model,
     stream: rest.stream,
@@ -166,6 +172,7 @@ export const transformOpenAIToGoogleAI: APIFormatTransformer<
       topP: rest.top_p,
       topK: 40, // openai schema doesn't have this, google ai defaults to 40
       temperature: rest.temperature,
+      ...(thinkingConfig ? { thinkingConfig } : {})
     },
     safetySettings: [
       { category: "HARM_CATEGORY_HARASSMENT", threshold: "BLOCK_NONE" },