diff --git a/packages/core/src/core/client.ts b/packages/core/src/core/client.ts
index 90f86df26f1..6760428d464 100644
--- a/packages/core/src/core/client.ts
+++ b/packages/core/src/core/client.ts
@@ -429,7 +429,8 @@ export class GeminiClient {
       const text =
         message.parts
           ?.filter(
-            (part): part is { text: string } => typeof part.text === 'string',
+            (part): part is { text: string } =>
+              typeof part.text === 'string' && !part.thought,
           )
           .map((part) => part.text)
           .join('') ?? '';
diff --git a/packages/core/src/core/geminiChat.test.ts b/packages/core/src/core/geminiChat.test.ts
index 7e20b94ed5d..b1254f636b8 100644
--- a/packages/core/src/core/geminiChat.test.ts
+++ b/packages/core/src/core/geminiChat.test.ts
@@ -4136,6 +4136,27 @@ describe('GeminiChat', async () => {
       expect(chat.getLastModelMessageText()).toBe('new answer');
       expect(structuredCloneSpy).not.toHaveBeenCalled();
     });
+
+    it('filters out thought parts from the last model message', () => {
+      chat.addHistory({
+        role: 'model',
+        parts: [
+          { text: 'internal reasoning...', thought: true },
+          { text: 'visible response' },
+        ],
+      });
+
+      expect(chat.getLastModelMessageText()).toBe('visible response');
+    });
+
+    it('returns undefined when all text parts are thoughts', () => {
+      chat.addHistory({
+        role: 'model',
+        parts: [{ text: 'only thinking', thought: true }],
+      });
+
+      expect(chat.getLastModelMessageText()).toBeUndefined();
+    });
   });
 
   describe('sendMessageStream with retries', () => {
diff --git a/packages/core/src/core/geminiChat.ts b/packages/core/src/core/geminiChat.ts
index 6ade570acdd..158d87ec3e0 100644
--- a/packages/core/src/core/geminiChat.ts
+++ b/packages/core/src/core/geminiChat.ts
@@ -2776,7 +2776,8 @@ export class GeminiChat {
       const text =
         message.parts
           ?.filter(
-            (part): part is { text: string } => typeof part.text === 'string',
+            (part): part is { text: string } =>
+              typeof part.text === 'string' && !part.thought,
           )
           .map((part) => part.text)
           .join('') ?? '';