diff --git a/packages/core/src/config/defaultModelConfigs.ts b/packages/core/src/config/defaultModelConfigs.ts
index 1849b1e206..5df8da93f5 100644
--- a/packages/core/src/config/defaultModelConfigs.ts
+++ b/packages/core/src/config/defaultModelConfigs.ts
@@ -334,7 +334,7 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
       family: 'gemma-4',
       isPreview: true,
       isVisible: true,
-      features: { thinking: false, multimodalToolUse: false },
+      features: { thinking: true, multimodalToolUse: false },
     },
     'gemma-4-31b-it': {
       tier: 'pro',
diff --git a/packages/core/src/core/geminiChat.ts b/packages/core/src/core/geminiChat.ts
index c480c3800b..f7fece6c33 100644
--- a/packages/core/src/core/geminiChat.ts
+++ b/packages/core/src/core/geminiChat.ts
@@ -1072,9 +1072,13 @@ export class GeminiChat {
     }
 
     const thoughtPart = content.parts[0];
-    if (thoughtPart.text) {
+    const rawText =
+      typeof thoughtPart.thought === 'string'
+        ? thoughtPart.thought
+        : (thoughtPart.text ?? '');
+
+    if (rawText) {
       // Extract subject and description using the same logic as turn.ts
-      const rawText = thoughtPart.text;
       const subjectStringMatches = rawText.match(/\*\*(.*?)\*\*/s);
       const subject = subjectStringMatches
         ? subjectStringMatches[1].trim()
diff --git a/packages/core/src/core/turn.test.ts b/packages/core/src/core/turn.test.ts
index 435323f73d..ec5466e3ee 100644
--- a/packages/core/src/core/turn.test.ts
+++ b/packages/core/src/core/turn.test.ts
@@ -733,7 +733,7 @@ describe('Turn', () => {
       },
       {
         description: 'should yield thought events with traceId',
-        part: { text: '[Thought: thinking]', thought: 'thinking' },
+        part: { text: '[Thought: thinking]', thought: true },
         responseId: 'trace-456',
         expectedEvent: {
           type: GeminiEventType.Thought,
@@ -774,7 +774,7 @@ describe('Turn', () => {
               {
                 content: {
                   parts: [
-                    { text: '**Planning** the solution', thought: 'planning' },
+                    { text: '**Planning** the solution', thought: true },
                     { text: 'I will help you with that.' },
                   ],
                 },
diff --git a/packages/core/src/core/turn.ts b/packages/core/src/core/turn.ts
index 9c0e536c48..3e3a4007f7 100644
--- a/packages/core/src/core/turn.ts
+++ b/packages/core/src/core/turn.ts
@@ -308,7 +308,11 @@ export class Turn {
         const parts = resp.candidates?.[0]?.content?.parts ?? [];
         for (const part of parts) {
           if (part.thought) {
-            const thought = parseThought(part.text ?? '');
+            const rawThought =
+              typeof part.thought === 'string'
+                ? part.thought
+                : (part.text ?? '');
+            const thought = parseThought(rawThought);
             yield {
               type: GeminiEventType.Thought,
               value: thought,