diff --git a/packages/core/src/core/geminiChat.test.ts b/packages/core/src/core/geminiChat.test.ts
index 6cdc6ebdfa..d85609fec5 100644
--- a/packages/core/src/core/geminiChat.test.ts
+++ b/packages/core/src/core/geminiChat.test.ts
@@ -13,7 +13,7 @@ import type {
 import type { ContentGenerator } from '../core/contentGenerator.js';
 import {
   GeminiChat,
-  EmptyStreamError,
+  InvalidStreamError,
   StreamEventType,
   type StreamEvent,
 } from './geminiChat.js';
@@ -237,7 +237,7 @@ describe('GeminiChat', () => {
             /* consume stream */
           }
         })(),
-      ).rejects.toThrow(EmptyStreamError);
+      ).rejects.toThrow(InvalidStreamError);
     });
 
     it('should succeed if the stream ends with an invalid part but has a finishReason and contained a valid part', async () => {
@@ -501,14 +501,14 @@ describe('GeminiChat', () => {
         'prompt-id-stream-1',
       );
 
-      // 4. Assert: The stream processing should throw an EmptyStreamError.
+      // 4. Assert: The stream processing should throw an InvalidStreamError.
       await expect(
         (async () => {
           for await (const _ of stream) {
             // This loop consumes the stream to trigger the internal logic.
           }
         })(),
-      ).rejects.toThrow(EmptyStreamError);
+      ).rejects.toThrow(InvalidStreamError);
     });
 
     it('should succeed when there is a tool call without finish reason', async () => {
@@ -554,7 +554,7 @@ describe('GeminiChat', () => {
       ).resolves.not.toThrow();
     });
 
-    it('should throw EmptyStreamError when no tool call and no finish reason', async () => {
+    it('should throw InvalidStreamError when no tool call and no finish reason', async () => {
       // Setup: Stream with text but no finish reason and no tool call
       const streamWithoutFinishReason = (async function* () {
         yield {
@@ -586,10 +586,10 @@ describe('GeminiChat', () => {
             // consume stream
           }
         })(),
-      ).rejects.toThrow(EmptyStreamError);
+      ).rejects.toThrow(InvalidStreamError);
     });
 
-    it('should throw EmptyStreamError when no tool call and empty response text', async () => {
+    it('should throw InvalidStreamError when no tool call and empty response text', async () => {
       // Setup: Stream with finish reason but empty response (only thoughts)
       const streamWithEmptyResponse = (async function* () {
         yield {
@@ -621,7 +621,7 @@ describe('GeminiChat', () => {
             // consume stream
           }
         })(),
-      ).rejects.toThrow(EmptyStreamError);
+      ).rejects.toThrow(InvalidStreamError);
     });
 
     it('should succeed when there is finish reason and response text', async () => {
@@ -889,7 +889,7 @@ describe('GeminiChat', () => {
         for await (const _ of stream) {
           // Must loop to trigger the internal logic that throws.
         }
-      }).rejects.toThrow(EmptyStreamError);
+      }).rejects.toThrow(InvalidStreamError);
 
       // Should be called 3 times (initial + 2 retries)
       expect(mockContentGenerator.generateContentStream).toHaveBeenCalledTimes(
diff --git a/packages/core/src/core/geminiChat.ts b/packages/core/src/core/geminiChat.ts
index 77831c574a..8088facb94 100644
--- a/packages/core/src/core/geminiChat.ts
+++ b/packages/core/src/core/geminiChat.ts
@@ -161,13 +161,16 @@ function extractCuratedHistory(comprehensiveHistory: Content[]): Content[] {
 }
 
 /**
- * Custom error to signal that a stream completed without valid content,
+ * Custom error to signal that a stream completed with invalid content,
  * which should trigger a retry.
  */
-export class EmptyStreamError extends Error {
-  constructor(message: string) {
+export class InvalidStreamError extends Error {
+  readonly type: 'NO_FINISH_REASON' | 'NO_RESPONSE_TEXT';
+
+  constructor(message: string, type: 'NO_FINISH_REASON' | 'NO_RESPONSE_TEXT') {
     super(message);
-    this.name = 'EmptyStreamError';
+    this.name = 'InvalidStreamError';
+    this.type = type;
   }
 }
 
@@ -284,7 +287,7 @@ export class GeminiChat {
             break;
           } catch (error) {
             lastError = error;
-            const isContentError = error instanceof EmptyStreamError;
+            const isContentError = error instanceof InvalidStreamError;
 
             if (isContentError) {
               // Check if we have more attempts left.
@@ -293,7 +296,7 @@ export class GeminiChat {
                   self.config,
                   new ContentRetryEvent(
                     attempt,
-                    'EmptyStreamError',
+                    (error as InvalidStreamError).type,
                     INVALID_CONTENT_RETRY_OPTIONS.initialDelayMs,
                   ),
                 );
@@ -312,12 +315,12 @@ export class GeminiChat {
         }
 
         if (lastError) {
-          if (lastError instanceof EmptyStreamError) {
+          if (lastError instanceof InvalidStreamError) {
             logContentRetryFailure(
               self.config,
               new ContentRetryFailureEvent(
                 INVALID_CONTENT_RETRY_OPTIONS.maxAttempts,
-                'EmptyStreamError',
+                (lastError as InvalidStreamError).type,
               ),
             );
           }
@@ -564,9 +567,17 @@ export class GeminiChat {
     // - No finish reason, OR
     // - Empty response text (e.g., only thoughts with no actual content)
     if (!hasToolCall && (!hasFinishReason || !responseText)) {
-      throw new EmptyStreamError(
-        'Model stream ended with an invalid chunk or missing finish reason.',
-      );
+      if (!hasFinishReason) {
+        throw new InvalidStreamError(
+          'Model stream ended without a finish reason.',
+          'NO_FINISH_REASON',
+        );
+      } else {
+        throw new InvalidStreamError(
+          'Model stream ended with empty response text.',
+          'NO_RESPONSE_TEXT',
+        );
+      }
     }
 
     this.history.push({ role: 'model', parts: consolidatedParts });