fix: relax chunk validation to avoid unnecessary retry

packages/core/src/core/geminiChat.ts

@@ -50,9 +50,13 @@ const INVALID_CONTENT_RETRY_OPTIONS: ContentRetryOptions = {
 };
 /**
  * Returns true if the response is valid, false otherwise.
+ *
+ * The DashScope provider may return the last 2 chunks as:
+ * 1. A choice(candidate) with finishReason and empty content
+ * 2. Empty choices with usage metadata
+ * We'll check separately for both of these cases.
  */
 function isValidResponse(response: GenerateContentResponse): boolean {
-  // The Dashscope provider returns empty content with usage metadata at the end of the stream
   if (response.usageMetadata) {
     return true;
   }
@@ -61,6 +65,10 @@ function isValidResponse(response: GenerateContentResponse): boolean {
     return false;
   }
 
+  if (response.candidates.some((candidate) => candidate.finishReason)) {
+    return true;
+  }
+
   const content = response.candidates[0]?.content;
   return content !== undefined && isValidContent(content);
 }

packages/core/src/core/openaiContentGenerator/converter.ts

@@ -18,6 +18,7 @@ import {
   ContentListUnion,
   ContentUnion,
   PartUnion,
+  Candidate,
 } from '@google/genai';
 import OpenAI from 'openai';
 import { safeJsonParse } from '../../utils/safeJsonParse.js';
@@ -652,19 +653,21 @@ export class OpenAIContentConverter {
         this.streamingToolCallParser.reset();
       }
 
-      response.candidates = [
-        {
-          content: {
-            parts,
-            role: 'model' as const,
-          },
-          finishReason: choice.finish_reason
-            ? this.mapOpenAIFinishReasonToGemini(choice.finish_reason)
-            : FinishReason.FINISH_REASON_UNSPECIFIED,
-          index: 0,
-          safetyRatings: [],
+      // Only include finishReason key if finish_reason is present
+      const candidate: Candidate = {
+        content: {
+          parts,
+          role: 'model' as const,
         },
-      ];
+        index: 0,
+        safetyRatings: [],
+      };
+      if (choice.finish_reason) {
+        candidate.finishReason = this.mapOpenAIFinishReasonToGemini(
+          choice.finish_reason,
+        );
+      }
+      response.candidates = [candidate];
     } else {
       response.candidates = [];
     }

packages/core/src/core/openaiContentGenerator/pipeline.ts

@@ -119,6 +119,7 @@ export class ContentGenerationPipeline {
         // Stage 2b: Filter empty responses to avoid downstream issues
         if (
           response.candidates?.[0]?.content?.parts?.length === 0 &&
+          !response.candidates?.[0]?.finishReason &&
           !response.usageMetadata
         ) {
           continue;