Fix: Wrap Gemini function response arrays in object to prevent API error (#2745)

extensions/copilot/src/extension/byok/common/geminiMessageConverter.ts

@@ -77,7 +77,7 @@ function apiContentToGeminiContent(content: (LanguageModelTextPart | LanguageMod
 				// Handle case with text content (may also have images)
 				try {
 					responsePayload = JSON.parse(textContent);
-					if (typeof responsePayload !== 'object' || responsePayload === null) {
+					if (typeof responsePayload !== 'object' || responsePayload === null || Array.isArray(responsePayload)) {
 						responsePayload = { result: responsePayload };
 					}
 				} catch {

extensions/copilot/src/extension/byok/common/test/geminiMessageConverter.spec.ts

@@ -102,6 +102,24 @@ describe('GeminiMessageConverter', () => {
 		expect(fr.functionResponse.response).toEqual({ foo: 'bar' });
 	});
 
+	it('should wrap array responses in an object', () => {
+		const toolResult = new LanguageModelToolResultPart('listRepos_12345', [new LanguageModelTextPart('["repo1", "repo2"]')]);
+		const messages: LanguageModelChatMessage[] = [
+			{
+				role: LanguageModelChatMessageRole.Assistant,
+				content: [toolResult],
+				name: undefined
+			}
+		];
+
+		const result = apiMessageToGeminiMessage(messages);
+
+		expect(result.contents).toHaveLength(1);
+		expect(result.contents[0].role).toBe('user');
+		const fr: any = result.contents[0].parts![0];
+		expect(fr.functionResponse.response).toEqual({ result: ['repo1', 'repo2'] });
+	});
+
 	it('should be idempotent when called multiple times (no duplication)', () => {
 		const toolResult = new LanguageModelToolResultPart('doThing_12345', [new LMText('{"value":42}')]);
 		const messages: LanguageModelChatMessage[] = [