Fix: Remove unavailable Gemini model and improve error handling

- Remove gemini-2.5-pro-exp-03-25 from default models list (not available in API v1beta)
- Update fallback logic to use gemini-2.5-pro-preview-05-06 instead
- Add specific error handling for 404/model not found errors with clearer messages
- Prevents repeated 404 errors when model router selects unavailable models

Author: Tajudeen

src/vs/workbench/contrib/cortexide/common/modelCapabilities.ts

@@ -101,7 +101,7 @@ export const defaultModelsOfProvider = {
 		'grok-3-mini-fast'
 	],
 	gemini: [ // https://ai.google.dev/gemini-api/docs/models/gemini
-		'gemini-2.5-pro-exp-03-25',
+		// 'gemini-2.5-pro-exp-03-25', // Not available in API v1beta
 		'gemini-2.5-flash-preview-04-17',
 		'gemini-2.0-flash',
 		'gemini-2.0-flash-lite',
@@ -416,7 +416,7 @@ const extensiveModelOptionsFallback: VoidStaticProviderInfo['modelOptionsFallbac
 		};
 	};
 
-	if (lower.includes('gemini') && (lower.includes('2.5') || lower.includes('2-5'))) { return toFallback(geminiModelOptions, 'gemini-2.5-pro-exp-03-25'); }
+	if (lower.includes('gemini') && (lower.includes('2.5') || lower.includes('2-5'))) { return toFallback(geminiModelOptions, 'gemini-2.5-pro-preview-05-06'); }
 
 	if (lower.includes('claude-3-5') || lower.includes('claude-3.5')) { return toFallback(anthropicModelOptions, 'claude-3-5-sonnet-20241022'); }
 	if (lower.includes('claude')) { return toFallback(anthropicModelOptions, 'claude-3-7-sonnet-20250219'); }

src/vs/workbench/contrib/cortexide/electron-main/llmMessage/sendLLMMessage.impl.ts

@@ -982,6 +982,11 @@ const sendGeminiChat = async ({
 				else if (error?.message?.includes('429')) {
 					onError({ message: 'Rate limit reached. ' + error, fullError: error });
 				}
+				else if (error?.message?.includes('404') || error?.message?.includes('NOT_FOUND') || error?.message?.includes('is not found')) {
+					// Model not found - provide helpful error message
+					const modelNotFoundMessage = `Model "${modelName}" is not available. The model may have been deprecated or is not supported in the current API version. Please try a different model.`;
+					onError({ message: modelNotFoundMessage, fullError: error });
+				}
 				else
 					onError({ message: error + '', fullError: error });
 			}