refactor(web): use discriminated union for selectConfiguredLanguageMo…

…del result; askCodebase drops impossible fallback branch
Harsh23Kashyap · Jul 2, 2026 · Jul 2, 2026 · Jul 2, 2026 · Jul 4, 2026 · Jul 5, 2026
commit 392ad3c69a0b7615fefe875fbaa443f6c57f57c6
diff --git a/packages/web/src/ee/features/mcp/askCodebase.ts b/packages/web/src/ee/features/mcp/askCodebase.ts
@@ -72,21 +72,14 @@ export const askCodebase = (params: AskCodebaseParams): Promise<AskCodebaseResul
 
             let languageModelConfig = configuredModels[0];
             if (requestedLanguageModel) {
-                const { languageModelConfig: selectedLanguageModel, error } = selectConfiguredLanguageModel(
+                const result = selectConfiguredLanguageModel(
                     configuredModels,
                     requestedLanguageModel
                 );
-                if (error) {
-                    return error;
+                if (result.error) {
+                    return result.error;
                 }
-                if (!selectedLanguageModel) {
-                    return {
-                        statusCode: StatusCodes.INTERNAL_SERVER_ERROR,
-                        errorCode: ErrorCode.UNEXPECTED_ERROR,
-                        message: "Failed to resolve the requested language model.",
-                    } satisfies ServiceError;
-                }
-                languageModelConfig = selectedLanguageModel;
+                languageModelConfig = result.languageModelConfig;
             }
 
             const { model, providerOptions, temperature } = await getAISDKLanguageModelAndOptions(languageModelConfig);

diff --git a/packages/web/src/ee/features/mcp/selectConfiguredLanguageModel.ts b/packages/web/src/ee/features/mcp/selectConfiguredLanguageModel.ts
@@ -12,10 +12,10 @@ const formatConfiguredLanguageModelLabel = (model: Pick<LanguageModelInfo, 'prov
 export const selectConfiguredLanguageModel = <T extends Pick<LanguageModelInfo, 'provider' | 'model' | 'displayName'>>(
     configuredModels: T[],
     requestedLanguageModel: Pick<LanguageModelInfo, 'provider' | 'model' | 'displayName'>
-): {
-    languageModelConfig?: T;
-    error?: ServiceError;
-} => {
+): (
+    | { languageModelConfig: T; error?: never }
+    | { languageModelConfig?: never; error: ServiceError }
+) => {
     const candidateModels = configuredModels.filter(
         (model) => model.provider === requestedLanguageModel.provider && model.model === requestedLanguageModel.model
     );