feat: enhance error handling for chat

changelogs/fragments/11543.yml

@@ -0,0 +1,2 @@
+feat:
+- Enhance error handling for chat ([#11543](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/11543))

src/plugins/chat/server/routes/ml_routes/generic_ml_router.ts

@@ -14,6 +14,7 @@ import {
   OpenSearchClient,
 } from '../../../../../core/server';
 import { MLAgentRouter } from './ml_agent_router';
+import { MLClientError } from './ml_client_error';
 
 /**
  * Generic ML client detector with caching for performance
@@ -118,6 +119,13 @@ export class GenericMLRouter implements MLAgentRouter {
         context
       );
 
+      if (mlResponse.status && mlResponse.status >= 400) {
+        const mlClientError = new MLClientError(mlResponse.body);
+        mlClientError.statusCode = mlResponse.status;
+        mlClientError.statusText = mlResponse.statusText;
+        throw mlClientError;
+      }
+
       // Handle response based on type
       if (typeof mlResponse === 'object' && 'body' in mlResponse) {
         return typeof mlResponse.body === 'string' ? JSON.parse(mlResponse.body) : mlResponse.body;

src/plugins/chat/server/routes/ml_routes/ml_client_error.ts

@@ -0,0 +1,9 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+export class MLClientError extends Error {
+  public statusCode?: number;
+  public statusText?: string;
+}