fix(editor): Improve chat error handling (no-changelog)

packages/frontend/@n8n/i18n/src/locales/en.json

@@ -411,7 +411,18 @@
 	"chatHub.message.actions.executionId": "Execution ID",
 	"chatHub.message.edit.cancel": "Cancel",
 	"chatHub.message.edit.send": "Send",
-	"chatHub.message.error.unknown": "Error: Unknown error occurred",
+	"chatHub.message.error.unknown": "Something went wrong. Please try again.",
+	"chatHub.error.payloadTooLarge": "Your message is too large. Try using shorter text or fewer files.",
+	"chatHub.error.badRequest": "Something went wrong with your message. Please try again.",
+	"chatHub.error.forbidden": "You don't have permission to do this. Please check your settings.",
+	"chatHub.error.serverError": "We're having trouble right now. Please try again in a moment.",
+	"chatHub.error.serverErrorWithReason": "Something went wrong: {error}",
+	"chatHub.error.unknown": "Something went wrong. Please try again.",
+	"chatHub.error.noConnection": "Can't connect right now. Check your internet connection and try again.",
+	"chatHub.error.fetchConversationFailed": "Couldn't load this conversation",
+	"chatHub.error.sendMessageFailed": "Couldn't send the message",
+	"chatHub.error.updateModelFailed": "Couldn't change the AI model",
+	"chatHub.error.updateToolsFailed": "Couldn't update tools",
 	"chatHub.models.selector.defaultLabel": "Select model",
 	"chatHub.models.byIdSelector.title": "Choose {provider} model by ID",
 	"chatHub.models.byIdSelector.choose": "Enter model identifier (e.g. \"gpt-4\")",

packages/frontend/@n8n/rest-api-client/src/utils.test.ts

@@ -54,7 +54,7 @@ describe('streamRequest', () => {
 		expect(onErrorMock).not.toHaveBeenCalled();
 	});
 
-	it('should stream error response from the API endpoint', async () => {
+	it('should stream error response with error data from the API endpoint', async () => {
 		const testError = { code: 500, message: 'Error happened' };
 		const encoder = new TextEncoder();
 		const mockResponse = new ReadableStream({
@@ -66,6 +66,8 @@ describe('streamRequest', () => {
 
 		const mockFetch = vi.fn().mockResolvedValue({
 			ok: false,
+			status: 500,
+			statusText: 'Internal Server Error',
 			body: mockResponse,
 		});
 
@@ -98,8 +100,51 @@ describe('streamRequest', () => {
 		});
 
 		expect(onChunkMock).not.toHaveBeenCalled();
+		expect(onDoneMock).not.toHaveBeenCalled();
+		expect(onErrorMock).toHaveBeenCalledExactlyOnceWith(
+			new ResponseError(testError.message, { httpStatusCode: 500 }),
+		);
+	});
+
+	it('should call onError when stream ends immediately with non-ok status and no chunks', async () => {
+		const mockResponse = new ReadableStream({
+			start(controller) {
+				// Empty stream that just closes without sending any chunks
+				controller.close();
+			},
+		});
+
+		const mockFetch = vi.fn().mockResolvedValue({
+			ok: false,
+			status: 403,
+			statusText: 'Forbidden',
+			body: mockResponse,
+		});
+
+		global.fetch = mockFetch;
+
+		const onChunkMock = vi.fn();
+		const onDoneMock = vi.fn();
+		const onErrorMock = vi.fn();
+
+		await streamRequest(
+			{
+				baseUrl: 'https://api.example.com',
+				pushRef: '',
+			},
+			'/data',
+			{ key: 'value' },
+			onChunkMock,
+			onDoneMock,
+			onErrorMock,
+		);
+
+		expect(onChunkMock).not.toHaveBeenCalled();
+		expect(onDoneMock).not.toHaveBeenCalled();
 		expect(onErrorMock).toHaveBeenCalledTimes(1);
-		expect(onErrorMock).toHaveBeenCalledWith(new ResponseError(testError.message));
+		expect(onErrorMock).toHaveBeenCalledExactlyOnceWith(
+			new ResponseError('Forbidden', { httpStatusCode: 403 }),
+		);
 	});
 
 	it('should handle broken stream data', async () => {

packages/frontend/@n8n/rest-api-client/src/utils.ts

@@ -234,6 +234,10 @@ export async function streamRequest<T extends object>(
 	separator = STREAM_SEPARATOR,
 	abortSignal?: AbortSignal,
 ): Promise<void> {
+	let onErrorOnce: ((e: Error) => void) | undefined = (e: Error) => {
+		onErrorOnce = undefined;
+		onError?.(e);
+	};
 	const headers: Record<string, string> = {
 		'browser-id': getBrowserId(),
 		'Content-Type': 'application/json',
@@ -258,7 +262,15 @@ export async function streamRequest<T extends object>(
 			async function readStream() {
 				const { done, value } = await reader.read();
 				if (done) {
-					onDone?.();
+					if (response.ok) {
+						onDone?.();
+					} else {
+						onErrorOnce?.(
+							new ResponseError(response.statusText, {
+								httpStatusCode: response.status,
+							}),
+						);
+					}
 					return;
 				}
 				const chunk = decoder.decode(value);
@@ -286,15 +298,15 @@ export async function streamRequest<T extends object>(
 							} else {
 								// Otherwise, call error callback
 								const message = 'message' in data ? data.message : response.statusText;
-								onError?.(
+								onErrorOnce?.(
 									new ResponseError(String(message), {
 										httpStatusCode: response.status,
 									}),
 								);
 							}
 						} catch (e: unknown) {
 							if (e instanceof Error) {
-								onError?.(e);
+								onErrorOnce?.(e);
 							}
 						}
 					}
@@ -304,11 +316,11 @@ export async function streamRequest<T extends object>(
 
 			// Start reading the stream
 			await readStream();
-		} else if (onError) {
-			onError(new Error(response.statusText));
+		} else if (onErrorOnce) {
+			onErrorOnce(new Error(response.statusText));
 		}
 	} catch (e: unknown) {
 		assert(e instanceof Error);
-		onError?.(e);
+		onErrorOnce?.(e);
 	}
 }

packages/frontend/editor-ui/src/features/ai/chatHub/ChatView.vue

@@ -322,7 +322,7 @@ watch(
 			try {
 				await chatStore.fetchMessages(id);
 			} catch (error) {
-				toast.showError(error, 'Error fetching a conversation');
+				toast.showError(error, i18n.baseText('chatHub.error.fetchConversationFailed'));
 				await router.push({ name: CHAT_VIEW });
 			}
 		}
@@ -469,7 +469,7 @@ async function handleSelectModel(selection: ChatHubConversationModel, displayNam
 		try {
 			await chatStore.updateSessionModel(sessionId.value, selection, agentName);
 		} catch (error) {
-			toast.showError(error, 'Could not update selected model');
+			toast.showError(error, i18n.baseText('chatHub.error.updateModelFailed'));
 		}
 	} else {
 		defaultModel.value = { ...selection, cachedDisplayName: agentName };
@@ -503,7 +503,7 @@ async function handleUpdateTools(newTools: INode[]) {
 		try {
 			await chatStore.updateToolsInSession(sessionId.value, newTools);
 		} catch (error) {
-			toast.showError(error, 'Could not update selected tools');
+			toast.showError(error, i18n.baseText('chatHub.error.updateToolsFailed'));
 		}
 	}
 }

packages/frontend/editor-ui/src/features/ai/chatHub/chat.store.ts

@@ -2,6 +2,7 @@ import { defineStore } from 'pinia';
 import { CHAT_STORE } from './constants';
 import { computed, ref } from 'vue';
 import { v4 as uuidv4 } from 'uuid';
+import { useI18n } from '@n8n/i18n';
 import {
 	fetchChatModelsApi,
 	sendMessageApi,
@@ -58,11 +59,13 @@ import { useTelemetry } from '@/app/composables/useTelemetry';
 import { deepCopy, type INode } from 'n8n-workflow';
 import type { ChatHubLLMProvider, ChatProviderSettingsDto } from '@n8n/api-types';
 import { convertFileToBinaryData } from '@/app/utils/fileUtils';
+import { ResponseError } from '@n8n/rest-api-client';
 
 export const useChatStore = defineStore(CHAT_STORE, () => {
 	const rootStore = useRootStore();
 	const toast = useToast();
 	const telemetry = useTelemetry();
+	const i18n = useI18n();
 
 	const agents = ref<ChatModelsResponse>();
 	const customAgents = ref<Partial<Record<string, ChatHubAgentDto>>>({});
@@ -455,24 +458,36 @@ export const useChatStore = defineStore(CHAT_STORE, () => {
 			return;
 		}
 
-		toast.showError(error, 'Could not send message');
+		const cause =
+			error instanceof ResponseError
+				? new Error(getErrorMessageByStatusCode(error.httpStatusCode, error.message))
+				: error.message.includes('Failed to fetch')
+					? new Error(i18n.baseText('chatHub.error.noConnection'))
+					: error;
 
-		const { sessionId } = streaming.value;
+		toast.showError(cause, i18n.baseText('chatHub.error.sendMessageFailed'));
 
 		streaming.value = undefined;
+	}
 
-		const conversation = getConversation(sessionId);
-		if (!conversation) {
-			return;
-		}
+	function getErrorMessageByStatusCode(
+		statusCode: number | undefined,
+		message: string | undefined,
+	): string {
+		const errorMessages: Record<number, string> = {
+			[413]: i18n.baseText('chatHub.error.payloadTooLarge'),
+			[400]: i18n.baseText('chatHub.error.badRequest'),
+			[403]: i18n.baseText('chatHub.error.forbidden'),
+			[500]: message
+				? i18n.baseText('chatHub.error.serverErrorWithReason', {
+						interpolate: { error: message },
+					})
+				: i18n.baseText('chatHub.error.serverError'),
+		};
 
-		// TODO: Not sure if we want to mark all running messages as errored?
-		for (const messageId of conversation.activeMessageChain) {
-			const message = conversation.messages[messageId];
-			if (message.status === 'running') {
-				updateMessage(sessionId, messageId, 'error');
-			}
-		}
+		return (
+			(statusCode && errorMessages[statusCode]) || message || i18n.baseText('chatHub.error.unknown')
+		);
 	}
 
 	async function sendMessage(