fix: Update BaseChatModel import checks for MistralAI compatibility (#8527)

Signed-off-by: Oleg Ivaniv <me@olegivaniv.com>

packages/@n8n/nodes-langchain/nodes/agents/Agent/agents/ConversationalAgent/execute.ts

@@ -6,24 +6,21 @@ import {
 } from 'n8n-workflow';
 
 import { initializeAgentExecutorWithOptions } from 'langchain/agents';
-import { BaseChatModel } from 'langchain/chat_models/base';
 import type { Tool } from 'langchain/tools';
 import type { BaseChatMemory } from 'langchain/memory';
 import type { BaseOutputParser } from 'langchain/schema/output_parser';
 import { PromptTemplate } from 'langchain/prompts';
 import { CombiningOutputParser } from 'langchain/output_parsers';
+import { isChatInstance } from '../../../../../utils/helpers';
 
 export async function conversationalAgentExecute(
 	this: IExecuteFunctions,
 ): Promise<INodeExecutionData[][]> {
 	this.logger.verbose('Executing Conversational Agent');
 
-	const model = (await this.getInputConnectionData(
-		NodeConnectionType.AiLanguageModel,
-		0,
-	)) as BaseChatModel;
+	const model = await this.getInputConnectionData(NodeConnectionType.AiLanguageModel, 0);
 
-	if (!(model instanceof BaseChatModel)) {
+	if (!isChatInstance(model)) {
 		throw new NodeOperationError(this.getNode(), 'Conversational Agent requires Chat Model');
 	}
 

packages/@n8n/nodes-langchain/nodes/agents/Agent/agents/ReActAgent/execute.ts

@@ -11,7 +11,8 @@ import type { Tool } from 'langchain/tools';
 import type { BaseOutputParser } from 'langchain/schema/output_parser';
 import { PromptTemplate } from 'langchain/prompts';
 import { CombiningOutputParser } from 'langchain/output_parsers';
-import { BaseChatModel } from 'langchain/chat_models/base';
+import type { BaseChatModel } from 'langchain/chat_models/base';
+import { isChatInstance } from '../../../../../utils/helpers';
 
 export async function reActAgentAgentExecute(
 	this: IExecuteFunctions,
@@ -38,7 +39,7 @@ export async function reActAgentAgentExecute(
 	};
 	let agent: ChatAgent | ZeroShotAgent;
 
-	if (model instanceof BaseChatModel) {
+	if (isChatInstance(model)) {
 		agent = ChatAgent.fromLLMAndTools(model, tools, {
 			prefix: options.prefix,
 			suffix: options.suffixChat,

packages/@n8n/nodes-langchain/nodes/chains/ChainLLM/ChainLlm.node.ts

@@ -19,9 +19,10 @@ import {
 import type { BaseOutputParser } from 'langchain/schema/output_parser';
 import { CombiningOutputParser } from 'langchain/output_parsers';
 import { LLMChain } from 'langchain/chains';
-import { BaseChatModel } from 'langchain/chat_models/base';
+import type { BaseChatModel } from 'langchain/chat_models/base';
 import { HumanMessage } from 'langchain/schema';
 import { getTemplateNoticeField } from '../../../utils/sharedFields';
+import { isChatInstance } from '../../../utils/helpers';
 
 interface MessagesTemplate {
 	type: string;
@@ -94,7 +95,7 @@ async function getChainPromptTemplate(
 		partialVariables: formatInstructions ? { formatInstructions } : undefined,
 	});
 
-	if (llm instanceof BaseChatModel) {
+	if (isChatInstance(llm)) {
 		const parsedMessages = await Promise.all(
 			(messages ?? []).map(async (message) => {
 				const messageClass = [

packages/@n8n/nodes-langchain/utils/helpers.ts

@@ -1,4 +1,6 @@
 import type { IExecuteFunctions } from 'n8n-workflow';
+import { BaseChatModel } from 'langchain/chat_models/base';
+import { BaseChatModel as BaseChatModelCore } from '@langchain/core/language_models/chat_models';
 
 export function getMetadataFiltersValues(
 	ctx: IExecuteFunctions,
@@ -14,3 +16,8 @@ export function getMetadataFiltersValues(
 
 	return undefined;
 }
+
+// TODO: Remove this function once langchain package is updated to 0.1.x
+export function isChatInstance(model: any): model is BaseChatModel | BaseChatModelCore {
+	return model instanceof BaseChatModel || model instanceof BaseChatModelCore;
+}

packages/@n8n/nodes-langchain/utils/logWrapper.ts

@@ -27,6 +27,7 @@ import { BaseOutputParser } from 'langchain/schema/output_parser';
 import { isObject } from 'lodash';
 import { N8nJsonLoader } from './N8nJsonLoader';
 import { N8nBinaryLoader } from './N8nBinaryLoader';
+import { isChatInstance } from './helpers';
 
 const errorsMap: { [key: string]: { message: string; description: string } } = {
 	'You exceeded your current quota, please check your plan and billing details.': {
@@ -225,7 +226,7 @@ export function logWrapper(
 			}
 
 			// ========== BaseChatModel ==========
-			if (originalInstance instanceof BaseLLM || originalInstance instanceof BaseChatModel) {
+			if (originalInstance instanceof BaseLLM || isChatInstance(originalInstance)) {
 				if (prop === '_generate' && '_generate' in target) {
 					return async (
 						messages: BaseMessage[] & string[],