fix(Mistral Cloud Chat Mode Node): Support JSON response from latest Magistral models (#20853)

package.json

@@ -89,6 +89,7 @@
     ],
     "overrides": {
       "@azure/identity": "^4.3.0",
+      "@mistralai/mistralai": "^1.10.0",
       "@n8n/typeorm>@sentry/node": "catalog:",
       "@types/node": "^20.17.50",
       "axios": "1.12.0",

packages/@n8n/nodes-langchain/nodes/chains/ChainLLM/methods/chainExecutor.ts

@@ -77,6 +77,11 @@ export function getOutputParserForLLM(
 		return new NaiveJsonOutputParser();
 	}
 
+	// For example Mistral's Magistral models (LmChatMistralCloud node)
+	if (llm.metadata?.output_format === 'json') {
+		return new NaiveJsonOutputParser();
+	}
+
 	return new StringOutputParser();
 }
 

packages/@n8n/nodes-langchain/nodes/chains/ChainLLM/test/chainExecutor.test.ts

@@ -76,6 +76,26 @@ describe('chainExecutor', () => {
 			const parser = chainExecutor.getOutputParserForLLM(model as unknown as BaseChatModel);
 			expect(parser).toBeInstanceOf(NaiveJsonOutputParser);
 		});
+
+		it('should return NaiveJsonOutputParser for models with metadata output_format set to json', () => {
+			const model = mock<BaseChatModel>({
+				metadata: {
+					output_format: 'json',
+				},
+			});
+			const parser = chainExecutor.getOutputParserForLLM(model);
+			expect(parser).toBeInstanceOf(NaiveJsonOutputParser);
+		});
+
+		it('should return StringOutputParser for models with metadata output_format not set to json', () => {
+			const model = mock<BaseChatModel>({
+				metadata: {
+					output_format: 'text',
+				},
+			});
+			const parser = chainExecutor.getOutputParserForLLM(model);
+			expect(parser).toBeInstanceOf(StringOutputParser);
+		});
 	});
 
 	describe('NaiveJsonOutputParser', () => {

packages/@n8n/nodes-langchain/nodes/llms/LmChatMistralCloud/LmChatMistralCloud.node.ts

@@ -13,6 +13,8 @@ import { getConnectionHintNoticeField } from '@utils/sharedFields';
 import { makeN8nLlmFailedAttemptHandler } from '../n8nLlmFailedAttemptHandler';
 import { N8nLlmTracing } from '../N8nLlmTracing';
 
+const deprecatedMagistralModelsWithTextOutput = ['magistral-small-2506', 'magistral-medium-2506'];
+
 export class LmChatMistralCloud implements INodeType {
 	description: INodeTypeDescription = {
 		displayName: 'Mistral Cloud Chat Model',
@@ -192,6 +194,9 @@ export class LmChatMistralCloud implements INodeType {
 			...options,
 			callbacks: [new N8nLlmTracing(this)],
 			onFailedAttempt: makeN8nLlmFailedAttemptHandler(this),
+			metadata: {
+				output_format: isModelWithJSONOutput(modelName) ? 'json' : undefined,
+			},
 		});
 
 		return {
@@ -199,3 +204,20 @@ export class LmChatMistralCloud implements INodeType {
 		};
 	}
 }
+
+function isModelWithJSONOutput(modelName: string): boolean {
+	if (!modelName.includes('magistral')) {
+		return false;
+	}
+
+	if (deprecatedMagistralModelsWithTextOutput.includes(modelName)) {
+		// Deprecated Magistral models return text output
+		// Includes <think></think> chunks as part of text content
+		return false;
+	}
+
+	// All future Magistral models will return JSON output
+	// Which include "thinking" json types
+	// https://docs.mistral.ai/capabilities/reasoning/
+	return true;
+}

packages/@n8n/nodes-langchain/package.json

@@ -183,7 +183,7 @@
     "@langchain/google-genai": "0.2.17",
     "@langchain/google-vertexai": "0.2.18",
     "@langchain/groq": "0.2.3",
-    "@langchain/mistralai": "0.2.1",
+    "@langchain/mistralai": "0.2.3",
     "@langchain/mongodb": "^0.1.0",
     "@langchain/ollama": "0.2.3",
     "@langchain/openai": "catalog:",