n8n Live Workflow Fails with 400 Bad Request Due to Invalid JSON Payload to OpenAI API

I'm encountering an issue with an n8n workflow running live via a WebHook. In test mode everything works fine, but when the workflow is triggered live, it fails with a 400 error indicating an invalid JSON payload. The error message from the OpenAI API is as follows:

JSONCopied
{  
  “errorMessage”: “Bad request - please check your parameters”,  
  “errorDescription”: “We could not parse the JSON body of your request. (HINT: This likely means you aren’t using your HTTP library correctly. The OpenAI API expects a JSON payload, but what was sent was not valid JSON. If you have trouble figuring out how to fix this, please contact us through our help center at [help.openai.com](http://help.openai.com).)”,  
  “errorDetails”: {},  
  “n8nDetails”: {  
    “time”: “2/5/2025, 10:09:57 AM”,  
    “n8nVersion”: “1.76.2 (Self Hosted)”,  
    “binaryDataMode”: “default”,  
    “cause”: {  
      “status”: 400,  
      “headers”: {  
        “alt-svc”: “h3=\":443\"; ma=86400”,  
        “cf-cache-status”: “DYNAMIC”,  
        “cf-ray”: “90d482d6a9f4ebed-SJC”,  
        “connection”: “keep-alive”,  
        “content-length”: “443”,  
        “content-type”: “application/json; charset=utf-8”,  
        “date”: “Wed, 05 Feb 2025 17:09:57 GMT”,  
        “server”: “cloudflare”,  
        “set-cookie”: “__cf_bm=JGfwy1fwj2WtUw8kFKT_91UY27XiWd05EQT4J6TEhVs-1738775397-1.0.1.1-Ds28tL59SaY4Yg3bvJ.SPYVt2aOVCofRlL4avtuI.oPlWrcAbdKg77kf2TfTyTlhFybbmM6oV4XibiuFVY.uOw; path=/; expires=Wed, 05-Feb-25 17:39:57 GMT; [domain=.api.openai.com](http://domain=.api.openai.com); HttpOnly; Secure; SameSite=None, _cfuvid=knWkElZNHUao4JW_pZo_uM3aBpXmlcZ8dU7_0nky5Jk-1738775397017-0.0.1.1-604800000; path=/; [domain=.api.openai.com](http://domain=.api.openai.com); HttpOnly; Secure; SameSite=None”,  
        “strict-transport-security”: “max-age=31536000; includeSubDomains; preload”,  
        “vary”: “Origin”,  
        “x-content-type-options”: “nosniff”,  
        “x-request-id”: “req_0e94df1c9b6a8afa43d98799f22efada”  
      },  
      “request_id”: “req_0e94df1c9b6a8afa43d98799f22efada”,  
      “error”: {  
        “message”: “We could not parse the JSON body of your request. (HINT: This likely means you aren’t using your HTTP library correctly. The OpenAI API expects a JSON payload, but what was sent was not valid JSON. If you have trouble figuring out how to fix this, please contact us through our help center at [help.openai.com](http://help.openai.com).)”,  
        “type”: “invalid_request_error”,  
        “param”: null,  
        “code”: null  
      },  
      “code”: null,  
      “param”: null,  
      “type”: “invalid_request_error”,  
      “attemptNumber”: 1,  
      “retriesLeft”: 2  
    }  
  }  
}

This problem appears to occur because the JSON payload sent in live mode isn't properly formatted or encoded. I've included my workflow details below, along with screenshots and code snippets to illustrate how the payload is constructed and sent:

Screenshot of the workflow setup:
[](https://private-user-images.githubusercontent.com/33808039/410102222-80f704e7-6a7a-4d03-a6f5-5985077da2f3.png?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.MQ4XLoHkJYNAMhtG41MnBf9jgxJEWsSx5Tki-cSxswE

The key parts of my workflow include the following nodes:

JSONCopied
{  
“nodes”: [  
  {  
    “parameters”: {  
      “promptType”: “define”,  
      “text”: “=Name of the Book: {{ $json[‘Idea (from Book)’][0] }}\nThe research data you need for the book: {{ $json[‘Research (from Book)’][0] }}\n\n=== CHAPTER ====\nName of the chapter: {{ $json[‘Chapter Name’] }}\n\nResearch about the chapter: {{ $json.Research }}\n\n========= PERFECT NOW WRITE THE CONTENT FOR THE CHAPTER\n”,  
      “options”: {  
        “systemMessage”: “=You’re a world class book writer with half a century of experience weaving words that connects with people, you’ll be given specific tasks to write chapters for books, you’ll be given research and the idea, description of the chapter, and you’ll have to comeup with the adecuate anount of content necesary to sake the chapter gold, you*ll filter through all the information and will write the chapter as it connects.\n\nWrite the content in markdown, It’s should be a long chapter and you’ll have to do your word magic to write the chapter in this book.”  
      }  
    },  
    “type”: “[@n8n](/u/n8n)/n8n-nodes-langchain.agent”,  
    “typeVersion”: 1.7,  
    “position”: [  
      740,  
      580  
    ],  
    “id”: “1e05e577-248e-4229-8a7b-4a2447da868f”,  
    “name”: “AI Agent2”  
  }  
],  
“connections”: {  
  “AI Agent2”: {  
    “main”: [      
  
    ]  
  }  
},  
“pinData”: {},  
“meta”: {  
  “templateCredsSetupCompleted”: true,  
  “instanceId”: “dad6575cdc9fb918369bf30cc4905e540fd7e5a48ee08d02082f1e7d7a2abd1c”  
 }  
}

and

JSONCopied
{  
“nodes”: [  
  {  
    “parameters”: {  
      “model”: {  
        “__rl”: true,  
        “value”: “gpt-4o”,  
        “mode”: “list”,  
        “cachedResultName”: “gpt-4o”  
      },  
      “options”: {}  
    },  
    “type”: “[@n8n](/u/n8n)/n8n-nodes-langchain.lmChatOpenAi”,  
    “typeVersion”: 1.2,  
    “position”: [  
      340,  
      780  
    ],  
    “id”: “cd5f4690-5a64-41ba-9329-6f3b7faf692f”,  
    “name”: “ChatGPT LGE”,  
    “credentials”: {  
      “openAiApi”: {  
        “id”: “lMR6ozBbqztOHaBi”,  
        “name”: “OpenAi V2 - LGE”  
      }  
    }  
  }  
],  
“connections”: {  
  “ChatGPT LGE”: {  
    “ai_languageModel”: [      
  
    ]  
  }  
},  
“pinData”: {},  
“meta”: {  
  “templateCredsSetupCompleted”: true,  
  “instanceId”: “dad6575cdc9fb918369bf30cc4905e540fd7e5a48ee08d02082f1e7d7a2abd1c”  
 }  
}

The logs also show that the error is consistent with the behavior seen in live mode running on Railway.com with n8n Version 1.76.3 on Linux and a Postgres database. My current approach suggests checking that the payload is correctly formatted and that the HTTP library properly stringifies the JSON data before sending it. Any additional insights or suggestions to resolve this issue would be greatly appreciated.