Unexpected Cannot read properties of undefined (reading 'error') while using a GraphQL node

Questions
1

Describe the problem/error/question

Unexpected Cannot read properties of undefined (reading ‘error’) while using a GraphQL node

What is the error message (if any)?

{
  "errorMessage": "Cannot read properties of undefined (reading 'error')",
  "errorDetails": {},
  "n8nDetails": {
    "n8nVersion": "1.102.4 (Self Hosted)",
    "binaryDataMode": "default",
    "stackTrace": [
      "TypeError: Cannot read properties of undefined (reading 'error')",
      "    at WorkflowExecute.handleNodeErrorOutput (/usr/local/lib/node_modules/n8n/node_modules/.pnpm/n8n-core@file+packages+core_openai@5.8.1_ws@8.17.1_zod@3.25.67_/node_modules/n8n-core/src/execution-engine/workflow-execute.ts:2348:26)",
      "    at /usr/local/lib/node_modules/n8n/node_modules/.pnpm/n8n-core@file+packages+core_openai@5.8.1_ws@8.17.1_zod@3.25.67_/node_modules/n8n-core/src/execution-engine/workflow-execute.ts:1619:15",
      "    at processTicksAndRejections (node:internal/process/task_queues:105:5)",
      "    at /usr/local/lib/node_modules/n8n/node_modules/.pnpm/n8n-core@file+packages+core_openai@5.8.1_ws@8.17.1_zod@3.25.67_/node_modules/n8n-core/src/execution-engine/workflow-execute.ts:2153:11"
    ]
  }
}

Please share your workflow

Github Gist of the workflow : n8n-graphql-workflow.json · GitHub

Share the output returned by the last node

[
  {
    "username": "jane_doe"
  }
]

Information on your n8n setup

# Debug info

## core

- n8nVersion: 1.102.4
- platform: docker (self-hosted)
- nodeJsVersion: 22.17.0
- database: postgres
- executionMode: regular
- concurrency: -1
- license: community
- consumerId: unknown

## storage

- success: all
- error: all
- progress: false
- manual: true
- binaryMode: memory

## pruning

- enabled: true
- maxAge: 336 hours
- maxCount: 10000 executions

## client

- userAgent: mozilla/5.0 (x11; linux x86_64; rv:142.0) gecko/20100101 firefox/142.0
- isTouchDevice: false

Generated at: 2025-09-19T13:42:32.921Z
2

I’ve continue to do some tests after posting.

It seems the problem is linked to having two GraphQL nodes chained, both using a token through an n8n “credential”. It looks like the session is dropped after the first usage, so, to bypass the error, I duplicate my token request before each GraphQL node …

But it’s not very efficient

3

hello @florian_briand

I suppose the GraphQL node doesn’t work with the error branch. Try setting the error behavior to “continue“.