How do I debug this?

Questions
1

I have a workflow here and keep getting hit with this error whenever I insert the merge node to combine the inputs before hitting the Google sheets node where I want the AI responses to be in line with the edit fields.

How do I debug this?

Screenshot 2025-06-30 at 7.51.00 PM
Screenshot 2025-06-30 at 7.51.00 PM1930×1168 476 KB

2

Hello @Ahmad_Rasheed,

It turns out this error when adding the Merge node usually means there’s something wrong with the connections or the expected input structure to that node, not that Merge itself is broken.

Check your Merge node and the inputs that it receives. Run the workflow step-by-step with both branches active to confirm Merge receives the expected inputs.

3

Thank you for the response. This error starts as soon as I execute the workflow. The form doesn’t even pop up.

4

When you click “Execute workflow” in n8n, the system doesn’t just run the nodes connected to the trigger, it loads and validates the entire node graph, including all connections, even those that aren’t visibly active. If a node (like a Merge) contains an internal reference to a deleted or corrupted node, n8n will still try to resolve it during the startup phase. If that reference is undefined, the engine can’t build the execution plan and throws an error immediately, even if the node is far down the line or shouldn’t run yet.

This is a known behavior caused by how n8n precompiles the whole workflow before execution begins.

The only reliable fix imo is to recreate the broken node from scratch, as duplicating or editing it will often preserve the corrupted internal reference.

5

Thank you.

I deleted the node, re ran the workflow (sucessfully) and then added the merge node again and still facing the same issue

6

Thanks for trying that! the issue is most likely with how the inputs are connected or with a node before the Merge that’s not resolving properly.

Here’s what I suggest:

  1. Temporarily disconnect one of the inputs to the Merge node (leave only one connected) and run the workflow.
  • If it works: the second input is the problem.
  • If it still fails: the issue is in the first branch or the Merge config itself.
  1. Double-check that both inputs actually return data