Encountering 'Unknown top-level item key:' Error in n8n Sub-Workflow Pagination After Update

Below is some background and guidance based on n8n’s current docs and best practices:

What Changed?

In earlier versions the execution context in sub-workflows may have implicitly allowed access to all items processed across iterations. With version 1.76.3 the context is now handled more strictly. In your sub-workflow the call to

JSCopied
const items = await getItems();

now only returns the items for the current iteration (or may not work as expected at all) rather than aggregating items across your IF loop. This change was introduced as part of overall improvements to how n8n manages execution contexts and looping.

How to Retrieve All Items Across Iterations

While pagination can indeed be handled within the HTTP Request node, if you prefer to combine results from all iterations (e.g. from the “Returns Product Information” node), consider these approaches:

1. Use the Loop Over Items (Split In Batches) Node:
   Instead of manually handling aggregation with a function call, the Loop Over Items node is designed to let you process batches and then automatically aggregates the data when the looping finishes. This node saves the original incoming data and, once looping is complete, delivers a combined output via its done output.

2. Restructure Your Workflow:
   Rework your sub-workflow so that each iteration outputs its result to a common downstream node (for example, a Merge or an Append node), so that when looping or paging is finished you have a final aggregated output. This design adheres to the current execution model in which each node call deals with the items it processes alone.

Why It Doesn’t Work Anymore

The internal context handling around functions like getItems has been updated. Right now, sub-workflows and IF nodes no longer automatically combine all items across iterations as they might have previously. This tighter control helps ensure that nodes (including HTTP Request) behave consistently especially when handling paginated APIs. If you want to aggregate, you now need to use the dedicated mechanisms (like Loop Over Items) or explicitly combine items via workflow design.

Recommended Steps

• Replace your current manual approach (using getItems) with the use of the Loop Over Items node so that each batch is processed properly and then merged at the end.
• Or, redesign your workflow so that each iteration’s result is forwarded to nodes that perform merging/aggregation before you use the aggregated data further.

For more details on looping and handling batching, please refer to the n8n documentation on [Looping in n8n] and [Loop Over Items]. These sections explain how n8n now expects you to architect workflows that require iteration over many items.

I hope this helps clarify why your code is no longer working and how you can adjust your workflow for the updated version!