How can I resolve the 'No binary data set' error when processing PNG images in n8n's ChainLlm node?

Below is some guidance on how to troubleshoot and resolve the error “No binary data set.” as it pertains to the binary input expected by the ChainLlm node.

Understanding the Error

The error is thrown by the node when it does not find the expected binary property on the item. In n8n, binary data is attached to a specific property on the item (for example, under item.binary) and downstream nodes need to access the exact property name. If the binary field isn’t found or if its name isn’t correctly specified, the node will error out.

Points to Check

1. Verify Previous Node Output

   Inspect the output of the node that should be attaching the binary file. Use the “Execute Workflow” feature and check the data in the Output panel. Confirm that the binary property exists (e.g. item.binary.data0, item.binary.image, etc.) and note the exact name.

2. Reference the Correct Binary Property

   When using expressions, make sure you reference the correct path. For example, if your preceding node attaches the image under the binary key data0, then you need to reference it accordingly. Some common reference formats might be:

   • {{ $input.item.binary.data0 }}
   • {{ $json.binary.data0 }}

   If you see that the binary file is stored under a different key (for example, image), then adjust the expression to match (e.g. {{ $input.item.binary.image }}).

3. Check Node Configuration

   The ChainLlm node expecting the binary may also have a dedicated field or option where you define which binary property it should use. If available, set this parameter to the exact property name where your binary file is found.

4. Ensure File Conversion (if needed)

   In cases where the file isn’t already binary or needs conversion (for instance, if you’re taking data from a different source and then converting to a file), verify that the Convert to File node or other binary-capable node is correctly set up. See the n8n documentation on handling binary data for more details.

5. Self-hosted and Environment Variables Check

   Since you’re running n8n on a self-hosted Docker instance with default binary data mode, make sure that you have not disabled reading/writing of binary data via environment variables such as NODES_EXCLUDE. The default binary data handling mode should work, but any misconfiguration could lead to missing binary files.

Next Steps

• Log the Full Structure: Before passing data to the ChainLlm node, insert a Function or Set node to log the full structure of the input item. This helps determine exactly where the binary data lives (and what the key is).

• Adjust Expression: Update the expression used in the ChainLlm or relevant node to reference the correct binary property name.

• Review Workflow: Confirm that the preceding node (which attaches the binary data) is configured correctly. For instance, if you use a Read/Write or Convert to File node, verify that the file is correctly output to the expected binary property.

By checking these points you should be able to resolve the “No binary data set.” error. If after verifying the output structure you are still not finding the binary file, double-check the documentation for the node you’re using (e.g. ChainLlm node in LangChain) to see if there are any specific requirements regarding binary file input.

Let me know if you need further assistance troubleshooting the workflow details!