Why Are n8n Custom Variables Showing as [undefined] After an Update?

Below is some guidance based on documented behavior with n8n variables.

What’s Happening

n8n processes custom variables at runtime. When a variable exists without an assigned value, n8n replaces its value as undefined. With your workflow suddenly showing [undefined] for all or some variables, it indicates that the variables in question are either missing a value or are not being set before they’re being referenced.

Points to Check

• Variable Definition:
  Open the Variables page in your n8n instance and verify that the keys you are referencing still have the expected values. Remember, custom variables are read-only and must be managed through the UI. Also, verify that the keys adhere to naming requirements (only letters, numbers, and underscores, up to 50 characters).

• Workflow Execution Changes:
  Since your workflow has been running correctly for months, consider whether the update might have reset or changed the values configured for your custom variables. It may be worth reviewing the variable settings in your instance to ensure nothing was inadvertently modified during the update.

• Reference in Expressions:
  Make sure that when you refer to a variable in a Code node or an expression you are using the correct syntax:

  JSCopied
  $vars.<variable-name>

  A small typo or a change in the variable’s key might result in the value being undefined.

Next Steps

1. Verify Variable Values:
   Go to the Variables configuration in the n8n UI and ensure that the expected keys have the correct values assigned.

2. Inspect Workflow References:
   Double-check how the variables are referenced in your workflow schema. Small changes in the update might require you to re-establish any variable assumptions.

3. Test a Minimal Case:
   Try using a simple workflow that solely accesses a custom variable. This can help determine if the issue is isolated to your workflow or if it’s a broader problem with variable handling in the updated instance.

If after these steps the variables remain undefined, consider checking the release notes for the version you updated to, as there may be information regarding changes to variable handling or possible bugs.

This troubleshooting should help pinpoint why your variables show as [undefined] after your recent update.