A user encountered an issue where a ControlUp workflow, previously used to push alert messages to Google Chat, stopped functioning correctly. The workflow’s start node began reporting a reference to a missing node, a problem not seen before. This issue coincided with the use of output variables in the workflow. Removing these output variables stopped the error messages, though including them had been necessary for the workflow to work previously.
The output variables in ControlUp workflows are primarily designed for use with subflows, where a subflow acts like a function by taking input, processing it, and returning data to the main flow. The output variables specify what data the subflow returns. However, in this case, the workflow was not a subflow, and the user was instructing the workflow to return properties from an event variable that could not be found. This discrepancy caused the workflow to flag missing node references.
A newer validation check within ControlUp appears to verify if workflows reference variables that do not exist. This validation is likely why the error started appearing even though the workflow continued to run and post messages correctly. Before this update, referencing nonexistent variables was silently ignored, causing no breakage. Therefore, although the output variables cause no functional harm in a non-subflow context, they create misleading error states that might confuse anyone reviewing or maintaining the workflow.
The recommended resolution is to delete the output variables whenever the workflow is not a subflow. Removing these output variables prevents confusion and stops error messages related to missing nodes without impacting the workflow’s functionality. Users needing to troubleshoot similar issues should also consider exporting the workflow in JSON format and providing run history details when contacting ControlUp support. For more on ControlUp workflows, output variables, and subflows, refer to the official documentation at https://docs.controlup.com.
Read the entire ‘Understanding and Resolving Missing Node References Caused by Output Variables in ControlUp Workflows’ thread below:
This may be related to the same, but noticing a workflow stopped functioning about the same time.
I have an alert that triggers a workflow to push a message to Google Chat, and now the start node says it references a missing node. It didn’t say that previously
If I remove the output variables the messages go away, but putting them there is what made it work previously.
Please export the flow to json and email to support@controlup.com along with these screenshots
FYI
It would be great if you could also reference a good run ID from Run History
Email is already sent, but 9/29/26 at 9:21:25am, ran for 42 seconds, which seems rather long for what it does, but that did post a good message
Output variables are primarily used with subflows.
IE I have a sub flow that takes a device ID, uses the device ID to add some standard data and returns that to the main flow.
The output variables determine what the main flow gets back from the subflow.
If you consider a workflow a function. Output variables is what gets returned.
You’re telling workflows that you want to return properties of an event variable. But workflows can’t find an event variable.
I believe that check, that makes sure you’re not referencing variables that don’t exist, is new. Hence why this didn’t show up before and still worked.
You were just telling workflows to return nothing. And since this isn’t used as a subflow, it didn’t break anything then nor does it break anything now.
IMO, delete the output variables. Not because there is any functional difference. But because it avoids confusion if/when someone else looks at this and tries to understand why the output variables are there.
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