prompt action, input field keep showing a red dot even if there is a variable assigned copilot studio

Question

Hi, I'm building a topic flow in Copilot Studio and I'm running into an issue with the Prompt node that I can't seem to resolve.

My flow works like this: a user asks a question, it gets saved as a global variable, then a Generative Answers node uses that variable to search the knowledge base. The result is saved as a global record variable. After that, a action Prompt node should take that result as input, read it, and classify it into one of five statuses.

The problem is that the Prompt node has a required input field and no matter what I do it keeps showing a red dot, as if nothing is connected to it.

I've tried pretty much everything I can think of, refreshing the bindings, deleting and recreating the input, switching the variable from Global to topic scope, changing the variable type from Record to String, using PowerFx formulas to reference it, and reassigning it through the variable picker. Nothing has worked so far.

the Generative Answers node is writing to it correctly. The issue seems to be specifically with how the Prompt node is binding to it.

The variable itself is definitely not empty.

Is there something I'm missing about how input parameters work in Prompt nodes? Or is this a known issue with bindings not persisting correctly after saving?

below more context: the user response is used to do a knowldge search and the result is saved as Result_knowledge_query wich is a record. I want to decide what the status of this result.

When i ask a question i get this error message: "Error Message: The parameter with name 'Document_20input' is required to call the prompt but its value is blank. Error Code: AIModelActionBadRequest Conversation Id: beb3e23c-53b6-4ae7-960a-d4991309bdd6 Time (UTC): 2026-03-10T11:39:49.211Z"

Thanks in advance.

Answer 1

Hi Nathan,

You’re very close — the red dot issue is happening because of an input type mismatch.

Your Prompt input is Document_20input (Any), but you’re passing Global.Result_Kn... which is a record from Generative Answers. In Copilot Studio, this can look mapped in the designer but still be treated as blank at runtime, which is why you get:

The parameter 'Document_20input' is required ... but its value is blank

1. Open your Status Deciding prompt.
2. Remove Document_20input.
3. Create a new required input as Text (for example: knowledgeText).
4. In the topic, map knowledgeText to a text field inside Global.Result_Kn... (not the whole record).
5. Add a quick check before the Prompt node: if text is empty, skip prompt / handle no-result case.
6. Delete and re-add the Prompt node (to clear stale binding), then Save + Publish.

That should remove the red dot behavior and fix the runtime blank-parameter error

Reference docs

• Copilot Studio prompts/tools: https://learn.microsoft.com/en-us/microsoft-copilot-studio/authoring-create-edit-topics
• Copilot Studio variables (types/scope): https://learn.microsoft.com/en-us/microsoft-copilot-studio/authoring-variables
• Power Fx in Copilot Studio: https://learn.microsoft.com/en-us/microsoft-copilot-studio/advanced-power-fx

Thanks,

Karan Shewale.