Feature Request / Bug Report – Evaluate Business Rule Activity: Collect Hit Policy List Output Not Supported

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Hi Team,

I wanted to raise a limitation we encountered while working with the Evaluate Business Rule activity and DMN files in UiPath Orchestrator.

Issue Summary:
When a DMN file is configured with the Collect hit policy, the Evaluate Business Rule activity does not return all matched results as a list. Instead, it only returns the last matched value, and throws the following warning:

“A previous output value for {output_name} already exists.”

This makes the Collect hit policy essentially unusable within the current activity.

What We Tried:

  1. Changing the output argument type to List(Of String) in the activity’s Arguments panel — not supported, the activity resets it back to a scalar type on refresh.
  2. Calling the Business Rule via Orchestrator’s API directly as an HTTP Request workaround — the evaluation endpoint does not appear to be publicly exposed in Swagger.
  3. Redesigning the DMN with multiple output columns using Unique hit policy — works but is not scalable as new columns are needed for every new rule.
  4. Using the “Any” type in the DMN output column — does not resolve the issue on the UiPath activity side.

Expected Behavior:
When a DMN uses the Collect hit policy, the Evaluate Business Rule activity should return all matched output values as a List, not just the last one.

Requested Improvements:

  1. Update the Evaluate Business Rule activity to natively support List output types for Collect hit policy results.
  2. Expose a public API endpoint in Orchestrator Swagger for evaluating Business Rules programmatically, so developers can handle the response themselves as a workaround.

This is a standard DMN feature and having it unsupported limits the usefulness of the Business Rules capability significantly for real-world use cases.

Thank you for looking into this. Happy to provide the DMN file or workflow screenshots if needed.

Source Issue: Evaluate Business Rule - How to retrieve "Collect" Hit Policy output

Best regards,
Karthik

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