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 Introduction One of the most common and dangerous issues in DMN-based systems is a Boolean evaluation error in production . These errors often do not appear in local testing but suddenly break workflows after deployment. Typical symptoms include: DMN decision fails at runtime Process instance stuck or aborted Unexpected false decision output Runtime exceptions like: FEEL evaluation error Boolean expected but got null Cannot coerce value to Boolean This blog explains: What DMN Boolean errors are Why they happen in production Real root causes (from live systems) How to fix and prevent them What Is a DMN Boolean Error? In DMN, Boolean logic is used in: Input Expressions Decision Table conditions Literal Expressions FEEL expressions A Boolean error occurs when: DMN expects true or false But receives null , empty, wrong type, or invalid expression This leads to decision failure or wrong routing in BPMN processes...

 One of the most common Camunda DMN issues seen in production environments is the infamous Boolean evaluation error , where a decision table fails with a message indicating that a condition did not return a Boolean value . This problem often: Does not appear in development Surfaces suddenly after deployment Blocks process execution in production In this blog, we’ll cover: The exact root causes of this issue Why it appears unexpectedly in production Proven fixes used in real projects 🔴 Typical Error Message You may see an error similar to: Cannot evaluate expression: condition expression returns non - Boolean : result has class java.lang.String and not java.lang.Boolean or FEEL expression did not return a Boolean result This usually occurs when: A process reaches a DMN decision task A decision table condition is evaluated Camunda expects true or false , but receives something else 🧠 Root Cause Analysis (Most Important Section) ...