Flow variable defined in a parent Mule flow, when the parent calls a child flow using a flow reference, what is the scope and behavior of that variable in the child flow?

• A. The flow variable is accessible in the child flow, can be changed, and changes are seen back in the parent flow
• B. The flow variable remains local to the parent flow and is not visible in the child flow
• C. The flow variable is passed as an immutable copy to the child flow
• D. It becomes read-only when accessed from the child flow

Answer: (A)

Flow variables live on the message and are part of the same message context used across a flow invocation. When the parent flow calls a child flow with a flow reference, the child flow runs in the same message context, so the flow variable defined in the parent is visible inside the child, can be read and modified, and those changes persist back in the parent when control returns. This shared, mutable behavior lets you communicate state between flows without passing separate copies. If you need true isolation, you’d copy the value or store it elsewhere, but by default it’s accessible and mutable across the parent and child.