Add a boundary event to the sub-process

Sub-processes support boundary events just like regular tasks. If *anything* inside the sub-process fails, the boundary event catches it and routes to a recovery path — cancelling the entire sub-process cleanly.

This is much more powerful than handling errors inside: one boundary event on the sub-process replaces four individual error handlers on each internal task.

What to do

• Hover over the sub-process boundary (the outer edge of the sub-process box)
• Click the error boundary event icon that appears (lightning bolt)
• The boundary event attaches to the outer edge of the sub-process
• Connect it to a new task: "Escalate claim"

> 💡 Sub-process error boundary events catch any unhandled BPMN error thrown inside — from any task at any nesting level. One boundary event protects the whole group.