Understanding boundary events — Handling failures gracefully

Step 2 of 5

Understanding boundary events

A boundary event sits on the edge of a task. It "catches" something that happens during task execution and diverts the flow to a recovery path.

Error boundary (lightning bolt) — catches a thrown BPMN error
Timer boundary (clock) — fires after a timeout (e.g., "if no response in 5 minutes")
Message boundary (envelope) — catches an incoming message during task execution

Interrupting (solid border) — cancels the task and takes the boundary path
Non-interrupting (dashed border) — runs the boundary path *in parallel* without cancelling the task

The boundary event appears as a small circle sitting on the edge of a task:

┌─────────────┐


│ Charge card │
└──────◈──────┘
       │
   ⚡ Error
       │
  Handle failure

> 💡 Boundary events are one of BPMN's most powerful features. They let you model error handling and timeouts visually — exactly where the risk is.

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Tutorial complete!

You finished Handling failures gracefully. Great work — you've learned the fundamentals of BPMN modeling.