Unhandled flow fault notifications
Key Takeaway
When a flow element fails and has no fault connector, the flow stops and the running user sees a generic error. Salesforce sends a detailed error email, by default to the admin who last modified the flow.
A fault is "unhandled" when a flow element fails and nothing in the flow catches the error. The error emails and the failed interviews that Salesforce can save are how an app builder finds and fixes flows that break after activation.
What happens when a flow element fails
What happens next depends on whether the failing element has a fault connector.
If the failing element has a fault connector...
The flow runs the elements on the fault path instead, so you can show a user-friendly error message or take an alternate path.
If the failing element has no fault connector...
The fault is unhandled, and the flow stops. The running user sees the generic message "An unhandled fault has occurred in this flow" and is told to contact the system administrator. The user can't continue the flow or go back to an earlier part of it. Salesforce creates a failed interview and sends a detailed error email.
For screen flows, Salesforce also publishes a Flow Execution Error Event platform event message when the flow fails.