Answer

If the lead answered but the vendor (Vapi/ElevenLabs) rejects or fails the bot's call leg, the lead is not dropped immediately.

The dialer escalates in this order:

Try another Bot Flow: if other active bot flows serve the same group, the dialer immediately re-tries the lead on the next one (up to 3 candidate flows).
Fall back to a human: if all candidates fail and the lead's group has clocked-in human agents, the call is handed to a free human through the normal transfer path (the agent gets a screen-pop, without an AI summary).
Drop: only if no human serves the group either, the call ends and is recorded as an AI drop.

flowchart TD
  F[Vendor call to the bot fails] --> A{Another active Bot Flow serves this group?}
  A -- Yes --> R[Retry the lead on the next Bot Flow]
  A -- No --> B{Clocked-in human in the lead's group?}
  B -- Yes --> T[Connect the lead to a free human]
  B -- No --> D[Call ends - recorded as an AI drop]

Around the individual call, two protection layers react to vendor failures:

Channel quarantine: the single AI agent whose vendor call failed is clocked out for a short grace period and switched to Manual staffing, so the auto-staffer doesn't immediately reuse a bad channel. Switch it back to Auto on the AI Agents page once the vendor is healthy.
Vendor health auto-disable: repeated failures in a short window (by default 5 failed calls within 60 seconds) automatically disable the whole bot flow; if several flows of one engine trip in quick succession, the entire AI Engine is disabled. Its AI agents clock out, the group's AI-qualified leads return to the human pool (Separate mode), and an alert appears on the Realtime page.

Re-enabling is manual, on the AI Engines page - see Vendor health & auto-disable.