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Inbound queue SLA forecast + virtual callback gate

Orbit’s ACD queue entry check forecasts whether the head-of-line (or a new caller’s projected wait) will breach the queue’s SLA threshold — the per-queue target the supervisor surface already shows. When a queue opts the new slaCallbackPolicy field into suggest or block, the engine guards entries accordingly:
  • suggest — entry still allowed; the supervisor surface marks “press 1 for a callback” as advised for this tick.
  • block — the entry check refuses the ZADD and routes the caller to the press-1 virtual-callback consent (position saved; the callback-in-queue dispatcher dials them on the Devotel softswitch, not an outbound Telnyx/DIDWW agent — respect the invariant).

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Fields

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Supervisor verdict

computeSlaCallbackGate returns { verdict, projectedWaitSeconds, breachOverSeconds, alreadyBreached }:
  • verdict: ok, suggest, or block.
  • projectedWaitSeconds: position-based estimate.
  • breachOverSeconds: the deeper of head-of-line overhang vs position math; used to surface “how much capacity callback would absorb”.
  • alreadyBreached: head-of-line already past threshold (a 0-waiting queue can still be flagged).
The supervisor read-model and the request-path entry check use the same engine so the two surfaces cannot drift.

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Entry decision flow

  1. The queue controller fetches getQueueStats + getQueueConfig.
  2. If slaCallbackPolicy is absent → the block check is skipped.
  3. When 'block' and the forecast is a breach → the controller responds 503 with slaCallbackBlocked: true, projectedWaitSecs, slaThresholdSecs and fires handleOverflow(call, 'callback', ...). The caller hears the press-1 prompt and consents a callback whose position is preserved.
  4. Queues without the field engage only the existing press-1 escape — nothing else changes.

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Dispatch safety

The blocked-entry path is the same callback overflow handleOverflow the existing press-1 escape uses, so it lands in the normal callback_requests / callback_in_queue dispatch path. The callback dispatcher enforces:
  • Emergency-dial guard (invariant #49).
  • TCPA federal-window check (invariant #68) for +1 NANP.
  • Devotel softswitch trunk for dialbacks (invariant #45).

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Example PATCH

The queue will now protect every inbound call against accruing hold on an already-breaching queue and steer it to virtual callback instead.