The decision rule is straightforward: keep audio ingestion and ticket triage as two contracts, and do not let a transcription provider's readiness decide whether the logistics queue can accept a customer message. A multipart upload can produce a { text } result, but the call must sit behind an availability check. If the speech service is unavailable, preserve the original audio reference and route the ticket for a later transcription attempt or human review.

That boundary matters more than the upload syntax. A missed delivery call can be time-sensitive, while a model handoff is replaceable.

What should the production boundary protect?

For a logistics support system, the critical path is: receive the audio, retain a durable reference to it, ask the speech provider for text, then pass the text to the classifier that decides queue, urgency, and next action. The transcription service owns the audio-to-text step.…