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Hear can clean up final English transcripts. Interim partials are never rewritten. Every presentation step is fail-open: a timeout, exception, or lexical-guard miss returns the previous text unchanged.
Hear transcription is English-only. These flags apply on sync (POST /v1/audio/transcriptions), streaming (GET /v1/audio/transcriptions/stream), and async jobs (POST /v1/transcription/jobs).

Flags

numerals is independent of the others. dictation, drop_fillers, and vocabulary are not implied by smart_format.

smart_format

Opt-in. Changes case and punctuation only. Word identity is guarded; if wrapping would add or drop a word, Hear returns the unformatted final.
List commas keep the spoken and. Run-on splits are conservative: they fire only with enough words before a new clause (the meeting/call/order/…, also / anyway / meanwhile, please send/call/…, or a late standalone i). Tag questions use a short closer (right, yeah, okay, isn't it, …). smart_format does not:
  • Invent emails, URLs, or street addresses
  • Expand or rewrite words (threepm stays threepm unless ITN already normalized it)
  • Remove fillers (that is drop_fillers)
  • Honor spoken “period” / “comma” (that is dictation)
  • Format non-English text

dictation

Separate from smart_format. Off by default. On English finals only, these spoken commands become punctuation:
  • period.
  • comma,
  • question mark?
  • new paragraph → a paragraph break
Turn smart_format on as well if you also want sentence capitalization.

drop_fillers

Off by default. Strips filled pauses (um, uh, umm, uhh, er) on English finals. Do not enable on legal or compliance audio by default — those tokens can be evidence.

vocabulary

A per-call phrase list, not a stored project glossary. Max 32 phrases, 64 characters each. Matching is case-insensitive and exact; the transcript is re-cased to the form you sent, and the same list is boosted for this request only.

Phone numbers

NANP grouping lives under numerals / ITN, not smart_format:
9-digit SSN-shaped spans and 16-digit card-shaped spans are never grouped.

Surfaces

Examples

On the stream, render partial greyed and only commit speech_final / final. That is how you get live captions that snap to punctuated text instead of flickering punctuation on every hypothesis. See Stream speech-to-text.

Failure behavior

Formatting is best-effort and fail-open. A timeout, exception, or lexical-guard miss returns the previous final unchanged. dictation and drop_fillers may change word count; when word timestamps cannot be realigned, the transcript still updates and the words array is cleared. Clients should not treat missing punctuation as an API error.

Next steps

Stream speech-to-text

Partials vs finals, commit, and endpointing.

Conversation intelligence

Batch jobs, diarization, and post-call analytics.