> ## Documentation Index
> Fetch the complete documentation index at: https://docs.aircaps.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Models

> What each model does and when to use it.

## A5S Async v1

`a5s-async-v1` · REST · [batch guide](/guides/async-transcription)

* Recorded audio or video in any common format, from 0.1 s to 10 hours.
* Speaker labels (`speaker_0`, `speaker_1`, …), word timestamps, utterances, SRT/VTT subtitles.
* English only: `language_code` accepts `en` and regional variants (`en-US`, `en-GB`, …); any other value returns `400 unsupported_language`.
* Text is verbatim and lowercase without punctuation; disfluencies ("uh", "um") are kept.
* Typical turnaround: well under a minute for most files once processing starts.

## A5S v2 Streaming

`a5s-v2-streaming` · WebSocket · [streaming guide](/guides/streaming)

* Live 16 kHz mono PCM16 audio in, partial and final text out as people speak.
* Punctuated, cased text. No speaker labels.
* Optional custom vocabulary to bias recognition toward names and terms.
* English only: the start message's `language` accepts `en` and regional variants (`en-US`, `en-GB`, …); any other value is refused with `unsupported_language`.
* Sessions last up to 5 minutes.

## Choosing

| You have | Use |
| - | - |
| Recordings, uploads, meeting files | A5S Async v1 |
| A live microphone or call that needs captions now | A5S v2 Streaming |
| Live audio that later needs speaker labels | Stream for captions, then send the recording to A5S Async v1 |

## Languages

Both models support English today. **Multilingual support is planned and will be available soon.** Accepted codes: `en`, `en-US`, `en-GB`, `en-AU`, `en-CA`, `en-IN`, `en-IE`, `en-NZ`, `en-ZA` (case-insensitive; `_` works too).

## Access

Accounts can use both models by default. An account may be limited to one model. Requests to a model your account can't use return `403 model_access_denied` (streaming: an `error` message with that code, then close code `4403`). `GET /v1/account` shows `enabled` for each model. To get access, [talk to sales](https://research.aircaps.com/contact).

`GET /v1/models` lists the models.


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