Async jobs: why video APIs answer later
An asynchronous job is a request that returns an ID straight away and finishes later, the usual shape of a video generation API because renders take minutes. From 3 source pages, read 2026-09-25; no maker pays to be listed.
LTX offers a sync endpoint for quick clips and an async job API for production work, both returning an MP4. Descript's API jobs are polled by ID or answered at a callback URL, and fal queues requests that are polled or answered by webhook.
The ID is the thread that ties a request to its result, so it belongs in the pipeline's log.
Async jobs can outlive the process that started them; a restart should look up open IDs rather than start new renders.
Most tools in the register with an API use this shape, even where the introductory page does not say so.
A job that fails still has an ID and a status, which is where the reason for the failure is found.
| Tool | Hook | What the documentation says |
|---|---|---|
| LTX | Formats | An MP4 returned by the API, from a sync or an async endpoint |
| Descript | Webhooks | A job status to poll, or a callback URL that receives the result |
| fal | Webhooks | Queued requests that are polled or answered by webhook |
Inclusion rule. Readings from the register used on this page. Order. The order the text takes them in.
1As the documentation puts it
The API returns an MP4.
LTX, API page
or pass a callback_url and Descript will POST the same payload when the job finishes
Descript, help centre: Descript API
poll for status or receive results via webhook
fal, documentation: Model APIs
- Quick startAn MP4 returned by the API, from a sync or an async endpoint
- JobsA job status to poll, or a callback URL that receives the result
- Inference methodsQueued requests that are polled or answered by webhook
2Where a drama generator fits
Read against “Async job”, this is how SceneMixer describes the matching stage of its own pipeline:
A script is read once per project; switching affects later tasks such as a storyboard.
SceneMixer, Doubao Seed 2.1 Pro — “Does Pro re-read my script?” (read 2026-10-13)
It is the reference every later segment points at, which is what keeps a character's face and a location consistent across an episode.
SceneMixer, Glossary — “What is a setup image for?” (read 2026-10-13)