Cancel a queued Seedance 2.5 job: it works only before it starts

You can cancel a seedance-2.5 job only while it is still queued. POST /v1/jobs/{id}/cancel succeeds before generation work starts; after that it returns 409 job_generation_already_started with details.cancelable: false, and the job runs to completion. Cancelling a job that is already canceled is idempotent and returns the same job.

The rules come from Sume's Jobs and results docs and Generation admission docs, read 2026-10-02. Seedance 2.5's 4-30 s range is from the Video Router docs.

When is a Seedance 2.5 job still cancelable?

Only while it waits. On a plan whose processing slots are full, new jobs sit in queued until a slot opens, which is the window in which cancel works. The job envelope has a cancelable boolean and a cancel_url, so read those instead of guessing.

Sume does not expose a per-job queue position or an ETA, so you cannot predict how long the window lasts.

What does cancelling do to the bill?

Paid generation reserves the estimated amount when a request is accepted. Successful completion captures it; failed jobs and failed admission release or refund the reservation where applicable. A job you cancel while queued has not started generating, so there is no completed output to capture.

A job that has started keeps running and bills normally, and a client-side timeout does not cancel it. Stopping your poller only stops you watching.

When should I cancel instead of waiting?

Cancel queued work when the prompt was wrong, or when a full queue is blocking a batch. On a Free workspace with 1 processing slot and 5 queued, a bad prompt in the queue costs a slot until it runs; see the Free plan limits. After 429 queue_full, the docs say to cancel queued jobs you no longer need, then retry with the same Idempotency-Key.

Treat a 409 as information, not failure: it means the job is already running, so wait for it and use the clip or discard it.

In practice: submit with mode: "async", keep the job id and cancel_url, and decide quickly. The longer a job waits, the more likely it has moved to processing, at which point cancel is no longer possible and the only choices are to use the clip or ignore it.