C2PA inputTo records prompts and seeds; Sume video has no seed

The C2PA implementation guide names inputTo ingredient assertions as the place to record inputs to a generation: prompts, reference images, seed values and parameters. On Sume you can record the prompt, the reference URLs and the model id, but not a seed, because the Sume docs say no v1 video model accepts seed.

What C2PA asks for

The guidance says prompt and model information can be recorded as ingredient assertions. The implementation guide extends that to reference images, seeds and parameters. These records make a generation more auditable, since a reviewer sees what went in.

Replace the seed with a replay record

Without a seed you cannot promise the same pixels twice. What you can keep is the request body and the result. Submits require an Idempotency-Key, which means a retry of the same key maps to the same job, not a second generation.

Store the key with the request body. Re-sending the same key is a retry of that job, not a re-roll.

Billing note

Every video model bills at provider list times 1.25, reserved on submit. A re-roll is a new paid job, so keeping the approved job id is cheaper than regenerating to prove a point. See video models.