Same Omni video twice: no seed, but a replay returns it

You cannot reproduce a Gemini Omni Flash clip by setting a seed. Google's Omni page lists no system instructions, temperature, top_p or stop sequences, and Sume's video docs say no v1 model accepts seed: each model reports seed: false and the API rejects the field. What Sume does give you is a replay: send the same Idempotency-Key with the same payload and you get the original job back, not a new generation. Read on 2026-10-08.

So there are two different needs here. If you want the identical file again, replay or re-download. If you want the same clip with one thing changed, use an edit.

Which control exists where

The table separates what a sampling control would do from what each route offers.

Replay without paying twice

Sume's differences table lists idempotency as an addition: send Idempotency-Key to make retries safe, and a replay returns the original job. A key reused for a different payload is a 409 idempotency_conflict, which is the right failure when someone changes the prompt and forgets the key.

One practical rule: build the key from the clip, not the attempt. A key such as spring-hook-03-720p stays stable across crashes. A draft at 360p and a final at 720p need separate keys, since they are different payloads.

Edit instead of re-rolling

Re-rolling an Omni clip to fix one detail usually changes everything else too. Sume's Omni row has an edit mode: send video_url and a prompt such as Replace the bottle with an apple. Keep everything else the same. Resolution is optional and defaults to 720p, and aspect_ratio is not accepted for an edit. Google's page also recommends the phrase Keep everything else the same for targeted edits.

An edit bills output seconds at the same per-second rate. When the caller sends no duration, the reserve assumes 8 seconds: $1.00 at 720p on Sume. Google's direct list is about $0.10 per second at 720p.

What to store

Store the prompt, the resolution, the idempotency key and the job id next to every approved clip. If a client asks for the same clip next month, the file is the answer. A new request is a new roll.

Keeping a result you like

Since you cannot repeat a generation, save the file the first time. Download the result as soon as the job completes and store it with the prompt. For small changes to a clip you like, use edit mode with video_url and a prompt instead of generating again.