Veo 3.1 takes 3 reference images; Omni on Sume takes 10 plus 3 clips

Google's Veo 3.1 page lists up to three reference images as style and content guides (read 2026-10-09). On Sume, gemini-omni-flash-1.1 accepts up to 10 reference images and up to 3 reference clips of 3 seconds each, and it takes no reference audio.

What do the two limits look like side by side?

Google's Omni page lists up to 3 video references of 3 seconds each and says audio references are unsupported. Sume's Video Router docs set the same video limits and the 10-image limit.

How do you point at a reference in the prompt?

On Sume you name each reference by index, from zero, in list order: <IMAGE_REF_0>, <IMAGE_REF_1>, and <VIDEO_REF_0>. In a /v1/videos call, the images go in input_references; on the Video Router wire they go in reference_image_urls and reference_video_urls.

curl -X POST https://api.sume.com/v1/video-router/generate \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: refs-001" \
  -d '{"model":"gemini-omni-flash-1.1","prompt":"<IMAGE_REF_0> walks past <IMAGE_REF_1>, handheld","reference_image_urls":["https://example.com/a.png","https://example.com/b.png"],"duration":6,"resolution":"720p","mode":"async"}'

Does a reference change the price?

Sume bills Omni per output second by resolution, so the 6-second 720p call above is 6 x $0.125 = $0.75, however many images you send. The cap is the thing to watch: an eleventh image is an error, not a charge.

What if you only need Veo?

Sume does not list a Veo id (catalog read 2026-10-09). Google marks the Veo 3.1 preview ids for shutdown on October 22, 2026, with Omni as the named replacement.