gemini-3.1-flash-image deprecated: Nano Banana 2.1 on Sume

Google's release notes dated October 6, 2026 say Nano Banana 2.1 is generally available and that gemini-3.1-flash-image is now deprecated. If your client still sends that id, plan the swap. On Sume the id to send is nano-banana-2.1 (or google/nano-banana-2.1), and the older Nano Banana 2 strings still run as 2.1.

Sume does not say it accepts gemini-3.1-flash-image. Look the id up in GET /v1/catalog rather than assuming, and expect 404 model_not_found for an id that is not listed.

Prices side by side

The two columns come from different rate cards and should not be compared as a markup. Sume's numbers are the catalog price per image at default options. Google's are its Standard tier from its pricing page, read 2026-10-08.

For 100 images at 1K, that is 100 x $0.10 = $10.00 on Sume and 100 x $0.0336 = $3.36 at Google's Standard rate. At 2K it is 100 x $0.15 = $15.00 against 100 x $0.0504 = $5.04. Google also lists a Batch tier at $0.0168, $0.0252 and $0.0567 per image for 1K, 2K and 4K.

Migration checklist

The code change is small, but the checks are not. Resolution names map directly: both sides list 1K, 2K and 4K. Output ids, aspect ratios and the way you receive the image differ, since Sume returns durable media.sume.com URLs from an async job.

• Replace the model string and resend a single request with mode: "async", then poll the job.
• Send an Idempotency-Key per order so a retry does not create a second paid job.
• Read the result artifacts from the job and use the Sume media URL, not a provider URL.
• Run a 10-image sample and compare quality at 1K before moving a 1,000-image workload.
• Search your repos for the old id. The linked script post shows one way.

When Sume is the wrong choice

If you only need the lowest per-image price and already have a Google key, the Standard and Batch rates above are lower. Sume's reasons to switch are one key, one job model and one webhook scheme across image, video and audio, and the unified queue behavior in the Generation admission page. That trade is yours to make.

Budgeting the swap

Take your monthly image count by size. If you make 2,000 images at 1K and 500 at 2K, the Sume list cost is 2,000 x $0.10 + 500 x $0.15 = $200 + $75 = $275. At Google's Standard rate the same mix is 2,000 x $0.0336 + 500 x $0.0504 = $67.20 + $25.20 = $92.40. The Batch tier would be 2,000 x $0.0168 + 500 x $0.0252 = $33.60 + $12.60 = $46.20.

Those gaps are real, so decide what you are buying. Sume bills the job result and handles the queue, the retry key and the webhook; a direct Google integration does not. Run the arithmetic on your own mix before you decide, and keep the deprecation date on your calendar either way.