Nano Banana 2.1 has no 512px size in Google's guide; Sume lists 512

Google's image generation guide says the 512px (0.5K) resolution works on Gemini 3.1 Flash Image but "not supported on Gemini Nano Banana 2.1". Its pricing page lists a 0.5K price only for the older model, at $0.045. Sume's own catalog code lists 512 as a resolution tier for google/nano-banana-2.1, so the two sources disagree on paper.

What each source says

The table sets the evidence side by side. I tested none of this against a live endpoint, so treat the last row as an open question.

Why Sume's list says 512

The repo comment in Sume's image contract says the enum comes from the provider's resolution option, and a unit test pins the public values to 512, 1K, 2K, 4K. A catalog descriptor tells you what the Sume API accepts at the door. It does not prove that the model renders 512px natively, or that the price is lower at that tier.

How to check before you rely on it

• Send one request at "resolution": "512" and one at "1K", and read the pixel size of each returned file.
• Compare usage.cost on the two responses. If they match, the lower tier saved nothing.
• If you need small drafts from Google directly, use gemini-3.1-flash-image, which Google still lists with 0.5K, and keep in mind it is now deprecated.
• Always use an uppercase K for Google's own tiers. Google says lowercase values are rejected.

Where the descriptor lives

Read GET /v1/images/models/google/nano-banana-2.1/endpoints from the Sume Image API and look at supported_parameters.resolution. Pin the tiers you saw there, not the tiers from a blog post.