Nano Banana Pro aspect ratio: auto keeps the reference shape

Set aspect_ratio: "auto" when you edit with reference images and want the output to keep the reference's shape. Freepik's changelog describes this for Nano Banana Pro, and Sume's image docs give the same advice for edits: omitting the field is not the same as auto.

Freepik facts are from its changelog; Sume facts from the image docs, both read 2026-09-30.

What does Freepik say auto does?

The changelog says Nano Banana Pro and Pro Flash now accept auto as an aspect_ratio, which keeps the aspect ratio of the reference images you send. Output is no longer limited to the ten preset ratios: its example is a 900x1050 reference returning a 960x1120 image. Very extreme ratios are approximated to the closest shape the model can produce.

Two limits matter. auto only applies when you send reference images; without them the model picks the ratio itself. And the default stays 1:1, so omitting the field keeps returning squares.

What does Sume's documentation say?

How do I check that Nano Banana Pro accepts auto on Sume?

Read supported_parameters from GET /v1/images/models, or the per-endpoint list at /v1/images/models/{model_id}/endpoints. The docs say to do this before pinning a tier or ratio. This post did not confirm that the Freepik behavior (the exact output size) carries over to Sume, so test one edit and look at the returned dimensions.

What if I need an exact size like 1080x1350?

Do not rely on auto for that. The docs say 4:5 is Instagram portrait, that Banana Pro sends aspect_ratio: "4:5" with a native size around 928x1152 at 1K, and that exact 1080x1350 is a separate post-step. See Nano Banana Pro custom aspect ratio.