Ideogram 4.5 edit keeps the source shape when aspect_ratio is omitted

Image-to-image calls often get the wrong shape: you send a 4:5 photo and get back a square. The Sume Image API page covers this directly. On edit and image-to-image calls, aspect_ratio: "auto" matches the reference, and omitting the field is not the same as auto.

Ideogram 4.5 is the exception. Sume's API notes say an edit with no aspect_ratio keeps the source geometry, and its descriptor does not list auto at all. Its resolution values, 1K or 2K, combine with an explicit ratio to map to exact sizes.

Which models list auto

From the catalog data in the repo, these ids list auto in their aspect ratio descriptor:

A request that keeps the shape

For Nano Banana 2, pass auto and one reference:

curl -X POST https://api.sume.com/v1/images \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"google/nano-banana-2","prompt":"Brighten the room, keep the layout","aspect_ratio":"auto","input_references":[{"type":"image_url","image_url":{"url":"https://example.com/room.jpg"}}]}'

Failure mode to avoid

Sending auto to a model that does not list it returns 400 unsupported_parameter, not a silent fallback. That makes the mistake easy to catch: the API tells you which parameter the model refuses. Ideogram's own reference docs describe attaching references as turning the prompt into an edit instruction. On Sume, the edit path keeps the source frame when you omit the ratio.

How this was checked

Vendor facts come from the pages listed in the sources, read on 2026-10-05. Sume facts come from the Image API docs and the catalog code on main on the same date. Catalogs and limits change, so read the descriptors from GET /v1/images/models before you pin a number in production code.