Image edit reference limits on Sume: 16 on GPT Image 2.5, 10 elsewhere

Up to 16 reference images on openai/gpt-image-2.5 and its Sunburst variant, 10 on the other edit-capable rows, 5 on ideogram/ideogram-v4.5, and zero on text-only rows. The cap is a catalog value, and a request above it returns 400. Reference URLs must be public HTTPS; Sume rejects localhost, private and non-HTTP URLs before submission.

Per model

From the repo's docs/api/images.md, the public Image API docs and the catalog capability data.

Request shape

Each reference is an object, and the first one is the picture to edit on rows that treat it that way (Ideogram 4.5 does). On edit calls use aspect_ratio: "auto" to match the reference; omitting the field is not the same.

{
  "model": "openai/gpt-image-2.5",
  "prompt": "place the bag from image 1 on the table in image 2",
  "input_references": [
    {"type": "image_url", "image_url": {"url": "https://example.com/bag.png"}},
    {"type": "image_url", "image_url": {"url": "https://example.com/table.jpg"}}
  ],
  "aspect_ratio": "auto"
}

Cost

Reference images add input cost on the token-priced GPT rows. See the rate card for current credits.