How many reference images? 10 on Image 1.0, 16 on GPT Image 2.5

Image 1.0 accepts 1 to 10 reference or edit images in image_urls, and ChatGPT Image 2.5 accepts up to 16 image references on POST /v1/images. A model whose input_references descriptor is min 0, max 0 is text-to-image only and rejects references.

From Sume's Image 1.0 and Image API docs, read 2026-09-30.

What are the limits by route?

Both routes require public HTTPS URLs.

What counts as a valid URL?

Localhost, private-network and non-HTTPS URLs are rejected before submission. If Sume cannot fetch or mirror an input, the job fails with an error such as image_not_fetchable; check the URL is public and returns an image.

How do I send several references?

List them in image_urls on Image 1.0:

curl -X POST https://api.sume.com/v1/image-1.0/generate \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: refs-001" \
  -d '{
    "prompt": "Place the mug from image 1 on the table from image 2",
    "image_urls": [
      "https://media.sume.com/artifacts/artf_demo/mug.png",
      "https://media.sume.com/artifacts/artf_demo/table.png"
    ]
  }'

Which route for many references?

Use POST /v1/images with ChatGPT Image 2.5 when you need more than 10. Read the model's input_references descriptor first, since limits vary by model.

How do I check this myself?

Confirm each URL opens in a private browser window before submitting. The linked docs pages and the catalog endpoint show the current values, and this post reflects them as of 2026-09-30.