Instagram messaging API multiple images: make a set in one call

Instagram's changelog says sending multiple images in a message is out of beta and available to all accounts (entry dated 2026-05-06). To make a set to send, ask Sume's image endpoint for several images in one request with n, then pass the returned media.sume.com URLs to Meta's messaging call. Sume does not send the message.

The changelog gives no per-message image maximum, so this post states none. Sume facts are from the Image API docs, read 2026-10-01.

How many images can one Sume call return?

The docs say you can request up to 10 images per call with n, and that per-model ceilings are lower, so read the n range descriptor from the catalog. The catalog example for bytedance-seed/seedream-4.5 shows a range of 1 to 4, which fits a four-image set.

What does the request look like?

Check the status code before reading the body: 200 is the image response, 202 is a job envelope you poll. Slow settings such as large n are more likely to come back as 202.

const res = await fetch("https://api.sume.com/v1/images", {
  method: "POST",
  headers: {
    Authorization: "Bearer " + process.env.SUME_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    model: "openai/gpt-image-2",
    prompt: "four angles of a ceramic mug on a desk",
    n: 4,
  }),
});
if (res.status !== 200) throw new Error("job envelope, poll status_url");
const { data } = await res.json();
console.log(data.map((img) => img.url));

What comes back for each image?

Which aspect ratio should the set use?

The docs note that 4:5 is Instagram portrait (1080x1350), and the supported ratios vary by model, so check the catalog first. For carousel feed posts, which have their own crop rule, see first image sets the crop ratio. Meta's changelog does not state a ratio for message images.