Ideogram 4.5 transparency claim vs Sume's background field

If you need a transparent PNG on Sume, send background: "transparent" to ChatGPT Image 2.5. Do not send it to Ideogram 4.5. The Higgsfield changelog (read 2026-10-05) lists transparent backgrounds among Ideogram 4.5's features on Sep 30, but Sume's Image API accepts background only on ChatGPT Image 2.5 (both Flare and Sunburst variants). Elsewhere the request comes back as 400 unsupported_parameter.

Claim vs what Sume exposes

The left column is a distributor's feature list. The right column is what the Sume Image API docs say you can send today.

Three ways to get alpha on Sume

Pick the route by what you already have.

• Generate with alpha: ChatGPT Image 2.5 with background: "transparent". The OpenAI guide pairs transparent output with PNG or WebP.
• Generate on another model, then cut out: Sume's background-removal model sume/rmbg-1.0 lists $0.0225 per image.
• Legacy shape: the Image API docs say that for transparent stills on other models, use Image 1.0 with transparency: true. Image 1.0 is retiring and is an alias of Auto, so avoid it in new code.

A transparent request

This asks ChatGPT Image 2.5 for a PNG with a transparent background. The sticker prompt is only an example.

import asyncio, os, httpx

async def main():
    body = {
        "model": "openai/gpt-image-2.5",
        "prompt": "a die-cut sticker of a smiling fox, flat colors",
        "background": "transparent",
        "output_format": "png",
    }
    headers = {"Authorization": f"Bearer {os.environ['SUME_API_KEY']}"}
    async with httpx.AsyncClient(timeout=60) as c:
        r = await c.post("https://api.sume.com/v1/images", headers=headers, json=body)
    print(r.status_code, r.json())

asyncio.run(main())

Which route to pick

If the look has to come from Ideogram 4.5 (text-heavy layouts, for example), generate there and cut out with RMBG, then check the edges at 100 percent on your real background. If any model will do, the single-call alpha on ChatGPT Image 2.5 avoids a second step. We have not measured edge quality for either route. A related recipe covers replacing headline text on a finished Ideogram image, and the edit chain cost post prices repeated passes.

Check the result

Whichever route you use, place the output on a dark and a light background and look at the edges at 100 percent zoom. A transparent PNG that looks clean on white can show a halo on black. Also open the file's channels to confirm there is an alpha channel at all, since a file can be PNG and still be opaque.