Vercel Blob signed URL as a Sume image_url is rejected

Do not pass a Vercel Blob signed URL as a Sume input.image_url. Sume's docs say input URLs must be fetchable public HTTPS URLs and that signed or private URLs are rejected before generation submission. Put the file in a public-access Blob store and pass that URL.

Vercel facts are from its Blob page and changelog entries, read 2026-09-30. Sume facts are from Media inputs.

What is a Blob signed URL?

Per the Vercel changelog (2026-06-02), a signed URL is a scoped URL with an expiry: it covers a single operation (put, get, head, delete), a specific pathname, and a maximum expiry of 7 days, and needs @vercel/blob 2.4.0 or later. Private storage requires an authenticated token to read; public storage is readable by anyone with the URL.

What does Sume check?

Localhost, private-network URLs, non-HTTPS URLs, signed/private URLs and mismatched content types are rejected. The fields include input.image_url for Avatar 1.0 photos, scene.image_url, product_image, and video_url for face swap and captions. There is no separate asset upload step in the public contract, so the URL you pass is the input.

Can I change a private store to public?

No. Vercel says the access mode cannot be changed after the store is created. Since 2026-09-23 you can create as many stores as you need, so create a separate public store for Sume inputs rather than loosening your private one. Only put files there that you are fine making public.

Is there another way to get a public URL?

Any host that serves the file over public HTTPS with the right content type works. See how to get a public URL for an image.