Codex 0.158 transparent images vs Sume rmbg_create cutouts
Codex 0.158 can request a transparent-background image directly. When that beats a Sume still plus rmbg_create, and when it does not.
Codex 0.158, released September 28, 2026, added support for explicit transparent-background requests in image generation. If you only need a new sprite or icon on transparency, ask for it directly. If the subject already exists as a frame, a product shot or a Sume still, cut it out instead: Sume's hosted MCP lists rmbg_create for cutouts, and video_frames_create can pull a frame first.
What the changelog says
The Codex changelog lists, for 0.158.0, that image generation now supports explicit transparent background requests. The entry I read does not say which image model or which output formats are involved, so I do not describe quality or edge handling.
What Sume offers
MCP tools and gates groups rmbg_create with the paid image tools (generate_image, image_upscale_create and others) and says cutouts are rmbg_create, not a tool imported from elsewhere. Paid tools need mcp:write or an API key and an idempotency_key; dry_run=true previews cost. Start from the MCP quickstart if Codex is not yet connected to https://mcp.sume.com/mcp.
| Starting point | Better route | Why |
|---|---|---|
| No image yet, need a new asset | Ask Codex for transparency directly | One step, no second paid call |
| Frame inside a Sume video | video_frames_create then rmbg_create | Subject is fixed by the footage |
| Existing product photo | rmbg_create | Preserves the real product |
| Needs a larger size too | Cutout and upscale as separate jobs | Each is its own job with its own id |
Mind the order and the checks
If you use more than one step, treat each as a separate job: submit, store the id, wait, then read the result. Do not chain on a guess about a file URL. The jobs page describes the status values and result reads.
Always look at the edges on a real background before shipping. A transparent PNG that looks clean on white can show a halo on dark, and neither route removes the need to check.
Keep the agent on a leash
Cutouts are cheap compared with video, but a loop is still a loop. Ask Codex to run dry_run=true first on any batch, use a fresh idempotency_key per image, and put the source image URL or asset id in the job notes so a re-run does not need the same guess twice.
Sources
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