StabilityAI Suite - SD3

There's a bitter joke in the history of Stable Diffusion 3: the model the community got to download was the 2B Medium - under-trained, anatomy-broken, promptly written off - while the model Stability actually believed in, the 8B-class thing powering its API, was the one nobody could run locally. This node talks to that API. It's SD3 as it was meant to be used: the hosted model, from inside ComfyUI, in exchange for API credits.

That framing matters for your expectations. If you're judging SD3 from the open Medium's reputation, this is a different experience. And you're a customer of a cloud endpoint, not a licensee of weights - so the license saga and the CivitAI removals that dogged the open family are not your problem here. You just want images.

How it works

A POST to stable-image/generate/sd3 with your prompt and model choice. Two modes: no image connected and it's text-to-image with an aspect_ratio; wire in an image and it becomes image-to-image, controlled by strength (default 0.5 - the same idea as a denoise dial).

Inputs that matter

• model - sd3 or sd3-turbo. Turbo is the distilled, faster variant; plain sd3 for the full-quality pass.
• prompt - required.
• image + strength - add an image to rework it; strength runs 0.01–1, start near 0.5 and nudge up for bigger changes.
• aspect_ratio - nine options, used only in text-to-image mode (it's dropped when an image is attached).
• output_format - png or jpeg. Note: no webp here, unlike the other nodes in the pack.

Output is a single IMAGE.

Install

The usual. ComfyUI Manager → "ComfyUI StabilityAI Suite", or:

cd ComfyUI/custom_nodes
git clone https://github.com/florestefano1975/ComfyUI-StabilityAI-Suite

Restart, key in via env var, sai_platform_key.txt, or api_key_override. No model downloads, no extra pip packages - thin wrapper, like everything in this pack.

Gotchas

• Paid per generation, and turbo exists partly to make the bill smaller.
• The 2B's bad reputation may make you skeptical; give the API model a real try before dismissing the family - the hosted weights were always the better ones.
• If you want open SD3.5 to run locally, this isn't it - this is the hosted convenience path, and the pack never touches local checkpoints.

Where this node fits: quick SD3 tests, one-off generations with zero setup, or a composable step inside a bigger cloud workflow. For everything else, the local ecosystem has moved on - but when you specifically want the SD3 look, this is the honest way to get it.