Stability AI Stable Diffusion 3.5 - ComfyUI Native Node Documentation

A node that generates high-quality images using Stability AI Stable Diffusion 3.5 model

The Stability AI Stable Diffusion 3.5 Image node uses Stability AI’s Stable Diffusion 3.5 API to generate high-quality images. It supports both text-to-image and image-to-image generation, capable of creating detailed visual content from text prompts.

Parameters

Required Parameters

Parameter	Type	Default	Description
prompt	string	""	What you want to see in the output image. Strong, descriptive prompts that clearly define elements, colors and themes will yield better results
model	select	-	Choose which Stability SD 3.5 model to use
aspect_ratio	select	”1:1”	Width to height ratio of generated image
style_preset	select	”None”	Optional preset style for the desired image
cfg_scale	float	4.0	How strictly the diffusion process adheres to the prompt text (higher values keep your image closer to your prompt). Range: 1.0 - 10.0, Step: 0.1
seed	integer	0	Random seed for noise generation (0-4294967294)

Optional Parameters

Parameter	Type	Default	Description
image	image	-	Input image. When provided, the node switches to image-to-image mode
negative_prompt	string	""	Keywords of what you don’t want to see in the output image. This is an advanced feature
image_denoise	float	0.5	Denoising strength for input image. 0.0 yields image identical to input, 1.0 is as if no image was provided at all. Range: 0.0 - 1.0, Step: 0.01. Only effective when image is provided

Output

Output	Type	Description
IMAGE	image	Generated image

Usage Example

Stability AI Stable Diffusion 3.5 Image Workflow Example

Stability AI Stable Diffusion 3.5 Image Workflow Example

Notes

• When an input image is provided, the node switches from text-to-image mode to image-to-image mode
• In image-to-image mode, aspect ratio parameters are ignored
• Mode selection automatically switches based on whether an image is provided:
  • No image provided: text-to-image mode
  • Image provided: image-to-image mode
• If style_preset is set to “None”, no preset style will be applied

Source Code

[Node source code (Updated on 2025-05-07)]

class StabilityStableImageSD_3_5Node:
    """
    Generates images synchronously based on prompt and resolution.
    """

    RETURN_TYPES = (IO.IMAGE,)
    DESCRIPTION = cleandoc(__doc__ or "")  # Handle potential None value
    FUNCTION = "api_call"
    API_NODE = True
    CATEGORY = "api node/image/Stability AI"

    @classmethod
    def INPUT_TYPES(s):
        return {
            "required": {
                "prompt": (
                    IO.STRING,
                    {
                        "multiline": True,
                        "default": "",
                        "tooltip": "What you wish to see in the output image. A strong, descriptive prompt that clearly defines elements, colors, and subjects will lead to better results."
                    },
                ),
                "model": ([x.value for x in Stability_SD3_5_Model],),
                "aspect_ratio": ([x.value for x in StabilityAspectRatio],
                    {
                        "default": StabilityAspectRatio.ratio_1_1,
                        "tooltip": "Aspect ratio of generated image.",
                    },
                ),
                "style_preset": (get_stability_style_presets(),
                    {
                        "tooltip": "Optional desired style of generated image.",
                    },
                ),
                "cfg_scale": (
                    IO.FLOAT,
                    {
                        "default": 4.0,
                        "min": 1.0,
                        "max": 10.0,
                        "step": 0.1,
                        "tooltip": "How strictly the diffusion process adheres to the prompt text (higher values keep your image closer to your prompt)",
                    },
                ),
                "seed": (
                    IO.INT,
                    {
                        "default": 0,
                        "min": 0,
                        "max": 4294967294,
                        "control_after_generate": True,
                        "tooltip": "The random seed used for creating the noise.",
                    },
                ),
            },
            "optional": {
                "image": (IO.IMAGE,),
                "negative_prompt": (
                    IO.STRING,
                    {
                        "default": "",
                        "forceInput": True,
                        "tooltip": "Keywords of what you do not wish to see in the output image. This is an advanced feature."
                    },
                ),
                "image_denoise": (
                    IO.FLOAT,
                    {
                        "default": 0.5,
                        "min": 0.0,
                        "max": 1.0,
                        "step": 0.01,
                        "tooltip": "Denoise of input image; 0.0 yields image identical to input, 1.0 is as if no image was provided at all.",
                    },
                ),
            },
            "hidden": {
                "auth_token": "AUTH_TOKEN_COMFY_ORG",
            },
        }

    def api_call(self, model: str, prompt: str, aspect_ratio: str, style_preset: str, seed: int, cfg_scale: float,
                 negative_prompt: str=None, image: torch.Tensor = None, image_denoise: float=None,
                 auth_token=None):
        validate_string(prompt, strip_whitespace=False)
        # prepare image binary if image present
        image_binary = None
        mode = Stability_SD3_5_GenerationMode.text_to_image
        if image is not None:
            image_binary = tensor_to_bytesio(image, total_pixels=1504*1504).read()
            mode = Stability_SD3_5_GenerationMode.image_to_image
            aspect_ratio = None
        else:
            image_denoise = None

        if not negative_prompt:
            negative_prompt = None
        if style_preset == "None":
            style_preset = None

        files = {
            "image": image_binary
        }

        operation = SynchronousOperation(
            endpoint=ApiEndpoint(
                path="/proxy/stability/v2beta/stable-image/generate/sd3",
                method=HttpMethod.POST,
                request_model=StabilityStable3_5Request,
                response_model=StabilityStableUltraResponse,
            ),
            request=StabilityStable3_5Request(
                prompt=prompt,
                negative_prompt=negative_prompt,
                aspect_ratio=aspect_ratio,
                seed=seed,
                strength=image_denoise,
                style_preset=style_preset,
                cfg_scale=cfg_scale,
                model=model,
                mode=mode,
            ),
            files=files,
            content_type="multipart/form-data",
            auth_token=auth_token,
        )
        response_api = operation.execute()

        if response_api.finish_reason != "SUCCESS":
            raise Exception(f"Stable Diffusion 3.5 Image generation failed: {response_api.finish_reason}.")

        image_data = base64.b64decode(response_api.image)
        returned_image = bytesio_to_image_tensor(BytesIO(image_data))

        return (returned_image,)