Comfy-Org/ComfyUI · error · ValueError

Spreading {len(images)} images across the clip needs an expl

Error message

Spreading {len(images)} images across the clip needs an explicit duration: set duration, or place the images yourself with 'at times'.

What it means

The FLUX.3 keyframe node spreads 3+ keyframes evenly between the first and last frame, which requires a known clip length. When duration is 'auto' the API cannot compute even spacing, so the node raises this before uploading anything.

Source

Thrown at comfy_api_nodes/nodes_bfl.py:1333

        keyframes: IO.Autogrow.Type,
        placement: dict,
        aspect_ratio: str,
        duration: str,
        resolution: str,
        generate_audio: bool,
        safety_tolerance: int,
        seed: int,
    ) -> IO.NodeOutput:
        fields = cls.common_fields(prompt, aspect_ratio, duration, resolution, generate_audio, safety_tolerance)
        images = _flux3_collect_images(keyframes, "keyframes")
        if not images:
            raise ValueError("Connect at least one keyframe image.")
        times = None
        if placement["placement"] == "at times":
            times = _flux3_parse_times(placement["times"], len(images), fields["duration"])
        elif len(images) >= 3 and fields["duration"] == "auto":
            # spread images land evenly between the first and last, which needs a known length
            raise ValueError(
                f"Spreading {len(images)} images across the clip needs an explicit duration: "
                "set duration, or place the images yourself with 'at times'."
            )
        urls = await upload_images_to_comfyapi(
            cls, images, max_images=_FLUX3_MAX_IMAGES, wait_label="Uploading keyframes"
        )
        request = Flux3ImageToVideoRequest(
            keyframes=list(zip(times, urls)) if times is not None else urls,
            **fields,
        )
        return await _flux3_execute(cls, request)


class Flux3VideoContinuationNode(Flux3VideoNodeBase):
    RATE_HD = 0.5863
    RATE_FHD = 0.7579

    @classmethod

View on GitHub (pinned to 1c6d8d45b3)

Solutions

1. Set the duration widget to an explicit value (e.g. '5s' or whatever the combo offers) so spread math has a clip length.
2. Or switch placement to 'at times' and give explicit timestamps for each keyframe via _flux3_parse_times.
3. Or reduce to 2 keyframes, which use first/last frame positions and work with 'auto'.

Example fix

// before
placement = {'placement': 'spread', 'times': ''}
duration = 'auto'
// after
placement = {'placement': 'spread', 'times': ''}
duration = '5s'

n = len(collected_keyframes)
if n >= 3 and placement['placement'] != 'at times' and duration == 'auto':
    raise UserError('Set an explicit duration, or use at-times placement, before running.')

When it happens

Trigger: Keyframes Autogrow has >= 3 images, placement mode is the default 'spread', and the duration widget is left on 'auto' (fields['duration'] == 'auto').

Common situations: User chains several keyframes assuming the model picks its own length; duration widget forgotten after copying a 2-keyframe workflow that worked (2 images map to first/last frames and are exempt).

Related errors

• Connect at least one keyframe image.
• One of prompt or structured_prompt is required to be non-emp
• Reference video {i} is too short: {dur:.1f}s. Minimum durati
• Total reference video duration is {total_video_duration:.1f}
• Reference audio {i} is too short: {dur:.1f}s. Minimum durati

AI-assisted analysis of Comfy-Org/ComfyUI@1c6d8d45b3 (2026-08-14). Data as JSON: /api/errors/64e7361f09032d92. Report an issue: GitHub.