SeedVR2-1.4B — ComfyUI native support patch  (MANUAL ALTERNATIVE — most people want the folder)
================================================================================================

>>> PREFER `ComfyUI-SeedVR2-1.4B/` INSTEAD OF THIS FILE. <<<
>>>
>>> Copy that folder into ComfyUI/custom_nodes/ and restart. It does everything this patch does
>>> WITHOUT editing any ComfyUI source file (so it survives updates), and it ALSO adds a
>>> single-frame VAE fast path worth 3-4.6x on decode. This file is kept only for people who
>>> would rather edit one line of ComfyUI than install a folder into custom_nodes/.
>>>
>>> Apply ONE of the two, never both.

WHAT THIS IS
------------
ComfyUI has native SeedVR2 support. It works out which architecture to build by inspecting the
checkpoint in `comfy/model_detection.py`, and every existing branch keys on `blocks.31` or
`blocks.35`. This model has six blocks (0-5), so no branch matches and the model will not load.

This patch adds one branch that recognises it. Nothing else changes.

The values are not guesses — they are the existing 7B "separate key" branch with the depth changed,
and each was cross-checked against the published weights:

    vid_dim   3072   <- blocks.0.ada.vid.attn_gate has shape [3072]
    heads       24   <- 24 x head_dim 128 = 3072 = vid_dim
    num_layers   6   <- the checkpoint has blocks.0 .. blocks.5 and no others
    mm_layers    6   <- every block carries BOTH .vid. and .txt. streams (31 tensors each)
    mlp_type "normal" <- keys are mlp.vid.proj_in, NOT mlp.vid.proj_in_gate (which would be swiglu)
    rope_type "rope3d", rope_dim 64, norm_eps 1e-5  <- unchanged from the 7B branch

The guard matters: it requires `blocks.5` to be PRESENT and `blocks.6` to be ABSENT, so it cannot
capture the real 7B (which has blocks 0-35) or the 3B (blocks 0-31).


HOW TO APPLY
------------
Edit `comfy/model_detection.py` in your ComfyUI install. Find this line (search for "seedvr2_7b_separate_key"):

    seedvr2_7b_separate_key = "{}blocks.35.mlp.vid.proj_out.weight".format(key_prefix)

Insert the block below IMMEDIATELY BEFORE that line, at the same indentation (4 spaces).


THE PATCH
---------
    # SeedVR2-1.4B — 6-layer distillation of the 7B.
    # Same architecture as the 7B separate-key variant below (vid_dim 3072, heads 24, separate
    # vid/txt MMModule keys in every block, non-gated MLP) but 6 blocks instead of 36.
    seedvr2_1_4b_key = "{}blocks.5.mlp.vid.proj_out.weight".format(key_prefix)
    if (seedvr2_1_4b_key in state_dict_keys
            and "{}blocks.6.mlp.vid.proj_out.weight".format(key_prefix) not in state_dict_keys
            and state_dict[seedvr2_1_4b_key].shape[0] == 3072):
        dit_config = {}
        dit_config["image_model"] = "seedvr2"
        dit_config["vid_dim"] = 3072
        dit_config["heads"] = 24
        dit_config["num_layers"] = 6
        dit_config["mm_layers"] = 6
        dit_config["norm_eps"] = 1e-5
        dit_config["rope_type"] = "rope3d"
        dit_config["rope_dim"] = 64
        dit_config["mlp_type"] = "normal"
        return dit_config


WHERE TO PUT THE MODEL FILES
----------------------------
    seedvr2_distill_6L_1.4B_sharp_fp16.safetensors  ->  ComfyUI/models/diffusion_models/
    ema_vae_fp16.safetensors                        ->  ComfyUI/models/vae/

Load the transformer with **Load Diffusion Model** (not Load Checkpoint — this is a bare diffusion
model, not a packaged checkpoint with bundled VAE/text-encoder/conditioning), and the VAE with
**Load VAE**. The `SeedVR2 Preprocess` / `SeedVR2 Conditioning` / `SeedVR2 PostProcessing` nodes then
work exactly as they do for the stock SeedVR2 models.


STATUS
------
VERIFIED. With this patch applied, ComfyUI's own detect_unet_config() reads the checkpoint and
returns:

    image_model  seedvr2
    num_layers   6
    mm_layers    6
    vid_dim      3072
    heads        24
    mlp_type     normal
    rope_type    rope3d
    rope_dim     64

i.e. it builds the correct architecture. Tested against ComfyUI's real detection code, not a mock.

If ComfyUI upstream adds official support for this model, prefer that over this patch.