ModelMergeSD35_Large_motorway_edition

SD3.5 Large was Stability's serious SD3 push - the model that fixed a lot of what 3.0 got wrong - and its MMDiT is bigger than the 2B's. ModelMergeSD35_Large is ComfyUI's per-block merge node for it, and this is its Motorway-ed clone. If you're merging SD3.5 Large checkpoints, this is the tool, and it's the same shape as the SD3 2B node with more blocks.

The layout

• pos_embed - positional embedding for image tokens.
• x_embedder - the image-latent input projection.
• context_embedder - text-token conditioning projection.
• y_embedder - the pooled-text/CLIP conditioning path.
• t_embedder - timestep conditioning.
• joint_blocks.0–joint_blocks.37 - 38 joint blocks where image and text tokens attend together; the bulk of the model. Early blocks carry structure and cross-modal semantics, late blocks carry detail and finish.
• final_layer - the output projection.

The family gotcha, one more time: all ratios default to 1.0, so an untouched node returns model2. The working recipe is the same as every per-block merge - choose a base blend for all the floats, sample, then raise or lower the regions that matter (embedders for prompt adherence, late joint_blocks for detail).

SD3.5 Large is the one member of the SD3 family with a real checkpoint ecosystem, which makes its merge node genuinely usable rather than academic. The KB's merge framing applies: per-block merging is how you steer which parent's strength shows up where, at the cost of some consistency. If you're blending two 3.5 Large checkpoints to trade prompt-following for aesthetic or vice versa, the embedders (context_embedder, y_embedder) are where you'll feel that trade.

The inputs

• INPUT_model1_key (default model1) and INPUT_model2_key (default model2) - the two SD3.5 Large models.
• The block ratios, each 0.0–1.0, step 0.01, default 1.0.
• OUTPUT_MODEL_key (default MODEL) - where the merged model lands.

The wrapper keeps every ratio as a widget, turns the models into key strings, and keyed-writes the result. Runtime behavior matches stock ModelMergeSD35_Large.

Install

One install for the whole pack. ComfyUI Manager, search "ComfyUI_agilly1989_motorway", or:

cd ComfyUI/custom_nodes
git clone https://github.com/agilly1989/ComfyUI_agilly1989_motorway

Restart ComfyUI. No requirements.txt, no model downloads.

Troubleshooting

• Result is pure model2? All ratios default to 1.0 - set a base blend first.
• Use ModelMergeSD3_2B for SD3 2B weights - that variant has 24 joint blocks, not 38, and the layouts don't swap.
• Merge SD3.5 Large with SD3.5 Large. Different architectures have different block names; the ratios won't mean anything across families.
• 'MotorwayClass' object has no attribute 'hash_' = a model key isn't in the Motorway; check the loaders ran and the key spelling matches (case-sensitive).
• Pack caveats: BETA, and the newest published version (1.1.7) disabled clone generation, so on a fresh install these _motorway_edition nodes may be missing from the menu. They're present in the 1.1.0–1.1.6 builds comfy.icu indexed.