ModelMergeSD3_2B_motorway_edition

Stable Diffusion 3 swapped the U-Net for an MMDiT - a transformer where text and image tokens run through the same blocks - and its merge node reflects that: there's no input/middle/output split, just embedders plus a run of joint_blocks. ModelMergeSD3_2B is ComfyUI's per-block merge for the 2B variant, and this is its Motorway-ed clone.

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.23 - the 24 joint blocks where image and text tokens attend together. Earlier blocks build structure and cross-modal understanding; later blocks carry detail.
• final_layer - the output projection.

The family gotcha applies: all ratios default to 1.0, so an untouched node returns model2. Set a base blend first, then push regions - y_embedder and context_embedder if you care about prompt adherence, late joint_blocks for finish.

One context note: SD3.0 2B's place in the merge world is modest - it's the model the community largely skipped between SDXL and the SD3.5/Large refits, so you're not going to find a deep recipe book for it. Its merge node exists because ComfyUI supports the architecture; if you're here you're blending SD3 2B checkpoints, which is a niche within a niche. The mechanics are identical to its sibling nodes, so the skills transfer.

The inputs

• INPUT_model1_key (default model1) and INPUT_model2_key (default model2) - the two SD3 2B 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 ModelMergeSD3_2B.

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.
• SD3.5 Large has more joint blocks (38 vs 24) - use ModelMergeSD35_Large for those weights. The layouts aren't interchangeable.
• Merge SD3 with SD3 only; U-Net models (SD1/SD2/SDXL) don't have joint_blocks at all.
• '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.