Cond Set Default Combine

Masked conditioning has a hole in the middle: whatever your masks don't cover gets no instructions at all. ConditioningSetDefaultCombine ("Cond Set Default Combine") is the single-conditioning fix for that. You give it your existing conditioning and a second conditioning marked as the default, it combines them, and the sampler uses the default one to fill every pixel the region masks didn't claim. It's the single-cond cousin of PairConditioningSetDefaultCombine - same idea, half the wiring.

The problem it solves

Think about what a regional workflow does. Each masked conditioning owns its area - the left character's prompt owns the left half, the right character's prompt owns the right half. The background, the lighting, the framing in between get nothing. No prompt is steering them, and the sampler improvises, which is exactly when you get the "two images stitched together" look that dominates every thread about this technique.

The fix is a default conditioning: a prompt describing the whole scene. During sampling, ComfyUI computes each masked region first, then runs the default against the remaining unmasked area, so it fills the gaps without overriding the regions. That's the mechanism, and it's why this node exists - it's the sanctioned way to stamp the default flag and merge in one step.

The inputs

• cond - your existing conditioning, usually the combined output of the regional nodes.
• cond_DEFAULT - the global prompt. Plain CLIP-encoded text, no mask, no region. "two characters on a neon-lit street at night, cinematic" - the scene, not a subject.
• hooks (optional) - a HOOKS group to attach to the default cond. Rarely used, but available for cases like a global style hook you want everywhere the default reaches.

Output: a single merged CONDITIONING.

Note the asymmetry on purpose: the _DEFAULT input gets the default flag and any hooks; your existing cond is left as-is. It's a layering operation, not a symmetric combine.

Why you'd pick this over the pair version

The pair version (PairConditioningSetDefaultCombine) handles positive and negative together - you need it when your regions are built as pos/neg pairs, which the hook-based regional nodes encourage. This single version is for when you're managing one conditioning stream and just want to bolt a global prompt on the end before the sampler. If your pipeline already merged its positive and negative into one, this is the smaller, cleaner node.

The practical notes

The default flag only means something if regions actually exist - with no masked conds in the list, "fill the remaining area" is just "fill everything," and the node degenerates into a fancy combine. And the family economics still apply: if you attach a hook to the default, that's another separate model pass on top of every region pass. One genuinely useful trick from the community: feed a TIMESTEPS_RANGE from ConditioningTimestepsRange into the Set Props node on the _DEFAULT path so the global prompt shapes composition early, then bows out before it can fight the region LoRAs in the detail phase.

Ships with ComfyUI core, no install, experimental like all the hooks nodes. Under advanced → hooks → cond single.