LTX Reverse Model Sampling Pred (Ray)

LTX Reverse Model Sampling Pred (Ray) is the mirror image of RayLTXForwardModelSamplingPred: it flips LTX's sampler into the mode that extends video backward - generating the frames that come before an existing clip instead of after it. Together the pair is how you turn a short LTX generation into a longer one without restarting from scratch, which is one of the model family's most-used community patterns.

Mechanically it's the same trick as its forward sibling, but pointed the other way. The sampler gets a ModelSamplingFlux-based sampling object with the standard LTX shift of 1.15, this time with a ReverseCONST prediction mode. The difference is in the inverse noise scaling: the reverse flavor divides the latent by (1 - sigma) as it walks the schedule, which is the math that lets the model regress a latent through the noise schedule instead of progressing it. Both nodes exist because "run the sampler backward" isn't something a stock sampler does - the model needs to be told which direction it's predicting in.

When you reach for it

Forward or backward extension is a workflow decision: if your clip ends where the action continues and you want "what happens next," that's the forward node. If your clip starts mid-motion and you want the lead-in - or you're building a sequence that needs to attach frames before an existing chunk - that's this one. In a backward-extension graph you'll also see the reverse node paired with a swapped start/end latent arrangement, because the frames you're generating become the beginning of the clip.

No knobs, that's the point

Like the forward variant, this node takes only ray_actors and returns ray_actors. There's nothing to configure - the shift (1.15), the prediction mode, and the inverted scaling are all baked in. That makes it a "this belongs in the graph or it doesn't" node: put it in a forward-extension workflow and it'll fight the direction you actually want; leave it out of a backward-extension workflow and the extension simply won't run correctly.

Gotchas

• It's the reverse node for the backward direction - the naming is about the sampler's prediction direction, not about being "advanced." Grab the wrong one and you'll know by the output, not the console.
• Frame-count rules still apply: LTX windows want 8n+1 frames, and the Raylight sampler inherits whatever latent arrangement your workflow built. Keep the extension math consistent with the base clip.
• Both direction nodes sit in the same LTXV expansion group of the pack, so if one imports, the other does too - a missing-node error almost always means the whole pack didn't load, not this specific node.

Install: ComfyUI Manager → "raylight", or clone + pip install -r requirements.txt. No model downloads.