XB-BOX - 🆕 SCAIL 无限接力点 (New)

This is the node that makes SCAIL infinite ("🆕 SCAIL 无限接力点 (New)"). A single SCAIL generation produces one segment of about 81 frames - a few seconds. This relay node chains those segments: it generates one, keeps the tail frames, generates the next segment continuing from them, trims the overlap, appends, and repeats. Set relay_count to 10 and you get a coherent multi-minute character video from a model that can only natively do seconds. It's the SCAIL counterpart of the same "relay" idea XB uses for first/last-frame Wan.

How it works

Each relay iteration reads everything from the wan_scail_bus (the ParamBus node's output) and adds only the per-segment bits. It computes the current offset into the pose video, grabs the last previous_frame_count frames of the accumulated video as previous_frames (that's the tail stitching - the new segment literally starts from where the old one ended), encodes your per-segment prompt, then hands it all to the pack's XB_WanSCAILToVideoPro to build conditioning and a latent. Sampling runs through a standard KSampler with the bus's steps/cfg/sampler/scheduler, decode uses tiled decode from the bus's VAE knobs, the overlapping frames get trimmed, and the result is appended via concat_mode (CPU accumulation when VRAM is tight). If relay_count is more than 1, it loops internally instead of requiring you to copy-paste more nodes.

The inputs that matter

• wan_scail_bus - the WAN_SCAIL_BUS output of the ParamBus node.
• segment_length - default 81. SCAIL is trained on 4N+1 frame sections, and 81 is the standard unit; if the remaining pose frames don't fit, the last segment snaps to the nearest valid length.
• positive_prompt - per-segment; leave blank to reuse the bus's prompt.
• previous_frame_count - default 5; the overlap frames for tail stitching. Keep it modest; too high and you're re-generating a lot of already-done footage, too low and continuity jumps.
• relay_count - how many segments this node generates (1 = generate one, pass the bus on to the next relay node in the chain).
• total_frames_display - a display of the automatically computed total; mostly read-only.

Outputs: WAN_SCAIL_BUS (pass to the next relay) and the Accumulated Video Stream (IMAGE).

Install

Pack install - Manager search XB_ToolBox or clone into custom_nodes, restart. Plus the SCAIL model (the Wan 2.1 14B SCAIL fp8 from kijai's WanVideo_comfy_fp8_scaled is the community default for 16GB cards) and the ParamBus upstream. Community notes on SCAIL-2 that carry over here: it's trained at 16fps but works fine at 24fps, and you extend by chaining 81-frame sections rather than one giant generation.

Common issues

If the chain stops partway, the pose video ran out of frames - the node prints how many relays completed. A visible jump between segments means previous_frame_count is too small (or your pose/motion isn't continuous). And if VRAM climbs segment after segment, force concat_mode to CPU in the bus so the accumulated video stops squatting on the GPU.