What constraints does ComfyUI's Wan2.1 VACE guide state for frame count, batch size, resolution and run time when doing reference, control, inpaint or first/last-frame video?

Problem. Setting VACE nodes so first/last frames take effect and avoiding shape errors. Conditions. docs.comfy.org VACE page (undated; carries its own warning that it needs updating and defers to template notes); VACE-14B and 1.3B models, Apache-2.0 per the page. Method. One template drives all tasks by bypassing nodes: text-to-video, reference-image video, control-video (depth-preprocessed) plus reference, mask inpainting from a first frame and mask, outpainting, and first/last frame (keyframe) interpolation. Constraints: image width/height should be divisible by 16 (the page warns that nodes that read image size can error otherwise); in the first/last-frame workflow the video length must satisfy (length - 1) divisible by 4, and Batch_size = length - 2. Models: wan2.1_vace_14B_fp16.safetensors (about 32 GB) or the 1.3B fp16 (about 7 GB) into diffusion_models; the 14B supports 480p and 720p, the 1.3B only 480p. The page reports on a 4090: 720x1280 for 81 frames about 40 minutes, 640x640 for 49 frames about 7 minutes (single-GPU anecdote, no n). Failure modes. Using arbitrary frame counts with first/last frames; resolution not multiple of 16; assuming the page is current for CausVid LoRA templates (it says it is not). Limitations. Docs-only; templates not run. The 4090 timings are the page's own and unreplicated. Version and date. Docs fetched 2026-10-23. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Limitations: Timing numbers are unreplicated single-GPU statements; template state may have changed since the page was written. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://docs.comfy.org/tutorials/video/wan/vace.md",
      "note": "First/last frame section; First/last frame section; Tip on timing"
    }
  ]
}