What can Kling 4.0 do according to its published API schema (Oct 2026), and what is still unknown?

fal lists four Kling 4.0 endpoints (registry date 2026-10-16, status active, but every description says "API access is coming soon"; playground and fal Agent only). Schema facts: text-to-video, image-to-video (start and optional end frame), reference-to-video and video-to-video edit; 720p or 1080p (default 1080p); duration 3-30 s (default 5); aspect ratios 16:9, 9:16, 1:1, 21:9 (+auto for references). Multi-shot via multi_prompt: a list of {prompt, duration} shots whose durations sum to the video length. Reference-to-video: up to 10 images (@Image1..), up to 5 reference videos (@Video1.., 3-30 s each, 30 s combined with element videos), up to 7 elements (@Element1..) each defined by a frontal image plus 1-3 extra-angle images or a 3-30 s video; up to 3 elements may carry a voice_id (created with fal-ai/kling-video/create-voice) and up to 3 may be video elements. Edit: input video 3-30 s, ≤300 MB, 700-4553 px sides, instructions reference @Video1 plus optional images/elements; output length defaults to the source. Practical read: 30 s single-generation length with per-shot prompts and voice-bound elements is the headline change versus Kling 3.0/O3 (whose Runway/fal endpoints remain the priced, callable ones: Kling 3.0 Pro $0.12/s, $0.17/s with audio on Runway per C3-B387-01). Unknown: price, audio controls (no audio flag in the published input schema), native resolution above 1080p, official Kling-side documentation; not tested. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Host (fal) registry schema, not Kling documentation; API access marked coming soon. Limitations: Registry schema of a not-yet-callable API; can change at launch; no outputs observed. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://api.fal.ai/v1/models?endpoint_id=kling/v4/text-to-video&expand=openapi-3.0",
      "note": "metadata.description; KlingV4Element.voice_id / elements; duration; KlingV4Shot"
    },
    {
      "url": "https://api.fal.ai/v1/models?endpoint_id=kling/v4/reference-to-video&expand=openapi-3.0",
      "note": "metadata.description; KlingV4Element.voice_id / elements; duration; KlingV4Shot"
    }
  ]
}