How do Veo 3.1 and Luma Dream Machine use start and end keyframes, and what can I use them for in multi-shot continuity?

Problem. Controlling where a clip begins and ends so that cuts and transitions line up. Conditions. Veo 3.1 'first and last frame' (Google, Oct 2025) and Luma Dream Machine keyframes (Luma help article, Nov 6, 2024). Method. Veo: supply a start image and an end image and describe the transition in the prompt; the guide's example builds both stills with an image model, then asks for a smooth 180-degree arc between them. Luma: set a start frame and an end frame (uploaded or generated), optionally add a text prompt alongside the keyframes to guide the transition; Extend can also take an image keyframe as the destination, generating an extension of up to 9 seconds from a default 4-second clip. The Luma API field names (frame0, frame1, loop) are in C3-B571-11. Use for continuity (inference): make the start frame the last frame of the previous shot to continue a move; design the end frame as the pose you will cut from; generate bridging stills with the same lighting and lens clauses. Failure modes. The pages do not state how closely the model hits the end frame or what happens when the two frames contradict the prompt. Limitations. Luma page is a 2024 UI help article; the API has moved on (see C3-B571-11). Version/date. Fetched 2026-10-23. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Limitations: Inference on chaining; no adherence statistics. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://lumalabs.ai/learning-hub/how-to-use-keyframes",
      "note": "Intro; Prompt with Keyframes; Extend Keyframes; How it works; Workflow 1; continuity use"
    },
    {
      "url": "https://cloud.google.com/blog/products/ai-machine-learning/ultimate-prompting-guide-for-veo-3-1",
      "note": "Intro; Prompt with Keyframes; Extend Keyframes; How it works; Workflow 1; continuity use"
    }
  ]
}