Seedance 2.5: Video Extend is a ComfyUI workflow for continuing an existing video either forward (adding new moments after the last frame) or backward (adding pre-roll before the first frame). It is designed to preserve the original characters, setting, and aspect ratio while generating a new segment 4–30 seconds long (default 5). The pipeline loads your source clip with LoadVideo, extracts a short context range with Video Slice, conditions a reference-aware model via ByteDance2ReferenceNodeV2, and synthesizes the new frames using the workflow’s Seedance 2.5 generation node (d9aa59a4-3784-4796-9f1b-5b467fb41fa1). The final sequence is encoded with SaveVideo as MP4 or MOV.
Technically, the Video Slice node selects the most informative frames at the head or tail of your source (depending on whether you extend backward or forward). Those frames feed ByteDance2ReferenceNodeV2, which anchors appearance, layout, and motion cues so the generator can extrapolate in-time while maintaining character identity and scene consistency. The generation node (d9aa59a4-3784-4796-9f1b-5b467fb41fa1) then produces the new segment at the original aspect ratio, and SaveVideo assembles the output clip. A MarkdownNote inside the graph documents limits and defaults: the input video must be 1.9–30 seconds; the requested extension can be 4–30 seconds (default 5).
API
Use this workflow from code
Every Comfy workflow is a JSON graph. The payload below is this workflow, exactly as ComfyUI runs it — fetch it from the URL, keep it in version control, or load it in ComfyUI and run it node by node.
Run it from TypeScript or Python with the Comfy SDK. The same code targets Comfy Cloud or a ComfyUI you host yourself — only the base URL changes.
// Install (beta)
npm i @comfyorg/sdk
// Run this workflow (TypeScript)
import { Comfy } from "@comfyorg/sdk";
const client = new Comfy({ apiKey: "comfyui-..." });
const wf = await client.workflows.fromFile("workflow_api.json");
const job = await client.run(wf);
await job.getOutputs("<output-node-id>")[0].toFile("output.png");The SDK takes a workflow in API format: open this workflow in ComfyUI and use File → Export Workflow (API).
Comfy Cloud API access requires a plan with an API key.
FAQ
