Runway API

Two settings on this node are traps and one is a gift. The traps: duration is 5 or 10 seconds only, and 10 seconds can't be 1080p. The gift: watermark defaults to the string kie.ai, and setting it to an empty string removes the watermark entirely. Nobody reads that tooltip until they've already rendered the clip.

What it is

KIE_Next_runway_be3d3441 calls Runway's video generation through KIE.ai - text-to-video from a prompt, or image-to-video when you connect a reference frame. The KIE Next pack generates it from KIE's catalog rather than hand-coding a form, which is why the settings look like an API request.

Runway as a company is a slightly strange neighbour in this ecosystem: it published the SD 1.5 weights in 2022 and then deleted them in 2024, breaking half the internet's default download paths, and has been a closed commercial video company ever since. That history is why there's no Runway checkpoint on your disk and why a node like this exists at all.

Why reach for it: it's a short-clip generator with an image input. You have a still you like and want five seconds of motion, or you want a fast concept pass without burning an hour of local Wan. It's a drafting tool, not a finishing tool.

How it works

The pack's standard pipeline: build the request, upload any connected media, create the task, poll until timeout_seconds (1200 default), download the result into a VIDEO. Credits spent show on the node, and you get task_id back as a socket - which is the input to the pack's Runway API Extend AI Video node if you want to keep going past the initial clip.

The inputs that matter

prompt is required and caps at 1800 characters. Be specific about subject, action, style and setting - the tooltip's own advice, and it's right. When you connect image_url, the prompt shifts meaning: it now describes how to animate or modify that image.

duration is a FLOAT with a default of 5, and the documented values are 5 or 10. quality is 720p or 1080p - and note the type: it's a plain string field, not a dropdown. A typo like 1080 won't be caught by a menu, so type it carefully. The hard rule the docs give is that a 10-second video cannot be rendered at 1080p; pick one.

aspect_ratio (9:16 default, plus 16:9, 4:3, 1:1, 3:4) is only for text-to-video. With an image connected it's ignored and the output takes the image's ratio - which is the behaviour you want, but it does mean a setting you changed can appear to do nothing.

watermark is a string that renders in the bottom-right corner, defaulting to kie.ai. Set it to "" for a clean frame, or put your own handle in it. This is the single most-missed setting on the node.

Outputs

video → KIE • Preview Video to watch it inside the graph, or KIE • Save Video to write an MP4 under output/KIE-Videos and get a saved_file value KIE • Persistent Load Video can reload later. task_id is what the Extend node and KIE • Reuse Completed Image/Video/Audio consume. url is the provider link - treat it as disposable. all_urls_json, raw_json, credits_consumed, credits_left round it out. It's not an output node, so connect something downstream or it won't run.

Installing it

ComfyUI Manager → search "KIE.ai Nodes Next", or:

comfy node install kie-ai-nodes-next

Manual:

cd ComfyUI/custom_nodes
git clone https://github.com/felipederosilva/ComfyUI-KIE-Nodes-Next
pip install -r requirements.txt

Restart, then Settings → KIE.ai Nodes Next → Connection and paste your KIE.ai API key. The pack validates it before overwriting a working key and only ever displays a masked fingerprint; the key stays out of your workflow JSON. Environment variables are intentionally unsupported.

Dependencies are requests, Pillow, numpy, PyYAML. No weights to download and nothing to fit in VRAM.

Where people get burned

The duration/quality pair. Ten seconds at 1080p isn't a setting the API refuses gracefully in your head - it's just invalid. Decide which you want before you write the prompt.

The watermark. Now you know.

It's a five-second machine. Local video people complain they can't get past five seconds; this is a commercial endpoint that gives you five seconds and charges for the privilege. Use it for the shot it's good at. If you need a longer sequence, chain the Extend node - knowing that each hop drifts.

The provider's filter, not the node's. Runway's own moderation applies to whatever you send, and there's no local override for a model you can't download. If a prompt keeps getting refused, that's the endpoint answering, not a bug in the pack. Right-click → KIE Next · Check inputs & model controls will show you the documented fields and limits it can verify locally; a refusal from Runway itself won't appear there.