arkennemasis fal · Flux 3 Image to Video Draft · $0.06/s

Here's the honest economics of paid video. A full 1080p render of a 10-second shot is $2.90. If you want to see three different prompts on the same still - and you do, because you never know which phrasing gives you the motion you meant - that's $8.70 of guessing. At $0.06 per second for a draft, the same three experiments cost $1.80 and you only finish the one that worked.

ArkFal_blackforestlabs_flux_3_image_to_video_draft animates a still at draft quality and returns a reusable draft cache, which is what makes the finish cheap in the other sense too: draft_enhance re-renders that draft at full quality rather than re-rolling. Same seed, same motion. You're not buying a lottery ticket, you're buying a decision.

What you set

• image - required. The opening keyframe. PNG, JPEG or WebP; uploaded to fal's CDN for free.
• prompt - the motion. The same prompt you'd use on the full node, since the enhance preserves what the draft decided.
• duration - whole seconds from 5 through 20, or auto. It's the cost dial; drafts bill by the second.
• generate_audio - on by default, and included at no extra cost, so use it to check whether a line of dialogue lands before you pay full price for it.
• aspect_ratio - auto by default.
• safety_tolerance - 0 to 4, default 2.

No resolution box. Drafts are 720p-class, which is precisely why they're a fifth of the price.

Shared fal controls, all optional: max_cost_usd (default $20, enforced before anything is uploaded), reuse_identical_run (on - rerunning an identical graph returns the saved result free rather than billing again), extra_json, max_concurrent (1 by default, so paid calls go one at a time unless you raise it).

Outputs: video, video_path, draft_cache_path, info.

Get the handoff right

The draft saves the encrypted bundle to disk as draft_cache_path - a local path. The enhance node's draft_cache_url expects a URL or data URI, and it passes that string to fal untouched. Wire the path across and it will not work; fal can't fetch your output folder.

The URL is in the draft node's info output, under fal's full answer, and it's also logged to output/fal/_requests.jsonl. Copy it into the enhance node by hand, and keep the draft's info until the finished clip is on disk.

Install

cd ComfyUI/custom_nodes
git clone https://github.com/Hishamahmer/comfyui-arkennemasis

Restart ComfyUI afterwards, or let ComfyUI Manager do it (search arkennemasis). Then, once:

FAL_KEY=your-key-from-fal.ai/dashboard/keys

in the .env file that lives beside run_nvidia_gpu.bat on a portable build, or in the ComfyUI folder otherwise. No key box on the node, deliberately - a key typed into a widget is saved into every workflow file you share. No model downloads either; the entire point of this node is that fal runs FLUX 3 for you.

Notes before you start

The node checks every input, computes the cost and compares it against max_cost_usd before it uploads a single byte - so a bad prompt length, a broken image socket or a too-tight cap fails free. Only the submit itself is billed.

Results are saved in output/fal/blackforestlabs_flux-3_image-to-video_draft/, and the node shows the clip on itself when it's done. If your ComfyUI restarts while a draft is in flight, the render continues on fal: fal Recover Result collects it by request id at no extra cost.