FalFluxAPI

This is the flagship node of the ComfyUI-Cloud-APIs pack, and the reason the pack exists. FalFluxAPI sends your prompt to fal.ai, where BFL's hosted Flux models actually run, then downloads the result and hands you a perfectly ordinary IMAGE tensor. You keep your graph, your prompt discipline, and your save pipeline; you just skip the part where a 12B transformer melts your GPU for two minutes.

It's aimed squarely at people who are GPU-poor - the pack author built it on a 2060 6GB and posted it to r/StableDiffusion as "How to use the Flux API in your local workflows." If you've been staring at Flux workflows and assuming they need a 4090, this node is the workaround. It's also the only realistic way to touch Flux Pro in ComfyUI, because Pro has never been downloadable.

How it works

The endpoint dropdown picks which fal model gets called:

• schnell (4+ steps) → fal-ai/flux/schnell
• dev (25+ steps) → fal-ai/flux/dev
• pro (25+ steps) → fal-ai/flux-pro
• realism (25+ steps) → fal-ai/flux-realism
• pro 1.1 → fal-ai/flux-pro/v1.1

The node reads your key from a text file, sets FAL_KEY, submits the job, and downloads the image. One bit of baked-in logic to know about: if you pick schnell and crank steps past 8, it silently clamps to 8. Schnell is a step-distilled model that wants 1-4 steps anyway, so this is the pack protecting you from yourself.

The inputs that matter

• endpoint - schnell is cheap and fast (Apache 2.0), dev is the community-quality standard, pro/realism cost more but are the API-only tiers.
• prompt - Flux likes natural language. Don't bring SDXL tag-soup habits.
• width / height - 256–2048, snapped to multiples of 16. Flux's native sweet spot is 1024², and it tolerates up to roughly 2MP happily.
• steps - default 4, which is right for schnell; bump to 20-30 if you switch to dev.
• cfg_dev_and_pro - guidance. 3.5 is the stock default and the community starting point; a lot of people find lower is better.
• image_count - 1 to 4. Output comes back as a batched IMAGE tensor, which is why the pack also ships SplitImages to un-batch it.

api_key and seed are self-explanatory. Output is IMAGE - wire it straight into Save Image / Preview.

Install

ComfyUI Manager → search "ComfyUI-Cloud-APIs", or:

cd ComfyUI/custom_nodes
git clone https://github.com/BetaDoggo/ComfyUI-Cloud-APIs

Restart, then create an account at fal.ai, add a key at fal.ai/dashboard/keys, and paste it into a .txt file in ComfyUI-Cloud-APIs/keys/ (delete nokey.txt). You also need to top up at fal.ai/dashboard/billing - fal won't serve you on an empty balance. No model files, nothing heavy to download; the pack's dependencies are just fal-client, replicate, requests, numpy, and pillow.

Troubleshooting

• Application 'fal-ai/flux' is not public - a real error people hit, usually because the account has no credit or the endpoint isn't enabled. Top up billing and retry.
• Muddy or blurry Flux output - you're on dev with a nonstandard sampler in your head. This node doesn't expose sampler/scheduler; it uses fal's defaults. Drop guidance, keep steps in the 20-30 band.
• It costs money - check fal.ai/models for per-image pricing before you iterate a prompt 60 times. The author's own advice is to skip automated top-ups for your wallet's sake.

The pack is archived and unmaintained, but this node is a thin API wrapper, so it keeps working. If fal changes an endpoint someday, that's when you fork it.