Flux Dev (BFL)

Flux Dev (BFL) is the original community darling - the open-weights model that took over r/StableDiffusion in late 2024 - delivered through Black Forest Labs' API instead of your local checkpoint folder. In the ComfyUI-FLUX-BFL-API pack, this node is the text-to-image workhorse: type a prompt, get a picture. No 12GB download, no VRAM math, no distilled-Schnell compromise. For someone with a modest GPU who still wants proper Flux Dev quality, this is the honest shortcut.

The catch is the price model and the wait - every generation is a metered API call that takes tens of seconds to poll. But if you're already paying for the BFL API (or you're on someone else's key), the Flux Dev tier is the cheap one, and this node gives you the exact same model the local crowd runs, with the familiar knobs exposed.

How it works

Standard pack flow: build the request, POST to flux-dev, poll get_result?id=... every 5 seconds, return an IMAGE. Unlike the Pro tiers, Dev gives you explicit control over steps and guidance - it's a real diffusion knobs-and-dials node, not a "tier decides everything" one. There's also an image_prompt input if you want image-to-image, which is a rarer feature in the Pro line.

The inputs that matter

• prompt - the whole ballgame.
• width / height - 256–1440 each, default 1024×768. Needs to land on a 32-multiple or the request bounces (the pack validates this).
• steps - 1–50, default 28. The Dev-native default; you rarely need more.
• guidance - 1.5–5, default 3. Dev's sweet spot is low, and this node's range reflects that. Crank it and you get the overcooked look.
• prompt_upsampling - let BFL internally expand your prompt. Occasionally helps short prompts, usually unnecessary.
• safety_tolerance - 0–6, default 2. Moderation strictness.
• output_format - jpeg (default) or png.
• image_prompt - optional base64 image for img2img-style guidance (wire it through Image to Base64 (BFL)).
• Optional seed, webhook_url/secret, config.

Output: one IMAGE tensor.

Installing it

One pack, one install:

cd ComfyUI/custom_nodes
git clone https://github.com/gelasdev/ComfyUI-FLUX-BFL-API.git

Restart, set your key in config.ini or a Flux Config (BFL) node. The pack's only real dependency is torch, already bundled - nothing heavy to install, no model files.

Where people get burned

• Black output. The pack's universal failure signal: moderation, API error, or the ~200s poll ceiling. Watch [BFL] logs - every POST prints a curl equivalent you can replay to see the raw response.
• Assuming "Dev" means local speed. It's a remote call. Expect a wait; that's the price of zero local VRAM.
• Dimensions off the 32-grid. The node checks and will fail with a blank image rather than silently squishing. Keep width/height multiples of 32.
• Not reading the moderation reality. Dev on the API is the censored BFL stack, full stop. The community's NSFW Flux workflow runs on local weights and their own LoRAs, not through this API. If that's the goal, this isn't the node for it.

The honest take: local Flux Dev still wins on cost-per-image and privacy once you have the hardware. This node is for the no-VRAM, need-it-now, already-own-a-key crowd - and for anyone who wants Dev-quality results without babysitting a 12GB download.