Flux 2 Pro Preview (BFL)

Flux 2 Pro Preview (BFL) is the same Flux 2 Pro node with one difference: it hits the flux-2-pro-preview endpoint instead of the stable one. BFL runs a preview tier for each model family - the latest advances, shipped early, quality and behavior subject to change between releases. In the ComfyUI-FLUX-BFL-API pack it's a one-click way to try what BFL is cooking before it's baked, without waiting for a public announcement.

That "subject to change" is the entire personality of this node. A preview endpoint's weights, prompt behavior, and even its moderation behavior can shift out from under you between generations. If you're doing anything repeatable - a batch, a client proof, a workflow you'll reuse - this is the wrong tier. If you're exploring, it's exactly right.

How it works

Identical to Flux 2 Pro mechanically: build the request from your prompt and up to eight base64 reference images, POST to flux-2-pro-preview, poll get_result?id=..., return an IMAGE. Same inputs, same output, same pack plumbing - only the URL changes.

The inputs

• prompt - the scene description.
• input_image … input_image_8 - up to eight references for character/object/style consistency (the Flux 2 signature move).
• width / height - optional, ≥64 if set, default lets BFL decide.
• safety_tolerance - 0–5, default 2.
• output_format - jpeg (default) or png.
• Optional seed, webhook_url/secret, config.

Installing it

Same single-pack install as the rest:

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

Restart, key in config.ini or via Flux Config (BFL). No models to download; torch is the only declared dependency.

Where people get burned

• Treating preview output as stable. The whole point of a preview tier is that it changes. Results that look amazing this week can regress next week when BFL updates the endpoint. Never ship a client deliverable off a preview without a stable-tier backup.
• Cost confusion. Preview tiers aren't a free trial - they're metered like the stable tiers. Check Flux Credits (BFL) before running big preview batches.
• Black output. The pack's standard failure signal - moderation, error, or poll timeout. [BFL] logs print a curl equivalent for every call, so you can replay and see what the preview endpoint actually returned.

The honest take: Flux 2 Pro Preview is a peek, not a foundation. Use it to see where BFL's quality is heading, then run the real jobs on the stable node.