flux2 / flex / createImage

Every Civitai image-gen node in this pack is the same trick: your prompt goes up to Civitai's cloud, the model runs on their GPUs, and an IMAGE comes back down into your graph. CivitaiImageGenFlux2FlexCreateImage is the text-to-image flavor of the hosted flex variant of Flux 2 - the one that actually hands you the sampler controls, which most of these cloud nodes don't bother exposing.

It belongs to the official civitai/civitai-comfy-nodes pack (roughly 160 nodes wrapping the Civitai Orchestration API). The engine is flux2, the model discriminator is flex, and the operation is createImage. What that buys you is Flux 2's composition and text rendering quality in a text-to-image node, with zero VRAM spent and no checkpoint on disk - your only "GPU" is the Buzz balance on your Civitai account. If you've run the full Flux 2 Dev locally, this is the same lineage minus the 24GB squeeze; if you haven't, it's the on-ramp.

How it works. Type a prompt, hit run. The node builds a workflow payload, submits it to orchestration.civitai.com, and long-polls until the job lands in a terminal state (it checks every few seconds and honors ComfyUI's Cancel, so you can bail on a slow job). Success returns four outputs: images (an IMAGE tensor - wire it into Preview, Save Image, or downstream nodes), errors (JSON of step errors), workflow_id, and raw_json (the full response, handy for cost inspection).

Inputs that matter. Only prompt is required. The interesting pair is guidance_scale (default 3.5) and num_inference_steps (default 28) - these are the settings flex lets you tune, and they're the two things you'd fiddle with on a flow-matching model locally anyway. Lower steps = faster and cheaper but looser; push guidance toward 5-7 if the result feels under-composed. width/height (512-2048), quantity (1-4), and seed behave as usual, and enable_prompt_expansion (default off) lets Civitai rewrite your prompt into something longer before generating. output_format and image_metadata are cosmetic.

Install. It ships with the pack, so you get it the same way as every other node here:

cd ComfyUI/custom_nodes
git clone https://github.com/civitai/civitai-comfy-nodes.git
pip install -r civitai-comfy-nodes/requirements.txt

…then restart ComfyUI. Or search Civitai Comfy Nodes in ComfyUI Manager's Custom Nodes Manager (publisher civitai). No model downloads - that's the entire point of a cloud node.

Auth and gotchas. Credentials resolve from a wired Civitai Auth node, then CIVITAI_API_TOKEN, then a stored key or sidebar OAuth. Missing Buzz gets you a 402 ("insufficient Buzz") from the API; a bad token is 401; spamming runs gets you 429. Jobs can take a while - the launch thread in r/civitai complained about slow generation times and timeouts - and the default kill switch is 30 minutes. Also, this is an early-preview pack: generated straight from the API spec, so node shapes and behavior can change between releases. And the standard cloud caveat applies: your prompt leaves the machine, and Civitai's content restrictions apply exactly as they do on the website.

Reach for this when you want Flux 2 quality and your card can't carry the 32B. If it can, local is still the better default - faster, free per image, and unfiltered - but as a cloud fallback in a bigger workflow, this node is honest about what it is.