FLUX.1 Kontext [max]

FLUX.1 Kontext [max] is the closed, API-only version of the model that turned instruction-based editing into a commodity. Same family as the Kontext dev you might already know from local workflows - feed it reference image(s) and a sentence, get back an edit that keeps identity - but this one runs on Black Forest Labs' servers with the max-tier quality and none of the license headaches that the dev checkpoint shipped with. You trade away local control for "it just works" at a higher quality ceiling.

If the pack's RunwareArch_flux_1_kontext_dev node is the "bring your own checkpoint" version, this is the turnkey one: the model AIR (bfl:4@1) is baked in and you never think about weights again.

How it works

Kontext is architecturally interesting because it consumes reference images in-context, not through adapter embeddings - which is exactly why character identity survives an edit. This node is a taskType: imageInference REST call; your image goes up as a data URI, the instruction rides in the prompt, and the result comes back as an IMAGE tensor.

Inputs that matter

• positivePrompt - required. This is the instruction: "swap the background to a beach at sunset," "change her coat to a red puffer."
• referenceImages - the source image(s) to edit or reference, wired from Load Image. This is the whole point of the model, so get comfortable feeding it a proper batch.
• width / height - default 1024; no tight range in the schema, so match your reference's aspect roughly.
• providerSettings.bfl.promptUpsampling - the auto-expander; nice for terse instructions.
• providerSettings.bfl.safetyTolerance - 0–5, default 2, the BFL moderation dial.
• seed / numberResults - reproducibility and variants.

Install

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

Or ComfyUI Manager → search Runware → Install → restart. API key in ComfyUI Settings → Runware API key or RUNWARE_API_KEY. Prepaid top-up; per-run cost on the title bar.

Gotchas

• The Kontext family's party trick - clean object/watermark removal - is also its licensing sore spot. The dev tier's license update about circumventing content restrictions pushed a lot of users out; max sidesteps that by being an API you're renting, but you still answer to BFL's moderation.
• Results depend heavily on the reference image quality. Feed it a blurry reference and expect a blurry edit.
• No steps or CFG widgets - provider-fixed. If you need dials, the Kontext dev arch node is the knob-rich alternative.

For character-consistent editing without the 12B-model footprint or the license ambiguity, this is the cleanest path. It's the API version of the model the community called "shockingly effective."