Flux Prompt Generator

If you came here expecting the ML-powered prompt generator from Aitrepreneur's famous Ultimate Flux Workflow, reset. That one downloads text2image-prompt-generator and an opus-mt translation model and needs its own models folder. This node shares the name and the origin story - FairyRoot ported Aitrepreneur's app to ComfyUI - but the ComfyUI version is a completely different beast: a seedable randomizer that draws terms from 30 bundled JSON files and stitches them into natural-language sentences. No API, no key, no model downloads. That's not a downgrade, it's the whole point.

Why you'd reach for it

Flux's text encoder is really two encoders. T5-XXL wants flowing sentences; CLIP-L still wants the tag list. The community's consensus, which this node encodes on purpose, is that you feed sentences to T5 and tags to CLIP-L, and that naming a physical camera is the single highest-leverage phrase you can add. This node does both things at once and randomizes them per run.

So the honest use case is batch variety: plug it in front of a Flux sampler, queue 50 images, and get 50 differently-framed, differently-styled, camera-named prompts for zero typing. As a free LLM substitute it's no competition for a real model. As a slot machine for "photography of X" it's exactly what it claims.

How it works

Each of the 30 dropdowns is backed by a JSON list shipped in the repo's data/ folder - 713 artists, 564 backgrounds, 226 poses, a device list that is literally camera models like "Canon EOS R5 with RF 70-200mm f/2.8L IS USM". Every dropdown follows the same pattern:

• disabled - skip this category entirely
• random - pick a term using the seedable RNG
• a specific value - use it as-is
• comma-separated values - your own mini-pool, one is picked

The generator then assembles sentences from templates: "working as {role}", "dressed in {clothing}", "They have {eye_color} eyes", "appearing {age_group}", "shot on {device}". Along the way it drops BREAK_CLIPG and BREAK_CLIPL markers into the text, then a splitter carves it into the three encoder-specific strings. Weights like (photo_type:1.3) stay in the CLIP-L block; T5 gets a cleaned version with all parentheses stripped, because T5 doesn't read weights.

The inputs that matter

You'll mostly touch three things: seed (INT, 0–30000), custom (multiline text prepended verbatim) and subject (the main subject; takes precedence over the default_tags dropdown). Everything else is "set it to random or leave it disabled" - which is the trap: every dropdown defaults to disabled, so an untouched node spits out a near-empty prompt. You have to actively feed it.

Worth knowing: lighting on "random" picks 2–4 terms (the rest pick one), subject silently overrides default_tags, and photography_styles is ignored unless artform is photography.

The outputs and wiring

All six outputs are STRING, and the three encoder-split ones are the reason this node exists:

• t5xxl - the natural-language version, for Flux's T5-XXL input
• clip_l - the weighted tag block, for Flux's CLIP-L input
• clip_g - its own segment, matches SDXL's second encoder
• prompt - all three comma-joined (drop this into a plain CLIPTextEncode and it just works)
• seed - the seed actually used, handy for logging what produced what
• debug_info - a readable dump of which categories fired and which were ignored and why

So for Flux: wire t5xxl and clip_l into a CLIPTextEncodeFlux. For SDXL: clip_l and clip_g. The node marks itself changed on every queue, so batch runs shuffle each time.

Install

ComfyUI Manager is the easy path - search "Flux Prompt Generator" and install. Or by hand:

cd ComfyUI/custom_nodes
git clone https://github.com/fairy-root/Flux-Prompt-Generator

then restart ComfyUI. The nice part: there's no requirements.txt and no heavy dependency - the source uses only Python's standard library (the install_and_import helper in the file is dead code, never called). Thirty-one JSON files in data/ are the entire payload. It's MIT-licensed, and FairyRoot is a responsive author who posts nodes to r/comfyui and answers issues.

Where people get burned

Mainly the defaults. A fresh node is a silent no-op until you flip some dropdowns off "disabled" - turn on subject or default_tags, pick an artform, then set the categories you want varied to "random". And the seed cap of 30000 is smaller than you expect from other nodes, so treat seeds as throwaway session values rather than reproducible CivitAI-style recipes.