flux-txt2img

name	flux-txt2img
description	Build Flux txt2img workflows — Flux.1 Dev (SRPO), Flux 2 Klein 9B, Turbo LoRAs, FluxGuidance, and DualCLIPLoader patterns Use when this capability is needed.
metadata	{"author":"artokun"}

Flux Text-to-Image Workflows

Overview

Flux is a guidance-distilled diffusion model family from Black Forest Labs. It uses a separate FluxGuidance node instead of KSampler CFG (which must always be 1.0). Three variants are available locally:

1. Flux.1 Dev SRPO — Fine-tuned Flux.1 Dev with SRPO alignment. Uses DualCLIPLoader (T5XXL + CLIP-L). BF16 only.
2. Flux 2 Klein 9B — Distilled Flux 2 variant. Uses single CLIPLoader (Qwen3-8B) + flux2-vae.safetensors. Fast 4-step generation.
3. Flux 2 Turbo LoRA — Applied to Flux.1 Dev for 4-step generation.

Models

Flux.1 Dev SRPO

Component	Node	Model	Notes
UNET	UNETLoader	flux.1-dev-SRPO-BFL-bf16.safetensors	22.7GB, BF16 only — FP8 produces broken results
CLIP	DualCLIPLoader (type=flux)	clip_name1: t5xxl_fp8_e4m3fn.safetensors, clip_name2: clip_l.safetensors	T5XXL (4.7GB) + CLIP-L (235MB)
VAE	VAELoader	ae.safetensors	Standard Flux/Z-Image VAE (320MB)

Flux 2 Klein 9B

Component	Node	Model	Notes
UNET	UNETLoader	bigLove_klein1.safetensors	17.3GB, Klein 9B variant
CLIP	CLIPLoader (type=flux)	qwen_3_8b_fp8mixed.safetensors	Qwen3-8B in text_encoders/ (8.3GB)
VAE	VAELoader	flux2-vae.safetensors	Flux 2 specific VAE (321MB)

Klein 9B vs Flux.1 Dev: Klein uses Qwen3-8B text encoder (not T5XXL + CLIP-L). It has a different VAE (flux2-vae.safetensors). 9B distilled runs in 4 steps; 9B base needs ~50 steps at CFG 5.0. Fits in ~20GB VRAM with FP8.

Flux 2 Turbo LoRA (applied to Flux.1 Dev)

Component	Node	Model	Notes
LoRA	LoraLoaderModelOnly	flux2-turbo-lora.safetensors	2.6GB, strength 1.0
Alt LoRA	LoraLoaderModelOnly	Flux2TurboComfyv2.safetensors	Community variant, same size

Conditioning

CLIPTextEncodeFlux (Recommended for Flux.1 Dev)

Provides separate prompt fields for each text encoder:

{
  "class_type": "CLIPTextEncodeFlux",
  "inputs": {
    "clip": ["<dual_clip>", 0],
    "clip_l": "short prompt for CLIP-L",
    "t5xxl": "detailed description for T5XXL",
    "guidance": 3.5
  }
}

clip_l captures key semantic features. t5xxl expands and refines descriptions. For simple use, put the same prompt in both fields. Guidance is built into this node — no separate FluxGuidance needed.

FluxGuidance (Alternative)

If using standard CLIPTextEncode instead of CLIPTextEncodeFlux, apply guidance separately:

{
  "class_type": "FluxGuidance",
  "inputs": {
    "conditioning": ["<clip_text_encode>", 0],
    "guidance": 3.5
  }
}

Guidance Values

Scenario	Guidance	Notes
Short prompts	3.5–4.0	Tighter prompt adherence
Long/complex prompts	1.0–1.5	More creative freedom
Realism	2.5	Less glossy skin, richer detail
Standard	3.5	Default for most use cases

Negative Conditioning

Flux does NOT support traditional negative prompts (guidance-distilled, CFG=1.0). Use ConditioningZeroOut:

{
  "class_type": "ConditioningZeroOut",
  "inputs": { "conditioning": ["<positive_cond>", 0] }
}

Or simply use an empty CLIPTextEncode for the negative input.

Sampler Settings

Flux.1 Dev SRPO

Parameter	Standard	Notes
steps	20	Range: 20–28
cfg	1.0	Always 1.0 — guidance is via FluxGuidance
sampler_name	ipndm	Author-recommended for SRPO
scheduler	beta	Author-recommended for SRPO
guidance	3.5	Via CLIPTextEncodeFlux or FluxGuidance
denoise	1.0

SRPO note: The ipndm/beta combo is specifically recommended by the SRPO author. Standard Flux settings (euler/simple) also work but ipndm/beta gives better results with this fine-tune.

Flux 2 Klein 9B (Distilled)

Parameter	Value	Notes
steps	4	Distilled model, 4 steps is optimal
cfg	1.0	Always 1.0
sampler_name	euler
scheduler	simple
denoise	1.0

Flux 2 Klein 9B (Base/Undistilled)

Parameter	Value	Notes
steps	50	Full quality
cfg	5.0	Higher CFG for base model
sampler_name	euler
scheduler	simple

Flux.1 Dev + Turbo LoRA

Parameter	Value	Notes
steps	4	Turbo-distilled
cfg	1.0
sampler_name	euler
scheduler	simple
lora_strength	1.0

Resolutions

Aspect	Resolution	Megapixels
Square	1024x1024	1.0MP
Portrait 3:4	896x1152	1.0MP
Landscape 4:3	1152x896	1.0MP
Landscape 16:9	1344x768	1.0MP
Portrait 9:16	768x1344	1.0MP

Flux operates at ~1 megapixel natively. Dimensions should be multiples of 8.

Prompt Style

Natural language descriptions. No quality tags needed (unlike SDXL/Illustrious). Detailed, descriptive prompts work best.

Good: "A young woman with auburn hair sits at a sunlit cafe in Paris, wearing a cream linen blazer, soft bokeh background, shot on Sony A7III 85mm f/1.4"
Bad: "masterpiece, best quality, 1girl, cafe, paris"

Complete Workflow: Flux.1 Dev SRPO

{
  "1": { "class_type": "UNETLoader", "inputs": { "unet_name": "flux.1-dev-SRPO-BFL-bf16.safetensors", "weight_dtype": "default" }},
  "2": { "class_type": "DualCLIPLoader", "inputs": { "clip_name1": "t5xxl_fp8_e4m3fn.safetensors", "clip_name2": "clip_l.safetensors", "type": "flux" }},
  "3": { "class_type": "VAELoader", "inputs": { "vae_name": "ae.safetensors" 
       
      
     
     
     
  
           
              
       
      
      
      
      
               
  
              
             

Complete Workflow: Flux 2 Klein 9B (Distilled, 4-Step)

{
  "1": { "class_type": "UNETLoader", "inputs": { "unet_name": "bigLove_klein1.safetensors", "weight_dtype": "default" }},
  "2": { "class_type": "CLIPLoader", "inputs": { "clip_name": "qwen_3_8b_fp8mixed.safetensors", "type": "flux" }},
  "3": { "class_type": "VAELoader", "inputs": { "vae_name": "flux2-vae.safetensors" }},
  "4"           
           
              
       
      
      
      
      
               
  
              
             

Klein note: Uses single CLIPLoader (not DualCLIPLoader) with type: "flux" and the Qwen3-8B text encoder from text_encoders/. The CLIP loader path resolves from models/text_encoders/.

Complete Workflow: Flux.1 Dev + Turbo LoRA (4-Step)

{
  "1": { "class_type": "UNETLoader", "inputs": { "unet_name": "flux.1-dev-SRPO-BFL-bf16.safetensors", "weight_dtype": "default" }},
  "2": { "class_type": "LoraLoaderModelOnly", "inputs": { "model": ["1", 0], "lora_name": "flux2-turbo-lora.safetensors", "strength_model": 1.0 }},
  "3": { "class_type": "DualCLIPLoader", "inputs":        
          
       
      
     
     
     
  
           
              
       
      
      
      
      
               
  
              
             

LoRA Support

Custom LoRAs (jellyfish, etc.)

Apply Flux LoRAs with LoraLoaderModelOnly between UNET and KSampler:

{
  "class_type": "LoraLoaderModelOnly",
  "inputs": {
    "model": ["<unet_or_previous_lora>", 0],
    "lora_name": "<lora_file>.safetensors",
    "strength_model": 1.0
  }
}

Klein LoRAs

Klein 9B LoRAs go in loras/Flux.2 Klein 9B/ subfolder:

• klein_slider_detail.safetensors — Detail slider LoRA

VRAM Considerations

Model	VRAM	Notes
SRPO BF16 + DualCLIP	~24GB	Fills RTX 4090 exactly. Must use BF16 — FP8 is broken for SRPO
Klein 9B FP8 + Qwen3-8B	~20GB	Fits comfortably on 4090
SRPO + Turbo LoRA	~24GB	Same as SRPO base

• Always clear_vram before switching to Flux from another model family
• T5XXL is the main VRAM consumer alongside the UNET — both stay loaded during sampling
• CLIP-L is small (235MB) and negligible

Tips

1. KSampler CFG must always be 1.0 — all guidance is through CLIPTextEncodeFlux or FluxGuidance
2. SRPO requires BF16 — the FP8 quantization is known to produce broken results with this fine-tune
3. For short prompts (1-2 sentences), increase guidance to 3.5–4.0. For long prompts (paragraph), decrease to 1.0–1.5
4. Flux generates excellent text in images — put text to render in quotes within your prompt
5. Klein 9B is the fastest option at 4 steps — use it for rapid iteration, then switch to SRPO for final quality

---

Source: artokun/comfyui-mcp — distributed by TomeVault.