/flux-txt2img

name: flux-txt2img
description: Build Flux txt2img workflows with Flux.1 Dev (SRPO), Flux 2 Klein 9B, Turbo LoRAs, FluxGuidance, and DualCLIPLoader patterns
globs:
  - "**/*.json"

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 VAE (320MB). Z-Image uses the same VAE *architecture* but different weights — its VAE is a separate file (`z-image-ae.safetensors`), not this one |

Flux 2 Klein 9B

| Component | Node | Model | Notes | |-----------|------|-------|-------| | **UNET** | `UNETLoader` | `bigLove_klein1.safetensors` | 17.3GB, Klein 9B variant | | **CLIP** | `CLIPLoader` (type=`flux2`) | `qwen_3_8b_fp8mixed.safetensors` | Qwen3-8B in text_encoders/ (8.3GB). Use `flux2`, NOT `flux` — both exist in the enum and `flux` fails at the sampler | | **VAE** | `VAELoader` | `flux2-vae.safetensors` | Flux 2 specific VAE (321MB) |

Klein 9B vs Flux.1 Dev: Klein uses the 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, so no separate FluxGuidance is 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 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 | |

The SRPO author recommends the ipndm/beta combo. 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",