FLUX.1

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Architecture

• DiT (Diffusion Transformer) — replaces the UNet. Operates on patchified latent representations using bidirectional attention.
• Dual text encoders
  • CLIP-L — fast encoder for short-to-medium prompts.
  • T5-XXL — large language model encoder for long, complex prompts (up to 512 tokens by default).
• AutoEncoder (AE) — encodes and decodes between pixel and latent space. Not VAE-compatible with SD 1.x/2.x or SDXL.

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Versions

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Required model files

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Available training methods

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LoRA training

accelerate launch --num_cpu_threads_per_process 1 flux_train_network.py \
  --pretrained_model_name_or_path="flux1-dev.safetensors" \
  --clip_l="clip_l.safetensors" \
  --t5xxl="t5xxl_fp16.safetensors" \
  --ae="ae.safetensors" \
  --dataset_config="my_flux_dataset_config.toml" \
  --output_dir="./output" \
  --output_name="my_flux_lora" \
  --save_model_as=safetensors \
  --network_module=networks.lora_flux \
  --network_dim=16 \
  --network_alpha=1 \
  --learning_rate=1e-4 \
  --optimizer_type="AdamW8bit" \
  --lr_scheduler="constant" \
  --sdpa \
  --max_train_epochs=10 \
  --save_every_n_epochs=1 \
  --mixed_precision="fp16" \
  --gradient_checkpointing \
  --guidance_scale=1.0 \
  --timestep_sampling="flux_shift" \
  --model_prediction_type="raw" \
  --blocks_to_swap=18 \
  --cache_text_encoder_outputs \
  --cache_latents

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Memory optimization

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Key memory options

• --fp8_base — trains FLUX.1, CLIP-L, and T5-XXL in FP8 format. Significantly reduces VRAM at a potential quality cost.
• --blocks_to_swap <n> — offloads n Transformer blocks to CPU. FLUX.1 supports up to 35 blocks. Cannot be combined with --cpu_offload_checkpointing.
• --cache_text_encoder_outputs — caches CLIP-L and T5-XXL outputs; reduces memory usage but disables text encoder LoRA training.
• --cache_latents / --cache_latents_to_disk — caches AE outputs.

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Key training parameters

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Incompatible options

• --v2, --v_parameterization, --clip_skip
• --max_token_length (use --t5xxl_max_token_length instead)
• --split_mode (deprecated; use --blocks_to_swap)