Practical: memory, speed, and reproducibility

A few habits separate a smooth setup from a miserable one. Memory comes first, and the good news is that modern ComfyUIComfyUIThe dominant node-based interface for running diffusion models locally. Started by 'comfyanonymous' in January 2023, now stewarded by Comfy Org. manages VRAMVRAM (Video RAM)The memory on a GPU. It sets a hard ceiling on the model size and image resolution you can run locally. dynamically on its own; the old manual tiering flags have largely become automatic, and most people never touch them. When you do run against the wall there are still escape hatches, from reserving headroom, to forcing more of the model onto system RAM, to, in the worst case, running on the CPU, and a tiled VAEVAE (Variational Autoencoder)A neural network that learns to compress images into a small numerical representation (a latent) and decompress them back. Used in latent diffusion models to make the generation process tractable. decode that processes a large image in patches rather than all at once is often the single thing that lets a big final decode fit in memory that a whole-image decode would not.

Reproducibility comes second, and the seed is the whole game. Fix it and change one thing at a time, rather than chasing a good result you can never get back; there is even a flag to force slower, fully deterministic math when you need bit-for-bit repeatability, though results still drift across different GPUs and library versions. Because every generated PNG carries its own workflow, a good image doubles as a saved recipe. Finally, the most common self-inflicted wounds are boringly mechanical: models filed in the wrong folder (checkpoints, LoRAs, VAEs, ControlNets, and upscalers each have their own directory under models), a VAE mismatched to its checkpointCheckpointA saved set of model weights. The .safetensors or .ckpt files you download to run a model., or an SDXL VAE throwing black frames in half precision, a problem common enough to have its own fix flag. Keep the folders clean and match your parts, and most of the errors people post about never happen to you.