What problem does it solve? HOT-Step CPP loads music-generation models (LM, DiT, VAE, text encoder) from GGUF files, and failures like "no GGUF models found", crash-loops, or models that show as installed but never appear in generation dropdowns are hard to diagnose without knowing how the engine scans and classifies files. This Skill documents the exact registry rules, quantization procedures, and download-service internals needed to add, convert, quantize, publish, and debug models. ## Core Features & Use Cases - Model installation and classification: Explains which component (LM, DiT, VAE, text encoder, PP-VAE) needs which file, where files must live, and how the engine's startup scan classifies GGUF, safetensors, and ONNX files. - Conversion and quantization procedures: Step-by-step commands for converting Hugging Face safetensors checkpoints to BF16 GGUF, quantizing to Q4_K_M/Q8_0/MXFP4 and other types, and converting ComfyUI int8/ConvRot checkpoints. - Model Manager and publishing workflow: Covers the Node download service, the model-registry.json catalogue, REST API routes, and the full publish pipeline (Hugging Face upload, registry entry, pack assignment, prereq verification). - Use Case: A user reports a model shows "installed" in the Model Manager but is missing from generation dropdowns. The Skill pinpoints the cause: the engine scans only root-level .gguf files while the Node installed-check also scans one subdirectory level, so the file must be moved to the models root. ## Quick Start Ask the assistant to diagnose why a downloaded GGUF model is not appearing in the generation dropdowns, or to walk through quantizing a BF16 DiT model to Q4_K_M.