hao-ai-lab-FastVideo/scripts/checkpoint_conversion/AGENTS.md

scripts/checkpoint_conversion/ — Official → FastVideo Converters

Generated: 2026-05-02

Pre-commit excludes scripts/. Format / lint by hand against neighboring converters before opening a PR.

What Lives Here

checkpoint_conversion/
├── convert_gamecraft_full.py            # Combined DiT + VAE
├── convert_gamecraft_vae.py             # VAE only
├── convert_gamecraft_weights.py         # DiT only
├── convert_gen3c_to_fastvideo.py
├── convert_ltx2_weights.py
├── convert_minimax_h3_adaln_rank.py     # Rank-reduces AdaLN in place; same family
├── convert_turbodiffusion_to_diffusers.py
├── convert_turbodiffusion_i2v_to_diffusers.py
├── extract_llava_text_encoder.py        # Encoder extraction from a multimodal repo
├── longcat_to_fastvideo.py
├── stable_audio_to_diffusers.py
├── wan_to_diffusers.py
├── validate_longcat_weights.py          # Post-conversion validation
├── pt_to_safetensors.py                 # Generic format flip
└── create_hf_repo.py                    # Push to HF after conversion

Naming Convention

Pattern	Use
convert_<model>_*.py / <model>_to_<format>.py	One-shot converter for a model family
extract_<role>_*.py	Pull a sub-component out of a multimodal repo
validate_<model>_*.py	Post-conversion shape / norm sanity checks
<format>_to_<format>.py	Generic format conversion (no model knowledge)

Authoring a New Converter

1. Prototype the FastVideo-native component first under fastvideo/models/<role>/<model>.py. Its state_dict() is the target surface — never the other way around.
2. Mirror the official-checkpoint key pattern → FastVideo-native key pattern in a param_names_mapping (declared on the arch config in fastvideo/configs/models/<role>/<model>.py).
3. The converter's only job: load the official checkpoint, apply the mapping (with split/fuse for QKV / packed MLP), and write a safetensors directory that the ComponentLoader (fastvideo/models/loader/) can read.
4. Record intentionally skipped keys (training-only EMA, optimizer state, logvar, dynamic buffers) in a constant near the top of the converter — with a one-line reason each.
5. Add a smoke test under tests/local_tests/<model>/ or fastvideo/tests/<role>/ that loads the converted weights and runs a parity assertion against the official reference (1 forward pass).

Cross-Reference

• fastvideo/layers/AGENTS.md — which native layer to target (fused QKV, parallel MLP, etc.). Determines the split/fuse logic in the converter.
• fastvideo/models/AGENTS.md — model-side discipline (lint excluded, native state-dict is the source of truth).

Anti-Patterns

• Hard-coding tensor renames inside the model class instead of the converter.
• Converting via a private fork of transformers / diffusers weight loaders. Read tensors directly with safetensors or torch.load.
• Pushing to HF before the validate / smoke test passes locally.
• Skipping the explicit "skipped keys" list — it documents intent and prevents silent precision loss across re-conversions.