ai-toolkit/toolkit/models/v2/PLANNING.md

v2 Model Module Restructure — Planning

Goal

Every component the toolkit loads (DiTs/transformers, unets, text encoders, vision encoders, VAEs, audio VAEs) becomes a class extending one base module in toolkit/models/v2. BaseModel (toolkit/models/base_model.py) stays as the multimodal holder that each arch in extensions_built_in/diffusion_models extends — that layer is good. The layer below it is what gets unified: one loading entry point, one quantization path, one save path, shared component definitions instead of per-model-folder copies.

End state this enables:

• Live server with model hot-swap: a resident process where, when a generation or training run requests a different model, the unused components are dropped and the new ones loaded. Shared component classes (same TE/VAE reused across archs) make component-level reuse possible instead of full teardown/reload.
• Model loading test suite: a test that loads each registered arch one at a time and runs an inference pass. Every model type gets added to this suite as it is migrated (see Testing below).
• Comfy-aligned weights: weights live in the ComfyUI folder layout under MODELS_PATH (shareable with a ComfyUI install), download there when missing, and saves are comfy-format. Eventually defaults move to comfy / our own prequantized releases for everything.

Current state (survey 2026-08-27)

Three generations of loading conventions coexist:

1. Legacy monolith toolkit/stable_diffusion_model.py (is_flux / is_v3 branches); still the silent fallback in toolkit/util/get_model.py when an arch string doesn't match.
2. BaseModel subclass per arch (35 registered classes), each with a hand-written load_model() / save_model().
3. toolkit/models/v2/_mixin.py (OstrisModelMixin) — the intended fix, currently used by one model (v2/z_image.py → z_image extension).

Duplication highlights

• BFL KL autoencoder: full copies in flux2/src/autoencoder.py and ideogram4/src/vae.py (header says "Flux2 KL autoencoder").
• Qwen3-VL text encoder loaded independently in qwen_image, nucleus_image, krea2, ideogram4, mageflow, minimax_h3 — from several different repo sources; krea2 hand-patches the vision tower locally.
• Qwen3ForCausalLM TE load: 3 verbatim line-for-line copies (z_image/z_image.py:257, z_image/z_image_l2p_model.py:471, zeta_chroma/zeta_chroma_model.py:146).
• Flux1 VAE + T5 + CLIP trio loaded 4x from 2 different repos (chroma ×2, flux_kontext, legacy SD path).
• Comfy-file resolver copy-pasted: minimax_h3/minimax_h3.py:248 (_resolve_comfy_file) → ltx2/ltx2.py:1254 ("mirrors MinimaxH3Model").
• AutoencoderKLQwenImage latents mean/std handling triplicated (qwen_image, nucleus_image, krea2).
• transformer. ↔ diffusion_model. LoRA key rename copy-pasted ~15x in convert_lora_weights_before_save/load overrides.
• Fake CLIP/TE/config stubs redefined in ~5 places (canonical: toolkit/models/FakeVAE.py, toolkit/unloader.py).

Inconsistency highlights

• Quantization, 5 paths: quantize_model() (block-streaming, ARA-aware — ~21 users), raw quantize() (~10 users, no block streaming/excludes, but the only path honoring quantize_kwargs), hidream's hand-rolled block loop, the v2 mixin's own quantize_, and bare TE quantization everywhere.
• Known bugs: ~9 sites quantize the TE with qtype instead of qtype_te (chroma ×2, flux2, flux_kontext, cogview4, wan21, legacy SD, ...); toolkit/models/loaders/umt5.py accepts a comfy_files param it never uses, so wan21's comfy-TE path is a silent no-op.
• Saving, 4 incompatible styles: diffusers save_pretrained folders, flat safetensors, safetensors-inside-diffusers-folder hybrids, and z_image's loaded-format-dependent branch. Dequant-on-save done 3 ways; the isinstance(v, QTensor) variant (chroma, flux2, boogu_image, ideogram4) misses torchao and Ostris weights entirely. Every save_pretrained override ignores its save_dtype argument.
• Registry: linear scan in toolkit/util/get_model.py, silent SD1 fallback on a typo'd arch, eager import of every model file at startup. Second unsynchronized registry in ui/src/app/jobs/new/options.tsx.

Decisions (locked in)

1. Save format = ComfyUI format. Single-file safetensors in comfy key layout. Must support saving quantized — primarily convrot8 and nvfp4 (comfy_quant marker format, see toolkit/util/comfy_quant_import.py) — and plain bf16, all in comfy format. Loading stays backwards compatible: diffusers dirs, transformers repos, and single files all still digest through load_model; only saving standardizes on comfy.

2. v2 folder layout mirrors the comfy save path structure:

   toolkit/models/v2/
     _mixin.py            # base module (OstrisModelMixin, evolving)
     resolver.py          # comfy-layout weight resolution (lift from minimax_h3)
     diffusion_models/    # one file per DiT/unet family
     text_encoders/       # qwen3_vl.py, qwen3.py, t5.py, clip.py, gemma.py, ...
     vae/                 # flux_kl.py, qwen_image.py, wan.py, audio VAEs, ...
     vision_encoders/
   

3. Method names win from BaseModel: get_transformer_block_names and get_quantization_exclude_modules. The mixin's get_quantization_block_names gets renamed to match; resolve the classmethod-vs-instance-method mismatch while doing so.

4. Loading policy:

   • Per-model special handling is allowed via the hook methods.
   • If name_or_path is a diffusers/transformers source, load it with diffusers/transformers for now. Step 1 is migrating every model to the v2 module format and loader without breaking anything — same weights, same sources, same results.
   • Each model declares a comfy_weight_names dict keyed per standard name_or_path. If the user points at a local folder or a non-standard repo, load it as-is. If name_or_path is the standard repo and we have matching comfy weight names, load those instead when any of them exist (locally under MODELS_PATH in comfy layout, or downloadable to there).
   • Eventually the default flips to comfy weights / our own prequantized releases for everything.

Base module: what OstrisModelMixin still needs

The mixin already handles: diffusers dir / hub repo / local single file / org/repo/file.safetensors, key-conversion hooks on load and save, overridable backend hooks for transformers-lib models, block-wise quantize.

To add:

• Comfy weight spec + resolver. aitk_comfy_repo / aitk_comfy_weight_names class attrs + find_comfy_weights (local-only until Phase 2); resolution chain generalized from minimax_h3._resolve_comfy_file into v2/resolver.py: explicit override → MODELS_PATH at the repo-relative comfy path → flat at root → recursive walk of the category folder → hub download to the repo-relative path (folder stays shareable with ComfyUI, no duplicate downloads).
• Automatic prequantized import. Single-file path sniffs comfy_quant markers and routes through import_comfy_quantized_layers before load_state_dict, including the OstrisLinear missing-key whitelist that minimax_h3 and ltx2 each hand-rolled.
• One save path. save_model(path, dtype): dequantize via dequantize_if_quantized (honors dtype), run convert_state_dict_on_save, write single-file comfy-layout safetensors. (Quantized-storage saves — convrot8 / nvfp4 with comfy_quant markers — land with Phase 2; diffusers-folder save as an explicit flag still to add.)
• Tokenizer/processor declaration for text encoders (aitk_tokenizer_repo/aitk_processor_repo + load_tokenizer/load_processor).
• Rename quantization hooks to the BaseModel spellings (decision 3): get_transformer_block_names (classmethod on the module).

Migration steps

Track progress here; check items off as they land.

Phase 0 — foundation (done 2026-08-27)

• Evolve _mixin.py per the list above (comfy spec local-only until Phase 2)
• Create v2/diffusion_models/, v2/text_encoders/, v2/vae/, v2/vision_encoders/; move v2/z_image.py → v2/diffusion_models/z_image.py
• Lift the comfy resolver out of minimax_h3 into v2/resolver.py; point minimax_h3 and ltx2 at it (delete their copies)
• BaseModel default convert_lora_weights_before_save/load doing the transformer. ↔ diffusion_model. rename, gated on the class attr lora_keys_use_comfy_prefix (default False, so passthrough models keep their behavior); the ~18 identical overrides replaced with the flag. Custom conversions (anima, hidream_o1, ltx2, wan21) keep their overrides; ltx2's now composes with the flag via super().

Phase 1 — migrate all models to v2 modules, no behavior change

Every arch's components become v2 classes; if name_or_path is diffusers, it still loads via diffusers. Nothing about sources or outputs changes yet. Suggested order (worst duplication first), each including its loading test (see Testing):

• text_encoders/qwen3.py — Qwen3TextEncoder + OstrisTransformersMixin backend + BaseModel.prepare_text_encoder policy helper; the 3 verbatim TE stanzas (z_image, z_image_l2p, zeta_chroma) replaced. Verified with real Z-Image weights (load + encode on GPU).
• text_encoders/qwen3_vl.py — Qwen3VLTextEncoder with drop_vision_tower / patch_vision_patch_embed; the 4 identical patch_qwen_vl_patch_embed copies (krea2, mageflow, boogu_image, Qwen3VLCaptioner) consolidated; TE loads migrated in krea2, mageflow, nucleus_image. Still on their own paths: ideogram4 (loads via AutoModel), minimax_h3 (custom truncated/prequantized comfy load — port later), qwen_image (Qwen2.5-VL, needs its own class)
• text_encoders/t5.py, text_encoders/clip.py — T5TextEncoder, CLIPTextEncoder, CLIPTextEncoderWithProjection; migrated chroma ×2, flux_kontext, f_light (T5 stanzas → prepare_text_encoder, fixing their qtype → qtype_te bug) and hidream (CLIP ×2 + T5 with subfolder overrides; slow-tokenizer classes preserved via use_fast=False)
• vae/qwen_image.py — QwenImageVAE + QwenImageVAEHolderMixin (frame-dim + latents mean/std handling built in, tiling opt-in via vae_decode_tiled_on_low_vram); the triplicated encode/decode deleted from qwen_image, nucleus_image, krea2 and all three VAE loads routed through the v2 loader
• vae/autoencoder_kl.py — KLVAE (diffusers AutoencoderKL through the universal loader); migrated the scattered loads in chroma, flux_kontext, f_light, hidream, z_image
• vae/flux2_kl.py — the BFL-style Flux2 KL autoencoder unified from the flux2 + ideogram4 copies (both files deleted; flux2's encode/decode/small-decoder superset + ideogram4's diffusers key converter). Verified bit-identical to both originals (weights, encode/ decode outputs, converter mapping) and round-tripped real ae.safetensors weights on GPU. Packing/normalization stays per-model — flux2 packs (c pi pj) with BatchNorm running stats, ideogram4 packs (ph pw c) with its latent_norm tables; the conventions are incompatible.
• z_image — transformer, TE (qwen3), and VAE (KLVAE) all on v2 modules. z_image_l2p still has its local progressive-transformer subclass (rebasing it onto the v2 class deferred; its TE is migrated)
• qwen_image family — v2/diffusion_models/qwen_image.py (single-file loads stay on diffusers' from_single_file until the comfy flip) + v2/text_encoders/qwen25_vl.py (slow tokenizer preserved); edit variants inherit
• nucleus_image — v2/diffusion_models/nucleus_image.py, TE stanza collapsed to prepare_text_encoder
• krea2, ideogram4, mageflow — DiTs on the mixin via the config= passthrough (holder builds config from model_kwargs/holder state, mixin does build/markers/whitelist/casting; plain nn.Module classes now work with the default builder). krea2 + ideogram4 verified by harness; mageflow untestable while its repo 404s
• chroma, chroma_radiance — both vendored Chroma classes now carry OstrisModelMixin with the block-count sniff moved into a new aitk_config_from_state_dict hook (mixin now supports checkpoint-derived configs + load_from_state_dict for non-safetensors sources, used by radiance's .pth path). zeta_chroma transformer left as-is: its config depends on holder state (patch_size), not the checkpoint
• flux_kontext — v2/diffusion_models/flux.py (FluxTransformer2DModel); whole model now loads through v2 (transformer, T5, CLIP, KLVAE)
• flux2 + zeta_chroma DiTs on the mixin via config= passthrough (flux2_klein_4b verified by harness). Every arch's DiT now loads through the mixin except: ltx2 family (one-file→two-modules split, helper delegated), anima (diffusers modular pipeline), ace_step (bundled single-file loader), z_image_l2p's local subclass, and the grandfathered legacy stable_diffusion_model archs
• minimax_h3 (+ ref2va) transformer ported to the mixin: config sniffed from the checkpoint via aitk_config_from_state_dict (adaln_t_table), marker attach + stored-precision load via the new aitk_cast_on_load = False knob. Verified on the real pruned convrot file: 200 ConvRot linears, pruned table detected, fp32/fp16/bf16 mix preserved, no meta leftovers. Its TE stays custom (50-layer truncation + key_map). ltx2.5's _load_quantized_module now delegates to the mixin's whitelist/meta helper (~30 lines deleted); its full port is blocked on the one-comfy-file → transformer+connectors split, which doesn't fit the per-class single-file shape — revisit with the live server's component model
• wan21 / wan22 family — v2/diffusion_models/wan.py (WanTransformer3DModel, both wan22 dual loads included) + v2/text_encoders/umt5.py (UMT5TextEncoder + PatchedT5Tokenizer; loaders/umt5.py is now a thin compat shim, comfy_files still reserved for Phase 2 — no local comfy umt5 file to verify the key conversion against). wan21's TE qtype → qtype_te bug fixed via prepare_text_encoder
• hidream family — vendored transformer carries the mixin; v2/diffusion_models/hidream.py wraps the diffusers class for hidream_e1; both load via the switchable hidream_transformer_class through load_model
• omnigen2 — vendored transformer carries the mixin, load migrated
• boogu_image, ernie_image, prx_pixel_t2i — their vendored diffusers-style DiT classes now carry OstrisModelMixin (subfolder + block names on the class) and the holders load via load_model
• f_light — DiT class carries the mixin (aitk_subfolder="dit_model"), load migrated
• anima — loads through diffusers modular pipelines (AnimaModularPipeline); not a mixin fit, revisit at Phase 2
• flux2 DiT — holder-config params classes (Flux2/Klein variants), defer like krea2/mageflow
• ace_step — one bundled safetensors holds model+TE+VAE+tokenizer via its own load_models; decomposing into v2 components is its own task
• Per-model fixes folded in as each migrates: qtype_te bug, dequant-on-save (dequantize_if_quantized everywhere), raw-quantize() → quantize_model()

Phase 2 — comfy weights become the preferred source

Decisions:

• Comfy weights come from the Comfy-Org hub repos (per-model repos, comfy layout nested under split_files/ — stripped when placing files into MODELS_PATH). Repos ship several precision variants of each component.

• Selection preference: convrot8 > float8 mixed > float8 > bf16 > fp16 (resolver.comfy_precision_rank; nvfp4/unmarked rank last and are only used when explicitly listed). Local-first: the best-ranked LOCAL candidate wins; only when no candidate is local is the best-ranked one downloaded.

• Per-model candidate lists (aitk_comfy_weight_names) hold only the variants the class can actually digest. Constraint discovered: comfy convrot/quantized files carry markers on the ORIGINAL module layout (e.g. z_image's fused attention.qkv) — diffusers-layout classes with split modules can't attach them until they grow fused-layout support; until then those models list bf16/fp8 variants only. (Vendored comfy-layout classes — minimax/ltx pattern — take convrot directly.)

• The standard repo still supplies the config; local dirs and unregistered repos load as-is; model_kwargs.use_comfy_weights: false opts out.

• Mechanism: resolver.comfy_precision_rank / comfy_local_rel / resolve_comfy_candidates + OstrisModelMixin.resolve_comfy_weights, integrated into load_model (comfy file preferred for registered standard repos, downloaded into the shared comfy layout)

• First wired model: z_image (Comfy-Org/z_image_turbo, bf16 candidate). Verified end-to-end against the real shared ComfyUI folder (MODELS_PATH=/mnt/Models/comfy_models): standard-repo name_or_path resolved to the locally-present comfy file and produced the identical generation to the diffusers-shards load

• qwen_image wired: its comfy files use the diffusers key layout directly — fp8mixed (float8-mixed, rank 1) attaches its 839 float8_e4m3fn markers straight onto the class; candidates fp8mixed → fp8_e4m3fn (raw cast) → bf16. Verified with real weights: loaded the shared folder's local fp8 file (local-first, no download) and generated correctly. Holder skips re-quantization for prequantized checkpoints.

• New float8_e4m3fn Ostris backend (toolkit/util/float8_quant.py): ComfyUI's fp8 + per-tensor-scale storage with dequantized matmul, in get_ostris_quantizer + comfy import/export. Round-trip verified.

• wan family wired: comfy wan files (original key layout) convert via diffusers' own convert_wan_transformer_to_diffusers (rename-only, so quantized weight/scale keys ride along with their modules). Candidate keys support (repo, subfolder) tuples for wan2.2 A14B's dual DiTs (transformer = high noise, transformer_2 = low noise) and per-entry comfy-repo overrides ({"repo": ..., "files": [...]}) since wan2.1 and 2.2 files live in different Comfy-Org repos. Wired: 2.2 TI2V-5B, T2V/I2V-A14B (fp8_scaled), 2.1 T2V 1.3B/14B, I2V 480P/720P. Verified with real weights: wan21 1.3B (downloaded comfy bf16) and wan22 5B (local comfy fp16) both load through the converter and generate video. Fix along the way: the mixin's meta build now uses accelerate init_empty_weights (params meta, buffers real) so init-computed non-persistent buffers like wan's rope tables materialize.

• Legacy ComfyUI scaled-fp8 support (scaled_fp8 marker + per-layer fp8 weight / scalar scale_weight, e.g. every wan *_fp8_scaled file): imports onto the float8 backend; scale_input (activation quant) is dropped, matmuls run dequantized.

• wan comfy-format saves: convert_state_dict_on_save inverts diffusers' rename table (base/t2v/i2v; vace/animate excluded — their reverse mappings collide). Round-trip verified on both real comfy files (exact; the 2.1 file's legacy model.diffusion_model. prefix drops per the modern convention) and with real weights (load → save → 825-key original-layout file → reload bit-equal). wan21 + wan22_5b save one comfy file; wan22_14b saves the comfy-standard _high_noise/_low_noise pair instead of two diffusers folders.

• Wire remaining archs' candidate lists (chroma/others as their key conversions are verified per file)

• Fused-layout quantized attach for diffusers-split classes: split_fused_quantized_keys / fuse_split_quantized_keys (comfy_quant_import) do exact out-dim row surgery on quantized comfy entries for all three formats (int8 rows+scales slice; fp8 scalar and nvfp4 per-tensor scales shared; nvfp4 block scales unswizzle→split→reswizzle). z_image's load/save converters use them, so its convrot8 candidate is live and top-ranked. Unit-verified exact both directions.

• Comfy-format save: save_model auto-keeps quantized storage (comfy_quant markers) for convrot8 / nvfp4 / convrotcomfyw4a4 layers via toolkit/util/comfy_quant_export.py (inverse of comfy_quant_import; nvfp4 nibbles re-swapped + scales re-swizzled to the cuBLAS tile layout), plain layers save at bf16; partially-exportable models fall back to dequantized. Round-trip verified: save → mixin reload → outputs match for convrot8, nvfp4, and plain layers.

• Save unification started: z_image and qwen_image holders now save comfy-format single files via the mixin regardless of how they loaded (z_image's dual-style branch deleted). Real round trip verified: the published z_image int8_convrot file loads (270 quantized linears, split-attach), resaves to the IDENTICAL 857-key comfy layout with bit-exact fused qkv weights/scales/markers, and the reload's quantized forward is bit-identical — toolkit saves are byte-compatible with ComfyUI.

• chroma + chroma_radiance saves flipped to the mixin (their class keys ARE the original layout) — also fixes their quanto-only dequant bug (torchao/Ostris weights now dequantize on save). Tiny-model round trip verified. Save flips so far: z_image, qwen_image, wan21, wan22_5b, wan22_14b (dual files), chroma ×2.

• flux_kontext comfy wiring deferred: its Comfy-Org repo ships a single legacy-fp8 file in fused BFL layout — needs the flux fused-split conversion (split_fused_quantized_keys pattern + BFL↔diffusers maps)

• Flip the remaining per-arch save_model overrides as each arch's save-side key conversion is in place

• Publish/verify comfy repacks per model as they flip

Phase 3 — live server

• Component-level identity (which TE/VAE instances are shared between archs) so a model switch drops only what the next run doesn't need
• Resident process: request comes in → diff requested components vs loaded → unload/load the difference
• Legacy stable_diffusion_model.py archs: grandfather or port last

Testing

• testing/test_model_loading.py: per-arch load + one small sample through the normal training-style flow (get_model_class → load_model → generate_images). --arch X runs one in-process; --all runs every registered arch in its own subprocess (full unload between archs). 15 archs registered so far — add each model type as it migrates.
• Missing weights skip rather than fail: default is HF_HUB_OFFLINE=1 and hub/file errors classify as SKIP; --allow-download opts into fetching. (GPU + local-weights test, not CI-portable.)
• Final certification sweep (2026-08-27, post-polish): 14/14 runnable archs PASS — comfy-source loads (zimage convrot8, qwen fp8, wan ×2 + fp8 umt5 TE), all ported holder-config DiTs, and the migrated quantize_model paths (chroma, flux_kontext, f_light block-streamed) in one run; mageflow remains the upstream 404 skip. One regression caught and fixed: qwen's _load_single_file override needed the new config kwarg.
• Full sweep run 2026-08-27: 14/15 PASS (zimage, qwen_image, krea2, boogu_image, ernie_image, ideogram4, hidream_o1, anima, wan21, wan22_5b, chroma, flux_kontext, flux2_klein_4b, ltx2.3 — the quantized 22B ltx stack doesn't fit 32GB, needs the 96GB card). mageflow blocked upstream: microsoft/Mage-Flow-Base 404s on the hub (cached locally, so it runs offline — recheck whether the repo moved/went private).
• Registry carries realistic per-arch sample settings (native res, steps, CFG) so sweep outputs are visually verifiable, not just "a file exists". Verified: all 14 produce proper generations. Findings from the quality pass: boogu emits a black frame below native res at low-step/high-CFG (settings regime, present pre-restructure, not a migration bug); chroma's FakeCLIP hardcoded device 'cuda' broke any non-cuda:0 run (pre-existing, fixed — FakeCLIP now takes the real device); ideogram4's fp8 release renders its own "blocked by safety filter" card for a plain cat prompt (model behavior, not a bug — investigate its trigger).
• Round-trip verified for the first comfy-save arch: z_image convrot load → comfy save → identical key set + bit-exact quantized entries vs the published file → reload → bit-identical quantized forward. Extend per arch as saves flip.
• Each newly migrated model adds its test in the same PR as its migration.

TODO / look at later

• Quantize consolidation: quantize_model now honors quantize_kwargs (blocks + extras) and tolerates missing block names; the chroma ×2, flux_kontext, f_light, omnigen2 raw-quantize sites migrated onto it (gaining block streaming, excludes, ARA, dequant-on-save patching) with holder block names added. Remaining raw sites are legacy/extension (flex2, cogview4, stable_diffusion_model). The ARA uint8 hardcode stands — revisit if a non-uint8 ARA base is ever wanted.
• Last known qtype_te bugs fixed (flux2's Mistral TE, anima's text_conditioner) — 9/9 sites from the survey now correct outside the grandfathered legacy monolith (cogview4/legacy SD remain as-is).
• wan comfy-TE resolved for real: UMT5TextEncoder carries comfy candidates (fp8_e4m3fn_scaled via the legacy importer, fp16), files already in transformers key layout (spiece blob dropped, tied embed_tokens materialized). Verified: wan21 samples with the local comfy fp8 TE. The loaders/umt5.py comfy_files param stays as a no-op shim for old callers.
• Registry hardening: unknown archs now raise with the known-arch list (legacy monolith archs whitelisted via LEGACY_ARCHS). Still open: lazy per-arch imports; single source of truth shared with the UI's options.tsx model list.
• Stub dedup where identical: chroma_radiance imports FakeCLIP/FakeConfig from chroma_model. The other Fake* copies (hidream_o1, flux2, zeta) carry model-specific values — left in place.
• Vendored upstream code (hidream/src, omnigen2/src, ltx2 converter's private comfy-quant parser): dedupe against toolkit utils where practical.