Sweep all 296 v2 modules: simplify verbose docstrings/comments and remove 376 dangling
"(design_vN §X)" citations to the now-deleted design docs (v2/README.md is the source of
truth). Comment/docstring-only — AST-verified code-identical; the CPU suite holds at 237
passed / 5 pre-existing. Also applies yapf + ruff --fix auto-fixes (import ordering,
forward-ref annotation de-quoting under `from __future__ import annotations`; behavior-
neutral, suite-confirmed) and adds the legitimate domain terms mot/clen/te to the codespell
ignore-list. Remaining ruff (24) + mypy (68 no-untyped-call) findings are pre-existing v2
debt, untouched here.
Two distilled few-step video models rendered incorrectly on GPU; root-caused via
dense frame sampling (contact sheets) and fixed in the recipe cards.
SF-Wan2.1 (self-forcing causal, wan_causal card): was oversaturated/overcooked.
The distilled student is CFG-FREE (guidance 1.0, single forward/step) and denoises
with the 4-step DMD schedule [1000,750,500,250] (warped by FlowShiftPolicy(5.0)),
at a native causal block of 3 latent frames. Defaults were ClassicCFG@6.0 + 2 steps
+ block 2 -> overcooked AND under-denoised. Fixed: num_chunks=7, chunk_size=3,
steps_per_chunk=4; SamplingDefaults num_steps=4, guidance_scale=1.0 (7x3=21 latent
-> 81 frames). Renders a clean raccoon-in-sunflowers across all 81 frames.
LTX2-Distilled 2-stage SR (ltx2 card + LTX2VAE): was temporally blocky. Root cause
was an OOM-forced 57-frame reduction (only 8 latent temporal frames); the model is
designed for 121 (16 latent frames). Enable VAE tiling in LTX2VAE so the 121-frame
full-res decode fits the 80 GiB GPU; keep base cfg_scale=3.0 (drives brightness;
cfg=1 washed out) with stg_scale=0.0 (v2's drop-text perturbation is not real
skip-layer STG). Renders the on-prompt backyard shot, bright + temporally coherent.
torch_backend.py: enable LTX2VAE tiling; clear pre-existing mypy no-untyped-call /
yapf debt on the file (surfaced once per-file linting bypassed the duplicate-module
flakiness) by annotating the helper/constructor/maker signatures.
Tests: update the 3 affected CPU defaults/chunk-count tests. v2 mini: 240 passed.
Frees v2/models/ to become the vendored-architecture namespace that mirrors fastvideo/models
(part of making v2 self-contained / able to replace fastvideo). The v2 recipe layer (per-family
card.py/loop.py/program.py + common.py + the build_*_engine re-exports) is the recipe, not the
architectures, so it moves to v2/recipes/. The pure-numpy toy/parity implementations (ToyDiT etc.)
move from v2/models/backend.py to v2/platform/backends/toy.py (alongside cpu.py/accel.py/torch_*).
Mechanical: all imports are absolute, so v2.models.<x> -> v2.recipes.<x> and v2.models.backend ->
v2.platform.backends.toy across v2/ + examples/ (89 files, 178 refs). No behavior change.
CPU mini green (202 passed, 2 skipped); all v2 files compile.
Addresses the 'how is ltx2 separate from ltx2.3' confusion + a wrong capability:
- LTX-2 cards renamed by ARCHITECTURE (the version labels did not map to it): build_ltx2_card model_id
'ltx2.3-distilled' -> 'ltx2-2stage-distilled' (two-stage base->upsample->refine; serves the
upsampler-having FastVideo/LTX2-Distilled-Diffusers); build_ltx2_base_card 'ltx2.base' ->
'ltx2-single-stage' (one loop; serves Davids048 base + the single-stage FastVideo/LTX-2.3-Distilled,
which has NO spatial_upsampler). Dispatch already splits on has_spatial_upsampler. Updated the
model-id refs in the mini's tests/examples.
- Wan2.1 base is T2V-only: dropped the wrong Capability.IMAGE_TO_VIDEO + narrowed components'
required_for to {t2v} (i2v is the separate InP variant; v2 has no i2v path yet). build_wan21_card is
shared by wan21 + wan2.2-ti2v; the A14B card was already T2V-only.
- CPU suite green (202 passed, 2 skipped).
Directory rename (git mv, history preserved) plus rewrite of all references: absolute imports in
tests, the zero-dep runner, docstrings, comments, and the README. No behavior change.
Run: python3 -m pytest v2/tests/ -q ; python3 v2/run_tests.py ; python3 -m v2.examples
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