The remaining design_v3 probes (all except 8b speculative decoding). All fit with no new runtime
primitive (148 tests pass).
#6 LTX-2 joint audio+video (§9.11) — LTX-2 declared an audio_vae required_for t2vs but never used
it; now a single 2-stage denoise carries a synchronized audio latent (conditioned on video),
applies per-modality CFG (guidance_per_modality), and decodes via video VAE + audio VAE → video +
audio. Gated on requesting audio, so the T2V path is byte-identical (existing tests untouched).
ToyAudioVAE; build_ltx2_av_program. 5 tests.
#4 Live weight-sync under in-flight serving (§9.14) — WeightSyncController makes the freeze → drain →
transfer → bump version + invalidate → resume lifecycle explicit. Tests: a mid-flight swap corrupts
(the hazard); draining first leaves the in-flight request bit-identical to baseline while a
post-sync request reflects new weights; transformer-only sync, so the frozen text-encoder cache
survives. The RL flywheel's hardest correctness. 3 tests.
#5 Reward-model-as-a-served-card (§9.15) — a reward model is a card (scorer + a score loop emitting
REWARD_BATCH units); ServedRewardScorer drop-in-replaces the numpy scorer so any RL method becomes
RLHF/RLAIF with no method change. ToyRewardModel; models/reward/. 4 tests.
#7 Content-adaptive control flow (§9.12) — CacheDiTDenoiseLoop (isolated WanDenoiseLoop subclass)
reuses the cached velocity when predictions barely change (cache-dit skip) and early-exits on
convergence — variable step count; interleave parity holds across ragged loops. models/adaptive/. 4 tests.
#8a Nested workflows (§9.13) — a workflow stage can invoke another workflow (engine.run routes ids);
requires/validate recurse; cycles caught at registration + a run-time guard (engine._wf_running).
build_t2i_i2v_extend_workflow. 5 tests.
designv4 §9.11–§9.15 + falsifier/layout/closing updates (148 tests, 25 files). Also removed a
pre-existing unused import in ltx2/loop.py.
Answers "what's the right way to name/register custom pipelines like T2I→I2V":
treat a Workflow like a card — a stable namespaced id in the same servable
namespace, declared dependencies, and a two-level registry. No new concepts;
mirrors how cards are registered (and vllm-omni's pipeline_registry).
- program/workflow.py: Workflow gains `requires` (the cards it composes, derived
from stages) and `validate(engine)` (fail-fast if a required card is absent,
P7). New WorkflowRegistry: declarative workflow_id -> builder catalog for
out-of-tree/ad hoc use.
- runtime/engine.py: `_workflows` registry + register_workflow (validates deps,
rejects id collision with a model_id) + serves(); engine.run routes a request
whose model_id is a workflow to workflow.run — addressable exactly like a model.
Single-model hot path untouched.
- runtime/async_engine.py + serving/server.py: serves() and /models include
workflows (discoverable as servables).
- models/__init__.py: declarative `_WORKFLOWS` catalog (the cross-model analog of
_BUILDERS) + register_workflows() helper; build_image_video_engine now registers
the workflow too. Adding a custom pipeline = one catalog line.
- Naming convention: dotted/namespaced workflow_id (`image_video.t2i_i2v`),
distinct from kebab model ids, collision-checked. Renamed from `t2i_then_i2v`.
- tests (+5, 12 total in the file): addressable by id, requires/validate, id
collision, registry catalog, register_workflows helper. Full suite 114 passed.
- designv4 §9.6: the naming & registration convention documented.
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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