record(MODEL-DIFFUSION-LTX25): the first render on the full 21.004 B DiT, and the 1024x576 rung it could not fit (#1375)

[localai-bot]

Every LTX-2.5 artifact until now was rendered on the distilled arm. This records
the first on the full ltx-2.5-22b-dev-transformer-bf16.safetensors (42,018,190,584
bytes, 4349 tensors, 21,004,025,600 elements): 768x448/25f on GB10 in 2990 s, 25
frames plus 1.01 s of 48 kHz stereo, verifier PASS on both the pixel and audio
arms. Binary 0a43a750 built from 7b9e207b1, run 20260819T150230Z.

The verifier numbers rather than its verdict: 25 distinct frame hashes of 25,
zero near-uniform and zero near-black frames, adjacent-frame MAD 2.01 against
far-frame MAD 9.34 (ratio 0.215, where uncorrelated noise gives ~1.0), audio RMS
-15.63 dBFS, envelope CV 0.112, spectral crest 52.0.

The same lease REFUSED 1024x576/25f, and that contrast is the result rather than
a failure beside it. The governor measured first_dit 481.5 s and 162.0 s per
forward from 7 resolved forward starts, so the recipe's fixed 60 forwards plus a
600 s tail project 10803 s against that rung's 7153 s budget. The 60 is not
tunable: one_stage at model version 2.5 resolves to 30 inference steps
(ltx2_pipeline.cpp:968) and a non-unit cfg_scale forces an unconditional
forward per step (ltx2_pipeline.cpp:521-523), so the ceiling is geometry
against lease length. That per-forward measurement is issue #1375.

What it is not is recorded with it. Ltx2DitForwardDevice takes no
perturbations argument, so the device-resident arm refuses the perturbed and
isolated-modality passes by name (ltx2_video.cpp:2738-2749, issue #1092), while
LTX-2.5's own params carry stg_scale 1.0 and modality_scale 3.0. The run used
the engine's own sanctioned escape and kept real classifier-free guidance (video
3.0, audio 7.0) while giving up the STG and isolated-modality terms. No oracle
ran against it, so the speed axis stays PENDING and no parity claim is made.

Two instrument facts ride with the number because both have already produced a
wrong reading elsewhere. gpu_edges = 0 means saturated rather than idle: the
counter needs a busy-to-idle transition, and that rung sat above 50 per cent
utilisation in 2704 of 3191 samples. And eu-stack resolves no frames in the rc
worker container, so phase attribution came from the cpu and rss signature
instead of from symbols.

Reachable at all only because of issue #1252. Before it, the caption projection
was a scalar triple loop with a double accumulator that could not reach an f32
FMA; runs on the pre-fix binary measured single-core stretches of 1740 s and
1738 s, 0.11 per cent apart, reproducing the figure in issue #1087 twice in one
render. After it, the same phase appears as first_dit 481 s.

Three files change and all three are additions only: the entry in
docs/BENCHMARKS.md, its forensics and reproduce recipe in
.agents/benchmark-record.md where the public table's own checker directs detail
that does not fit an entry, and the append-only index row for issue #1375.

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Assisted-by: AGENT:claude-opus-5-1m [Claude Code]