record(LTX25-RESOLUTION-ENVELOPE): 704x448/25f completes, and the size the page said could not (#1088)

[localai-bot]

Closes #1088.

docs/USAGE.md published 448x256 at 25 frames as "Measured NOT to complete", with the reason that its decode loses about 59 GB in 24 s. Two renders on dgx.casa on 16 to 17 August 2026 against main 0b0b8900f completed that geometry in 3085 s and completed 704x448 at 25 frames in 4231 s. The page now records the newer envelope, and docs/BENCHMARKS.md no longer says the opposite of it in a cell a reader meets first.

What was measured

Container vllmcpp-build:gb10, Release, VLLM_CPP_CUDA=ON, arch 121a, TRITON=ON, CUTLASS absent so FlashAttention-2 was not built, which is like for like with the earlier renders. VLLM_CPP_CPU_THREADS=20, NVFP4 transformer, no --allow-unported. 0b0b8900f carries #1041 threaded decode, #1032 T2A and #1036 f32 decode accumulators.

Geometry	Result	Wall
448x256 / 25 frames	completed	3085 s
704x448 / 25 frames	completed	4231 s
1024x576 / 25 frames	not attempted to completion, another session claimed the box	n/a

The ~59 GiB cliff did not recur under a 2 s memory guard that would have seen it: MemAvailable floors of 38.96 GiB over 1289 samples at 448x256 and 38.89 GiB over 1743 samples at 704x448, zero samples under 34 GiB on either, peak use of 80 of 119 GiB, and no reboot.

The 704x448 artifact was verified rather than inferred from an exit code: 25/25 distinct frame md5s, 0 near-uniform and 0 near-black frames, adjacent-frame mean absolute difference 4.381 against a uniform-noise reference of 85.3 on the same shape, 0/24 zero-motion pairs, and audio at 48 kHz stereo, 1.010 s, -37.29 dBFS, 20/20 windows above threshold. The mp4 lives at benchmarks/media/ltx25-704x448-25f-audio.mp4 on the render host and is gitignored by .gitignore:35, so it is not committed here.

What is not claimed

One run per geometry on a contended shared box with no oracle on either side. Two points establish no scaling law. 704x448 is not published as a ceiling: the next rung up stopped because another session claimed the box, not because of memory or an envelope. The page says all of this in its own words.

The 59 GB is kept, not deleted

It is the reason the old row gave, so deleting it would remove the evidence the newer result is measured against. It stays attributed to its own run, which is rung F1 in .agents/benchmark-record.md: a prompt-embeds render with no text tower that an armed watchdog ended at 13.77 GiB against an 18 GiB floor, rather than the engine failing. Attributing the fall is still #1014, and this change does not close it.

The dominant cost moved off the decode

docs/USAGE.md said most of a 320x192/25f render is spent in the host VAE decode. After #1041 threaded that decode, the dominant cost is a resolution-independent phase of about 1731 s, measured at 1731 s and 1732 s across two rungs whose voxel counts differ 2.75x, which is 57 to 66% of wall. That is #1087, which owns naming the phase. The sampler classified by CPU-time rate rather than by symbol, so what is measured is a duration and a scaling law and not a function, and the page says so.

Files

Record	Edit
docs/USAGE.md	envelope table rows, the paragraph under it, the bounded-by paragraph, and the #1009 paragraph's stale "has not been re-measured" clause
docs/BENCHMARKS.md	the LTX-2.5 axes row, edited in place as two table cells, 208 and 214 characters against MAX_CELL_CHARS = 220, so no prose paragraph is added to a page sitting at 35 of 35
.agents/specs/ltx25-resolution-envelope.md	new section 4.1 recording what superseded section 4, and the ## Owed bullet that section 4 wrote
.agents/issue-index.md	one row appended for #1088, zero rows edited, zero removed

Evidence

Records only. No src/, include/ or tests/ change, so no build was run and none is claimed.

Key-by-key proof, taking HEAD's version of each file and reapplying the scoped edit:

Record	Keys in base	Keys now	Unrelated keys byte-identical	Changed	Added	Removed
docs/USAGE.md	205	206	203 of 203	**Measured to complete on one GB10**	Largest size tried, Superseded, kept for the record	Measured NOT to complete
docs/BENCHMARKS.md	190	190	189 of 189	LTX-2.5 axes	none	none

Issue index, the three verifications the append-only rule needs: the base file is a byte-identical prefix of the new one, the addition is exactly one line whose sha256 is 65933626d961a41b…, and the file has 290 rows against 290 unique issue ids. The union driver was never allowed to resolve anything: the file was rebuilt as base bytes plus the row.

Checkers, each with a red control observed on the same tree before the green was believed:

Checker	Result	Armed control
check-doc-checkpoint.py --staged and --commit cedb85eb1	0	--commit b5618b305 exits 1, "changed user_usage but did not update docs/USAGE.md"
check-public-doc-tables.py	0	padding the new cell past 220 characters exits 1 at line 487, "table cell of 333 chars exceeds 220"
check-issue-index-append-only.py --base origin/main	0	committing a deletion of the #168 row exits 1, "this range removes or edits lines"
check-agent-record.py	0	replacing the new row's owning row with a dash exits 1, "34 rows name no owner, above the recorded 33"
check-commit-style.py --range origin/main..HEAD	0	an empty commit whose subject ends in a period exits 1
check-commit-trailers.py --range origin/main..HEAD	0	an empty commit with no trailer block exits 1 on three lines
check-pr-size.py --base origin/main --head HEAD	0	n/a, no control run

Every tree mutation was restored and the restored file re-hashed to the pre-mutation sha256 before the next step. The key proof itself was seen red first, on an expectation that omitted the one key the change does edit in place, so its green is not a tautology.

scripts/agent-preflight.sh --staged and scripts/agent-ready.py both report All gates green on 21544efd9. agent-ready then exits 1 only on expected exactly one live PR for row/LTX25-ENVELOPE-RECORD; found 0, which this pull request is.

origin/main advanced twice during this work, to e9dfa6319 and then 9143196c7. Both were merged in and every checker re-run afterwards; the second merge is the merge commit on this branch, and its message carries the trailer block because the range gate caught that it did not.

What could not be verified

The first scripts/agent-preflight.sh run exited 1 on test_cpu_x86_llamacpp_floor, on the unmodified tree before any edit in this branch. Its own output names the cause: load=120.50, so the harness discarded the contended leg and returned NO_QUIET_WINDOW (4) where the case expects GIVING_UP (2). That is #618. It passed on the later runs once the box quieted, so this branch has no evidence of that case being sound, only of it being load-dependent as #618 already says.

The renders themselves were performed by another session and are reported here from its results. This branch did not run them, holds no GPU, and did not rebuild anything.

.agents/specs/ltx25-decode-speed.md and .agents/benchmark-record.md also discuss the 448x256 rung. Neither is edited here: the decode-speed spec already records that the "inside the decode" half of the old sentence is unsupported, and the benchmark record is an append-only log of what each run observed, which stays true of the run it describes. Reconciling the investigation spec against the new rungs belongs to #1087, which owns the phase.

FOLLOWING_AGENTS_PROTOCOL

Following-Agents-Protocol: true
AI-Assisted: true
Assisted-by: AGENT:claude-opus-5 [claude-code]