record(SPEC-DFLASH2): #1456's conclusion is retracted at the artifact, and the 0.8017 denominator inherits it (#1796)

.agents/issue-index.md

@@ -668,3 +668,4 @@ rather than merged. `scripts/check-agent-record.py` gates both.
 | [#1804](https://github.com/mudler/vllm.cpp/issues/1804) | `MODEL-MM-dots3-note-dots3-note-for-causal-lm` | **`.agents/specs/dots3-note.md` §4 item 6 read `is_neox_style=False` as belonging to the dots3-note SLIDING rope ONLY, and it belongs to both MLA ropes** — the sentence would have sent a W3 implementer to rotate the 13 full-attention layers split-half NeoX. `Dots3NoteSlidingAttention` does pass `is_neox_style=False` literally (`model.py:408` @ vLLM `origin/main` `c205726108df54bb6fbf15b19e725a4a3add2b18`), which is the half W0 read; `Dots3NoteFullAttention` (`model.py:219`) inherits the SAME hard-coded value from `deepseek_v2.py`::`DeepseekV2MLAAttention.__init__` (`:1093-1098`). So the two geometries do NOT differ on the RoPE layout at all — they differ on the THETA, `swa_rope_theta` 5e4 on 33 layers against `rope_theta` 8e7 on 13. The polarity that DOES flip is the INDEXER's, and that is §4 trap 2's point rather than item 6's: `deepseek_v2.py:1148` sets the indexer rope to `is_neox_style = not indexer_rope_interleave`, so at DeepSeek-V3.2's absent-key default the indexer runs NeoX beside an MLA rope that is GPT-J, and `indexer_rope_interleave = True` (`configs/dots3_note.py:23`) is what makes dots3-note's two agree. Being wrong in this direction is SILENT: the same 64 coordinates are rotated either way, so nothing changes shape and nothing throws — the §4 defect class exactly, on a row that spec §6.4 says has no oracle anywhere to catch it. FIXED IN FLOW on `row/MODEL-MM-dots3-note-W1`: §4 item 6 corrected in place and it says what it used to say (`main` is never rewritten), `ParseDots3NoteParams` resolves `rope_is_neox_style = false` on BOTH geometries with the two citations beside it, and `tests/vllm/models/test_dots3_note_scaffold.cpp` asserts both plus the indexer's agreement with them. The assertion was captured RED against the NeoX reading, on an arm that compiled and ran, before the corrected value existed | bug |
 | [#1802](https://github.com/mudler/vllm.cpp/issues/1802) | `BACKEND-CUDA-SM110` | **Re-measuring the sm_110 `ctest` baseline at `6756f9131` (2026-08-23, job `8bf39567-9334-4f7e-aa27-43a2aa867bb7`, artifacts `/mnt/nas_share/rc/thor-w05-955/out/`) found six names red that were green at `0764ded2b`, none with an owner**, plus two standing entries whose recorded cause no longer holds. Arrivals, all mode `Failed`: `test_cuda_ops` (`:106` `CHECK(bad == 0)` -> `6 == 0` and `7 == 0`, silu_and_mul vs CPU; also red on GB10 at 439/440 against 438/440 here, [#907](https://github.com/mudler/vllm.cpp/issues/907)), `test_backend_cross_device` (`:2063` MoeSiluMul and `:2601` MoE combine/gate vs the CPU oracle, 80205/80207), `test_llama_embedding_fold` (`:254` engine vs direct at `epsilon(1e-5)`), `test_mtp_depth` (`:738` `CHECK(st.capture_shapes == 0)`), `test_qwen3_dflash2_draft` (`:2574` `CHECK(r.generate_threw.empty())`), and `test_ops_attention_dense_fa2` (`:692` `CHECK(Mismatches(on, ref) > 0)` -> `0 > 0`, which reads as a TEST arch-assumption: the case asserts the knob-ON path DIFFERS from the scalar reference, and with `fa2` DISABLED for `[110]` they are the same kernel). Four of the six are CUDA-vs-CPU numeric comparisons off by about one ulp, so they MAY be one sm_110 difference wearing four names -- a hypothesis from the logs, not a measurement. Also folded in: `test_gguf_device_fit_reach`, red and unattributed since 2026-08-15 (`:463`, moved from `:278`, assertion unchanged); and `test_serve_low_tools`, whose `(name, mode)` pair never moved while its CAUSE changed completely -- `73ada0df8` (#1661/#1662) fixed the [#961](https://github.com/mudler/vllm.cpp/issues/961) guard so it skips, the string `shellcheck` appears nowhere in the run's log, and the failure is now four `tests/tools/test_dflash2_speed_harness.py` `ShellDriverTest` cases of 517. The CONTROL was rerun and now falsifies the old conclusion: the baseline reads `FAILED (failures=3, errors=1, skipped=1)` and the control with `shellcheck` 0.9.0 installed reads `FAILED (failures=3, errors=1)` -- the same four cases, differing only in the vanished skip. **That vanished `skipped=1` is a second proof**: the one test that skipped in the baseline is the `shellcheck` guard itself, so with the binary present it stopped skipping and PASSED, showing the instrument was the only thing the install changed. #961 was CLOSED COMPLETED on 2026-08-23 acting on that prompt -- `73ada0df8` fixed its guard while referencing the sibling filing #1661/#1662, which had left #961 orphaned rather than resolved. Not in scope here, because they have owners and did not worsen: the four FA-2 refusals, `test_platform`/`test_op_parity` hardcoding GB10, `test_linear_method` and the three `qwen3_5_gdn_spec_routing` tests (#907), the FP8 pair ([#1725](https://github.com/mudler/vllm.cpp/issues/1725), which improved `SEGFAULT` -> `Failed`), and [#962](https://github.com/mudler/vllm.cpp/issues/962), which reproduced byte-identically at `bitdiff=15/32768`. Table and diff in [`environment.md`](environment.md); the re-measure debt itself is [#955](https://github.com/mudler/vllm.cpp/issues/955) | bug |
 | [#1791](https://github.com/mudler/vllm.cpp/issues/1791) | `SPEC-DSPARK` | **`scripts/dspark-paired-e2e.sh`'s `settle()` can never break early, so a wait for the GPU to drain always spends its full 360 s however fast the box actually drains.** The same idiom as [#1734](https://github.com/mudler/vllm.cpp/issues/1734), found by sweeping `scripts/` for it: `grep -c .` with an `\|\| echo 0` fallback makes `$n` the two-line string `0\n0`, so `[ "$n" -eq 0 ] && break` answers `integer expression expected` and returns 2 instead of deciding. The BUSY half of the guard works -- a positive count exits 0 and the fallback does not fire -- so only the FREE half is dead, and the failure is in the safe direction, which is why it was paid in silence. This is the FIFTH diagnosis of the idiom in this tree: `scripts/cpu-x86-llamacpp-floor.sh` already carries the removal and the reason in a comment, and a comment in one file is not reachable from another. FIXED IN FLOW with #1734: `\|\| true` keeps grep's own `0` and swallows only its status. The recurrence gate is `TheIdiomIsGoneFromEveryShellScript` in `tests/scripts/test_ltx25_ab_memwatch.py`, which sweeps every `scripts/*.sh` for a counting `grep`/`pgrep` paired with an `\|\| echo` fallback outside a comment; run against `27d8bfa70` it names all three live instances, this one included. It is a TRIPWIRE and says so: it reads text, and a `wc -l` with the same fallback walks past it | bug |
+| [#1796](https://github.com/mudler/vllm.cpp/issues/1796) | `SPEC-DFLASH2` | **[#1456](https://github.com/mudler/vllm.cpp/issues/1456)'s conclusion is retracted AT THE ARTIFACT, off-GPU, and the DFlash2 speed ratio's denominator inherits the retraction: `0.8016987337853048` MAY BE FLATTERING US.** #1456 measured a real source build at `CUDA_ARCHS=12.0` emitting `sm_80` for `_vllm_fa2_C` and `sm_75` for `_vllm_fa3_C`, and concluded the GB10 oracle has no `FLASH_ATTN` denominator. **The arch measurement stands; the conclusion does not, and no lease was needed to show it.** Both staged oracle wheels were opened with `zipfile` and walked as fatbinaries on the CPU dev box: `0.1.dev1+g66e5414c6` (this row's oracle, `/mnt/nas_share/rc/oracle-dflash2/`) and `0.1.dev1+g555967922` (the parity pin, `/mnt/nas_share/rc/oracle-vllm/`) each carry 76 FA2 fatbinaries and 192 FA3 fatbinaries, and **every one holds a PTX image beside its SASS image** -- arch 80 for FA2, arch 75 for FA3. The first FA2 PTX payload is zstd and decompresses to `.version 9.0` / `.target sm_80` for `flash_fwd_hdim128_bf16_causal_sm80`. That is the `+PTX` half of `FA2_ARCHS "8.0+PTX"` and it is the mechanism by which the module CAN reach sm_121 -- the artifact establishes a necessary condition, forward-JITtable code being shipped, and that the JIT then ran is an inference from that plus a run selecting `FLASH_ATTN` and generating; `cudaErrorUnsupportedPtxVersion` is the OPPOSITE failure, PTX ISA newer than the driver, which `.version 9.0` under driver 580.173.02 is not. vLLM says it directly too: `FlashAttentionBackend.supports_compute_capability` returns `capability >= DeviceCapability(8, 0)` (`vllm/v1/attention/backends/flash_attn.py:251-252` in the staged wheel). **THE DOWNSTREAM IS THE THING TO CHASE.** #1456's body records that the DFlash2 speed gate's denominator "will be vLLM pinned to `TRITON_ATTN`, by developer decision on 2026-08-20", explicitly because of that conclusion. AGENTS.md requires vLLM's PRODUCTION configuration as the denominator, and on this box vLLM's own auto-selection picks `FLASH_ATTN`: the 0.8017 gate run's log carries BOTH paths in one process, the forced branch taking `TRITON_ATTN` for the 27B target (`cuda.py:426`) and the auto branch taking `FLASH_ATTN` out of four valid backends (`cuda.py:486`), in `/mnt/nas_share/rc/dflash2-1673/out-n1673b/m-gate.log`. **So if `TRITON_ATTN` is the slower backend -- which vLLM's own priority ordering IMPLIES rather than states, and which nothing here measures -- then 16.279 tok/s is too LOW and the ratio is too HIGH. An error in our own favour is the one nobody chases, so it is recorded with its sign.** The ratio is NOT withdrawn and no denominator is substituted, because a wave must not replace a denominator the developer declared. **The five FA layers of [#1685](https://github.com/mudler/vllm.cpp/issues/1685) fall out of the same read**: `vllm/v1/worker/gpu/spec_decode/dflash/utils.py:31-46` sets the draft's `backend=speculative_config.attention_backend` UNCONDITIONALLY, so a harness that sets only the engine backend leaves the draft at `None` and the draft re-runs auto-selection; the siblings `dspark/utils.py:24-28` and `gemma4/speculator.py:66-89` both carry the target's backend through, and dspark's comment names this hazard by name. NOT reconciled in flow, and the reason is precise: what remains is ONE lease running vLLM against itself on this workload with `attention_backend=FLASH_ATTN` against `TRITON_ATTN`, each read back off the built engine, and **no GPU lease is authorised for this session**, so it is PENDING. Recommended collapse, recommended and not taken: #1456, [#1679](https://github.com/mudler/vllm.cpp/issues/1679) and #1685 observe ONE mechanism on two wheels, and #1685 is the one attached to a live number and should survive. Owed under `## Owed` O33 of [the DFlash2 spec](specs/dflash2-spec-decode.md), with caveat 5 beside the ratio in the same file | verification |