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docs(fold): Metal's OCRBench flips point at the build, not drafting #414

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glennneuber merged 1 commit into from
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docs(fold): Metal's OCRBench flips point at the build, not drafting #414

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33 changes: 25 additions & 8 deletions docs/maxusai/tasks/upstream-sync-0.34.4.md
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Expand Up @@ -1026,7 +1026,7 @@ all cells: 189/189 answers byte-identical
- **So the fold's think-off results hold for the deployed build,** with their attribution against the 0.34.0 control.
- **GGUF gemma4:31b ran at `-b/-ub 2048`,** without pieced image decoding (#387).

### OCRBench: all 1000 items, equal to 0.34.0
### OCRBench: all 1000 items, the same score as 0.34.0

gemma4:31b-nvfp4 (manifest `637cc0ff1570`, the checkpoint 0.34.0's 835/1000 record scored), on generate, with think off,
`num_ctx` 16384 and temperature 0. It ran in five chunks of 200, merged by row index (`summarize_extbench.py --paired`,
Expand All @@ -1045,19 +1045,36 @@ ocrbench — `echo840/OCRBench` [test], rows 0..1000.
|---|---|---|---|---|---|
| ocrk0340all vs ocrk0344relall | 829 | 159 | 6 | 6 | 1.000 |

- **The deployed build scores 835 of 1000, as 0.34.0 did.** 6 items flip each way, with McNemar exact p = 1.000.
- **The deployed build scores 835 of 1000, as 0.34.0 did.** 6 items flip each way, with McNemar exact p = 1.000, so the
score does not move.
- **The items are the same:** all 1000 questions and golds equal 0.34.0's, row by row. 975 of the 1000 predictions are
identical.
- **The 12 flips are not attributable to the build.** OCRBench has no grammar, so gemma4 drafts, and every drafted
request is its own sample path.
- **Against the fold, rows 0–199 are identical:** all 200 predictions equal the fold's 200-item run (174 correct,
against 0.34.0's 175).
- **Against the fold, rows 0–199 are identical:** all 200 predictions equal the fold's 200-item run, item 0's flip
included (174/200 correct, against 0.34.0's 175/200).
- **The flips' cause is not isolated.** 0.34.0 ran once. The one repeat of this build's code, the fold's run of rows
0–199, reproduced every prediction, although OCRBench drafts: 999 of the deployed run's 1000 requests drafted. That
points at the build rather than drafting (5881649818). gemma4's MLX model code, its sampler and its drafting code
differ from 0.34.0's only in their package paths, but two other changes can move 31b-nvfp4's numerics on Metal, and
nothing here separates them:
- the MLX pin move, `d9add9d1 → 59d600b5`;
- ADR 0039. At 0.34.0, every dense nvfp4 linear applied its global scale through a float32 round trip that misses
17 of 31b's 191 vision scales by one ulp (#312). ADR 0039 removed it.
- **The `MIXED` banner** is only 0.34.0's missing provenance: its chunks predate H11.
- **The record, item by item:**
[`bench-runs/ocrbench-v1-1000-gemma4-31b-nvfp4-0344-vs-0340.json`](../vision-suite/bench-runs/ocrbench-v1-1000-gemma4-31b-nvfp4-0344-vs-0340.json).

**Not measured on the deployed build: think-on.** Drafting makes think-on uncheckable byte for byte. The undrafted path
above is byte-identical, and the pins and the `server/`, `llm/` and `mlxrunner/` code are the same at the tag.
**Not measured on the deployed build: think-on.** A byte comparison may not hold for it. Two-pass drafts the thinking,
and on this host drafted thinking parted from itself at character 594 across a window change, and at character 58 after
a different preceding request, where the undrafted single pass stayed byte-identical (5824799988). Short drafted answers
can repeat exactly, as OCRBench's rows 0–199 did. The undrafted path above is byte-identical, and the pins and the
`server/`, `llm/` and `mlxrunner/` code are the same at the tag.

Runs: `rel-0344.log`, `proto-rel-thinkoff.log` and `proto-rel-ocrbench.log` in the fold worktree's `.campaign/`, with
the driver `rel-0344.sh`, the comparer `drv/eq_check.py`, and `drv/merge_ext.py` and `drv/build_ocr_record.py`, which
merged the chunks and wrote the record, in the same directory. The server log there, `serve-11436.log`, carries the
OCRBench run's `speculative decode stats`, one line per request. The answers compared are `resp_r0344rel_1_*` against
`resp_f0344p2_1_*`. The OCRBench runs are `ext_ocrk0344relall_ocrbench.json` and `ext_ocrk0340all_ocrbench.json`, and
the fold's 200-item run is `ext_ocr0344p2_ocrbench.json`, all in the fold worktree's suite directory.

## Gates 4–6 on gfx1151 (2026-09-25)

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