Result
Two findings survive rigorous noise control; per-page claims do not (see
methodology note).
-
Eval loss (teacher-forced, sampling-free): best in the series at every
step — 0.5444 at 1200, 0.5310 at 1800, roughly 0.028 below both the
merger-LoRA twin and the frozen-merger flagship at their step-1300 finals.
The only loss-curve separation in the series, and it kept widening
(decelerating) through 1800.
-
Transcription benchmark medians: statistically tied. Religious
manuscripts 0.811 (flagship 0.816, merger-LoRA 0.810); frozen PGP-131
0.870 (0.862 / 0.868). The likelihood gain never translated into
transcription-benchmark gains — at 1200 or at 1800.
-
Zero-shot grounding (none of these arms saw grounding data): merger
training visibly reorganizes spatial association. On a frozen 133-query
grounding eval (phrase→box, box→text, grounded page transcription):
Table with columns: arm, locate median IoU, read_box CER, grounded line-box IoU| arm | locate median IoU | read_box CER | grounded line-box IoU |
|---|
| v1.9a-1300 (frozen merger) | 0.288 | 0.579 | 0.150 |
| v1.9b-1300 (merger LoRA) | 0.278 | 0.543 | 0.437 |
| v1.9c-1200 (full) | 0.277 | 0.820 | 0.253 |
| v1.9c-1800 (full, +600 steps) | 0.318 | 0.771 | 0.355 |
Both trained-merger arms emit far better-localized line boxes than the
frozen arm (line IoU 0.437 / 0.355 vs 0.150) while transcription medians
stay tied — and the effect is undirected: full-weight training initially
degrades region-conditioned reading (read_box 0.820 vs 0.579), then
partially recovers while every spatial metric improves monotonically
through step 1800. The merger is still actively reorganizing spatial
pathways late in training, from transcription-only supervision.
Methodology note. Per-page "break/rescue" comparisons between these
arms are unreliable at single-decode granularity: a same-model rerun
control (identical weights, temperature 0.1) flipped 4 of 29 probed
fragments across the 0.5 aligned-F1 line, including the largest swings
previously attributed to merger effects. A tail of fragments is bistable
under sampled decoding; page-level attribution requires N-decode averaging
or greedy evaluation. Medians, loss curves, and the aggregate grounding
rates above are robust to this and are the basis of every conclusion here.
Conclusion: full-weight merger training improves likelihood but not
transcription benchmarks, so v2.0a keeps the merger frozen (simpler,
equal). But the grounding probe shows the merger is precisely where
prompt↔visual-region association lives — motivating a v2.0b arm that
re-enables merger training on v2.0's grounding-supervised mixture, judged
on grounding metrics with transcription medians as the no-regression
guard. Single-seed caveat applies throughout.
The series at a glance
One line per generation — which checkpoint to use and which are historical:
Table with columns: version, repo, status, canonical revision, headline (benchmark)| version | repo | status | canonical revision | headline (benchmark) |
|---|
| v2.0a | v20a-ckpt | current best on both corpora; first with grounding | step 1800 af9df6a0 | F1 0.849 (religious-140) / 0.875 (PGP-131); locate IoU 0.467, read_box CER 0.129 |
| v1.9a | v19a-ckpt | FLAGSHIP — use this | step 1300 |
* CER over substantive attempts only, alignment-based scorer. Benchmarks
differ across generations (Talmud print vs Genizah manuscripts) — compare
within a row's named benchmark, not across rows.