An adversarial review found a real regression: removing the greedy overflow
re-check left walk_region's has_note skip with no safety net. When a note-less
leading measure precedes a soft (or automatic) break at a barline, walk_region
skips the break — the closing system has no content — but the DP, which treated
that barline as a forced segment boundary, optimized each side independently and
could not foresee the skip. The following optimizer-filled measures then absorb
the furniture measure and silently overflow into a MULTI-measure overfull system
(forbidden by the module's own contract). The review verified the rest of the DP
sound (reachability can't yield a giant overfull system, determinism holds).
Fix: restore the greedy overflow check as a fallback net — walk_region also
breaks before a measure that would overflow the content width
(chunk_hi[i] - current_lo > width_limit, guarded by has_note). In the common
content-full case the DP's break fires first, so the net never triggers and the
geometry is the optimizer's (zero golden churn).
Regression: a_content_less_measure_before_a_soft_break_never_overflows (a wide
note-less M0 + a soft break + narrow-then-wide measures; verified to fail
without the net: "system 0 spans 5 measures at width 60 > 42"). 945 tests,
clippy 0, docs -D warnings, zero golden churn, conformance 8/8.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Levi Neuwirth
177bcdb43b