When part spacing exceeds a clamp's inflated span the per-axis block
interval [zone - clearance + s, zone + clearance] inverts. The old
collapse to the zone centerline was not conservative: a part could
start exactly on the centerline with material inside the clamp
(PM d86d22c9 - the probe rail Box(0,0,5,0.625) at part spacing 4
completed at y=0.3125). Per decision D11, an inverted span now blocks
a zero-extent line at the clamp edge facing the sheet interior:
zone max + clearance when the zone center is in the bin's lower half
on that axis, else zone min - clearance + s, so interior-side parts
keep the exact bottom-edge clearance and the unavoidable extra
exclusion lands toward the nearer sheet edge.
Failing-first: the PM probe fixture in quadrants 1-4 and two X-inverted
fixtures (mid-rail and far-rail) were red on ab50900 against an
independent material-vs-inflated-footprint oracle; all six now pass.
Non-inverted spans stay bit-for-bit identical: four keep-row layout
digests captured from the unfixed ab50900 packer are unchanged, the
between-clamp rows still pack the gap, and the three zero-clamp C2
baseline hashes are untouched. Full Engine suite 929 passed/2 existing
skips.
Block each clamp's keep-out into the max-rects free list before any
packing: same split logic as placements, not a used item (no contact
score, no material). The blocked rectangle accounts for the inflated
item model exactly - material keeps the bottom-edge clearance from the
clamp without paying an extra part-spacing tax; degenerate spans
collapse to the zone centerline (conservative, never permissive).
Zero-clamp sheets skip blocking entirely: three fixture layout hashes
(rectangle grid, mixed shapes, multi-sheet overflow), captured from the
unchanged packer at a3f1124, stay bit-identical (C2). With clamps:
placements never intrude, demand lands between two clamps when it fits,
a full-width front rail makes an otherwise feasible job Incomplete, and
a far-away zone leaves the layout hash equal to no-clamps.
Rectangles lane only; Irregular parity is Slice 2.
aj