§38.2 concluded the objective is net-positive on severing a level's
circulation: merging a corridor into a habitable sibling gains x6
(value_inside/value_circulation), while "level N not connected" costs x0.5, so
break-even needs 0.5^w < 50/300, w > 2.58 -- "severing must cost at least 3
fails and costs 1". The arithmetic is right. The premise is wrong.
Shipped anyway, EXPERIMENTAL and default off (byte-identical):
fitness.connectivity_weight_for(value_inside, value_circulation) returns the
smallest weight making severing net-negative -- 3.0 at the defaults, DERIVED
from the rates rather than hard-coded so it tracks them if either is retuned.
conf["connectivity_weight"] takes 1.0 / "auto" / a number and counts each
connectivity failure as w failures in the 0.5^n penalty.
MEASUREMENT: at auto (=3) the §38.2 deletion test does not move at all -- 5/25
rewarded either way, median x0.26 vs x0.27. Reason: the connectivity fail count
is UNCHANGED in every rewarded deletion (115->107 fails but 5->5 connectivity;
107->99 but 3->3; 78->71 but 3->3). Weighting a fail that never fires changes
nothing.
And when a deletion DOES break connectivity, it is already punished. Every such
case, 4 seeds per programme: harbor-house 2 of 32 sampled deletions, both
punished (x0.00, x0.01); maple-court 5 of 32, all punished (x0.58 .. x0.07).
Severing costs 1-2 connectivity fails PLUS the cascade after them, which
already outweighs the x6 gain. The flat rule was never the problem.
Where §38.2 went wrong: the x4.06 "well-daylit circulation leaf" that motivated
the bead was a deletion that did NOT change the connectivity fail count. It was
rewarded for removing the leaf's own quality failures -- §38.1's zero-value
finding -- and I misread it as a pricing mechanism. §38.2 now carries the
retraction inline. Two lessons recorded: a plausible closed-form arithmetic is
not a measurement, and when a fix produces exactly no effect, suspect the
premise before the implementation.
Still standing from §38: §38.1 (buried leaves score zero quality and contribute
no value) and §38.3 (frontage budget) are direct measurements. §39.7 remains
the better lever on the same symptom -- it made the connectivity fails FIRE,
where this would only have made them cost more.
Re-opened as homemaker-py-yql: why level-not-connected persists in the best
layout when severing is already punished. Evidence now points at reachability,
not incentive, and it is newly measurable because §39.7 stopped store cupboards
standing in for corridors.
353 passed (+3 new), same 7 pre-existing fixture failures, lint unchanged.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MJ84Feep79Hhm3E4zZJmnB
3aee813ccd