Cut 5's own probe passed while breaking Cut 3's reuse rule: with R7 holding
the rim, the through-thickness echo (KEcho/_EchoReflect) is the only
remaining source of sub-critical tension for a weak hit, and its magnitude
(-0.65) was weaker than the still-live residual compression velocity left
by the direct KInject kick by the time the echo fired. The echo's own
header comment says a free-surface reflection inverts with unit
magnitude, matching the pre-R7 rim's Dirichlet condition -- -0.65 was a
lossy fraction that could reduce but never flip the sign of u, so a weak
hit's u never crossed positive and KFracture's `u <= 0` guard skipped the
sub-critical erosion branch forever, no matter how many hits landed.
Raised echoReflect from -0.65 to -0.9 (ShieldPanel.cs) -- enough margin to
flip a weak hit's residual compression into net tension without needing a
delay/seeding change; echoDelaySteps and KInject's seeding were not the
defect. All four probes now pass, including Cut 3's reuse rule (temper
0.4180 -> 0.3997 on a reused panel).
Also lands the multi-hit-reuse rule Cut 5's own report flagged as unpinned:
CheckRepeatedWeakHitsBreakWhereOneDoesNot in ShieldPanelCut5Verify.cs.
Energy 15 (not 8, whose peak tension of ~0.14 sits under tensileStrength
0.2 and can never break at any repetition) breaks on hit 2 of a live,
reused panel while a cold single hit -- given equal idle time (720 steps,
matching the multi-hit run's total budget, to rule out "just needed more
time to ring out") -- never breaks. This is the Cut 3 reuse rule and the
temper mechanism producing the operator-facing payoff together.
Verified: ShieldPanelCut1Verify, Cut2Verify, Cut3Verify, Cut5Verify all
PASS via batchmode (graphics device required, not -nographics).
Operator watch: echoReflect at -0.9 is close to the physical "unit
inversion" ceiling implied by the header comment; if later tuning raises
hit energies or lowers damping, watch for the echo overshooting into an
immediate break on a single moderate hit (observed at -1.4 and even -1.0
in earlier tuning passes) rather than the intended multi-hit erosion.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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