diff --git a/experiments/DAMPED_COUPLED_TRIAL_2026-09-18.md b/experiments/DAMPED_COUPLED_TRIAL_2026-09-18.md
index e66d84f..b6cfe1f 100644
--- a/experiments/DAMPED_COUPLED_TRIAL_2026-09-18.md
+++ b/experiments/DAMPED_COUPLED_TRIAL_2026-09-18.md
@@ -59,7 +59,9 @@ every candidate evaluation, fresh selected-state replay and unchanged accepted
 buffers/normalization. Only the accepted trial is replayed for quadrature-14 and
 quadrature-18 physical observations, outside the timed selection phase.
 
-Operation timings exclude artifact output and physical replay; search wall time
+Operation timings include raw preparation, gravity correction and the coupled transaction.
+They exclude setup, ordinary initial/final metric calls, final restoration, accepted
+commit refresh, artifact output and physical replay; search wall time
 also includes artifact output. Callback vector copies remain in the measured
 transaction. The no-correction control captures the same tangent for a comparable
 screen, so capture cost is reported separately and is not ordinary Newton work
diff --git a/experiments/plateau_damped_coupled_diagnostics.hpp b/experiments/plateau_damped_coupled_diagnostics.hpp
index 7126544..8ff80e9 100644
--- a/experiments/plateau_damped_coupled_diagnostics.hpp
+++ b/experiments/plateau_damped_coupled_diagnostics.hpp
@@ -133,7 +133,12 @@ void ProbeDampedCoupledPath(State &state, const mfem::Vector &base, const mfem::
         const auto baseMetric = evaluate(baseF);
         mfem::Vector defect(action);
         defect += baseF;
-        const bool outerGate = d::Norm(defect) <= options.common.outerLinearTolerance * baseMetric.residualNorm;
+        const double defectNorm = d::Norm(defect);
+        const bool outerGate = d::Finite(baseF) && d::Finite(action) && d::Finite(defect) &&
+            std::isfinite(baseMetric.residualNorm) && baseMetric.residualNorm > 0. &&
+            std::isfinite(baseMetric.merit) && baseMetric.merit >= 0. && std::isfinite(d::Norm(direction)) &&
+            std::isfinite(d::Norm(action)) &&
+            std::isfinite(defectNorm) && defectNorm <= options.common.outerLinearTolerance * baseMetric.residualNorm;
         metric("base_norm", baseMetric.residualNorm);
         metric("base_merit", baseMetric.merit);
         metric("outer_relative_defect", d::Norm(defect) / baseMetric.residualNorm);
@@ -196,11 +201,17 @@ void ProbeDampedCoupledPath(State &state, const mfem::Vector &base, const mfem::
                 gravitySeconds = d::Seconds(started);
                 if (gravityGate) d::Save(file("gravity_correction" + suffix), gravity->fullCorrection);
             }
-            const bool usable = preparation.has_value() && gravityGate;
+            // Production rejects an overflowing prepared residual before the
+            // correction transaction, whose precondition requires a valid metric.
+            const bool preparedFinite = preparation.has_value() && gravityGate && d::Finite(state.trialNormalizedResidual);
+            const auto preparedMetric = preparedFinite ? evaluate(state.trialNormalizedResidual) :
+                solver::nonlinear::MetricEvaluation{nan, nan};
+            const bool usable = preparedFinite && std::isfinite(preparedMetric.residualNorm) &&
+                preparedMetric.residualNorm >= 0. && std::isfinite(preparedMetric.merit) && preparedMetric.merit >= 0.;
             const mfem::Vector before(state.trialNormalizedState);
             auto beforeMetric = solver::nonlinear::MetricEvaluation{nan, nan};
             if (usable) {
-                beforeMetric = evaluate(state.trialNormalizedResidual);
+                beforeMetric = preparedMetric;
                 d::Save(file("before" + suffix), before);
                 d::Save(file("before_residual" + suffix), state.trialNormalizedResidual);
             }