diff --git a/experiments/nonlinear_step_controls_2026-09-18.json b/experiments/nonlinear_step_controls_2026-09-18.json
new file mode 100644
index 0000000..4fc0eea
--- /dev/null
+++ b/experiments/nonlinear_step_controls_2026-09-18.json
@@ -0,0 +1,43 @@
+[
+  {
+    "id": "n1p5_late_eta0003",
+    "arguments": [
+      "--index", "1.5",
+      "--angular-momentum", "0",
+      "--no-central",
+      "--max-newton", "0",
+      "--strategy", "curvature",
+      "--nonlinear-step-probe",
+      "--probe-state", "/Users/tboudreaux/.codex/.chatgpt-projects/g-p-6a6b3f2194ec8191bebcd59075897f1d/diagnostics/preconditioner_improvement_2026-09-18/newton_v1/n1p5_J0_curvature_gravity_schur/accepted_state.txt",
+      "--restart", "160",
+      "--max-linear", "600",
+      "--linear-tol", "0.003",
+      "--preconditioner-variant", "gravity-schur",
+      "--schur-sweeps", "1",
+      "--schur-relaxation", "0.5",
+      "--gravity-tol", "1e-10",
+      "--gravity-iterations", "300",
+      "--gravity-restart", "80"
+    ]
+  },
+  {
+    "id": "n1p5_seed_eta003",
+    "arguments": [
+      "--index", "1.5",
+      "--angular-momentum", "0",
+      "--no-central",
+      "--max-newton", "0",
+      "--strategy", "curvature",
+      "--nonlinear-step-probe",
+      "--restart", "160",
+      "--max-linear", "600",
+      "--linear-tol", "0.03",
+      "--preconditioner-variant", "gravity-schur",
+      "--schur-sweeps", "1",
+      "--schur-relaxation", "0.5",
+      "--gravity-tol", "1e-10",
+      "--gravity-iterations", "300",
+      "--gravity-restart", "80"
+    ]
+  }
+]
diff --git a/experiments/nonlinear_step_late_case_2026-09-18.json b/experiments/nonlinear_step_late_case_2026-09-18.json
new file mode 100644
index 0000000..a52cb11
--- /dev/null
+++ b/experiments/nonlinear_step_late_case_2026-09-18.json
@@ -0,0 +1,23 @@
+[
+  {
+    "id": "n1p5_late_eta003",
+    "arguments": [
+      "--index", "1.5",
+      "--angular-momentum", "0",
+      "--no-central",
+      "--max-newton", "0",
+      "--strategy", "curvature",
+      "--nonlinear-step-probe",
+      "--probe-state", "/Users/tboudreaux/.codex/.chatgpt-projects/g-p-6a6b3f2194ec8191bebcd59075897f1d/diagnostics/preconditioner_improvement_2026-09-18/newton_v1/n1p5_J0_curvature_gravity_schur/accepted_state.txt",
+      "--restart", "160",
+      "--max-linear", "600",
+      "--linear-tol", "0.03",
+      "--preconditioner-variant", "gravity-schur",
+      "--schur-sweeps", "1",
+      "--schur-relaxation", "0.5",
+      "--gravity-tol", "1e-10",
+      "--gravity-iterations", "300",
+      "--gravity-restart", "80"
+    ]
+  }
+]