diff --git a/handoff/NOTES_LEVEL.md b/handoff/NOTES_LEVEL.md
index 3b59474..095ede6 100644
--- a/handoff/NOTES_LEVEL.md
+++ b/handoff/NOTES_LEVEL.md
@@ -1036,3 +1036,27 @@ reproduce the committed references EXACTLY. => Bit-exact (bytes) is REACHABLE; t
 that could have made it impossible (per-run randomization) is closed. The remaining work
 to bytes-parity is purely: exact structural chain + exact kernels + internal 48000/4096
 geometry + live A/B/gamma, NOT fighting host nondeterminism.
+
+## ============ UPDATE 2026-08-20v: EXISTING PARAMETRIC LUT SETS BENCHED (F1 closure) ============
+All previously-derived parametric-LUT sets (from repo scripts + NOTES) tested on the
+FULL honest 24-bit corpus (59 cases) inside ONE fixed bridge pipeline
+(C = G*LUT(xv)+W*warp^A, gain=(1-C)*res^rp, committed G/W/A/rp). Result:
+
+  LUT form            mean|err|  max
+  ------------------  --------  -----
+  pchip   (committed)   0.773   3.426   <-- BEST (unchanged)
+  linear  (0.483/0.717) 1.017   3.116
+  realpts (lutpts.npy)  1.134   3.192
+  u563a60 (A=-13.78/B=68.29/g=0.344) 1.669 6.004
+  lut5    (0.4356/0.5914/1.999/0.9364) 1.785 3.951
+  lut4    (fit_lut)     1.785   3.951
+  powerlaw(C=8)         6.809  11.880
+
+=> The empirical Pchip curve remains the best form-factor; NO existing parametric set
+   beats it at fixed bridge params. Realistic conclusion: the recovered runtime curve
+   (NOTES:967) was fit to extracted (xv,C) points, but those points themselves came from
+   the SAME bridge-shaped model (LUT=xv->C), so parameteric fits overfit their source
+   and lose on the honest render metric. Pchip baseline (0.773) stays canonical.
+   F1 (params of the LUT curve) is hereby CLOSED as "already produced, none accepted";
+   the structural A/B/gamma from ctx+0x188 remains the only path to bytes (blocked:
+   level-path object not live-captured; see F2/F5.)