From f35a6307227023780c88eb81103721c0c02335b5 Mon Sep 17 00:00:00 2001
From: Matiq <kokagishi@proton.me>
Date: Tue, 18 Aug 2026 18:50:31 +0300
Subject: [PATCH] Handoff: step5 dB-parity result (0.268 dB) + measurement
 notes

---
 handoff/SESSION_HANDOFF.md | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/handoff/SESSION_HANDOFF.md b/handoff/SESSION_HANDOFF.md
index 9dd8785..4182749 100644
--- a/handoff/SESSION_HANDOFF.md
+++ b/handoff/SESSION_HANDOFF.md
@@ -107,6 +107,22 @@ NEXT SESSION START (recommendation): skip deeper FFT mining; go straight to step
 smoothing + 0x540658 shaping that can be fit/absorbed). Runtime capture of 0x540658 only if step 5
 stalls on the Q=0.1 knee.
 
+### STEP 5 STARTED (2026-08-18) — dB-parity harness DONE (commit f96bb42)
+- `/home/m/re-tools/render_parity.py`: measures steady-state per-tone reduction DIRECTLY on the
+  reference wavs (Goertzel tone-amp over late steady window; handles 16/24-bit, mono/stereo).
+  NOTE: Goertzel must use the SEQUENTIAL update form (s2=s1;s1=s0;s0=v+cw*s1-s2) — the tuple-unpack
+  form is numerically unstable (overflows ~1500 steps).
+- Validation: measured dual Q-scan == stored dataset (dual.wav is 4s mono 16-bit; renders 6s stereo 24-bit).
+- **dB-PARITY RESULT (canonical B.12, 36 pts, real wavs): TOTAL rmse=0.268 dB**
+  (dual500 0.130, dual2000 0.387, t1kq 0.320, t1k 0.076).
+  residual structure: dual2000 -0.80@Q0.1..+0.36@Q10 (LUT-knee), t1kq +0.36..+0.26 (level region),
+  t1k ±0.1 (good). Refit (g,w,a)=(1.224,0.379,3.405)→0.264; +2 LUT-knots→0.203 (plateau).
+- CONCLUSION: B.12 form plateau ~0.20-0.27 dB vs real renders; residual is structural (0x540658
+  FFT shaping + level-curve region), matches plan expectation. Re-measured-on-wav numbers differ
+  slightly from the stored model_lut.py dataset (t1kq ~+0.3 dB) — different steady-window method.
+- Open: full PIPELINE frame-render (STFT + per-frame mask + time constants) is the remaining big
+  lift for byte-parity; dB-parity milestone achieved at 0.268 dB.
+
 Candidates that may consume Phase 5 time: source of sens≈24.65 (host ×2 over XML 12.0 — not found in dump),
 IAT\*0x181bab370 outside dump (non-blocking), final z¹ phase proof, the 0x563440 LUT curve (+0x188) values.