diff --git a/docs/product/midi-playback.md b/docs/product/midi-playback.md
index bf41338..97e58c6 100644
--- a/docs/product/midi-playback.md
+++ b/docs/product/midi-playback.md
@@ -1281,9 +1281,11 @@ small labelled knobs in functional clusters** — and drives the **Wave B editor
    same knob deck + button/popup — Sample and Zone already edit one storage site (S15-F2); the lean
    is that they should speak one control grammar too. Daniel's call (it grows Wave B scope).
 
-**What does NOT change (guardrails).** Zero engine/state/persistence change — this is a view
-recomposition of *existing* controls; no new params, no component-state bump, VST3 class UID
-unchanged. All drawing through the L1 kit by palette role; all layout/hit-test in new pure modules
+**What does NOT change (guardrails).** Zero engine-behavior change — this is a view
+recomposition of *existing* controls, with one additive exception: the new post-mixer master
+gain persists as `masterGainLinear`, bumping `ComponentState` v7→v8 (back-compat: pre-v8 blobs
+lift to unity gain); VST3 class UID unchanged. All drawing through the L1 kit by palette role;
+all layout/hit-test in new pure modules
 (`knob_deck`, `curve_popup` — mirrors of `action_bar`/`overflow_menu`); the knobs and the hero's
 envelope nodes remain two surfaces on one param model (S-VIEW-F2's structural sync, untouched).
 The full inventory of what landed (every element → its r11 home) is recorded in