diff --git a/frontend/style.css b/frontend/style.css
index dc3f3e6..7f905a8 100644
--- a/frontend/style.css
+++ b/frontend/style.css
@@ -28,14 +28,14 @@ html, body {
   -webkit-tap-highlight-color: transparent;
   overscroll-behavior: none;
   user-select: none;
+  overflow: hidden;
 }
 
 body {
   display: flex;
   flex-direction: column;
-  min-height: 100vh;
-  /* Use dynamic viewport height on mobile to account for browser chrome */
-  min-height: 100dvh;
+  height: 100vh;
+  height: 100dvh;
 }
 
 /* ===== Private mode banner (decision #1041) ===== */
@@ -148,10 +148,8 @@ body {
 /* ===== SOS button (min 60vmin × 60vmin per UX spec) ===== */
 
 .btn-sos {
-  width: 60vmin;
-  height: 60vmin;
-  min-width: 180px;
-  min-height: 180px;
+  width: min(60vmin, 70vw, 300px);
+  height: min(60vmin, 70vw, 300px);
   border-radius: 50%;
   border: none;
   background: var(--sos);
diff --git a/frontend/sw.js b/frontend/sw.js
index 807e2c4..a81706c 100644
--- a/frontend/sw.js
+++ b/frontend/sw.js
@@ -1,6 +1,6 @@
 'use strict';
 
-const CACHE_NAME = 'baton-v2';
+const CACHE_NAME = 'baton-v3';
 
 // App shell assets to precache
 const APP_SHELL = [