diff --git a/desktop/src/features/settings/ui/SettingsPanels.tsx b/desktop/src/features/settings/ui/SettingsPanels.tsx
index ab423c833..14632697a 100644
--- a/desktop/src/features/settings/ui/SettingsPanels.tsx
+++ b/desktop/src/features/settings/ui/SettingsPanels.tsx
@@ -1,4 +1,4 @@
-import { useEffect, useMemo, useState } from "react";
+import { useMemo, useState } from "react";
 import { AnimatePresence, motion, useReducedMotion } from "motion/react";
 import {
   Archive,
@@ -438,14 +438,8 @@ function ThemeSettingsCard() {
       ? "light"
       : "dark";
 
-  const [selectedMode, setSelectedMode] = useState<AppearanceMode>(activeMode);
   const [themeStyleExpanded, setThemeStyleExpanded] = useState(false);
 
-  // Community sync can replace the appearance while this panel remains open.
-  // Mirror that external value so the segmented control never describes the
-  // previous community's color mode.
-  useEffect(() => setSelectedMode(activeMode), [activeMode]);
-
   const getVars = (name: SyntaxThemeName) =>
     withAccentPreviewVars(
       previewVarsByTheme[name] ?? getThemeFallbackPreviewVars(name),
@@ -467,7 +461,6 @@ function ThemeSettingsCard() {
   }, [pairedLight, darkOnly]);
 
   const handleModeSelect = (mode: AppearanceMode) => {
-    setSelectedMode(mode);
     if (mode === "system") {
       setFollowSystem(true);
       // If the current theme is unpaired, resolveSystemTheme can't switch it
@@ -505,7 +498,7 @@ function ThemeSettingsCard() {
 
   const handleSelectTheme = (name: SyntaxThemeName) => {
     setTheme(name);
-    if (selectedMode === "system") {
+    if (activeMode === "system") {
       setFollowSystem(true);
     } else {
       setFollowSystem(false);
@@ -518,7 +511,7 @@ function ThemeSettingsCard() {
     return selectedThemeName === lightName || selectedThemeName === darkName;
   };
   const selectedPairedTheme =
-    selectedMode === "system" ? pairedLight.find(isPairActive) : undefined;
+    activeMode === "system" ? pairedLight.find(isPairActive) : undefined;
   const selectedTheme = selectedThemeName as SyntaxThemeName;
   const selectedPairedDarkTheme = selectedPairedTheme
     ? getThemePair(selectedPairedTheme)
@@ -579,7 +572,7 @@ function ThemeSettingsCard() {
         ) : null}
         <div className="max-h-[430px] overflow-y-auto rounded-lg pt-2">
           <div className="flex flex-wrap gap-4 p-1">
-            {selectedMode === "system" &&
+            {activeMode === "system" &&
               pairedLight.map((lightName) => {
                 const darkName = getThemePair(lightName);
                 if (!darkName) return null;
@@ -594,7 +587,7 @@ function ThemeSettingsCard() {
                   />
                 );
               })}
-            {selectedMode === "light" &&
+            {activeMode === "light" &&
               allLightThemes.map((name) => (
                 <SingleThemeTile
                   isActive={selectedThemeName === name}
@@ -604,7 +597,7 @@ function ThemeSettingsCard() {
                   vars={getVars(name)}
                 />
               ))}
-            {selectedMode === "dark" &&
+            {activeMode === "dark" &&
               allDarkThemes.map((name) => (
                 <SingleThemeTile
                   isActive={selectedThemeName === name}
@@ -656,16 +649,16 @@ function ThemeSettingsCard() {
                 className="absolute bottom-0.5 left-0.5 top-0.5 z-0 rounded-md bg-background shadow-sm transition-transform duration-[250ms] ease-out motion-reduce:transition-none"
                 data-testid="appearance-color-mode-indicator"
                 style={{
-                  transform: `translateX(${APPEARANCE_MODE_OPTIONS.findIndex((option) => option.mode === selectedMode) * 100}%)`,
+                  transform: `translateX(${APPEARANCE_MODE_OPTIONS.findIndex((option) => option.mode === activeMode) * 100}%)`,
                   width: "calc((100% - 4px) / 3)",
                 }}
               />
               {APPEARANCE_MODE_OPTIONS.map(({ mode, label, Icon }) => (
                 <button
-                  aria-pressed={selectedMode === mode}
+                  aria-pressed={activeMode === mode}
                   className={cn(
                     "relative z-10 flex h-full items-center justify-center gap-1.5 rounded-md bg-transparent px-2.5 text-xs font-medium transition-colors duration-[250ms] ease-out focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-ring motion-reduce:transition-none",
-                    selectedMode === mode
+                    activeMode === mode
                       ? "text-foreground"
                       : "text-muted-foreground hover:text-foreground",
                   )}
diff --git a/desktop/src/shared/theme/CommunityThemeController.tsx b/desktop/src/shared/theme/CommunityThemeController.tsx
index dca362e2b..90f93a0d0 100644
--- a/desktop/src/shared/theme/CommunityThemeController.tsx
+++ b/desktop/src/shared/theme/CommunityThemeController.tsx
@@ -3,13 +3,15 @@ import { useCommunities } from "@/features/communities/useCommunities";
 import { relayClient } from "@/shared/api/relayClient";
 import { useIdentityQuery } from "@/shared/api/hooks";
 import {
-  DEFAULT_COMMUNITY_THEME,
   cacheAndApplyCommunityTheme,
   clearCommunityThemeOutbox,
+  communityThemeAppearanceFallback,
   communityThemeApplyExpectation,
   communityThemePersistenceAction,
   communityThemeScopeFallback,
   hasMigratedCommunityTheme,
+  hasMigratedCommunityThemeAppearance,
+  markCommunityThemeAppearanceMigrated,
   markCommunityThemeMigrated,
   readCommunityThemeOutbox,
   readCommunityThemePreference,
@@ -80,21 +82,28 @@ export function CommunityThemeController() {
 
   useLayoutEffect(() => {
     if (!pubkey || !relayUrl) return;
-    const legacyFallback = communityThemeScopeFallback(
+    const scopeFallback = communityThemeScopeFallback(
       hasMigratedCommunityTheme(pubkey),
       initialPreferenceRef.current,
     );
+    const appearanceFallback = communityThemeAppearanceFallback(
+      hasMigratedCommunityThemeAppearance(pubkey),
+      initialPreferenceRef.current,
+    );
     const local = readCommunityThemePreference(
       pubkey,
       relayUrl,
-      legacyFallback,
+      appearanceFallback,
     );
-    const dirty = readCommunityThemeOutbox(pubkey, relayUrl, legacyFallback);
-    // Preserve the user's existing global appearance the first time this
-    // feature sees their current community. Later missing/malformed target
-    // records use the stable default so the previous community never leaks.
-    const fallback = legacyFallback;
-    const scopedPreference = dirty ?? local ?? fallback;
+    const dirty = readCommunityThemeOutbox(
+      pubkey,
+      relayUrl,
+      appearanceFallback,
+    );
+    // Scope migration decides whether an entirely empty community inherits the
+    // outer appearance. Appearance migration separately fills fields missing
+    // from an existing three-field record.
+    const scopedPreference = dirty ?? local ?? scopeFallback;
     scopedPreferenceRef.current = scopedPreference;
     applyPreference(scopedPreference);
     // Initialization is programmatic even when the provider already exposes
@@ -110,7 +119,25 @@ export function CommunityThemeController() {
   useEffect(() => {
     if (!pubkey || !relayUrl) return;
     const scope = `${pubkey}:${relayUrl}`;
-    const legacyFallback = communityThemeScopeFallback(
+    const appearanceFallback = communityThemeAppearanceFallback(
+      hasMigratedCommunityThemeAppearance(pubkey),
+      initialPreferenceRef.current,
+    );
+    const local = readCommunityThemePreference(
+      pubkey,
+      relayUrl,
+      appearanceFallback,
+    );
+    const durablePending = readCommunityThemeOutbox(
+      pubkey,
+      relayUrl,
+      appearanceFallback,
+    );
+    // A value already cached for this relay is the safest fallback for a later
+    // incomplete event. Without one, use the one-time appearance migration
+    // seed, which is never taken from a previous community after migration.
+    const legacyFallback = durablePending ?? local ?? appearanceFallback;
+    const scopeFallback = communityThemeScopeFallback(
       hasMigratedCommunityTheme(pubkey),
       initialPreferenceRef.current,
     );
@@ -136,11 +163,6 @@ export function CommunityThemeController() {
       legacyFallback,
     );
     managerRef.current = manager;
-    const durablePending = readCommunityThemeOutbox(
-      pubkey,
-      relayUrl,
-      legacyFallback,
-    );
     if (durablePending) manager.publish(durablePending);
 
     const applyRemote = (remote: RemoteCommunityTheme) => {
@@ -188,16 +210,18 @@ export function CommunityThemeController() {
         if (remote) {
           applyRemote(remote);
           markCommunityThemeMigrated(pubkey);
+          markCommunityThemeAppearanceMigrated(pubkey);
         } else if (shouldSeedCommunityTheme(result)) {
-          const local =
+          const seed =
             readCommunityThemeOutbox(pubkey, relayUrl, legacyFallback) ??
             readCommunityThemePreference(pubkey, relayUrl, legacyFallback) ??
             scopedPreferenceRef.current ??
-            DEFAULT_COMMUNITY_THEME;
-          writeCommunityThemePreference(pubkey, relayUrl, local);
-          writeCommunityThemeOutbox(pubkey, relayUrl, local);
+            scopeFallback;
+          writeCommunityThemePreference(pubkey, relayUrl, seed);
+          writeCommunityThemeOutbox(pubkey, relayUrl, seed);
           markCommunityThemeMigrated(pubkey);
-          manager.publish(local);
+          markCommunityThemeAppearanceMigrated(pubkey);
+          manager.publish(seed);
         }
         // Invalid or unavailable hydration keeps the already-applied fallback
         // without publishing over relay state we could not establish safely.
@@ -250,8 +274,8 @@ export function CommunityThemeController() {
     const stored = readCommunityThemePreference(
       pubkey,
       relayUrl,
-      communityThemeScopeFallback(
-        hasMigratedCommunityTheme(pubkey),
+      communityThemeAppearanceFallback(
+        hasMigratedCommunityThemeAppearance(pubkey),
         initialPreferenceRef.current,
       ),
     );
diff --git a/desktop/src/shared/theme/communityThemePreference.test.mjs b/desktop/src/shared/theme/communityThemePreference.test.mjs
index 70a5803a4..f3804a619 100644
--- a/desktop/src/shared/theme/communityThemePreference.test.mjs
+++ b/desktop/src/shared/theme/communityThemePreference.test.mjs
@@ -1,14 +1,20 @@
 import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
 import test from "node:test";
 import {
   DEFAULT_COMMUNITY_THEME,
   cacheAndApplyCommunityTheme,
   clearCommunityThemeOutbox,
+  communityThemeAppearanceFallback,
   communityThemeApplyExpectation,
   communityThemeOutboxKey,
   communityThemePersistenceAction,
   communityThemeScopeFallback,
   communityThemeStorageKey,
+  hasMigratedCommunityTheme,
+  hasMigratedCommunityThemeAppearance,
+  markCommunityThemeAppearanceMigrated,
+  markCommunityThemeMigrated,
   parseCommunityThemePreference,
   readCommunityThemeOutbox,
   readCommunityThemePreference,
@@ -16,6 +22,7 @@ import {
   writeCommunityThemeOutbox,
   writeCommunityThemePreference,
 } from "./communityThemePreference.ts";
+import { GLASS_OPACITY_MAX, GLASS_OPACITY_MIN } from "./ThemeProvider.tsx";
 
 function localStorageStub() {
   const data = new Map();
@@ -98,7 +105,7 @@ test("older theme records inherit the pre-migration appearance controls", () =>
   });
 });
 
-test("later legacy records use stable defaults instead of a prior community", () => {
+test("completed appearance migration uses stable defaults", () => {
   const priorCommunity = {
     ...DEFAULT_COMMUNITY_THEME,
     glassBackground: true,
@@ -115,12 +122,86 @@ test("later legacy records use stable defaults instead of a prior community", ()
   assert.deepEqual(
     parseCommunityThemePreference(
       olderRecord,
-      communityThemeScopeFallback(true, priorCommunity),
+      communityThemeAppearanceFallback(true, priorCommunity),
     ),
     { ...DEFAULT_COMMUNITY_THEME, ...olderRecord },
   );
 });
 
+test("appearance widening is independent from community scoping", () => {
+  globalThis.window = { localStorage: localStorageStub() };
+  const inherited = {
+    ...DEFAULT_COMMUNITY_THEME,
+    glassBackground: true,
+    glassOpacity: 80,
+    prominentActiveTab: true,
+  };
+  const legacy = {
+    version: 1,
+    theme: "houston",
+    accent: "#a855f7",
+    followSystem: false,
+  };
+  window.localStorage.setItem(
+    communityThemeStorageKey("alice", "wss://relay.example"),
+    JSON.stringify(legacy),
+  );
+
+  markCommunityThemeMigrated("alice");
+  assert.equal(hasMigratedCommunityTheme("alice"), true);
+  assert.equal(hasMigratedCommunityThemeAppearance("alice"), false);
+  assert.deepEqual(
+    readCommunityThemePreference(
+      "alice",
+      "wss://relay.example",
+      communityThemeAppearanceFallback(
+        hasMigratedCommunityThemeAppearance("alice"),
+        inherited,
+      ),
+    ),
+    {
+      ...legacy,
+      glassBackground: true,
+      glassOpacity: 80,
+      prominentActiveTab: true,
+    },
+  );
+
+  markCommunityThemeAppearanceMigrated("alice");
+  assert.equal(hasMigratedCommunityThemeAppearance("alice"), true);
+  assert.deepEqual(
+    communityThemeAppearanceFallback(
+      hasMigratedCommunityThemeAppearance("alice"),
+      inherited,
+    ),
+    DEFAULT_COMMUNITY_THEME,
+  );
+});
+
+test("desktop appearance limits match the shared wire contract", () => {
+  const contract = JSON.parse(
+    readFileSync(
+      new URL("../../../../schema/community-theme-v1.json", import.meta.url),
+      "utf8",
+    ),
+  );
+
+  assert.equal(
+    DEFAULT_COMMUNITY_THEME.glassBackground,
+    contract.properties.glassBackground.default,
+  );
+  assert.equal(
+    DEFAULT_COMMUNITY_THEME.glassOpacity,
+    contract.properties.glassOpacity.default,
+  );
+  assert.equal(GLASS_OPACITY_MIN, contract.properties.glassOpacity.minimum);
+  assert.equal(GLASS_OPACITY_MAX, contract.properties.glassOpacity.maximum);
+  assert.equal(
+    DEFAULT_COMMUNITY_THEME.prominentActiveTab,
+    contract.properties.prominentActiveTab.default,
+  );
+});
+
 test("appearance equality includes glass and prominent-tab choices", () => {
   assert.equal(
     sameCommunityThemePreference(DEFAULT_COMMUNITY_THEME, {
diff --git a/desktop/src/shared/theme/communityThemePreference.ts b/desktop/src/shared/theme/communityThemePreference.ts
index eed642e04..f3457b572 100644
--- a/desktop/src/shared/theme/communityThemePreference.ts
+++ b/desktop/src/shared/theme/communityThemePreference.ts
@@ -12,6 +12,8 @@ import { SYNTAX_THEMES, type SyntaxThemeName } from "./theme-loader";
 const STORAGE_KEY_PREFIX = "buzz-community-theme.v1";
 const OUTBOX_KEY_PREFIX = "buzz-community-theme-outbox.v1";
 const MIGRATION_KEY_PREFIX = "buzz-community-theme-migrated.v1";
+const APPEARANCE_MIGRATION_KEY_PREFIX =
+  "buzz-community-theme-appearance-migrated.v1";
 
 export type CommunityThemePreference = {
   version: 1;
@@ -181,6 +183,29 @@ export function markCommunityThemeMigrated(pubkey: string): void {
   }
 }
 
+export function hasMigratedCommunityThemeAppearance(pubkey: string): boolean {
+  try {
+    return (
+      window.localStorage.getItem(
+        `${APPEARANCE_MIGRATION_KEY_PREFIX}:${pubkey}`,
+      ) === "true"
+    );
+  } catch {
+    return false;
+  }
+}
+
+export function markCommunityThemeAppearanceMigrated(pubkey: string): void {
+  try {
+    window.localStorage.setItem(
+      `${APPEARANCE_MIGRATION_KEY_PREFIX}:${pubkey}`,
+      "true",
+    );
+  } catch {
+    // The expanded preference remains usable in memory when storage is full.
+  }
+}
+
 export function writeCommunityThemePreference(
   pubkey: string,
   relayUrl: string,
@@ -214,6 +239,19 @@ export function communityThemeScopeFallback(
   return migrated ? DEFAULT_COMMUNITY_THEME : inherited;
 }
 
+/**
+ * Choose values for appearance fields missing from the original v1 payload.
+ * This migration is independent from the older per-community scope migration:
+ * profiles that already completed scoping still need one chance to retain
+ * their former global glass and prominent-tab preferences.
+ */
+export function communityThemeAppearanceFallback(
+  migrated: boolean,
+  inherited: CommunityThemePreference,
+): CommunityThemePreference {
+  return migrated ? DEFAULT_COMMUNITY_THEME : inherited;
+}
+
 export function sameCommunityThemePreference(
   left: CommunityThemePreference,
   right: CommunityThemePreference,
diff --git a/mobile/lib/shared/theme/community_theme_preference.dart b/mobile/lib/shared/theme/community_theme_preference.dart
index ae9e9d75b..3b065b5cc 100644
--- a/mobile/lib/shared/theme/community_theme_preference.dart
+++ b/mobile/lib/shared/theme/community_theme_preference.dart
@@ -29,6 +29,9 @@ class CommunityThemePreference {
   final bool glassBackground;
   final int glassOpacity;
   final bool prominentActiveTab;
+  final bool includesGlassBackground;
+  final bool includesGlassOpacity;
+  final bool includesProminentActiveTab;
 
   const CommunityThemePreference({
     this.version = 1,
@@ -38,6 +41,9 @@ class CommunityThemePreference {
     this.glassBackground = defaultCommunityGlassBackground,
     this.glassOpacity = defaultCommunityGlassOpacity,
     this.prominentActiveTab = defaultCommunityProminentActiveTab,
+    this.includesGlassBackground = true,
+    this.includesGlassOpacity = true,
+    this.includesProminentActiveTab = true,
   });
 
   factory CommunityThemePreference.fromJson(Map<String, dynamic> json) {
@@ -49,13 +55,16 @@ class CommunityThemePreference {
         json['followSystem'] is! bool) {
       throw const FormatException('Invalid community theme preference');
     }
-    final glassBackground = json.containsKey('glassBackground')
+    final includesGlassBackground = json.containsKey('glassBackground');
+    final includesGlassOpacity = json.containsKey('glassOpacity');
+    final includesProminentActiveTab = json.containsKey('prominentActiveTab');
+    final glassBackground = includesGlassBackground
         ? json['glassBackground']
         : defaultCommunityGlassBackground;
-    final glassOpacity = json.containsKey('glassOpacity')
+    final glassOpacity = includesGlassOpacity
         ? json['glassOpacity']
         : defaultCommunityGlassOpacity;
-    final prominentActiveTab = json.containsKey('prominentActiveTab')
+    final prominentActiveTab = includesProminentActiveTab
         ? json['prominentActiveTab']
         : defaultCommunityProminentActiveTab;
     if (glassBackground is! bool ||
@@ -74,6 +83,9 @@ class CommunityThemePreference {
       glassBackground: glassBackground,
       glassOpacity: glassOpacity.toInt(),
       prominentActiveTab: prominentActiveTab,
+      includesGlassBackground: includesGlassBackground,
+      includesGlassOpacity: includesGlassOpacity,
+      includesProminentActiveTab: includesProminentActiveTab,
     );
   }
 
@@ -82,9 +94,9 @@ class CommunityThemePreference {
     'theme': theme,
     'accent': accent,
     'followSystem': followSystem,
-    'glassBackground': glassBackground,
-    'glassOpacity': glassOpacity,
-    'prominentActiveTab': prominentActiveTab,
+    if (includesGlassBackground) 'glassBackground': glassBackground,
+    if (includesGlassOpacity) 'glassOpacity': glassOpacity,
+    if (includesProminentActiveTab) 'prominentActiveTab': prominentActiveTab,
   };
 
   CommunityThemePreference copyWith({
@@ -102,6 +114,10 @@ class CommunityThemePreference {
     glassBackground: glassBackground ?? this.glassBackground,
     glassOpacity: glassOpacity ?? this.glassOpacity,
     prominentActiveTab: prominentActiveTab ?? this.prominentActiveTab,
+    includesGlassBackground: glassBackground != null || includesGlassBackground,
+    includesGlassOpacity: glassOpacity != null || includesGlassOpacity,
+    includesProminentActiveTab:
+        prominentActiveTab != null || includesProminentActiveTab,
   );
 
   ThemeMode get mode {
@@ -117,7 +133,10 @@ class CommunityThemePreference {
       followSystem == other.followSystem &&
       glassBackground == other.glassBackground &&
       glassOpacity == other.glassOpacity &&
-      prominentActiveTab == other.prominentActiveTab;
+      prominentActiveTab == other.prominentActiveTab &&
+      includesGlassBackground == other.includesGlassBackground &&
+      includesGlassOpacity == other.includesGlassOpacity &&
+      includesProminentActiveTab == other.includesProminentActiveTab;
 
   @override
   int get hashCode => Object.hash(
@@ -127,6 +146,9 @@ class CommunityThemePreference {
     glassBackground,
     glassOpacity,
     prominentActiveTab,
+    includesGlassBackground,
+    includesGlassOpacity,
+    includesProminentActiveTab,
   );
 }
 
diff --git a/mobile/test/shared/theme/community_theme_preference_test.dart b/mobile/test/shared/theme/community_theme_preference_test.dart
index 1507e3064..b1982b605 100644
--- a/mobile/test/shared/theme/community_theme_preference_test.dart
+++ b/mobile/test/shared/theme/community_theme_preference_test.dart
@@ -1,4 +1,5 @@
 import 'dart:convert';
+import 'dart:io';
 
 import 'package:buzz/shared/theme/theme.dart';
 import 'package:flutter/material.dart';
@@ -24,7 +25,7 @@ void main() {
     );
   });
 
-  test('older v1 payloads gain capability-independent defaults', () {
+  test('older v1 payloads retain missing desktop-only fields', () {
     final preference = CommunityThemePreference.fromJson({
       'version': 1,
       'theme': 'buzz',
@@ -35,7 +36,56 @@ void main() {
     expect(preference.glassBackground, isFalse);
     expect(preference.glassOpacity, 65);
     expect(preference.prominentActiveTab, isFalse);
-    expect(preference.toJson(), containsPair('glassOpacity', 65));
+    expect(preference.toJson(), isNot(contains('glassBackground')));
+    expect(preference.toJson(), isNot(contains('glassOpacity')));
+    expect(preference.toJson(), isNot(contains('prominentActiveTab')));
+  });
+
+  test('mobile edits do not widen legacy appearance fields with defaults', () {
+    final legacy = CommunityThemePreference.fromJson({
+      'version': 1,
+      'theme': 'buzz',
+      'accent': '#3b82f6',
+      'followSystem': true,
+    });
+
+    final edited = legacy.copyWith(accent: '#ef4444');
+
+    expect(edited.toJson(), {
+      'version': 1,
+      'theme': 'buzz',
+      'accent': '#ef4444',
+      'followSystem': true,
+    });
+
+    expect(legacy.copyWith(glassOpacity: 70).toJson(), {
+      'version': 1,
+      'theme': 'buzz',
+      'accent': '#3b82f6',
+      'followSystem': true,
+      'glassOpacity': 70,
+    });
+  });
+
+  test('mobile appearance limits match the shared wire contract', () {
+    final contract =
+        jsonDecode(File('../schema/community-theme-v1.json').readAsStringSync())
+            as Map<String, dynamic>;
+    final properties = contract['properties'] as Map<String, dynamic>;
+    final glassBackground =
+        properties['glassBackground'] as Map<String, dynamic>;
+    final glassOpacity = properties['glassOpacity'] as Map<String, dynamic>;
+    final prominentActiveTab =
+        properties['prominentActiveTab'] as Map<String, dynamic>;
+
+    expect(defaultCommunityGlassBackground, glassBackground['default'] as bool);
+    expect(defaultCommunityGlassOpacity, glassOpacity['default'] as int);
+    expect(minCommunityGlassOpacity, glassOpacity['minimum'] as int);
+    expect(maxCommunityGlassOpacity, glassOpacity['maximum'] as int);
+    expect(
+      defaultCommunityProminentActiveTab,
+      prominentActiveTab['default'] as bool,
+    );
   });
 
   test('rejects invalid theme and appearance values', () {
diff --git a/mobile/test/shared/theme/community_theme_provider_test.dart b/mobile/test/shared/theme/community_theme_provider_test.dart
index 540e0755c..7f0474ec0 100644
--- a/mobile/test/shared/theme/community_theme_provider_test.dart
+++ b/mobile/test/shared/theme/community_theme_provider_test.dart
@@ -11,6 +11,65 @@ import 'package:nostr/nostr.dart' as nostr;
 import 'package:shared_preferences/shared_preferences.dart';
 
 void main() {
+  test(
+    'mobile edit preserves omitted desktop-only fields from a legacy cache',
+    () async {
+      SharedPreferences.setMockInitialValues({});
+      final prefs = await SharedPreferences.getInstance();
+      final keys = nostr.Keys.generate();
+      final storage = CommunityThemeStorage(prefs);
+      await prefs.setString(
+        storage.key(keys.public, 'https://relay.example'),
+        jsonEncode({
+          'version': 1,
+          'theme': 'buzz',
+          'accent': '#3b82f6',
+          'followSystem': true,
+        }),
+      );
+      final session = _ThemeRelaySession(
+        keys.nsec,
+        keys.public,
+        initialStatus: SessionStatus.reconnecting,
+      );
+      final container = ProviderContainer(
+        overrides: [
+          communityThemeStorageProvider.overrideWithValue(storage),
+          relayConfigProvider.overrideWith(() => _RelayConfig(keys.nsec)),
+          relaySessionProvider.overrideWith(() => session),
+        ],
+      );
+      addTearDown(container.dispose);
+      container.listen(
+        communityThemeProvider,
+        (_, _) {},
+        fireImmediately: true,
+      );
+
+      container
+          .read(communityThemeProvider.notifier)
+          .setAccent(accentIndexForWireValue('#ef4444')!);
+
+      await _waitUntil(() {
+        final raw = prefs.getString(
+          storage.key(keys.public, 'https://relay.example'),
+        );
+        if (raw == null) return false;
+        return (jsonDecode(raw) as Map<String, dynamic>)['accent'] == '#ef4444';
+      });
+      final persisted =
+          jsonDecode(
+                prefs.getString(
+                  storage.key(keys.public, 'https://relay.example'),
+                )!,
+              )
+              as Map<String, dynamic>;
+      expect(persisted, isNot(contains('glassBackground')));
+      expect(persisted, isNot(contains('glassOpacity')));
+      expect(persisted, isNot(contains('prominentActiveTab')));
+    },
+  );
+
   test('mobile edits retain desktop-only appearance preferences', () async {
     SharedPreferences.setMockInitialValues({});
     final prefs = await SharedPreferences.getInstance();
diff --git a/schema/community-theme-v1.json b/schema/community-theme-v1.json
new file mode 100644
index 000000000..3ccc5e29e
--- /dev/null
+++ b/schema/community-theme-v1.json
@@ -0,0 +1,44 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://github.com/block/buzz/schema/community-theme-v1.json",
+  "title": "Buzz community theme preference v1",
+  "description": "Canonical completed payload. Clients also accept the original three-field v1 form during migration.",
+  "type": "object",
+  "required": [
+    "version",
+    "theme",
+    "accent",
+    "followSystem",
+    "glassBackground",
+    "glassOpacity",
+    "prominentActiveTab"
+  ],
+  "properties": {
+    "version": {
+      "const": 1
+    },
+    "theme": {
+      "type": "string"
+    },
+    "accent": {
+      "type": "string"
+    },
+    "followSystem": {
+      "type": "boolean"
+    },
+    "glassBackground": {
+      "type": "boolean",
+      "default": false
+    },
+    "glassOpacity": {
+      "type": "integer",
+      "minimum": 30,
+      "maximum": 90,
+      "default": 65
+    },
+    "prominentActiveTab": {
+      "type": "boolean",
+      "default": false
+    }
+  }
+}