From a0c1b8ba31bae253bc96413a7bbe1871944e6d32 Mon Sep 17 00:00:00 2001
From: miteruzo <miteruzo@naver.com>
Date: Sun, 5 Jul 2026 20:18:16 +0900
Subject: [PATCH] #34

---
 frontend/src/App.tsx                     |  39 +-
 frontend/src/components/TopNav.tsx       |  29 +-
 frontend/src/index.css                   |  35 +-
 frontend/src/lib/settings.ts             | 217 ++++++--
 frontend/src/pages/users/SettingPage.tsx | 597 +++++++++++++----------
 5 files changed, 578 insertions(+), 339 deletions(-)

diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index a4cba2f..aa3688b 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -16,12 +16,9 @@ import { applyClientAppearance,
 	 fetchUserThemeSlots,
 	 fetchUserSettings,
 	 getClientThemeMode,
-	 getClientActiveThemeSlot,
 	 hasStoredClientThemeSelection,
-	 normaliseThemeSlotSelectionAgainstSlots,
 	 normaliseUserThemeSlots,
 	 setCachedUserThemeSlots,
-	 setClientActiveThemeSlot,
 	 seedClientThemeMode } from '@/lib/settings'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
 
@@ -182,30 +179,18 @@ const App: FC = () => {
       return
 
     void (async () => {
-      try
-      {
-	const [settings, themeSlots] = await Promise.all ([
-	    fetchUserSettings (),
-	    fetchUserThemeSlots (),
-	])
-	const storedThemeSlots = normaliseUserThemeSlots (themeSlots)
-	const initialSelection = (
-	    hasStoredClientThemeSelection ()
-	    ? getClientActiveThemeSlot ()
-	    : (settings.theme === 'system'
-	       ? 'system'
-	       : `builtin:${ settings.theme }`)
-	)
-	const nextSelection = normaliseThemeSlotSelectionAgainstSlots (
-	    initialSelection,
-	    storedThemeSlots,
-	)
-	setCachedUserThemeSlots (storedThemeSlots)
-	seedClientThemeMode (settings.theme)
-	if (nextSelection !== initialSelection)
-	  setClientActiveThemeSlot (nextSelection)
-	applyClientAppearance ()
-      }
+	try
+	{
+	  const [settings, themeSlots] = await Promise.all ([
+	      fetchUserSettings (),
+	      fetchUserThemeSlots (),
+	  ])
+	  const storedThemeSlots = normaliseUserThemeSlots (themeSlots)
+	  setCachedUserThemeSlots (storedThemeSlots)
+	  if (!(hasStoredClientThemeSelection ()))
+	    seedClientThemeMode (settings.theme)
+	  applyClientAppearance ()
+	}
       catch
       {
 	return
diff --git a/frontend/src/components/TopNav.tsx b/frontend/src/components/TopNav.tsx
index 2b41409..4f1c0d5 100644
--- a/frontend/src/components/TopNav.tsx
+++ b/frontend/src/components/TopNav.tsx
@@ -208,12 +208,11 @@ const TopNav: FC<Props> = ({ user }) => {
 
   return (
       <>
-	<nav className="top-nav-root px-3 flex justify-between items-center w-full
-			border-b">
+	<nav className="top-nav-root px-3 flex justify-between items-center w-full">
 	  <div className="flex items-center gap-2 h-12">
 	    <PrefetchLink
 		to="/posts"
-		className="top-nav-link mx-4 text-xl font-bold"
+		className="top-nav-brand-link mx-4 text-xl font-bold"
 		onClick={() => {
 		  scroll (0, 0)
 		}}>
@@ -245,7 +244,7 @@ const TopNav: FC<Props> = ({ user }) => {
 			ref={(el: (HTMLAnchorElement | null)) => {
 			  itemsRef.current[i] = el
 			}}
-			className={cn ('top-nav-link relative z-10 flex h-full items-center px-5',
+			className={cn ('top-nav-menu-link relative z-10 flex h-full items-center px-5',
 				       (i === openItemIdx) && 'font-bold')}>
 		      {item.name}
 		    </PrefetchLink>
@@ -260,7 +259,7 @@ const TopNav: FC<Props> = ({ user }) => {
 		    setMoreVsbl (true)
 		    measure (-1)
 		  }}
-		  className={cn ('top-nav-link relative z-10 flex h-full items-center px-5',
+		  className={cn ('top-nav-menu-link relative z-10 flex h-full items-center px-5',
 				 (openItemIdx < 0 || moreVsbl) && 'font-bold')}>
 		その他 &raquo;
 	      </PrefetchLink>
@@ -271,7 +270,7 @@ const TopNav: FC<Props> = ({ user }) => {
 
 	  <button
 	     type="button"
-	     className="top-nav-link md:hidden ml-auto border-0 bg-transparent pr-4"
+	     className="top-nav-mobile-toggle md:hidden ml-auto border-0 bg-transparent pr-4"
 	     onClick={() => {
 	       setMenuOpen (!(menuOpen))
 	     }}>
@@ -345,7 +344,7 @@ const TopNav: FC<Props> = ({ user }) => {
 				    to={subItem.to}
 				    target={subItem.to.slice (0, 2) === '//' ? '_blank' : undefined}
 				    onClick={() => setMoreVsbl (false)}
-				    className="top-nav-link h-full flex items-center px-3">
+				    className="top-nav-menu-link h-full flex items-center px-3">
 				  {subItem.name}
 				</PrefetchLink>
 			      </motion.div>)))}
@@ -372,7 +371,7 @@ const TopNav: FC<Props> = ({ user }) => {
 					 target={item.to.slice (0, 2) === '//'
 						 ? '_blank'
 						 : undefined}
-					 className="top-nav-link h-full flex items-center px-3">
+					 className="top-nav-menu-link h-full flex items-center px-3">
 				       {item.name}
 				     </PrefetchLink>
 				   </div>)))}
@@ -411,7 +410,7 @@ const TopNav: FC<Props> = ({ user }) => {
 					   target={item.to.slice (0, 2) === '//'
 						   ? '_blank'
 						   : undefined}
-					   className="top-nav-link h-full flex items-center px-3">
+					   className="top-nav-menu-link h-full flex items-center px-3">
 					 {item.name}
 				       </PrefetchLink>
 				     </motion.div>)))}
@@ -432,7 +431,7 @@ const TopNav: FC<Props> = ({ user }) => {
 		       <Fragment key={i}>
 			 <PrefetchLink
 			     to={i === openItemIdx ? item.to : '#'}
-			     className={cn ('top-nav-link w-full min-h-[40px] flex items-center pl-8',
+			     className={cn ('top-nav-mobile-row w-full min-h-[40px] flex items-center pl-8',
 					((i === openItemIdx)
 					 && 'top-nav-mobile-active font-bold'))}
 			     onClick={(ev: MouseEvent<HTMLAnchorElement>) => {
@@ -462,7 +461,7 @@ const TopNav: FC<Props> = ({ user }) => {
 					   target={subItem.to.slice (0, 2) === '//'
 						   ? '_blank'
 						   : undefined}
-					   className="top-nav-link w-full min-h-[36px] flex items-center pl-12">
+					   className="top-nav-mobile-row w-full min-h-[36px] flex items-center pl-12">
 					 {subItem.name}
 				       </PrefetchLink>)))}
 			     </div>)}
@@ -472,7 +471,7 @@ const TopNav: FC<Props> = ({ user }) => {
 		       ref={(el: (HTMLAnchorElement | null)) => {
 			 itemsRef.current[visibleMenu.length] = el
 		       }}
-		       className={cn ('top-nav-link w-full min-h-[40px] flex items-center pl-8',
+		       className={cn ('top-nav-mobile-row w-full min-h-[40px] flex items-center pl-8',
 				      ((openItemIdx < 0)
 				       && 'top-nav-mobile-active font-bold'))}>
 		     その他 &raquo;
@@ -500,7 +499,7 @@ const TopNav: FC<Props> = ({ user }) => {
 			 <Fragment key={i}>
 			   <PrefetchLink
 			       to={i === openItemIdx ? item.to : '#'}
-			       className={cn ('top-nav-link w-full min-h-[40px] flex items-center pl-8',
+			       className={cn ('top-nav-mobile-row w-full min-h-[40px] flex items-center pl-8',
 					  ((i === openItemIdx)
 					   && 'top-nav-mobile-active font-bold'))}
 			       onClick={(ev: MouseEvent<HTMLAnchorElement>) => {
@@ -543,7 +542,7 @@ const TopNav: FC<Props> = ({ user }) => {
 					       target={subItem.to.slice (0, 2) === '//'
 						       ? '_blank'
 						       : undefined}
-					       className="top-nav-link w-full min-h-[36px] flex items-center pl-12">
+					       className="top-nav-mobile-row w-full min-h-[36px] flex items-center pl-12">
 					     {subItem.name}
 					   </PrefetchLink>)))}
 				 </motion.div>)}
@@ -554,7 +553,7 @@ const TopNav: FC<Props> = ({ user }) => {
 			 ref={(el: (HTMLAnchorElement | null)) => {
 			   itemsRef.current[visibleMenu.length] = el
 			 }}
-			 className={cn ('top-nav-link w-full min-h-[40px] flex items-center pl-8',
+			 className={cn ('top-nav-mobile-row w-full min-h-[40px] flex items-center pl-8',
 					((openItemIdx < 0)
 					 && 'top-nav-mobile-active font-bold'))}>
 		       その他 &raquo;
diff --git a/frontend/src/index.css b/frontend/src/index.css
index 9091484..3ae212b 100644
--- a/frontend/src/index.css
+++ b/frontend/src/index.css
@@ -36,10 +36,11 @@
     --theme-link: 221.2 83.2% 53.3%;
     --top-nav-root-bg-mobile: #fef08a;
     --top-nav-root-bg-desktop: #fefce8;
-    --top-nav-highlight-bg: #fef08a;
+    --top-nav-active-bg: #fef08a;
     --top-nav-submenu-bg: #fef08a;
     --top-nav-mobile-active-bg: #fefce8;
-    --top-nav-link: #db2777;
+    --top-nav-brand-link: #db2777;
+    --top-nav-menu-link: #1d4ed8;
 
     --tag-colour-deerjikist: #9f1239;
     --tag-colour-deerjikist-hover: #b62a51;
@@ -86,10 +87,11 @@
     --ring: 212.7 26.8% 83.9%;
     --top-nav-root-bg-mobile: #230505;
     --top-nav-root-bg-desktop: #230505;
-    --top-nav-highlight-bg: #450a0a;
+    --top-nav-active-bg: #450a0a;
     --top-nav-submenu-bg: #450a0a;
     --top-nav-mobile-active-bg: #450a0a;
-    --top-nav-link: #f9a8d4;
+    --top-nav-brand-link: #f9a8d4;
+    --top-nav-menu-link: #93c5fd;
   }
 
   body
@@ -212,7 +214,6 @@ body
 .top-nav-root
 {
   background: var(--top-nav-root-bg-mobile);
-  border-color: transparent;
 }
 
 @media (min-width: 768px)
@@ -223,19 +224,33 @@ body
   }
 }
 
-.top-nav-link
+.top-nav-brand-link,
+.top-nav-mobile-toggle
 {
-  color: var(--top-nav-link);
+  color: var(--top-nav-brand-link);
 }
 
-.top-nav-link:hover
+.top-nav-brand-link:hover,
+.top-nav-mobile-toggle:hover
 {
-  color: color-mix(in oklab, var(--top-nav-link), white 18%);
+  color: color-mix(in oklab, var(--top-nav-brand-link), white 18%);
+}
+
+.top-nav-menu-link,
+.top-nav-mobile-row
+{
+  color: var(--top-nav-menu-link);
+}
+
+.top-nav-menu-link:hover,
+.top-nav-mobile-row:hover
+{
+  color: color-mix(in oklab, var(--top-nav-menu-link), white 18%);
 }
 
 .top-nav-highlight
 {
-  background: var(--top-nav-highlight-bg);
+  background: var(--top-nav-active-bg);
 }
 
 .top-nav-submenu
diff --git a/frontend/src/lib/settings.ts b/frontend/src/lib/settings.ts
index 0ef15fc..b08fbbf 100644
--- a/frontend/src/lib/settings.ts
+++ b/frontend/src/lib/settings.ts
@@ -15,6 +15,7 @@ export type ThemeTagColours = Record<Category, string>
 export type BuiltinThemeId = 'light' | 'dark'
 export type UserThemeSlotNo = 1 | 2 | 3
 export type UserThemeSlotSelection = `user:${ BuiltinThemeId }:${ UserThemeSlotNo }`
+export type ClientThemeMode = 'system' | 'light' | 'dark'
 export type ThemeSlotSelection =
     | 'system'
     | `builtin:${ BuiltinThemeId }`
@@ -43,13 +44,14 @@ export type ThemeTokens = {
     input:                  string
     ring:                   string
     link:                   string
-    topNavRootBackgroundMobile:  string
-    topNavRootBackgroundDesktop: string
-    topNavHighlightBackground:   string
-    topNavSubmenuBackground:     string
+    topNavRootBackgroundMobile:   string
+    topNavRootBackgroundDesktop:  string
+    topNavActiveBackground:       string
+    topNavSubmenuBackground:      string
     topNavMobileActiveBackground: string
-    topNavLink:                  string
-    tagColours:             ThemeTagColours }
+    topNavBrandLink:             string
+    topNavMenuLink:              string
+    tagColours:                  ThemeTagColours }
 export type UserThemeSlot = {
     baseTheme:   BuiltinThemeId
     slotNo:      UserThemeSlotNo
@@ -63,6 +65,12 @@ export type ResolvedThemeSelection = {
     baseTheme:  BuiltinThemeId
     builtin:    boolean
     tokens:     ThemeTokens }
+export type ResolvedDisplayedTheme = {
+    themeMode:  ClientThemeMode
+    baseTheme:  BuiltinThemeId
+    selection:  UserThemeSlotSelection
+    slotNo:     UserThemeSlotNo
+    tokens:     ThemeTokens }
 export type ClientTheme = {
     id:         ThemeId
     name:       string
@@ -97,6 +105,9 @@ export type ClientKeyboardSettings = {
     bindings?:  Partial<Record<ShortcutActionId, KeyBinding | null>> }
 
 export type ClientAppearanceSettings = {
+    themeMode?:             ClientThemeMode
+    activeLightThemeSlotNo?: UserThemeSlotNo
+    activeDarkThemeSlotNo?: UserThemeSlotNo
     activeThemeSlot?: ThemeSlotSelection
     activeThemeId?: ActiveThemeId
     customThemes?:  Record<string, CustomClientTheme>
@@ -210,13 +221,14 @@ export const LIGHT_THEME_TOKENS: ThemeTokens = {
     input:                 '214.3 31.8% 91.4%',
     ring:                  '222.2 84% 4.9%',
     link:                  '221.2 83.2% 53.3%',
-    topNavRootBackgroundMobile:  '#fef08a',
-    topNavRootBackgroundDesktop: '#fefce8',
-    topNavHighlightBackground:   '#fef08a',
-    topNavSubmenuBackground:     '#fef08a',
+    topNavRootBackgroundMobile:   '#fef08a',
+    topNavRootBackgroundDesktop:  '#fefce8',
+    topNavActiveBackground:       '#fef08a',
+    topNavSubmenuBackground:      '#fef08a',
     topNavMobileActiveBackground: '#fefce8',
-    topNavLink:                  '#db2777',
-    tagColours:            DEFAULT_LIGHT_THEME_TAG_COLOURS }
+    topNavBrandLink:             '#db2777',
+    topNavMenuLink:              '#1d4ed8',
+    tagColours:                  DEFAULT_LIGHT_THEME_TAG_COLOURS }
 export const DARK_THEME_TOKENS: ThemeTokens = {
     background:            '222.2 84% 4.9%',
     foreground:            '210 40% 98%',
@@ -238,13 +250,14 @@ export const DARK_THEME_TOKENS: ThemeTokens = {
     input:                 '217.2 32.6% 17.5%',
     ring:                  '212.7 26.8% 83.9%',
     link:                  '213.1 93.9% 67.8%',
-    topNavRootBackgroundMobile:  '#230505',
-    topNavRootBackgroundDesktop: '#230505',
-    topNavHighlightBackground:   '#450a0a',
-    topNavSubmenuBackground:     '#450a0a',
+    topNavRootBackgroundMobile:   '#230505',
+    topNavRootBackgroundDesktop:  '#230505',
+    topNavActiveBackground:       '#450a0a',
+    topNavSubmenuBackground:      '#450a0a',
     topNavMobileActiveBackground: '#450a0a',
-    topNavLink:                  '#f9a8d4',
-    tagColours:            DEFAULT_DARK_THEME_TAG_COLOURS }
+    topNavBrandLink:             '#f9a8d4',
+    topNavMenuLink:              '#93c5fd',
+    tagColours:                  DEFAULT_DARK_THEME_TAG_COLOURS }
 export const BUILTIN_THEMES: Record<BuiltinThemeId, ClientTheme> = {
     light: {
 	id:         'light',
@@ -356,6 +369,14 @@ const validListLimit = (value: unknown): ClientListLimit | null =>
     value === 20 || value === 50 || value === 100 ? value : null
 
 
+const normaliseThemeMode = (value: unknown): ClientThemeMode | null =>
+    value === 'system' || value === 'light' || value === 'dark' ? value : null
+
+
+const normaliseThemeSlotNo = (value: unknown): UserThemeSlotNo | null =>
+    value === 1 || value === 2 || value === 3 ? value : null
+
+
 const normaliseAnimationMode = (value: unknown): ClientAnimationMode | null => {
   if (value === 'normal' || value === 'reduced' || value === 'off')
     return value
@@ -667,6 +688,9 @@ let cachedUserThemeSlots: UserThemeSlotMap = { }
 export const hasStoredClientThemeSelection = (): boolean => {
   const appearance = appearanceFromSettings ()
   return (
+      appearance.themeMode != null
+      || appearance.activeLightThemeSlotNo != null
+      || appearance.activeDarkThemeSlotNo != null
       appearance.activeThemeSlot != null
       || appearance.activeThemeId != null
       || appearance.customThemes != null
@@ -720,6 +744,31 @@ const legacyThemeSlotSelection = (): ThemeSlotSelection => {
 }
 
 
+const legacyThemeMode = (): ClientThemeMode =>
+    normaliseThemeMode (appearanceFromSettings ().theme)
+    ?? (
+	legacyThemeSlotSelection () === 'system'
+	? 'system'
+	: (baseThemeOfSelection (legacyThemeSlotSelection ()) ?? 'system')
+    )
+
+
+const legacyThemeSlotNoFor = (
+    baseTheme: BuiltinThemeId,
+): UserThemeSlotNo => {
+  const legacySelection = legacyThemeSlotSelection ()
+
+  if (isUserThemeSlotSelection (legacySelection))
+    {
+      const [_, selectionBaseTheme, slotNo] = legacySelection.split (':')
+      if (selectionBaseTheme === baseTheme)
+	return Number (slotNo) as UserThemeSlotNo
+    }
+
+  return 1
+}
+
+
 export const getClientActiveThemeSlot = (): ThemeSlotSelection =>
     normaliseThemeSlotSelection (appearanceFromSettings ().activeThemeSlot)
     ?? legacyThemeSlotSelection ()
@@ -739,21 +788,49 @@ export const setClientActiveThemeSlot = (
 
 
 export const getClientThemeMode = (): UserSettings['theme'] => {
-  const selection = getClientActiveThemeSlot ()
+  return (
+      normaliseThemeMode (appearanceFromSettings ().themeMode)
+      ?? legacyThemeMode ()
+  )
+}
 
-  if (selection === 'system')
-    return 'system'
 
-  return baseThemeOfSelection (selection) ?? DEFAULT_USER_SETTINGS.theme
+export const getClientActiveLightThemeSlotNo = (): UserThemeSlotNo =>
+    normaliseThemeSlotNo (appearanceFromSettings ().activeLightThemeSlotNo)
+    ?? legacyThemeSlotNoFor ('light')
+
+
+export const getClientActiveDarkThemeSlotNo = (): UserThemeSlotNo =>
+    normaliseThemeSlotNo (appearanceFromSettings ().activeDarkThemeSlotNo)
+    ?? legacyThemeSlotNoFor ('dark')
+
+
+export const setClientThemeAppearance = (
+    { themeMode,
+      activeLightThemeSlotNo,
+      activeDarkThemeSlotNo }: {
+	  themeMode:              ClientThemeMode
+	  activeLightThemeSlotNo: UserThemeSlotNo
+	  activeDarkThemeSlotNo:  UserThemeSlotNo },
+): void => {
+  updateClientSettings (settings => ({
+      ...settings,
+      appearance: {
+	  ...(settings.appearance ?? { }),
+	  themeMode,
+	  activeLightThemeSlotNo,
+	  activeDarkThemeSlotNo,
+      },
+  }))
 }
 
 
 export const setClientThemeMode = (theme: UserSettings['theme']): void => {
-  setClientActiveThemeSlot (
-      theme === 'system'
-      ? 'system'
-      : `builtin:${ theme }`,
-  )
+  setClientThemeAppearance ({
+      themeMode: theme,
+      activeLightThemeSlotNo: getClientActiveLightThemeSlotNo (),
+      activeDarkThemeSlotNo: getClientActiveDarkThemeSlotNo (),
+  })
 }
 
 
@@ -893,9 +970,11 @@ const normaliseThemeTokens = (
 	  tokens.topNavRootBackgroundDesktop ?? legacyTopNavTokens.topNavBackground,
 	  fallback.topNavRootBackgroundDesktop,
       ),
-      topNavHighlightBackground: normaliseTopNavColourValue (
-	  tokens.topNavHighlightBackground ?? legacyTopNavTokens.topNavActiveBackground,
-	  fallback.topNavHighlightBackground,
+      topNavActiveBackground: normaliseTopNavColourValue (
+	  tokens.topNavActiveBackground
+	  ?? legacyTopNavTokens.topNavHighlightBackground
+	  ?? legacyTopNavTokens.topNavActiveBackground,
+	  fallback.topNavActiveBackground,
       ),
       topNavSubmenuBackground: normaliseTopNavColourValue (
 	  tokens.topNavSubmenuBackground,
@@ -905,9 +984,16 @@ const normaliseThemeTokens = (
 	  tokens.topNavMobileActiveBackground ?? legacyTopNavTokens.topNavBackground,
 	  fallback.topNavMobileActiveBackground,
       ),
-      topNavLink: normaliseTopNavColourValue (
-	  tokens.topNavLink,
-	  fallback.topNavLink,
+      topNavBrandLink: normaliseTopNavColourValue (
+	  tokens.topNavBrandLink
+	  ?? legacyTopNavTokens.topNavLink,
+	  fallback.topNavBrandLink,
+      ),
+      topNavMenuLink: normaliseTopNavColourValue (
+	  tokens.topNavMenuLink
+	  ?? tokens.link
+	  ?? fallback.topNavMenuLink,
+	  fallback.topNavMenuLink,
       ),
       tagColours: normaliseThemeTagColours (tokens.tagColours, fallback.tagColours),
   }
@@ -1141,6 +1227,33 @@ export const getCachedUserThemeSlots = (): UserThemeSlotMap =>
     cachedUserThemeSlots
 
 
+export const resolveDisplayedTheme = (
+    { themeMode,
+      activeLightThemeSlotNo,
+      activeDarkThemeSlotNo }: {
+	  themeMode:              ClientThemeMode
+	  activeLightThemeSlotNo: UserThemeSlotNo
+	  activeDarkThemeSlotNo:  UserThemeSlotNo },
+    themeSlots: UserThemeSlotMap = getCachedUserThemeSlots (),
+): ResolvedDisplayedTheme => {
+  const baseTheme = resolveThemeMode (themeMode)
+  const slotNo =
+      baseTheme === 'dark'
+      ? activeDarkThemeSlotNo
+      : activeLightThemeSlotNo
+  const selection = getUserThemeSlotSelection (baseTheme, slotNo)
+
+  return {
+      themeMode,
+      baseTheme,
+      selection,
+      slotNo,
+      tokens: themeSlots[selection]?.tokens
+	  ?? getDefaultUserThemeSlot (baseTheme, slotNo).tokens,
+  }
+}
+
+
 export const normaliseThemeSlotSelectionAgainstSlots = (
     selection:   ThemeSlotSelection,
     themeSlots:  UserThemeSlotMap,
@@ -1379,8 +1492,8 @@ export const applyThemeTokens = (tokens: ThemeTokens): void => {
       tokens.topNavRootBackgroundDesktop,
   )
   root.style.setProperty (
-      '--top-nav-highlight-bg',
-      tokens.topNavHighlightBackground,
+      '--top-nav-active-bg',
+      tokens.topNavActiveBackground,
   )
   root.style.setProperty (
       '--top-nav-submenu-bg',
@@ -1391,8 +1504,12 @@ export const applyThemeTokens = (tokens: ThemeTokens): void => {
       tokens.topNavMobileActiveBackground,
   )
   root.style.setProperty (
-      '--top-nav-link',
-      tokens.topNavLink,
+      '--top-nav-brand-link',
+      tokens.topNavBrandLink,
+  )
+  root.style.setProperty (
+      '--top-nav-menu-link',
+      tokens.topNavMenuLink,
   )
 
   applyThemeTagColours (tokens.tagColours)
@@ -1409,10 +1526,34 @@ export const applyThemeSelection = (
 }
 
 
+export const applyThemeAppearanceState = (
+    { themeMode,
+      activeLightThemeSlotNo,
+      activeDarkThemeSlotNo }: {
+	  themeMode:              ClientThemeMode
+	  activeLightThemeSlotNo: UserThemeSlotNo
+	  activeDarkThemeSlotNo:  UserThemeSlotNo },
+    themeSlots: UserThemeSlotMap = getCachedUserThemeSlots (),
+): void => {
+  const theme = resolveDisplayedTheme ({
+      themeMode,
+      activeLightThemeSlotNo,
+      activeDarkThemeSlotNo,
+  }, themeSlots)
+
+  applyThemeMode (theme.baseTheme)
+  applyThemeTokens (theme.tokens)
+}
+
+
 export const applyClientAppearance = (
     themeSlots: UserThemeSlotMap = getCachedUserThemeSlots (),
 ): void => {
-  applyThemeSelection (getClientActiveThemeSlot (), themeSlots)
+  applyThemeAppearanceState ({
+      themeMode: getClientThemeMode (),
+      activeLightThemeSlotNo: getClientActiveLightThemeSlotNo (),
+      activeDarkThemeSlotNo: getClientActiveDarkThemeSlotNo (),
+  }, themeSlots)
 }
 
 
diff --git a/frontend/src/pages/users/SettingPage.tsx b/frontend/src/pages/users/SettingPage.tsx
index 71a7dd0..6c30086 100644
--- a/frontend/src/pages/users/SettingPage.tsx
+++ b/frontend/src/pages/users/SettingPage.tsx
@@ -20,20 +20,20 @@ import { SITE_TITLE } from '@/config'
 import { apiPut } from '@/lib/api'
 import {
     applyClientAppearance,
-    applyThemeSelection,
+    applyThemeAppearanceState,
     DEFAULT_USER_SETTINGS,
-    deriveUserThemeModeFromSlotSelection,
     fetchUserSettings,
     fetchUserThemeSlots,
-    getClientActiveThemeSlot,
+    getClientActiveDarkThemeSlotNo,
+    getClientActiveLightThemeSlotNo,
+    getClientThemeMode,
     getDefaultUserThemeSlot,
     hasStoredClientThemeSelection,
-    isUserThemeSlotSelection,
-    normaliseThemeSlotSelectionAgainstSlots,
+    getUserThemeSlotSelection,
     normaliseUserThemeSlots,
+    resolveDisplayedTheme,
     setCachedUserThemeSlots,
-    setClientActiveThemeSlot,
-    resolveThemeFromSlotSelection,
+    setClientThemeAppearance,
     updateUserSettings,
     upsertUserThemeSlot,
     USER_THEME_SLOT_SELECTIONS,
@@ -47,8 +47,8 @@ import type { CSSProperties, Dispatch, FC, KeyboardEvent, SetStateAction } from
 import type { Category, Tag, User } from '@/types'
 import type {
     BuiltinThemeId,
+    ClientThemeMode,
     ClientTheme,
-    ThemeSlotSelection,
     ThemeTokens,
     ThemeTagColours,
     UserSettings,
@@ -80,12 +80,15 @@ type AccountSectionProps = {
     userBaseErrors:   string[]
     userFieldErrors:  Partial<Record<UserFormField, string[]>> }
 
+type ThemeModeItem = {
+    id:     ClientThemeMode
+    label:  string }
+
 type ThemeSelectionItem = {
-    id:         ThemeSlotSelection
-    label:      string
-    editable:   boolean
-    baseTheme?: BuiltinThemeId
-    slotNo?:    UserThemeSlotNo }
+    id:        UserThemeSlotSelection
+    label:     string
+    baseTheme: BuiltinThemeId
+    slotNo:    UserThemeSlotNo }
 
 type ThemeTokenFieldSpec = {
     key:    ThemeTokenKey
@@ -96,17 +99,20 @@ type ThemeTokenGroupSpec = {
     fields:  ThemeTokenFieldSpec[] }
 
 type ThemeSectionProps = {
-    draftActiveThemeSlot:    ThemeSlotSelection
-    draftThemeSlots:         UserThemeSlotMap
-    editingThemeSlot:        UserThemeSlotSelection | null
+    draftThemeMode:          ClientThemeMode
+    draftActiveLightThemeSlotNo: UserThemeSlotNo
+    draftActiveDarkThemeSlotNo: UserThemeSlotNo
+    editingThemeSlot:        UserThemeSlotSelection
     selectedTheme:           ClientTheme
-    selectedThemeLabel:      string
+    displayedThemeLabel:     string
+    systemThemeLabel:        string
     hasUnsavedChanges:       boolean
     settingsBaseErrors:      string[]
     settingsFieldErrors:     Partial<Record<SettingsFormField, string[]>>
-    onSelectThemeSlot:       (selection: ThemeSlotSelection) => void
-    onEditThemeSlot:         (selection: UserThemeSlotSelection) => void
-    onEnsureEditableTheme:   () => void
+    onSelectThemeMode:       (themeMode: ClientThemeMode) => void
+    onSelectLightThemeSlotNo: (slotNo: UserThemeSlotNo) => void
+    onSelectDarkThemeSlotNo: (slotNo: UserThemeSlotNo) => void
+    onSelectEditingThemeSlot: (selection: UserThemeSlotSelection) => void
     onThemeTokenChange:      (key: ThemeTokenKey, value: string) => void
     onTagColourChange:       (category: Category, colour: string) => void
     onResetThemeSlot:        (selection: UserThemeSlotSelection) => void
@@ -117,25 +123,34 @@ type SettingsTabDirtyState = {
     dirty:    boolean
     discard:  () => void | Promise<void> }
 
+type ThemeDraftState = {
+    themeMode:              ClientThemeMode
+    activeLightThemeSlotNo: UserThemeSlotNo
+    activeDarkThemeSlotNo:  UserThemeSlotNo
+    themeSlots:             UserThemeSlotMap
+    editingThemeSlot:       UserThemeSlotSelection }
+
 const tabs: TabSpec[] = [
     { id: 'account', label: 'アカウント' },
     { id: 'behavior', label: '動作' },
     { id: 'theme', label: 'テーマ' },
     { id: 'keyboard', label: 'キーボード' } ]
 
+const themeModeSelections: ThemeModeItem[] = [
+    { id: 'system', label: 'システム設定に従う' },
+    { id: 'light', label: 'ライト' },
+    { id: 'dark', label: 'ダーク' } ]
+
 const sectionClassName =
     'space-y-4 rounded-xl border border-border bg-background/80 p-4'
 
 const themeSelections: ThemeSelectionItem[] = [
-    { id: 'system', label: 'システム設定', editable: false },
-    { id: 'builtin:light', label: '標準ライト', editable: false },
-    { id: 'builtin:dark', label: '標準ダーク', editable: false },
-    { id: 'user:light:1', label: 'ライト 1', editable: true, baseTheme: 'light', slotNo: 1 },
-    { id: 'user:light:2', label: 'ライト 2', editable: true, baseTheme: 'light', slotNo: 2 },
-    { id: 'user:light:3', label: 'ライト 3', editable: true, baseTheme: 'light', slotNo: 3 },
-    { id: 'user:dark:1', label: 'ダーク 1', editable: true, baseTheme: 'dark', slotNo: 1 },
-    { id: 'user:dark:2', label: 'ダーク 2', editable: true, baseTheme: 'dark', slotNo: 2 },
-    { id: 'user:dark:3', label: 'ダーク 3', editable: true, baseTheme: 'dark', slotNo: 3 },
+    { id: 'user:light:1', label: 'ライト 1', baseTheme: 'light', slotNo: 1 },
+    { id: 'user:light:2', label: 'ライト 2', baseTheme: 'light', slotNo: 2 },
+    { id: 'user:light:3', label: 'ライト 3', baseTheme: 'light', slotNo: 3 },
+    { id: 'user:dark:1', label: 'ダーク 1', baseTheme: 'dark', slotNo: 1 },
+    { id: 'user:dark:2', label: 'ダーク 2', baseTheme: 'dark', slotNo: 2 },
+    { id: 'user:dark:3', label: 'ダーク 3', baseTheme: 'dark', slotNo: 3 },
 ]
 
 const themeTokenGroups: ThemeTokenGroupSpec[] = [
@@ -159,12 +174,13 @@ const themeTokenGroups: ThemeTokenGroupSpec[] = [
       ] },
     { title: '上部ナビ',
       fields: [
-	  { key: 'topNavRootBackgroundMobile', label: '通常背景' },
+	  { key: 'topNavRootBackgroundMobile', label: 'スマホ背景' },
 	  { key: 'topNavRootBackgroundDesktop', label: 'PC 背景' },
-	  { key: 'topNavHighlightBackground', label: '選択中背景' },
+	  { key: 'topNavActiveBackground', label: '選択中背景' },
 	  { key: 'topNavSubmenuBackground', label: 'サブメニュー背景' },
 	  { key: 'topNavMobileActiveBackground', label: 'スマホ選択中背景' },
-	  { key: 'topNavLink', label: 'リンク' },
+	  { key: 'topNavBrandLink', label: 'ロゴ色' },
+	  { key: 'topNavMenuLink', label: 'メニュー文字色' },
       ] },
 ]
 
@@ -215,8 +231,8 @@ const themePreviewStyle = (tagColours: ThemeTagColours): CSSProperties =>
 	    [`--tag-colour-${ category }`, tagColours[category]],
 	    [`--tag-colour-${ category }-hover`, tagColours[category]]])) as CSSProperties
 
-const themeLabelBySelection = (selection: ThemeSlotSelection): string =>
-    themeSelections.find (item => item.id === selection)?.label ?? 'システム設定'
+const themeLabelBySelection = (selection: UserThemeSlotSelection): string =>
+    themeSelections.find (item => item.id === selection)?.label ?? 'ライト 1'
 
 const ensureCompleteThemeSlots = (
     themeSlots: UserThemeSlotMap,
@@ -236,31 +252,21 @@ const ensureCompleteThemeSlots = (
     )
 
 const serialiseThemeDraft = (
-    activeThemeSlot: ThemeSlotSelection,
-    themeSlots:      UserThemeSlotMap,
+    themeMode:              ClientThemeMode,
+    activeLightThemeSlotNo: UserThemeSlotNo,
+    activeDarkThemeSlotNo:  UserThemeSlotNo,
+    themeSlots:             UserThemeSlotMap,
 ): string =>
     JSON.stringify ({
-	activeThemeSlot,
+	themeMode,
+	activeLightThemeSlotNo,
+	activeDarkThemeSlotNo,
 	themeSlots: USER_THEME_SLOT_SELECTIONS.map (selection => ({
 	    selection,
 	    tokens: themeSlots[selection]?.tokens,
 	})),
     })
 
-const themeToSelection = (
-    theme: UserSettings['theme'],
-): ThemeSlotSelection =>
-    theme === 'system'
-    ? 'system'
-    : `builtin:${ theme }`
-
-const themeRowBaseLabel = (
-    selection: ThemeSlotSelection,
-): string =>
-    selection === 'system'
-    ? '端末設定に従います'
-    : themeLabelBySelection (selection)
-
 
 const isTopNavThemeTokenKey = (key: ThemeTokenKey): boolean =>
     key.startsWith ('topNav')
@@ -447,32 +453,27 @@ const AccountSection: FC<AccountSectionProps> = (
     </section>)
 
 const ThemeSection: FC<ThemeSectionProps> = (
-    { draftActiveThemeSlot,
-      draftThemeSlots,
+    { draftThemeMode,
+      draftActiveLightThemeSlotNo,
+      draftActiveDarkThemeSlotNo,
       editingThemeSlot,
       selectedTheme,
-      selectedThemeLabel,
+      displayedThemeLabel,
+      systemThemeLabel,
       hasUnsavedChanges,
       settingsBaseErrors,
       settingsFieldErrors,
-      onSelectThemeSlot,
-      onEditThemeSlot,
-      onEnsureEditableTheme,
+      onSelectThemeMode,
+      onSelectLightThemeSlotNo,
+      onSelectDarkThemeSlotNo,
+      onSelectEditingThemeSlot,
       onThemeTokenChange,
       onTagColourChange,
       onResetThemeSlot,
       onThemeSubmit,
       onThemeDiscard },
 ) => {
-  const currentSelection =
-      themeSelections.find (item => item.id === draftActiveThemeSlot)
-      ?? themeSelections[0]
-  const currentEditableSelection =
-      editingThemeSlot
-      ?? (isUserThemeSlotSelection (draftActiveThemeSlot)
-	  ? draftActiveThemeSlot
-	  : null)
-  const canEditTheme = currentEditableSelection != null
+  const currentEditableSelection = editingThemeSlot
 
   return (
       <section className={sectionClassName}>
@@ -480,12 +481,15 @@ const ThemeSection: FC<ThemeSectionProps> = (
 	  <div className="space-y-1">
 	    <h2 className="text-xl font-bold">テーマ</h2>
 	    <p className="text-sm text-muted-foreground">
-	      現在の表示: {selectedThemeLabel}
+	      現在表示中: {displayedThemeLabel}
 	    </p>
-	    {editingThemeSlot && (
+	    {draftThemeMode === 'system' && (
 		<p className="text-sm text-muted-foreground">
-		  編輯対象: {themeLabelBySelection (editingThemeSlot)}
+		  システム設定: {systemThemeLabel}
 		</p>)}
+	    <p className="text-sm text-muted-foreground">
+	      編輯対象: {themeLabelBySelection (currentEditableSelection)}
+	    </p>
 	    {hasUnsavedChanges && (
 		<p className="text-sm text-amber-700 dark:text-amber-300">
 		  未保存の変更があります
@@ -514,13 +518,60 @@ const ThemeSection: FC<ThemeSectionProps> = (
 
 	<div className="space-y-3 rounded-xl border border-border/70 bg-background/70 p-4">
 	  <div className="space-y-2">
-	    <Label>保存する枠</Label>
-	    <div className="flex flex-col gap-2 sm:flex-row sm:flex-wrap sm:items-center">
+	    <Label>表示モード</Label>
+	    <select
+		className={inputClass (false)}
+		value={draftThemeMode}
+		onChange={ev =>
+		    onSelectThemeMode (ev.target.value as ClientThemeMode)}>
+	      {themeModeSelections.map (selection => (
+		    <option key={selection.id} value={selection.id}>
+		      {selection.label}
+		    </option>))}
+	    </select>
+	  </div>
+
+	  <div className="space-y-2">
+	    <Label>ライト用テーマ</Label>
+	    <select
+		className={inputClass (false)}
+		value={draftActiveLightThemeSlotNo}
+		onChange={ev =>
+		    onSelectLightThemeSlotNo (Number (ev.target.value) as UserThemeSlotNo)}>
+	      {themeSelections
+	       .filter (selection => selection.baseTheme === 'light')
+	       .map (selection => (
+		   <option key={selection.id} value={selection.slotNo}>
+		     {selection.label}
+		   </option>))}
+	    </select>
+	  </div>
+
+	  <div className="space-y-2">
+	    <Label>ダーク用テーマ</Label>
+	    <select
+		className={inputClass (false)}
+		value={draftActiveDarkThemeSlotNo}
+		onChange={ev =>
+		    onSelectDarkThemeSlotNo (Number (ev.target.value) as UserThemeSlotNo)}>
+	      {themeSelections
+	       .filter (selection => selection.baseTheme === 'dark')
+	       .map (selection => (
+		   <option key={selection.id} value={selection.slotNo}>
+		     {selection.label}
+		   </option>))}
+	    </select>
+	  </div>
+
+	  <div className="space-y-2">
+	    <Label htmlFor="theme-slot-select">編輯対象</Label>
+	    <div className="flex flex-col gap-2 sm:flex-row sm:items-center">
 	      <select
+		  id="theme-slot-select"
 		  className={cn (inputClass (false), 'w-full min-w-0 sm:w-64')}
-		  value={draftActiveThemeSlot}
+		  value={currentEditableSelection}
 		  onChange={ev =>
-		      onSelectThemeSlot (ev.target.value as ThemeSlotSelection)}>
+		      onSelectEditingThemeSlot (ev.target.value as UserThemeSlotSelection)}>
 		{themeSelections.map (selection => (
 		    <option key={selection.id} value={selection.id}>
 		      {selection.label}
@@ -529,43 +580,15 @@ const ThemeSection: FC<ThemeSectionProps> = (
 
 	      <Button
 		  type="button"
-		  variant="outline"
-		  onClick={() => {
-		    if (isUserThemeSlotSelection (draftActiveThemeSlot))
-		      {
-			onEditThemeSlot (draftActiveThemeSlot)
-			return
-		      }
-
-		    onEnsureEditableTheme ()
-		  }}>
-		{canEditTheme ? 'この枠を編輯' : '編輯する枠を選ぶ'}
+		  variant="ghost"
+		  onClick={() => onResetThemeSlot (currentEditableSelection)}>
+		既定に戻す
 	      </Button>
-
-	      {currentEditableSelection && (
-		  <Button
-		      type="button"
-		      variant="ghost"
-		      onClick={() => onResetThemeSlot (currentEditableSelection)}>
-		    既定に戻す
-		  </Button>)}
 	    </div>
 	  </div>
 
-	  <div className="space-y-1">
-	    <p className="text-sm font-semibold">{currentSelection.label}</p>
-	    <p className="text-sm text-muted-foreground">
-	      {themeRowBaseLabel (currentSelection.id)}
-	    </p>
-	    {canEditTheme
-	     ? (
-		 <p className="text-sm text-muted-foreground">
-		   この枠への変更は保存時に反映されます。
-		 </p>)
-	     : (
-		 <p className="text-sm text-muted-foreground">
-		   標準テーマは直接編輯できません。編輯する枠を選んでください。
-		 </p>)}
+	  <div className="space-y-1 text-sm text-muted-foreground">
+	    <p>変更は保存時に反映されます。</p>
 	  </div>
 
 	  <div style={themePreviewStyle (selectedTheme.tokens.tagColours)}>
@@ -593,10 +616,9 @@ const ThemeSection: FC<ThemeSectionProps> = (
 			  <p className="text-sm font-medium">{field.label}</p>
 			</div>
 			<div className="flex flex-wrap items-center gap-3">
-			  <input
+			 <input
 			      type="color"
 			      value={themeTokenToHex (field.key, selectedTheme.tokens[field.key])}
-			      disabled={!(canEditTheme)}
 			      onChange={ev =>
 				  onThemeTokenChange (field.key, hexToThemeToken (field.key, ev.target.value))}
 			      className="h-10 w-16 cursor-pointer rounded border border-border
@@ -635,7 +657,6 @@ const ThemeSection: FC<ThemeSectionProps> = (
 		      <input
 			  type="color"
 			  value={selectedTheme.tokens.tagColours[category]}
-			  disabled={!(canEditTheme)}
 			  onChange={ev => onTagColourChange (category, ev.target.value)}
 			  className="h-10 w-16 cursor-pointer rounded border border-border
 				     bg-transparent p-1 disabled:cursor-not-allowed
@@ -659,16 +680,26 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
   const [name, setName] = useState ('')
   const [settingsError, setSettingsError] = useState<string | null> (null)
   const [, setDraftSettings] = useState<UserSettings> (DEFAULT_USER_SETTINGS)
-  const [savedActiveThemeSlot, setSavedActiveThemeSlot] =
-      useState<ThemeSlotSelection> (getClientActiveThemeSlot ())
-  const [draftActiveThemeSlot, setDraftActiveThemeSlot] =
-      useState<ThemeSlotSelection> (getClientActiveThemeSlot ())
+  const [savedThemeMode, setSavedThemeMode] =
+      useState<ClientThemeMode> (getClientThemeMode ())
+  const [draftThemeMode, setDraftThemeMode] =
+      useState<ClientThemeMode> (getClientThemeMode ())
+  const [savedActiveLightThemeSlotNo, setSavedActiveLightThemeSlotNo] =
+      useState<UserThemeSlotNo> (getClientActiveLightThemeSlotNo ())
+  const [draftActiveLightThemeSlotNo, setDraftActiveLightThemeSlotNo] =
+      useState<UserThemeSlotNo> (getClientActiveLightThemeSlotNo ())
+  const [savedActiveDarkThemeSlotNo, setSavedActiveDarkThemeSlotNo] =
+      useState<UserThemeSlotNo> (getClientActiveDarkThemeSlotNo ())
+  const [draftActiveDarkThemeSlotNo, setDraftActiveDarkThemeSlotNo] =
+      useState<UserThemeSlotNo> (getClientActiveDarkThemeSlotNo ())
   const [savedThemeSlots, setSavedThemeSlots] =
       useState<UserThemeSlotMap> (() => ensureCompleteThemeSlots ({ }))
   const [draftThemeSlots, setDraftThemeSlots] =
       useState<UserThemeSlotMap> (() => ensureCompleteThemeSlots ({ }))
+  const [savedEditingThemeSlot, setSavedEditingThemeSlot] =
+      useState<UserThemeSlotSelection> ('user:light:1')
   const [editingThemeSlot, setEditingThemeSlot] =
-      useState<UserThemeSlotSelection | null> (null)
+      useState<UserThemeSlotSelection> ('user:light:1')
   const [dirtyStates, setDirtyStates] =
       useState<Partial<Record<SettingsTab, SettingsTabDirtyState>>> ({ })
   const [userCodeVsbl, setUserCodeVsbl] = useState (false)
@@ -684,25 +715,59 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
       useValidationErrors<SettingsFormField> ()
 
   const activeTab = useMemo<SettingsTab> (() => parseTab (location.search), [location.search])
+  const displayedThemeSelection = useMemo (
+      () => resolveDisplayedTheme ({
+	  themeMode: draftThemeMode,
+	  activeLightThemeSlotNo: draftActiveLightThemeSlotNo,
+	  activeDarkThemeSlotNo: draftActiveDarkThemeSlotNo,
+      }, draftThemeSlots),
+      [draftActiveDarkThemeSlotNo,
+       draftActiveLightThemeSlotNo,
+       draftThemeMode,
+       draftThemeSlots],
+  )
   const selectedTheme = useMemo<ClientTheme> (
       () => {
-	  const resolvedTheme =
-	      resolveThemeFromSlotSelection (draftActiveThemeSlot, draftThemeSlots)
+	  const currentSelection =
+	      themeSelections.find (selection => selection.id === editingThemeSlot)
+	      ?? themeSelections[0]
+	  const themeSlot =
+	      draftThemeSlots[currentSelection.id]
+	      ?? getDefaultUserThemeSlot (currentSelection.baseTheme, currentSelection.slotNo)
 	  return {
-	      id: resolvedTheme.baseTheme,
-	      name: themeLabelBySelection (draftActiveThemeSlot),
-	      builtin: resolvedTheme.builtin,
-	      baseTheme: resolvedTheme.baseTheme,
-	      tokens: resolvedTheme.tokens,
+	      id: currentSelection.baseTheme,
+	      name: themeLabelBySelection (currentSelection.id),
+	      builtin: false,
+	      baseTheme: currentSelection.baseTheme,
+	      tokens: themeSlot.tokens,
 	  }
       },
-      [draftActiveThemeSlot, draftThemeSlots],
+      [draftThemeSlots, editingThemeSlot],
   )
   const hasUnsavedThemeChanges = useMemo (
       () =>
-	  serialiseThemeDraft (draftActiveThemeSlot, draftThemeSlots)
-	  !== serialiseThemeDraft (savedActiveThemeSlot, savedThemeSlots),
-      [draftActiveThemeSlot, draftThemeSlots, savedActiveThemeSlot, savedThemeSlots],
+	  serialiseThemeDraft (
+	      draftThemeMode,
+	      draftActiveLightThemeSlotNo,
+	      draftActiveDarkThemeSlotNo,
+	      draftThemeSlots,
+	  )
+	  !== serialiseThemeDraft (
+	      savedThemeMode,
+	      savedActiveLightThemeSlotNo,
+	      savedActiveDarkThemeSlotNo,
+	      savedThemeSlots,
+	  ),
+      [draftActiveDarkThemeSlotNo,
+       draftActiveLightThemeSlotNo,
+       draftThemeMode,
+       draftThemeSlots,
+       editingThemeSlot,
+       savedActiveDarkThemeSlotNo,
+       savedActiveLightThemeSlotNo,
+       savedEditingThemeSlot,
+       savedThemeMode,
+       savedThemeSlots],
   )
 
   const applyActiveTab = (tab: SettingsTab) => {
@@ -753,25 +818,63 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
       [conflictActionIds.size, settingsFieldErrors.theme, userFieldErrors.name],
   )
 
-  const applyDraftThemeSelection = (
-      activeThemeSlot: ThemeSlotSelection,
-      themeSlots:      UserThemeSlotMap,
+  const applyDraftThemeState = (
+      { themeMode = draftThemeMode,
+	 activeLightThemeSlotNo = draftActiveLightThemeSlotNo,
+	 activeDarkThemeSlotNo = draftActiveDarkThemeSlotNo,
+	 themeSlots = draftThemeSlots,
+	 nextEditingThemeSlot = editingThemeSlot }: {
+	     themeMode?:               ClientThemeMode
+	     activeLightThemeSlotNo?:  UserThemeSlotNo
+	     activeDarkThemeSlotNo?:   UserThemeSlotNo
+	     themeSlots?:              UserThemeSlotMap
+	     nextEditingThemeSlot?:    UserThemeSlotSelection },
   ) => {
-    setDraftActiveThemeSlot (activeThemeSlot)
+    setDraftThemeMode (themeMode)
+    setDraftActiveLightThemeSlotNo (activeLightThemeSlotNo)
+    setDraftActiveDarkThemeSlotNo (activeDarkThemeSlotNo)
     setDraftThemeSlots (themeSlots)
+    setEditingThemeSlot (nextEditingThemeSlot)
     setDraftSettings (current => ({
 	...current,
-	theme: deriveUserThemeModeFromSlotSelection (activeThemeSlot),
+	theme: themeMode,
     }))
-    applyThemeSelection (activeThemeSlot, themeSlots)
+    setCachedUserThemeSlots (themeSlots)
+    applyThemeAppearanceState ({
+	themeMode,
+	activeLightThemeSlotNo,
+	activeDarkThemeSlotNo,
+    }, themeSlots)
   }
 
+  const currentThemeDraftState = (): ThemeDraftState => ({
+      themeMode: draftThemeMode,
+      activeLightThemeSlotNo: draftActiveLightThemeSlotNo,
+      activeDarkThemeSlotNo: draftActiveDarkThemeSlotNo,
+      themeSlots: draftThemeSlots,
+      editingThemeSlot,
+  })
+
+  const savedThemeDraftState = (): ThemeDraftState => ({
+      themeMode: savedThemeMode,
+      activeLightThemeSlotNo: savedActiveLightThemeSlotNo,
+      activeDarkThemeSlotNo: savedActiveDarkThemeSlotNo,
+      themeSlots: savedThemeSlots,
+      editingThemeSlot: savedEditingThemeSlot,
+  })
+
   const discardThemeChanges = () => {
-    setDraftActiveThemeSlot (savedActiveThemeSlot)
+    setDraftThemeMode (savedThemeMode)
+    setDraftActiveLightThemeSlotNo (savedActiveLightThemeSlotNo)
+    setDraftActiveDarkThemeSlotNo (savedActiveDarkThemeSlotNo)
     setDraftThemeSlots (savedThemeSlots)
-    setEditingThemeSlot (null)
+    setEditingThemeSlot (savedEditingThemeSlot)
     setCachedUserThemeSlots (savedThemeSlots)
-    setClientActiveThemeSlot (savedActiveThemeSlot)
+    setClientThemeAppearance ({
+	themeMode: savedThemeMode,
+	activeLightThemeSlotNo: savedActiveLightThemeSlotNo,
+	activeDarkThemeSlotNo: savedActiveDarkThemeSlotNo,
+    })
     applyClientAppearance (savedThemeSlots)
   }
 
@@ -800,66 +903,42 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
     applyActiveTab (nextTab)
   }
 
-  const requestThemeSlotSelection = async (
-      selection:    ThemeSlotSelection,
-      editingSlot:  UserThemeSlotSelection | null,
+  const requestThemeStateChange = async (
+      buildNextState: (baseState: ThemeDraftState) => ThemeDraftState,
+      description = 'このまま切り替えると、保存していない変更は失われます。',
+      cancelText = 'このまま編集する',
+      confirmText = '変更を破棄して切り替える',
   ): Promise<void> => {
-    if (
-	selection === draftActiveThemeSlot
-	&& editingSlot === editingThemeSlot
-    )
-      return
+    const baseState =
+	hasUnsavedThemeChanges
+	? savedThemeDraftState ()
+	: currentThemeDraftState ()
 
     if (hasUnsavedThemeChanges)
       {
 	const confirmed = await confirmDiscardChanges (
-	    'このまま切り替えると、保存していない変更は失われます。',
-	    'この枠に残る',
-	    '変更を破棄して切り替える',
+	    description,
+	    cancelText,
+	    confirmText,
 	)
 	if (!(confirmed))
 	  return
-
-	discardThemeChanges ()
       }
 
-    setEditingThemeSlot (editingSlot)
-    applyDraftThemeSelection (selection, savedThemeSlots)
-  }
+    const nextState = buildNextState (baseState)
 
-  const ensureEditableThemeSlot = async (): Promise<UserThemeSlotSelection | null> => {
-    if (editingThemeSlot != null)
-      return editingThemeSlot
-    if (isUserThemeSlotSelection (draftActiveThemeSlot))
-      {
-	setEditingThemeSlot (draftActiveThemeSlot)
-	return draftActiveThemeSlot
-      }
-
-    const choice = await dialogue.choice<UserThemeSlotSelection> ({
-	title: '保存先を選択してください',
-	description: '色を変更する前に、保存先のテーマ枠を選択してください。',
-	cancelText: '取消',
-	choices: themeSelections
-	    .filter (selection => selection.editable)
-	    .map (selection => ({
-		value: selection.id as UserThemeSlotSelection,
-		label: selection.label,
-	    })),
+    applyDraftThemeState ({
+	themeMode: nextState.themeMode,
+	activeLightThemeSlotNo: nextState.activeLightThemeSlotNo,
+	activeDarkThemeSlotNo: nextState.activeDarkThemeSlotNo,
+	themeSlots: nextState.themeSlots,
+	nextEditingThemeSlot: nextState.editingThemeSlot,
     })
-
-    if (choice == null)
-      return null
-
-    setEditingThemeSlot (choice)
-    applyDraftThemeSelection (choice, savedThemeSlots)
-    return choice
   }
 
   const updateDraftThemeSlot = (
       selection: UserThemeSlotSelection,
       updater:   (tokens: ThemeTokens) => ThemeTokens,
-      options?:  { activeThemeSlot?: ThemeSlotSelection },
   ) => {
     const currentThemeSlot =
 	draftThemeSlots[selection]
@@ -872,10 +951,10 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
 	},
     }
 
-    applyDraftThemeSelection (
-	options?.activeThemeSlot ?? draftActiveThemeSlot,
-	nextThemeSlots,
-    )
+    applyDraftThemeState ({
+	themeSlots: nextThemeSlots,
+	nextEditingThemeSlot: selection,
+    })
   }
 
   const handleTabKeyDown = (event: KeyboardEvent<HTMLButtonElement>) => {
@@ -944,8 +1023,7 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
 	  const draftThemeSlot = draftThemeSlots[selection]
 	  const savedThemeSlot = savedThemeSlots[selection]
 	  const requiresPersist =
-	      selection === draftActiveThemeSlot
-	      && isUserThemeSlotSelection (draftActiveThemeSlot)
+	      selection === editingThemeSlot
 	      && savedThemeSlot?.createdAt == null
 
 	  if (
@@ -969,21 +1047,22 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
 	  }
 	}
 
-      const themeMode =
-	  deriveUserThemeModeFromSlotSelection (draftActiveThemeSlot)
-      const data = await updateUserSettings ({ theme: themeMode })
+      const data = await updateUserSettings ({ theme: draftThemeMode })
       const completeThemeSlots = ensureCompleteThemeSlots (nextSavedThemeSlots)
 
-      setDraftSettings ({ ...data, theme: themeMode })
-      setSavedActiveThemeSlot (draftActiveThemeSlot)
+      setDraftSettings ({ ...data, theme: draftThemeMode })
+      setSavedThemeMode (draftThemeMode)
+      setSavedActiveLightThemeSlotNo (draftActiveLightThemeSlotNo)
+      setSavedActiveDarkThemeSlotNo (draftActiveDarkThemeSlotNo)
       setSavedThemeSlots (completeThemeSlots)
       setDraftThemeSlots (completeThemeSlots)
-      setEditingThemeSlot (
-	  isUserThemeSlotSelection (draftActiveThemeSlot)
-	  ? draftActiveThemeSlot
-	  : null,
-      )
-      setClientActiveThemeSlot (draftActiveThemeSlot)
+      setSavedEditingThemeSlot (editingThemeSlot)
+      setEditingThemeSlot (editingThemeSlot)
+      setClientThemeAppearance ({
+	  themeMode: draftThemeMode,
+	  activeLightThemeSlotNo: draftActiveLightThemeSlotNo,
+	  activeDarkThemeSlotNo: draftActiveDarkThemeSlotNo,
+      })
       setCachedUserThemeSlots (completeThemeSlots)
       applyClientAppearance (completeThemeSlots)
       toast ({ title: 'テーマ設定を保存しました．' })
@@ -1026,31 +1105,35 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
 
 	const storedThemeSlots = normaliseUserThemeSlots (themeSlots)
 	const completeThemeSlots = ensureCompleteThemeSlots (storedThemeSlots)
-	const initialSelection = (
+	const themeMode =
 	    hasStoredClientThemeSelection ()
-	    ? getClientActiveThemeSlot ()
-	    : themeToSelection (settings.theme)
-	)
-	const nextSelection = normaliseThemeSlotSelectionAgainstSlots (
-	    initialSelection,
-	    storedThemeSlots,
-	)
-	const themeMode = deriveUserThemeModeFromSlotSelection (nextSelection)
+	    ? getClientThemeMode ()
+	    : settings.theme
+	const activeLightThemeSlotNo = getClientActiveLightThemeSlotNo ()
+	const activeDarkThemeSlotNo = getClientActiveDarkThemeSlotNo ()
+	const initialEditingThemeSlot = resolveDisplayedTheme ({
+	    themeMode,
+	    activeLightThemeSlotNo,
+	    activeDarkThemeSlotNo,
+	}, completeThemeSlots).selection
 
 	setDraftSettings ({ ...settings, theme: themeMode })
-	setSavedActiveThemeSlot (nextSelection)
-	setDraftActiveThemeSlot (nextSelection)
+	setSavedThemeMode (themeMode)
+	setDraftThemeMode (themeMode)
+	setSavedActiveLightThemeSlotNo (activeLightThemeSlotNo)
+	setDraftActiveLightThemeSlotNo (activeLightThemeSlotNo)
+	setSavedActiveDarkThemeSlotNo (activeDarkThemeSlotNo)
+	setDraftActiveDarkThemeSlotNo (activeDarkThemeSlotNo)
 	setSavedThemeSlots (completeThemeSlots)
 	setDraftThemeSlots (completeThemeSlots)
-	setEditingThemeSlot (
-	    isUserThemeSlotSelection (nextSelection)
-	    ? nextSelection
-	    : null,
-	)
+	setSavedEditingThemeSlot (initialEditingThemeSlot)
+	setEditingThemeSlot (initialEditingThemeSlot)
 	setCachedUserThemeSlots (completeThemeSlots)
-	applyThemeSelection (nextSelection, completeThemeSlots)
-	if (nextSelection !== initialSelection)
-	  setClientActiveThemeSlot (nextSelection)
+	applyThemeAppearanceState ({
+	    themeMode,
+	    activeLightThemeSlotNo,
+	    activeDarkThemeSlotNo,
+	}, completeThemeSlots)
 	setSettingsError (null)
       }
       catch
@@ -1083,12 +1166,21 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
   }, [location.pathname, location.search, settingsFieldErrors.theme])
 
   useEffect (() => {
-    applyThemeSelection (draftActiveThemeSlot, draftThemeSlots)
+    applyThemeAppearanceState ({
+	themeMode: draftThemeMode,
+	activeLightThemeSlotNo: draftActiveLightThemeSlotNo,
+	activeDarkThemeSlotNo: draftActiveDarkThemeSlotNo,
+    }, draftThemeSlots)
 
     return () => {
-      applyThemeSelection (savedActiveThemeSlot, savedThemeSlots)
+      setCachedUserThemeSlots (savedThemeSlots)
+      applyClientAppearance (savedThemeSlots)
     }
-  }, [draftActiveThemeSlot, draftThemeSlots, savedActiveThemeSlot, savedThemeSlots])
+  }, [draftActiveDarkThemeSlotNo,
+      draftActiveLightThemeSlotNo,
+      draftThemeMode,
+      draftThemeSlots,
+      savedThemeSlots])
 
   const accountSectionProps: AccountSectionProps | null =
       user
@@ -1109,7 +1201,7 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
 	dirty: hasUnsavedThemeChanges,
 	discard: handleThemeDiscard,
     })
-  }, [hasUnsavedThemeChanges, savedActiveThemeSlot, savedThemeSlots])
+  }, [hasUnsavedThemeChanges, savedThemeSlots])
 
   useKeyboardShortcuts ({
       'settings.account': () => {
@@ -1127,49 +1219,56 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
   })
 
   const themeSectionProps: ThemeSectionProps = {
-      draftActiveThemeSlot,
-      draftThemeSlots,
+      draftThemeMode,
+      draftActiveLightThemeSlotNo,
+      draftActiveDarkThemeSlotNo,
       editingThemeSlot,
       selectedTheme,
-      selectedThemeLabel: themeLabelBySelection (draftActiveThemeSlot),
+      displayedThemeLabel: themeLabelBySelection (displayedThemeSelection.selection),
+      systemThemeLabel: displayedThemeSelection.baseTheme === 'dark' ? 'ダーク' : 'ライト',
       hasUnsavedChanges: hasUnsavedThemeChanges,
       settingsBaseErrors,
       settingsFieldErrors,
-      onSelectThemeSlot: selection => {
-	  void requestThemeSlotSelection (selection, null)
+      onSelectThemeMode: themeMode => {
+	  void requestThemeStateChange (baseState => ({
+	      ...baseState,
+	      themeMode,
+	  }))
       },
-      onEditThemeSlot: selection => {
-	  void requestThemeSlotSelection (selection, selection)
+      onSelectLightThemeSlotNo: slotNo => {
+	  void requestThemeStateChange (baseState => ({
+	      ...baseState,
+		  activeLightThemeSlotNo: slotNo,
+		  editingThemeSlot: getUserThemeSlotSelection ('light', slotNo),
+	      }))
       },
-      onEnsureEditableTheme: () => {
-	  void ensureEditableThemeSlot ()
+      onSelectDarkThemeSlotNo: slotNo => {
+	  void requestThemeStateChange (baseState => ({
+	      ...baseState,
+		  activeDarkThemeSlotNo: slotNo,
+		  editingThemeSlot: getUserThemeSlotSelection ('dark', slotNo),
+	      }))
+      },
+      onSelectEditingThemeSlot: selection => {
+	  void requestThemeStateChange (baseState => ({
+	      ...baseState,
+	      editingThemeSlot: selection,
+	  }))
       },
       onThemeTokenChange: (key, value) => {
-	  void (async () => {
-	      const editableThemeSlot = await ensureEditableThemeSlot ()
-	      if (editableThemeSlot == null)
-		return
-
-	      updateDraftThemeSlot (editableThemeSlot, tokens => ({
-		  ...tokens,
-		  [key]: value,
-	      }), { activeThemeSlot: editableThemeSlot })
-	  }) ()
+	  updateDraftThemeSlot (editingThemeSlot, tokens => ({
+	      ...tokens,
+	      [key]: value,
+	  }))
       },
       onTagColourChange: (category, colour) => {
-	  void (async () => {
-	      const editableThemeSlot = await ensureEditableThemeSlot ()
-	      if (editableThemeSlot == null)
-		return
-
-	      updateDraftThemeSlot (editableThemeSlot, tokens => ({
-		  ...tokens,
-		  tagColours: {
-		      ...tokens.tagColours,
-		      [category]: colour,
-		  },
-	      }), { activeThemeSlot: editableThemeSlot })
-	  }) ()
+	  updateDraftThemeSlot (editingThemeSlot, tokens => ({
+	      ...tokens,
+	      tagColours: {
+		  ...tokens.tagColours,
+		  [category]: colour,
+	      },
+	  }))
       },
       onResetThemeSlot: selection => {
 	  const baseTheme =