#445

backend/db/migrate/20261108000000_add_linked_tag_ids_to_nico_tag_versions.rb

@@ -0,0 +1,5 @@
+class AddLinkedTagIdsToNicoTagVersions < ActiveRecord::Migration[8.0]
+  def change
+    add_column :nico_tag_versions, :linked_tag_ids, :text
+  end
+end

backend/db/migrate/20261108010000_migrate_linked_tags_in_nico_tag_versions.rb

@@ -0,0 +1,42 @@
+class MigrateLinkedTagsInNicoTagVersions < ActiveRecord::Migration[8.0]
+  class MigrationTagVersion < ActiveRecord::Base
+    self.table_name = 'tag_versions'
+  end
+
+  class MigrationNicoTagVersion < ActiveRecord::Base
+    self.table_name = 'nico_tag_versions'
+  end
+
+  def up
+    # 除票外部タグの恢復はないので除票履歴があれば全消しでよいはず．
+    execute <<~SQL
+      DELETE
+        t1
+      FROM
+        nico_tag_versions t1
+        INNER JOIN
+          nico_tag_versions t2
+          ON
+            t1.tag_id = t2.tag_id
+            AND t2.event_type = 'discard'
+    SQL
+
+    MigrationNicoTagVersion.find_each do |ntv|
+      linked_tag_ids = ntv.linked_tags.split.map { |name|
+        # 厳密には一意ぢゃないけどめんだぅだからこれでいいや．
+        MigrationTagVersion
+            .order(created_at: :desc, id: :desc)
+            .find_by("names ->> '$.ja.name' = ?", name)
+            &.tag_id
+      }.compact.uniq.sort.join(' ')
+
+      ntv.update_columns(linked_tag_ids:)
+    end
+
+    change_column_null :nico_tag_versions, :linked_tag_ids, false
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, '戻せません．'
+  end
+end

backend/db/migrate/20261108020000_remove_linked_tags_from_nico_tag_versions.rb

@@ -0,0 +1,6 @@
+class RemoveLinkedTagsFromNicoTagVersions < ActiveRecord::Migration[8.0]
+  def change
+    remove_column :nico_tag_versions, :linked_tags
+    remove_column :nico_tag_versions, :name
+  end
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
+ActiveRecord::Schema[8.0].define(version: 2026_11_08_020000) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -301,10 +301,9 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
     t.bigint "tag_id", null: false
     t.integer "version_no", null: false
     t.string "event_type", null: false
-    t.string "name", null: false
-    t.text "linked_tags", null: false
     t.datetime "created_at", null: false
     t.bigint "created_by_user_id"
+    t.text "linked_tag_ids", null: false
     t.index ["created_at"], name: "index_nico_tag_versions_on_created_at"
     t.index ["created_by_user_id", "created_at"], name: "index_nico_tag_versions_on_created_by_user_id_and_created_at", order: { created_at: :desc }
     t.index ["tag_id", "created_at"], name: "index_nico_tag_versions_on_tag_id_and_created_at", order: { created_at: :desc }

frontend/public/fonts/noto-sans-mongolian/LICENSE

@@ -1,94 +0,0 @@
-Copyright 2018 The Noto Project Authors (github.com/googlei18n/noto-fonts)
-
-This Font Software is licensed under the SIL Open Font License,
-Version 1.1.
-
-This license is copied below, and is also available with a FAQ at:
-http://scripts.sil.org/OFL
-
------------------------------------------------------------
-SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
------------------------------------------------------------
-
-PREAMBLE
-The goals of the Open Font License (OFL) are to stimulate worldwide
-development of collaborative font projects, to support the font
-creation efforts of academic and linguistic communities, and to
-provide a free and open framework in which fonts may be shared and
-improved in partnership with others.
-
-The OFL allows the licensed fonts to be used, studied, modified and
-redistributed freely as long as they are not sold by themselves. The
-fonts, including any derivative works, can be bundled, embedded,
-redistributed and/or sold with any software provided that any reserved
-names are not used by derivative works. The fonts and derivatives,
-however, cannot be released under any other type of license. The
-requirement for fonts to remain under this license does not apply to
-any document created using the fonts or their derivatives.
-
-DEFINITIONS
-"Font Software" refers to the set of files released by the Copyright
-Holder(s) under this license and clearly marked as such. This may
-include source files, build scripts and documentation.
-
-"Reserved Font Name" refers to any names specified as such after the
-copyright statement(s).
-
-"Original Version" refers to the collection of Font Software
-components as distributed by the Copyright Holder(s).
-
-"Modified Version" refers to any derivative made by adding to,
-deleting, or substituting -- in part or in whole -- any of the
-components of the Original Version, by changing formats or by porting
-the Font Software to a new environment.
-
-"Author" refers to any designer, engineer, programmer, technical
-writer or other person who contributed to the Font Software.
-
-PERMISSION & CONDITIONS
-Permission is hereby granted, free of charge, to any person obtaining
-a copy of the Font Software, to use, study, copy, merge, embed,
-modify, redistribute, and sell modified and unmodified copies of the
-Font Software, subject to the following conditions:
-
-1) Neither the Font Software nor any of its individual components, in
-Original or Modified Versions, may be sold by itself.
-
-2) Original or Modified Versions of the Font Software may be bundled,
-redistributed and/or sold with any software, provided that each copy
-contains the above copyright notice and this license. These can be
-included either as stand-alone text files, human-readable headers or
-in the appropriate machine-readable metadata fields within text or
-binary files as long as those fields can be easily viewed by the user.
-
-3) No Modified Version of the Font Software may use the Reserved Font
-Name(s) unless explicit written permission is granted by the
-corresponding Copyright Holder. This restriction only applies to the
-primary font name as presented to the users.
-
-4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
-Software shall not be used to promote, endorse or advertise any
-Modified Version, except to acknowledge the contribution(s) of the
-Copyright Holder(s) and the Author(s) or with their explicit written
-permission.
-
-5) The Font Software, modified or unmodified, in part or in whole,
-must be distributed entirely under this license, and must not be
-distributed under any other license. The requirement for fonts to
-remain under this license does not apply to any document created using
-the Font Software.
-
-TERMINATION
-This license becomes null and void if any of the above conditions are
-not met.
-
-DISCLAIMER
-THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
-MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
-OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
-COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
-INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
-DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
-FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
-OTHER DEALINGS IN THE FONT SOFTWARE.

frontend/public/fonts/noto-sans-mongolian/SOURCE.md

@@ -1,11 +0,0 @@
-Noto Sans Mongolian Regular, unmodified TrueType font.
-
-Font copyright: Copyright 2018 Google Inc. All Rights Reserved.
-
-- Source: https://github.com/notofonts/noto-fonts/tree/main/hinted/ttf/NotoSansMongolian
-- Font: https://raw.githubusercontent.com/notofonts/noto-fonts/main/hinted/ttf/NotoSansMongolian/NotoSansMongolian-Regular.ttf
-- License: SIL Open Font License 1.1; see the accompanying LICENSE.
-- Retrieved: 2026-11-08.
-
-Used only by the Unicode Mongolian sample in the development layout route.
-The font and license are served together from this directory.

frontend/src/App.tsx

@@ -20,13 +20,13 @@ import { Toaster } from '@/components/ui/toaster'
 import { isApiError } from '@/lib/api'
 import { initialiseUserSession } from '@/lib/users'
 import { prepareHelpPage } from '@/lib/help'
-import { fetchLocales, isLocaleCode, isVerticalPreviewPath, legacyLocalePath,
-	 localiseTo, switchLocalePath, unlocalisedPath } from '@/lib/locales'
+import { fetchLocales, isLocaleCode, legacyLocalePath,
+	 switchLocalePath, unlocalisedPath } from '@/lib/locales'
 import { isAuthorityDependentQuery, localesKeys, sessionKeys } from '@/lib/queryKeys'
 import { isCountsPath } from '@/lib/routeLocales'
 import { switchPostFilterLocale } from '@/lib/posts'
 import { switchWikiLocale } from '@/lib/wiki'
-import { useLocale, useVerticalPreview } from '@/lib/useLocale'
+import { useLocale } from '@/lib/useLocale'
 import { applyClientAnimationMode,
 	 applyClientAppearance,
 	 fetchUserThemeSlots,
@@ -267,7 +267,6 @@ const RoutedApp = ({ locales }: { locales: AvailableLocale[] }) => {
   const client = useQueryClient ()
   const location = useLocation ()
   const locale = useLocale ()
-  const verticalPreview = useVerticalPreview ()
   const route = resolvePageRoute (location.pathname)
   const robots = isCountsPath (location.pathname) ? 'noindex' : route?.route.handle?.robots
   const pagePath = unlocalisedPath (location.pathname)
@@ -394,8 +393,7 @@ const RoutedApp = ({ locales }: { locales: AvailableLocale[] }) => {
 	      <motion.div
 		  layout={(animationMode === 'off' || countsPage) ? false : 'position'}
 		  transition={{ layout: appLayoutTransition }}
-		  data-vertical-preview={verticalPreview || undefined}
-		  className="app-layout relative flex h-dvh w-full flex-col overflow-y-hidden">
+		  className="relative flex h-dvh w-full flex-col overflow-y-hidden">
 		<TopNav user={user} locales={locales} resolveLocaleSwitch={switchLocale}/>
 		<RouteTransitionWrapper
 		    user={user}
@@ -414,7 +412,6 @@ const RoutedApp = ({ locales }: { locales: AvailableLocale[] }) => {
 const LocaleRoute: FC = () => {
   const { locale } = useParams ()
   const location = useLocation ()
-  const verticalPreview = isVerticalPreviewPath (location.pathname)
   const { i18n } = useTranslation ()
   const { data, isError } = useQuery ({
       queryKey: localesKeys.index,
@@ -424,11 +421,10 @@ const LocaleRoute: FC = () => {
       refetchOnMount: true,
       refetchOnWindowFocus: true,
       refetchOnReconnect: true })
-  const contentLocale = verticalPreview ? 'ja' : locale
   const activeLocale =
-      (isLocaleCode (contentLocale)
-       && data?.locales.some (entry => entry.code === contentLocale))
-      ? contentLocale
+      (isLocaleCode (locale)
+       && data?.locales.some (entry => entry.code === locale))
+      ? locale
       : null
 
   useLayoutEffect (() => {
@@ -439,15 +435,15 @@ const LocaleRoute: FC = () => {
   }, [activeLocale, i18n])
 
   const redirect = legacyLocalePath (location, pathname => resolvePageRoute (pathname) != null)
-  if (!(isLocaleCode (locale)) && !verticalPreview && redirect == null)
+  if (!(isLocaleCode (locale)) && redirect == null)
     return <NotFound/>
   if (isError && data == null)
     return <ServiceUnavailable/>
   if (data == null)
     return null
-  if (isLocaleCode (locale) || verticalPreview)
+  if (isLocaleCode (locale))
   {
-    return data.locales.some (entry => entry.code === contentLocale)
+    return data.locales.some (entry => entry.code === locale)
         ? <RoutedApp locales={data.locales}/>
         : <NotFound/>
   }
@@ -459,8 +455,7 @@ const LocaleRoute: FC = () => {
 const LocaleRedirect = ({ to }: { to: string }) => {
   const locale = useLocale ()
   const location = useLocation ()
-  return <Navigate to={localiseTo (
-      { ...location, pathname: to }, locale, location.pathname)} replace/>
+  return <Navigate to={switchLocalePath ({ ...location, pathname: to }, locale)} replace/>
 }
 
 

frontend/src/components/PostList.tsx

@@ -34,7 +34,7 @@ const PostList: FC<Props> = ({ posts, onClick }) => {
   const cardRef = useRef<HTMLDivElement> (null)
 
   return (
-      <div className="post-list flex flex-wrap gap-6 p-4">
+      <div className="flex flex-wrap gap-6 p-4">
 	{posts.map ((post, i) => {
 	  const sharedId = `page-${ post.id }`
 	  const layoutId = sharedId

frontend/src/components/PrefetchLink.tsx

@@ -1,10 +1,9 @@
 import { useQueryClient } from '@tanstack/react-query'
 import { forwardRef, useMemo } from 'react'
 import { flushSync } from 'react-dom'
-import { createPath, useLocation } from 'react-router-dom'
+import { createPath } from 'react-router-dom'
 
-import { isVerticalPreviewPath, localeFromPath,
-	 localiseTo, unlocalisedPath } from '@/lib/locales'
+import { localiseTo } from '@/lib/locales'
 import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
 import { useOverlayStore } from '@/components/RouteBlockerOverlay'
 import { prefetchForURL } from '@/lib/prefetchers'
@@ -39,18 +38,15 @@ export default forwardRef<HTMLAnchorElement, Props> (({
 
   const navigate = useLocaleNavigate ()
   const locale = useLocale ()
-  const { pathname } = useLocation ()
   const qc = useQueryClient ()
   const behaviourSettings = useClientBehaviourSettings ()
   const linkPreloadMode = behaviourSettings.linkPreload ?? 'intent'
   const path = useMemo (
       () => {
-	const localised = localiseTo (to, locale, pathname)
-	const destination = typeof localised === 'string' ? localised : createPath (localised)
-	return (isVerticalPreviewPath (pathname) && localeFromPath (destination) === locale)
-	    ? `/mn-Mong${ unlocalisedPath (destination) }` : destination
+	const localised = localiseTo (to, locale)
+	return typeof localised === 'string' ? localised : createPath (localised)
       },
-      [to, locale, pathname],
+      [to, locale],
   )
   const url = useMemo (() => {
     return (new URL (path, currentRenderContext ()?.origin ?? 'http://localhost')).toString ()

frontend/src/components/TopNav.tsx

@@ -4,7 +4,7 @@ import { Globe } from 'lucide-react'
 import { Fragment, useEffect, useLayoutEffect, useRef, useState } from 'react'
 import { useLocation } from 'react-router-dom'
 
-import { useLocale, useLocaleNavigate, useVerticalPreview } from '@/lib/useLocale'
+import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
 import LocalisedText, { formatUIString } from '@/components/LocalisedText'
 import Separator from '@/components/MenuSeparator'
 import PrefetchLink from '@/components/PrefetchLink'
@@ -137,7 +137,6 @@ export const menuOutline = (
 const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
   const { message, label } = useUITranslation ('shared')
   const locale = useLocale ()
-  const verticalPreview = useVerticalPreview ()
   const localeName = locales.find (entry => entry.code === locale)?.name
   const navigate = useLocaleNavigate ()
   const location = useLocation ()
@@ -181,12 +180,11 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
     let node: HTMLElement | null = el
     while (node != null && node !== nav)
     {
-      left += verticalPreview ? node.offsetTop : node.offsetLeft
+      left += node.offsetLeft
       const parent: Element | null = node.offsetParent
       node = parent instanceof HTMLElement ? parent : null
     }
-    const width = node === nav
-	? (verticalPreview ? el.offsetHeight : el.offsetWidth) : 0
+    const width = node === nav ? el.offsetWidth : 0
     const visible = width > 0
     setHL (current =>
 	(current.left === left && current.width === width && current.visible === visible)
@@ -204,7 +202,6 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
   const [moreVsbl, setMoreVsbl] = useState (false)
   const [openItemIdx, setOpenItemIdx] = useState (-1)
   const [submenuHeight, setSubmenuHeight] = useState (0)
-  const [submenuWidth, setSubmenuWidth] = useState (0)
   const [wikiId, setWikiId] = useState<number | null> (WikiIdBus.get ())
 
   const wikiIdStr = String (wikiId ?? '')
@@ -258,22 +255,8 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
       animationsOff
       ? undefined
       : (reducedAnimations
-	 ? 'transition-[transform,width,height] duration-75 ease-linear'
-	 : 'transition-[transform,width,height] duration-200 ease-out')
-  const submenuItemMotion = animationsOff ? { } : {
-      initial: { x: verticalPreview ? -40 : 0,
-	  y: verticalPreview ? 0 : -40, opacity: 0 },
-      animate: { x: 0, y: 0, opacity: 1 },
-      exit: { x: verticalPreview ? -40 : 0,
-	  y: verticalPreview ? 0 : -40, opacity: 0 } }
-  const submenuVariants = {
-      enter: (direction: -1 | 1) => ({
-	  x: verticalPreview ? direction * 24 : 0,
-	  y: verticalPreview ? 0 : direction * 24, opacity: 0 }),
-      centre: { x: 0, y: 0, opacity: 1 },
-      exit: (direction: -1 | 1) => ({
-	  x: verticalPreview ? (-direction) * 24 : 0,
-	  y: verticalPreview ? 0 : (-direction) * 24, opacity: 0 }) }
+	 ? 'transition-[transform,width] duration-75 ease-linear'
+	 : 'transition-[transform,width] duration-200 ease-out')
 
   const prevActiveIdxRef = useRef<number> (activeIdx)
 
@@ -304,14 +287,6 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 	return
       }
 
-      if (verticalPreview)
-      {
-	setDesktop (true)
-	setDensity ('auto')
-	measure (moreVsbl ? -1 : activeIdx)
-	return
-      }
-
       // Measure the same desktop elements while the mobile layout is active.
       layout.setAttribute ('data-measuring', '')
       const previousDensity = layout.getAttribute ('data-density') ?? 'auto'
@@ -376,8 +351,7 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
       removeEventListener ('resize', schedule)
       document.fonts?.removeEventListener ('loadingdone', schedule)
     }
-  }, [activeIdx, moreVsbl, desktop, density, user?.name, locale, locales,
-      menuLabels, verticalPreview])
+  }, [activeIdx, moreVsbl, desktop, density, user?.name, locale, locales, menuLabels])
 
   useEffect (() => {
     if (desktop == null || layoutReady)
@@ -404,8 +378,7 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
     measure (moreVsbl ? -1 : activeIdx)
     if (!(desktop))
       setMoreVsbl (false)
-  }, [activeIdx, moreVsbl, desktop, density, locale, animationMode,
-      menuLabels, verticalPreview])
+  }, [activeIdx, moreVsbl, desktop, density, locale, animationMode, menuLabels])
 
   useEffect (() => {
     const unsubscribe = WikiIdBus.subscribe (setWikiId)
@@ -419,7 +392,6 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 
     const update = () => {
       setSubmenuHeight (Math.ceil (content.getBoundingClientRect ().height))
-      setSubmenuWidth (Math.ceil (content.getBoundingClientRect ().width))
     }
     const observer =
 	typeof ResizeObserver === 'undefined' ? null : new ResizeObserver (update)
@@ -431,7 +403,7 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
       observer?.disconnect ()
       removeEventListener ('resize', update)
     }
-  }, [activeIdx, moreVsbl, desktop, density, locale, verticalPreview])
+  }, [activeIdx, moreVsbl, desktop, density, locale])
 
   useEffect (() => {
     setMenuOpen (false)
@@ -507,11 +479,8 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 		   className={cn ('absolute inset-y-0 h-12',
 				  'top-nav-highlight',
 				  highlightTransitionClass)}
-		   style={{ width:      verticalPreview ? '100%' : hl.width,
-			    height:     verticalPreview ? hl.width : undefined,
-			    transform:  verticalPreview
-				? `translateY(${ hl.left }px)`
-				: `translateX(${ hl.left }px)`,
+		   style={{ width:      hl.width,
+			    transform:  `translateX(${ hl.left }px)`,
 			    opacity:    hl.visible ? 1 : 0 }}/>
 
 	      {visibleMenu.map ((item, i) => (
@@ -560,18 +529,10 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 	  <div className="top-nav-account ml-auto flex min-w-0 items-center gap-2">
 	    <TopNavUser user={user}/>
 	    {localeSelector}
-	    {verticalPreview && (
-		<span className="vertical-preview-sample" lang="mn-Mong">
-		  ᠮᠣᠩᠭᠣᠯ
-		</span>)}
 	  </div>
 
 	  <div className="top-nav-mobile-controls ml-auto flex shrink-0 items-center gap-2">
 	    {menuOpen && localeSelector}
-	    {verticalPreview && (
-		<span className="vertical-preview-sample" lang="mn-Mong">
-		  ᠮᠣᠩᠭᠣᠯ
-		</span>)}
 	    <button
 		type="button"
 		className="top-nav-mobile-toggle shrink-0 whitespace-nowrap
@@ -593,9 +554,7 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 	      layout
 	      className="top-nav-desktop-submenu relative z-20 shrink-0
 			 overflow-hidden top-nav-submenu"
-	      animate={verticalPreview && desktop
-		  ? { width: submenuWidth, height: '100%' }
-		  : { width: 'auto', height: desktop == null ? 'auto' : submenuHeight }}
+	      animate={{ height: desktop == null ? 'auto' : submenuHeight }}
 	      onMouseLeave={() => {
 		if (moreVsbl)
 		  setMoreVsbl (false)
@@ -607,8 +566,7 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 	      onLayoutAnimationComplete={() => {
 		measure (highlightTargetRef.current)
 	      }}>
-	  <div ref={submenuContentRef}
-	      className={cn ('top-nav-submenu-content', moreVsbl && 'top-nav-more-menu')}>
+	  <div ref={submenuContentRef} className={cn (moreVsbl && 'top-nav-more-menu')}>
 	  {moreVsbl
 	   ? (
 	      moreMenu.map ((item, i) => (
@@ -618,11 +576,9 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 			  {...((item.visible ?? true)
 			       ? { layoutId: `menu-${ menu.indexOf (item) }` }
 			       : (animationsOff ? { }
-				  : { initial: {
-					  x: 40, y: verticalPreview ? 0 : -40, opacity: 0 },
+				  : { initial: { x: 40, y: -40, opacity: 0 },
 				      animate: { x: 0, y: 0, opacity: 1 },
-				      exit: {
-					  x: 40, y: verticalPreview ? 0 : -40, opacity: 0 } }))}
+				      exit: { x: 40, y: -40, opacity: 0 } }))}
 			  onLayoutAnimationComplete={() => measure (highlightTargetRef.current)}
 			  className="z-10 min-w-0 px-3 py-2 font-bold">
 			<h2>
@@ -643,7 +599,10 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 				  transition={topNavTransition}
 				  {...(visibleMenu[activeIdx] === item
 				       ? { layoutId: `submenu-${ menu.indexOf (item) }-${ j }` }
-				       : submenuItemMotion)}>
+				       : (animationsOff ? { }
+					  : { initial: { y: -40, opacity: 0 },
+					      animate: { y: 0, opacity: 1 },
+					      exit: { y: -40, opacity: 0 } }))}>
 				{subItem.component}
 			      </motion.div>)
 			  : (
@@ -653,7 +612,10 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 				  transition={topNavTransition}
 				  {...(visibleMenu[activeIdx] === item
 				       ? { layoutId: `submenu-${ menu.indexOf (item) }-${ j }` }
-				       : submenuItemMotion)}>
+				       : (animationsOff ? { }
+					  : { initial: { y: -40, opacity: 0 },
+					      animate: { y: 0, opacity: 1 },
+					      exit: { y: -40, opacity: 0 } }))}>
 				<PrefetchLink
 				    to={subItem.to}
 				    target={subItem.to.slice (0, 2) === '//' ? '_blank' : undefined}
@@ -671,8 +633,7 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 		  <div className="relative min-h-[40px]">
 		    {animationsOff
 		     ? (
-			 <div className="top-nav-submenu-items flex min-h-[40px]
-					 flex-wrap items-center px-3">
+			 <div className="flex min-h-[40px] flex-wrap items-center px-3">
 			   {(visibleMenu[activeIdx]?.subMenu ?? [])
 			    .filter (item => item.visible ?? true)
 			    .map ((item, i) => (
@@ -701,9 +662,10 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 			   <motion.div
 			       key={activeIdx}
 			       custom={dir}
-			       variants={submenuVariants}
-			       className="top-nav-submenu-items relative flex min-h-[40px]
-					  flex-wrap items-center px-3"
+			       variants={{ enter: (d: -1 | 1) => ({ y: d * 24, opacity: 0 }),
+					   centre: { y: 0, opacity: 1 },
+					   exit: (d: -1 | 1) => ({ y: (-d) * 24, opacity: 0 }) }}
+			       className="relative flex min-h-[40px] flex-wrap items-center px-3"
 			       initial="enter"
 			       animate="centre"
 			       exit="exit"

frontend/src/components/layout/MainArea.tsx

@@ -1,10 +1,7 @@
 import { motion } from 'framer-motion'
-import { useEffect, useRef } from 'react'
-import { useLocation } from 'react-router-dom'
 
 import { clientAnimationTransition } from '@/lib/clientAnimation'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
-import { useVerticalPreview } from '@/lib/useLocale'
 import { cn } from '@/lib/utils'
 
 import type { FC, ReactNode } from 'react'
@@ -12,71 +9,21 @@ import type { FC, ReactNode } from 'react'
 type Props = {
     children:   ReactNode
     className?: string
-    animateLayout?: boolean
-    verticalContent?: boolean }
+    animateLayout?: boolean }
 
 
-const MainArea: FC<Props> = (
-    { children, className, animateLayout = true, verticalContent = false },
-) => {
+const MainArea: FC<Props> = ({ children, className, animateLayout = true }) => {
   const behaviourSettings = useClientBehaviourSettings ()
-  const verticalPreview = useVerticalPreview ()
-  const horizontal = verticalPreview && verticalContent
-  const { pathname, search } = useLocation ()
-  const rootRef = useRef<HTMLElement | null> (null)
   const animationMode = behaviourSettings.animation ?? 'normal'
   const layoutTransition = clientAnimationTransition (
       animationMode,
-      { normal: { duration: .2, ease: 'easeOut' as const } })
-
-  useEffect (() => {
-    if (horizontal && rootRef.current != null)
-      rootRef.current.scrollLeft = 0
-  }, [horizontal, pathname, search])
-
-  useEffect (() => {
-    const root = rootRef.current
-    if (!horizontal || root == null)
-      return
-
-    const handleWheel = (event: WheelEvent) => {
-      if (event.ctrlKey || event.metaKey || event.shiftKey
-	  || event.deltaX !== 0 || event.deltaY === 0 || event.defaultPrevented)
-	return
-
-      // Nested tables, forms and code blocks retain their own scrolling.
-      let node = event.target instanceof HTMLElement ? event.target : null
-      while (node != null && node !== root)
-      {
-	if (node.matches ('input, select, textarea, [contenteditable="true"]'))
-	  return
-	const style = getComputedStyle (node)
-	if ((/auto|scroll/.test (style.overflowY) && node.scrollHeight > node.clientHeight)
-	    || (/auto|scroll/.test (style.overflowX) && node.scrollWidth > node.clientWidth))
-	  return
-	node = node.parentElement
-      }
-
-      const unit = event.deltaMode === 1 ? 16 : (event.deltaMode === 2 ? root.clientWidth : 1)
-      const delta = event.deltaY * unit
-      if ((delta < 0 && root.scrollLeft <= 0)
-	  || (delta > 0 && root.scrollLeft + root.clientWidth >= root.scrollWidth))
-	return
-      event.preventDefault ()
-      root.scrollLeft += delta
-    }
-
-    root.addEventListener ('wheel', handleWheel, { passive: false })
-    return () => root.removeEventListener ('wheel', handleWheel)
-  }, [horizontal])
+      { normal: { duration: .2, ease: 'easeOut' as const } },
+  )
 
   return (
       <motion.main
-	  ref={rootRef}
-	  data-vertical-content={horizontal || undefined}
-	  tabIndex={horizontal ? 0 : undefined}
 	  transition={{ layout: layoutTransition }}
-	  className={cn ('main-area flex-1 overflow-y-auto p-4', className)}
+	  className={cn ('flex-1 overflow-y-auto p-4', className)}
 	  layout={(animationMode === 'off' || !animateLayout) ? false : 'position'}>
 	{children}
       </motion.main>)

frontend/src/components/layout/SidebarComponent.tsx

@@ -1,14 +1,13 @@
 import { motion } from 'framer-motion'
-import { useCallback, useEffect, useRef, useState } from 'react'
 import { Helmet } from 'react-helmet-async'
 
 import { clientAnimationTransition } from '@/lib/clientAnimation'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
 import { cn } from '@/lib/utils'
 import { useUITranslation } from '@/lib/useUITranslation'
-import { useVerticalPreview } from '@/lib/useLocale'
 
 import type { CSSProperties, FC, MouseEvent, PointerEvent, ReactNode } from 'react'
+import { useCallback, useEffect, useRef, useState } from 'react'
 
 type SidebarSide = 'left' | 'right'
 
@@ -24,12 +23,12 @@ type Props = {
 
 type ResizeState = {
     pointerId:  number
-    startSize: number
+    startWidth: number
     startX:     number
-    startY:     number
-    verticalPreview: boolean
     side:       SidebarSide }
 
+type PendingPressState = ResizeState & { startY: number }
+
 const DEFAULT_SIDEBAR_WIDTH = 256
 const MIN_SIDEBAR_WIDTH = 192
 const MIN_MAIN_WIDTH = 360
@@ -38,97 +37,84 @@ const LONG_PRESS_DELAY_MS = 350
 const TOUCH_MOVE_THRESHOLD_PX = 8
 
 
-const storageKeyForSidebar = (
-    sidebarKey: string,
-    side: SidebarSide,
-    verticalPreview = false,
-): string =>
-    `sidebar:${ sidebarKey }:${ side }:${ verticalPreview ? 'height' : 'width' }`
+const storageKeyForSidebar = (sidebarKey: string, side: SidebarSide): string =>
+    `sidebar:${ sidebarKey }:${ side }:width`
 
 
-const getSidebarMaxWidth = (containerSize: number): number => {
+const getSidebarMaxWidth = (containerWidth: number): number => {
   const viewportWidth =
-      typeof window === 'undefined' ? containerSize : window.innerWidth
+      typeof window === 'undefined' ? containerWidth : window.innerWidth
   const viewportMaxWidth = Math.floor (viewportWidth * MAX_VIEWPORT_WIDTH_RATIO)
-  const containerMaxWidth = Math.floor (containerSize - MIN_MAIN_WIDTH)
+  const containerMaxWidth = Math.floor (containerWidth - MIN_MAIN_WIDTH)
   const dynamicMaxWidth = Math.min (viewportMaxWidth, containerMaxWidth)
 
   return Math.max (MIN_SIDEBAR_WIDTH, dynamicMaxWidth)
 }
 
 
-const readStoredSidebarSize = (
+const readStoredSidebarWidth = (
     sidebarKey: string,
-    side: SidebarSide,
-    verticalPreview: boolean,
-): number => {
+    side: SidebarSide): number => {
   if (typeof window === 'undefined')
     return DEFAULT_SIDEBAR_WIDTH
 
-  try
-  {
-    const value = window.localStorage.getItem (
-	storageKeyForSidebar (sidebarKey, side, verticalPreview))
-    const size = value == null ? Number.NaN : Number (value)
-    return Number.isFinite (size) ? size : DEFAULT_SIDEBAR_WIDTH
-  }
-  catch
-  {
-    return DEFAULT_SIDEBAR_WIDTH
-  }
+  const value = window.localStorage.getItem (storageKeyForSidebar (sidebarKey, side))
+  const width = value == null ? Number.NaN : Number (value)
+
+  return Number.isFinite (width) ? width : DEFAULT_SIDEBAR_WIDTH
 }
 
 
-const SidebarComponent: FC<Props> = (
-    { children, className, maxWidth, maxWidthRatio, animateLayout = true,
-      onWidthChange, sidebarKey, side = 'left' },
-) => {
+const SidebarComponent: FC<Props> = ({
+    children,
+    className,
+    maxWidth,
+    maxWidthRatio,
+    animateLayout = true,
+    onWidthChange,
+    sidebarKey,
+    side = 'left',
+}) => {
   const { message } = useUITranslation ('shared')
   const behaviourSettings = useClientBehaviourSettings ()
-  const verticalPreview = useVerticalPreview ()
   const animationMode = behaviourSettings.animation ?? 'normal'
   const layoutTransition = clientAnimationTransition (
       animationMode,
-      { normal: { duration: .2, ease: 'easeOut' as const } })
+      { normal: { duration: .2, ease: 'easeOut' as const } },
+  )
   const rootRef = useRef<HTMLDivElement | null> (null)
   const maxWidthRef = useRef (maxWidth)
   const maxWidthRatioRef = useRef (maxWidthRatio)
-  const getContainerSize = useCallback (() => {
-    const container = rootRef.current?.closest ('[data-sidebar-container]')
-    return verticalPreview
-	? container?.clientHeight ?? window.innerHeight
-	: container?.clientWidth ?? window.innerWidth
-  }, [verticalPreview])
-  const getClampedSize = useCallback ((
-      nextSize: number,
-      containerSize: number,
-  ): number => {
-    if (verticalPreview)
-    {
-      const maximum = Math.max (64, Math.min (
-	  window.innerHeight * .6, containerSize - 160))
-      return Math.min (maximum, Math.max (64, nextSize))
-    }
+  const getContainerWidth = useCallback (() => {
+    const containerWidth = rootRef.current
+	?.closest ('[data-sidebar-container]')
+	?.clientWidth
+    ?? window.innerWidth
+    return containerWidth
+  }, [])
+  const getClampedWidth = useCallback ((
+      nextWidth: number,
+      containerWidth: number): number => {
     const viewportWidth =
-	typeof window === 'undefined' ? containerSize : window.innerWidth
+	typeof window === 'undefined' ? containerWidth : window.innerWidth
     const viewportMaxWidth = Math.floor (viewportWidth * MAX_VIEWPORT_WIDTH_RATIO)
     const ratioMaxWidth = maxWidthRatioRef.current == null
-	? Infinity : Math.floor (containerSize * maxWidthRatioRef.current)
+	? Infinity : Math.floor (containerWidth * maxWidthRatioRef.current)
     const configuredMaxWidth = maxWidthRef.current == null
-	? getSidebarMaxWidth (containerSize)
+	? getSidebarMaxWidth (containerWidth)
 	: Math.max (MIN_SIDEBAR_WIDTH,
 	    Math.min (viewportMaxWidth, maxWidthRef.current))
     const maxAllowedWidth = Math.max (MIN_SIDEBAR_WIDTH,
 	Math.min (ratioMaxWidth, configuredMaxWidth))
 
-    return Math.min (maxAllowedWidth, Math.max (MIN_SIDEBAR_WIDTH, nextSize))
-  }, [verticalPreview])
+    return Math.min (maxAllowedWidth, Math.max (MIN_SIDEBAR_WIDTH, nextWidth))
+  }, [])
 
-  const [size, setSize] = useState (DEFAULT_SIDEBAR_WIDTH)
+  const [width, setWidth] = useState (DEFAULT_SIDEBAR_WIDTH)
   const [resizing, setResizing] = useState (false)
-  const sizeRef = useRef (size)
+  const widthRef = useRef (width)
   const longPressTimerRef = useRef<ReturnType<typeof setTimeout> | null> (null)
-  const pendingPressRef = useRef<ResizeState | null> (null)
+  const pendingPressRef = useRef<PendingPressState | null> (null)
   const resizeRef = useRef<ResizeState | null> (null)
   const bodyStyleRef = useRef<{ cursor: string, userSelect: string } | null> (null)
 
@@ -162,7 +148,7 @@ const SidebarComponent: FC<Props> = (
 	  userSelect: document.body.style.userSelect }
     }
 
-    document.body.style.cursor = state.verticalPreview ? 'row-resize' : 'col-resize'
+    document.body.style.cursor = 'col-resize'
     document.body.style.userSelect = 'none'
   }, [clearLongPressTimer])
 
@@ -173,50 +159,43 @@ const SidebarComponent: FC<Props> = (
     const state = resizeRef.current
     resizeRef.current = null
 
-    try
-    {
-      if (state != null)
-	window.localStorage.setItem (
-	    storageKeyForSidebar (sidebarKey, state.side, state.verticalPreview),
-	    String (sizeRef.current))
-    }
-    catch
-    {
-      // Resizing remains usable when browser storage is unavailable.
-    }
+    if (state != null)
+      window.localStorage.setItem (
+	  storageKeyForSidebar (sidebarKey, state.side),
+	  String (widthRef.current))
 
     setResizing (false)
     restoreBodyStyle ()
   }, [clearLongPressTimer, restoreBodyStyle, sidebarKey])
 
-  const applySize = useCallback ((nextSize: number) => {
-    if (nextSize === sizeRef.current)
+  const applyWidth = useCallback ((nextWidth: number) => {
+    if (nextWidth === widthRef.current)
       return
 
-    sizeRef.current = nextSize
-    setSize (nextSize)
+    widthRef.current = nextWidth
+    setWidth (nextWidth)
   }, [])
 
   useEffect (() => {
     maxWidthRef.current = maxWidth
     maxWidthRatioRef.current = maxWidthRatio
-    const containerSize = getContainerSize ()
-    const nextSize = getClampedSize (sizeRef.current, containerSize)
-    applySize (nextSize)
-  }, [applySize, getClampedSize, getContainerSize, maxWidth, maxWidthRatio])
+    const containerWidth = getContainerWidth ()
+    const nextWidth = getClampedWidth (widthRef.current, containerWidth)
+    applyWidth (nextWidth)
+  }, [applyWidth, getClampedWidth, getContainerWidth, maxWidth, maxWidthRatio])
 
-  const updateSize = useCallback ((clientX: number, clientY: number) => {
+  const updateWidth = useCallback ((clientX: number) => {
     const state = resizeRef.current
     if (state == null)
       return
 
-    const containerSize = getContainerSize ()
-    const delta = state.verticalPreview
-	? clientY - state.startY
-	: (state.side === 'left' ? clientX - state.startX : state.startX - clientX)
-    const nextSize = getClampedSize (state.startSize + delta, containerSize)
-    applySize (nextSize)
-  }, [applySize, getClampedSize, getContainerSize])
+    const containerWidth = getContainerWidth ()
+    const delta = state.side === 'left'
+		  ? clientX - state.startX
+		  : state.startX - clientX
+    const nextWidth = getClampedWidth (state.startWidth + delta, containerWidth)
+    applyWidth (nextWidth)
+  }, [applyWidth, getClampedWidth, getContainerWidth])
 
   const handlePointerDown = (ev: PointerEvent<HTMLDivElement>) => {
     if (ev.pointerType !== 'mouse' && ev.pointerType !== 'touch')
@@ -232,10 +211,8 @@ const SidebarComponent: FC<Props> = (
     const state = {
 	pointerId: ev.pointerId,
 	side,
-	startSize: sizeRef.current,
-	startX: ev.clientX,
-	startY: ev.clientY,
-	verticalPreview }
+	startWidth: widthRef.current,
+	startX: ev.clientX }
 
     if (ev.pointerType === 'mouse')
     {
@@ -243,7 +220,7 @@ const SidebarComponent: FC<Props> = (
       return
     }
 
-    pendingPressRef.current = state
+    pendingPressRef.current = { ...state, startY: ev.clientY }
     clearLongPressTimer ()
     longPressTimerRef.current = setTimeout (() => {
       if (pendingPressRef.current != null)
@@ -257,7 +234,7 @@ const SidebarComponent: FC<Props> = (
     if (resizeRef.current != null)
     {
       ev.preventDefault ()
-      updateSize (ev.clientX, ev.clientY)
+      updateWidth (ev.clientX)
       return
     }
 
@@ -285,58 +262,58 @@ const SidebarComponent: FC<Props> = (
     finishResize ()
   }
 
-  const resetSize = useCallback (() => {
-    const containerSize = getContainerSize ()
-    const nextSize = getClampedSize (DEFAULT_SIDEBAR_WIDTH, containerSize)
-    applySize (nextSize)
-    window.localStorage.removeItem (
-	storageKeyForSidebar (sidebarKey, side, verticalPreview))
-  }, [applySize, getClampedSize, getContainerSize, sidebarKey, side, verticalPreview])
+  const resetWidth = useCallback (() => {
+    const containerWidth = getContainerWidth ()
+    const nextWidth = getClampedWidth (DEFAULT_SIDEBAR_WIDTH, containerWidth)
+    applyWidth (nextWidth)
+    window.localStorage.removeItem (storageKeyForSidebar (sidebarKey, side))
+  }, [applyWidth, getClampedWidth, getContainerWidth, sidebarKey, side])
 
   const handleDoubleClick = (ev: MouseEvent<HTMLDivElement>) => {
     ev.preventDefault ()
     ev.stopPropagation ()
-    resetSize ()
+    resetWidth ()
   }
 
   useEffect (() => {
-    const containerSize = getContainerSize ()
-    const nextSize = getClampedSize (
-	readStoredSidebarSize (sidebarKey, side, verticalPreview),
-	containerSize)
-    applySize (nextSize)
-  }, [applySize, getClampedSize, getContainerSize, sidebarKey, side, verticalPreview])
+    const containerWidth = getContainerWidth ()
+    const nextWidth = getClampedWidth (
+	readStoredSidebarWidth (sidebarKey, side),
+	containerWidth)
+    applyWidth (nextWidth)
+  }, [applyWidth, getClampedWidth, getContainerWidth, sidebarKey, side])
 
   useEffect (() => {
-    const containerSize = getContainerSize ()
-    const nextSize = getClampedSize (sizeRef.current, containerSize)
-    applySize (nextSize)
-  }, [applySize, getClampedSize, getContainerSize])
+    const containerWidth = getContainerWidth ()
+    const nextWidth = getClampedWidth (widthRef.current, containerWidth)
+    applyWidth (nextWidth)
+  }, [applyWidth, getClampedWidth, getContainerWidth])
 
   useEffect (() => {
     if (typeof window === 'undefined')
       return
 
     const handleResize = () => {
-      const containerSize = getContainerSize ()
-      const nextSize = getClampedSize (sizeRef.current, containerSize)
-      applySize (nextSize)
+      const containerWidth = getContainerWidth ()
+      const nextWidth = getClampedWidth (widthRef.current, containerWidth)
+      applyWidth (nextWidth)
     }
 
     window.addEventListener ('resize', handleResize)
     return () => window.removeEventListener ('resize', handleResize)
-  }, [applySize, getClampedSize, getContainerSize])
+  }, [applyWidth, getClampedWidth, getContainerWidth])
 
   useEffect (() => {
-    if (!verticalPreview)
-      onWidthChange?.(size)
-  }, [onWidthChange, size, verticalPreview])
+    onWidthChange?.(width)
+  }, [onWidthChange, width])
 
-  useEffect (() => () => finishResize (), [finishResize, verticalPreview])
+  useEffect (() => () => {
+    clearLongPressTimer ()
+    restoreBodyStyle ()
+  }, [clearLongPressTimer, restoreBodyStyle])
 
   const style = {
-      '--sidebar-width': `${ size }px`,
-      '--sidebar-height': `${ size }px` } as CSSProperties
+      '--sidebar-width': `${ width }px` } as CSSProperties
 
   return (
       <motion.div
@@ -345,7 +322,7 @@ const SidebarComponent: FC<Props> = (
 	  transition={{ layout: layoutTransition }}
 	  style={style}
 	  className={cn (
-	      'sidebar-panel relative w-full md:w-[var(--sidebar-width)] md:shrink-0 md:h-full',
+	      'relative w-full md:w-[var(--sidebar-width)] md:shrink-0 md:h-full',
 	      className)}>
 	<Helmet>
 	  <style>
@@ -368,16 +345,16 @@ const SidebarComponent: FC<Props> = (
 
 	<div
 	    role="separator"
-	    aria-orientation={verticalPreview ? 'horizontal' : 'vertical'}
-	    aria-label={message (verticalPreview ? 'labels.menu' : 'sidebarWidth').text}
-	    lang={message (verticalPreview ? 'labels.menu' : 'sidebarWidth').language}
+	    aria-orientation="vertical"
+	    aria-label={message ('sidebarWidth').text}
+	    lang={message ('sidebarWidth').language}
 	    onPointerDown={handlePointerDown}
 	    onPointerMove={handlePointerMove}
 	    onPointerUp={handlePointerEnd}
 	    onPointerCancel={handlePointerEnd}
 	    onDoubleClick={handleDoubleClick}
 	    className={cn (
-		'sidebar-resize hidden md:block absolute top-0 bottom-0 z-20 w-4 cursor-col-resize',
+		'hidden md:block absolute top-0 bottom-0 z-20 w-4 cursor-col-resize',
 		'touch-none select-none',
 		side === 'left' ? '-right-2' : '-left-2',
 		'before:absolute before:top-0 before:bottom-0 before:w-px',

frontend/src/entry-server.tsx

@@ -9,8 +9,7 @@ import { createStaticHandler, createStaticRouter,
 import { AppFrame, appRoutes, resolvePageRoute } from '@/App'
 import { apiGet, isApiError } from '@/lib/api'
 import { createUII18n } from '@/lib/i18n'
-import { fetchLocales, isLocaleCode, isVerticalPreviewPath,
-	 legacyLocalePath } from '@/lib/locales'
+import { fetchLocales, isLocaleCode, legacyLocalePath } from '@/lib/locales'
 import { localesKeys, sessionKeys } from '@/lib/queryKeys'
 import { withRenderContext } from '@/lib/renderContext.server'
 
@@ -73,15 +72,13 @@ export const render = async (
       pathname => resolvePageRoute (pathname) != null)
   const pathname = legacy == null ? url.pathname : new URL (legacy, origin).pathname
   const segment = pathname.split ('/')[1]
-  const verticalPreview = isVerticalPreviewPath (pathname)
   const known = resolvePageRoute (pathname)
   if (legacy != null && known != null)
     return { status: 308, location: legacy }
   const locale = isLocaleCode (segment) ? segment : 'ja'
-  const routePrefix = verticalPreview ? 'mn-Mong' : locale
   if (known?.route.handle?.redirectTo != null)
     return { status: 308,
-      location: `/${routePrefix}${known.route.handle.redirectTo}${url.search}` }
+      location: `/${locale}${known.route.handle.redirectTo}${url.search}` }
   const requestContext: RenderContext & { status: number } = {
       pathname: url.pathname, origin, apiBaseURL,
       ...authentication, status: 200 }
@@ -109,8 +106,7 @@ export const render = async (
 	}
       }
       const prepare = known?.route.handle?.prepare
-      const routeLocaleValid = isLocaleCode (segment) || verticalPreview
-      let status = known == null || !active || !routeLocaleValid ? 404 : 200
+      let status = known == null || !active || !isLocaleCode (segment) ? 404 : 200
       if (status === 200 && known?.route.handle?.authentication != null
 	  && client.getQueryData (sessionKeys.current) == null)
 	status = 401

frontend/src/index.css

@@ -625,503 +625,3 @@ body
   white-space: nowrap;
   will-change: transform;
 }
-
-/* Loaded only by the development-only sample, with the OFL alongside the font. */
-@font-face
-{
-  font-family: 'BTRC Mongolian Preview';
-  src: url('/fonts/noto-sans-mongolian/NotoSansMongolian-Regular.ttf') format('truetype');
-  font-weight: 400;
-  font-style: normal;
-  font-display: swap;
-}
-
-/* Development-only /mn-Mong layout. Unannotated pages retain horizontal text. */
-[data-vertical-preview]
-{
-  min-width: 0;
-  min-height: 0;
-  overflow: hidden;
-}
-
-[data-vertical-preview] > :not(.top-nav-layout)
-{
-  flex: 1;
-  min-width: 0;
-  min-height: 0;
-  overflow: auto;
-}
-
-[data-vertical-preview] [data-sidebar-container]
-{
-  display: flex;
-  flex-direction: column;
-  min-width: 0;
-  min-height: 0;
-  overflow: hidden;
-}
-
-[data-vertical-preview] .main-area
-{
-  min-width: 0;
-  min-height: 0;
-  overscroll-behavior: contain;
-}
-
-[data-vertical-preview] .main-area[data-vertical-content]
-{
-  overflow-x: auto;
-  overflow-y: hidden;
-  overscroll-behavior-x: contain;
-}
-
-[data-vertical-preview] .sidebar-panel
-{
-  width: 100%;
-  height: var(--sidebar-height);
-  min-height: 0;
-  flex: none;
-}
-
-[data-vertical-preview] .sidebar
-{
-  display: flex;
-  align-items: flex-start;
-  gap: 1rem;
-  direction: ltr;
-  overflow-x: auto;
-  overflow-y: hidden;
-  overscroll-behavior: contain;
-}
-
-[data-vertical-preview] .sidebar > *
-{
-  flex-shrink: 0;
-}
-
-[data-vertical-preview] .sidebar > form
-{
-  width: 16rem;
-  height: 100%;
-  overflow-y: auto;
-}
-
-[data-vertical-preview] .sidebar > form > ul
-{
-  position: relative;
-}
-
-[data-vertical-preview] .sidebar > div
-{
-  writing-mode: vertical-lr;
-  text-orientation: mixed;
-  height: 100%;
-  margin: 0;
-}
-
-[data-vertical-preview] .sidebar :is(h2, h3, ul)
-{
-  margin: 0;
-  margin-block-end: 1rem;
-}
-
-[data-vertical-preview] .sidebar-resize
-{
-  display: block;
-  inset: auto 0 -.5rem;
-  width: 100%;
-  height: 1rem;
-  cursor: row-resize;
-}
-
-[data-vertical-preview] .sidebar-resize::before
-{
-  inset: 50% 0 auto;
-  width: 100%;
-  height: 1px;
-}
-
-[data-vertical-preview] .vertical-preview-sample
-{
-  writing-mode: vertical-lr;
-  text-orientation: mixed;
-  font-family: 'BTRC Mongolian Preview', 'Mongolian Baiti', sans-serif;
-  font-size: 1.25rem;
-  line-height: 1.5;
-  flex-shrink: 0;
-}
-
-/* The post grid fills each column downwards before continuing to the right. */
-[data-vertical-preview] .posts-main-area > div
-{
-  display: flex;
-  height: 100%;
-  width: max-content;
-  margin: 0;
-  gap: 1rem;
-}
-
-[data-vertical-preview] .posts-main-area > div > div:first-child
-{
-  flex-direction: column;
-  justify-content: flex-start;
-  writing-mode: vertical-lr;
-  text-orientation: mixed;
-}
-
-[data-vertical-preview] .posts-main-area > div > div:last-child
-{
-  display: flex;
-  width: max-content;
-  height: 100%;
-  margin: 0;
-  gap: 1rem;
-}
-
-[data-vertical-preview] .main-area[data-vertical-content] .post-list
-{
-  display: grid;
-  grid-auto-flow: column;
-  grid-auto-columns: 10rem;
-  grid-template-rows: repeat(auto-fill, min(10rem, 100%));
-  flex: none;
-  width: max-content;
-  height: 100%;
-  writing-mode: horizontal-tb;
-}
-
-[data-vertical-preview] .main-area[data-vertical-content] .post-list > a
-{
-  height: 100%;
-}
-
-[data-vertical-preview] .main-area[data-vertical-content] nav
-{
-  flex: none;
-  align-self: flex-start;
-  margin: 0;
-  writing-mode: horizontal-tb;
-}
-
-[data-vertical-preview] .tags-main-area
-{
-  display: flex;
-  align-items: stretch;
-  gap: 1.5rem;
-}
-
-[data-vertical-preview] .tag-list-filter
-{
-  flex: none;
-  width: min(24rem, 75vw);
-  max-width: none;
-  overflow-y: auto;
-}
-
-[data-vertical-preview] .tag-list-filter h1
-{
-  writing-mode: vertical-lr;
-  text-orientation: mixed;
-  max-height: 8rem;
-  margin-block: 0;
-}
-
-[data-vertical-preview] .tag-list-filter input[type='number']
-{
-  max-width: 7rem;
-}
-
-[data-vertical-preview] .tag-list-results
-{
-  display: flex;
-  flex: none;
-  gap: 1rem;
-  max-width: none;
-  margin: 0;
-}
-
-[data-vertical-preview] .tag-list-table
-{
-  max-width: none;
-  overflow-x: visible;
-  overflow-y: auto;
-}
-
-[data-vertical-preview] .tag-list-table table
-{
-  writing-mode: vertical-lr;
-  text-orientation: mixed;
-  inline-size: max-content;
-  block-size: max-content;
-  min-width: 0;
-}
-
-[data-vertical-preview] .tag-list-table col
-{
-  width: auto;
-}
-
-[data-vertical-preview] .tag-list-table :is(th, td)
-{
-  min-inline-size: 2rem;
-  max-inline-size: 16rem;
-  text-align: start;
-}
-
-[data-vertical-preview] .tag-list-table thead
-{
-  border-bottom: 0;
-  border-block-end: 2px solid currentColor;
-}
-
-[data-vertical-preview] .tag-list-table td:nth-child(2),
-[data-vertical-preview] .tag-list-table time
-{
-  writing-mode: horizontal-tb;
-  white-space: nowrap;
-}
-
-[data-vertical-preview] :is(.sidebar, .tag-list-table, .wiki-main-area) .tag-marquee,
-[data-vertical-preview] :is(.sidebar, .tag-list-table, .wiki-main-area) .tag-marquee__static
-{
-  white-space: normal;
-  overflow: visible;
-  text-overflow: clip;
-  max-inline-size: 16rem;
-  opacity: 1;
-}
-
-[data-vertical-preview] :is(.sidebar, .tag-list-table, .wiki-main-area) .tag-marquee__animated
-{
-  display: none;
-}
-
-/* Prose flows through the viewport height and grows into columns on the right. */
-[data-vertical-preview] .wiki-main-area
-{
-  display: flex;
-  gap: 1rem;
-}
-
-[data-vertical-preview] .wiki-main-area > div
-{
-  flex: none;
-  writing-mode: vertical-lr;
-  text-orientation: mixed;
-  margin: 0;
-}
-
-[data-vertical-preview] .wiki-main-area > div > span
-{
-  writing-mode: horizontal-tb;
-}
-
-[data-vertical-preview] .wiki-main-area article,
-[data-vertical-preview] .posts-main-area .localised-document
-{
-  writing-mode: vertical-lr;
-  text-orientation: mixed;
-  inline-size: 100%;
-  block-size: max-content;
-  max-width: none;
-  margin: 0;
-  flex: none;
-}
-
-[data-vertical-preview] .main-area[data-vertical-content] .localised-document
-{
-  max-width: none;
-  overflow: visible;
-}
-
-[data-vertical-preview] .wiki-main-area article :is(h1, h2, h3, h4, p, ul, ol, blockquote)
-{
-  margin: 0;
-  margin-block: 1em;
-}
-
-[data-vertical-preview] .wiki-main-area article :is(ul, ol)
-{
-  padding: 0;
-  padding-inline-start: 1.5em;
-}
-
-[data-vertical-preview] .wiki-main-area article :is(img, video, iframe, svg)
-{
-  writing-mode: horizontal-tb;
-  max-height: 100%;
-  max-width: none;
-  object-fit: contain;
-}
-
-[data-vertical-preview] .wiki-main-area article :is(pre, table, .not-prose),
-[data-vertical-preview] .main-area[data-vertical-content] :is(code, time, input, select, textarea)
-{
-  writing-mode: horizontal-tb;
-  text-orientation: mixed;
-}
-
-[data-vertical-preview] .wiki-main-area article :is(pre, table, .not-prose)
-{
-  display: inline-block;
-  max-height: 100%;
-  max-width: min(48rem, 80vw);
-  overflow: auto;
-  vertical-align: top;
-}
-
-[data-vertical-preview] .wiki-main-area article .not-prose
-{
-  width: max-content;
-  height: 100%;
-}
-
-[data-vertical-preview] .wiki-main-area .not-prose > div
-{
-  display: flex;
-  flex-direction: column;
-  height: 100%;
-  margin: 0;
-}
-
-[data-vertical-preview] .wiki-main-area .not-prose > div > div:last-child
-{
-  flex: 1;
-  min-height: 0;
-}
-
-@media (min-width: 768px)
-{
-  [data-vertical-preview].app-layout
-  {
-    flex-direction: row;
-  }
-
-  [data-vertical-preview] .top-nav-layout
-  {
-    display: flex;
-    width: max-content;
-    max-width: 50vw;
-    height: 100%;
-  }
-
-  [data-vertical-preview] .top-nav-bar
-  {
-    flex-direction: column;
-    flex: none;
-    width: 7rem;
-    height: 100%;
-    padding: .5rem;
-    gap: .5rem;
-  }
-
-  [data-vertical-preview] .top-nav-primary
-  {
-    flex-direction: column;
-    flex: 1;
-    min-height: 0;
-    width: 100%;
-    height: auto;
-    overflow-y: auto;
-  }
-
-  [data-vertical-preview] .top-nav-brand-link
-  {
-    writing-mode: vertical-lr;
-    text-orientation: mixed;
-    max-height: 9rem;
-    white-space: normal;
-    margin-block: .5rem;
-  }
-
-  [data-vertical-preview] .top-nav-desktop-menu
-  {
-    flex-direction: column;
-    width: 100%;
-    height: auto;
-  }
-
-  [data-vertical-preview] .top-nav-desktop-menu > div:not(.top-nav-highlight)
-  {
-    width: 100%;
-  }
-
-  [data-vertical-preview] .top-nav-desktop-menu .top-nav-menu-link
-  {
-    justify-content: center;
-    width: 100%;
-    min-height: 3rem;
-    height: auto;
-    padding: .5rem;
-  }
-
-  [data-vertical-preview] .top-nav-menu-link > :not(svg, select),
-  [data-vertical-preview] .top-nav-more-menu h2
-  {
-    writing-mode: vertical-lr;
-    text-orientation: mixed;
-    max-height: 9rem;
-    white-space: normal;
-  }
-
-  [data-vertical-preview] .top-nav-highlight
-  {
-    inset-inline-start: 0;
-  }
-
-  [data-vertical-preview] .top-nav-account
-  {
-    flex-direction: column;
-    width: 100%;
-    margin: 0;
-  }
-
-  [data-vertical-preview] .top-nav-account .top-nav-user-desktop
-  {
-    max-width: 100%;
-    margin: 0;
-    padding: 0;
-  }
-
-  [data-vertical-preview] .top-nav-locale-name
-  {
-    display: inline;
-    writing-mode: horizontal-tb;
-  }
-
-  [data-vertical-preview] .top-nav-desktop-submenu
-  {
-    min-width: 0;
-    height: 100%;
-  }
-
-  [data-vertical-preview] .top-nav-submenu-content
-  {
-    width: max-content;
-    max-width: 35vw;
-    height: 100%;
-    overflow-y: auto;
-    overflow-x: hidden;
-  }
-
-  [data-vertical-preview] :is(.top-nav-submenu-items, .top-nav-more-links)
-  {
-    flex-direction: column;
-    flex-wrap: nowrap;
-    align-items: stretch;
-  }
-
-  [data-vertical-preview] .top-nav-submenu-items .top-nav-menu-link
-  {
-    justify-content: center;
-  }
-}
-
-@media (max-width: 767px)
-{
-  [data-vertical-preview] .top-nav-layout
-  {
-    max-height: 50dvh;
-    overflow-y: auto;
-  }
-}

frontend/src/lib/locales.ts

@@ -28,11 +28,6 @@ export const localeFromPath = (pathname: string): LocaleCode | null => {
 }
 
 
-// A development-only layout route; API and dictionary locales stay unchanged.
-export const isVerticalPreviewPath = (pathname: string): boolean =>
-    import.meta.env.DEV && /^\/mn-Mong(?:[/?#]|$)/.test (pathname)
-
-
 export const resolveViewingLocale = (
     pathname: string,
     routeLocale?: unknown,
@@ -45,22 +40,20 @@ export const currentViewingLocale = (): LocaleCode =>
 
 
 export const unlocalisedPath = (pathname: string): string => {
-  const locale = isVerticalPreviewPath (pathname) ? 'mn-Mong' : localeFromPath (pathname)
+  const locale = localeFromPath (pathname)
   return locale == null ? pathname : pathname.slice (locale.length + 1) || '/'
 }
 
 
-export const localiseTo = (to: To, locale: LocaleCode, viewingPath = ''): To => {
+export const localiseTo = (to: To, locale: LocaleCode): To => {
   const pathname = typeof to === 'string' ? to : to.pathname
   if (pathname == null
       || !(pathname.startsWith ('/'))
       || pathname.startsWith ('//')
-      || localeFromPath (pathname) != null
-      || isVerticalPreviewPath (pathname))
+      || localeFromPath (pathname) != null)
     return to
 
-  const prefix = isVerticalPreviewPath (viewingPath) ? 'mn-Mong' : locale
-  const localised = `/${ prefix }${ pathname }`
+  const localised = `/${ locale }${ pathname }`
   return typeof to === 'string' ? localised : { ...to, pathname: localised }
 }
 
@@ -80,8 +73,7 @@ export const legacyLocalePath = (
     location: { pathname: string; search: string; hash: string },
     isPage: (pathname: string) => boolean = () => false,
 ): string | null => {
-  if (localeFromPath (location.pathname) != null
-      || isVerticalPreviewPath (location.pathname) || !isPage (location.pathname))
+  if (localeFromPath (location.pathname) != null || !isPage (location.pathname))
     return null
   return switchLocalePath (location, automaticallySelectedLocale ())
 }

frontend/src/lib/useLocale.ts

@@ -1,7 +1,7 @@
 import { useCallback } from 'react'
 import { useLocation, useNavigate, useParams } from 'react-router-dom'
 
-import { isVerticalPreviewPath, localiseTo, resolveViewingLocale } from '@/lib/locales'
+import { localiseTo, resolveViewingLocale } from '@/lib/locales'
 
 import type { NavigateFunction, NavigateOptions, To } from 'react-router-dom'
 
@@ -18,15 +18,10 @@ export const useLocale = (): LocaleCode => {
 export const useLocaleNavigate = (): NavigateFunction => {
   const navigate = useNavigate ()
   const locale = useLocale ()
-  const { pathname } = useLocation ()
   return useCallback ((to: To | number, options?: NavigateOptions) => {
     if (typeof to === 'number')
       navigate (to)
     else
-      navigate (localiseTo (to, locale, pathname), options)
-  }, [locale, navigate, pathname])
+      navigate (localiseTo (to, locale), options)
+  }, [locale, navigate])
 }
-
-
-export const useVerticalPreview = (): boolean =>
-    isVerticalPreviewPath (useLocation ().pathname)

frontend/src/pages/posts/PostListPage.tsx

@@ -146,7 +146,7 @@ const PostListPage: FC = () => {
 				    JSON.stringify (statesToSave))
 	}}/>
 
-	<MainArea className="posts-main-area" verticalContent>
+	<MainArea>
 	  <TabGroup
 	      rightAddon={
 		  <label className="flex items-center gap-2 text-xs text-muted-foreground">

frontend/src/pages/tags/TagListPage.tsx

@@ -220,10 +220,10 @@ const TagListPage: FC = () => {
   }), [page, totalPages, location.search]))
 
   return (
-      <MainArea className="tags-main-area min-w-0" verticalContent>
+      <MainArea className="min-w-0">
 	<PageHead title={message ('title')}/>
 
-	<div className="tag-list-filter max-w-xl">
+	<div className="max-w-xl">
 	  <div className="flex flex-wrap items-center justify-between gap-3">
 	    <PageTitle>{label ('title')}</PageTitle>
 	    <label className="flex items-center gap-2 text-xs text-muted-foreground">
@@ -358,8 +358,8 @@ const TagListPage: FC = () => {
 
 	{isError && <p role="alert">{label ('common:fetchError')}</p>}
 	{loading ? label ('common:loading') : (results.length > 0 ? (
-	    <div className="tag-list-results mt-4 min-w-0 max-w-full">
-	      <div className="tag-list-table min-w-0 max-w-full overflow-x-auto">
+	    <div className="mt-4 min-w-0 max-w-full">
+	      <div className="min-w-0 max-w-full overflow-x-auto">
 		<table className="w-full min-w-[2000px] table-auto border-collapse">
 		  <colgroup>
 		    <col className="w-72"/>

frontend/src/pages/wiki/WikiDetailPage.tsx

@@ -114,7 +114,7 @@ const WikiDetailPage: FC = () => {
     return <NotFound/>
 
   return (
-      <MainArea className="wiki-main-area" verticalContent>
+      <MainArea>
 	<PageHead title={{
 	    text: `${displayTitle}${deprecated
 		? message ('labels.deprecatedSuffix').text : ''} Wiki`,