WIP: address PR #475 review feedback

backend/app/services/counts_candidates.rb

@@ -6,14 +6,8 @@ class CountsCandidates
 
   def initialize(params)
     QueryState.validate!(params, KEYS)
-    definition = CountsResourceDefinition.new(params.fetch('resource'))
+    raise ArgumentError unless params.fetch('resource') == 'posts'
-    fields = ['resource_id', 'user']
+    raise ArgumentError unless ['tags', 'tags_json'].include?(params.fetch('field'))
-    fields += ['tags', 'tags_json', 'tags.id'] if definition.resource == 'posts'
-    fields << 'members' if definition.resource == 'tag_groups'
-    if definition.resource == 'materials'
-      fields += ['updated_by_user_id', 'file_blob_id', 'source_file_id', 'drive_file_id']
-    end
-    raise ArgumentError unless fields.include?(params.fetch('field'))
 
     @params = params
     @page = Integer(params.fetch('page', '1'), 10)
@@ -24,27 +18,25 @@ class CountsCandidates
   end
 
   def call
-    references = ['tags', 'tags_json', 'tags.id', 'members']
-    return resource_candidates unless references.include?(@params['field'])
-
     options = @params.slice('locale', 'at', 'execution_at', 'timezone')
         .merge('definition' => 'latest', 'resource' => 'tags')
     internal = CountsPopulation.new(options)
-    groups_flg = @params['field'] == 'members'
+    external = CountsPopulation.new(options.merge('resource' => 'nico_tags',
-    external = CountsPopulation.new(options.merge(
-        'resource' => groups_flg ? 'tag_groups' : 'nico_tags',
         'execution_at' => internal.at.iso8601(6)))
     connection = TagVersion.connection
     sources = [[internal, 'internal', 'v.category', 'v.names'],
-        [external, groups_flg ? 'group' : 'external', 'NULL', 'JSON_OBJECT()']]
+               [external, 'external', 'NULL', 'JSON_OBJECT()']]
     sources = sources.map do |population, kind, category, names|
       scope = population.scope.except(:select)
-      identity = "v.#{ population.definition.keys.first }"
+      if @params['query'].present?
-      scope = search(scope, identity, 'v.name', names)
+        pattern = "%#{ ApplicationRecord.sanitize_sql_like(@params['query']) }%"
-      value = ['tags.id', 'members'].include?(@params['field']) ?
+        scope = scope.where("(v.name LIKE ? OR CAST(v.tag_id AS CHAR) = ? OR EXISTS (" +
-          "CAST(#{ identity } AS CHAR)" : "CONCAT('#{ kind }:', #{ identity })"
+            "SELECT 1 FROM JSON_TABLE(COALESCE(JSON_EXTRACT(#{ names }, '$**.name'), " +
+            "JSON_ARRAY()), '$[*]' COLUMNS (name TEXT PATH '$')) candidate_name " +
+            'WHERE candidate_name.name LIKE ?))', pattern, @params['query'], pattern)
+      end
       scope.select(Arel.sql(
-          "#{ value } AS value, #{ identity } AS id, " +
+          "CONCAT('#{ kind }:', v.tag_id) AS value, v.tag_id AS id, " +
           "v.name AS name, #{ names } AS names, #{ category } AS category, '#{ kind }' AS kind"))
           .to_sql
     end
@@ -63,63 +55,4 @@ class CountsCandidates
     { rows: rows.first(LIMIT), page: @page, more: rows.length > LIMIT,
       execution_at: internal.at.iso8601(6) }
   end
-
-  private
-
-  def search(scope, identity, name, names)
-    return scope if @params['query'].blank?
-
-    pattern = "%#{ ApplicationRecord.sanitize_sql_like(@params['query']) }%"
-    scope.where("(#{ name } LIKE ? OR CAST(#{ identity } AS CHAR) = ? OR EXISTS (" +
-        "SELECT 1 FROM JSON_TABLE(COALESCE(JSON_EXTRACT(#{ names }, '$**.name'), " +
-        "JSON_ARRAY()), '$[*]' COLUMNS (name TEXT PATH '$')) candidate_name " +
-        'WHERE candidate_name.name LIKE ?))', pattern, @params['query'], pattern)
-  end
-
-  def resource_candidates
-    options = @params.slice('at', 'execution_at', 'timezone')
-        .merge('resource' => @params.fetch('resource'), 'definition' => 'latest')
-    actor_flg = ['user', 'updated_by_user_id'].include?(@params['field'])
-    options['definition'] = 'history' if actor_flg
-    population = CountsPopulation.new(options)
-    scope = population.scope.except(:select)
-    if actor_flg
-      point = population.timestamp(@params['at']) || population.at
-      raise ArgumentError if point > population.at
-
-      column = @params['field'] == 'user' ? 'created_by_user_id' : 'updated_by_user_id'
-      identities = scope.where('v.created_at <= ?', point).select("v.#{ column }")
-      scope = User.where(id: identities)
-      identity = 'users.id'
-      name = 'users.name'
-      names = 'JSON_OBJECT()'
-    else
-      definition = population.definition
-      column = @params['field'] == 'resource_id' ? definition.keys.first : @params['field']
-      if column == 'drive_file_id'
-        column = 'source_file_id'
-        scope = scope.where('v.source_kind' => 'google_drive_file')
-      end
-      identity = "v.#{ column }"
-      label = ['title', 'name', 'url'].find { definition.fields.key?(_1) }
-      name = label ? "v.#{ label }" : 'NULL'
-      names = definition.resource == 'tags' ? 'v.names' : 'JSON_OBJECT()'
-      if ['file_blob_id', 'source_file_id', 'drive_file_id'].include?(@params['field'])
-        scope = scope.where.not("v.#{ column }" => nil).group(Arel.sql(identity))
-        name = 'v.file_filename'
-      end
-    end
-    scope = search(scope, identity, name, names)
-    title = ['file_blob_id', 'source_file_id', 'drive_file_id'].include?(@params['field']) ?
-        "MIN(#{ name })" : name
-    query = scope.optimizer_hints('MAX_EXECUTION_TIME(10000)').distinct
-        .select(Arel.sql("#{ identity } AS id, #{ title } AS name, #{ names } AS names"))
-        .order(Arel.sql(identity)).limit(LIMIT + 1).offset((@page - 1) * LIMIT)
-    rows = scope.klass.connection.select_all(query.to_sql).to_a.map do |values|
-      values['names'] = JSON.parse(values['names']) if values['names'].is_a?(String)
-      values.merge('value' => values.fetch('id').to_s)
-    end
-    { rows: rows.first(LIMIT), page: @page, more: rows.length > LIMIT,
-      execution_at: population.at.iso8601(6) }
-  end
 end

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

@@ -0,0 +1,94 @@
+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

@@ -0,0 +1,11 @@
+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 by the Mongolian UI at `/mn-Mong`.
+The font and license are served together from this directory.

frontend/scripts/help-assets.test.ts

@@ -1,9 +1,10 @@
 import { mkdir, mkdtemp, rm, writeFile } from 'node:fs/promises'
 import { tmpdir } from 'node:os'
 import path from 'node:path'
+import { createServer } from 'vite'
 import { afterAll, afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
-import { generateHelpAssets } from './help-assets'
+import { generateHelpAssets, helpAssets } from './help-assets'
 
 import type { ArticleMeta, HelpChange, HelpSearchEntry, HelpTitleIndex } from '@/lib/help'
 
@@ -109,4 +110,22 @@ describe ('Build-time Help assets', () => {
   it ('rejects an empty Help checkout', async () => {
     await expect (generateHelpAssets (root)).rejects.toThrow ('No Help articles found')
   })
+
+  it ('defers missing Help errors until a Help module is requested', async () => {
+    const server = await createServer ({
+	configFile: false,
+	root,
+	plugins: [helpAssets ()],
+	server: { middlewareMode: true, watch: null } })
+    try
+    {
+      await server.pluginContainer.buildStart ({})
+      await expect (server.pluginContainer.load ('\0virtual:help/articles'))
+	  .rejects.toThrow ('ENOENT')
+    }
+    finally
+    {
+      await server.close ()
+    }
+  })
 })

frontend/scripts/help-assets.ts

@@ -159,10 +159,9 @@ export const helpAssets = (): Plugin => {
       configResolved (config) {
 	state.root = path.resolve (config.root, 'help')
       },
-      async buildStart () {
+      buildStart () {
-	state.data = generateHelpAssets (state.root)
+	state.data = undefined
-	const generated = await data ()
+	this.addWatchFile (state.root)
-	generated.files.forEach (file => this.addWatchFile (file))
       },
       resolveId (id) {
 	return id.startsWith (prefix) ? `\0${ id }` : null
@@ -170,7 +169,9 @@ export const helpAssets = (): Plugin => {
       async load (id) {
 	if (!(id.startsWith (`\0${ prefix }`)))
 	  return null
-	const source = (await data ()).modules.get (id.slice (1))
+	const generated = await data ()
+	generated.files.forEach (file => this.addWatchFile (file))
+	const source = generated.modules.get (id.slice (1))
 	if (source == null)
 	  throw new Error (`Unknown Help asset: ${ id.slice (1) }`)
 	return source

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, legacyLocalePath,
+import { fetchLocales, isLocaleCode, isVerticalPreviewPath, legacyLocalePath,
-	 switchLocalePath, unlocalisedPath } from '@/lib/locales'
+	 localiseTo, 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 } from '@/lib/useLocale'
+import { useLocale, useUILocale, useVerticalPreview } from '@/lib/useLocale'
 import { applyClientAnimationMode,
 	 applyClientAppearance,
 	 fetchUserThemeSlots,
@@ -46,7 +46,7 @@ import ServiceUnavailable from '@/pages/ServiceUnavailable'
 import type { ComponentType, Dispatch, FC, ReactNode, SetStateAction } from 'react'
 import type { RouteMatch } from 'react-router-dom'
 
-import type { AvailableLocale, LocaleCode } from '@/lib/locales'
+import type { AvailableLocale, LocaleCode, UILocaleCode } from '@/lib/locales'
 import type { PageRoute } from '@/lib/routeLocales'
 import type { User } from '@/types'
 
@@ -267,15 +267,21 @@ 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)
   const countsPage = pagePath === '/counts' || pagePath.startsWith ('/counts/')
-  const switchLocale = async (targetLocale: LocaleCode): Promise<string> => {
+  const switchLocale = async (target: UILocaleCode): Promise<string> => {
+    const targetLocale = target === 'mn-Mong' ? 'ja' : target
+    if (targetLocale === locale)
+      return switchLocalePath (location, target)
     const resolve = route?.route.handle?.switchLocale
-    return (resolve != null && route != null)
+    const destination =
-	? resolve ({ location, params: route.params, locale, targetLocale })
+	(resolve != null && route != null)
+	? await resolve ({ location, params: route.params, locale, targetLocale })
 	: switchLocalePath (location, targetLocale)
+    return target === 'mn-Mong' ? `/mn-Mong${unlocalisedPath (destination)}` : destination
   }
   const [user, setUserState] = useState<User | null> (
       () => client.getQueryData<User> (sessionKeys.current) ?? null)
@@ -393,7 +399,8 @@ const RoutedApp = ({ locales }: { locales: AvailableLocale[] }) => {
 	      <motion.div
 		  layout={(animationMode === 'off' || countsPage) ? false : 'position'}
 		  transition={{ layout: appLayoutTransition }}
-		  className="relative flex h-dvh w-full flex-col overflow-y-hidden">
+		  data-vertical-preview={verticalPreview || undefined}
+		  className="app-layout relative flex h-dvh w-full flex-col overflow-y-hidden">
 		<TopNav user={user} locales={locales} resolveLocaleSwitch={switchLocale}/>
 		<RouteTransitionWrapper
 		    user={user}
@@ -411,7 +418,9 @@ const RoutedApp = ({ locales }: { locales: AvailableLocale[] }) => {
 
 const LocaleRoute: FC = () => {
   const { locale } = useParams ()
+  const uiLocale = useUILocale ()
   const location = useLocation ()
+  const verticalPreview = isVerticalPreviewPath (location.pathname)
   const { i18n } = useTranslation ()
   const { data, isError } = useQuery ({
       queryKey: localesKeys.index,
@@ -421,29 +430,30 @@ const LocaleRoute: FC = () => {
       refetchOnMount: true,
       refetchOnWindowFocus: true,
       refetchOnReconnect: true })
+  const contentLocale = verticalPreview ? 'ja' : locale
   const activeLocale =
-      (isLocaleCode (locale)
+      (isLocaleCode (contentLocale)
-       && data?.locales.some (entry => entry.code === locale))
+       && data?.locales.some (entry => entry.code === contentLocale))
-      ? locale
+      ? contentLocale
       : null
 
   useLayoutEffect (() => {
     if (activeLocale != null)
-      document.documentElement.lang = activeLocale
+      document.documentElement.lang = uiLocale
-    if (activeLocale != null && i18n.language !== activeLocale)
+    if (activeLocale != null && i18n.language !== uiLocale)
-      void i18n.changeLanguage (activeLocale)
+      void i18n.changeLanguage (uiLocale)
-  }, [activeLocale, i18n])
+  }, [activeLocale, uiLocale, i18n])
 
   const redirect = legacyLocalePath (location, pathname => resolvePageRoute (pathname) != null)
-  if (!(isLocaleCode (locale)) && redirect == null)
+  if (!(isLocaleCode (locale)) && !verticalPreview && redirect == null)
     return <NotFound/>
   if (isError && data == null)
     return <ServiceUnavailable/>
   if (data == null)
     return null
-  if (isLocaleCode (locale))
+  if (isLocaleCode (locale) || verticalPreview)
   {
-    return data.locales.some (entry => entry.code === locale)
+    return data.locales.some (entry => entry.code === contentLocale)
         ? <RoutedApp locales={data.locales}/>
         : <NotFound/>
   }
@@ -455,7 +465,8 @@ const LocaleRoute: FC = () => {
 const LocaleRedirect = ({ to }: { to: string }) => {
   const locale = useLocale ()
   const location = useLocation ()
-  return <Navigate to={switchLocalePath ({ ...location, pathname: to }, locale)} replace/>
+  return <Navigate to={localiseTo (
+      { ...location, pathname: to }, locale, location.pathname)} replace/>
 }
 
 

frontend/src/components/PostEditForm.tsx

@@ -1,6 +1,5 @@
 import { useEffect, useMemo, useState } from 'react'
 
-import ResourcePickerButton from '@/components/common/ResourcePickerButton'
 import { useLocale } from '@/lib/useLocale'
 import PostOriginalCreatedTimeField from '@/components/PostOriginalCreatedTimeField'
 import FieldError from '@/components/common/FieldError'
@@ -185,12 +184,7 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
 	    value={parentPostIds}
 	    disabled={disabled}
 	    errors={fieldErrors.parentPostIds}
-	    onChange={setParentPostIds}
+	    onChange={setParentPostIds}/>
-	    after={<ResourcePickerButton
-		source={{ resource: 'posts', field: 'resource_id' }}
-		values={parentPostIds.split (/\s+/).filter (Boolean)}
-		maximum={Number.MAX_SAFE_INTEGER} disabled={disabled}
-		onSelect={values => setParentPostIds (values.join (' '))}/>}/>
 
 	<PostTagsField
 	    disabled={disabled}

frontend/src/components/PostList.tsx

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

frontend/src/components/PrefetchLink.tsx

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

frontend/src/components/TagLink.tsx

@@ -79,7 +79,9 @@ const TagLink: FC<Props> = ({ tag,
   } as CSSProperties
   const spanClass = 'tag-link-colour'
   const linkClass = 'tag-link-colour tag-link-hover-colour'
-  const textClass = 'group min-w-0 max-w-full overflow-hidden align-bottom'
+  const textClass = cn (
+      'group [min-inline-size:0] [max-inline-size:100%]',
+      'overflow-hidden align-bottom')
   const markerWrapClass = 'shrink-0 self-start md:self-auto'
   const countClass = 'shrink-0 self-end md:self-auto'
   const matchedAlias = isFullTag (tag) ? tag.matchedAlias : null
@@ -89,7 +91,8 @@ const TagLink: FC<Props> = ({ tag,
   return (
       <span
 	  className={cn (
-	      'inline-flex min-w-0 max-w-full flex-nowrap items-stretch align-baseline',
+	      'inline-flex [min-inline-size:0] [max-inline-size:100%] flex-nowrap',
+	      'items-stretch align-baseline',
 	      'gap-x-1 md:items-baseline')}>
 	{(linkFlg && withWiki && isFullTag (tag) && tag.category !== 'nico') && (
 	    <span className={markerWrapClass}>
@@ -153,8 +156,8 @@ const TagLink: FC<Props> = ({ tag,
 	    </span>)}
 	{nestLevel > 0 && (
 	    <span
-		className="ml-1 mr-1 shrink-0"
+		className="ms-1 me-1 shrink-0"
-		style={{ paddingLeft: `${ (nestLevel - 1) }rem` }}>
+		style={{ paddingInlineStart: `${ (nestLevel - 1) }rem` }}>
 	      ↳
 	    </span>)}
 	{matchedAlias != null && (

frontend/src/components/TagSearch.tsx

@@ -3,7 +3,7 @@
 import { useEffect, useRef, useState } from 'react'
 import { useLocation } from 'react-router-dom'
 
-import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
+import { useLocale, useLocaleNavigate, useVerticalPreview } from '@/lib/useLocale'
 import { useUITranslation } from '@/lib/useUITranslation'
 import { apiGet } from '@/lib/api'
 import { inputClass } from '@/lib/utils'
@@ -18,6 +18,7 @@ import type { Tag } from '@/types'
 const TagSearch: FC = () => {
   const { message } = useUITranslation ('shared')
   const locale = useLocale ()
+  const verticalPreview = useVerticalPreview ()
   const location = useLocation ()
   const navigate = useLocaleNavigate ()
   const compositionFlgRef = useRef (false)
@@ -105,13 +106,13 @@ const TagSearch: FC = () => {
 
     switch (ev.key)
     {
-    case 'ArrowDown':
+    case verticalPreview ? 'ArrowRight' : 'ArrowDown':
       ev.preventDefault ()
       setActiveIndex (i => Math.min (i + 1, suggestions.length - 1))
       setSuggestionsVsbl (true)
       break
 
-    case 'ArrowUp':
+    case verticalPreview ? 'ArrowLeft' : 'ArrowUp':
       ev.preventDefault ()
       setActiveIndex (i => Math.max (i - 1, -1))
       setSuggestionsVsbl (true)

frontend/src/components/TagSearchBox.tsx

@@ -15,7 +15,7 @@ const TagSearchBox: FC<Props> = ({ suggestions, activeIndex, onSelect }) => {
     return
 
   return (
-      <ul className="absolute left-0 right-0 z-50 w-full
+      <ul className="tag-search-suggestions absolute left-0 right-0 z-50 w-full
 		     bg-gray-100 dark:bg-gray-800 border dark:border-gray-600
 		     rounded shadow">
 	{suggestions.map ((tag, i) => (

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 } from '@/lib/useLocale'
+import { useLocale, useLocaleNavigate, useUILocale, useVerticalPreview } from '@/lib/useLocale'
 import LocalisedText, { formatUIString } from '@/components/LocalisedText'
 import Separator from '@/components/MenuSeparator'
 import PrefetchLink from '@/components/PrefetchLink'
@@ -12,9 +12,9 @@ import TopNavUser from '@/components/TopNavUser'
 import TranslatedText from '@/components/TranslatedText'
 import { toast } from '@/components/ui/use-toast'
 import { WikiIdBus } from '@/lib/eventBus/WikiIdBus'
-import { isLocaleCode,
+import { isUILocaleCode,
-	 localeFromPath,
 	 switchLocalePath,
+	 uiLocaleFromPath,
 	 unlocalisedPath } from '@/lib/locales'
 import { uiMessage, uiMessageLanguage } from '@/lib/messages'
 import { useUITranslation } from '@/lib/useUITranslation'
@@ -28,13 +28,13 @@ import { fetchWikiPage } from '@/lib/wiki'
 
 import type { FC, MouseEvent } from 'react'
 
-import type { AvailableLocale, LocaleCode } from '@/lib/locales'
+import type { AvailableLocale, UILocaleCode } from '@/lib/locales'
 import type { Material, Menu, MenuVisibleItem, Tag, User } from '@/types'
 
 type Props = {
     user: User | null
     locales: AvailableLocale[]
-    resolveLocaleSwitch?: (locale: LocaleCode) => Promise<string> }
+    resolveLocaleSwitch?: (locale: UILocaleCode) => Promise<string> }
 type NavDensity = 'auto' | 'comfortable' | 'compact'
 
 
@@ -47,7 +47,7 @@ export const menuOutline = (
 	pathName: string },
 ): Menu => {
   const pathName = unlocalisedPath (fullPathname)
-  const locale = localeFromPath (fullPathname) ?? 'ja'
+  const locale = uiLocaleFromPath (fullPathname)
 
   const message = (
       key: Parameters<typeof uiMessage>[1],
@@ -137,7 +137,10 @@ export const menuOutline = (
 const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
   const { message, label } = useUITranslation ('shared')
   const locale = useLocale ()
-  const localeName = locales.find (entry => entry.code === locale)?.name
+  const uiLocale = useUILocale ()
+  const verticalPreview = useVerticalPreview ()
+  const uiLocales = locales.filter (entry => isUILocaleCode (entry.code))
+  const localeName = uiLocales.find (entry => entry.code === uiLocale)?.name
   const navigate = useLocaleNavigate ()
   const location = useLocation ()
   const currentLocation = useRef (location)
@@ -180,11 +183,12 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
     let node: HTMLElement | null = el
     while (node != null && node !== nav)
     {
-      left += node.offsetLeft
+      left += verticalPreview ? node.offsetTop : node.offsetLeft
       const parent: Element | null = node.offsetParent
       node = parent instanceof HTMLElement ? parent : null
     }
-    const width = node === nav ? el.offsetWidth : 0
+    const width = node === nav
+	? (verticalPreview ? el.offsetHeight : el.offsetWidth) : 0
     const visible = width > 0
     setHL (current =>
 	(current.left === left && current.width === width && current.visible === visible)
@@ -202,6 +206,7 @@ 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 ?? '')
@@ -255,8 +260,22 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
       animationsOff
       ? undefined
       : (reducedAnimations
-	 ? 'transition-[transform,width] duration-75 ease-linear'
+	 ? 'transition-[transform,width,height] duration-75 ease-linear'
-	 : 'transition-[transform,width] duration-200 ease-out')
+	 : '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 }) }
 
   const prevActiveIdxRef = useRef<number> (activeIdx)
 
@@ -287,6 +306,14 @@ 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'
@@ -351,7 +378,8 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
       removeEventListener ('resize', schedule)
       document.fonts?.removeEventListener ('loadingdone', schedule)
     }
-  }, [activeIdx, moreVsbl, desktop, density, user?.name, locale, locales, menuLabels])
+  }, [activeIdx, moreVsbl, desktop, density, user?.name, locale, locales,
+      menuLabels, verticalPreview])
 
   useEffect (() => {
     if (desktop == null || layoutReady)
@@ -378,7 +406,8 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
     measure (moreVsbl ? -1 : activeIdx)
     if (!(desktop))
       setMoreVsbl (false)
-  }, [activeIdx, moreVsbl, desktop, density, locale, animationMode, menuLabels])
+  }, [activeIdx, moreVsbl, desktop, density, locale, animationMode,
+      menuLabels, verticalPreview])
 
   useEffect (() => {
     const unsubscribe = WikiIdBus.subscribe (setWikiId)
@@ -392,6 +421,7 @@ 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)
@@ -403,7 +433,7 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
       observer?.disconnect ()
       removeEventListener ('resize', update)
     }
-  }, [activeIdx, moreVsbl, desktop, density, locale])
+  }, [activeIdx, moreVsbl, desktop, density, locale, verticalPreview])
 
   useEffect (() => {
     setMenuOpen (false)
@@ -415,17 +445,18 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 			rounded px-1 focus-within:ring-2">
 	<Globe aria-hidden="true" size={16}/>
 	<span className="top-nav-locale-name whitespace-nowrap text-sm">
-	  <LocalisedText language={locale}>{localeName}</LocalisedText>
+	  <LocalisedText language={uiLocale}>{localeName}</LocalisedText>
 	</span>
 	<select
-	    aria-label={formatUIString (localeName ?? '', locale)}
+	    aria-label={formatUIString (localeName ?? '', uiLocale)}
-	    value={locale}
+	    lang={uiLocale}
+	    value={uiLocale}
 	    disabled={switchingLocale}
 	    className="absolute inset-0 h-full w-full cursor-pointer opacity-0"
 	    onChange={async event => {
 	      const nextLocale = event.target.value
-	      if (isLocaleCode (nextLocale)
+	      if (isUILocaleCode (nextLocale)
-		  && locales.some (entry => entry.code === nextLocale))
+		  && uiLocales.some (entry => entry.code === nextLocale))
 	      {
 		const request = ++localeSwitchRequest.current
 		setSwitchingLocale (true)
@@ -450,8 +481,8 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 		}
 	      }
 	    }}>
-	  {locales.map (entry => isLocaleCode (entry.code) && (
+	  {uiLocales.map (entry => (
-	      <option key={entry.code} value={entry.code}>
+	      <option key={entry.code} value={entry.code} lang={entry.code}>
 		{formatUIString (entry.name, entry.code)}
 	      </option>))}
 	</select>
@@ -461,7 +492,7 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
       <div ref={layoutRef} className="top-nav-layout w-full min-w-0 shrink-0"
 	  data-desktop={desktop ?? undefined} data-density={density}
 	  data-layout-ready={layoutReady}>
-	<nav ref={barRef} lang={uiMessageLanguage (locale, 'posts')}
+	<nav ref={barRef} lang={uiMessageLanguage (uiLocale, 'posts')}
 	    className="top-nav-root top-nav-bar flex justify-between items-center w-full">
 	  <div className="top-nav-primary flex shrink-0 items-center h-12">
 	    <PrefetchLink
@@ -479,8 +510,11 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 		   className={cn ('absolute inset-y-0 h-12',
 				  'top-nav-highlight',
 				  highlightTransitionClass)}
-		   style={{ width:      hl.width,
+		   style={{ width:      verticalPreview ? '100%' : hl.width,
-			    transform:  `translateX(${ hl.left }px)`,
+			    height:     verticalPreview ? hl.width : undefined,
+			    transform:  verticalPreview
+				? `translateY(${ hl.left }px)`
+				: `translateX(${ hl.left }px)`,
 			    opacity:    hl.visible ? 1 : 0 }}/>
 
 	      {visibleMenu.map ((item, i) => (
@@ -554,7 +588,9 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 	      layout
 	      className="top-nav-desktop-submenu relative z-20 shrink-0
 			 overflow-hidden top-nav-submenu"
-	      animate={{ height: desktop == null ? 'auto' : submenuHeight }}
+	      animate={verticalPreview && desktop
+		  ? { width: submenuWidth, height: '100%' }
+		  : { width: 'auto', height: desktop == null ? 'auto' : submenuHeight }}
 	      onMouseLeave={() => {
 		if (moreVsbl)
 		  setMoreVsbl (false)
@@ -566,7 +602,8 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 	      onLayoutAnimationComplete={() => {
 		measure (highlightTargetRef.current)
 	      }}>
-	  <div ref={submenuContentRef} className={cn (moreVsbl && 'top-nav-more-menu')}>
+	  <div ref={submenuContentRef}
+	      className={cn ('top-nav-submenu-content', moreVsbl && 'top-nav-more-menu')}>
 	  {moreVsbl
 	   ? (
 	      moreMenu.map ((item, i) => (
@@ -576,9 +613,11 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 			  {...((item.visible ?? true)
 			       ? { layoutId: `menu-${ menu.indexOf (item) }` }
 			       : (animationsOff ? { }
-				  : { initial: { x: 40, y: -40, opacity: 0 },
+				  : { initial: {
+					  x: 40, y: verticalPreview ? 0 : -40, opacity: 0 },
 				      animate: { x: 0, y: 0, opacity: 1 },
-				      exit: { x: 40, y: -40, opacity: 0 } }))}
+				      exit: {
+					  x: 40, y: verticalPreview ? 0 : -40, opacity: 0 } }))}
 			  onLayoutAnimationComplete={() => measure (highlightTargetRef.current)}
 			  className="z-10 min-w-0 px-3 py-2 font-bold">
 			<h2>
@@ -599,10 +638,7 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 				  transition={topNavTransition}
 				  {...(visibleMenu[activeIdx] === item
 				       ? { layoutId: `submenu-${ menu.indexOf (item) }-${ j }` }
-				       : (animationsOff ? { }
+				       : submenuItemMotion)}>
-					  : { initial: { y: -40, opacity: 0 },
-					      animate: { y: 0, opacity: 1 },
-					      exit: { y: -40, opacity: 0 } }))}>
 				{subItem.component}
 			      </motion.div>)
 			  : (
@@ -612,10 +648,7 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 				  transition={topNavTransition}
 				  {...(visibleMenu[activeIdx] === item
 				       ? { layoutId: `submenu-${ menu.indexOf (item) }-${ j }` }
-				       : (animationsOff ? { }
+				       : submenuItemMotion)}>
-					  : { 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}
@@ -633,7 +666,8 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 		  <div className="relative min-h-[40px]">
 		    {animationsOff
 		     ? (
-			 <div className="flex min-h-[40px] flex-wrap items-center px-3">
+			 <div className="top-nav-submenu-items flex min-h-[40px]
+					 flex-wrap items-center px-3">
 			   {(visibleMenu[activeIdx]?.subMenu ?? [])
 			    .filter (item => item.visible ?? true)
 			    .map ((item, i) => (
@@ -662,10 +696,9 @@ const TopNav: FC<Props> = ({ user, locales, resolveLocaleSwitch }) => {
 			   <motion.div
 			       key={activeIdx}
 			       custom={dir}
-			       variants={{ enter: (d: -1 | 1) => ({ y: d * 24, opacity: 0 }),
+			       variants={submenuVariants}
-					   centre: { y: 0, opacity: 1 },
+			       className="top-nav-submenu-items relative flex min-h-[40px]
-					   exit: (d: -1 | 1) => ({ y: (-d) * 24, opacity: 0 }) }}
+					  flex-wrap items-center px-3"
-			       className="relative flex min-h-[40px] flex-wrap items-center px-3"
 			       initial="enter"
 			       animate="centre"
 			       exit="exit"

frontend/src/components/common/Form.tsx

@@ -8,7 +8,7 @@ type Props = {
 
 
 const Form: FC<Props> = ({ children, className }) => (
-    <div className={cn ('mx-auto max-w-xl space-y-4 p-4', className)}>
+    <div className={cn ('form-layout mx-auto max-w-xl space-y-4 p-4', className)}>
       {children}
     </div>)
 

frontend/src/components/common/Pagination.tsx

@@ -61,7 +61,7 @@ const Pagination: FC<Props> = ({ page, totalPages, siblingCount = 3 }) => {
   const pages = getPages (page, totalPages, siblingCount)
 
   return (
-      <nav className="mt-4 flex justify-center"
+      <nav className="pagination mt-4 flex justify-center"
 	  lang={message ('pagination.label').language}
 	  aria-label={message ('pagination.label').text}>
 	<div className="flex items-center gap-2">

frontend/src/components/common/ResourcePickerButton.tsx

@@ -1,27 +0,0 @@
-import CandidatePicker from '@/components/common/CandidatePicker'
-import { Button } from '@/components/ui/button'
-import useDialogue from '@/lib/dialogues/useDialogue'
-import { useUITranslation } from '@/lib/useUITranslation'
-
-import type { CandidateSource } from '@/components/common/CandidatePicker'
-
-
-const ResourcePickerButton = (
-    { source, values, maximum = 1, disabled, onSelect }: {
-	source: CandidateSource; values: (string | number | boolean)[]
-	maximum?: number; disabled?: boolean
-	onSelect: (values: string[]) => void },
-) => {
-  const dialogue = useDialogue ()
-  const { label } = useUITranslation ('counts')
-  return <Button type="button" variant="outline" disabled={disabled || maximum === 0}
-      onClick={() => void dialogue.form ({
-	  title: label ('pattern.link'), size: 'large', footerLayout: 'inline',
-	  body: controls => <CandidatePicker source={source} initial={values}
-	      maximum={maximum} controls={controls} onSelect={onSelect}/> })}>
-    {label ('pattern.selection')}
-  </Button>
-}
-
-
-export default ResourcePickerButton

frontend/src/components/common/TextArea.tsx

@@ -12,7 +12,7 @@ export default forwardRef<HTMLTextAreaElement, Props> (
 	<textarea
 	    ref={ref}
 	    aria-invalid={invalid}
-	    className={cn ('rounded border w-full p-2 h-32',
+	    className={cn ('rounded border [inline-size:100%] p-2 [block-size:8rem]',
 			   (invalid
 			    ? ['border-red-500 bg-red-50 text-red-900',
 			       'focus:border-red-500 focus:outline-none focus:ring-2',

frontend/src/components/counts/CountsAdditionalConditions.tsx

@@ -2,10 +2,9 @@ import { useEffect, useState } from 'react'
 
 import CountsConditionValues from '@/components/counts/CountsConditionValues'
 import DateTimeField from '@/components/common/DateTimeField'
-import ResourcePickerButton from '@/components/common/ResourcePickerButton'
 import { Button } from '@/components/ui/button'
-import { countsCandidateSource, countsConditionInputs, countsEventTypes, countsFieldLabel,
+import { countsConditionInputs, countsEventTypes, countsFieldLabel, countsFilterFields,
-	 countsFilterFields, countsSetOperators, useCountsDefinition }
+	 countsSetOperators, useCountsDefinition }
     from '@/lib/countsDefinitions'
 import useDialogue from '@/lib/dialogues/useDialogue'
 import { countsConditionValue } from '@/lib/countsDisplay'
@@ -16,7 +15,7 @@ import { useUITranslation } from '@/lib/useUITranslation'
 
 import { readCountState, encodeCountState } from '@/lib/queryState'
 
-import type { CountsResource, CountsResult } from '@/lib/counts'
+import type { CountsResult } from '@/lib/counts'
 import type { DialogueFormControls } from '@/lib/dialogues/useDialogue'
 import type { CountsCondition, CountsDefinition } from '@/lib/countsDefinitions'
 
@@ -95,9 +94,7 @@ const ConditionEditor = (
 }
 
 
-const CountsAdditionalConditions = (
+const CountsAdditionalConditions = ({ params, update, conditionLabels }: {
-    { resource, params, update, conditionLabels }: {
-	resource: CountsResource
     conditionLabels?: CountsResult['conditionLabels']
     params: URLSearchParams
     update: (key: string, value: string) => void },
@@ -152,19 +149,11 @@ const CountsAdditionalConditions = (
 	  value={condition[key] == null ? '' : String (condition[key])} disabled={condition.blank}
 	  aria-label={aria.text} lang={aria.language}
 	  onChange={value => patch (index, { [key]: value ?? '' })}/>
-    const source = countsCandidateSource (resource, condition.field, params)
+    return <input value={condition[key] == null ? '' : String (condition[key])} disabled={condition.blank}
-    const value = condition[key]
-    return <>
-      <input value={condition[key] == null ? '' : String (condition[key])}
-	  disabled={condition.blank}
 	type={(type === 'integer' || type === 'interval') ? 'number' : 'text'}
 	className={inputClass (false, 'h-10 w-36 min-w-0 max-w-full py-1')}
 	aria-label={aria.text} lang={aria.language}
 	onChange={event => patch (index, { [key]: event.target.value })}/>
-      {source != null && <ResourcePickerButton source={source} disabled={condition.blank}
-	  values={value == null ? [] : [value]}
-	  onSelect={values => patch (index, { [key]: values[0] ?? '' })}/>}
-    </>
   }
   return <fieldset className="min-w-0 space-y-1">
     <legend className="flex items-center gap-2">{label ('additionalConditions')}
@@ -193,7 +182,7 @@ const CountsAdditionalConditions = (
 	  </Button>
 	  {countsSetOperators.includes (condition.operator) ? (
 	      <CountsConditionValues key={`${condition.field}:${condition.operator}`}
-		  condition={condition} resource={resource}
+		  condition={condition}
 		  field={metadata.find (field => field.key === condition.field)!}
 		  definition={definition} params={params}
 		  maximum={Math.max (0, 100 - conditions.reduce ((sum, item, position) =>

frontend/src/components/counts/CountsCandidatePicker.tsx

@@ -10,19 +10,16 @@ import { useUITranslation } from '@/lib/useUITranslation'
 import { inputClass } from '@/lib/utils'
 
 import type { DialogueFormControls } from '@/lib/dialogues/useDialogue'
-import type { CountsResource } from '@/lib/counts'
+import type { CountsCandidate, CountsDefinition, CountsFieldMetadata }
-import type { CountsCandidate } from '@/lib/countsDefinitions'
+    from '@/lib/countsDefinitions'
 
 
-type CandidateSource = {
+const CountsCandidatePicker = (
-    resource: CountsResource; field: string; params?: URLSearchParams }
+    { field, definition, params, initial, maximum, controls, save }: {
-
+	field: CountsFieldMetadata; params: URLSearchParams
-const CandidatePicker = (
+	definition: CountsDefinition
-    { source, choices = [], categories = [], initial, maximum, controls, onSelect }: {
-	source?: CandidateSource; choices?: CountsCandidate[]
-	categories?: { value: string; label: string }[]
 	initial: (string | number | boolean)[]; maximum: number
-	controls: DialogueFormControls; onSelect: (values: string[]) => void },
+	controls: DialogueFormControls; save: (values: string[]) => void },
 ) => {
   const { label, message } = useUITranslation ('counts')
   const locale = useLocale ()
@@ -32,58 +29,49 @@ const CandidatePicker = (
   const [search, setSearch] = useState ('')
   const [category, setCategory] = useState ('')
   const [page, setPage] = useState (1)
-  const params = source?.params ?? new URLSearchParams ()
   const point = useRef (params.get ('execution_at'))
-  const resource = source?.resource ?? 'posts'
+  const request = new URLSearchParams ({ field: field.key, query: search, page: String (page) })
-  const request = new URLSearchParams ({
-      field: source?.field ?? '', query: search, page: String (page) })
   for (const key of ['timezone', 'at', 'execution_at'])
     if (params.has (key)) request.set (key, params.get (key)!)
   if (countsUseLatest (params)) request.delete ('at')
   if (category) request.set ('category', category)
-  const dynamic = source != null
+  const dynamic = field.candidateSource === 'tags'
   const { data, isFetching: fetching, isError: errorFlg } = useQuery ({
-      queryKey: countsKeys.candidates (resource, request.toString (), locale), enabled: dynamic,
+      queryKey: countsKeys.candidates (request.toString (), locale), enabled: dynamic,
       queryFn: ({ signal }) => {
 	const pinned = new URLSearchParams (request)
 	if (point.current != null) pinned.set ('execution_at', point.current)
-	return fetchCountsCandidates (resource, pinned, locale, signal)
+	return fetchCountsCandidates (pinned, locale, signal)
-      }, retry: false, staleTime: 0, gcTime: 0 })
+      }, retry: false })
   useEffect (() => {
     if (data != null) point.current = data.executionAt
   }, [data])
   useEffect (() => {
     controls.setActions ([{ label: label ('counts:pattern.selection'),
-	onSelect: () => onSelect ([...selected]) }])
+	onSelect: () => save ([...selected]) }])
-  }, [controls, label, onSelect, selected])
+  }, [controls, label, save, selected])
-  const rows = dynamic ? data?.rows ?? [] : choices.filter (row =>
+  const fixed: CountsCandidate[] = (field.choices ?? []).map (choice => ({
+      value: choice.value, name: message (choice.label).text }))
+  const rows = dynamic ? data?.rows ?? [] : fixed.filter (row =>
       row.name?.includes (search))
   const headings: Record<string, string> = {
       id: 'columns.resourceId', name: 'columns.name', category: 'common:categoryLabel',
       kind: 'columns.kind' }
-  const referenceFlg = ['tags', 'tags_json', 'tags.id', 'members'].includes (source?.field ?? '')
+  const available = dynamic ? ['id', 'name', 'category', 'kind'] : ['name']
-  const available =
-      dynamic
-      ? (referenceFlg ? ['id', 'name', 'category', 'kind'] : ['id', 'name']) : ['name']
   const visible = available.filter (column => columns.includes (column))
+  const categories = definition.filterFields?.find (field =>
+      field.candidateSource === 'categories')?.choices ?? []
   const cell = (row: CountsCandidate, column: string) => {
-    if (column === 'category')
+    if (column === 'category') return row.category == null ? ''
-      return row.category == null ? '' : message (`common:categories.${row.category}`).text
+	: message (`common:categories.${row.category}`).text
-    if (column === 'kind')
+    if (column === 'kind') return row.kind == null ? '' : message (`kinds.${row.kind}`).text
-    {
-      const key = row.kind === 'group' ? 'resources.tag_groups' : `kinds.${row.kind}`
-      return row.kind == null ? '' : message (key).text
-    }
     return column === 'id' ? row.id : row.name
   }
   return <div className="min-w-0 space-y-2">
     <div className="flex min-w-0 items-center gap-2">
       <input className={inputClass (false, 'h-9 min-w-0 flex-1')}
-	  aria-label={message ('common:search').text} value={draft} maxLength={1000}
+	  aria-label={message ('common:search').text} value={draft}
-	  onChange={event => {
+	  onChange={event => setDraft (event.target.value)}
-	    const value = event.target.value
-	    if (new TextEncoder ().encode (value).length <= 1000) setDraft (value)
-	  }}
 	  onKeyDown={event => {
 	    if (event.key !== 'Enter') return
 	    event.preventDefault ()
@@ -93,7 +81,7 @@ const CandidatePicker = (
       <Button type="button" onClick={() => { setSearch (draft); setPage (1) }}>
 	{label ('common:search')}</Button>
     </div>
-    {categories.length > 0 && <select className={inputClass (false, 'h-9 w-full')}
+    {dynamic && <select className={inputClass (false, 'h-9 w-full')}
 	aria-label={message ('common:categoryLabel').text} value={category}
 	onChange={event => { setCategory (event.target.value); setPage (1) }}>
       <option value=""/>
@@ -120,13 +108,12 @@ const CandidatePicker = (
 	  {visible.map (column => <th key={column} className="p-2">
 	    {label (headings[column])}</th>)}
 	</tr></thead>
-	<tbody>{rows.map (row => <tr key={`${row.kind ?? ''}:${row.value}`}
+	<tbody>{rows.map (row => <tr key={row.value} className="border-t dark:border-slate-700">
-	    className="border-t dark:border-slate-700">
 	  <td className="p-2"><input type="checkbox" checked={selected.has (row.value)}
 	      aria-label={row.name ?? String (row.id ?? '')}
-	      disabled={maximum !== 1 && !selected.has (row.value) && selected.size >= maximum}
+	      disabled={!selected.has (row.value) && selected.size >= maximum}
 	      onChange={event => setSelected (previous => {
-		const next = new Set (maximum === 1 ? [] : previous)
+		const next = new Set (previous)
 		if (event.target.checked) next.add (row.value)
 		else next.delete (row.value)
 		return next
@@ -141,8 +128,7 @@ const CandidatePicker = (
 	  onClick={() => setPage (previous => previous - 1)}>
 	{label ('common:pagination.previous')}</Button>
       <span>{page}</span>
-      <Button type="button" variant="outline"
+      <Button type="button" variant="outline" disabled={!data?.more || fetching}
-	  disabled={!data?.more || page >= 100_000 || fetching}
 	  onClick={() => setPage (previous => previous + 1)}>
 	{label ('common:pagination.next')}</Button>
     </div>}
@@ -150,5 +136,4 @@ const CandidatePicker = (
 }
 
 
-export default CandidatePicker
+export default CountsCandidatePicker
-export type { CandidateSource }

frontend/src/components/counts/CountsConditionValues.tsx

@@ -1,22 +1,18 @@
 import { useState } from 'react'
 
-import CandidatePicker from '@/components/common/CandidatePicker'
+import CountsCandidatePicker from '@/components/counts/CountsCandidatePicker'
 import DateTimeField from '@/components/common/DateTimeField'
-import ResourcePickerButton from '@/components/common/ResourcePickerButton'
 import { Button } from '@/components/ui/button'
-import { countsCandidateSource } from '@/lib/countsDefinitions'
 import useDialogue from '@/lib/dialogues/useDialogue'
 import { inputClass } from '@/lib/utils'
 import { useUITranslation } from '@/lib/useUITranslation'
 
-import type { CountsResource } from '@/lib/counts'
 import type { CountsCondition, CountsDefinition, CountsFieldMetadata }
     from '@/lib/countsDefinitions'
 
 
 const CountsConditionValues = (
-    { resource, condition, field, definition, params, maximum, change }: {
+    { condition, field, definition, params, maximum, change }: {
-	resource: CountsResource
 	condition: CountsCondition; field: CountsFieldMetadata; definition: CountsDefinition
 	params: URLSearchParams; maximum: number
 	change: (values: (string | number | boolean)[]) => void },
@@ -25,21 +21,11 @@ const CountsConditionValues = (
   const dialogue = useDialogue ()
   const [draft, setDraft] = useState ('')
   const values = condition.values ?? []
-  const source = countsCandidateSource (resource, field.key, params)
   const pick = () => {
     void dialogue.form ({ title: label (field.candidateSource === 'tags'
 	? 'counts:pattern.link' : 'counts:pattern.pattern'), size: 'large', footerLayout: 'inline',
-	body: controls => <CandidatePicker
+	body: controls => <CountsCandidatePicker field={field} definition={definition}
-	    source={
+	    params={params} initial={values} maximum={maximum} controls={controls} save={change}/> })
-		field.candidateSource === 'tags'
-		? { resource: 'posts', field: field.key, params } : undefined}
-	    choices={(field.choices ?? []).map (choice => ({
-		value: choice.value, name: message (choice.label).text }))}
-	    categories={
-		field.candidateSource === 'tags'
-		? definition.filterFields?.find (field =>
-		    field.candidateSource === 'categories')?.choices : undefined}
-	    initial={values} maximum={maximum} controls={controls} onSelect={change}/> })
   }
   if (condition.input === 'list' || field.candidateSource === 'tags')
     return <Button type="button" variant="outline" disabled={condition.blank} onClick={pick}>
@@ -87,8 +73,6 @@ const CountsConditionValues = (
 	  onClick={() => change (values.filter ((_, position) => position !== index))}>×</Button>
     </span>)}
     {input ()}
-    {source != null && <ResourcePickerButton source={source} values={values}
-	maximum={maximum} disabled={condition.blank} onSelect={change}/>}
     <Button type="button" variant="outline" disabled={condition.blank || draft === ''
 	|| values.length >= maximum} onClick={append}>{label ('add')}</Button>
     <Button type="button" variant="ghost" disabled={condition.blank}

frontend/src/components/counts/CountsControls.tsx

@@ -7,7 +7,6 @@ import AnimatedCollapse from '@/components/common/AnimatedCollapse'
 import DateTimeField from '@/components/common/DateTimeField'
 import FormField from '@/components/common/FormField'
 import HelpPopover from '@/components/common/HelpPopover'
-import ResourcePickerButton from '@/components/common/ResourcePickerButton'
 import TagInput from '@/components/common/TagInput'
 import { Button } from '@/components/ui/button'
 import { countsRequestParams, countsUseLatest, fieldsForCounts, normaliseCountsParams, readCountSort,
@@ -224,17 +223,11 @@ const CountsControls = (
             {['resource_id', 'user_id'].map (key => <FormField key={key}
                 label={label (key === 'resource_id' ? 'columns.resourceId'
                     : 'fields.actor')}>
-              {() => <div className="flex flex-wrap items-center gap-1">
+              {() => <input value={draft.get (key) ?? ''}
-		<input value={draft.get (key) ?? ''}
                   aria-label={message (key === 'resource_id' ? 'columns.resourceId'
                       : 'fields.actor').text}
                   className={inputClass (false, 'w-28 py-1')}
-		    onChange={event => update (key, event.target.value)}/>
+                  onChange={event => update (key, event.target.value)}/>}
-		<ResourcePickerButton source={{ resource,
-		    field: key === 'resource_id' ? key : 'user', params: draft }}
-		    values={draft.get (key) ? [draft.get (key)!] : []}
-		    onSelect={values => update (key, values[0] ?? '')}/>
-	      </div>}
             </FormField>)}
           </div>
           {resource === 'posts' && <FormField label={label ('columns.tags')}>
@@ -270,7 +263,7 @@ const CountsControls = (
               </>}
             </div>}
           </FormField>}
-	  <CountsAdditionalConditions resource={resource} params={draft} update={update}
+	  <CountsAdditionalConditions params={draft} update={update}
               conditionLabels={(labelParams != null
                   && draft.get ('current') === labelParams.get ('current')
                   && draft.get ('at') === labelParams.get ('at')

frontend/src/components/dialogues/DialogueProvider.tsx

@@ -227,13 +227,11 @@ const DialogueProvider: FC<Props> = ({ children }) => {
 		       </DialogHeader>
 
 		       <div className="min-h-0 flex-1 overflow-y-auto overscroll-contain">
-			 <DialogueProvider key={active.id}>
 			 {active.options.body (
 			     formControls.current[active.id] ??= {
 				 close: () => closeRequest (active.id),
 				 setActions: actions => setRequestActions (active.id, actions),
 				 confirm: options => openNestedConfirm (active.id, options) })}
-			 </DialogueProvider>
 		       </div>
 
 		       <DialogFooter

frontend/src/components/layout/MainArea.tsx

@@ -1,7 +1,10 @@
 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'
@@ -9,21 +12,71 @@ import type { FC, ReactNode } from 'react'
 type Props = {
     children:   ReactNode
     className?: string
-    animateLayout?: boolean }
+    animateLayout?: boolean
+    verticalContent?: boolean }
 
 
-const MainArea: FC<Props> = ({ children, className, animateLayout = true }) => {
+const MainArea: FC<Props> = (
+    { children, className, animateLayout = true, verticalContent = 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 } },
+      { 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])
 
   return (
       <motion.main
+	  ref={rootRef}
+	  data-vertical-content={horizontal || undefined}
+	  tabIndex={horizontal ? 0 : undefined}
 	  transition={{ layout: layoutTransition }}
-	  className={cn ('flex-1 overflow-y-auto p-4', className)}
+	  className={cn ('main-area flex-1 overflow-y-auto p-4', className)}
 	  layout={(animationMode === 'off' || !animateLayout) ? false : 'position'}>
 	{children}
       </motion.main>)

frontend/src/components/layout/SidebarComponent.tsx

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

@@ -1,4 +1,3 @@
-import ResourcePickerButton from '@/components/common/ResourcePickerButton'
 import PostOriginalCreatedTimeField from '@/components/PostOriginalCreatedTimeField'
 import PostTagsField from '@/components/posts/PostTagsField'
 import PostTextField from '@/components/posts/PostTextField'
@@ -89,12 +88,7 @@ const PostCoreDataFields: FC<PostCoreDataFieldsProps> = (
           disabled={parentPostIds.disabled}
           warnings={parentPostIds.warnings}
           errors={parentPostIds.errors}
-          onChange={parentPostIds.onChange}
+          onChange={parentPostIds.onChange}/>
-	  after={<ResourcePickerButton
-	      source={{ resource: 'posts', field: 'resource_id' }}
-	      values={parentPostIds.value.split (/\s+/).filter (Boolean)}
-	      maximum={Number.MAX_SAFE_INTEGER} disabled={parentPostIds.disabled}
-	      onSelect={values => parentPostIds.onChange (values.join (' '))}/>}/>
     </>)
 
 export default PostCoreDataFields

frontend/src/components/posts/PostTextField.tsx

@@ -34,8 +34,6 @@ const PostTextField: FC<Props> = (
     <FormField label={label} messages={errors}>
       {({ describedBy, invalid }) => (
           <>
-	    <div className="flex items-center gap-2">
-	      <div className="min-w-0 flex-1">
             <input
                 type={type}
                 value={value}
@@ -46,10 +44,8 @@ const PostTextField: FC<Props> = (
                 aria-describedby={describedBy}
                 aria-invalid={invalid}
                 className={inputClass (invalid, className)}/>
-	      </div>
-	      {after}
-	    </div>
             <FieldWarning messages={warnings}/>
+            {after}
           </>)}
     </FormField>)
 

frontend/src/components/ui/button.tsx

@@ -32,10 +32,10 @@ const buttonVariants = cva (
 	link:
 	  'text-blue-700 underline-offset-4 hover:underline dark:text-blue-300'},
       size: {
-	default: 'h-10 px-4 py-2',
+	default: '[block-size:2.5rem] [padding-inline:1rem] [padding-block:.5rem]',
-	sm:      'h-9 rounded-md px-3',
+	sm:      '[block-size:2.25rem] rounded-md [padding-inline:.75rem]',
-	lg:      'h-11 rounded-md px-8',
+	lg:      '[block-size:2.75rem] rounded-md [padding-inline:2rem]',
-	icon:    'h-10 w-10'}},
+	icon:    '[block-size:2.5rem] [inline-size:2.5rem]'}},
     defaultVariants: {
       variant: 'default',
       size:    'default'}})

frontend/src/config.test.ts

@@ -0,0 +1,9 @@
+import { describe, expect, it } from 'vitest'
+
+import { API_BASE_URL } from '@/config'
+
+describe ('test API configuration', () => {
+  it ('resolves the sample configuration without a local config file', () => {
+    expect (API_BASE_URL).toBe ('/api')
+  })
+})

frontend/src/entry-server.tsx

@@ -9,7 +9,8 @@ import { createStaticHandler, createStaticRouter,
 import { AppFrame, appRoutes, resolvePageRoute } from '@/App'
 import { apiGet, isApiError } from '@/lib/api'
 import { createUII18n } from '@/lib/i18n'
-import { fetchLocales, isLocaleCode, legacyLocalePath } from '@/lib/locales'
+import { fetchLocales, isLocaleCode, isVerticalPreviewPath,
+	 legacyLocalePath, uiLocaleFromPath } from '@/lib/locales'
 import { localesKeys, sessionKeys } from '@/lib/queryKeys'
 import { withRenderContext } from '@/lib/renderContext.server'
 
@@ -72,13 +73,16 @@ 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 uiLocale = uiLocaleFromPath (pathname)
+  const routePrefix = verticalPreview ? 'mn-Mong' : locale
   if (known?.route.handle?.redirectTo != null)
     return { status: 308,
-      location: `/${locale}${known.route.handle.redirectTo}${url.search}` }
+      location: `/${routePrefix}${known.route.handle.redirectTo}${url.search}` }
   const requestContext: RenderContext & { status: number } = {
       pathname: url.pathname, origin, apiBaseURL,
       ...authentication, status: 200 }
@@ -106,14 +110,15 @@ export const render = async (
 	}
       }
       const prepare = known?.route.handle?.prepare
-      let status = known == null || !active || !isLocaleCode (segment) ? 404 : 200
+      const routeLocaleValid = isLocaleCode (segment) || verticalPreview
+      let status = known == null || !active || !routeLocaleValid ? 404 : 200
       if (status === 200 && known?.route.handle?.authentication != null
 	  && client.getQueryData (sessionKeys.current) == null)
 	status = 401
       if (prepare != null && known != null && status === 200)
 	status = await prepare ({ client, params: known.params, locale,
 	    searchParams: url.searchParams })
-      const instance = createUII18n (locale)
+      const instance = createUII18n (uiLocale)
       const handler = createStaticHandler (appRoutes)
       const context = await handler.query (new Request (url))
       if (context instanceof Response)
@@ -183,11 +188,11 @@ export const render = async (
 	      isAxiosError: true, response: {
 		status: isApiError (query.state.error) ? query.state.error.response?.status : 500 } } }
       })) }
-      const bootstrap = JSON.stringify ({ state, status, locale,
+      const bootstrap = JSON.stringify ({ state, status, locale: uiLocale,
 	  url: url.pathname + url.search })
 	  .replace (/</g, '\\u003c').replace (/\u2028/g, '\\u2028')
 	  .replace (/\u2029/g, '\\u2029')
-      return { status, html, head, locale, bootstrap,
+      return { status, html, head, locale: uiLocale, bootstrap,
 	  setCookies: requestContext.setCookies }
     }
     finally

frontend/src/index.css

@@ -625,3 +625,642 @@ body
   white-space: nowrap;
   will-change: transform;
 }
+
+/* Locally hosted Mongolian font; the OFL accompanies the font file. */
+@font-face
+{
+  font-family: 'BTRC Mongolian';
+  src: url('/fonts/noto-sans-mongolian/NotoSansMongolian-Regular.ttf') format('truetype');
+  font-weight: 400;
+  font-style: normal;
+  font-display: swap;
+}
+
+/* Mongolian flows down each line, then into the next column on the right. */
+:lang(mn-Mong)
+{
+  font-family: 'BTRC Mongolian', 'Mongolian Baiti', 'Noto Sans JP Variable', sans-serif;
+}
+
+/* Include portalled dialogues and toasts, and controls with UA writing modes. */
+html:lang(mn-Mong) body > :not(#root),
+html:lang(mn-Mong) #root > :not(.app-layout),
+html:lang(mn-Mong) :is(button, input, select, textarea),
+[data-vertical-preview] :is(
+    .main-area:not(.posts-main-area, .tags-main-area, .wiki-main-area),
+    .sidebar > *, .tag-list-filter, .post-list > *,
+    .top-nav-brand-link, .top-nav-menu-link,
+    .top-nav-user-desktop, .top-nav-user-mobile, .top-nav-mobile-menu)
+{
+  writing-mode: vertical-lr;
+  text-orientation: mixed;
+}
+
+/* Existing Japanese vertical decorations must also advance to the right. */
+html:lang(mn-Mong) [style*='writing-mode']
+{
+  writing-mode: vertical-lr !important;
+}
+
+/* Inline alignment turns left/right into top/bottom; flex cross alignment
+   and table vertical-align already follow the vertical writing mode. */
+html:lang(mn-Mong) .text-left
+{
+  text-align: start;
+}
+
+html:lang(mn-Mong) .text-right
+{
+  text-align: end;
+}
+
+[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;
+}
+
+/* Specialised lists below retain their own grid and table layouts. */
+[data-vertical-preview] .main-area[data-vertical-content]:not(
+    .posts-main-area, .tags-main-area, .wiki-main-area)
+{
+  writing-mode: vertical-lr;
+  text-orientation: mixed;
+  text-align: start;
+  overflow-y: auto;
+}
+
+[data-vertical-preview] .main-area[data-vertical-content]:not(
+    .posts-main-area, .tags-main-area, .wiki-main-area) > :is(div, article, section)
+{
+  max-width: none;
+  max-inline-size: 100%;
+}
+
+[data-vertical-preview] .main-area[data-vertical-content] .prose
+{
+  max-width: none;
+  max-inline-size: 100%;
+}
+
+/* Input and data widgets retain nested scrolling in the vertical text flow. */
+[data-vertical-preview] .main-area[data-vertical-content] :is(
+    form, .form-layout, pre, .overflow-x-auto, .rc-md-editor, .not-prose)
+{
+  writing-mode: vertical-lr;
+  text-orientation: mixed;
+  max-height: 100%;
+  overflow: auto;
+}
+
+[data-vertical-preview] .main-area[data-vertical-content] :is(form, .form-layout)
+{
+  width: auto;
+  inline-size: min(36rem, 100%);
+}
+
+[data-vertical-preview] :where(.main-area[data-vertical-content]) :is(
+    button, input, select, textarea, code, time, table)
+{
+  writing-mode: vertical-lr;
+}
+
+[data-vertical-preview] .main-area[data-vertical-content] :is(img, video, iframe, canvas)
+{
+  max-height: 100%;
+  object-fit: 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
+{
+  writing-mode: vertical-lr;
+  text-orientation: mixed;
+  display: block;
+  width: auto;
+  height: 100%;
+}
+
+[data-vertical-preview] .sidebar > form > input[type='text']
+{
+  writing-mode: vertical-lr;
+  text-orientation: mixed;
+  width: auto;
+  height: 100%;
+  min-height: 0;
+  padding: .75rem .5rem;
+}
+
+[data-vertical-preview] .sidebar > form > .tag-search-suggestions
+{
+  inset: auto;
+  inset-inline-start: 0;
+  inset-block-start: 100%;
+  width: auto;
+  inline-size: 100%;
+  max-block-size: min(16rem, 75vw);
+  margin: 0;
+  overflow: auto;
+}
+
+[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] .top-nav-locale-name:has(:lang(mn-Mong))
+{
+  display: inline;
+  writing-mode: vertical-lr;
+  text-orientation: mixed;
+  font-size: 1.25rem;
+  line-height: 1.5;
+  flex-shrink: 0;
+}
+
+[data-vertical-preview] .top-nav-menu-link:has(.top-nav-locale-name)
+{
+  height: auto;
+  min-height: 2rem;
+}
+
+/* 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: none;
+  flex-direction: row;
+  justify-content: space-between;
+  height: 100%;
+  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: vertical-lr;
+}
+
+[data-vertical-preview] .main-area[data-vertical-content] .pagination
+{
+  align-self: stretch;
+  inline-size: 100%;
+}
+
+[data-vertical-preview] .tags-main-area
+{
+  display: flex;
+  align-items: stretch;
+  gap: 1.5rem;
+}
+
+[data-vertical-preview] .tag-list-filter
+{
+  flex: none;
+  width: auto;
+  inline-size: min(24rem, 100%);
+  max-inline-size: none;
+  overflow: 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-inline-size: 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;
+}
+
+[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: vertical-lr;
+  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: vertical-lr;
+}
+
+[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: vertical-lr;
+  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: 3.5rem;
+    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: none;
+    white-space: nowrap;
+    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: none;
+    white-space: nowrap;
+  }
+
+  [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: vertical-lr;
+  }
+
+  [data-vertical-preview] .top-nav-desktop-submenu
+  {
+    min-width: 0;
+    height: 100%;
+  }
+
+  [data-vertical-preview] .top-nav-submenu-content
+  {
+    writing-mode: vertical-lr;
+    text-orientation: mixed;
+    width: max-content;
+    max-width: 35vw;
+    height: 100%;
+    overflow-x: auto;
+    overflow-y: hidden;
+  }
+
+  [data-vertical-preview] .top-nav-submenu-content:not(.top-nav-more-menu) > div
+  {
+    height: 100%;
+  }
+
+  [data-vertical-preview] :is(.top-nav-submenu-items, .top-nav-more-links)
+  {
+    flex-direction: row;
+    flex-wrap: wrap;
+    align-items: stretch;
+    max-height: 100%;
+    padding-inline: .75rem;
+    padding-block: 0;
+  }
+
+  [data-vertical-preview] .top-nav-desktop-submenu .top-nav-menu-link
+  {
+    min-height: 0;
+    min-width: 40px;
+    padding-inline: .75rem;
+    padding-block: .5rem;
+  }
+
+  [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/countsDefinitions.ts

@@ -89,19 +89,18 @@ export const fetchCountsDefinition = (
     .then (definition => localiseCountsDefinition (definition, locale))
 
 export type CountsCandidate = {
-    value: string; id?: number | string; name: string | null; category?: string | null
+    value: string; id?: number; name: string | null; category?: string | null
     names?: Record<string, unknown>
-    kind?: 'internal' | 'external' | 'group' }
+    kind?: 'internal' | 'external' }
 export type CountsCandidatesResult = {
     rows: CountsCandidate[]; page: number; more: boolean; executionAt: string }
 
 export const fetchCountsCandidates = (
-    resource: CountsResource,
     params: URLSearchParams,
     locale: LocaleCode,
     signal?: AbortSignal,
 ): Promise<CountsCandidatesResult> => apiGet (
-    `/counts/definitions/${encodeURIComponent (resource)}/candidates`, {
+    '/counts/definitions/posts/candidates', {
 	params: Object.fromEntries (params), locale, signal })
 
 export const countsSetOperators = ['in', 'not_in', 'any', 'all', 'none']
@@ -156,25 +155,3 @@ export const countsAxisFields = (
     history: boolean,
 ): CountField[] => definition.axes[history ? 'history' : 'latest']
     .map (key => ({ key, label: countsFieldLabel (key) }))
-
-
-export const countsCandidateSource = (
-    resource: CountsResource,
-    field: string,
-    params: URLSearchParams,
-): { resource: CountsResource; field: string; params: URLSearchParams } | undefined => {
-  if (['resource_id', 'user', 'updated_by_user_id', 'file_blob_id', 'source_file_id']
-      .includes (field)) return { resource, field, params }
-  if (field === 'user.id') return { resource, field: 'user', params }
-  if ((field === 'tags.id' && resource === 'posts')
-      || (field === 'members' && resource === 'tag_groups'))
-    return { resource, field, params }
-  const leaf = field.split ('.').at (-1) ?? ''
-  const targets: Record<string, CountsResource> = {
-      tagGroupId: 'tag_groups', tagId: 'tags', tag_id: 'tags', parent_id: 'materials',
-      parents: resource === 'posts' ? 'posts' : 'tags',
-      'parents.id': resource === 'posts' ? 'posts' : 'tags',
-      parent_post_ids: 'posts', parent_tag_ids: 'tags' }
-  const target = targets[field] ?? targets[leaf]
-  return target == null ? undefined : { resource: target, field: 'resource_id', params }
-}

frontend/src/lib/i18n.ts

@@ -1,9 +1,11 @@
 import { createInstance } from 'i18next'
 import { initReactI18next } from 'react-i18next'
 
+import { MONGOLIAN_LOCALE, SUPPORTED_LOCALES } from '@/lib/locales'
+
 import type { i18n as I18n, TOptions } from 'i18next'
 
-import type { LocaleCode } from '@/lib/locales'
+import type { UILocaleCode } from '@/lib/locales'
 
 // Keep Japanese placeholders editable without reporting them as completed translations.
 const translatedResource = (resource: Record<string, unknown>): Record<string, unknown> => {
@@ -34,9 +36,14 @@ for (const [path, dictionary] of Object.entries (dictionaries))
   const [, , locale, filename] = path.split ('/')
   resources[locale] ??= { }
   resources[locale][filename.slice (0, -5)] =
-      locale === 'ain-Kana' ? translatedResource (dictionary) : dictionary
+      locale === 'ja' ? dictionary : translatedResource (dictionary)
 }
 const namespaces = Object.keys (resources.ja ?? { })
+// No Mongolian translations yet; preserve the existing fallback language metadata.
+resources[MONGOLIAN_LOCALE.code] ??= { }
+for (const namespace of namespaces)
+  resources[MONGOLIAN_LOCALE.code][namespace] ??=
+      translatedResource ({ _untranslated: ['*'] })
 
 
 export const createUII18n = (locale: string): I18n => {
@@ -44,7 +51,7 @@ export const createUII18n = (locale: string): I18n => {
   void instance.init ({
       lng: locale,
       fallbackLng: 'ja',
-      supportedLngs: ['ja', 'ain-Kana'],
+      supportedLngs: [...SUPPORTED_LOCALES, MONGOLIAN_LOCALE.code],
       load: 'currentOnly',
       initAsync: false,
       defaultNS: 'navigation',
@@ -122,7 +129,7 @@ export const languageUIMessage = (
 
 
 export const untranslatedKeys = (
-    locale: LocaleCode,
+    locale: UILocaleCode,
     namespace = 'navigation',
 ): string[] => {
   const collect = (resource: Record<string, unknown>, prefix = ''): string[] =>

frontend/src/lib/locales.ts

@@ -7,6 +7,10 @@ export const SUPPORTED_LOCALES = ['ja', 'ain-Kana'] as const
 
 export type LocaleCode = typeof SUPPORTED_LOCALES[number]
 
+// This UI locale uses Japanese content until the API supports Mongolian.
+export const MONGOLIAN_LOCALE = { code: 'mn-Mong', name: 'ᠮᠣᠩᠭᠣᠯ' } as const
+export type UILocaleCode = LocaleCode | typeof MONGOLIAN_LOCALE.code
+
 export type AvailableLocale = { code: string; name: string }
 
 
@@ -28,6 +32,19 @@ export const localeFromPath = (pathname: string): LocaleCode | null => {
 }
 
 
+// Frontend layout selection must not change the API's content locale.
+export const isVerticalPreviewPath = (pathname: string): boolean =>
+    /^\/mn-Mong(?:[/?#]|$)/.test (pathname)
+
+
+export const isUILocaleCode = (value: unknown): value is UILocaleCode =>
+    value === MONGOLIAN_LOCALE.code || isLocaleCode (value)
+
+
+export const uiLocaleFromPath = (pathname: string): UILocaleCode =>
+    isVerticalPreviewPath (pathname) ? MONGOLIAN_LOCALE.code : localeFromPath (pathname) ?? 'ja'
+
+
 export const resolveViewingLocale = (
     pathname: string,
     routeLocale?: unknown,
@@ -40,27 +57,29 @@ export const currentViewingLocale = (): LocaleCode =>
 
 
 export const unlocalisedPath = (pathname: string): string => {
-  const locale = localeFromPath (pathname)
+  const locale = isVerticalPreviewPath (pathname) ? 'mn-Mong' : localeFromPath (pathname)
   return locale == null ? pathname : pathname.slice (locale.length + 1) || '/'
 }
 
 
-export const localiseTo = (to: To, locale: LocaleCode): To => {
+export const localiseTo = (to: To, locale: LocaleCode, viewingPath = ''): To => {
   const pathname = typeof to === 'string' ? to : to.pathname
   if (pathname == null
       || !(pathname.startsWith ('/'))
       || pathname.startsWith ('//')
-      || localeFromPath (pathname) != null)
+      || localeFromPath (pathname) != null
+      || isVerticalPreviewPath (pathname))
     return to
 
-  const localised = `/${ locale }${ pathname }`
+  const prefix = isVerticalPreviewPath (viewingPath) ? 'mn-Mong' : locale
+  const localised = `/${ prefix }${ pathname }`
   return typeof to === 'string' ? localised : { ...to, pathname: localised }
 }
 
 
 export const switchLocalePath = (
     location: { pathname: string; search: string; hash: string },
-    locale: LocaleCode,
+    locale: UILocaleCode,
 ): string =>
     `/${ locale }${ unlocalisedPath (location.pathname) }${ location.search }${ location.hash }`
 
@@ -73,7 +92,8 @@ export const legacyLocalePath = (
     location: { pathname: string; search: string; hash: string },
     isPage: (pathname: string) => boolean = () => false,
 ): string | null => {
-  if (localeFromPath (location.pathname) != null || !isPage (location.pathname))
+  if (localeFromPath (location.pathname) != null
+      || isVerticalPreviewPath (location.pathname) || !isPage (location.pathname))
     return null
   return switchLocalePath (location, automaticallySelectedLocale ())
 }

frontend/src/lib/messages.ts

@@ -1,19 +1,19 @@
 import { translateUIMessage } from '@/lib/i18n'
 
 import type navigation from '@/locales/ja/navigation.json'
-import type { LocaleCode } from '@/lib/locales'
+import type { UILocaleCode } from '@/lib/locales'
 
 export type UIMessageKey = keyof typeof navigation
 
 
 export const uiMessage = (
-    locale: LocaleCode,
+    locale: UILocaleCode,
     key: UIMessageKey,
     values: Record<string, string | number> = { },
 ): string => translateUIMessage (key, 'navigation', locale, values).text
 
 
-export const uiMessageLanguage = (locale: LocaleCode, key: UIMessageKey): 'ja' | 'ain' =>
+export const uiMessageLanguage = (locale: UILocaleCode, key: UIMessageKey): 'ja' | 'ain' =>
     translateUIMessage (key, 'navigation', locale).language === 'ain-Kana'
     ? 'ain'
     : 'ja'

frontend/src/lib/queryKeys.ts

@@ -174,7 +174,6 @@ export const theatresKeys = {
 export const countsKeys = {
     definition: (resource: string, locale: LocaleCode = 'ja') =>
 	['counts', 'definition', resource, locale] as const,
-    candidates: (resource: string, params: string, locale: LocaleCode) =>
+    candidates: (params: string, locale: LocaleCode) => ['counts', 'candidates', locale, params] as const,
-	['counts', 'candidates', resource, locale, params] as const,
     index: (resource: string, params: string, locale: LocaleCode) =>
 	['counts', resource, locale, params] as const }

frontend/src/lib/useLocale.ts

@@ -1,11 +1,12 @@
 import { useCallback } from 'react'
 import { useLocation, useNavigate, useParams } from 'react-router-dom'
 
-import { localiseTo, resolveViewingLocale } from '@/lib/locales'
+import { isVerticalPreviewPath, localiseTo,
+	 resolveViewingLocale, uiLocaleFromPath } from '@/lib/locales'
 
 import type { NavigateFunction, NavigateOptions, To } from 'react-router-dom'
 
-import type { LocaleCode } from '@/lib/locales'
+import type { LocaleCode, UILocaleCode } from '@/lib/locales'
 
 
 export const useLocale = (): LocaleCode => {
@@ -15,13 +16,22 @@ export const useLocale = (): LocaleCode => {
 }
 
 
+export const useUILocale = (): UILocaleCode =>
+    uiLocaleFromPath (useLocation ().pathname)
+
+
 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), options)
+      navigate (localiseTo (to, locale, pathname), options)
-  }, [locale, navigate])
+  }, [locale, navigate, pathname])
 }
+
+
+export const useVerticalPreview = (): boolean =>
+    isVerticalPreviewPath (useLocation ().pathname)

frontend/src/lib/useUITranslation.ts

@@ -3,11 +3,11 @@ import { useTranslation } from 'react-i18next'
 
 import LocalisedText from '@/components/LocalisedText'
 import { translateUIMessage } from '@/lib/i18n'
-import { useLocale } from '@/lib/useLocale'
+import { useUILocale } from '@/lib/useLocale'
 
 
 export const useUITranslation = (namespace = 'common') => {
-  const locale = useLocale ()
+  const locale = useUILocale ()
   const { i18n } = useTranslation (namespace, { lng: locale })
 
   const message = useCallback ((key: string, values?: Record<string, string | number>) => {

frontend/src/lib/utils.ts

@@ -152,7 +152,7 @@ export const msToTime = (ms: number): string => {
 
 
 export const inputClass = (invalid?: boolean, className?: string): string =>
-    cn ('w-full rounded border p-2',
+    cn ('[inline-size:100%] rounded border p-2',
 	(invalid
 	 ? ['border-red-500 bg-red-50 text-red-900',
 	    'placeholder:text-red-300',

frontend/src/main.tsx

@@ -6,7 +6,7 @@ import { I18nextProvider } from 'react-i18next'
 import '@/index.css'
 import App, { preloadPageRoute, resolvePageRoute } from '@/App'
 import { createUII18n } from '@/lib/i18n'
-import { currentViewingLocale } from '@/lib/locales'
+import { currentViewingLocale, uiLocaleFromPath } from '@/lib/locales'
 import { localesKeys } from '@/lib/queryKeys'
 import { applyClientAnimationMode, getClientAnimationMode } from '@/lib/settings'
 
@@ -22,7 +22,7 @@ const client = new QueryClient ({
 
 
 const mount = (serverRendered: boolean) => {
-  const instance = createUII18n (currentViewingLocale ())
+  const instance = createUII18n (uiLocaleFromPath (window.location.pathname))
   const app = (
       <HelmetProvider context={helmetContext}>
 	<QueryClientProvider client={client}>

frontend/src/pages/counts/CountsResourcePage.tsx

@@ -359,7 +359,8 @@ const CountsResourceContent = (
 	      </ul>
 	    </nav>
 	  </SidebarComponent>
-	  <MainArea animateLayout={false} className="flex min-h-0 min-w-0 flex-col p-2">
+	  <MainArea animateLayout={false} verticalContent={false}
+	      className="flex min-h-0 min-w-0 flex-col p-2">
 	    <PageTitle className="mb-1 text-base" lang={title.language}>{title.text}</PageTitle>
 	    <div ref={controlsArea} className="shrink-0"
 		style={{ minHeight: definition == null ? controlsHeight : undefined }}>

frontend/src/pages/materials/MaterialHistoryPage.tsx

@@ -6,7 +6,6 @@ import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
 import PrefetchLink from '@/components/PrefetchLink'
 import FormField from '@/components/common/FormField'
 import PageTitle from '@/components/common/PageTitle'
-import ResourcePickerButton from '@/components/common/ResourcePickerButton'
 import Pagination from '@/components/common/Pagination'
 import MainArea from '@/components/layout/MainArea'
 import PageHead from '@/components/common/PageHead'
@@ -97,19 +96,13 @@ const MaterialHistoryPage: FC = () => {
 	    <div className="space-y-3">
 	      <FormField label={label ('materialId')}>
 		{({ invalid }) => (
-		    <div className="flex items-center gap-2">
 		    <input
 			type="text"
 			value={materialIdInput}
 			aria-label={message ('materialId').text}
 			lang={message ('materialId').language}
 			onChange={e => setMaterialIdInput (e.target.value)}
-			className={inputClass (invalid, 'min-w-0 flex-1')}/>
+			className={inputClass (invalid)}/>)}
-		      <ResourcePickerButton
-			source={{ resource: 'materials', field: 'resource_id' }}
-			values={materialIdInput === '' ? [] : [materialIdInput]}
-			onSelect={values => setMaterialIdInput (values[0] ?? '')}/>
-		    </div>)}
 	      </FormField>
 
 	      <FormField label={label ('tagName')}>

frontend/src/pages/materials/MaterialSyncSuppressionsPage.tsx

@@ -4,7 +4,6 @@ import { useState } from 'react'
 import { useLocale } from '@/lib/useLocale'
 import FormField from '@/components/common/FormField'
 import PageTitle from '@/components/common/PageTitle'
-import ResourcePickerButton from '@/components/common/ResourcePickerButton'
 import MainArea from '@/components/layout/MainArea'
 import { Button } from '@/components/ui/button'
 import { toast } from '@/components/ui/use-toast'
@@ -127,17 +126,11 @@ const MaterialSyncSuppressionsPage: FC = () => {
 
 	      <FormField label={label ('suppressions.driveFileId')}>
 		{({ invalid }) => (
-		    <div className="flex items-center gap-2">
 		    <input
 			type="text"
 			value={driveFileId}
 			onChange={e => setDriveFileId (e.target.value)}
-			className={inputClass (invalid, 'min-w-0 flex-1')}/>
+			className={inputClass (invalid)}/>)}
-		      <ResourcePickerButton
-			source={{ resource: 'materials', field: 'drive_file_id' }}
-			values={driveFileId === '' ? [] : [driveFileId]}
-			onSelect={values => setDriveFileId (values[0] ?? '')}/>
-		    </div>)}
 	      </FormField>
 
 	      <FormField label={label ('suppressions.reason')}>

frontend/src/pages/posts/PostDetailPage.tsx

@@ -107,7 +107,7 @@ const PostDetailPage: FC<Props> = ({ user }) => {
 
 	{post && <TagDetailSidebar post={post} className="hidden md:block"/>}
 
-	<MainArea className="relative">
+	<MainArea className="relative" verticalContent={false}>
 	  {post
 	   ? (
 	      <>

frontend/src/pages/posts/PostListPage.tsx

@@ -146,7 +146,7 @@ const PostListPage: FC = () => {
 				    JSON.stringify (statesToSave))
 	}}/>
 
-	<MainArea>
+	<MainArea className="posts-main-area" verticalContent>
 	  <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="min-w-0">
+      <MainArea className="tags-main-area min-w-0" verticalContent>
 	<PageHead title={message ('title')}/>
 
-	<div className="max-w-xl">
+	<div className="tag-list-filter 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="mt-4 min-w-0 max-w-full">
+	    <div className="tag-list-results mt-4 min-w-0 max-w-full">
-	      <div className="min-w-0 max-w-full overflow-x-auto">
+	      <div className="tag-list-table 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>
+      <MainArea className="wiki-main-area" verticalContent>
 	<PageHead title={{
 	    text: `${displayTitle}${deprecated
 		? message ('labels.deprecatedSuffix').text : ''} Wiki`,

frontend/vitest.config.ts

@@ -1,3 +1,4 @@
+import path from 'node:path'
 import { defineConfig, mergeConfig } from 'vitest/config'
 
 import viteConfig from './vite.config'
@@ -6,7 +7,9 @@ import viteConfig from './vite.config'
 export default mergeConfig (
     viteConfig,
     defineConfig ({
-	test: { environment:  'jsdom',
+	test: { alias: {
+		    '@/config': path.resolve (__dirname, './src/config.sample.ts') },
+		environment:  'jsdom',
 		testTimeout: 30_000,
 		exclude: ['**/node_modules/**', '**/dist/**', 'server.ssr.test.mjs'],
 		setupFiles:   './src/test/setup.ts',