diff --git a/frontend/src/lib/help.test.ts b/frontend/src/lib/help.test.ts
index a4b246b..79ee9b0 100644
--- a/frontend/src/lib/help.test.ts
+++ b/frontend/src/lib/help.test.ts
@@ -4,6 +4,18 @@ import { createHelpFixture } from '@/test/helpFixtures'
 
 
 describe ('Help file catalogue', () => {
+  it.each ([['Éclair', 'eclair'], ['home', 'HOME'], ['e\u0301clair', 'Éclair']]) (
+      'compares title %s and %s equally at primary strength', (a, b) => {
+	const { api } = createHelpFixture ()
+	expect (api.compareHelpTitles (a, b)).toBe (0)
+      })
+
+  it ('orders distinct Latin titles in both directions', () => {
+    const { api } = createHelpFixture ()
+    expect (api.compareHelpTitles ('Apple', 'Zebra')).toBeLessThan (0)
+    expect (api.compareHelpTitles ('Zebra', 'Apple')).toBeGreaterThan (0)
+  })
+
   it.each ([['ほーむ', 'ホーム'], ['ホーム', 'ほーむ'], ['ﾎｰﾑ', 'ホーム'],
       ['ＡＢＣ', 'abc'], ['ｶﾞｲﾄﾞ', 'がいど']]) (
       'normalises search text %s and %s identically', (query, text) => {
diff --git a/frontend/src/lib/help.ts b/frontend/src/lib/help.ts
index de61501..36b6207 100644
--- a/frontend/src/lib/help.ts
+++ b/frontend/src/lib/help.ts
@@ -33,6 +33,14 @@ export type HelpDiff = {
 
 export type HelpEditionIdentifier = { date: string; revision: number | null }
 
+// Fix the locale and primary strength; ICU versions still differ from MySQL UCA 9.0.
+const helpTitleCollator = new Intl.Collator ('en', {
+    usage: 'sort', sensitivity: 'base', ignorePunctuation: false, numeric: false })
+
+
+export const compareHelpTitles = (a: string, b: string): number =>
+    helpTitleCollator.compare (a, b)
+
 
 export const normaliseHelpSearchText = (value: string): string =>
     value.normalize ('NFKC').toLowerCase ().replace (/[ァ-ヶヽヾ]/g,
diff --git a/frontend/src/pages/help/HelpListPage.test.tsx b/frontend/src/pages/help/HelpListPage.test.tsx
index 385ad79..218ccd1 100644
--- a/frontend/src/pages/help/HelpListPage.test.tsx
+++ b/frontend/src/pages/help/HelpListPage.test.tsx
@@ -90,6 +90,20 @@ describe ('Help search', () => {
       })
 
   // ai_ci equality is documented by MySQL; these are not captured DB sort results.
+  it.each (['asc', 'desc']) ('orders different titles before identifiers in order %s',
+      async direction => {
+	helpFixture.assets.search.default.ja = [
+	    { identifier: 'alpha', edition: '2026-10-02', title: 'Zebra', body: '' },
+	    { identifier: 'beta', edition: '2026-10-02', title: 'Apple', body: '' }]
+	const { container } = renderWithProviders (<HelpListPage/>, {
+	    route: `/help?order=title:${ direction }` })
+	await screen.findByText ('2 件')
+	const expected = direction === 'asc'
+	    ? ['/help/beta', '/help/alpha'] : ['/help/alpha', '/help/beta']
+	expect (Array.from (container.querySelectorAll ('tbody a'), link =>
+	    link.getAttribute ('href'))).toEqual (expected)
+      })
+
   it.each (['asc', 'desc']) ('uses identifier ties for MySQL ai_ci title order %s',
       async direction => {
 	helpFixture.assets.search.default.ja = [
diff --git a/frontend/src/pages/help/HelpListPage.tsx b/frontend/src/pages/help/HelpListPage.tsx
index 0b4976d..bf0341c 100644
--- a/frontend/src/pages/help/HelpListPage.tsx
+++ b/frontend/src/pages/help/HelpListPage.tsx
@@ -11,6 +11,7 @@ import Pagination from '@/components/common/Pagination'
 import MainArea from '@/components/layout/MainArea'
 import { SITE_TITLE } from '@/config'
 import { compareHelpEditions,
+	 compareHelpTitles,
 	 getHelpSearchEntries,
 	 helpEditionDate,
 	 normaliseHelpSearchText } from '@/lib/help'
@@ -70,7 +71,7 @@ const HelpSearchPage: FC = () => {
 		|| normaliseHelpSearchText (entry.body).includes (textQuery))))
 	.sort ((a, b) => {
 	  const comparison = field === 'title'
-	      ? a.title.localeCompare (b.title, 'ja')
+	      ? compareHelpTitles (a.title, b.title)
 	      : compareHelpEditions (a.edition, b.edition)
 
 	  return (direction === 'asc' ? comparison : -comparison)
diff --git a/frontend/src/pages/wiki/WikiDetailPage.test.tsx b/frontend/src/pages/wiki/WikiDetailPage.test.tsx
index fac93da..84268c9 100644
--- a/frontend/src/pages/wiki/WikiDetailPage.test.tsx
+++ b/frontend/src/pages/wiki/WikiDetailPage.test.tsx
@@ -1,9 +1,10 @@
-import { act, fireEvent, screen, waitFor } from '@testing-library/react'
-import { Route, Routes } from 'react-router-dom'
+import { act, fireEvent, screen, waitFor, within } from '@testing-library/react'
+import { Route, Routes, useLocation } from 'react-router-dom'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { apiPost } from '@/lib/api'
 import { getHelpTitleIndex } from '@/lib/help'
+import { tagsKeys, wikiKeys } from '@/lib/queryKeys'
 import WikiDetailPage from '@/pages/wiki/WikiDetailPage'
 import WikiNewPage from '@/pages/wiki/WikiNewPage'
 import { buildTag, buildUser, buildWikiPage } from '@/test/factories'
@@ -27,7 +28,8 @@ vi.mock ('@/lib/wiki', () => wikiApi)
 vi.mock ('@/lib/tags', () => tagsApi)
 vi.mock ('@/lib/posts', () => postsApi)
 vi.mock ('@/lib/help', () => ({ getHelpTitleIndex: vi.fn () }))
-vi.mock ('@/lib/api', () => ({ apiPost: vi.fn () }))
+vi.mock ('@/lib/api', async importOriginal => ({
+    ...await importOriginal<typeof import ('@/lib/api')> (), apiPost: vi.fn () }))
 vi.mock ('@/components/ui/use-toast', () => ({ toast: vi.fn () }))
 vi.mock ('react-markdown-editor-lite', () => ({
     default: ({ value, onChange }: {
@@ -36,6 +38,13 @@ vi.mock ('react-markdown-editor-lite', () => ({
 	    <textarea aria-label="本文エディタ" value={value}
 		onChange={event => onChange ({ text: event.target.value })}/>) }))
 
+
+const Location = () => {
+  const location = useLocation ()
+  return <output data-testid="location">{location.pathname}{location.search}</output>
+}
+
+
 describe ('WikiDetailPage', () => {
   beforeEach (() => {
     wikiApi.fetchWikiPageByTitle.mockReset ().mockResolvedValue (null)
@@ -70,25 +79,64 @@ describe ('WikiDetailPage', () => {
 	resourceType: 'tag_description' })
     tagsApi.fetchTagByName.mockResolvedValue (buildTag ({ name: page.title, hasWiki: false }))
     vi.mocked (apiPost).mockResolvedValueOnce (page)
-    renderWithProviders (
-	<Routes>
-	  <Route path="/wiki/new" element={<WikiNewPage user={buildUser ({ role: 'member' })}/>}/>
-	  <Route path="/wiki/:title" element={<WikiDetailPage/>}/>
-	</Routes>, { route: `/wiki/${ encodeURIComponent (page.title) }` })
+    const path = `/wiki/${ encodeURIComponent (page.title) }`
+    const { container, queryClient } = renderWithProviders (
+	<>
+	  <Location/>
+	  <Routes>
+	    <Route path="/wiki/new" element={<WikiNewPage user={buildUser ({ role: 'member' })}/>}/>
+	    <Route path="/wiki/:title" element={<WikiDetailPage/>}/>
+	  </Routes>
+	</>, { route: path })
     fireEvent.click (await screen.findByRole ('link', { name: '新規作成してください' }))
     await screen.findByRole ('heading', { name: '新規 Wiki ページ' })
+    expect (queryClient.getQueryData (wikiKeys.show (page.title, { }))).toBeNull ()
+    queryClient.setQueryData (wikiKeys.index ({ }), [])
     wikiApi.fetchWikiPageByTitle.mockResolvedValue (page)
+    wikiApi.fetchWikiPages.mockResolvedValue ([page])
+    tagsApi.fetchTagByName.mockResolvedValue (buildTag ({ name: page.title, hasWiki: true }))
     expect (screen.getAllByRole ('textbox')[0]).toHaveValue (page.title)
     fireEvent.change (screen.getByRole ('textbox', { name: '本文エディタ' }), {
 	target: { value: page.body } })
     fireEvent.click (screen.getByRole ('button', { name: '追加' }))
-    expect (await screen.findByText (page.body)).toBeInTheDocument ()
+    await screen.findByRole ('heading', { name: page.title })
+    expect (screen.getByTestId ('location')).toHaveTextContent (path)
+    expect (screen.queryByRole ('textbox', { name: '本文エディタ' })).not.toBeInTheDocument ()
+    expect (within (container.querySelector ('article')!).getByText (page.body))
+	.toBeInTheDocument ()
     const form = vi.mocked (apiPost).mock.calls[0][1] as FormData
     expect (form.get ('title')).toBe (page.title)
     expect (form.get ('body')).toBe (page.body)
     expect (apiPost).toHaveBeenCalledWith ('/wiki', form,
 	{ headers: { 'Content-Type': 'multipart/form-data' } })
     expect (screen.queryByText ('404')).not.toBeInTheDocument ()
+    expect (queryClient.getQueryData (wikiKeys.show (page.title, { }))).toEqual (page)
+    await waitFor (() => expect (queryClient.getQueryData (wikiKeys.index ({ })))
+	.toEqual ([page]))
+    await waitFor (() => expect (queryClient.getQueryData (tagsKeys.show (page.title)))
+	.toMatchObject ({ hasWiki: true }))
+    expect (getHelpTitleIndex).toHaveBeenCalledTimes (1)
+  })
+
+  it ('keeps failed saves on the form without changing cached Wiki or tag state', async () => {
+    const title = '既存タグ'
+    const tag = buildTag ({ name: title, hasWiki: false })
+    const path = `/wiki/new?title=${ encodeURIComponent (title) }`
+    vi.mocked (apiPost).mockRejectedValueOnce (new Error ('save failed'))
+    const { queryClient } = renderWithProviders (
+	<><Location/><WikiNewPage user={buildUser ({ role: 'member' })}/></>, { route: path })
+    queryClient.setQueryData (wikiKeys.show (title, { }), null)
+    queryClient.setQueryData (wikiKeys.index ({ }), [])
+    queryClient.setQueryData (tagsKeys.show (title), tag)
+    fireEvent.change (screen.getByRole ('textbox', { name: '本文エディタ' }), {
+	target: { value: '保存しない本文' } })
+    await act (async () => fireEvent.click (screen.getByRole ('button', { name: '追加' })))
+    expect (apiPost).toHaveBeenCalledTimes (1)
+    expect (screen.getByTestId ('location')).toHaveTextContent (path)
+    expect (screen.getByRole ('heading', { name: '新規 Wiki ページ' })).toBeInTheDocument ()
+    expect (queryClient.getQueryData (wikiKeys.show (title, { }))).toBeNull ()
+    expect (queryClient.getQueryData (tagsKeys.show (title))).toEqual (tag)
+    expect (queryClient.getQueryState (wikiKeys.index ({ }))?.isInvalidated).toBe (false)
   })
 
   it ('shows NotFound when neither a tag nor a Help title exists', async () => {
diff --git a/frontend/src/pages/wiki/WikiNewPage.tsx b/frontend/src/pages/wiki/WikiNewPage.tsx
index b7878e4..60ee6a9 100644
--- a/frontend/src/pages/wiki/WikiNewPage.tsx
+++ b/frontend/src/pages/wiki/WikiNewPage.tsx
@@ -1,10 +1,10 @@
-import type { FC } from 'react'
-
+import { useQueryClient } from '@tanstack/react-query'
 import MarkdownIt from 'markdown-it'
 import { useState } from 'react'
 import { Helmet } from 'react-helmet-async'
 import MdEditor from 'react-markdown-editor-lite'
 import { useLocation, useNavigate } from 'react-router-dom'
+import 'react-markdown-editor-lite/lib/index.css'
 
 import FieldError from '@/components/common/FieldError'
 import FormField from '@/components/common/FormField'
@@ -12,12 +12,13 @@ import MainArea from '@/components/layout/MainArea'
 import { toast } from '@/components/ui/use-toast'
 import { SITE_TITLE } from '@/config'
 import { apiPost } from '@/lib/api'
+import { tagsKeys, wikiKeys } from '@/lib/queryKeys'
 import { canEditContent } from '@/lib/users'
 import { inputClass } from '@/lib/utils'
 import { useValidationErrors } from '@/lib/useValidationErrors'
 import Forbidden from '@/pages/Forbidden'
 
-import 'react-markdown-editor-lite/lib/index.css'
+import type { FC } from 'react'
 
 import type { User, WikiPage } from '@/types'
 
@@ -38,6 +39,7 @@ const WikiNewPage: FC<Props> = ({ user }) => {
 
   const location = useLocation ()
   const navigate = useNavigate ()
+  const qc = useQueryClient ()
 
   const query = new URLSearchParams (location.search)
   const titleQuery = query.get ('title') ?? ''
@@ -58,6 +60,11 @@ const WikiNewPage: FC<Props> = ({ user }) => {
     {
       const data = await apiPost<WikiPage> ('/wiki', formData,
 				  { headers: { 'Content-Type': 'multipart/form-data' } })
+      await qc.cancelQueries ({ queryKey: wikiKeys.root })
+      qc.setQueryData (wikiKeys.show (data.title, { }), data)
+      await Promise.all ([
+	  qc.invalidateQueries ({ queryKey: wikiKeys.root }),
+	  qc.invalidateQueries ({ queryKey: tagsKeys.root })])
       toast ({ title: '投稿成功!' })
       navigate (`/wiki/${ encodeURIComponent (data.title) }`)
     }