diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index 78fd0a9..c8d135d 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -1,8 +1,9 @@
 import { AnimatePresence, LayoutGroup, MotionConfig, motion } from 'framer-motion'
 import { Fragment, useEffect, useMemo, useState } from 'react'
-import { BrowserRouter,
+import { createBrowserRouter,
 	 Navigate,
 	 Route,
+	 RouterProvider,
 	 Routes,
 	 useLocation } from 'react-router-dom'
 
@@ -171,6 +172,41 @@ const App: FC = () => {
       ),
       [animationMode],
   )
+  const router = useMemo (
+      () => createBrowserRouter ([{
+	  path: '*',
+	  element: (
+	      <DialogueProvider>
+		<UnsavedChangesGuardProvider>
+		  <KeyboardShortcutsProvider>
+		  <MotionConfig
+		      reducedMotion={
+			  animationMode === 'normal'
+			  ? 'never'
+			  : animationMode === 'reduced'
+			    ? 'user'
+			    : 'always'
+		      }>
+		    <LayoutWrapper>
+		      <motion.div
+			  layout={animationMode === 'off' ? false : 'position'}
+			  transition={{ layout: appLayoutTransition }}
+			  className="relative flex h-dvh w-full flex-col overflow-y-hidden">
+			<TopNav user={user}/>
+			<RouteTransitionWrapper
+			    animationMode={animationMode}
+			    user={user}
+			    setUser={setUser}/>
+		      </motion.div>
+		    </LayoutWrapper>
+		  </MotionConfig>
+
+		  <Toaster/>
+		  </KeyboardShortcutsProvider>
+		</UnsavedChangesGuardProvider>
+	      </DialogueProvider>) }]),
+      [LayoutWrapper, animationMode, appLayoutTransition, setUser, user],
+  )
 
   useEffect (() => {
     applyClientAppearance ()
@@ -256,38 +292,7 @@ const App: FC = () => {
       <>
 	<RouteBlockerOverlay/>
 	{import.meta.env.DEV && <DevModeWatermark/>}
-
-	<BrowserRouter>
-	  <DialogueProvider>
-	    <UnsavedChangesGuardProvider>
-	      <KeyboardShortcutsProvider>
-	      <MotionConfig
-		  reducedMotion={
-		      animationMode === 'normal'
-		      ? 'never'
-		      : animationMode === 'reduced'
-			? 'user'
-			: 'always'
-		  }>
-		<LayoutWrapper>
-		  <motion.div
-		      layout={animationMode === 'off' ? false : 'position'}
-		      transition={{ layout: appLayoutTransition }}
-		      className="relative flex flex-col h-dvh w-full overflow-y-hidden">
-		    <TopNav user={user}/>
-		    <RouteTransitionWrapper
-			animationMode={animationMode}
-			user={user}
-			setUser={setUser}/>
-		  </motion.div>
-		</LayoutWrapper>
-	      </MotionConfig>
-
-	      <Toaster/>
-	      </KeyboardShortcutsProvider>
-	    </UnsavedChangesGuardProvider>
-	  </DialogueProvider>
-	</BrowserRouter>
+	<RouterProvider router={router}/>
       </>)
 }
 
diff --git a/frontend/src/components/PrefetchLink.tsx b/frontend/src/components/PrefetchLink.tsx
index 3651b5b..be533a4 100644
--- a/frontend/src/components/PrefetchLink.tsx
+++ b/frontend/src/components/PrefetchLink.tsx
@@ -6,7 +6,6 @@ import { createPath, useNavigate } from 'react-router-dom'
 import { useOverlayStore } from '@/components/RouteBlockerOverlay'
 import { prefetchForURL } from '@/lib/prefetchers'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
-import { useUnsavedChangesGuard } from '@/lib/useUnsavedChangesGuard'
 import { cn } from '@/lib/utils'
 
 import type { AnchorHTMLAttributes, MouseEvent, TouchEvent } from 'react'
@@ -36,7 +35,6 @@ export default forwardRef<HTMLAnchorElement, Props> (({
   const navigate = useNavigate ()
   const qc = useQueryClient ()
   const behaviourSettings = useClientBehaviourSettings ()
-  const { confirmDiscardNavigation } = useUnsavedChangesGuard ()
   const linkPreloadMode = behaviourSettings.linkPreload ?? 'intent'
   const path = useMemo (
       () => typeof to === 'string' ? to : createPath (to),
@@ -45,10 +43,6 @@ export default forwardRef<HTMLAnchorElement, Props> (({
   const url = useMemo (() => {
     return (new URL (path, window.location.origin)).toString ()
   }, [path])
-  const nextPathname = useMemo (
-      () => (new URL (path, window.location.origin)).pathname,
-      [path],
-  )
   const setOverlay = useOverlayStore (s => s.setActive)
 
   const doPrefetch = async () => {
@@ -93,13 +87,6 @@ export default forwardRef<HTMLAnchorElement, Props> (({
 
       ev.preventDefault ()
 
-      if (nextPathname !== window.location.pathname)
-	{
-	  const confirmed = await confirmDiscardNavigation ()
-	  if (!(confirmed))
-	    return
-	}
-
       flushSync (() => {
 	setOverlay (true)
       })
diff --git a/frontend/src/components/posts/import/PostImportRowForm.tsx b/frontend/src/components/posts/import/PostImportRowForm.tsx
index 6aa037c..641fe4a 100644
--- a/frontend/src/components/posts/import/PostImportRowForm.tsx
+++ b/frontend/src/components/posts/import/PostImportRowForm.tsx
@@ -10,8 +10,8 @@ import { hasThumbnailBaseValue, hasVideoTag } from '@/lib/postImportRows'
 
 import type { FC } from 'react'
 
-import type { PostImportEditableDraft, PostImportRow } from '@/lib/postImportSession'
 import type { DialogueFormControls } from '@/lib/dialogues/useDialogue'
+import type { PostImportEditableDraft, PostImportRow } from '@/lib/postImportTypes'
 
 type Draft = PostImportEditableDraft
 
diff --git a/frontend/src/components/posts/import/PostImportRowSummary.tsx b/frontend/src/components/posts/import/PostImportRowSummary.tsx
index d2fd4b3..9e1cb76 100644
--- a/frontend/src/components/posts/import/PostImportRowSummary.tsx
+++ b/frontend/src/components/posts/import/PostImportRowSummary.tsx
@@ -4,13 +4,16 @@ import { Button } from '@/components/ui/button'
 import PostImportThumbnailPreview from '@/components/posts/import/PostImportThumbnailPreview'
 import PostImportStatusBadge from '@/components/posts/import/PostImportStatusBadge'
 import { displayPostImportStatus } from '@/components/posts/import/postImportRowStatus'
-import { hasVideoTag } from '@/lib/postImportSession'
-import { canEditReviewRow, canRetryResultRow } from '@/lib/postImportSession'
+import {
+    canEditReviewRow,
+    canRetryResultRow,
+    hasVideoTag,
+} from '@/lib/postImportRows'
 import { cn, originalCreatedAtString } from '@/lib/utils'
 
 import type { FC } from 'react'
 
-import type { PostImportRow } from '@/lib/postImportSession'
+import type { PostImportRow } from '@/lib/postImportTypes'
 
 type Props = {
     row:              PostImportRow
diff --git a/frontend/src/components/posts/import/postImportRowStatus.ts b/frontend/src/components/posts/import/postImportRowStatus.ts
index 0e7ed4a..03b4eb9 100644
--- a/frontend/src/components/posts/import/postImportRowStatus.ts
+++ b/frontend/src/components/posts/import/postImportRowStatus.ts
@@ -1,4 +1,4 @@
-import type { PostImportRow } from '@/lib/postImportSession'
+import type { PostImportRow } from '@/lib/postImportTypes'
 
 export type PostImportDisplayStatus =
     'ready'
diff --git a/frontend/src/lib/postImportSession.ts b/frontend/src/lib/postImportSession.ts
deleted file mode 100644
index d43c394..0000000
--- a/frontend/src/lib/postImportSession.ts
+++ /dev/null
@@ -1,4 +0,0 @@
-export * from '@/lib/postImportTypes'
-export * from '@/lib/postImportStorage'
-export * from '@/lib/postImportSourceValidation'
-export * from '@/lib/postImportRows'
diff --git a/frontend/src/lib/useKeyboardShortcuts.tsx b/frontend/src/lib/useKeyboardShortcuts.tsx
index cc650bd..d6e955f 100644
--- a/frontend/src/lib/useKeyboardShortcuts.tsx
+++ b/frontend/src/lib/useKeyboardShortcuts.tsx
@@ -25,7 +25,6 @@ import {
     getEffectiveKeyBindings,
     setClientKeyboardSettings,
 } from '@/lib/settings'
-import { useUnsavedChangesGuard } from '@/lib/useUnsavedChangesGuard'
 
 import type {
     KeyBinding,
@@ -97,7 +96,6 @@ const focusSearchTarget = (): void => {
 export const KeyboardShortcutsProvider = ({ children }: PropsWithChildren) => {
   const location = useLocation ()
   const navigate = useNavigate ()
-  const { confirmDiscardNavigation } = useUnsavedChangesGuard ()
 
   const [keyboardSettings, setKeyboardSettingsState] =
       useState<ClientKeyboardSettings> (() => getClientKeyboardSettings ())
@@ -149,11 +147,8 @@ export const KeyboardShortcutsProvider = ({ children }: PropsWithChildren) => {
   }, [])
 
   const guardedNavigate = useCallback ((path: string) => {
-    confirmDiscardNavigation ().then (confirmed => {
-      if (confirmed)
-	navigate (path)
-    })
-  }, [confirmDiscardNavigation, navigate])
+    navigate (path)
+  }, [navigate])
 
   const builtinHandlers = useMemo<ShortcutHandlers> (
       () => ({
diff --git a/frontend/src/lib/useUnsavedChangesGuard.tsx b/frontend/src/lib/useUnsavedChangesGuard.tsx
index b866ad4..156901c 100644
--- a/frontend/src/lib/useUnsavedChangesGuard.tsx
+++ b/frontend/src/lib/useUnsavedChangesGuard.tsx
@@ -7,7 +7,7 @@ import {
     useRef,
     useState,
 } from 'react'
-import { useLocation } from 'react-router-dom'
+import { useBlocker, useLocation } from 'react-router-dom'
 
 import { useDialogue } from '@/lib/dialogues/useDialogue'
 
@@ -22,12 +22,11 @@ type UseUnsavedChangesGuardOptions = {
     onDiscard?: () => void | Promise<void> }
 
 type UnsavedChangesGuardContextValue = {
-    hasUnsavedChanges:             boolean
-    registerUnsavedChangesSource:  (
-	source: UnsavedChangesSource | null,
-    ) => void
-    confirmDiscardNavigation:      () => Promise<boolean>
-    allowNextNavigation:           () => void }
+    hasUnsavedChanges:            boolean
+    registerUnsavedChangesSource: (
+        source: UnsavedChangesSource,
+    ) => () => void
+    allowNextNavigation:          () => void }
 
 const UnsavedChangesGuardContext =
     createContext<UnsavedChangesGuardContextValue | null> (null)
@@ -36,41 +35,116 @@ const UnsavedChangesGuardContext =
 export const UnsavedChangesGuardProvider: FC<PropsWithChildren> = ({ children }) => {
   const dialogue = useDialogue ()
   const location = useLocation ()
-  const [source, setSource] = useState<UnsavedChangesSource | null> (null)
+  const sourcesRef = useRef (new Map<symbol, UnsavedChangesSource> ())
   const bypassNextNavigationRef = useRef (false)
+  const [revision, setRevision] = useState (0)
+  const dialogueOpenRef = useRef (false)
 
   const registerUnsavedChangesSource = useCallback ((
-      nextSource: UnsavedChangesSource | null,
-  ) => {
-    setSource (nextSource)
+      source: UnsavedChangesSource,
+  ): (() => void) => {
+    const sourceId = Symbol ('unsaved-changes-source')
+    sourcesRef.current.set (sourceId, source)
+    setRevision (current => current + 1)
+
+    return () => {
+      if (!(sourcesRef.current.delete (sourceId)))
+        return
+
+      setRevision (current => current + 1)
+    }
   }, [])
 
   const allowNextNavigation = useCallback (() => {
     bypassNextNavigationRef.current = true
   }, [])
 
-  const confirmDiscardNavigation = useCallback (async (): Promise<boolean> => {
-    if (!(source?.dirty))
+  const sources = useMemo (
+      () => [...sourcesRef.current.values ()],
+      [revision],
+  )
+  const dirtySources = useMemo (
+      () => sources.filter (source => source.dirty),
+      [sources],
+  )
+  const hasUnsavedChanges = dirtySources.length > 0
+  const blocker = useBlocker (
+      useCallback (
+          () => hasUnsavedChanges && !(bypassNextNavigationRef.current),
+          [hasUnsavedChanges],
+      ),
+  )
+
+  const discardDirtyChanges = useCallback (async (): Promise<boolean> => {
+    if (!(hasUnsavedChanges))
       return true
 
-    const confirmed = await dialogue.confirm ({
-	title: '変更が破棄してページ移動しますか?',
-	confirmText: '変更を破棄して移動',
-	variant: 'danger' })
-    if (!(confirmed))
+    if (dialogueOpenRef.current)
       return false
 
-    bypassNextNavigationRef.current = true
-    await source.discard ()
-    return true
-  }, [dialogue, source])
+    dialogueOpenRef.current = true
+
+    try
+    {
+      const confirmed = await dialogue.confirm ({
+          title: '変更が破棄してページ移動しますか?',
+          confirmText: '変更を破棄して移動',
+          variant: 'danger' })
+      if (!(confirmed))
+        return false
+
+      bypassNextNavigationRef.current = true
+
+      try
+      {
+        for (const source of dirtySources)
+          await source.discard ()
+      }
+      catch
+      {
+        bypassNextNavigationRef.current = false
+        return false
+      }
+
+      return true
+    }
+    finally
+    {
+      dialogueOpenRef.current = false
+    }
+  }, [dialogue, dirtySources, hasUnsavedChanges])
+
+  useEffect (() => {
+    if (blocker.state !== 'blocked')
+      return
+
+    let active = true
+
+    void (async () => {
+      const confirmed = await discardDirtyChanges ()
+      if (!(active))
+        return
+
+      if (confirmed)
+        {
+          blocker.proceed ()
+          return
+        }
+
+      blocker.reset ()
+    }) ()
+
+    return () => {
+      active = false
+    }
+  }, [blocker, discardDirtyChanges])
 
   useEffect (() => {
     bypassNextNavigationRef.current = false
   }, [location.hash, location.pathname, location.search])
 
   useEffect (() => {
-    if (!(source?.dirty))
+    if (!(hasUnsavedChanges))
       return
 
     const handleBeforeUnload = (event: BeforeUnloadEvent) => {
@@ -82,23 +156,21 @@ export const UnsavedChangesGuardProvider: FC<PropsWithChildren> = ({ children })
     return () => {
       window.removeEventListener ('beforeunload', handleBeforeUnload)
     }
-  }, [source?.dirty])
+  }, [hasUnsavedChanges])
 
   const value = useMemo<UnsavedChangesGuardContextValue> (() => ({
-      hasUnsavedChanges: source?.dirty === true,
+      hasUnsavedChanges,
       registerUnsavedChangesSource,
-      confirmDiscardNavigation,
       allowNextNavigation,
   }), [
       allowNextNavigation,
-      confirmDiscardNavigation,
+      hasUnsavedChanges,
       registerUnsavedChangesSource,
-      source?.dirty,
   ])
 
   return (
       <UnsavedChangesGuardContext.Provider value={value}>
-	{children}
+        {children}
       </UnsavedChangesGuardContext.Provider>)
 }
 
@@ -115,13 +187,9 @@ export const useUnsavedChangesGuard = (
     if (options == null)
       return
 
-    context.registerUnsavedChangesSource ({
-	dirty: options.dirty,
-	discard: options.onDiscard ?? (() => undefined) })
-
-    return () => {
-      context.registerUnsavedChangesSource (null)
-    }
+    return context.registerUnsavedChangesSource ({
+        dirty: options.dirty,
+        discard: options.onDiscard ?? (() => undefined) })
   }, [context, options?.dirty, options?.onDiscard])
 
   return context
diff --git a/frontend/src/pages/users/SettingPage.tsx b/frontend/src/pages/users/SettingPage.tsx
index 5619a6e..1ece04a 100644
--- a/frontend/src/pages/users/SettingPage.tsx
+++ b/frontend/src/pages/users/SettingPage.tsx
@@ -1197,13 +1197,9 @@ const SettingPage: FC<Props> = ({ user, setUser }) => {
   }, [hasUnsavedThemeChanges, savedThemeSlots])
 
   useEffect (() => {
-    registerUnsavedChangesSource ({
-	dirty: hasPageUnsavedChanges,
-	discard: discardAllDirtyChanges })
-
-    return () => {
-      registerUnsavedChangesSource (null)
-    }
+    return registerUnsavedChangesSource ({
+        dirty: hasPageUnsavedChanges,
+        discard: discardAllDirtyChanges })
   }, [discardAllDirtyChanges, hasPageUnsavedChanges, registerUnsavedChangesSource])
 
   useKeyboardShortcuts ({