diff --git a/components/modal/ModalContainer.vue b/components/modal/ModalContainer.vue
index 64ea572e..94bcfe92 100644
--- a/components/modal/ModalContainer.vue
+++ b/components/modal/ModalContainer.vue
@@ -5,6 +5,7 @@ import {
   isCommandPanelOpen,
   isConfirmDialogOpen,
   isEditHistoryDialogOpen,
+  isErrorDialogOpen,
   isFavouritedBoostedByDialogOpen,
   isMediaPreviewOpen,
   isPreviewHelpOpen,
@@ -87,6 +88,9 @@ const handleFavouritedBoostedByClose = () => {
     <ModalDialog v-model="isConfirmDialogOpen" py-4 px-8 max-w-125>
       <ModalConfirm v-if="confirmDialogLabel" v-bind="confirmDialogLabel" @choice="handleConfirmChoice" />
     </ModalDialog>
+    <ModalDialog v-model="isErrorDialogOpen" py-4 px-8 max-w-125>
+      <ModalError v-if="errorDialogData" v-bind="errorDialogData" />
+    </ModalDialog>
     <ModalDialog
       v-model="isFavouritedBoostedByDialogOpen"
       max-w-180
diff --git a/components/modal/ModalError.vue b/components/modal/ModalError.vue
new file mode 100644
index 00000000..5a99dec0
--- /dev/null
+++ b/components/modal/ModalError.vue
@@ -0,0 +1,31 @@
+<script setup lang="ts">
+import type { ErrorDialogData } from '~/types'
+
+defineProps<ErrorDialogData>()
+</script>
+
+<template>
+  <div flex="~ col" gap-6>
+    <div font-bold text-lg text-center>
+      {{ title }}
+    </div>
+    <div
+      flex="~ col"
+      gap-1 text-sm
+      pt-1 ps-2 pe-1 pb-2
+      text-red-600 dark:text-red-400
+      border="~ base rounded red-600 dark:red-400"
+    >
+      <ol ps-2 sm:ps-1>
+        <li v-for="(message, i) in messages" :key="i" flex="~ col sm:row" gap-y-1 sm:gap-x-2>
+          {{ message }}
+        </li>
+      </ol>
+    </div>
+    <div flex justify-end gap-2>
+      <button btn-text @click="closeErrorDialog()">
+        {{ close }}
+      </button>
+    </div>
+  </div>
+</template>
diff --git a/components/nav/NavUser.vue b/components/nav/NavUser.vue
index d86de13d..33b85e82 100644
--- a/components/nav/NavUser.vue
+++ b/components/nav/NavUser.vue
@@ -1,3 +1,7 @@
+<script setup>
+const { busy, oauth, singleInstanceServer } = useSignIn()
+</script>
+
 <template>
   <VDropdown v-if="isHydrated && currentUser" sm:hidden>
     <div style="-webkit-touch-callout: none;">
@@ -15,7 +19,24 @@
       <UserSwitcher ref="switcher" @click="hide()" />
     </template>
   </VDropdown>
-  <button v-else btn-solid text-sm px-2 py-1 text-center xl:hidden @click="openSigninDialog()">
-    {{ $t('action.sign_in') }}
-  </button>
+  <template v-else>
+    <button
+      v-if="singleInstanceServer"
+      flex="~ row"
+      gap-x-1 items-center justify-center btn-solid text-sm px-2 py-1 xl:hidden
+      :disabled="busy"
+      @click="oauth()"
+    >
+      <span v-if="busy" aria-hidden="true" block animate animate-spin preserve-3d class="rtl-flip">
+        <span block i-ri:loader-2-fill aria-hidden="true" />
+      </span>
+      <span v-else aria-hidden="true" block i-ri:login-circle-line class="rtl-flip" />
+      <i18n-t keypath="action.sign_in_to">
+        <strong>{{ currentServer }}</strong>
+      </i18n-t>
+    </button>
+    <button v-else btn-solid text-sm px-2 py-1 text-center xl:hidden @click="openSigninDialog()">
+      {{ $t('action.sign_in') }}
+    </button>
+  </template>
 </template>
diff --git a/components/user/UserSignIn.vue b/components/user/UserSignIn.vue
index eccf641c..97621bc2 100644
--- a/components/user/UserSignIn.vue
+++ b/components/user/UserSignIn.vue
@@ -1,66 +1,21 @@
 <script setup lang="ts">
 import Fuse from 'fuse.js'
-import { $fetch } from 'ofetch'
 
-const input = $ref<HTMLInputElement>()
-let server = $ref<string>('')
-let busy = $ref<boolean>(false)
-let error = $ref<boolean>(false)
-let displayError = $ref<boolean>(false)
+const input = ref<HTMLInputElement | undefined>()
 let knownServers = $ref<string[]>([])
 let autocompleteIndex = $ref(0)
 let autocompleteShow = $ref(false)
 
-const users = useUsers()
-const userSettings = useUserSettings()
-
-async function oauth() {
-  if (busy)
-    return
-
-  busy = true
-  error = false
-  displayError = false
-
-  await nextTick()
-
-  if (server)
-    server = server.split('/')[0]
-
-  try {
-    const url = await (globalThis.$fetch as any)(`/api/${server || publicServer.value}/login`, {
-      method: 'POST',
-      body: {
-        force_login: users.value.some(u => u.server === server),
-        origin: location.origin,
-        lang: userSettings.value.language,
-      },
-    })
-    location.href = url
-  }
-  catch (err) {
-    console.error(err)
-
-    displayError = true
-    error = true
-    await nextTick()
-    input?.focus()
-    await nextTick()
-    setTimeout(() => {
-      busy = false
-      error = false
-    }, 512)
-  }
-}
+const { busy, error, displayError, server, oauth } = useSignIn(input)
 
 let fuse = $shallowRef(new Fuse([] as string[]))
 
 const filteredServers = $computed(() => {
-  if (!server)
+  if (!server.value)
     return []
 
-  const results = fuse.search(server, { limit: 6 }).map(result => result.item)
-  if (results[0] === server)
+  const results = fuse.search(server.value, { limit: 6 }).map(result => result.item)
+  if (results[0] === server.value)
     return []
 
   return results
@@ -78,12 +33,12 @@ function isValidUrl(str: string) {
 }
 
 async function handleInput() {
-  const input = server.trim()
+  const input = server.value.trim()
   if (input.startsWith('https://'))
-    server = input.replace('https://', '')
+    server.value = input.replace('https://', '')
 
   if (input.length)
-    displayError = false
+    displayError.value = false
 
   if (
     isValidUrl(`https://${input}`)
@@ -110,7 +65,7 @@ function move(delta: number) {
 
 function onEnter(e: KeyboardEvent) {
   if (autocompleteShow === true && filteredServers[autocompleteIndex]) {
-    server = filteredServers[autocompleteIndex]
+    server.value = filteredServers[autocompleteIndex]
     e.preventDefault()
     autocompleteShow = false
   }
@@ -124,16 +79,16 @@ function escapeAutocomplete(evt: KeyboardEvent) {
 }
 
 function select(index: number) {
-  server = filteredServers[index]
+  server.value = filteredServers[index]
 }
 
 onMounted(async () => {
-  input?.focus()
+  input?.value?.focus()
   knownServers = await (globalThis.$fetch as any)('/api/list-servers')
   fuse = new Fuse(knownServers, { shouldSort: true })
 })
 
-onClickOutside($$(input), () => {
+onClickOutside(input, () => {
   autocompleteShow = false
 })
 </script>
diff --git a/components/user/UserSignInEntry.vue b/components/user/UserSignInEntry.vue
index d6274495..0d78abc2 100644
--- a/components/user/UserSignInEntry.vue
+++ b/components/user/UserSignInEntry.vue
@@ -1,3 +1,7 @@
+<script setup lang="ts">
+const { busy, oauth, singleInstanceServer } = useSignIn()
+</script>
+
 <template>
   <div p8 lg:flex="~ col gap2" hidden>
     <p v-if="isHydrated" text-sm>
@@ -8,7 +12,19 @@
     <p text-sm text-secondary>
       {{ $t('user.sign_in_desc') }}
     </p>
-    <button btn-solid rounded-3 text-center mt-2 select-none @click="openSigninDialog()">
+    <button
+      v-if="singleInstanceServer"
+      flex="~ row" gap-x-2 items-center justify-center btn-solid text-center rounded-3
+      :disabled="busy"
+      @click="oauth()"
+    >
+      <span v-if="busy" aria-hidden="true" block animate animate-spin preserve-3d class="rtl-flip">
+        <span block i-ri:loader-2-fill aria-hidden="true" />
+      </span>
+      <span v-else aria-hidden="true" block i-ri:login-circle-line class="rtl-flip" />
+      {{ $t('action.sign_in') }}
+    </button>
+    <button v-else btn-solid rounded-3 text-center mt-2 select-none @click="openSigninDialog()">
       {{ $t('action.sign_in') }}
     </button>
   </div>
diff --git a/components/user/UserSwitcher.vue b/components/user/UserSwitcher.vue
index e8a766f1..d082abb1 100644
--- a/components/user/UserSwitcher.vue
+++ b/components/user/UserSwitcher.vue
@@ -6,6 +6,7 @@ const emit = defineEmits<{
 }>()
 
 const all = useUsers()
+const { busy, singleInstanceServer, oauth } = useSignIn()
 
 const sorted = computed(() => {
   return [
@@ -21,6 +22,12 @@ const clickUser = (user: UserLogin) => {
   else
     switchUser(user)
 }
+const processSignIn = () => {
+  if (singleInstanceServer)
+    oauth()
+  else
+    openSigninDialog()
+}
 </script>
 
 <template>
@@ -43,7 +50,7 @@ const clickUser = (user: UserLogin) => {
         :text="$t('user.add_existing')"
         icon="i-ri:user-add-line"
         w-full
-        @click="openSigninDialog"
+        @click="processSignIn"
       />
       <CommonDropdownItem
         is="button"
diff --git a/composables/cache.ts b/composables/cache.ts
index e080ce11..b2c917f1 100644
--- a/composables/cache.ts
+++ b/composables/cache.ts
@@ -59,7 +59,8 @@ export function fetchAccountById(id?: string | null): Promise<mastodon.v1.Accoun
 export async function fetchAccountByHandle(acct: string): Promise<mastodon.v1.Account> {
   const server = currentServer.value
   const userId = currentUser.value?.account.id
-  const key = `${server}:${userId}:account:${acct}`
+  const userAcct = acct.endsWith(`@${server}`) ? acct.slice(0, -server.length - 1) : acct
+  const key = `${server}:${userId}:account:${userAcct}`
   const cached = cache.get(key)
   if (cached)
     return cached
@@ -69,9 +70,9 @@ export async function fetchAccountByHandle(acct: string): Promise<mastodon.v1.Ac
     const client = useMastoClient()
     let account: mastodon.v1.Account
     if (!isGotoSocial.value)
-      account = await client.v1.accounts.lookup({ acct })
+      account = await client.v1.accounts.lookup({ acct: userAcct })
     else
-      account = (await client.v1.search({ q: `@${acct}`, type: 'accounts' })).accounts[0]
+      account = (await client.v1.search({ q: `@${userAcct}`, type: 'accounts' })).accounts[0]
 
     if (account.acct && !account.acct.includes('@') && domain)
       account.acct = `${account.acct}@${domain}`
@@ -107,6 +108,7 @@ export function removeCachedStatus(id: string, server = currentServer.value) {
 
 export function cacheAccount(account: mastodon.v1.Account, server = currentServer.value, override?: boolean) {
   const userId = currentUser.value?.account.id
+  const userAcct = account.acct.endsWith(`@${server}`) ? account.acct.slice(0, -server.length - 1) : account.acct
   setCached(`${server}:${userId}:account:${account.id}`, account, override)
-  setCached(`${server}:${userId}:account:${account.acct}`, account, override)
+  setCached(`${server}:${userId}:account:${userAcct}`, account, override)
 }
diff --git a/composables/command.ts b/composables/command.ts
index da2c5a26..c6bc73ab 100644
--- a/composables/command.ts
+++ b/composables/command.ts
@@ -245,6 +245,7 @@ export const provideGlobalCommands = () => {
   const masto = useMasto()
   const colorMode = useColorMode()
   const userSettings = useUserSettings()
+  const { singleInstanceServer, oauth } = useSignIn()
 
   useCommand({
     scope: 'Navigation',
@@ -310,7 +311,10 @@ export const provideGlobalCommands = () => {
     icon: 'i-ri:user-add-line',
 
     onActivate() {
-      openSigninDialog()
+      if (singleInstanceServer)
+        oauth()
+      else
+        openSigninDialog()
     },
   })
   useCommand({
diff --git a/composables/dialog.ts b/composables/dialog.ts
index ac8f1018..9835d9be 100644
--- a/composables/dialog.ts
+++ b/composables/dialog.ts
@@ -1,9 +1,10 @@
 import type { mastodon } from 'masto'
-import type { ConfirmDialogChoice, ConfirmDialogLabel, Draft } from '~/types'
+import type { ConfirmDialogChoice, ConfirmDialogLabel, Draft, ErrorDialogData } from '~/types'
 import { STORAGE_KEY_FIRST_VISIT } from '~/constants'
 
 export const confirmDialogChoice = ref<ConfirmDialogChoice>()
 export const confirmDialogLabel = ref<ConfirmDialogLabel>()
+export const errorDialogData = ref<ErrorDialogData>()
 
 export const mediaPreviewList = ref<mastodon.v1.MediaAttachment[]>([])
 export const mediaPreviewIndex = ref(0)
@@ -22,6 +23,7 @@ export const isEditHistoryDialogOpen = ref(false)
 export const isPreviewHelpOpen = ref(isFirstVisit.value)
 export const isCommandPanelOpen = ref(false)
 export const isConfirmDialogOpen = ref(false)
+export const isErrorDialogOpen = ref(false)
 export const isFavouritedBoostedByDialogOpen = ref(false)
 
 export const lastPublishDialogStatus = ref<mastodon.v1.Status | null>(null)
@@ -101,6 +103,17 @@ export function openMediaPreview(attachments: mastodon.v1.MediaAttachment[], ind
   }, '')
 }
 
+export async function openErrorDialog(data: ErrorDialogData) {
+  errorDialogData.value = data
+  isErrorDialogOpen.value = true
+
+  await until(isErrorDialogOpen).toBe(false)
+}
+
+export function closeErrorDialog() {
+  isErrorDialogOpen.value = false
+}
+
 export function closeMediaPreview() {
   history.back()
 }
diff --git a/composables/sign-in.ts b/composables/sign-in.ts
new file mode 100644
index 00000000..139d792f
--- /dev/null
+++ b/composables/sign-in.ts
@@ -0,0 +1,77 @@
+import type { Ref } from 'vue'
+
+export const useSignIn = (input?: Ref<HTMLInputElement | undefined>) => {
+  const singleInstanceServer = useAppConfig().singleInstanceServer
+  const userSettings = useUserSettings()
+  const users = useUsers()
+  const { t } = useI18n()
+
+  const busy = ref(false)
+  const error = ref(false)
+  const server = ref('')
+  const displayError = ref(false)
+
+  async function oauth() {
+    if (busy.value)
+      return
+
+    busy.value = true
+    error.value = false
+    displayError.value = false
+
+    await nextTick()
+
+    if (!singleInstanceServer && server.value)
+      server.value = server.value.split('/')[0]
+
+    try {
+      let href: string
+      if (singleInstanceServer) {
+        href = await (globalThis.$fetch as any)(`/api/${publicServer.value}/login`, {
+          method: 'POST',
+          body: {
+            force_login: users.value.length > 0,
+            origin: location.origin,
+            lang: userSettings.value.language,
+          },
+        })
+        busy.value = false
+      }
+      else {
+        href = await (globalThis.$fetch as any)(`/api/${server.value || publicServer.value}/login`, {
+          method: 'POST',
+          body: {
+            force_login: users.value.some(u => u.server === server.value),
+            origin: location.origin,
+            lang: userSettings.value.language,
+          },
+        })
+      }
+      location.href = href
+    }
+    catch (err) {
+      if (singleInstanceServer) {
+        console.error(err)
+        busy.value = false
+        await openErrorDialog({
+          title: t('common.error'),
+          messages: [t('error.sign_in_error')],
+          close: t('action.close'),
+        })
+      }
+      else {
+        displayError.value = true
+        error.value = true
+        await nextTick()
+        input?.value?.focus()
+        await nextTick()
+        setTimeout(() => {
+          busy.value = false
+          error.value = false
+        }, 512)
+      }
+    }
+  }
+
+  return { busy, displayError, error, server, singleInstanceServer, oauth }
+}
diff --git a/composables/users.ts b/composables/users.ts
index 062fa401..ab69cf5f 100644
--- a/composables/users.ts
+++ b/composables/users.ts
@@ -263,7 +263,7 @@ export async function signOut() {
   if (!currentUserHandle.value)
     await useRouter().push('/')
 
-  loginTo(masto, currentUser.value)
+  loginTo(masto, currentUser.value || { server: publicServer.value })
 }
 
 export function checkLogin() {
diff --git a/locales/en.json b/locales/en.json
index 20714989..823339f8 100644
--- a/locales/en.json
+++ b/locales/en.json
@@ -69,6 +69,7 @@
     "save": "Save",
     "save_changes": "Save changes",
     "sign_in": "Sign in",
+    "sign_in_to": "Sign in to {0}",
     "switch_account": "Switch account",
     "vote": "Vote"
   },
diff --git a/locales/es.json b/locales/es.json
index 50cf46bb..648afb62 100644
--- a/locales/es.json
+++ b/locales/es.json
@@ -68,6 +68,7 @@
     "save": "Guardar",
     "save_changes": "Guardar cambios",
     "sign_in": "Iniciar sesión",
+    "sign_in_to": "Iniciar sesión en {0}",
     "switch_account": "Cambiar cuenta",
     "vote": "Votar"
   },
diff --git a/middleware/permalink.global.ts b/middleware/1.permalink.global.ts
similarity index 81%
rename from middleware/permalink.global.ts
rename to middleware/1.permalink.global.ts
index 6aa555cf..64c789fa 100644
--- a/middleware/permalink.global.ts
+++ b/middleware/1.permalink.global.ts
@@ -5,16 +5,18 @@ export default defineNuxtRouteMiddleware(async (to, from) => {
   if (!('server' in to.params))
     return
 
+  const server = to.params.server as string || currentServer.value
   const user = currentUser.value
   const masto = useMasto()
   if (!user) {
-    if (from.params.server !== to.params.server)
-      loginTo(masto, { server: to.params.server as string })
+    const fromServer = from.params.server || currentServer.value
+    if (fromServer !== server)
+      loginTo(masto, { server })
     return
   }
 
   // No need to additionally resolve an id if we're already logged in
-  if (user.server === to.params.server)
+  if (user.server === server)
     return
 
   // Tags don't need to be redirected to a local id
@@ -22,7 +24,7 @@ export default defineNuxtRouteMiddleware(async (to, from) => {
     return
 
   // Handle redirecting to new permalink structure for users with old links
-  if (!to.params.server) {
+  if (!useAppConfig().singleInstanceServer && !to.params.server) {
     return {
       ...to,
       params: {
diff --git a/middleware/2.single-instance.global.ts b/middleware/2.single-instance.global.ts
new file mode 100644
index 00000000..4b12cddd
--- /dev/null
+++ b/middleware/2.single-instance.global.ts
@@ -0,0 +1,10 @@
+export default defineNuxtRouteMiddleware(async (to) => {
+  if (process.server || !useAppConfig().singleInstanceServer)
+    return
+
+  if (to.params.server) {
+    const newTo = { ...to }
+    delete newTo.params.server
+    return newTo
+  }
+})
diff --git a/middleware/auth.ts b/middleware/auth.ts
index 05bddb0e..40eafd80 100644
--- a/middleware/auth.ts
+++ b/middleware/auth.ts
@@ -1,6 +1,7 @@
 export default defineNuxtRouteMiddleware((to) => {
   if (process.server)
     return
+
   if (to.path === '/signin/callback')
     return
 
diff --git a/nuxt.config.ts b/nuxt.config.ts
index 79211532..369631a9 100644
--- a/nuxt.config.ts
+++ b/nuxt.config.ts
@@ -96,6 +96,7 @@ export default defineNuxtConfig({
     },
   },
   appConfig: {
+    singleInstanceServer: process.env.SINGLE_INSTANCE_SERVER === 'true',
     storage: {
       driver: process.env.NUXT_STORAGE_DRIVER ?? (isCI ? 'cloudflare' : 'fs'),
     },
diff --git a/pages/[[server]]/@[account]/index.vue b/pages/[[server]]/@[account]/index.vue
index faba9dca..bce15883 100644
--- a/pages/[[server]]/@[account]/index.vue
+++ b/pages/[[server]]/@[account]/index.vue
@@ -1,6 +1,6 @@
 <script setup lang="ts">
 definePageMeta({
-  key: route => `${route.params.server}:${route.params.account}`,
+  key: route => `${route.params.server ?? currentServer.value}:${route.params.account}`,
 })
 
 const params = useRoute().params
diff --git a/pages/[[server]]/list/[list]/index.vue b/pages/[[server]]/list/[list]/index.vue
index d3e74dc7..bdee17b9 100644
--- a/pages/[[server]]/list/[list]/index.vue
+++ b/pages/[[server]]/list/[list]/index.vue
@@ -5,11 +5,11 @@ definePageMeta({
   middleware: 'auth',
 })
 
-const list = $computed(() => useRoute().params.list as string)
-const server = $computed(() => useRoute().params.server as string)
-
-const { t } = useI18n()
 const route = useRoute()
+const { t } = useI18n()
+
+const list = $computed(() => route.params.list as string)
+const server = $computed(() => (route.params.server ?? currentServer.value) as string)
 
 const tabs = $computed<CommonRouteTabOption[]>(() => [
   {
diff --git a/plugins/masto.ts b/plugins/masto.ts
index a980c4b6..4a280f6b 100644
--- a/plugins/masto.ts
+++ b/plugins/masto.ts
@@ -1,5 +1,6 @@
 export default defineNuxtPlugin(() => {
   const { params, query } = useRoute()
+
   publicServer.value = params.server as string || useRuntimeConfig().public.defaultServer
 
   const masto = createMasto()
diff --git a/plugins/social.server.ts b/plugins/social.server.ts
index 1bbf4421..bee5b6c9 100644
--- a/plugins/social.server.ts
+++ b/plugins/social.server.ts
@@ -4,7 +4,7 @@ const BOT_RE = /bot\b|index|spider|facebookexternalhit|crawl|wget|slurp|mediapar
 
 export default defineNuxtPlugin(async (nuxtApp) => {
   const route = useRoute()
-  if (!route.params.server)
+  if (!('server' in route.params))
     return
 
   const userAgent = useRequestHeaders()['user-agent']
diff --git a/types/index.ts b/types/index.ts
index 42e4c0ac..04f1508d 100644
--- a/types/index.ts
+++ b/types/index.ts
@@ -63,6 +63,12 @@ export interface ConfirmDialogLabel {
 }
 export type ConfirmDialogChoice = 'confirm' | 'cancel'
 
+export interface ErrorDialogData {
+  title: string
+  messages: string[]
+  close: string
+}
+
 export interface BuildInfo {
   version: string
   commit: string