diff --git a/frontend/src/views/auth/LinuxDoCallbackView.vue b/frontend/src/views/auth/LinuxDoCallbackView.vue
index 735c6582..a775075d 100644
--- a/frontend/src/views/auth/LinuxDoCallbackView.vue
+++ b/frontend/src/views/auth/LinuxDoCallbackView.vue
@@ -249,6 +249,7 @@ import {
   login2FA,
   persistOAuthTokenContext,
   type OAuthAdoptionDecision,
+  type OAuthTokenResponse,
   type PendingOAuthExchangeResponse
 } from '@/api/auth'
 
@@ -278,6 +279,7 @@ const pendingAccountAction = ref<'none' | 'create_account' | 'bind_login'>('none
 const pendingAccountEmail = ref('')
 const bindLoginEmail = ref('')
 const bindLoginPassword = ref('')
+const legacyPendingOAuthToken = ref('')
 const accountActionError = ref('')
 const canReturnToCreateAccount = ref(false)
 const bindSuccessMessage = t('profile.authBindings.bindSuccess')
@@ -315,6 +317,30 @@ function parseFragmentParams(): URLSearchParams {
   return new URLSearchParams(hash)
 }
 
+function readLegacyFragmentLogin(params: URLSearchParams): OAuthTokenResponse | null {
+  const accessToken = params.get('access_token')?.trim() || ''
+  if (!accessToken) {
+    return null
+  }
+
+  const completion: OAuthTokenResponse = {
+    access_token: accessToken
+  }
+  const refreshToken = params.get('refresh_token')?.trim() || ''
+  if (refreshToken) {
+    completion.refresh_token = refreshToken
+  }
+  const expiresIn = Number.parseInt(params.get('expires_in')?.trim() || '', 10)
+  if (Number.isFinite(expiresIn) && expiresIn > 0) {
+    completion.expires_in = expiresIn
+  }
+  const tokenType = params.get('token_type')?.trim() || ''
+  if (tokenType) {
+    completion.token_type = tokenType
+  }
+  return completion
+}
+
 function sanitizeRedirectPath(path: string | null | undefined): string {
   if (!path) return '/dashboard'
   if (!path.startsWith('/')) return '/dashboard'
@@ -521,10 +547,18 @@ async function handleSubmitInvitation() {
 
   isSubmitting.value = true
   try {
-    const tokenData = await completeLinuxDoOAuthRegistration(
-      invitationCode.value.trim(),
-      currentAdoptionDecision()
-    )
+    const tokenData = legacyPendingOAuthToken.value
+      ? (
+          await apiClient.post<OAuthTokenResponse>('/auth/oauth/linuxdo/complete-registration', {
+            pending_oauth_token: legacyPendingOAuthToken.value,
+            invitation_code: invitationCode.value.trim(),
+            ...serializeAdoptionDecision(currentAdoptionDecision())
+          })
+        ).data
+      : await completeLinuxDoOAuthRegistration(
+          invitationCode.value.trim(),
+          currentAdoptionDecision()
+        )
     persistOAuthTokenContext(tokenData)
     await authStore.setToken(tokenData.access_token)
     appStore.showSuccess(t('auth.loginSuccess'))
@@ -621,51 +655,72 @@ async function handleSubmitTotpChallenge() {
 
 onMounted(async () => {
   const params = parseFragmentParams()
+  const legacyLogin = readLegacyFragmentLogin(params)
+  const legacyPendingToken = params.get('pending_oauth_token')?.trim() || ''
   const error = params.get('error')
   const errorDesc = params.get('error_description') || params.get('error_message') || ''
-
-  if (error) {
-    errorMessage.value = errorDesc || error
-    appStore.showError(errorMessage.value)
-    isProcessing.value = false
-    return
-  }
+  const redirect = sanitizeRedirectPath(
+    params.get('redirect') || (route.query.redirect as string | undefined) || '/dashboard'
+  )
 
   try {
+    if (legacyLogin) {
+      persistOAuthTokenContext(legacyLogin)
+      await authStore.setToken(legacyLogin.access_token)
+      appStore.showSuccess(t('auth.loginSuccess'))
+      await router.replace(redirect)
+      return
+    }
+
+    if (error === 'invitation_required' && legacyPendingToken) {
+      legacyPendingOAuthToken.value = legacyPendingToken
+      redirectTo.value = redirect
+      needsInvitation.value = true
+      isProcessing.value = false
+      return
+    }
+
+    if (error) {
+      errorMessage.value = errorDesc || error
+      appStore.showError(errorMessage.value)
+      isProcessing.value = false
+      return
+    }
+
     const completion = await exchangePendingOAuthCompletion()
-    const redirect = sanitizeRedirectPath(
+    const completionRedirect = sanitizeRedirectPath(
       completion.redirect || (route.query.redirect as string | undefined) || '/dashboard'
     )
     applyAdoptionSuggestionState(completion)
-    redirectTo.value = redirect
+    redirectTo.value = completionRedirect
 
     if (completion.error === 'invitation_required') {
       needsInvitation.value = true
       isProcessing.value = false
-      persistPendingAuthSession(redirect)
+      persistPendingAuthSession(completionRedirect)
       return
     }
 
     if (applyTotpChallenge(completion as LinuxDoPendingActionResponse)) {
-      persistPendingAuthSession(redirect)
+      persistPendingAuthSession(completionRedirect)
       return
     }
 
     applyPendingAccountAction(completion as LinuxDoPendingActionResponse)
     if (pendingAccountAction.value !== 'none') {
       isProcessing.value = false
-      persistPendingAuthSession(redirect)
+      persistPendingAuthSession(completionRedirect)
       return
     }
 
     if (adoptionRequired.value && hasSuggestedProfile(completion)) {
       needsAdoptionConfirmation.value = true
       isProcessing.value = false
-      persistPendingAuthSession(redirect)
+      persistPendingAuthSession(completionRedirect)
       return
     }
 
-    await finalizeCompletion(completion, redirect)
+    await finalizeCompletion(completion, completionRedirect)
   } catch (e: unknown) {
     clearPendingAuthSession()
     errorMessage.value = getRequestErrorMessage(e, t('auth.loginFailed'))
diff --git a/frontend/src/views/auth/OidcCallbackView.vue b/frontend/src/views/auth/OidcCallbackView.vue
index 019cab54..e15e752f 100644
--- a/frontend/src/views/auth/OidcCallbackView.vue
+++ b/frontend/src/views/auth/OidcCallbackView.vue
@@ -259,6 +259,7 @@ import {
   login2FA,
   persistOAuthTokenContext,
   type OAuthAdoptionDecision,
+  type OAuthTokenResponse,
   type PendingOAuthExchangeResponse
 } from '@/api/auth'
 
@@ -287,6 +288,7 @@ const pendingAccountAction = ref<'none' | 'create_account' | 'bind_login'>('none
 const pendingAccountEmail = ref('')
 const bindLoginEmail = ref('')
 const bindLoginPassword = ref('')
+const legacyPendingOAuthToken = ref('')
 const accountActionError = ref('')
 const canReturnToCreateAccount = ref(false)
 const bindSuccessMessage = t('profile.authBindings.bindSuccess')
@@ -331,6 +333,30 @@ function parseFragmentParams(): URLSearchParams {
   return new URLSearchParams(hash)
 }
 
+function readLegacyFragmentLogin(params: URLSearchParams): OAuthTokenResponse | null {
+  const accessToken = params.get('access_token')?.trim() || ''
+  if (!accessToken) {
+    return null
+  }
+
+  const completion: OAuthTokenResponse = {
+    access_token: accessToken
+  }
+  const refreshToken = params.get('refresh_token')?.trim() || ''
+  if (refreshToken) {
+    completion.refresh_token = refreshToken
+  }
+  const expiresIn = Number.parseInt(params.get('expires_in')?.trim() || '', 10)
+  if (Number.isFinite(expiresIn) && expiresIn > 0) {
+    completion.expires_in = expiresIn
+  }
+  const tokenType = params.get('token_type')?.trim() || ''
+  if (tokenType) {
+    completion.token_type = tokenType
+  }
+  return completion
+}
+
 function sanitizeRedirectPath(path: string | null | undefined): string {
   if (!path) return '/dashboard'
   if (!path.startsWith('/')) return '/dashboard'
@@ -565,10 +591,18 @@ async function handleSubmitInvitation() {
 
   isSubmitting.value = true
   try {
-    const tokenData = await completeOIDCOAuthRegistration(
-      invitationCode.value.trim(),
-      currentAdoptionDecision()
-    )
+    const tokenData = legacyPendingOAuthToken.value
+      ? (
+          await apiClient.post<OAuthTokenResponse>('/auth/oauth/oidc/complete-registration', {
+            pending_oauth_token: legacyPendingOAuthToken.value,
+            invitation_code: invitationCode.value.trim(),
+            ...serializeAdoptionDecision(currentAdoptionDecision())
+          })
+        ).data
+      : await completeOIDCOAuthRegistration(
+          invitationCode.value.trim(),
+          currentAdoptionDecision()
+        )
     persistOAuthTokenContext(tokenData)
     await authStore.setToken(tokenData.access_token)
     appStore.showSuccess(t('auth.loginSuccess'))
@@ -667,51 +701,72 @@ onMounted(async () => {
   void loadProviderName()
 
   const params = parseFragmentParams()
+  const legacyLogin = readLegacyFragmentLogin(params)
+  const legacyPendingToken = params.get('pending_oauth_token')?.trim() || ''
   const error = params.get('error')
   const errorDesc = params.get('error_description') || params.get('error_message') || ''
-
-  if (error) {
-    errorMessage.value = errorDesc || error
-    appStore.showError(errorMessage.value)
-    isProcessing.value = false
-    return
-  }
+  const redirect = sanitizeRedirectPath(
+    params.get('redirect') || (route.query.redirect as string | undefined) || '/dashboard'
+  )
 
   try {
+    if (legacyLogin) {
+      persistOAuthTokenContext(legacyLogin)
+      await authStore.setToken(legacyLogin.access_token)
+      appStore.showSuccess(t('auth.loginSuccess'))
+      await router.replace(redirect)
+      return
+    }
+
+    if (error === 'invitation_required' && legacyPendingToken) {
+      legacyPendingOAuthToken.value = legacyPendingToken
+      redirectTo.value = redirect
+      needsInvitation.value = true
+      isProcessing.value = false
+      return
+    }
+
+    if (error) {
+      errorMessage.value = errorDesc || error
+      appStore.showError(errorMessage.value)
+      isProcessing.value = false
+      return
+    }
+
     const completion = await exchangePendingOAuthCompletion() as PendingOidcCompletion
-    const redirect = sanitizeRedirectPath(
+    const completionRedirect = sanitizeRedirectPath(
       completion.redirect || (route.query.redirect as string | undefined) || '/dashboard'
     )
     applyAdoptionSuggestionState(completion)
-    redirectTo.value = redirect
+    redirectTo.value = completionRedirect
 
     if (completion.error === 'invitation_required') {
       needsInvitation.value = true
       isProcessing.value = false
-      persistPendingAuthSession(redirect)
+      persistPendingAuthSession(completionRedirect)
       return
     }
 
     if (applyTotpChallenge(completion)) {
-      persistPendingAuthSession(redirect)
+      persistPendingAuthSession(completionRedirect)
       return
     }
 
     applyPendingAccountAction(completion)
     if (pendingAccountAction.value !== 'none') {
       isProcessing.value = false
-      persistPendingAuthSession(redirect)
+      persistPendingAuthSession(completionRedirect)
       return
     }
 
     if (adoptionRequired.value && hasSuggestedProfile(completion)) {
       needsAdoptionConfirmation.value = true
       isProcessing.value = false
-      persistPendingAuthSession(redirect)
+      persistPendingAuthSession(completionRedirect)
       return
     }
 
-    await finalizeCompletion(completion, redirect)
+    await finalizeCompletion(completion, completionRedirect)
   } catch (e: unknown) {
     clearPendingAuthSession()
     errorMessage.value = getRequestErrorMessage(e, t('auth.loginFailed'))
diff --git a/frontend/src/views/auth/__tests__/LinuxDoCallbackView.spec.ts b/frontend/src/views/auth/__tests__/LinuxDoCallbackView.spec.ts
index f612681a..0daf5d9a 100644
--- a/frontend/src/views/auth/__tests__/LinuxDoCallbackView.spec.ts
+++ b/frontend/src/views/auth/__tests__/LinuxDoCallbackView.spec.ts
@@ -86,6 +86,74 @@ describe('LinuxDoCallbackView', () => {
       turnstile_enabled: false,
       turnstile_site_key: ''
     })
+    window.location.hash = ''
+    localStorage.clear()
+  })
+
+  it('accepts the legacy fragment token success callback without pending-session exchange', async () => {
+    window.location.hash =
+      '#access_token=legacy-access-token&refresh_token=legacy-refresh-token&expires_in=3600&token_type=Bearer&redirect=%2Flegacy-dashboard'
+    setToken.mockResolvedValue({})
+
+    mount(LinuxDoCallbackView, {
+      global: {
+        stubs: {
+          AuthLayout: { template: '<div><slot /></div>' },
+          Icon: true,
+          RouterLink: { template: '<a><slot /></a>' },
+          transition: false
+        }
+      }
+    })
+
+    await flushPromises()
+
+    expect(exchangePendingOAuthCompletion).not.toHaveBeenCalled()
+    expect(setToken).toHaveBeenCalledWith('legacy-access-token')
+    expect(localStorage.getItem('refresh_token')).toBe('legacy-refresh-token')
+    expect(localStorage.getItem('token_expires_at')).not.toBeNull()
+    expect(showSuccess).toHaveBeenCalledWith('auth.loginSuccess')
+    expect(replace).toHaveBeenCalledWith('/legacy-dashboard')
+  })
+
+  it('accepts the legacy pending oauth invitation fragment without pending-session exchange', async () => {
+    window.location.hash = '#error=invitation_required&pending_oauth_token=legacy-pending-token&redirect=%2Flegacy-invite'
+    apiClientPost.mockResolvedValue({
+      data: {
+        access_token: 'legacy-access-token',
+        refresh_token: 'legacy-refresh-token',
+        expires_in: 3600,
+        token_type: 'Bearer'
+      }
+    })
+    setToken.mockResolvedValue({})
+
+    const wrapper = mount(LinuxDoCallbackView, {
+      global: {
+        stubs: {
+          AuthLayout: { template: '<div><slot /></div>' },
+          Icon: true,
+          RouterLink: { template: '<a><slot /></a>' },
+          transition: false
+        }
+      }
+    })
+
+    await flushPromises()
+
+    expect(exchangePendingOAuthCompletion).not.toHaveBeenCalled()
+    await wrapper.find('input[type="text"]').setValue('invite-code')
+    await wrapper.find('button').trigger('click')
+    await flushPromises()
+
+    expect(apiClientPost).toHaveBeenCalledWith('/auth/oauth/linuxdo/complete-registration', {
+      adopt_display_name: true,
+      adopt_avatar: true,
+      pending_oauth_token: 'legacy-pending-token',
+      invitation_code: 'invite-code'
+    })
+    expect(setToken).toHaveBeenCalledWith('legacy-access-token')
+    expect(replace).toHaveBeenCalledWith('/legacy-invite')
   })
 
   it('does not send adoption decisions during the initial exchange', async () => {
diff --git a/frontend/src/views/auth/__tests__/OidcCallbackView.spec.ts b/frontend/src/views/auth/__tests__/OidcCallbackView.spec.ts
index 0edcb931..18128f17 100644
--- a/frontend/src/views/auth/__tests__/OidcCallbackView.spec.ts
+++ b/frontend/src/views/auth/__tests__/OidcCallbackView.spec.ts
@@ -92,6 +92,74 @@ describe('OidcCallbackView', () => {
       turnstile_enabled: false,
       turnstile_site_key: ''
     })
+    window.location.hash = ''
+    localStorage.clear()
+  })
+
+  it('accepts the legacy fragment token success callback without pending-session exchange', async () => {
+    window.location.hash =
+      '#access_token=legacy-access-token&refresh_token=legacy-refresh-token&expires_in=3600&token_type=Bearer&redirect=%2Flegacy-dashboard'
+    setToken.mockResolvedValue({})
+
+    mount(OidcCallbackView, {
+      global: {
+        stubs: {
+          AuthLayout: { template: '<div><slot /></div>' },
+          Icon: true,
+          RouterLink: { template: '<a><slot /></a>' },
+          transition: false
+        }
+      }
+    })
+
+    await flushPromises()
+
+    expect(exchangePendingOAuthCompletion).not.toHaveBeenCalled()
+    expect(setToken).toHaveBeenCalledWith('legacy-access-token')
+    expect(localStorage.getItem('refresh_token')).toBe('legacy-refresh-token')
+    expect(localStorage.getItem('token_expires_at')).not.toBeNull()
+    expect(showSuccess).toHaveBeenCalledWith('auth.loginSuccess')
+    expect(replace).toHaveBeenCalledWith('/legacy-dashboard')
+  })
+
+  it('accepts the legacy pending oauth invitation fragment without pending-session exchange', async () => {
+    window.location.hash = '#error=invitation_required&pending_oauth_token=legacy-pending-token&redirect=%2Flegacy-invite'
+    apiClientPost.mockResolvedValue({
+      data: {
+        access_token: 'legacy-access-token',
+        refresh_token: 'legacy-refresh-token',
+        expires_in: 3600,
+        token_type: 'Bearer'
+      }
+    })
+    setToken.mockResolvedValue({})
+
+    const wrapper = mount(OidcCallbackView, {
+      global: {
+        stubs: {
+          AuthLayout: { template: '<div><slot /></div>' },
+          Icon: true,
+          RouterLink: { template: '<a><slot /></a>' },
+          transition: false
+        }
+      }
+    })
+
+    await flushPromises()
+
+    expect(exchangePendingOAuthCompletion).not.toHaveBeenCalled()
+    await wrapper.find('input[type="text"]').setValue('invite-code')
+    await wrapper.find('button').trigger('click')
+    await flushPromises()
+
+    expect(apiClientPost).toHaveBeenCalledWith('/auth/oauth/oidc/complete-registration', {
+      adopt_display_name: true,
+      adopt_avatar: true,
+      pending_oauth_token: 'legacy-pending-token',
+      invitation_code: 'invite-code'
+    })
+    expect(setToken).toHaveBeenCalledWith('legacy-access-token')
+    expect(replace).toHaveBeenCalledWith('/legacy-invite')
   })
 
   it('does not send adoption decisions during the initial exchange', async () => {