diff --git a/apps/ui-admin/src/modules/server-admin-context.test.ts b/apps/ui-admin/src/modules/server-admin-context.test.ts
index 5d7fe8c06..8aa896cbf 100644
--- a/apps/ui-admin/src/modules/server-admin-context.test.ts
+++ b/apps/ui-admin/src/modules/server-admin-context.test.ts
@@ -32,7 +32,12 @@ describe('ui-admin bootstrap context', () => {
   })
 
   it('keeps non-local standalone origins unchanged without redirect context', () => {
-    expect(defaultStandaloneApiServerUrl('https://admin.airi.build')).toBe('https://admin.airi.build')
+    expect(defaultStandaloneApiServerUrl('https://admin-preview.example')).toBe('https://admin-preview.example')
+  })
+
+  it('defaults known standalone admin deployments to their API origins', () => {
+    expect(defaultStandaloneApiServerUrl('https://admin.airi.build')).toBe('https://api.airi.build')
+    expect(defaultStandaloneApiServerUrl('https://server-dev.airi-server-admin.pages.dev')).toBe('https://airi-server-dev.up.railway.app')
   })
 
   it('falls back to the standalone query context when the static placeholder script is still present', () => {
diff --git a/apps/ui-admin/src/modules/server-admin-context.ts b/apps/ui-admin/src/modules/server-admin-context.ts
index 294bd711b..fdc19781b 100644
--- a/apps/ui-admin/src/modules/server-admin-context.ts
+++ b/apps/ui-admin/src/modules/server-admin-context.ts
@@ -11,6 +11,11 @@ const TRUSTED_STANDALONE_API_SERVER_ORIGINS = [
   'https://airi-server-dev.up.railway.app',
 ]
 
+const DEFAULT_API_SERVER_ORIGINS_BY_ADMIN_UI_ORIGIN = new Map([
+  ['https://admin.airi.build', 'https://api.airi.build'],
+  ['https://server-dev.airi-server-admin.pages.dev', 'https://airi-server-dev.up.railway.app'],
+])
+
 const TRUSTED_LOCAL_API_SERVER_ORIGIN_PATTERNS = [
   /^http:\/\/localhost(:\d+)?$/,
   /^http:\/\/127\.0\.0\.1(:\d+)?$/,
@@ -59,6 +64,9 @@ export function defaultApiServerUrl(): string {
  */
 export function defaultStandaloneApiServerUrl(currentOrigin: string): string {
   const origin = new URL(currentOrigin).origin
+  const knownApiServerOrigin = DEFAULT_API_SERVER_ORIGINS_BY_ADMIN_UI_ORIGIN.get(origin)
+  if (knownApiServerOrigin)
+    return knownApiServerOrigin
 
   if (TRUSTED_LOCAL_API_SERVER_ORIGIN_PATTERNS.some(pattern => pattern.test(origin))) {
     const url = new URL(origin)
diff --git a/apps/ui-server-auth/src/modules/sign-in.test.ts b/apps/ui-server-auth/src/modules/sign-in.test.ts
index 91d2b9e58..4aceb9b84 100644
--- a/apps/ui-server-auth/src/modules/sign-in.test.ts
+++ b/apps/ui-server-auth/src/modules/sign-in.test.ts
@@ -76,6 +76,34 @@ describe('ui-server-auth sign-in flow helpers', () => {
     })
   })
 
+  it('keeps trusted standalone admin redirects on the admin origin', () => {
+    expect(createServerSignInContext(
+      'https://accounts.airi.build/ui/sign-in?redirect=https%3A%2F%2Fadmin.airi.build%2Fllm-router%3Fapi_server_url%3Dhttps%253A%252F%252Fairi-server-dev.up.railway.app',
+      'https://api.airi.test',
+    )).toEqual({
+      callbackURL: 'https://admin.airi.build/llm-router?api_server_url=https%3A%2F%2Fairi-server-dev.up.railway.app',
+      requestedProvider: null,
+    })
+
+    expect(createServerSignInContext(
+      'https://accounts.airi.build/ui/sign-in?redirect=http%3A%2F%2F127.0.0.1%3A5178%2Fllm-router%3Fapi_server_url%3Dhttp%253A%252F%252F127.0.0.1%253A3000',
+      'https://api.airi.test',
+    )).toEqual({
+      callbackURL: 'http://127.0.0.1:5178/llm-router?api_server_url=http%3A%2F%2F127.0.0.1%3A3000',
+      requestedProvider: null,
+    })
+  })
+
+  it('rejects absolute redirects to untrusted origins', () => {
+    expect(createServerSignInContext(
+      'https://accounts.airi.build/ui/sign-in?redirect=https%3A%2F%2Fevil.example%2Fllm-router',
+      'https://api.airi.test',
+    )).toEqual({
+      callbackURL: '/',
+      requestedProvider: null,
+    })
+  })
+
   it('posts the selected provider and callback URL to the social sign-in endpoint', async () => {
     const fetchImpl = vi.fn<typeof fetch>(async () => {
       return new Response(JSON.stringify({ url: 'https://accounts.example.test/oauth/google' }), {
diff --git a/apps/ui-server-auth/src/modules/sign-in.ts b/apps/ui-server-auth/src/modules/sign-in.ts
index 5771f70b2..b8810ca4b 100644
--- a/apps/ui-server-auth/src/modules/sign-in.ts
+++ b/apps/ui-server-auth/src/modules/sign-in.ts
@@ -3,6 +3,18 @@ import type { OAuthProvider } from '@proj-airi/stage-ui/libs/auth'
 import { extractAuthError } from './auth-fetch'
 import { buildAuthUiPath } from './auth-ui-base'
 
+const TRUSTED_ADMIN_REDIRECT_ORIGINS = [
+  'https://admin.airi.build',
+  'https://server-dev.airi-server-admin.pages.dev',
+]
+
+const TRUSTED_LOCAL_ADMIN_REDIRECT_ORIGIN_PATTERNS = [
+  /^http:\/\/localhost(:\d+)?$/,
+  /^http:\/\/127\.0\.0\.1(:\d+)?$/,
+  /^https:\/\/localhost(:\d+)?$/,
+  /^https:\/\/127\.0\.0\.1(:\d+)?$/,
+]
+
 export interface ServerSignInContext {
   callbackURL: string
   requestedProvider: string | null
@@ -55,7 +67,14 @@ export function createServerSignInContext(currentUrl: string, apiServerUrl: stri
 }
 
 function normalizeStandaloneRedirect(currentUrl: URL, redirect: string | null): string | null {
-  if (!redirect || !redirect.startsWith('/') || redirect.startsWith('//'))
+  if (!redirect)
+    return null
+
+  const trustedAdminRedirect = normalizeTrustedAdminRedirect(redirect)
+  if (trustedAdminRedirect)
+    return trustedAdminRedirect
+
+  if (!redirect.startsWith('/') || redirect.startsWith('//'))
     return null
 
   if (redirect.startsWith('/admin'))
@@ -64,6 +83,22 @@ function normalizeStandaloneRedirect(currentUrl: URL, redirect: string | null):
   return `${currentUrl.origin}${buildAuthUiPath(redirect)}`
 }
 
+function normalizeTrustedAdminRedirect(redirect: string): string | null {
+  try {
+    const url = new URL(redirect)
+    if (TRUSTED_ADMIN_REDIRECT_ORIGINS.includes(url.origin))
+      return url.toString()
+
+    if (TRUSTED_LOCAL_ADMIN_REDIRECT_ORIGIN_PATTERNS.some(pattern => pattern.test(url.origin)))
+      return url.toString()
+
+    return null
+  }
+  catch {
+    return null
+  }
+}
+
 export async function requestSocialSignInRedirect(params: SocialSignInRedirectParams): Promise<string> {
   const fetchImpl = params.fetchImpl ?? fetch
   const endpoint = new URL('/api/auth/sign-in/social', params.apiServerUrl)