diff --git a/docs/content/1.guide/18.hub-initiate.md b/docs/content/1.guide/18.hub-initiate.md
index c8685810..7559d963 100644
--- a/docs/content/1.guide/18.hub-initiate.md
+++ b/docs/content/1.guide/18.hub-initiate.md
@@ -61,7 +61,8 @@ interface DevframeHubUi {
 
 `@devframes/hub-ui`'s `createUi()` is the reference (standalone `viewer` SPA + floating dock); its `setup(ctx)` publishes config to `ctx.staticConfig.ui` (`ConnectionMeta.configs.ui`):
 
-- **`branding`** — rebrand the UI (logo, name, primary color).
+- **`viewer`** — set to `false` to disable the standalone viewer.
+- **`branding`** — rebrand the UI (logo, name, primary color). `background` accepts any CSS `background` value (color, gradient, image, or `transparent`) or `{ light, dark }` variants; omit it to keep the design default.
 - **`dockPreferences`** — dock-rail: `categoryOrder`, floating-dock `maxVisibleItems`, first-run `defaultMode` (`'float'`/`'edge'`) and `defaultPosition`.
 - **`embeddedVisibility`** — the floating dock's reveal policy:
   - `'normal'` (default) — shows immediately.
diff --git a/packages/hub-ui/src/client/standalone/index.html b/packages/hub-ui/src/client/standalone/index.html
index fbf2a89b..97510332 100644
--- a/packages/hub-ui/src/client/standalone/index.html
+++ b/packages/hub-ui/src/client/standalone/index.html
@@ -6,15 +6,22 @@
     <title>Devframes</title>
     <meta name="description" content="Devframes hub" />
     <style>
+      :root {
+        color-scheme: light;
+        --devframes-viewer-background: #fff;
+      }
+      html.dark {
+        color-scheme: dark;
+        --devframes-viewer-background: #111;
+      }
+      html.viewer-background-custom {
+        color-scheme: normal;
+      }
       html,
       body {
         margin: 0;
         height: 100%;
-        background: #fff;
-      }
-      html.dark,
-      html.dark body {
-        background: #111;
+        background: var(--devframes-viewer-background);
       }
       #app {
         height: 100%;
diff --git a/packages/hub-ui/src/client/standalone/main.ts b/packages/hub-ui/src/client/standalone/main.ts
index 9f357457..5fde3835 100644
--- a/packages/hub-ui/src/client/standalone/main.ts
+++ b/packages/hub-ui/src/client/standalone/main.ts
@@ -2,7 +2,7 @@ import type { DockSessionStorage } from '@devframes/hub/client'
 import { getDevframeRpcClient, setDevframeClientContext } from '@devframes/hub/client'
 import { useSessionStorage } from '@vueuse/core'
 import { watchEffect } from 'vue'
-import { applyDocumentHead, applyPrimaryColor, setBranding } from '../state/branding'
+import { applyDocumentHead, applyPrimaryColor, setBranding, useBrandingBackground } from '../state/branding'
 import { isDark } from '../state/color-mode'
 import { DEFAULT_DOCK_SESSION_STORE } from '../state/docks'
 
@@ -12,14 +12,28 @@ import { DEFAULT_DOCK_SESSION_STORE } from '../state/docks'
 // shell stays frameworkless on purpose; everything visual lives inside the
 // custom element's shadow root.
 
-// The standalone page runs in the light DOM, so mirror the color mode onto the
-// document element — its background and native controls follow the
-// Auto/Light/Dark choice.
+// The standalone viewer runs in the light DOM, so mirror the color mode onto the
+// document element — its background follows the Auto/Light/Dark choice. The
+// component tree carries `color-scheme` for its native controls; keeping that
+// off the document lets custom backgrounds composite with the host page.
+const brandingBackground = useBrandingBackground()
+
+function applyViewerBackground(documentElement: HTMLElement, background: string | undefined): void {
+  if (background === undefined || !CSS.supports('background', background)) {
+    documentElement.classList.remove('viewer-background-custom')
+    documentElement.style.removeProperty('--devframes-viewer-background')
+    return
+  }
+
+  documentElement.classList.add('viewer-background-custom')
+  documentElement.style.setProperty('--devframes-viewer-background', background)
+}
+
 watchEffect(() => {
   const el = document.documentElement
   el.classList.toggle('dark', isDark.value)
   el.classList.toggle('light', !isDark.value)
-  el.style.colorScheme = isDark.value ? 'dark' : 'light'
+  applyViewerBackground(el, brandingBackground.value)
 })
 
 async function main(): Promise<void> {
diff --git a/packages/hub-ui/src/client/state/branding.test.ts b/packages/hub-ui/src/client/state/branding.test.ts
new file mode 100644
index 00000000..a3ac3631
--- /dev/null
+++ b/packages/hub-ui/src/client/state/branding.test.ts
@@ -0,0 +1,19 @@
+import { afterEach, describe, expect, it } from 'vitest'
+import { setBranding, useBrandingBackground } from './branding'
+import { setColorSchemePreference } from './color-mode'
+
+afterEach(() => {
+  setBranding({})
+  setColorSchemePreference('auto')
+})
+
+describe('useBrandingBackground', () => {
+  it('preserves an empty dark value for CSS validation', () => {
+    expect.assertions(1)
+
+    setColorSchemePreference('dark')
+    setBranding({ background: { light: 'white', dark: '' } })
+
+    expect(useBrandingBackground().value).toBe('')
+  })
+})
diff --git a/packages/hub-ui/src/client/state/branding.ts b/packages/hub-ui/src/client/state/branding.ts
index 0467eb0c..b38d006c 100644
--- a/packages/hub-ui/src/client/state/branding.ts
+++ b/packages/hub-ui/src/client/state/branding.ts
@@ -3,12 +3,15 @@ import type { BrandingLogo, DevframeBranding } from '../../types'
 import { computed, ref } from 'vue'
 import { isDark } from './color-mode'
 
+type ColorSchemeValue = string | { light: string, dark: string }
+
 /** Branding with defaults resolved — what the UI actually renders. */
 export interface ResolvedBranding {
   productName: string
   logo?: BrandingLogo
   wordmark?: BrandingLogo
   primaryColor?: string
+  background?: DevframeBranding['background']
   tagline?: string
   favicon?: string
   windowTitle: string
@@ -23,6 +26,7 @@ function resolveDefaults(branding: DevframeBranding): ResolvedBranding {
     logo: branding.logo,
     wordmark: branding.wordmark,
     primaryColor: branding.primaryColor,
+    background: branding.background,
     tagline: branding.tagline,
     favicon: branding.favicon,
     windowTitle: branding.windowTitle?.trim() || productName,
@@ -44,15 +48,20 @@ export function setBranding(branding: DevframeBranding): ResolvedBranding {
 
 /** The logo/wordmark URL for the current color scheme, reactive to it. */
 export function useBrandingLogo(pick: (b: ResolvedBranding) => BrandingLogo | undefined = b => b.logo): Ref<string | undefined> {
-  return computed(() => resolveLogo(pick(currentBranding.value), isDark.value))
+  return computed(() => resolveColorSchemeValue(pick(currentBranding.value), isDark.value))
+}
+
+/** The standalone viewer background for the current color scheme. */
+export function useBrandingBackground(): Ref<string | undefined> {
+  return computed(() => resolveColorSchemeValue(currentBranding.value.background, isDark.value))
 }
 
-function resolveLogo(logo: BrandingLogo | undefined, dark: boolean): string | undefined {
-  if (!logo)
+function resolveColorSchemeValue(value: ColorSchemeValue | undefined, dark: boolean): string | undefined {
+  if (!value)
     return undefined
-  if (typeof logo === 'string')
-    return logo
-  return dark ? (logo.dark || logo.light) : logo.light
+  if (typeof value === 'string')
+    return value
+  return dark ? (value.dark ?? value.light) : value.light
 }
 
 // --- Applying to the DOM --------------------------------------------------
diff --git a/packages/hub-ui/src/index.test.ts b/packages/hub-ui/src/index.test.ts
new file mode 100644
index 00000000..74367122
--- /dev/null
+++ b/packages/hub-ui/src/index.test.ts
@@ -0,0 +1,70 @@
+import type { DevframeHubContext } from '@devframes/hub/node'
+import { readFileSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { describe, expect, it } from 'vitest'
+import { createUi } from './index'
+
+function createContext(): DevframeHubContext {
+  return { staticConfig: {} } as unknown as DevframeHubContext
+}
+
+describe('createUi branding background', () => {
+  it('defines the viewer background through a static token', () => {
+    expect.assertions(6)
+
+    const html = readFileSync(fileURLToPath(new URL('../dist/client/standalone/index.html', import.meta.url)), 'utf8')
+
+    expect(html).not.toContain('__hub-ui.css')
+    expect(html).toContain('html.viewer-background-custom')
+    expect(html).toContain('--devframes-viewer-background: #fff')
+    expect(html).toContain('--devframes-viewer-background: #111')
+    expect(html).toContain('background: var(--devframes-viewer-background)')
+    expect(html).toMatch(/html\.viewer-background-custom\s*\{[^}]*color-scheme:\s*normal/)
+  })
+
+  it('preserves the default viewer background', () => {
+    expect.assertions(2)
+
+    const context = createContext()
+    const ui = createUi()
+    ui.setup?.(context)
+
+    expect(context.staticConfig.ui).toEqual({ branding: {} })
+    expect(ui.assets).toBeUndefined()
+  })
+
+  it('publishes a CSS viewer background with the branding', () => {
+    expect.assertions(2)
+
+    const context = createContext()
+    const ui = createUi({ branding: { background: 'transparent' } })
+    ui.setup?.(context)
+
+    expect(context.staticConfig.ui).toEqual({
+      branding: { background: 'transparent' },
+    })
+    expect(ui.assets).toBeUndefined()
+  })
+
+  it('publishes color-scheme viewer backgrounds with the branding', () => {
+    expect.assertions(1)
+
+    const context = createContext()
+    const background = {
+      light: 'linear-gradient(white, transparent)',
+      dark: 'linear-gradient(#111, transparent)',
+    }
+    const ui = createUi({ branding: { background } })
+    ui.setup?.(context)
+
+    expect(context.staticConfig.ui).toEqual({ branding: { background } })
+  })
+
+  it('disables the standalone viewer', () => {
+    expect.assertions(1)
+
+    const ui = createUi({ viewer: false })
+
+    expect(ui.viewer).toBeUndefined()
+  })
+})
diff --git a/packages/hub-ui/src/types.ts b/packages/hub-ui/src/types.ts
index aaf7259f..d31f8afa 100644
--- a/packages/hub-ui/src/types.ts
+++ b/packages/hub-ui/src/types.ts
@@ -31,6 +31,8 @@ export interface DevframeBranding {
   wordmark?: BrandingLogo
   /** Brand color; feeds `--devframe-primary` and the whole primary ramp. */
   primaryColor?: string
+  /** Standalone viewer CSS `background`; a string applies to both color schemes. */
+  background?: string | { light: string, dark: string }
   /** Short line for the auth screen and the standalone meta description. */
   tagline?: string
   /** Favicon URL — applied on the standalone viewer and the popped-out window only. */
diff --git a/tests/__snapshots__/tsnapi/@devframes/hub-ui/index.snapshot.d.ts b/tests/__snapshots__/tsnapi/@devframes/hub-ui/index.snapshot.d.ts
index 38bfd4a1..a30eabb0 100644
--- a/tests/__snapshots__/tsnapi/@devframes/hub-ui/index.snapshot.d.ts
+++ b/tests/__snapshots__/tsnapi/@devframes/hub-ui/index.snapshot.d.ts
@@ -14,6 +14,10 @@ export interface DevframeBranding {
   logo?: BrandingLogo;
   wordmark?: BrandingLogo;
   primaryColor?: string;
+  background?: string | {
+    light: string;
+    dark: string;
+  };
   tagline?: string;
   favicon?: string;
   windowTitle?: string;