diff --git a/cli/src/components/waiting-room-screen.tsx b/cli/src/components/waiting-room-screen.tsx
index 2bbee6c71..d48d986d2 100644
--- a/cli/src/components/waiting-room-screen.tsx
+++ b/cli/src/components/waiting-room-screen.tsx
@@ -90,6 +90,7 @@ export const WaitingRoomScreen: React.FC<WaitingRoomScreenProps> = ({
     forceStart: true,
     provider: 'gravity',
     fallbackProvider: 'carbon',
+    surface: 'waiting_room',
   })
 
   useFreebuffCtrlCExit()
diff --git a/cli/src/hooks/use-gravity-ad.ts b/cli/src/hooks/use-gravity-ad.ts
index 36a18faae..ea6977864 100644
--- a/cli/src/hooks/use-gravity-ad.ts
+++ b/cli/src/hooks/use-gravity-ad.ts
@@ -35,6 +35,7 @@ export type AdVariant = 'banner' | 'choice'
  * same normalized response shape, so the rest of the hook is provider-agnostic.
  */
 export type AdProvider = 'gravity' | 'carbon'
+export type AdSurface = 'waiting_room'
 
 export type AdData =
   | { variant: 'banner'; ad: AdResponse }
@@ -112,11 +113,14 @@ export const useGravityAd = (options?: {
   provider?: AdProvider
   /** Backup ad network to try when the primary returns no fill or errors. */
   fallbackProvider?: AdProvider
+  /** Product surface requesting the ad. The server maps this to placements. */
+  surface?: AdSurface
 }): GravityAdState => {
   const enabled = options?.enabled ?? true
   const forceStart = options?.forceStart ?? false
   const provider: AdProvider = options?.provider ?? 'gravity'
   const fallbackProvider = options?.fallbackProvider
+  const surface = options?.surface
   const [ad, setAd] = useState<AdResponse | null>(null)
   const [adData, setAdData] = useState<AdData | null>(null)
   const [isLoading, setIsLoading] = useState(false)
@@ -299,6 +303,7 @@ export const useGravityAd = (options?: {
             messages: adMessages,
             sessionId: useChatStore.getState().chatSessionId,
             device: getDeviceInfo(),
+            ...(surface ? { surface } : {}),
             // Carbon requires a real browser-ish useragent for targeting/fraud
             // detection. Gravity ignores it. We source one centrally so every
             // provider that needs it sees the same value.
@@ -430,7 +435,7 @@ export const useGravityAd = (options?: {
       clearInterval(id)
       ctrlRef.current.intervalId = null
     }
-  }, [shouldStart, shouldHideAds, provider, fallbackProvider])
+  }, [shouldStart, shouldHideAds, provider, fallbackProvider, surface])
 
   // Don't return ad when ads should be hidden
   const visible = shouldStart && !shouldHideAds
diff --git a/web/src/app/api/v1/ads/_post.ts b/web/src/app/api/v1/ads/_post.ts
index fc1fa07a5..a56846b05 100644
--- a/web/src/app/api/v1/ads/_post.ts
+++ b/web/src/app/api/v1/ads/_post.ts
@@ -35,12 +35,14 @@ const deviceSchema = z.object({
 })
 
 const providerSchema = z.enum(['gravity', 'carbon']).default('gravity')
+const surfaceSchema = z.enum(['waiting_room'])
 
 const bodySchema = z.object({
   provider: providerSchema.optional(),
   messages: z.array(messageSchema).optional().default([]),
   sessionId: z.string().optional(),
   device: deviceSchema.optional(),
+  surface: surfaceSchema.optional(),
   /** Browser/CLI useragent passed through to providers that require it. */
   userAgent: z.string().optional(),
 })
@@ -136,6 +138,7 @@ export async function postAds(params: {
       clientIp,
       userAgent,
       device: parsedBody.device,
+      surface: parsedBody.surface,
       messages: parsedBody.messages,
       testMode: serverEnv.CB_ENVIRONMENT !== 'prod',
       logger,
diff --git a/web/src/lib/ad-providers/gravity.ts b/web/src/lib/ad-providers/gravity.ts
index ed9209cb0..4ae33b514 100644
--- a/web/src/lib/ad-providers/gravity.ts
+++ b/web/src/lib/ad-providers/gravity.ts
@@ -19,6 +19,12 @@ const CHOICE_PLACEMENT_IDS = [
   'choice-ad-3',
   'choice-ad-4',
 ]
+const WAITING_ROOM_PLACEMENT_IDS = [
+  'waiting-room-1',
+  'waiting-room-2',
+  'waiting-room-3',
+  'waiting-room-4',
+]
 
 type GravityRawAd = {
   adText: string
@@ -105,16 +111,21 @@ export function createGravityProvider(config: { apiKey: string }): AdProvider {
         fetch,
       } = input
 
-      const variant = getGravityVariant(userId)
+      const variant =
+        input.surface === 'waiting_room' ? 'choice' : getGravityVariant(userId)
       const filteredMessages = prepareGravityMessages(messages)
 
-      const placements =
-        variant === 'choice'
-          ? CHOICE_PLACEMENT_IDS.map((id) => ({
-              placement: 'below_response',
-              placement_id: id,
-            }))
-          : [{ placement: 'below_response', placement_id: BANNER_PLACEMENT_ID }]
+      const placementIds =
+        input.surface === 'waiting_room'
+          ? WAITING_ROOM_PLACEMENT_IDS
+          : variant === 'choice'
+          ? CHOICE_PLACEMENT_IDS
+          : [BANNER_PLACEMENT_ID]
+
+      const placements = placementIds.map((id) => ({
+        placement: 'below_response',
+        placement_id: id,
+      }))
 
       const deviceBody = clientIp
         ? {
diff --git a/web/src/lib/ad-providers/types.ts b/web/src/lib/ad-providers/types.ts
index 5b664332b..fb3284e2a 100644
--- a/web/src/lib/ad-providers/types.ts
+++ b/web/src/lib/ad-providers/types.ts
@@ -41,6 +41,8 @@ export type AdDeviceInfo = {
   locale?: string
 }
 
+export type AdSurface = 'waiting_room'
+
 export type FetchAdInput = {
   userId: string
   userEmail: string | null
@@ -50,6 +52,8 @@ export type FetchAdInput = {
   /** Browser/CLI useragent string, passed through to upstream. */
   userAgent?: string
   device?: AdDeviceInfo
+  /** Product surface requesting the ad. Providers may map this to placements. */
+  surface?: AdSurface
   /** Last user + last preceding assistant message, if any. Used by Gravity. */
   messages?: AdMessage[]
   /** Set in non-prod so providers can request test ads. */