diff --git a/dotcom-rendering/src/lib/braze/BrazeBannersSystem.tsx b/dotcom-rendering/src/lib/braze/BrazeBannersSystem.tsx
index 4c910aa2022..18020832cd2 100644
--- a/dotcom-rendering/src/lib/braze/BrazeBannersSystem.tsx
+++ b/dotcom-rendering/src/lib/braze/BrazeBannersSystem.tsx
@@ -7,12 +7,15 @@ import type {
 	ReminderComponent,
 } from '@guardian/support-dotcom-components/dist/shared/types/reminders';
 import { useCallback, useEffect, useRef, useState } from 'react';
+import { submitComponentEvent } from '../../client/ophan/ophan';
+import { useConfig } from '../../components/ConfigContext';
 import { isProd } from '../../components/marketing/lib/stage';
 import type { StageType } from '../../types/config';
 import type { TagType } from '../../types/tag';
 import { getAuthState, getOptionsHeaders } from '../identity';
 import type { CandidateConfig, CanShowResult } from '../messagePicker';
 import { useAuthStatus } from '../useAuthStatus';
+import { useIsInView } from '../useIsInView';
 import type { BrazeInstance } from './initialiseBraze';
 import { suppressForTaylorReport } from './taylorReport';
 
@@ -150,12 +153,14 @@ export function refreshBanners(braze: BrazeInstance): Promise<void> {
  * Meta information required to display a Braze Banner.
  */
 export type BrazeBannersSystemMeta = {
+	id: string;
 	braze: BrazeInstance;
 	banner: Banner;
 };
 
 /**
  * Checks if a Braze Banner for the given placement ID can be shown.
+ * @param id Unique ID for the message candidate, used for logging and debugging
  * @param braze Braze instance
  * @param placementId Placement ID to check for a banner
  * @param contentType Content type of the article
@@ -164,6 +169,7 @@ export type BrazeBannersSystemMeta = {
  * @returns CanShowResult with the Banner meta if it can be shown
  */
 export const canShowBrazeBannersSystem = async (
+	id: string,
 	braze: BrazeInstance | null,
 	placementId: BrazeBannersSystemPlacementId,
 	contentType: string,
@@ -228,6 +234,7 @@ export const canShowBrazeBannersSystem = async (
 		return {
 			show: true,
 			meta: {
+				id,
 				braze,
 				banner,
 			},
@@ -266,6 +273,7 @@ export const buildBrazeBannersSystemConfig = (
 			id,
 			canShow: () => {
 				return canShowBrazeBannersSystem(
+					id,
 					braze,
 					placementId,
 					contentType,
@@ -455,6 +463,11 @@ export const BrazeBannersSystemDisplay = ({
 		useState<string>('#ffffff');
 	const [wrapperModeForegroundColor, setWrapperModeForegroundColor] =
 		useState<string>('#000000');
+	const { renderingTarget } = useConfig();
+	const [hasBeenSeen, setNode] = useIsInView({
+		debounce: true,
+		threshold: 0,
+	});
 
 	/**
 	 * Subscribes the user to a newsletter via the Identity API.
@@ -657,7 +670,19 @@ export const BrazeBannersSystemDisplay = ({
 			meta.braze.insertBanner(meta.banner, containerRef.current);
 
 			// CSS Checker
-			runCssCheckerOnBrazeBanner(meta);
+			const cssValidationResult = runCssCheckerOnBrazeBanner(meta);
+			if (!cssValidationResult) {
+				brazeBannersSystemLogger.warn(
+					'CSS validation failed for the Braze Banner. This may indicate broken styles. Check UI/UX ASAP!',
+				);
+				meta.braze.logCustomEvent(
+					'braze_banner_css_validation_failed',
+					{
+						placementId: meta.banner.placementId,
+					},
+				);
+				// We don't want to block the display of the banner if the CSS is broken, but we log it for awareness and action.
+			}
 		}
 	}, [showBanner, meta, meta.banner, meta.braze, setWrapperModeColors]);
 
@@ -729,6 +754,10 @@ export const BrazeBannersSystemDisplay = ({
 					});
 					break;
 				case BrazeBannersSystemMessageType.NewsletterSubscribe:
+					meta.braze.logBannerClick(
+						meta.banner,
+						'newsletter_subscribe_button',
+					);
 					const { newsletterId } = event.data;
 					if (newsletterId) {
 						void subscribeToNewsletter(newsletterId).then(
@@ -739,11 +768,23 @@ export const BrazeBannersSystemDisplay = ({
 										success,
 									},
 								);
+								meta.braze.logCustomEvent(
+									'braze_banner_newsletter_subscribe',
+									{
+										placementId: meta.banner.placementId,
+										newsletterId,
+										success,
+									},
+								);
 							},
 						);
 					}
 					break;
 				case BrazeBannersSystemMessageType.ReminderSubscribe:
+					meta.braze.logBannerClick(
+						meta.banner,
+						'reminder_subscribe_button',
+					);
 					const {
 						reminderPeriod,
 						reminderComponent,
@@ -761,6 +802,16 @@ export const BrazeBannersSystemDisplay = ({
 									success,
 								},
 							);
+							meta.braze.logCustomEvent(
+								'braze_banner_reminder_subscribe',
+								{
+									placementId: meta.banner.placementId,
+									reminderPeriod,
+									reminderComponent,
+									reminderOption,
+									success,
+								},
+							);
 						});
 					}
 					break;
@@ -771,8 +822,20 @@ export const BrazeBannersSystemDisplay = ({
 					);
 					break;
 				case BrazeBannersSystemMessageType.NavigateToUrl:
+					meta.braze.logBannerClick(
+						meta.banner,
+						'navigate_to_url_button',
+					);
 					const { url, target } = event.data;
 					if (url) {
+						meta.braze.logCustomEvent(
+							'braze_banner_navigate_to_url',
+							{
+								placementId: meta.banner.placementId,
+								url,
+								target,
+							},
+						);
 						if (target === 'blank') {
 							window.open(url, '_blank');
 						} else {
@@ -797,8 +860,11 @@ export const BrazeBannersSystemDisplay = ({
 					}
 					break;
 				case BrazeBannersSystemMessageType.DismissBanner:
-					// Remove the banner from the DOM
+					meta.braze.logBannerClick(meta.banner, 'dismiss_button');
 					dismissBanner();
+					meta.braze.logCustomEvent('braze_banner_dismissed', {
+						placementId: meta.banner.placementId,
+					});
 					break;
 			}
 		};
@@ -818,8 +884,38 @@ export const BrazeBannersSystemDisplay = ({
 		postMessageToBrazeBanner,
 	]);
 
-	// Log Impressions with Braze and Button Clicks with Ophan
-	// TODO
+	// Log Impressions when the banner is seen, using the hasBeenSeen value from the useIsInView hook
+	useEffect(() => {
+		if (hasBeenSeen) {
+			brazeBannersSystemLogger.info(
+				`Banner with placement ID "${meta.banner.placementId}" has been seen. Logging impression.`,
+			);
+
+			// Dispatch a custom event
+			document.dispatchEvent(
+				new CustomEvent('banner:open', {
+					detail: { bannerId: meta.id },
+				}),
+			);
+
+			// Log the impression with Braze
+			meta.braze.logBannerImpressions([meta.banner.placementId]);
+
+			// Log VIEW event with Ophan
+			void submitComponentEvent(
+				{
+					component: {
+						componentType: 'RETENTION_ENGAGEMENT_BANNER',
+						id:
+							meta.banner.getStringProperty('ophanComponentId') ??
+							meta.banner.placementId,
+					},
+					action: 'VIEW',
+				},
+				renderingTarget,
+			);
+		}
+	}, [hasBeenSeen, meta.banner, meta.id, meta.braze, renderingTarget]);
 
 	/**
 	 * If showBanner is false, we return null to unmount the component and remove the banner from the DOM.
@@ -831,6 +927,7 @@ export const BrazeBannersSystemDisplay = ({
 
 	return (
 		<div
+			ref={setNode}
 			className="braze-banner"
 			style={{
 				minHeight,
@@ -841,9 +938,9 @@ export const BrazeBannersSystemDisplay = ({
 							max-height: 65svh;
 							border-top: 1px solid rgb(0, 0, 0);
 							background-color: ${wrapperModeBackgroundColor};
-							${until.phablet} {
-								border: none;
-							}
+							overflow-y: auto;
+							overflow-x: hidden;
+							overscroll-behavior: none;
 					  `
 					: undefined
 			}
@@ -890,7 +987,7 @@ export const BrazeBannersSystemDisplay = ({
 									max-width: 660px;
 									grid-template:
 										'. .'
-										'copy-container close-button' / auto 0px;
+										'copy-container close-button' / 100% 0px;
 								}
 						  `
 						: undefined
diff --git a/dotcom-rendering/src/lib/braze/README.md b/dotcom-rendering/src/lib/braze/README.md
index 03e5f2f0e13..cea43a1336d 100644
--- a/dotcom-rendering/src/lib/braze/README.md
+++ b/dotcom-rendering/src/lib/braze/README.md
@@ -77,8 +77,10 @@ Because marketing teams have styling flexibility, there is a risk of campaigns t
 
 -   Parses the banner's HTML/CSS.
 -   Validates that every CSS selector matches at least one element.
--   Logs warnings (in development) if "dead" selectors are found.
-    This ensures broken creatives are caught during the QA process before launch.
+-   Logs warnings if "dead" selectors are found.
+-   On failure: emits a `brazeBannersSystemLogger.warn` and logs a Braze custom event `braze_banner_css_validation_failed` (with `placementId`) for Braze-side alerting. The banner is **not** blocked from rendering — it is shown regardless, but the failure is recorded for awareness and action.
+
+This ensures broken creatives are caught during the QA process before launch.
 
 #### B. JavaScript Isolation
 
@@ -103,7 +105,9 @@ To support more complex designs while maintaining consistency, the system suppor
 -   **Enabled via**: `wrapperModeEnabled` (Boolean) Key-Value pair.
 -   **Behavior**: When enabled, DCR applies specific styles to the **container** holding the Braze iframe, including:
     -   `max-height: 65svh` (prevents banners from taking over the full screen).
-    -   `border-top: 1px solid black` (provides visual separation).
+    -   `border-top: 1px solid black` (provides visual separation at all breakpoints — the previous phablet-level `border: none` override has been removed for consistency).
+    -   `overflow-y: auto` and `overflow-x: hidden` (allow vertical scrolling within the banner container on small/portrait screens).
+    -   `overscroll-behavior: none` (prevents scroll from propagating to the host page once the banner reaches its scroll boundary).
     -   Dynamic Background Color (see below).
 
 #### Automatic Color Contrast
@@ -118,14 +122,46 @@ When providing a background color in Wrapper Mode, DCR automatically calculates
 
 The system automatically reads specific Key-Value pairs from the Braze Campaign to configure the banner wrapper.
 
-| Key                          | Type    | Description                                                                                |
-| :--------------------------- | :------ | :----------------------------------------------------------------------------------------- |
-| `minHeight`                  | String  | Sets the CSS `min-height` of the container (e.g., "300px") to minimize layout shift (CLS). |
-| `wrapperModeEnabled`         | Boolean | Activates Wrapper Mode (see above).                                                        |
-| `wrapperModeBackgroundColor` | String  | Sets the background color of the wrapper and triggers the auto-contrast calculation.       |
+| Key                          | Type    | Description                                                                                                           |
+| :--------------------------- | :------ | :-------------------------------------------------------------------------------------------------------------------- |
+| `minHeight`                  | String  | Sets the CSS `min-height` of the container (e.g., "300px") to minimize layout shift (CLS).                            |
+| `wrapperModeEnabled`         | Boolean | Activates Wrapper Mode (see above).                                                                                   |
+| `wrapperModeBackgroundColor` | String  | Sets the background color of the wrapper and triggers the auto-contrast calculation.                                  |
+| `ophanComponentId`           | String  | Overrides the Ophan component ID used when logging the `VIEW` impression event. Defaults to `placementId` if not set. |
 
 _Custom keys can also be retrieved by the banner creative using the `BRAZE_BANNERS_SYSTEM:GET_SETTINGS_PROPERTY_VALUE` message._
 
+### 8. Impression Tracking & Analytics
+
+The system tracks when the banner enters the viewport and logs impressions to multiple destinations.
+
+#### Visibility Detection
+
+`BrazeBannersSystemDisplay` uses the `useIsInView` hook (backed by `IntersectionObserver`) to detect when the banner first becomes visible. Impression logging fires **once** per mount when `hasBeenSeen` becomes `true`.
+
+#### On First View
+
+When the banner enters the viewport for the first time, the following actions are performed in sequence:
+
+1.  **Logger**: `brazeBannersSystemLogger.info` records the event with the banner's placement ID.
+2.  **DOM Event**: A `banner:open` custom event is dispatched on `document`, carrying `{ bannerId: meta.id }`. This allows other parts of the page to react to the banner becoming visible.
+3.  **Braze Impression**: `meta.braze.logBannerImpressions([placementId])` notifies Braze that the banner was shown (used for frequency capping and campaign reporting).
+4.  **Ophan VIEW**: A `VIEW` component event is submitted via `submitComponentEvent` with `componentType: 'RETENTION_ENGAGEMENT_BANNER'`. The component ID is read from the `ophanComponentId` Key-Value pair, falling back to `placementId` if not set.
+
+### 9. User Interaction Logging
+
+All user interactions with the banner are tracked with both a Braze banner click (`logBannerClick`) and a Braze custom event (`logCustomEvent`) containing contextual metadata.
+
+| Interaction          | Braze Click Label             | Braze Custom Event                   | Custom Event Properties                                                           |
+| :------------------- | :---------------------------- | :----------------------------------- | :-------------------------------------------------------------------------------- |
+| Newsletter Subscribe | `newsletter_subscribe_button` | `braze_banner_newsletter_subscribe`  | `placementId`, `newsletterId`, `success`                                          |
+| Reminder Subscribe   | `reminder_subscribe_button`   | `braze_banner_reminder_subscribe`    | `placementId`, `reminderPeriod`, `reminderComponent`, `reminderOption`, `success` |
+| Navigate to URL      | `navigate_to_url_button`      | `braze_banner_navigate_to_url`       | `placementId`, `url`, `target`                                                    |
+| Dismiss Banner       | `dismiss_button`              | `braze_banner_dismissed`             | `placementId`                                                                     |
+| CSS Validation Fail  | —                             | `braze_banner_css_validation_failed` | `placementId`                                                                     |
+
+> The Braze click (`logBannerClick`) feeds native Braze campaign reports, while the custom event (`logCustomEvent`) provides granular analytics available in Braze Data Export and BigQuery.
+
 ## Communication Protocol
 
 The banner uses a `postMessage` protocol to interact with the host DCR page.
@@ -663,4 +699,4 @@ const brazeCandidate = buildBrazeBannersSystemConfig(
 ---
 
 **Value Team**
-_Last Updated: February 2026_
+_Last Updated: March 2026_