diff --git a/packages/memory-graph/README.md b/packages/memory-graph/README.md
index 83710f5a..4ec4db0a 100644
--- a/packages/memory-graph/README.md
+++ b/packages/memory-graph/README.md
@@ -66,6 +66,7 @@ function App() {
 | `error` | `Error \| null` | Error to display |
 | `loadMoreDocuments` | `() => Promise<void>` | Function to load more data |
 | `highlightDocumentIds` | `string[]` | IDs of documents to highlight |
+| `onNodeSelect` | `(nodeId: string \| null) => void` | Called when the selected node changes (click, keyboard, slideshow, or cleared) |
 
 ## Documentation
 
diff --git a/packages/memory-graph/src/components/memory-graph.tsx b/packages/memory-graph/src/components/memory-graph.tsx
index d165ac71..f0d5e342 100644
--- a/packages/memory-graph/src/components/memory-graph.tsx
+++ b/packages/memory-graph/src/components/memory-graph.tsx
@@ -39,6 +39,7 @@ export function MemoryGraph({
 	colors: colorOverrides,
 	totalCount,
 	onOpenDocument,
+	onNodeSelect,
 	labels: labelOverrides,
 	layering,
 }: MemoryGraphProps) {
@@ -73,6 +74,21 @@ export function MemoryGraph({
 	// Used as a dependency proxy to recalculate popover positions
 	const [viewportVersion, setViewportVersion] = useState(0)
 
+	// Surface selection changes to the host without making selection controlled.
+	// Keyed on selectedNode only; the callback is read through a ref so a changing
+	// callback identity does not re-fire it. The initial mount is skipped so a
+	// host does not receive a spurious null before any interaction.
+	const onNodeSelectRef = useRef(onNodeSelect)
+	onNodeSelectRef.current = onNodeSelect
+	const hasEmittedSelectionRef = useRef(false)
+	useEffect(() => {
+		if (!hasEmittedSelectionRef.current) {
+			hasEmittedSelectionRef.current = true
+			return
+		}
+		onNodeSelectRef.current?.(selectedNode)
+	}, [selectedNode])
+
 	// Limit documents so total node count (documents + their memories) stays under maxNodes
 	const limitedDocuments = useMemo(() => {
 		if (!maxNodes || documents.length === 0) return documents
diff --git a/packages/memory-graph/src/types.ts b/packages/memory-graph/src/types.ts
index f871b3da..32bfcaae 100644
--- a/packages/memory-graph/src/types.ts
+++ b/packages/memory-graph/src/types.ts
@@ -216,6 +216,13 @@ export interface MemoryGraphProps {
 	totalCount?: number
 	/** Callback when user wants to view full document content */
 	onOpenDocument?: (documentId: string) => void
+	/**
+	 * Called whenever the selected node changes, by click, keyboard navigation,
+	 * slideshow, or clearing the selection (nodeId is null when nothing is
+	 * selected). Lets a host observe selection without owning the state, e.g. to
+	 * drive a side panel or sync the URL.
+	 */
+	onNodeSelect?: (nodeId: string | null) => void
 	/** Custom user-facing labels (partial) - merged with defaults */
 	labels?: MemoryGraphLabels
 	/** Overlay layering controls */