perf(memory-graph): fix O(n^2) BFS queue drain in computeClusterAssignments (#1714)

packages/memory-graph/src/__tests__/graph-data-utils.test.ts

@@ -140,6 +140,24 @@ describe("cluster assignments", () => {
 
 		expect(assignments.get("a1")?.key).toBe(assignments.get("b1")?.key)
 	})
+
+	it("merges a wide fan-out of memories relating to one hub into a single cluster", () => {
+		const hub = makeDocument("doc-hub", [makeMemory({ id: "hub" })])
+		const spokes = Array.from({ length: 200 }, (_, i) =>
+			makeDocument(`doc-${i}`, [
+				makeMemory({ id: `spoke-${i}`, memoryRelations: { hub: "derives" } }),
+			]),
+		)
+
+		const assignments = computeClusterAssignments([hub, ...spokes])
+
+		const hubKey = assignments.get("hub")?.key
+		expect(hubKey).toBeDefined()
+		for (let i = 0; i < spokes.length; i++) {
+			expect(assignments.get(`spoke-${i}`)?.key).toBe(hubKey)
+		}
+		expect(assignments.get("hub")?.size).toBe(spokes.length + 1)
+	})
 })
 
 describe("memory orbit placement", () => {

packages/memory-graph/src/hooks/use-graph-data.ts

@@ -157,10 +157,12 @@ export function computeClusterAssignments(
 
 		const component: string[] = []
 		const queue = [startId]
+		// index dequeue: shift() is O(n) per call, O(n^2) on wide components
+		let head = 0
 		visited.add(startId)
 
-		while (queue.length > 0) {
-			const id = queue.shift() as string
+		while (head < queue.length) {
+			const id = queue[head++] as string
 			component.push(id)
 			for (const nextId of adjacency.get(id) ?? []) {
 				if (visited.has(nextId)) continue