diff --git a/docs/concepts/workspaces.mdx b/docs/concepts/workspaces.mdx
index bbf56428b..5befe8b02 100644
--- a/docs/concepts/workspaces.mdx
+++ b/docs/concepts/workspaces.mdx
@@ -32,4 +32,4 @@ Think of it as the place where the work happens: you keep the actual source mate
 
 ## Source of Truth
 
-The app stores workspace access, the item tree, relationships, current document checkpoints, and extracted text in Postgres. Original and preview file bytes live in R2. The `WorkspaceKernel` Durable Object is a live room for presence, revision notifications, and cleanup coordination; it is not a second database. Clients refetch the authoritative workspace query when a newer revision is announced. UI and AI operations go through workspace commands rather than writing directly to scattered client state.
+The app stores workspace access, the item tree, relationships, current document checkpoints, and extracted text in Postgres. Original and preview file bytes live in R2. The `WorkspaceKernel` Durable Object is a live room for presence, workspace-page deltas, and cleanup coordination; it is not a second database. Clients apply canonical item deltas and refetch the authoritative workspace query after reconnecting or when a full refresh is announced. UI and AI operations go through workspace commands rather than writing directly to scattered client state.
diff --git a/package.json b/package.json
index 568797a61..d37db5c40 100644
--- a/package.json
+++ b/package.json
@@ -78,7 +78,6 @@
 		"@posthog/rollup-plugin": "^1.4.7",
 		"@streamdown/cjk": "^1.0.3",
 		"@streamdown/math": "^1.0.2",
-		"@tanstack/pacer": "^0.22.0",
 		"@tanstack/react-hotkeys": "^0.10.0",
 		"@tanstack/react-query": "5.101.4",
 		"@tanstack/react-router": "1.170.23",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 22882b100..b6dfb44f3 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -134,9 +134,6 @@ importers:
       '@streamdown/math':
         specifier: ^1.0.2
         version: 1.0.2(react@19.2.8)
-      '@tanstack/pacer':
-        specifier: ^0.22.0
-        version: 0.22.0
       '@tanstack/react-hotkeys':
         specifier: ^0.10.0
         version: 0.10.0(react-dom@19.2.8(react@19.2.8))(react@19.2.8)
@@ -3638,10 +3635,6 @@ packages:
     resolution: {integrity: sha512-vqH7X9nb0MTJ/O08++dB5bP9jgj4+BIPOUu/U+6myG86lDsirZSVSobpq5UQpE7nBuk62i8eIYeOhd+OMl/UrA==}
     engines: {node: '>=18'}
 
-  '@tanstack/pacer@0.22.0':
-    resolution: {integrity: sha512-Zq23KOn30tFiA6ZYWihs5x++ttHkOIcnIIjRrJq05tGrYx9+iHsmVaj8jb7UJVemEI+JRWGzJ9C+50YV4nRz0w==}
-    engines: {node: '>=18'}
-
   '@tanstack/query-core@5.101.4':
     resolution: {integrity: sha512-gNwcvOJcRbLWPOLG/2OBm+zM+Yv+MKsXKEOWC57USuZDEsI71hEErQsiEGx5wX9rzWWkfwM0fVSPoiIFSsxfiw==}
 
@@ -11903,11 +11896,6 @@ snapshots:
     dependencies:
       '@tanstack/store': 0.11.1
 
-  '@tanstack/pacer@0.22.0':
-    dependencies:
-      '@tanstack/devtools-event-client': 0.5.0
-      '@tanstack/store': 0.11.1
-
   '@tanstack/query-core@5.101.4': {}
 
   '@tanstack/query-devtools@5.101.4': {}
diff --git a/src/features/workspaces/ai/ai-thread-runtime.ts b/src/features/workspaces/ai/ai-thread-runtime.ts
index b0134c73c..9897f94a7 100644
--- a/src/features/workspaces/ai/ai-thread-runtime.ts
+++ b/src/features/workspaces/ai/ai-thread-runtime.ts
@@ -325,6 +325,17 @@ function getWorkspaceAiLanguageModelForGatewayModel(
 function getWorkspaceAiGatewayTransportOptions() {
 	return {
 		caching: "auto" as const,
+		// Buy the fast lane where it exists. The gateway only forwards a tier to
+		// OpenAI, Google AI Studio, and Vertex, so this is a no-op on the Claude
+		// primaries and moves the models we actually default to (`auto`/luna, the
+		// Gemini pair, the nano/flash-lite title legs). It is a hint, never a
+		// promise: an unsupported model ignores it, and a provider that is out of
+		// priority capacity silently downgrades to standard and bills standard.
+		// Priority runs ~1.8-2x standard token price when it *is* granted, which
+		// the `cost` ladder in models.ts does not account for — read
+		// `service_tier` in PostHog before trusting those multipliers, since a
+		// missing value means we paid standard and got standard.
+		serviceTier: "priority" as const,
 		// Time-to-first-token budget before a BYOK leg is abandoned for the next
 		// provider — and eventually for Vercel's own credits. A flat 8s evicted
 		// healthy requests: 37% of gemini-3.1-pro steps and 29% of sonnet steps
diff --git a/src/features/workspaces/cache-page.test.ts b/src/features/workspaces/cache-page.test.ts
new file mode 100644
index 000000000..fc9b24ea5
--- /dev/null
+++ b/src/features/workspaces/cache-page.test.ts
@@ -0,0 +1,87 @@
+import { QueryClient } from "@tanstack/react-query";
+import { describe, expect, it, vi } from "vitest";
+
+import { workspacePageQueryKey } from "#/features/workspaces/cache-keys";
+import { applyWorkspacePageDeltaToCache } from "#/features/workspaces/cache-page";
+import type { WorkspaceItemSummary, WorkspacePage } from "#/features/workspaces/contracts";
+
+describe("workspace page cache ordering", () => {
+	it("applies only the next revision", () => {
+		const queryClient = createQueryClient(createPage(3, createItem({ name: "Before" })));
+
+		applyWorkspacePageDeltaToCache(queryClient, {
+			type: "workspace.items.upserted",
+			workspaceId: "workspace-1",
+			revision: 4,
+			items: [createItem({ name: "After" })],
+		});
+
+		expect(readPage(queryClient)).toMatchObject({
+			items: [{ name: "After" }],
+			revision: 4,
+		});
+	});
+
+	it("ignores stale revisions", () => {
+		const queryClient = createQueryClient(createPage(3, createItem({ name: "Current" })));
+		const invalidate = vi.spyOn(queryClient, "invalidateQueries").mockResolvedValue();
+
+		applyWorkspacePageDeltaToCache(queryClient, {
+			type: "workspace.items.upserted",
+			workspaceId: "workspace-1",
+			revision: 2,
+			items: [createItem({ name: "Stale" })],
+		});
+
+		expect(readItem(queryClient)).toMatchObject({ name: "Current" });
+		expect(invalidate).not.toHaveBeenCalled();
+	});
+
+	it("keeps current cache data and reconciles a revision gap", () => {
+		const queryClient = createQueryClient(createPage(3, createItem({ name: "Newer" })));
+		const invalidate = vi.spyOn(queryClient, "invalidateQueries").mockResolvedValue();
+
+		applyWorkspacePageDeltaToCache(queryClient, {
+			type: "workspace.items.upserted",
+			workspaceId: "workspace-1",
+			revision: 5,
+			items: [createItem({ name: "Older" })],
+		});
+
+		expect(readItem(queryClient)).toMatchObject({ name: "Newer" });
+		expect(invalidate).toHaveBeenCalledWith({ queryKey: workspacePageQueryKey("workspace-1") });
+	});
+});
+
+function createQueryClient(page: WorkspacePage) {
+	const queryClient = new QueryClient();
+	queryClient.setQueryData(workspacePageQueryKey("workspace-1"), page);
+	return queryClient;
+}
+
+function readItem(queryClient: QueryClient) {
+	return readPage(queryClient)?.items[0];
+}
+
+function readPage(queryClient: QueryClient) {
+	return queryClient.getQueryData<WorkspacePage>(workspacePageQueryKey("workspace-1"));
+}
+
+function createPage(revision: number, item: WorkspaceItemSummary): WorkspacePage {
+	return { workspace: {} as WorkspacePage["workspace"], items: [item], revision };
+}
+
+function createItem(input: Partial<WorkspaceItemSummary> = {}): WorkspaceItemSummary {
+	return {
+		color: input.color ?? null,
+		createdAt: "2026-01-01T00:00:00.000Z",
+		id: "folder-1",
+		metadataJson: {},
+		name: input.name ?? "Folder",
+		parentId: null,
+		sortOrder: 1,
+		type: "folder",
+		updatedAt: "2026-01-01T00:00:00.000Z",
+		workspaceId: "workspace-1",
+	};
+}
diff --git a/src/features/workspaces/cache-page.ts b/src/features/workspaces/cache-page.ts
index 744f48201..dfcf4165f 100644
--- a/src/features/workspaces/cache-page.ts
+++ b/src/features/workspaces/cache-page.ts
@@ -3,15 +3,40 @@ import { workspacePageQueryKey } from "#/features/workspaces/cache-keys";
 import type {
 	CreateWorkspaceItemInput,
 	MoveWorkspaceItemsInput,
-	UpdateWorkspaceItemColorInput,
 	WorkspacePage,
 } from "#/features/workspaces/contracts";
 import {
 	createWorkspaceItemInPage,
 	moveWorkspaceItemsInPage,
 	removeWorkspaceItemsFromPage,
-	updateWorkspaceItemColorInPage,
+	upsertWorkspaceItemInPage,
 } from "#/features/workspaces/model/workspace-page";
+import type { WorkspacePageDelta } from "#/features/workspaces/realtime/messages";
+
+export function applyWorkspacePageDeltaToCache(
+	queryClient: QueryClient,
+	change: WorkspacePageDelta,
+) {
+	let shouldReconcile = false;
+	queryClient.setQueryData<WorkspacePage>(workspacePageQueryKey(change.workspaceId), (current) => {
+		if (!current) return current;
+		if (change.revision <= current.revision) return current;
+		if (change.revision !== current.revision + 1) {
+			shouldReconcile = true;
+			return current;
+		}
+		if (change.type === "workspace.items.deleted") {
+			return removeWorkspaceItemsFromPage(current, change.itemIds, change.revision);
+		}
+		return change.items.reduce(
+			(page, item) => upsertWorkspaceItemInPage(page, item, change.revision),
+			current,
+		);
+	});
+	if (shouldReconcile) {
+		void queryClient.invalidateQueries({ queryKey: workspacePageQueryKey(change.workspaceId) });
+	}
+}
 
 export function createWorkspaceItemInPageCache(
 	queryClient: QueryClient,
@@ -40,31 +65,3 @@ export function removeWorkspaceItemsFromPageCache(
 		current ? removeWorkspaceItemsFromPage(current, itemIds) : current,
 	);
 }
-
-export function updateWorkspaceItemColorInPageCache(
-	queryClient: QueryClient,
-	input: UpdateWorkspaceItemColorInput,
-) {
-	queryClient.setQueryData<WorkspacePage>(workspacePageQueryKey(input.workspaceId), (current) => {
-		if (!current) {
-			return current;
-		}
-
-		const updateResult = updateWorkspaceItemColorInPage(current, input);
-
-		if (!updateResult) {
-			return current;
-		}
-
-		return updateResult;
-	});
-}
-
-export function getWorkspaceItemColorInPageCache(
-	queryClient: QueryClient,
-	input: Pick<UpdateWorkspaceItemColorInput, "itemId" | "workspaceId">,
-) {
-	const page = queryClient.getQueryData<WorkspacePage>(workspacePageQueryKey(input.workspaceId));
-
-	return page?.items.find((item) => item.id === input.itemId)?.color ?? null;
-}
diff --git a/src/features/workspaces/cache-workspace.ts b/src/features/workspaces/cache-workspace.ts
index d569f8505..722503ce3 100644
--- a/src/features/workspaces/cache-workspace.ts
+++ b/src/features/workspaces/cache-workspace.ts
@@ -38,14 +38,12 @@ export function setWorkspacePageCache(
 	input: {
 		workspace: WorkspaceSummary;
 		items: WorkspaceItemSummary[];
-		itemFacts: WorkspacePage["itemFacts"];
 		revision: number;
 	},
 ) {
 	queryClient.setQueryData<WorkspacePage>(workspacePageQueryKey(input.workspace.id), {
 		workspace: input.workspace,
 		items: input.items,
-		itemFacts: input.itemFacts,
 		revision: input.revision,
 	});
 }
diff --git a/src/features/workspaces/components/WorkspaceFileUploadProvider.tsx b/src/features/workspaces/components/WorkspaceFileUploadProvider.tsx
index 7511a8500..3c3d3b2ac 100644
--- a/src/features/workspaces/components/WorkspaceFileUploadProvider.tsx
+++ b/src/features/workspaces/components/WorkspaceFileUploadProvider.tsx
@@ -14,7 +14,7 @@ import {
 } from "#/components/ui/alert-dialog";
 import { useBillingState } from "#/features/account/use-billing-state";
 import { showUpgradeDialog } from "#/features/account/upgrade-navigation";
-import { workspacePageQueryKey } from "#/features/workspaces/cache";
+import { applyWorkspacePageDeltaToCache } from "#/features/workspaces/cache";
 import { useWorkspaceMutationAccess } from "#/features/workspaces/components/workspace-mutation-access";
 import { runWorkspaceFileUploadBatch } from "#/features/workspaces/files/workspace-file-upload";
 import { workspaceUploadAccept } from "#/features/workspaces/upload/workspace-upload-intake";
@@ -57,8 +57,13 @@ export function WorkspaceFileUploadProvider({
 			parentId,
 			files: fileList,
 			onLimitReached: setLimitResult,
-			onSuccess: () => {
-				void queryClient.invalidateQueries({ queryKey: workspacePageQueryKey(workspaceId) });
+			onSuccess: (command) => {
+				applyWorkspacePageDeltaToCache(queryClient, {
+					type: "workspace.items.upserted",
+					workspaceId,
+					items: [command.result],
+					revision: command.revision,
+				});
 			},
 		});
 	};
diff --git a/src/features/workspaces/components/WorkspaceItemActionsMenu.tsx b/src/features/workspaces/components/WorkspaceItemActionsMenu.tsx
index 6610893f3..93d36bb30 100644
--- a/src/features/workspaces/components/WorkspaceItemActionsMenu.tsx
+++ b/src/features/workspaces/components/WorkspaceItemActionsMenu.tsx
@@ -113,7 +113,7 @@ export function WorkspaceItemActionsMenuContent({
 				<WorkspaceItemColorSubmenu
 					item={item}
 					menuKind={menuKind}
-					readOnly={readOnly}
+					disabled={readOnly || updateWorkspaceItemColorMutation.isPending}
 					onUpdateItemColor={(color) =>
 						updateWorkspaceItemColorMutation.mutate({
 							workspaceId: item.workspaceId,
@@ -193,12 +193,12 @@ function WorkspaceItemRenameMenuItem({
 function WorkspaceItemColorSubmenu({
 	item,
 	menuKind,
-	readOnly,
+	disabled,
 	onUpdateItemColor,
 }: {
 	item: WorkspaceItem;
 	menuKind: "dropdown" | "context";
-	readOnly: boolean;
+	disabled: boolean;
 	onUpdateItemColor: (color: WorkspaceItemColor) => void;
 }) {
 	const selectedColor = getWorkspaceItemColorValue(item.color);
@@ -210,14 +210,14 @@ function WorkspaceItemColorSubmenu({
 			onValueChange={onUpdateItemColor}
 			showLabels={false}
 			className="grid-flow-col grid-rows-4 gap-1.5"
-			disabled={readOnly}
+			disabled={disabled}
 		/>
 	);
 
 	if (menuKind === "context") {
 		return (
 			<ContextMenuSub>
-				<ContextMenuSubTrigger disabled={readOnly}>
+				<ContextMenuSubTrigger disabled={disabled}>
 					{workspaceItemColorSubmenuTrigger}
 				</ContextMenuSubTrigger>
 				<ContextMenuSubContent className="max-w-[calc(100vw-2rem)] w-fit overflow-x-auto p-2">
@@ -229,7 +229,7 @@ function WorkspaceItemColorSubmenu({
 
 	return (
 		<DropdownMenuSub>
-			<DropdownMenuSubTrigger disabled={readOnly}>
+			<DropdownMenuSubTrigger disabled={disabled}>
 				{workspaceItemColorSubmenuTrigger}
 			</DropdownMenuSubTrigger>
 			<DropdownMenuSubContent className="max-w-[calc(100vw-2rem)] w-fit overflow-x-auto p-2">
diff --git a/src/features/workspaces/components/WorkspaceLayout.tsx b/src/features/workspaces/components/WorkspaceLayout.tsx
index 71bc894c9..c499bc065 100644
--- a/src/features/workspaces/components/WorkspaceLayout.tsx
+++ b/src/features/workspaces/components/WorkspaceLayout.tsx
@@ -1,6 +1,6 @@
 import { useQueryClient } from "@tanstack/react-query";
 import { useEffect } from "react";
-import { workspacePageQueryKey } from "#/features/workspaces/cache";
+import { applyWorkspacePageDeltaToCache, workspacePageQueryKey } from "#/features/workspaces/cache";
 import AiChatPanel from "#/features/workspaces/components/AiChatPanel";
 import WorkspaceChatLayout from "#/features/workspaces/components/WorkspaceChatLayout";
 import WorkspaceContextBar from "#/features/workspaces/components/WorkspaceContextBar";
@@ -22,11 +22,7 @@ import {
 	useWorkspaceViewPolicy,
 	WorkspaceViewCapabilitiesProvider,
 } from "#/features/workspaces/components/workspace-view-policy";
-import type {
-	WorkspaceItemFacts,
-	WorkspaceItemType,
-	WorkspaceSummary,
-} from "#/features/workspaces/contracts";
+import type { WorkspaceItemType, WorkspaceSummary } from "#/features/workspaces/contracts";
 import type { WorkspaceLocation } from "#/features/workspaces/locations/workspace-location";
 import { WorkspaceLocationProvider } from "#/features/workspaces/locations/workspace-location-context";
 import { DocumentEditReviewProvider } from "#/features/workspaces/documents/document-edit-review-context";
@@ -57,8 +53,6 @@ export type { WorkspaceItem } from "#/features/workspaces/model/types";
 interface WorkspaceShellProps {
 	workspace: WorkspaceSummary;
 	items: WorkspaceItem[];
-	itemFacts: WorkspaceItemFacts[];
-	revision: number;
 	activeTabIdFromUrl?: string;
 	activeViewFromUrl?: string;
 }
@@ -66,8 +60,6 @@ interface WorkspaceShellProps {
 export function WorkspaceShell({
 	workspace,
 	items,
-	itemFacts,
-	revision,
 	activeTabIdFromUrl,
 	activeViewFromUrl,
 }: WorkspaceShellProps) {
@@ -83,8 +75,10 @@ export function WorkspaceShell({
 	const normalizedUiSession = useWorkspaceUiSession(workspace.id);
 	const realtime = useWorkspaceRealtime({
 		workspaceId: workspace.id,
-		lastSeenRevision: revision,
-		onWorkspaceChanged: () => {
+		onPageChange: (change) => {
+			applyWorkspacePageDeltaToCache(queryClient, change);
+		},
+		onDesync: () => {
 			void queryClient.invalidateQueries({
 				queryKey: workspacePageQueryKey(workspace.id),
 			});
@@ -183,7 +177,6 @@ export function WorkspaceShell({
 		activeItem: isWorkspaceItemView(activeItem) ? activeItem : undefined,
 		activeTabId: activeTab.id,
 		itemViewStatesByItemId,
-		itemFactsById: new Map(itemFacts.map((item) => [item.itemId, item])),
 		itemsById,
 		presentation,
 		selectedItemIds,
diff --git a/src/features/workspaces/components/WorkspacePageRoute.tsx b/src/features/workspaces/components/WorkspacePageRoute.tsx
index 450979b14..d21148cbf 100644
--- a/src/features/workspaces/components/WorkspacePageRoute.tsx
+++ b/src/features/workspaces/components/WorkspacePageRoute.tsx
@@ -75,8 +75,6 @@ export default function WorkspacePageRoute() {
 			activeTabIdFromUrl={tab}
 			activeViewFromUrl={view}
 			items={page.items}
-			itemFacts={page.itemFacts}
-			revision={page.revision}
 			workspace={page.workspace}
 		/>
 	);
diff --git a/src/features/workspaces/contracts.ts b/src/features/workspaces/contracts.ts
index f4b3b674c..82f8c03bc 100644
--- a/src/features/workspaces/contracts.ts
+++ b/src/features/workspaces/contracts.ts
@@ -348,12 +348,6 @@ export const workspaceSummarySchema = z.object({
 	membershipRole: workspaceMembershipRoleSchema,
 });
 
-export const workspaceItemFactsSchema = z.object({
-	itemId: z.string(),
-	pageCount: z.number().int().positive().optional(),
-	relationshipCount: z.number().int().nonnegative(),
-});
-
 export const workspaceItemSummarySchema = z.object({
 	id: z.string(),
 	workspaceId: z.string(),
@@ -448,7 +442,6 @@ export const workspaceIdInputSchema = z.object({
 export const workspacePageSchema = z.object({
 	workspace: workspaceSummarySchema,
 	items: z.array(workspaceItemSummarySchema),
-	itemFacts: z.array(workspaceItemFactsSchema),
 	revision: z.number().int().nonnegative(),
 });
 
@@ -457,7 +450,6 @@ export type WorkspaceColor = z.infer<typeof workspaceColorSchema>;
 export type WorkspaceItemColor = z.infer<typeof workspaceColorSchema>;
 export type WorkspaceSummary = z.infer<typeof workspaceSummarySchema>;
 export type WorkspaceDetail = WorkspaceSummary;
-export type WorkspaceItemFacts = z.infer<typeof workspaceItemFactsSchema>;
 export type WorkspaceItemSummary = z.infer<typeof workspaceItemSummarySchema>;
 export type CreateWorkspaceItemInput = z.infer<typeof createWorkspaceItemInputSchema>;
 export type RenameWorkspaceItemInput = z.infer<typeof renameWorkspaceItemInputSchema>;
diff --git a/src/features/workspaces/kernel/workspace-kernel-access.ts b/src/features/workspaces/kernel/workspace-kernel-access.ts
index d54c725a9..2926ad70f 100644
--- a/src/features/workspaces/kernel/workspace-kernel-access.ts
+++ b/src/features/workspaces/kernel/workspace-kernel-access.ts
@@ -5,7 +5,6 @@ import type {
 	MoveWorkspaceItemsInput,
 	RenameWorkspaceItemInput,
 	UpdateWorkspaceItemColorInput,
-	WorkspaceItemFacts,
 	WorkspaceItemSummary,
 } from "#/features/workspaces/contracts";
 import {
@@ -50,15 +49,12 @@ export interface WorkspaceKernelClient {
 	getPage(input?: { userId?: string }): Promise<{
 		workspaceId: string;
 		items: WorkspaceItemSummary[];
-		itemFacts: WorkspaceItemFacts[];
 		revision: number;
 	}>;
 	listTreeItems(input?: ListWorkspaceKernelItemsArgs): Promise<ListWorkspaceKernelItemsResult>;
 	resolvePaths(input: ResolveWorkspaceKernelPathsArgs): Promise<WorkspaceKernelPathResolution[]>;
 	getItemPaths(input: GetWorkspaceKernelItemPathsArgs): Promise<WorkspaceKernelItemPath[]>;
-	linkItems(
-		input: LinkWorkspaceKernelItemsArgs,
-	): Promise<WorkspaceCommandResult<WorkspaceItemFacts[]>>;
+	linkItems(input: LinkWorkspaceKernelItemsArgs): Promise<void>;
 	listItemRelations(
 		input: ListWorkspaceKernelItemRelationsArgs,
 	): Promise<WorkspaceKernelItemRelation[]>;
diff --git a/src/features/workspaces/kernel/workspace-kernel-list.ts b/src/features/workspaces/kernel/workspace-kernel-list.ts
index 3c4b4f383..0707a9db5 100644
--- a/src/features/workspaces/kernel/workspace-kernel-list.ts
+++ b/src/features/workspaces/kernel/workspace-kernel-list.ts
@@ -1,8 +1,4 @@
-import type {
-	WorkspaceItemFacts,
-	WorkspaceItemSummary,
-	WorkspaceItemType,
-} from "#/features/workspaces/contracts";
+import type { WorkspaceItemSummary, WorkspaceItemType } from "#/features/workspaces/contracts";
 import {
 	joinWorkspacePathSegment,
 	resolveWorkspaceKernelCwd,
@@ -25,9 +21,7 @@ export interface ListWorkspaceKernelItemsResult {
 
 export interface ListWorkspaceKernelItem {
 	modifiedAt: string;
-	pageCount?: number;
 	path: string;
-	relationshipCount: number;
 	type: WorkspaceItemType | WorkspaceFileAssetKind;
 }
 
@@ -50,18 +44,13 @@ interface WorkspaceKernelListRow {
 }
 
 export function listWorkspaceKernelTreeItems(input: {
-	getItemFacts: (items: WorkspaceItemSummary[]) => WorkspaceItemFacts[];
 	tree: WorkspaceKernelTree;
 	offset?: number;
 	path?: string;
 	recursive?: boolean;
 	limit?: number;
 }): ListWorkspaceKernelItemsResult {
-	const selection = selectWorkspaceKernelTreeItems(input);
-	return formatWorkspaceKernelListSelection(
-		selection,
-		input.getItemFacts(selection.rows.map((row) => row.item)),
-	);
+	return formatWorkspaceKernelListSelection(selectWorkspaceKernelTreeItems(input));
 }
 
 function selectWorkspaceKernelTreeItems(input: {
@@ -112,14 +101,11 @@ function selectWorkspaceKernelTreeItems(input: {
 
 function formatWorkspaceKernelListSelection(
 	selection: WorkspaceKernelListSelection,
-	itemFacts: WorkspaceItemFacts[],
 ): ListWorkspaceKernelItemsResult {
-	const itemFactsById = new Map(itemFacts.map((facts) => [facts.itemId, facts]));
 	return {
 		failed: selection.failed,
 		items: selection.rows.map((row) =>
 			formatWorkspaceKernelListItem({
-				facts: itemFactsById.get(row.item.id),
 				item: row.item,
 				path: row.path,
 			}),
@@ -180,15 +166,12 @@ function collectWorkspaceKernelListRows({
 }
 
 function formatWorkspaceKernelListItem(input: {
-	facts?: WorkspaceItemFacts;
 	item: WorkspaceItemSummary;
 	path: string;
 }): ListWorkspaceKernelItem {
 	return {
 		modifiedAt: input.item.updatedAt,
-		...(input.facts?.pageCount ? { pageCount: input.facts.pageCount } : {}),
 		path: input.path,
-		relationshipCount: input.facts?.relationshipCount ?? 0,
 		type: resolveWorkspaceFileTypeFromItem(input.item)?.assetKind ?? input.item.type,
 	};
 }
diff --git a/src/features/workspaces/kernel/workspace-kernel.ts b/src/features/workspaces/kernel/workspace-kernel.ts
index 3c922bb41..644b95d29 100644
--- a/src/features/workspaces/kernel/workspace-kernel.ts
+++ b/src/features/workspaces/kernel/workspace-kernel.ts
@@ -10,7 +10,7 @@ import {
 import type { ResourcePurgeResult } from "#/features/workspaces/resource-purge-result";
 import type {
 	WorkspaceConnectionState,
-	WorkspaceRevision,
+	WorkspacePageChange,
 	WorkspaceRealtimeServerMessage,
 } from "#/features/workspaces/realtime/messages";
 import { recordOperationalFailure } from "#/integrations/observability/operational-events";
@@ -23,7 +23,7 @@ export { setWorkspaceKernelUserHeaders };
 /**
  * The deployed class name is retained to avoid a destructive Durable Object
  * migration. Canonical workspace data lives in Postgres; this object is only a
- * live room for presence, revision notifications, and retryable remote cleanup.
+ * live room for presence, workspace-page deltas, and retryable remote cleanup.
  */
 export class WorkspaceKernel extends Agent<Cloudflare.Env> {
 	onConnect(connection: Connection<WorkspaceConnectionState>, context: ConnectionContext) {
@@ -42,16 +42,12 @@ export class WorkspaceKernel extends Agent<Cloudflare.Env> {
 		this.broadcastPresenceSnapshot();
 	}
 
-	async publishWorkspaceChange(change: WorkspaceRevision): Promise<void> {
+	async publishWorkspacePageChange(change: WorkspacePageChange): Promise<void> {
 		if (change.workspaceId !== this.name) {
 			throw new Error("Workspace change was routed to the wrong room.");
 		}
 
-		this.broadcastRealtimeMessage({
-			type: "workspace.changed",
-			workspaceId: this.name,
-			revision: change.revision,
-		});
+		this.broadcastRealtimeMessage(change);
 	}
 
 	async disconnectMember(input: { userId: string; documentItemIds: string[] }): Promise<void> {
diff --git a/src/features/workspaces/model/workspace-ai-context-outline.ts b/src/features/workspaces/model/workspace-ai-context-outline.ts
index 9620e7060..f927292f4 100644
--- a/src/features/workspaces/model/workspace-ai-context-outline.ts
+++ b/src/features/workspaces/model/workspace-ai-context-outline.ts
@@ -59,13 +59,9 @@ function getWorkspaceAiContextOutlineRows(
 			throw new Error("Workspace outline path index returned an unknown item.");
 		}
 
-		const facts = context.itemFactsById.get(item.id);
-
 		return {
 			item,
 			outlineItem: {
-				...(facts?.pageCount ? { pageCount: facts.pageCount } : {}),
-				relationshipCount: facts?.relationshipCount ?? 0,
 				...(item.type === "folder"
 					? {
 							childCount: childCountsByItemId.get(item.id) ?? 0,
diff --git a/src/features/workspaces/model/workspace-ai-context-prompt.ts b/src/features/workspaces/model/workspace-ai-context-prompt.ts
index fd0f0cfe6..54d459768 100644
--- a/src/features/workspaces/model/workspace-ai-context-prompt.ts
+++ b/src/features/workspaces/model/workspace-ai-context-prompt.ts
@@ -106,14 +106,7 @@ function formatWorkspaceAiContextOutlineItemMeta(item: WorkspaceAiContextOutline
 			? ""
 			: `, ${item.childCount} direct ${item.childCount === 1 ? "child" : "children"}, ${item.descendantCount} total ${item.descendantCount === 1 ? "descendant" : "descendants"}`;
 
-	const pages = item.pageCount
-		? `, ${item.pageCount} ${item.pageCount === 1 ? "page" : "pages"}`
-		: "";
-	const relationships = item.relationshipCount
-		? `, ${item.relationshipCount} ${item.relationshipCount === 1 ? "relationship" : "relationships"}`
-		: "";
-
-	return `${item.type}${pages}${relationships}${counts}`;
+	return `${item.type}${counts}`;
 }
 
 function limitWorkspaceAiContextOutlineLines(lines: string[]) {
diff --git a/src/features/workspaces/model/workspace-ai-context-types.ts b/src/features/workspaces/model/workspace-ai-context-types.ts
index e56fa2bf0..211dfebda 100644
--- a/src/features/workspaces/model/workspace-ai-context-types.ts
+++ b/src/features/workspaces/model/workspace-ai-context-types.ts
@@ -1,6 +1,5 @@
 import type { WorkspaceTab } from "#/features/workspaces/model/tab-types";
 import type { WorkspaceItem } from "#/features/workspaces/model/types";
-import type { WorkspaceItemFacts } from "#/features/workspaces/contracts";
 import type {
 	WorkspaceAiContextItemViewState,
 	WorkspaceItemViewState,
@@ -12,7 +11,6 @@ export type WorkspaceAiContextScope = {
 	activeItem?: WorkspaceItem;
 	activeTabId?: string;
 	itemViewStatesByItemId: Readonly<Record<string, WorkspaceItemViewState | undefined>>;
-	itemFactsById: ReadonlyMap<string, WorkspaceItemFacts>;
 	itemsById: ReadonlyMap<string, WorkspaceItem>;
 	presentation: WorkspacePresentation;
 	selectedItemIds: readonly string[];
@@ -55,9 +53,7 @@ export type WorkspaceAiContextOutline =
 export type WorkspaceAiContextOutlineItem = {
 	childCount?: number;
 	descendantCount?: number;
-	pageCount?: number;
 	path: string;
-	relationshipCount: number;
 	type: string;
 };
 
diff --git a/src/features/workspaces/model/workspace-ai-context-validation.ts b/src/features/workspaces/model/workspace-ai-context-validation.ts
index be4d4a0ab..dc6141ca1 100644
--- a/src/features/workspaces/model/workspace-ai-context-validation.ts
+++ b/src/features/workspaces/model/workspace-ai-context-validation.ts
@@ -84,8 +84,6 @@ function isWorkspaceAiContextOutlineItem(value: unknown) {
 	return (
 		typeof value.path === "string" &&
 		typeof value.type === "string" &&
-		(value.pageCount === undefined || isPositiveInteger(value.pageCount)) &&
-		isNonNegativeInteger(value.relationshipCount) &&
 		hasChildCount === hasDescendantCount &&
 		(value.childCount === undefined || isNonNegativeInteger(value.childCount)) &&
 		(value.descendantCount === undefined || isNonNegativeInteger(value.descendantCount))
@@ -96,10 +94,6 @@ function isNonNegativeInteger(value: unknown) {
 	return typeof value === "number" && Number.isInteger(value) && value >= 0;
 }
 
-function isPositiveInteger(value: unknown) {
-	return typeof value === "number" && Number.isInteger(value) && value > 0;
-}
-
 function isWorkspaceAiContextSelectedItem(value: unknown): value is WorkspaceAiContextSelectedItem {
 	if (!isRecord(value) || !isWorkspaceAiContextItemReference(value)) {
 		return false;
diff --git a/src/features/workspaces/model/workspace-page.test.ts b/src/features/workspaces/model/workspace-page.test.ts
index f57de50ee..bed656837 100644
--- a/src/features/workspaces/model/workspace-page.test.ts
+++ b/src/features/workspaces/model/workspace-page.test.ts
@@ -13,18 +13,11 @@ describe("removeWorkspaceItemsFromPage", () => {
 				createItem({ id: "grandchild", parentId: "child" }),
 				createItem({ id: "sibling" }),
 			],
-			itemFacts: [
-				{ itemId: "folder", relationshipCount: 0 },
-				{ itemId: "child", relationshipCount: 0 },
-				{ itemId: "grandchild", relationshipCount: 0 },
-				{ itemId: "sibling", relationshipCount: 0 },
-			],
 			revision: 1,
 		} satisfies WorkspacePage;
 
 		expect(removeWorkspaceItemsFromPage(page, ["folder"])).toMatchObject({
 			items: [{ id: "sibling" }],
-			itemFacts: [{ itemId: "sibling" }],
 		});
 	});
 });
diff --git a/src/features/workspaces/model/workspace-page.ts b/src/features/workspaces/model/workspace-page.ts
index 2d236e4b3..74212f118 100644
--- a/src/features/workspaces/model/workspace-page.ts
+++ b/src/features/workspaces/model/workspace-page.ts
@@ -1,7 +1,6 @@
 import type {
 	CreateWorkspaceItemInput,
 	MoveWorkspaceItemsInput,
-	UpdateWorkspaceItemColorInput,
 	WorkspaceItemSummary,
 	WorkspacePage,
 } from "#/features/workspaces/contracts";
@@ -116,23 +115,6 @@ export function moveWorkspaceItemsInPage(
 	return nextPage;
 }
 
-export function updateWorkspaceItemColorInPage(
-	page: WorkspacePage,
-	input: UpdateWorkspaceItemColorInput,
-): WorkspacePage | null {
-	const previousItem = page.items.find((item) => item.id === input.itemId);
-
-	if (!previousItem) {
-		return null;
-	}
-
-	return upsertWorkspaceItemInPage(page, {
-		...previousItem,
-		color: input.color,
-		updatedAt: new Date().toISOString(),
-	});
-}
-
 export function upsertWorkspaceItemInPage(
 	page: WorkspacePage,
 	item: WorkspaceItemSummary,
@@ -161,7 +143,6 @@ export function removeWorkspaceItemsFromPage(
 		...page,
 		revision: Math.max(page.revision, revision),
 		items: page.items.filter((item) => !deletedIds.has(item.id)),
-		itemFacts: page.itemFacts.filter((facts) => !deletedIds.has(facts.itemId)),
 	};
 }
 
diff --git a/src/features/workspaces/operations/workspace-tool-schemas.ts b/src/features/workspaces/operations/workspace-tool-schemas.ts
index f1c34a35c..25f88e8e0 100644
--- a/src/features/workspaces/operations/workspace-tool-schemas.ts
+++ b/src/features/workspaces/operations/workspace-tool-schemas.ts
@@ -71,9 +71,7 @@ const workspacePathItemSchema = z.object({
 
 const workspaceListItemSchema = z.object({
 	modifiedAt: z.string(),
-	pageCount: z.number().int().positive().optional(),
 	path: workspacePathSchema,
-	relationshipCount: z.number().int().nonnegative(),
 	type: z.union([workspaceItemTypeSchema, workspaceFileAssetKindSchema]),
 });
 
diff --git a/src/features/workspaces/persistence/workspace-postgres-documents.ts b/src/features/workspaces/persistence/workspace-postgres-documents.ts
index b083926e8..f6bc033cd 100644
--- a/src/features/workspaces/persistence/workspace-postgres-documents.ts
+++ b/src/features/workspaces/persistence/workspace-postgres-documents.ts
@@ -6,7 +6,7 @@ import type {
 	ReadWorkspaceDocumentCheckpointArgs,
 	WorkspaceKernelPublishOutcome,
 } from "#/features/workspaces/kernel/workspace-kernel-types";
-import type { WorkspaceRevision } from "#/features/workspaces/realtime/messages";
+import type { WorkspacePageDelta } from "#/features/workspaces/realtime/messages";
 import {
 	getActiveWorkspaceItemRow,
 	lockWorkspaceForActor,
@@ -20,7 +20,7 @@ import {
 export class PostgresWorkspaceDocuments {
 	constructor(
 		private readonly workspaceId: string,
-		private readonly onChange?: (change: WorkspaceRevision) => Promise<void>,
+		private readonly onChange?: (change: WorkspacePageDelta) => Promise<void>,
 	) {}
 
 	async readCheckpoint(input: ReadWorkspaceDocumentCheckpointArgs) {
@@ -69,11 +69,17 @@ export class PostgresWorkspaceDocuments {
 				.update(workspaceItems)
 				.set({ metadata, updatedAt: now })
 				.where(eq(workspaceItems.id, input.itemId));
+			const item = await requireActiveWorkspaceItem(transaction, this.workspaceId, input.itemId);
 			const revision = await nextWorkspaceRevision(transaction, this.workspaceId);
-			return { outcome: "applied" as const, revision };
+			return { outcome: "applied" as const, item, revision };
 		});
 		if (publication.outcome === "applied") {
-			await this.onChange?.({ workspaceId: this.workspaceId, revision: publication.revision });
+			await this.onChange?.({
+				type: "workspace.items.upserted",
+				workspaceId: this.workspaceId,
+				revision: publication.revision,
+				items: [publication.item],
+			});
 		}
 		return publication.outcome;
 	}
diff --git a/src/features/workspaces/persistence/workspace-postgres-files.ts b/src/features/workspaces/persistence/workspace-postgres-files.ts
index f9ba59b70..781b9b5a5 100644
--- a/src/features/workspaces/persistence/workspace-postgres-files.ts
+++ b/src/features/workspaces/persistence/workspace-postgres-files.ts
@@ -24,7 +24,7 @@ import {
 } from "#/features/workspaces/model/workspace-file";
 import type {
 	WorkspaceCommandResult,
-	WorkspaceRevision,
+	WorkspacePageDelta,
 } from "#/features/workspaces/realtime/messages";
 import { assertCanReadWorkspace } from "#/features/workspaces/server/permissions";
 import {
@@ -47,7 +47,7 @@ export class PostgresWorkspaceFiles {
 	constructor(
 		private readonly workspaceId: string,
 		private readonly bucket: R2Bucket,
-		private readonly onChange?: (change: WorkspaceRevision) => Promise<void>,
+		private readonly onChange?: (change: WorkspacePageDelta) => Promise<void>,
 	) {}
 
 	async createFileFromUpload(
@@ -125,7 +125,12 @@ export class PostgresWorkspaceFiles {
 			const revision = await nextWorkspaceRevision(transaction, this.workspaceId);
 			return { result: item, revision };
 		});
-		await this.notify(command.revision);
+		await this.onChange?.({
+			type: "workspace.items.upserted",
+			workspaceId: this.workspaceId,
+			revision: command.revision,
+			items: [command.result],
+		});
 		return command;
 	}
 
@@ -223,10 +228,8 @@ export class PostgresWorkspaceFiles {
 						updatedAt: now,
 					},
 				});
-			const revision = await nextWorkspaceRevision(transaction, this.workspaceId);
-			return { outcome: "applied" as const, revision };
+			return { outcome: "applied" as const };
 		});
-		if (publication.outcome === "applied") await this.notify(publication.revision);
 		return publication.outcome;
 	}
 
@@ -310,10 +313,8 @@ export class PostgresWorkspaceFiles {
 						updatedAt: now,
 					},
 				});
-			const revision = await nextWorkspaceRevision(transaction, this.workspaceId);
-			return { outcome: "applied" as const, revision };
+			return { outcome: "applied" as const };
 		});
-		if (publication.outcome === "applied") await this.notify(publication.revision);
 		return publication.outcome;
 	}
 
@@ -337,8 +338,4 @@ export class PostgresWorkspaceFiles {
 				.orderBy(asc(workspaceItemPages.pageNumber));
 		});
 	}
-
-	private async notify(revision: number) {
-		await this.onChange?.({ workspaceId: this.workspaceId, revision });
-	}
 }
diff --git a/src/features/workspaces/persistence/workspace-postgres-persistence.ts b/src/features/workspaces/persistence/workspace-postgres-persistence.ts
index 7b08abbef..eb22d8508 100644
--- a/src/features/workspaces/persistence/workspace-postgres-persistence.ts
+++ b/src/features/workspaces/persistence/workspace-postgres-persistence.ts
@@ -42,7 +42,7 @@ import {
 } from "#/features/workspaces/model/workspace-item-colors";
 import type {
 	WorkspaceCommandResult,
-	WorkspaceRevision,
+	WorkspacePageDelta,
 } from "#/features/workspaces/realtime/messages";
 import { assertCanReadWorkspace } from "#/features/workspaces/server/permissions";
 import { PostgresWorkspaceDocuments } from "./workspace-postgres-documents";
@@ -52,9 +52,9 @@ import {
 	collectDescendants,
 	getActiveWorkspaceItemRows,
 	getNextWorkspaceSortOrder,
-	getWorkspaceItemFacts,
 	getActiveWorkspaceItemRow,
 	getWorkspaceItemsByIds,
+	getWorkspaceRevision,
 	hasSelectedAncestor,
 	isDescendantOf,
 	lockWorkspaceForActor,
@@ -71,8 +71,8 @@ import {
 /**
  * Postgres implementation of the existing workspace-kernel persistence surface.
  *
- * Mutations commit a workspace revision atomically, then publish that revision
- * as a cache-invalidation hint through the injected callback.
+ * Page-affecting mutations commit a workspace revision atomically, then publish
+ * their canonical cache delta through the injected callback.
  */
 export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 	private readonly files: PostgresWorkspaceFiles;
@@ -81,7 +81,7 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 	constructor(
 		private readonly workspaceId: string,
 		bucket: R2Bucket,
-		private readonly onChange?: (change: WorkspaceRevision) => Promise<void>,
+		private readonly onChange?: (change: WorkspacePageDelta) => Promise<void>,
 		private readonly onItemsDeleted?: (input: {
 			workspaceId: string;
 			documentItemIds: string[];
@@ -111,12 +111,9 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 
 	async listTreeItems(input: ListWorkspaceKernelItemsArgs = {}) {
 		const page = await this.getPage();
-		const factsById = new Map(page.itemFacts.map((facts) => [facts.itemId, facts]));
 		return listWorkspaceKernelTreeItems({
 			...input,
 			tree: buildWorkspaceKernelTree(page.items),
-			getItemFacts: (items) =>
-				items.map((item) => factsById.get(item.id) ?? { itemId: item.id, relationshipCount: 0 }),
 		});
 	}
 
@@ -178,7 +175,7 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 	}
 
 	async linkItems(input: LinkWorkspaceKernelItemsArgs) {
-		const command = await withWorkspaceTransaction(async (transaction) => {
+		await withWorkspaceTransaction(async (transaction) => {
 			await lockWorkspaceForActor(transaction, this.workspaceId, input.actorUserId);
 			const itemIds = Array.from(
 				new Set(input.relations.flatMap((relation) => [relation.fromItemId, relation.toItemId])),
@@ -202,14 +199,7 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 					)
 					.onConflictDoNothing();
 			}
-
-			const summaries = await getWorkspaceItemsByIds(transaction, this.workspaceId, itemIds);
-			const itemFacts = await getWorkspaceItemFacts(transaction, this.workspaceId, summaries);
-			const revision = await nextWorkspaceRevision(transaction, this.workspaceId);
-			return { result: itemFacts, revision };
 		});
-		await this.notify(command.revision);
-		return command;
 	}
 
 	async createItem(
@@ -293,7 +283,9 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 				},
 			};
 		});
-		if (outcome.status === "applied") await this.notify(outcome.command.revision);
+		if (outcome.status === "applied") {
+			await this.notifyItemsUpserted([outcome.command.result], outcome.command.revision);
+		}
 		return outcome;
 	}
 
@@ -341,7 +333,9 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 				},
 			};
 		});
-		if (outcome.status === "applied") await this.notify(outcome.command.revision);
+		if (outcome.status === "applied") {
+			await this.notifyItemsUpserted([outcome.command.result], outcome.command.revision);
+		}
 		return outcome;
 	}
 
@@ -430,7 +424,9 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 				},
 			};
 		});
-		if (outcome.status === "applied") await this.notify(outcome.command.revision);
+		if (outcome.status === "applied") {
+			await this.notifyItemsUpserted(outcome.command.result, outcome.command.revision);
+		}
 		return outcome;
 	}
 
@@ -451,7 +447,7 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 			const revision = await nextWorkspaceRevision(transaction, this.workspaceId);
 			return { result: item, revision };
 		});
-		await this.notify(command.revision);
+		await this.notifyItemsUpserted([command.result], command.revision);
 		return command;
 	}
 
@@ -477,7 +473,10 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 				await transaction.delete(workspaceItems).where(inArray(workspaceItems.id, rootIds));
 			}
 
-			const revision = await nextWorkspaceRevision(transaction, this.workspaceId);
+			const revision =
+				deleteIds.length > 0
+					? await nextWorkspaceRevision(transaction, this.workspaceId)
+					: await getWorkspaceRevision(transaction, this.workspaceId);
 			const result = { itemIds: rootIds, deletedItemIds: deleteIds };
 			return {
 				result,
@@ -487,12 +486,21 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 			};
 		});
 		await Promise.all([
-			this.notify(command.revision),
-			this.onItemsDeleted?.({
-				workspaceId: this.workspaceId,
-				documentItemIds: command.documentItemIds,
-				fileItemIds: command.fileItemIds,
-			}),
+			command.result.deletedItemIds.length > 0
+				? this.onChange?.({
+						type: "workspace.items.deleted",
+						workspaceId: this.workspaceId,
+						revision: command.revision,
+						itemIds: command.result.deletedItemIds,
+					})
+				: undefined,
+			command.documentItemIds.length > 0 || command.fileItemIds.length > 0
+				? this.onItemsDeleted?.({
+						workspaceId: this.workspaceId,
+						documentItemIds: command.documentItemIds,
+						fileItemIds: command.fileItemIds,
+					})
+				: undefined,
 		]);
 		return { revision: command.revision, result: command.result };
 	}
@@ -531,7 +539,12 @@ export class PostgresWorkspacePersistence implements WorkspaceKernelClient {
 		return await this.files.readPages(input);
 	}
 
-	private async notify(revision: number) {
-		await this.onChange?.({ workspaceId: this.workspaceId, revision });
+	private async notifyItemsUpserted(items: WorkspaceItemSummary[], revision: number) {
+		await this.onChange?.({
+			type: "workspace.items.upserted",
+			workspaceId: this.workspaceId,
+			revision,
+			items,
+		});
 	}
 }
diff --git a/src/features/workspaces/persistence/workspace-postgres-support.ts b/src/features/workspaces/persistence/workspace-postgres-support.ts
index f201203a4..a12c411e8 100644
--- a/src/features/workspaces/persistence/workspace-postgres-support.ts
+++ b/src/features/workspaces/persistence/workspace-postgres-support.ts
@@ -1,17 +1,14 @@
-import { and, asc, eq, inArray, isNull, or, sql } from "drizzle-orm";
+import { and, asc, eq, inArray, isNull, sql } from "drizzle-orm";
 
 import {
 	workspaceFileAssets,
-	workspaceItemPages,
 	workspaceItemExtractions,
-	workspaceItemRelations,
 	workspaceItems,
 	workspaces,
 } from "#/db/schema";
 import { createDbContext, withDb } from "#/db/server";
 import type {
 	JsonValue,
-	WorkspaceItemFacts,
 	WorkspaceItemSummary,
 	WorkspaceItemType,
 } from "#/features/workspaces/contracts";
@@ -60,13 +57,23 @@ export async function lockWorkspaceForActor(
 export async function nextWorkspaceRevision(transaction: Transaction, workspaceId: string) {
 	const [workspace] = await transaction
 		.update(workspaces)
-		.set({ revision: sql`${workspaces.revision} + 1`, updatedAt: new Date() })
+		.set({ revision: sql`${workspaces.revision} + 1` })
 		.where(eq(workspaces.id, workspaceId))
 		.returning({ revision: workspaces.revision });
 	if (!workspace) throw new Error("Workspace not found.");
 	return workspace.revision;
 }
 
+export async function getWorkspaceRevision(db: QueryExecutor, workspaceId: string) {
+	const [workspace] = await db
+		.select({ revision: workspaces.revision })
+		.from(workspaces)
+		.where(eq(workspaces.id, workspaceId))
+		.limit(1);
+	if (!workspace) throw new Error("Workspace not found.");
+	return workspace.revision;
+}
+
 export async function getActiveWorkspaceItemRows(db: QueryExecutor, workspaceId: string) {
 	return await db
 		.select()
@@ -79,20 +86,15 @@ export async function getActiveWorkspaceItems(db: QueryExecutor, workspaceId: st
 	return (await getActiveWorkspaceItemRows(db, workspaceId)).map(mapWorkspaceItem);
 }
 
-export async function readWorkspacePageSnapshot(db: QueryExecutor, workspaceId: string) {
-	const [workspace] = await db
-		.select({ revision: workspaces.revision })
-		.from(workspaces)
-		.where(eq(workspaces.id, workspaceId))
-		.limit(1);
-	if (!workspace) throw new Error("Workspace not found.");
-
+export async function readWorkspacePageSnapshot(db: Transaction, workspaceId: string) {
+	// A transaction owns one pg.Client, so its queries execute serially. Both
+	// callers use repeatable-read transactions to keep these statements coherent.
+	const revision = await getWorkspaceRevision(db, workspaceId);
 	const items = await getActiveWorkspaceItems(db, workspaceId);
 	return {
 		workspaceId,
 		items,
-		itemFacts: await getWorkspaceItemFacts(db, workspaceId, items),
-		revision: workspace.revision,
+		revision,
 	};
 }
 
@@ -144,53 +146,6 @@ export async function getWorkspaceItemsByIds(
 	});
 }
 
-export async function getWorkspaceItemFacts(
-	db: QueryExecutor,
-	workspaceId: string,
-	items: WorkspaceItemSummary[],
-): Promise<WorkspaceItemFacts[]> {
-	if (items.length === 0) return [];
-	const itemIds = items.map((item) => item.id);
-	const [relations, pageCounts] = await Promise.all([
-		db
-			.select({
-				fromItemId: workspaceItemRelations.fromItemId,
-				toItemId: workspaceItemRelations.toItemId,
-			})
-			.from(workspaceItemRelations)
-			.where(
-				and(
-					eq(workspaceItemRelations.workspaceId, workspaceId),
-					or(
-						inArray(workspaceItemRelations.fromItemId, itemIds),
-						inArray(workspaceItemRelations.toItemId, itemIds),
-					),
-				),
-			),
-		db
-			.select({
-				itemId: workspaceItemPages.itemId,
-				pageCount: sql<number>`count(*)::int`,
-			})
-			.from(workspaceItemPages)
-			.where(inArray(workspaceItemPages.itemId, itemIds))
-			.groupBy(workspaceItemPages.itemId),
-	]);
-	const relationCounts = new Map<string, number>();
-	for (const relation of relations) {
-		relationCounts.set(relation.fromItemId, (relationCounts.get(relation.fromItemId) ?? 0) + 1);
-		if (relation.toItemId !== relation.fromItemId) {
-			relationCounts.set(relation.toItemId, (relationCounts.get(relation.toItemId) ?? 0) + 1);
-		}
-	}
-	const countsByItem = new Map(pageCounts.map((row) => [row.itemId, row.pageCount]));
-	return items.map((item) => ({
-		itemId: item.id,
-		...(countsByItem.get(item.id) ? { pageCount: countsByItem.get(item.id) } : {}),
-		relationshipCount: relationCounts.get(item.id) ?? 0,
-	}));
-}
-
 export async function assertWorkspaceParentIsValid(
 	db: QueryExecutor,
 	workspaceId: string,
diff --git a/src/features/workspaces/query-options.ts b/src/features/workspaces/query-options.ts
index 0cadc4f13..01185d896 100644
--- a/src/features/workspaces/query-options.ts
+++ b/src/features/workspaces/query-options.ts
@@ -1,8 +1,10 @@
-import { queryOptions } from "@tanstack/react-query";
+import { queryOptions, replaceEqualDeep } from "@tanstack/react-query";
 
 import { workspacePageQueryKey, workspacesQueryKey } from "#/features/workspaces/cache";
 import { getWorkspacePageFn, listWorkspacesFn } from "#/features/workspaces/server/functions";
 
+type WorkspacePageQueryResult = Awaited<ReturnType<typeof getWorkspacePageFn>>;
+
 export function workspacesQueryOptions() {
 	return queryOptions({
 		queryKey: workspacesQueryKey,
@@ -14,6 +16,15 @@ export function workspacePageQueryOptions(workspaceId: string) {
 	return queryOptions({
 		queryKey: workspacePageQueryKey(workspaceId),
 		queryFn: () => getWorkspacePageFn({ data: { workspaceId } }),
+		structuralSharing: (current, incoming) => {
+			// TanStack exposes this commit-time boundary as unknown even though the
+			// query function above owns the result type.
+			const currentPage = current as WorkspacePageQueryResult | undefined;
+			const incomingPage = incoming as WorkspacePageQueryResult;
+			return currentPage && incomingPage && currentPage.revision > incomingPage.revision
+				? currentPage
+				: replaceEqualDeep(currentPage, incomingPage);
+		},
 		staleTime: 10_000,
 	});
 }
diff --git a/src/features/workspaces/realtime/messages.ts b/src/features/workspaces/realtime/messages.ts
index 82600c559..a5d7275c0 100644
--- a/src/features/workspaces/realtime/messages.ts
+++ b/src/features/workspaces/realtime/messages.ts
@@ -1,4 +1,5 @@
 import { z } from "zod";
+import { workspaceItemSummarySchema } from "#/features/workspaces/contracts";
 
 const workspacePresenceUserSchema = z.object({
 	id: z.string(),
@@ -7,25 +8,44 @@ const workspacePresenceUserSchema = z.object({
 	image: z.string().nullable(),
 });
 
-const workspaceRealtimeServerMessageSchema = z.discriminatedUnion("type", [
+const workspacePageDeltaSchema = z.discriminatedUnion("type", [
 	z.object({
-		type: z.literal("presence.snapshot"),
+		type: z.literal("workspace.items.upserted"),
 		workspaceId: z.string(),
-		users: z.array(workspacePresenceUserSchema),
+		revision: z.number().int().nonnegative(),
+		items: z.array(workspaceItemSummarySchema).min(1),
+	}),
+	z.object({
+		type: z.literal("workspace.items.deleted"),
+		workspaceId: z.string(),
+		revision: z.number().int().nonnegative(),
+		itemIds: z.array(z.string()).min(1),
 	}),
+]);
+
+const workspacePageChangeSchema = z.union([
+	workspacePageDeltaSchema,
 	z.object({
-		type: z.literal("workspace.changed"),
+		type: z.literal("workspace.page.refresh"),
 		workspaceId: z.string(),
 		revision: z.number().int().nonnegative(),
 	}),
 ]);
 
+const workspaceRealtimeServerMessageSchema = z.union([
+	z.object({
+		type: z.literal("presence.snapshot"),
+		workspaceId: z.string(),
+		users: z.array(workspacePresenceUserSchema),
+	}),
+	workspacePageChangeSchema,
+]);
+
 export type WorkspacePresenceUser = z.infer<typeof workspacePresenceUserSchema>;
 
-export interface WorkspaceRevision {
-	workspaceId: string;
-	revision: number;
-}
+export type WorkspacePageDelta = z.infer<typeof workspacePageDeltaSchema>;
+
+export type WorkspacePageChange = z.infer<typeof workspacePageChangeSchema>;
 
 export interface WorkspaceCommandResult<T> {
 	result: T;
diff --git a/src/features/workspaces/realtime/use-workspace-presence.ts b/src/features/workspaces/realtime/use-workspace-presence.ts
index 118a0603e..2fc4bfd0f 100644
--- a/src/features/workspaces/realtime/use-workspace-presence.ts
+++ b/src/features/workspaces/realtime/use-workspace-presence.ts
@@ -6,7 +6,11 @@ import {
 	workspaceKernelAgentName,
 	workspaceKernelBasePath,
 } from "#/features/workspaces/agent-routes";
-import { parseWorkspaceRealtimeServerMessage, type WorkspacePresenceUser } from "./messages";
+import {
+	parseWorkspaceRealtimeServerMessage,
+	type WorkspacePageDelta,
+	type WorkspacePresenceUser,
+} from "./messages";
 
 type ConnectionStatus = "connecting" | "connected" | "disconnected";
 
@@ -18,8 +22,8 @@ interface PresenceState {
 
 interface UseWorkspaceRealtimeInput {
 	workspaceId: string;
-	lastSeenRevision?: number;
-	onWorkspaceChanged?: () => void;
+	onPageChange?: (change: WorkspacePageDelta) => void;
+	onDesync?: () => void;
 }
 
 function parseServerMessage(data: unknown) {
@@ -44,42 +48,28 @@ function getInitialPresenceState(workspaceId: string): PresenceState {
 
 export function useWorkspaceRealtime({
 	workspaceId,
-	lastSeenRevision,
-	onWorkspaceChanged,
+	onPageChange,
+	onDesync,
 }: UseWorkspaceRealtimeInput) {
 	const [presence, setPresence] = useState(() => getInitialPresenceState(workspaceId));
-	const cachedRevisionRef = useRef(lastSeenRevision ?? 0);
-	const revisionWorkspaceRef = useRef(workspaceId);
-	const onWorkspaceChangedRef = useRef(onWorkspaceChanged);
+	const onPageChangeRef = useRef(onPageChange);
+	const onDesyncRef = useRef(onDesync);
 
 	useEffect(() => {
-		onWorkspaceChangedRef.current = onWorkspaceChanged;
+		onPageChangeRef.current = onPageChange;
+		onDesyncRef.current = onDesync;
 	});
 
 	const currentPresence =
 		presence.workspaceId === workspaceId ? presence : getInitialPresenceState(workspaceId);
 
-	useEffect(() => {
-		if (revisionWorkspaceRef.current !== workspaceId) {
-			revisionWorkspaceRef.current = workspaceId;
-			cachedRevisionRef.current = lastSeenRevision ?? 0;
-			return;
-		}
-
-		if (lastSeenRevision === undefined) {
-			return;
-		}
-
-		cachedRevisionRef.current = lastSeenRevision;
-	}, [lastSeenRevision, workspaceId]);
-
 	const handleOpen = useCallback(() => {
 		setPresence((current) => ({
 			...current,
 			status: "connected",
 			workspaceId,
 		}));
-		onWorkspaceChangedRef.current?.();
+		onDesyncRef.current?.();
 	}, [workspaceId]);
 
 	const handleClose = useCallback(() => {
@@ -88,7 +78,6 @@ export function useWorkspaceRealtime({
 			users: [],
 			workspaceId,
 		});
-		onWorkspaceChangedRef.current?.();
 	}, [workspaceId]);
 
 	const handleError = useCallback(() => {
@@ -106,7 +95,7 @@ export function useWorkspaceRealtime({
 				return;
 			}
 
-			if (message?.type === "presence.snapshot" && message.workspaceId === workspaceId) {
+			if (message.type === "presence.snapshot" && message.workspaceId === workspaceId) {
 				setPresence((current) => ({
 					...current,
 					users: message.users,
@@ -114,12 +103,12 @@ export function useWorkspaceRealtime({
 				}));
 			}
 
-			if (
-				message?.type === "workspace.changed" &&
-				message.workspaceId === workspaceId &&
-				message.revision > cachedRevisionRef.current
-			) {
-				onWorkspaceChangedRef.current?.();
+			if (message.type !== "presence.snapshot" && message.workspaceId === workspaceId) {
+				if (message.type === "workspace.page.refresh") {
+					onDesyncRef.current?.();
+				} else {
+					onPageChangeRef.current?.(message);
+				}
 			}
 		},
 		[workspaceId],
diff --git a/src/features/workspaces/realtime/workspace-room-notifier.ts b/src/features/workspaces/realtime/workspace-room-notifier.ts
index a8845b8c1..ab88b7631 100644
--- a/src/features/workspaces/realtime/workspace-room-notifier.ts
+++ b/src/features/workspaces/realtime/workspace-room-notifier.ts
@@ -1,18 +1,18 @@
 import { getAgentByName } from "agents";
 
 import { workspaceKernelAgentName } from "#/features/workspaces/agent-routes";
-import type { WorkspaceRevision } from "#/features/workspaces/realtime/messages";
+import type { WorkspacePageChange } from "#/features/workspaces/realtime/messages";
 import { recordOperationalFailure } from "#/integrations/observability/operational-events";
 
 const workspaceCleanupDeliveryAttempts = 3;
 
 export async function notifyWorkspaceRoom(
 	env: Cloudflare.Env,
-	change: WorkspaceRevision,
+	change: WorkspacePageChange,
 ): Promise<void> {
 	try {
 		const room = await getWorkspaceRoom(env, change.workspaceId);
-		await room.publishWorkspaceChange(change);
+		await room.publishWorkspacePageChange(change);
 	} catch (error) {
 		recordOperationalFailure({
 			error,
diff --git a/src/features/workspaces/server/mutations.test.ts b/src/features/workspaces/server/mutations.test.ts
index 46c0cd59c..7142d8b7a 100644
--- a/src/features/workspaces/server/mutations.test.ts
+++ b/src/features/workspaces/server/mutations.test.ts
@@ -88,6 +88,7 @@ describe("workspace settings mutations", () => {
 		);
 		expect(mocks.nextWorkspaceRevision).toHaveBeenCalledWith(transaction, workspace.id);
 		expect(mocks.notifyWorkspaceRoom).toHaveBeenCalledWith(mocks.env, {
+			type: "workspace.page.refresh",
 			workspaceId: workspace.id,
 			revision: 8,
 		});
diff --git a/src/features/workspaces/server/mutations.ts b/src/features/workspaces/server/mutations.ts
index 2097e1a5e..c79ac51c7 100644
--- a/src/features/workspaces/server/mutations.ts
+++ b/src/features/workspaces/server/mutations.ts
@@ -187,7 +187,11 @@ export async function updateWorkspaceForCurrentUser(
 			revision: await nextWorkspaceRevision(transaction, input.workspaceId),
 		};
 	});
-	await notifyWorkspaceRoom(env, { workspaceId: input.workspaceId, revision: update.revision });
+	await notifyWorkspaceRoom(env, {
+		type: "workspace.page.refresh",
+		workspaceId: input.workspaceId,
+		revision: update.revision,
+	});
 
 	const workspace = {
 		...update.updatedWorkspace,
diff --git a/src/features/workspaces/server/queries.ts b/src/features/workspaces/server/queries.ts
index a3bd2edb3..724e3cad6 100644
--- a/src/features/workspaces/server/queries.ts
+++ b/src/features/workspaces/server/queries.ts
@@ -65,7 +65,6 @@ export async function getWorkspacePageForUser(
 				return {
 					workspace,
 					items: page.items,
-					itemFacts: page.itemFacts,
 					revision: page.revision,
 				};
 			},
diff --git a/src/features/workspaces/use-create-workspace.ts b/src/features/workspaces/use-create-workspace.ts
index 31e73f6c5..505ce2355 100644
--- a/src/features/workspaces/use-create-workspace.ts
+++ b/src/features/workspaces/use-create-workspace.ts
@@ -60,7 +60,6 @@ export function useCreateWorkspaceMutation() {
 			setWorkspacePageCache(queryClient, {
 				workspace: optimisticWorkspace,
 				items: [],
-				itemFacts: [],
 				revision: 0,
 			});
 			markWorkspaceCreatedThisSession(id);
diff --git a/src/features/workspaces/use-workspace-kernel-items.ts b/src/features/workspaces/use-workspace-kernel-items.ts
index 6bfc2d2a9..bb74b71bb 100644
--- a/src/features/workspaces/use-workspace-kernel-items.ts
+++ b/src/features/workspaces/use-workspace-kernel-items.ts
@@ -1,14 +1,12 @@
 import { type QueryClient, useMutation, useQueryClient } from "@tanstack/react-query";
 import { useServerFn } from "@tanstack/react-start";
-import { useMemo } from "react";
 import { toast } from "sonner";
 
 import {
+	applyWorkspacePageDeltaToCache,
 	createWorkspaceItemInPageCache,
-	getWorkspaceItemColorInPageCache,
 	moveWorkspaceItemsInPageCache,
 	removeWorkspaceItemsFromPageCache,
-	updateWorkspaceItemColorInPageCache,
 	workspacePageQueryKey,
 } from "#/features/workspaces/cache";
 import type {
@@ -27,9 +25,6 @@ import {
 	updateWorkspaceItemColorFn,
 } from "#/features/workspaces/server/functions";
 import { getErrorMessage } from "#/lib/error-message";
-import { createKeyedDebouncedLatest } from "#/lib/keyed-debounced-latest";
-
-const workspaceItemColorCommitDelayMs = 180;
 export function useCreateWorkspaceItemMutation() {
 	const createWorkspaceItem = useServerFn(createWorkspaceItemFn);
 	const queryClient = useQueryClient();
@@ -49,7 +44,14 @@ export function useCreateWorkspaceItemMutation() {
 				});
 			}
 		},
-		onSuccess: (_command, input) => refreshWorkspacePage(queryClient, input.workspaceId),
+		onSuccess: (command, input) => {
+			applyWorkspacePageDeltaToCache(queryClient, {
+				type: "workspace.items.upserted",
+				workspaceId: input.workspaceId,
+				items: [command.result],
+				revision: command.revision,
+			});
+		},
 		onError: (error, preparedInput) => {
 			if (preparedInput.id) {
 				removeWorkspaceItemsFromPageCache(queryClient, preparedInput.workspaceId, [
@@ -80,7 +82,14 @@ export function useRenameWorkspaceItemMutation() {
 
 	return useMutation({
 		mutationFn: (input: RenameWorkspaceItemInput) => renameWorkspaceItem({ data: input }),
-		onSuccess: (_command, input) => refreshWorkspacePage(queryClient, input.workspaceId),
+		onSuccess: (command, input) => {
+			applyWorkspacePageDeltaToCache(queryClient, {
+				type: "workspace.items.upserted",
+				workspaceId: input.workspaceId,
+				items: [command.result],
+				revision: command.revision,
+			});
+		},
 		onError: (error) => {
 			toast.error(getErrorMessage(error, "Unable to rename workspace item right now."));
 		},
@@ -100,7 +109,14 @@ export function useMoveWorkspaceItemsMutation() {
 
 			moveWorkspaceItemsInPageCache(queryClient, input);
 		},
-		onSuccess: (_command, input) => refreshWorkspacePage(queryClient, input.workspaceId),
+		onSuccess: (command, input) => {
+			applyWorkspacePageDeltaToCache(queryClient, {
+				type: "workspace.items.upserted",
+				workspaceId: input.workspaceId,
+				items: command.result,
+				revision: command.revision,
+			});
+		},
 		onError: (_error, input) => refreshWorkspacePage(queryClient, input.workspaceId),
 	});
 }
@@ -109,36 +125,20 @@ export function useUpdateWorkspaceItemColorMutation() {
 	const updateWorkspaceItemColor = useServerFn(updateWorkspaceItemColorFn);
 	const queryClient = useQueryClient();
 
-	const commitColor = useMemo(
-		() =>
-			createKeyedDebouncedLatest<UpdateWorkspaceItemColorInput>({
-				getKey: getWorkspaceItemColorCommitKey,
-				wait: workspaceItemColorCommitDelayMs,
-				onExecute: (input) => {
-					updateWorkspaceItemColor({ data: input })
-						.then(() => refreshWorkspacePage(queryClient, input.workspaceId))
-						.catch((error: unknown) => {
-							if (getWorkspaceItemColorInPageCache(queryClient, input) !== input.color) {
-								return;
-							}
-
-							void refreshWorkspacePage(queryClient, input.workspaceId);
-							toast.error(getErrorMessage(error, "Unable to update item color right now."));
-						});
-				},
-			}),
-		[queryClient, updateWorkspaceItemColor],
-	);
-
-	const mutate = (input: UpdateWorkspaceItemColorInput) => {
-		void queryClient.cancelQueries({
-			queryKey: workspacePageQueryKey(input.workspaceId),
-		});
-		updateWorkspaceItemColorInPageCache(queryClient, input);
-		commitColor(input);
-	};
-
-	return { mutate };
+	return useMutation({
+		mutationFn: (input: UpdateWorkspaceItemColorInput) => updateWorkspaceItemColor({ data: input }),
+		onSuccess: (command, input) => {
+			applyWorkspacePageDeltaToCache(queryClient, {
+				type: "workspace.items.upserted",
+				workspaceId: input.workspaceId,
+				items: [command.result],
+				revision: command.revision,
+			});
+		},
+		onError: (error) => {
+			toast.error(getErrorMessage(error, "Unable to update item color right now."));
+		},
+	});
 }
 
 export function useDeleteWorkspaceItemsMutation() {
@@ -174,7 +174,16 @@ export function useDeleteWorkspaceItemsMutation() {
 
 			removeWorkspaceItemsFromPageCache(queryClient, input.workspaceId, input.itemIds);
 		},
-		onSuccess: (_command, input) => refreshWorkspacePage(queryClient, input.workspaceId),
+		onSuccess: (command, input) => {
+			if (command.result.deletedItemIds.length > 0) {
+				applyWorkspacePageDeltaToCache(queryClient, {
+					type: "workspace.items.deleted",
+					workspaceId: input.workspaceId,
+					itemIds: command.result.deletedItemIds,
+					revision: command.revision,
+				});
+			}
+		},
 		onError: (_error, input) => refreshWorkspacePage(queryClient, input.workspaceId),
 	});
 }
@@ -187,10 +196,6 @@ function getDeleteWorkspaceItemsToastMessage(
 	return `${action} ${itemCount === 1 ? "item" : `${itemCount} items`}${suffix}`;
 }
 
-function getWorkspaceItemColorCommitKey(input: UpdateWorkspaceItemColorInput) {
-	return `${input.workspaceId}:${input.itemId}`;
-}
-
 function refreshWorkspacePage(queryClient: QueryClient, workspaceId: string) {
 	return queryClient.invalidateQueries({ queryKey: workspacePageQueryKey(workspaceId) });
 }
diff --git a/src/integrations/posthog/ai-observability.ts b/src/integrations/posthog/ai-observability.ts
index 5688bb830..1d37cd0f4 100644
--- a/src/integrations/posthog/ai-observability.ts
+++ b/src/integrations/posthog/ai-observability.ts
@@ -69,21 +69,32 @@ function appendAiTraceProperties(
  * route that 400'd on every Google leg and was served by OpenAI looked like
  * Gemini for 105 generations. `credential_type` distinguishes our BYOK keys from
  * Vercel's metered credits.
+ *
+ * `serviceTier` is the tier the provider actually served, not the `priority` we
+ * asked for: the gateway omits it entirely on a silent downgrade to standard.
+ * That absence is the signal worth having — priority bills ~1.8-2x when granted,
+ * so it tells us whether we bought latency or just asked for it.
  */
 export function getGatewayServedRoute(providerMetadata: unknown) {
-	const routing = (providerMetadata as { gateway?: { routing?: unknown } } | undefined)?.gateway
-		?.routing as
+	const gateway = (providerMetadata as { gateway?: unknown } | undefined)?.gateway as
 		| {
-				finalProvider?: string;
-				modelAttempts?: { providerAttempts?: { credentialType?: string; success?: boolean }[] }[];
+				serviceTier?: string;
+				routing?: {
+					finalProvider?: string;
+					modelAttempts?: {
+						providerAttempts?: { credentialType?: string; success?: boolean }[];
+					}[];
+				};
 		  }
 		| undefined;
+	const routing = gateway?.routing;
 
 	return {
 		provider: routing?.finalProvider,
 		credentialType: routing?.modelAttempts
 			?.flatMap((attempt) => attempt.providerAttempts ?? [])
 			.find((attempt) => attempt.success)?.credentialType,
+		serviceTier: gateway?.serviceTier,
 	};
 }
 
@@ -113,6 +124,7 @@ export function capturePostHogAiGeneration(
 	const properties: Record<string, unknown> = {
 		...captureOptions.properties,
 		...(served.credentialType ? { credential_type: served.credentialType } : {}),
+		...(served.serviceTier ? { service_tier: served.serviceTier } : {}),
 	};
 
 	appendAiTraceProperties(properties, {
diff --git a/src/integrations/posthog/ai-observability.worker.test.ts b/src/integrations/posthog/ai-observability.worker.test.ts
index 912740a16..46152ebda 100644
--- a/src/integrations/posthog/ai-observability.worker.test.ts
+++ b/src/integrations/posthog/ai-observability.worker.test.ts
@@ -38,6 +38,17 @@ describe("getGatewayServedRoute", () => {
 		).toBe("system");
 	});
 
+	// A granted priority tier bills ~2x, and the gateway reports a downgrade by
+	// omitting the field rather than saying "default".
+	it("reports the tier that was served, and nothing when priority was downgraded", () => {
+		const served = routing([{ provider: "openai", credentialType: "byok", success: true }]);
+
+		expect(
+			getGatewayServedRoute({ gateway: { ...served.gateway, serviceTier: "priority" } }),
+		).toEqual({ provider: "openai", credentialType: "byok", serviceTier: "priority" });
+		expect(getGatewayServedRoute(served).serviceTier).toBeUndefined();
+	});
+
 	it("returns nothing for a non-gateway result, so callers keep their own value", () => {
 		expect(getGatewayServedRoute(undefined)).toEqual({
 			provider: undefined,
diff --git a/src/lib/keyed-debounced-latest.ts b/src/lib/keyed-debounced-latest.ts
deleted file mode 100644
index be02668e8..000000000
--- a/src/lib/keyed-debounced-latest.ts
+++ /dev/null
@@ -1,31 +0,0 @@
-import { debounce } from "@tanstack/pacer";
-
-export function createKeyedDebouncedLatest<TInput>({
-	getKey,
-	onExecute,
-	wait,
-}: {
-	getKey: (input: TInput) => string;
-	onExecute: (input: TInput) => void;
-	wait: number;
-}) {
-	const debouncedByKey = new Map<string, (input: TInput) => void>();
-
-	return (input: TInput) => {
-		const key = getKey(input);
-		let debounced = debouncedByKey.get(key);
-
-		if (!debounced) {
-			debounced = debounce(
-				(latestInput: TInput) => {
-					debouncedByKey.delete(key);
-					onExecute(latestInput);
-				},
-				{ wait },
-			);
-			debouncedByKey.set(key, debounced);
-		}
-
-		debounced(input);
-	};
-}