perf(i18n): stop serializing the full catalogue on public pages

The root layout fed the entire ~254 KB message catalogue to
NextIntlClientProvider, which serializes it into the RSC payload of every
page. A public page only reads ~59 KB of it; the ~195 KB difference is staff
tool copy that only /admin, /admin-next and /mod ever render.

The root provider now installs the reduced catalogue and each staff route
group re-installs the full one, since a nested NextIntlClientProvider replaces
the parent message set rather than merging into it. pages.admin.actions stays
public because the shared useServerAction hook runs on public pages too.

Measured: 253 KB -> 59 KB of messages per public page (raw JSON).

Guard tests cover all three halves: the root keeps using the reduced
catalogue, every staff layout installs its own full provider, and no public
tree reads a staff-only namespace.

src/app/admin-next/layout.tsx

@@ -1,4 +1,6 @@
 import { notFound } from "next/navigation";
+import { NextIntlClientProvider } from "next-intl";
+import { getLocale, getMessages } from "next-intl/server";
 import type { ReactNode } from "react";
 import { env } from "@/env";
 import { isHousekeepingPreviewEnabled } from "@/features/housekeeping/foundation/preview-gate";
@@ -27,5 +29,13 @@ export default async function AdminNextLayout({
 		notFound();
 	}
 
-	return children;
+	// Staff tree: re-install the full catalogue the root layout scopes down to
+	// the public subset (nested providers replace the parent set).
+	const [locale, messages] = await Promise.all([getLocale(), getMessages()]);
+
+	return (
+		<NextIntlClientProvider locale={locale} messages={messages}>
+			{children}
+		</NextIntlClientProvider>
+	);
 }

src/app/admin/layout.tsx

@@ -1,7 +1,8 @@
 import { eq } from "drizzle-orm";
 import { LogOut } from "lucide-react";
 import { redirect } from "next/navigation";
-import { getTranslations } from "next-intl/server";
+import { NextIntlClientProvider } from "next-intl";
+import { getLocale, getMessages, getTranslations } from "next-intl/server";
 import type { ReactNode } from "react";
 import { AdminHubChrome } from "@/components/admin/admin-hub-chrome";
 import { AdminMobileWrapper } from "@/components/admin/admin-mobile-wrapper";
@@ -40,8 +41,13 @@ export default async function AdminLayout({
 		if (!u?.twoFactorConfirmedAt) redirect("/settings/2fa?error=staffrequired");
 	}
 
+	// The root layout ships the reduced catalogue so public pages do not carry
+	// the ~195 KB of staff-tool strings. Nested providers replace the parent
+	// set rather than merging, so staff route groups re-install the full one.
+	const [locale, messages] = await Promise.all([getLocale(), getMessages()]);
+
 	return (
-		<>
+		<NextIntlClientProvider locale={locale} messages={messages}>
 			{csrfToken ? <meta name="csrf-token" content={csrfToken} /> : null}
 			<AdminMobileWrapper sidebar={<Sidebar staff={staff} />}>
 				<div
@@ -56,7 +62,7 @@ export default async function AdminLayout({
 				</div>
 			</AdminMobileWrapper>
 			<AdminToaster />
-		</>
+		</NextIntlClientProvider>
 	);
 }
 

src/app/layout.tsx

@@ -13,6 +13,7 @@ import { ThemeVars } from "@/components/theme-vars";
 import { enforceSiteAccess } from "@/lib/access-guard";
 import { getDefaultFaviconDataUri } from "@/lib/default-favicon";
 import { resolveHotelName } from "@/lib/hotel-name";
+import { publicClientMessages } from "@/lib/i18n-client-messages";
 import { siteSettings } from "@/lib/services/site-settings";
 import "./globals.css";
 
@@ -68,7 +69,11 @@ export default async function RootLayout({
 }) {
 	await enforceSiteAccess();
 	const locale = await getLocale();
-	const messages = await getMessages();
+	// Only the namespaces non-staff routes can reach: the full catalogue is
+	// ~254 KB and would otherwise be serialised into every public page's RSC
+	// payload. `/admin`, `/admin-next` and `/mod` install a nested provider
+	// seeded with the full set (see i18n-client-messages).
+	const messages = publicClientMessages(await getMessages());
 	const defaultDark = await siteSettings.getBool("default_dark", false);
 	const nitroUrl = await siteSettings.get("nitro_client_url", "");
 	const nonce = (await headers()).get("x-nonce") ?? undefined;

src/app/mod/layout.tsx

@@ -10,7 +10,8 @@ import {
 	Users,
 } from "lucide-react";
 import { redirect } from "next/navigation";
-import { getTranslations } from "next-intl/server";
+import { NextIntlClientProvider } from "next-intl";
+import { getLocale, getMessages, getTranslations } from "next-intl/server";
 import type { ReactNode } from "react";
 import { LanguageSwitcher } from "@/components/language-switcher";
 import Link from "@/components/link";
@@ -81,8 +82,13 @@ export default async function ModLayout({ children }: { children: ReactNode }) {
 		{ href: "/mod/team", label: t("nav.team"), icon: Users, show: showTeam },
 	].filter((item) => item.show);
 
+	// The root layout ships the reduced catalogue so public pages do not carry
+	// the ~195 KB of staff-tool strings. Nested providers replace the parent
+	// set rather than merging, so staff route groups re-install the full one.
+	const [locale, messages] = await Promise.all([getLocale(), getMessages()]);
+
 	return (
-		<>
+		<NextIntlClientProvider locale={locale} messages={messages}>
 			{csrfToken ? <meta name="csrf-token" content={csrfToken} /> : null}
 			<div
 				data-admin
@@ -140,6 +146,6 @@ export default async function ModLayout({ children }: { children: ReactNode }) {
 				</header>
 				<main className="mx-auto max-w-6xl p-4 sm:p-6">{children}</main>
 			</div>
-		</>
+		</NextIntlClientProvider>
 	);
 }

src/features/housekeeping/foundation/preview-route-contract.test.ts

@@ -41,6 +41,8 @@ const routeMocks = vi.hoisted(() => {
 			}
 			return translate;
 		}),
+		getLocale: vi.fn(async () => "en"),
+		getMessages: vi.fn(async () => ({})),
 		notFound: vi.fn((): never => {
 			throw new Error("NEXT_NOT_FOUND");
 		}),
@@ -58,6 +60,8 @@ vi.mock("next/navigation", () => ({
 }));
 vi.mock("next-intl/server", () => ({
 	getTranslations: routeMocks.getTranslations,
+	getLocale: routeMocks.getLocale,
+	getMessages: routeMocks.getMessages,
 }));
 vi.mock("@/features/housekeeping/foundation/server-capability-context", () => ({
 	getHousekeepingCapabilityContext: routeMocks.getHousekeepingCapabilityContext,

src/lib/i18n-client-messages.test.ts

@@ -85,7 +85,12 @@ describe("publicClientMessages", () => {
 			if (key === "admin") continue;
 			expect(result[key]).toBeDefined();
 		}
-		expect(result.pages.admin).toBeUndefined();
+		// `pages.admin` survives only in the shape the shared server-action hook
+		// needs: the generic `actions` copy, nothing staff-specific.
+		expect(Object.keys(result.pages.admin)).toEqual(["actions"]);
+		expect(result.pages.admin.actions.saved).toBe(en.pages.admin.actions.saved);
+		expect(result.pages.admin.nav).toBeUndefined();
+		expect(result.pages.admin.catalog).toBeUndefined();
 	});
 
 	it("actually shrinks the catalogue", async () => {
@@ -111,3 +116,59 @@ describe("publicClientMessages", () => {
 		expect(en.pages.admin).toBeDefined();
 	});
 });
+
+/**
+ * Scoping only works if the reduced catalogue goes to the client *and* every
+ * staff route group re-installs the full one. These two halves drift silently:
+ * narrowing the root without adding a staff provider renders raw keys in the
+ * admin panel, and the reverse just costs bytes. Both are asserted here.
+ */
+describe("client catalogue scoping is wired up", () => {
+	const STAFF_LAYOUTS = [
+		"src/app/admin/layout.tsx",
+		"src/app/admin-next/layout.tsx",
+		"src/app/mod/layout.tsx",
+	];
+
+	it("the root layout feeds the reduced catalogue to its provider", () => {
+		const src = readFileSync(join(process.cwd(), "src/app/layout.tsx"), "utf8");
+		expect(src).toContain("publicClientMessages(await getMessages())");
+	});
+
+	for (const layout of STAFF_LAYOUTS) {
+		it(`${layout} re-installs the full catalogue`, () => {
+			const src = readFileSync(join(process.cwd(), layout), "utf8");
+			expect(src).toContain("NextIntlClientProvider");
+			expect(src).toContain("getMessages()");
+		});
+	}
+});
+
+/**
+ * A client component that reads `admin.*` / `pages.admin.*` outside a staff
+ * route group would fall back to raw keys once the root catalogue is scoped,
+ * because the provider it inherits no longer carries them. Staff trees are the
+ * ones that install the full catalogue; the allowlist holds shared code that
+ * deliberately runs on public pages too.
+ */
+describe("staff namespace consumers sit in a staff tree", () => {
+	const STAFF_TREE =
+		/^src[\\/](app[\\/](admin|admin-next|mod)[\\/]|components[\\/]admin[\\/]|features[\\/](catalog|operations|history|housekeeping)[\\/])/;
+	const ALLOWLIST = new Set(["src/hooks/use-server-action.ts"]);
+	const CLIENT_STAFF_NS = /useTranslations\((["`])((admin)|(pages\.admin))/;
+
+	it("there is source to scan", () => {
+		expect(sourceFiles(join(process.cwd(), "src")).length).toBeGreaterThan(500);
+	});
+
+	it("no stray consumer of a staff namespace", () => {
+		const offenders: string[] = [];
+		for (const file of sourceFiles(join(process.cwd(), "src"))) {
+			const rel = file.slice(process.cwd().length + 1).replaceAll("\\", "/");
+			if (rel.includes(".test.")) continue;
+			if (STAFF_TREE.test(rel) || ALLOWLIST.has(rel)) continue;
+			if (CLIENT_STAFF_NS.test(readFileSync(file, "utf8"))) offenders.push(rel);
+		}
+		expect(offenders).toEqual([]);
+	});
+});

src/lib/i18n-client-messages.ts

@@ -3,22 +3,35 @@ import type { AbstractIntlMessages } from "next-intl";
 /**
  * Client-side message scoping.
  *
- * `getMessages()` hands back the whole catalogue, and the root layout feeds all
- * of it to `NextIntlClientProvider`, which serialises every message into the RSC
- * payload of every page. The catalogue is ~235 KB of which `pages.admin` and
- * `admin` together are ~177 KB — and no public page ever reads either.
+ * `getMessages()` hands back the whole catalogue, and the root layout feeds it
+ * to `NextIntlClientProvider`, which serialises every message into the RSC
+ * payload of every page. The catalogue is ~254 KB of which `pages.admin` and
+ * `admin` together are ~195 KB — and no public page ever reads either.
  *
  * Nested `NextIntlClientProvider`s REPLACE the parent's messages rather than
  * merging them (see use-intl's IntlProvider: `messages ?? parent.messages`), so
- * a segment cannot ask for "just my part". Instead the public layout installs a
- * provider seeded with the public subset, which shrinks the payload for every
- * public page while leaving /admin, /mod, /client and /admin-next on the full set.
+ * a segment cannot ask for "just my part". The root layout therefore installs
+ * the reduced catalogue, and the staff route groups (`/admin`, `/admin-next`,
+ * `/mod`) each install a nested provider seeded with the full one, which keeps
+ * staff tools complete while public pages ship ~59 KB instead of ~254 KB.
  */
 
 /** Top-level namespaces plus `pages.*` sub-namespaces reserved for staff tools. */
 const ADMIN_ONLY_NAMESPACES = new Set(["admin"]);
 const ADMIN_ONLY_PAGE_NAMESPACES = new Set(["admin"]);
 
+/**
+ * `pages.admin` sub-namespaces that are NOT staff-only because a shared
+ * client component reads them on public pages too.
+ *
+ * `useServerAction` (src/hooks/use-server-action.ts) resolves its default
+ * success/error toast copy from `pages.admin.actions` and is used by
+ * `/events/[slugOrId]` and `/polls/[id]`, so that one sub-namespace has to
+ * survive the filter — the strings in it are generic ("Saved successfully."),
+ * not staff-tool copy.
+ */
+const PUBLIC_PAGE_NAMESPACES = new Set(["actions"]);
+
 /**
  * Drop the staff-tool namespaces from a full catalogue.
  *
@@ -43,8 +56,21 @@ export function publicClientMessages(
 		for (const [pageKey, pageValue] of Object.entries(
 			value as AbstractIntlMessages,
 		)) {
-			if (ADMIN_ONLY_PAGE_NAMESPACES.has(pageKey)) continue;
+			if (!ADMIN_ONLY_PAGE_NAMESPACES.has(pageKey)) {
 				pages[pageKey] = pageValue;
+				continue;
+			}
+			// Staff-only page namespace: keep only the sub-namespaces that a
+			// shared client component reads on public pages as well.
+			const shared: AbstractIntlMessages = {};
+			for (const [sharedKey, sharedValue] of Object.entries(
+				pageValue as AbstractIntlMessages,
+			)) {
+				if (PUBLIC_PAGE_NAMESPACES.has(sharedKey)) {
+					shared[sharedKey] = sharedValue;
+				}
+			}
+			if (Object.keys(shared).length > 0) pages[pageKey] = shared;
 		}
 		result.pages = pages;
 	}