fix(docs): set metadataBase and emit one absolute canonical per page type

apps/docs/app/[lang]/blog/[[...slug]]/page.tsx

@@ -3,6 +3,7 @@ import { blog } from '@/lib/source';
 import { getMDXComponents } from '@/mdx-components';
 import { HomeLayout } from 'fumadocs-ui/layouts/home';
 import { baseOptions } from '@/lib/layout.shared';
+import { absoluteUrl } from '@/lib/site';
 import Link from 'next/link';
 import { ArrowLeft } from 'lucide-react';
 
@@ -192,6 +193,9 @@ export async function generateMetadata({
  return {
  title: 'Blog',
  description: 'Insights, updates, and best practices from the ObjectStack team.',
+ // The index has no MDX file behind it, so its route is spelled out here — the
+ // same literal `app/sitemap.ts` lists it under.
+ alternates: { canonical: absoluteUrl('/blog') },
  };
  }
 
@@ -204,5 +208,6 @@ export async function generateMetadata({
  return {
  title: page.data.title,
  description: page.data.description,
+ alternates: { canonical: absoluteUrl(page.url) },
  };
 }

apps/docs/app/[lang]/docs/[[...slug]]/page.tsx

@@ -9,6 +9,7 @@ import { File, Folder, Files } from 'fumadocs-ui/components/files';
 import { Tab, Tabs } from 'fumadocs-ui/components/tabs';
 import { LLMCopyButton, ViewOptions } from '@/components/ai/page-actions';
 import { gitConfig } from '@/lib/layout.shared';
+import { absoluteUrl } from '@/lib/site';
 
 export default async function Page(props: {
  params: Promise<{ lang: string; slug?: string[] }>;
@@ -63,5 +64,12 @@ export async function generateMetadata(props: {
  return {
  title: page.data.title,
  description: page.data.description,
+ /**
+ * `page.url` is the same locale-stripped route fumadocs uses for in-site links
+ * and that `app/sitemap.ts` lists, so the canonical link and the sitemap entry
+ * cannot drift apart. `absoluteUrl()` throws rather than emit a URL on another
+ * host if that ever stops being a site-relative path.
+ */
+ alternates: { canonical: absoluteUrl(page.url) },
  };
 }

apps/docs/app/[lang]/page.tsx

@@ -4,6 +4,7 @@ import { ArrowRight, Check } from 'lucide-react';
 import { Bricolage_Grotesque, IBM_Plex_Mono } from 'next/font/google';
 import { HomeLayout } from 'fumadocs-ui/layouts/home';
 import { baseOptions, gitConfig } from '@/lib/layout.shared';
+import { absoluteUrl } from '@/lib/site';
 import { YouTubeEmbed } from '@/components/youtube-embed';
 
 /** The 90-second overview — the same video the README's hero cover links to. */
@@ -25,6 +26,13 @@ export const metadata: Metadata = {
  title: 'Metadata framework for AI-written apps',
  description:
  'ObjectStack turns the whole app — data model, UI, workflows, permissions — into typed metadata: a complete CRM in under 150k tokens, one context window.',
+ /**
+ * `/` is the one indexable spelling of the homepage: `proxy.ts` rewrites `/` to
+ * this route internally, and the prefixed form `/en` 307s back to `/`. Every
+ * other spelling a crawler reaches it by — query strings, tracking parameters —
+ * points here.
+ */
+ alternates: { canonical: absoluteUrl('/') },
 };
 
 const VOCABULARY: { tag: string; title: string; copy: string }[] = [

apps/docs/app/layout.tsx

@@ -1,8 +1,19 @@
 import './global.css';
 import type { ReactNode } from 'react';
 import type { Metadata } from 'next';
+import { SITE_ORIGIN } from '@/lib/site';
 
 export const metadata: Metadata = {
+ /**
+ * The origin every relative URL in this site's metadata resolves against —
+ * canonical links today, the Open Graph / Twitter image paths next. Left unset,
+ * Next resolves them against a build-time guess of the deployment's own origin,
+ * so a preview build would advertise itself as the real site.
+ *
+ * `new URL(...)` at the point of use, so `lib/site.ts` keeps exporting an
+ * immutable string rather than a `URL` instance shared across every route.
+ */
+ metadataBase: new URL(SITE_ORIGIN),
  title: {
  template: '%s | ObjectStack',
  default: 'ObjectStack',