diff --git a/docs/superpowers/plans/2026-08-02-ombrora-hub-landing.md b/docs/superpowers/plans/2026-08-02-ombrora-hub-landing.md
index 617cf66..68f95fc 100644
--- a/docs/superpowers/plans/2026-08-02-ombrora-hub-landing.md
+++ b/docs/superpowers/plans/2026-08-02-ombrora-hub-landing.md
@@ -457,14 +457,16 @@ describe('BaseLayout SEO tags and theming', () => {
     expect(en).toContain('prefers-color-scheme: light');
   });
 
-  it('links the global stylesheet', () => {
+  it('applies the global stylesheet (inlined or linked)', () => {
     const en = readFileSync('dist/en/index.html', 'utf-8');
-    expect(en).toMatch(/<link rel="stylesheet"[^>]*href="[^"]+\.css"/);
+    const hasInlineStyle = /<style>[\s\S]*--accent[\s\S]*<\/style>/.test(en);
+    const hasStylesheetLink = /<link rel="stylesheet"[^>]*href="[^"]+\.css"/.test(en);
+    expect(hasInlineStyle || hasStylesheetLink).toBe(true);
   });
 });
 ```
 
-Note: from this task on, tests call `npm run build` themselves via `beforeAll`, so `npm run test` alone is sufficient going forward.
+Note: from this task on, tests call `npm run build` themselves via `beforeAll`, so `npm run test` alone is sufficient going forward. Astro inlines small stylesheets into a `<style>` tag during build rather than emitting an external `<link>` — the test accepts either form.
 
 - [ ] **Step 2: Run the test and confirm it fails**
 
diff --git a/src/layouts/BaseLayout.astro b/src/layouts/BaseLayout.astro
new file mode 100644
index 0000000..9c20ad9
--- /dev/null
+++ b/src/layouts/BaseLayout.astro
@@ -0,0 +1,46 @@
+---
+import '../styles/global.css';
+import { getDictionary } from '../i18n';
+import { otherLocale, swapLocalePath } from '../i18n/locale';
+import type { Locale } from '../i18n/locale';
+
+interface Props {
+  locale: Locale;
+}
+
+const { locale } = Astro.props;
+const t = getDictionary(locale);
+const target = otherLocale(locale);
+const alternatePath = swapLocalePath(Astro.url.pathname, locale, target);
+const canonicalURL = new URL(Astro.url.pathname, Astro.site);
+const alternateURL = new URL(alternatePath, Astro.site);
+const enURL = locale === 'en' ? canonicalURL : alternateURL;
+const frURL = locale === 'fr' ? canonicalURL : alternateURL;
+---
+<!doctype html>
+<html lang={locale} data-theme="dark">
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <title>{t.meta.title}</title>
+    <meta name="description" content={t.meta.description} />
+    <link rel="canonical" href={canonicalURL} />
+    <link rel="alternate" hreflang="en" href={enURL} />
+    <link rel="alternate" hreflang="fr" href={frURL} />
+    <link rel="alternate" hreflang="x-default" href={enURL} />
+    <meta property="og:title" content={t.meta.title} />
+    <meta property="og:description" content={t.meta.description} />
+    <meta property="og:type" content="website" />
+    <meta property="og:url" content={canonicalURL} />
+    <script is:inline>
+      (function () {
+        var stored = localStorage.getItem('ombrora-theme');
+        var theme = stored || (window.matchMedia('(prefers-color-scheme: light)').matches ? 'light' : 'dark');
+        document.documentElement.setAttribute('data-theme', theme);
+      })();
+    </script>
+  </head>
+  <body>
+    <slot />
+  </body>
+</html>
diff --git a/src/pages/en/index.astro b/src/pages/en/index.astro
index b9999ed..abe3be6 100644
--- a/src/pages/en/index.astro
+++ b/src/pages/en/index.astro
@@ -1,12 +1,8 @@
 ---
+import BaseLayout from '../../layouts/BaseLayout.astro';
+
 const locale = 'en';
 ---
-<html lang={locale}>
-  <head>
-    <meta charset="utf-8" />
-    <title>Ombrora</title>
-  </head>
-  <body>
-    <h1>Ombrora — EN</h1>
-  </body>
-</html>
+<BaseLayout locale={locale}>
+  <h1>Ombrora</h1>
+</BaseLayout>
diff --git a/src/pages/fr/index.astro b/src/pages/fr/index.astro
index 9ff3eed..46fd0cb 100644
--- a/src/pages/fr/index.astro
+++ b/src/pages/fr/index.astro
@@ -1,12 +1,8 @@
 ---
+import BaseLayout from '../../layouts/BaseLayout.astro';
+
 const locale = 'fr';
 ---
-<html lang={locale}>
-  <head>
-    <meta charset="utf-8" />
-    <title>Ombrora</title>
-  </head>
-  <body>
-    <h1>Ombrora — FR</h1>
-  </body>
-</html>
+<BaseLayout locale={locale}>
+  <h1>Ombrora</h1>
+</BaseLayout>
diff --git a/src/styles/global.css b/src/styles/global.css
new file mode 100644
index 0000000..b2be26e
--- /dev/null
+++ b/src/styles/global.css
@@ -0,0 +1,137 @@
+:root {
+  --bg: #ffffff;
+  --fg: #14171a;
+  --muted: #5b6470;
+  --accent: #6d5bff;
+  --card-bg: #f4f5f7;
+  --border: #e1e4e8;
+}
+
+:root[data-theme='dark'] {
+  --bg: #0d0f12;
+  --fg: #e6e8eb;
+  --muted: #9aa3ad;
+  --accent: #8f7cff;
+  --card-bg: #16191d;
+  --border: #262b31;
+}
+
+@media (prefers-color-scheme: dark) {
+  :root:not([data-theme='light']) {
+    --bg: #0d0f12;
+    --fg: #e6e8eb;
+    --muted: #9aa3ad;
+    --accent: #8f7cff;
+    --card-bg: #16191d;
+    --border: #262b31;
+  }
+}
+
+* {
+  box-sizing: border-box;
+}
+
+body {
+  margin: 0;
+  background: var(--bg);
+  color: var(--fg);
+  font-family: system-ui, -apple-system, 'Segoe UI', sans-serif;
+  line-height: 1.5;
+}
+
+.site-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  padding: 1rem 1.5rem;
+  border-bottom: 1px solid var(--border);
+}
+
+.header-actions {
+  display: flex;
+  gap: 0.75rem;
+  align-items: center;
+}
+
+.brand {
+  font-weight: 700;
+  color: var(--fg);
+  text-decoration: none;
+}
+
+.language-switcher {
+  color: var(--muted);
+  text-decoration: none;
+  font-size: 0.9rem;
+}
+
+.theme-toggle {
+  background: transparent;
+  border: 1px solid var(--border);
+  border-radius: 999px;
+  padding: 0.25rem 0.6rem;
+  cursor: pointer;
+  color: var(--fg);
+}
+
+main {
+  max-width: 960px;
+  margin: 0 auto;
+  padding: 2rem 1.5rem 4rem;
+}
+
+.hero {
+  padding: 3rem 0;
+}
+
+.hero h1 {
+  font-size: clamp(2rem, 4vw, 2.75rem);
+  margin: 0 0 0.75rem;
+}
+
+.hero p {
+  color: var(--muted);
+  max-width: 40ch;
+}
+
+.services-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
+  gap: 1.25rem;
+}
+
+.service-card {
+  display: block;
+  padding: 1.25rem;
+  border: 1px solid var(--border);
+  border-radius: 12px;
+  background: var(--card-bg);
+  text-decoration: none;
+  color: var(--fg);
+}
+
+.service-card__tag {
+  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
+  font-size: 0.75rem;
+  color: var(--accent);
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+}
+
+.service-card__name {
+  margin: 0.4rem 0 0.35rem;
+}
+
+.service-card__description {
+  color: var(--muted);
+  margin: 0;
+  font-size: 0.95rem;
+}
+
+.site-footer {
+  padding: 1.5rem;
+  text-align: center;
+  color: var(--muted);
+  font-size: 0.85rem;
+  border-top: 1px solid var(--border);
+}
diff --git a/tests/seo-theme.test.ts b/tests/seo-theme.test.ts
new file mode 100644
index 0000000..7d28e40
--- /dev/null
+++ b/tests/seo-theme.test.ts
@@ -0,0 +1,40 @@
+import { describe, it, expect, beforeAll } from 'vitest';
+import { execSync } from 'node:child_process';
+import { readFileSync } from 'node:fs';
+
+describe('BaseLayout SEO tags and theming', () => {
+  beforeAll(() => {
+    execSync('npm run build', { stdio: 'inherit' });
+  });
+
+  it('sets canonical and hreflang alternates pointing at each other', () => {
+    const en = readFileSync('dist/en/index.html', 'utf-8');
+    const fr = readFileSync('dist/fr/index.html', 'utf-8');
+
+    expect(en).toContain('rel="canonical" href="https://www.ombrora.com/en/"');
+    expect(en).toContain('hreflang="fr" href="https://www.ombrora.com/fr/"');
+    expect(fr).toContain('rel="canonical" href="https://www.ombrora.com/fr/"');
+    expect(fr).toContain('hreflang="en" href="https://www.ombrora.com/en/"');
+  });
+
+  it('uses the locale-specific meta title and description', () => {
+    const en = readFileSync('dist/en/index.html', 'utf-8');
+    const fr = readFileSync('dist/fr/index.html', 'utf-8');
+
+    expect(en).toContain('<title>Ombrora — Security tracking and file tools</title>');
+    expect(fr).toContain('<title>Ombrora — Veille sécurité et outils de fichiers</title>');
+  });
+
+  it('includes a pre-paint theme script keyed on ombrora-theme', () => {
+    const en = readFileSync('dist/en/index.html', 'utf-8');
+    expect(en).toContain("localStorage.getItem('ombrora-theme')");
+    expect(en).toContain('prefers-color-scheme: light');
+  });
+
+  it('applies the global stylesheet (inlined or linked)', () => {
+    const en = readFileSync('dist/en/index.html', 'utf-8');
+    const hasInlineStyle = /<style>[\s\S]*--accent[\s\S]*<\/style>/.test(en);
+    const hasStylesheetLink = /<link rel="stylesheet"[^>]*href="[^"]+\.css"/.test(en);
+    expect(hasInlineStyle || hasStylesheetLink).toBe(true);
+  });
+});
