diff --git a/.gitignore b/.gitignore
index a237787..449034a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -42,5 +42,8 @@ tests/e2e/test_firmware.zip
 # NickelMenu build artifacts
 nickelmenu/kobo-config/
 
+# Proposals
+proposals/
+
 # Claude
 .claude
diff --git a/tests/e2e/integration.spec.js b/tests/e2e/integration.spec.js
index 1126a20..ccf4f8b 100644
--- a/tests/e2e/integration.spec.js
+++ b/tests/e2e/integration.spec.js
@@ -1150,3 +1150,57 @@ test.describe('Custom patches', () => {
     await expect(page.locator('#step-connect')).not.toBeHidden();
   });
 });
+
+// ============================================================
+// Build output
+// ============================================================
+
+test.describe('Build output', () => {
+  const path = require('path');
+  const distDir = path.join(__dirname, '..', '..', 'web', 'dist');
+
+  test('CSS cache-bust hash is present on style.css link', async () => {
+    const html = fs.readFileSync(path.join(distDir, 'index.html'), 'utf-8');
+    expect(html).toMatch(/css\/style\.css\?h=[0-9a-f]{8}/);
+  });
+
+  test('JS cache-bust hash is present on bundle.js script', async () => {
+    const html = fs.readFileSync(path.join(distDir, 'index.html'), 'utf-8');
+    expect(html).toMatch(/bundle\.js\?h=[0-9a-f]{8}/);
+  });
+
+  test('critical CSS is inlined with :root tokens', async () => {
+    const html = fs.readFileSync(path.join(distDir, 'index.html'), 'utf-8');
+    // :root block should be inside an inline <style> tag, not in a <link>
+    expect(html).toMatch(/<style>[^<]*:root\{[^}]*--primary:/);
+    // var() references should be used (not hardcoded hex colors for themed values)
+    expect(html).toMatch(/<style>[^<]*var\(--primary\)/);
+  });
+
+  test('style.css does not contain a :root block', async () => {
+    const css = fs.readFileSync(path.join(distDir, 'css', 'style.css'), 'utf-8');
+    expect(css).not.toContain(':root');
+  });
+
+  test('--primary-hover differs from --primary', async () => {
+    const critical = fs.readFileSync(
+      path.join(__dirname, '..', '..', 'web', 'src', 'css', 'critical.css'), 'utf-8'
+    );
+    const primary = critical.match(/--primary:\s*([^;]+);/);
+    const hover = critical.match(/--primary-hover:\s*([^;]+);/);
+    expect(primary).not.toBeNull();
+    expect(hover).not.toBeNull();
+    expect(primary[1].trim()).not.toBe(hover[1].trim());
+  });
+
+  test('no jszip script tag in built HTML', async () => {
+    const html = fs.readFileSync(path.join(distDir, 'index.html'), 'utf-8');
+    expect(html).not.toContain('jszip');
+  });
+
+  test('no unreplaced template placeholders in built HTML', async () => {
+    const html = fs.readFileSync(path.join(distDir, 'index.html'), 'utf-8');
+    expect(html).not.toMatch(/\{\{[\w-]+\}\}/);
+    expect(html).not.toContain('@critical-css');
+  });
+});
diff --git a/web/build.mjs b/web/build.mjs
index 751c10a..a627ff9 100644
--- a/web/build.mjs
+++ b/web/build.mjs
@@ -102,6 +102,18 @@ async function build() {
 
     let html = readFileSync(join(srcDir, 'index.html'), 'utf-8');
 
+    // Inline critical.css into the <head> so :root tokens and loading styles
+    // are available before style.css arrives on slow connections.
+    const criticalCss = readFileSync(join(srcDir, 'css', 'critical.css'), 'utf-8');
+    const { code: criticalMinified } = await esbuild.transform(criticalCss, {
+        loader: 'css',
+        minify: !isDev && !isWatch,
+    });
+    html = html.replace(
+        '<!-- @critical-css -->',
+        `<style>${criticalMinified.trimEnd()}</style>`
+    );
+
     // Remove all <script src="js/..."> tags
     html = html.replace(/\s*<script src="js\/[^"]*"><\/script>\n/g, '');
     // Add the bundle script before </body>
@@ -112,7 +124,7 @@ async function build() {
 
     // Update CSS cache bust
     html = html.replace(
-        /css\/style\.css\?[^"]*/,
+        /css\/style\.css(?:\?[^"]*)?/,
         `css/style.css?h=${cssHash}`
     );
 
diff --git a/web/src/css/critical.css b/web/src/css/critical.css
new file mode 100644
index 0000000..f457a57
--- /dev/null
+++ b/web/src/css/critical.css
@@ -0,0 +1,46 @@
+/*
+ * Critical CSS — inlined into index.html at build time.
+ *
+ * Contains the :root design tokens and the minimal styles needed to render
+ * the hero header and loading spinner before style.css arrives. Because this
+ * is inlined, var() references resolve immediately.
+ *
+ * This is the single source of truth for all CSS custom properties.
+ * style.css uses these variables but does not redefine them.
+ */
+
+:root {
+    --bg: #f5f5f7;
+    --card-bg: #fff;
+    --border: #d1d5db;
+    --border-light: #e5e7eb;
+    --text: #111827;
+    --text-secondary: #6b7280;
+    --primary: #01a7c4;
+    --primary-hover: #018da6;
+    --primary-light: #eff6ff;
+    --error-bg: #fef2f2;
+    --error-border: #fca5a5;
+    --error-text: #991b1b;
+    --warning-bg: #fffbeb;
+    --warning-border: #fcd34d;
+    --warning-text: #92400e;
+    --success-bg: #f0fdf4;
+    --success-border: #86efac;
+    --success-text: #166534;
+    --shadow: 0 1px 3px rgba(0, 0, 0, 0.06), 0 1px 2px rgba(0, 0, 0, 0.04);
+    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
+}
+
+body { background: var(--bg); color: var(--text); font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", sans-serif; margin: 0; }
+main { max-width: 640px; margin: 0 auto; padding: 2rem 1.5rem 4rem; }
+.hero { margin-bottom: 1.5rem; padding-bottom: 1rem; border-bottom: 1px solid var(--border-light); }
+h1 { font-size: 1.75rem; font-weight: 700; letter-spacing: -0.02em; margin: 0; }
+.hero-accent { color: var(--primary); font-weight: 600; }
+.beta-pill { font-size: 0.7rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.05em; background: var(--primary); color: #fff; padding: 0.35rem 0.7rem; border-radius: 10px; vertical-align: middle; position: relative; top: -0.15rem; margin-left: 5px; }
+.subtitle { color: var(--text-secondary); font-size: 0.95rem; margin-top: 0.25rem; }
+.initial-loader { display: flex; align-items: center; justify-content: center; gap: 0.75rem; padding: 2rem 0; }
+.initial-loader p { margin: 0; font-size: 0.93rem; color: var(--text-secondary); }
+.spinner { width: 22px; height: 22px; border: 2.5px solid var(--border-light); border-top-color: var(--primary); border-radius: 50%; animation: spin 0.7s linear infinite; flex-shrink: 0; }
+@keyframes spin { to { transform: rotate(360deg); } }
+[hidden] { display: none !important; }
diff --git a/web/src/css/style.css b/web/src/css/style.css
index be800f6..b22407b 100644
--- a/web/src/css/style.css
+++ b/web/src/css/style.css
@@ -6,41 +6,21 @@
     padding: 0;
 }
 
-:root {
-    --bg: #f5f5f7;
-    --card-bg: #fff;
-    --border: #d1d5db;
-    --border-light: #e5e7eb;
-    --text: #111827;
-    --text-secondary: #6b7280;
-    --primary: #01a7c4;
-    --primary-hover: #01a7c4;
-    --primary-light: #eff6ff;
-    --error-bg: #fef2f2;
-    --error-border: #fca5a5;
-    --error-text: #991b1b;
-    --warning-bg: #fffbeb;
-    --warning-border: #fcd34d;
-    --warning-text: #92400e;
-    --success-bg: #f0fdf4;
-    --success-border: #86efac;
-    --success-text: #166534;
-    --shadow: 0 1px 3px rgba(0, 0, 0, 0.06), 0 1px 2px rgba(0, 0, 0, 0.04);
-    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
+button, input, select, textarea {
+    font-family: inherit;
 }
 
+/* Design tokens (:root variables) are defined in critical.css, which is
+   inlined into <head> at build time — do not redefine them here. */
+
 body {
-    font-family: "Google Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", sans-serif !important;
+    font-family: "Google Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", sans-serif;
     background: var(--bg);
     color: var(--text);
     line-height: 1.6;
     -webkit-font-smoothing: antialiased;
 }
 
-button {
-    font-family: "Google Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", sans-serif !important;
-}
-
 main {
     max-width: 640px;
     margin: 0 auto;
@@ -863,6 +843,7 @@ input[type="file"] {
     flex-shrink: 0;
 }
 
+/* Also defined in critical.css (inlined into <head>) for the pre-CSS loading spinner */
 @keyframes spin {
     to { transform: rotate(360deg); }
 }
diff --git a/web/src/index.html b/web/src/index.html
index c2038ea..dca4d43 100644
--- a/web/src/index.html
+++ b/web/src/index.html
@@ -55,23 +55,9 @@
     <link rel="preload" href="/patches/downloads.json" as="fetch" crossorigin>
     <link rel="preload" href="/patches/index.json" as="fetch" crossorigin>
 
-    <!-- Inline critical styles so the hero + loader render before style.css arrives on slow connections -->
-    <style>
-        body { background: #f5f5f7; color: #111827; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", sans-serif; margin: 0; }
-        main { max-width: 640px; margin: 0 auto; padding: 2rem 1.5rem 4rem; }
-        .hero { margin-bottom: 1.5rem; padding-bottom: 1rem; border-bottom: 1px solid #e5e7eb; }
-        h1 { font-size: 1.75rem; font-weight: 700; letter-spacing: -0.02em; margin: 0; }
-        .hero-accent { color: #00bedf; font-weight: 600; }
-        .beta-pill { font-size: 0.7rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.05em; background: #00bedf; color: #fff; padding: 0.35rem 0.7rem; border-radius: 10px; vertical-align: middle; position: relative; top: -0.15rem; margin-left: 5px; }
-        .subtitle { color: #6b7280; font-size: 0.95rem; margin-top: 0.25rem; }
-        .initial-loader { display: flex; align-items: center; justify-content: center; gap: 0.75rem; padding: 2rem 0; }
-        .initial-loader p { margin: 0; font-size: 0.93rem; color: #6b7280; }
-        .spinner { width: 22px; height: 22px; border: 2.5px solid #e5e7eb; border-top-color: #00bedf; border-radius: 50%; animation: spin 0.7s linear infinite; flex-shrink: 0; }
-        @keyframes spin { to { transform: rotate(360deg); } }
-        [hidden] { display: none !important; }
-    </style>
+    <!-- Inlined at build time from css/critical.css so the hero + loader render before style.css arrives -->
+    <!-- @critical-css -->
     <link rel="stylesheet" href="css/style.css">
-    <script src="js/jszip.min.js"></script>
 </head>
 <body>
         <main>
