diff --git a/extension/src/popup/components/__tests__/settings-nav.test.ts b/extension/src/popup/components/__tests__/settings-nav.test.ts
new file mode 100644
index 0000000..544665c
--- /dev/null
+++ b/extension/src/popup/components/__tests__/settings-nav.test.ts
@@ -0,0 +1,22 @@
+import { describe, it, expect, vi } from 'vitest';
+
+vi.stubGlobal('chrome', {
+  storage: {
+    local: {
+      get: vi.fn((_keys: unknown, cb: (r: Record<string, unknown>) => void) => cb({})),
+      set: vi.fn((_data: unknown, cb?: () => void) => cb?.()),
+    },
+  },
+});
+
+import * as settingsMod from '../settings';
+
+describe('settings module contract', () => {
+  it('exports renderSettings as a function', () => {
+    expect(typeof settingsMod.renderSettings).toBe('function');
+  });
+
+  it('exports teardownSettings as a function', () => {
+    expect(typeof settingsMod.teardownSettings).toBe('function');
+  });
+});
diff --git a/extension/src/popup/styles.css b/extension/src/popup/styles.css
index ee28b08..21226d1 100644
--- a/extension/src/popup/styles.css
+++ b/extension/src/popup/styles.css
@@ -1699,3 +1699,92 @@ textarea {
 .relicario-toast--error   { background: #4a1f1f; color: #f0afaf; border: 1px solid #ab2b20; }
 .relicario-toast--info    { background: #1f2d4a; color: #afc8f0; border: 1px solid #1f6feb; }
 .type-card__desc  { font-size: 10px; color: var(--text-muted, #8b949e); margin-top: 2px; }
+
+/* === Settings layout === */
+.settings-layout {
+  display: flex;
+  height: 100%;
+  overflow: hidden;
+}
+
+.settings-nav {
+  width: 148px;
+  min-width: 148px;
+  border-right: 1px solid var(--border, #30363d);
+  padding: 12px 0;
+  overflow-y: auto;
+  flex-shrink: 0;
+}
+
+.settings-nav__group-label {
+  font-size: 10px;
+  text-transform: uppercase;
+  letter-spacing: 0.06em;
+  color: var(--text-muted, #8b949e);
+  padding: 8px 12px 4px;
+}
+
+.settings-nav__item {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  width: 100%;
+  padding: 7px 12px;
+  background: transparent;
+  border: none;
+  cursor: pointer;
+  font-size: 13px;
+  color: inherit;
+  text-align: left;
+}
+
+.settings-nav__item:hover { background: var(--bg-hover, #161b22); }
+.settings-nav__item--active { background: var(--bg-selected, #1c2d41); }
+
+.settings-nav__icon { font-size: 14px; flex-shrink: 0; }
+
+.settings-content {
+  flex: 1;
+  overflow-y: auto;
+  padding: 20px 24px;
+  min-width: 0;
+}
+
+.setting-row {
+  display: flex;
+  align-items: flex-start;
+  justify-content: space-between;
+  gap: 16px;
+  padding: 12px 0;
+  border-bottom: 1px solid var(--border-subtle, #21262d);
+}
+
+.setting-row:last-child { border-bottom: none; }
+
+.setting-row__info { flex: 1; }
+.setting-row__title { font-size: 13px; font-weight: 500; }
+.setting-row__desc  { font-size: 11px; color: var(--text-muted, #8b949e); margin-top: 2px; }
+.setting-row__control { flex-shrink: 0; }
+
+.settings-section-title {
+  font-size: 12px;
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+  color: var(--text-muted, #8b949e);
+  margin: 0 0 12px;
+  padding-bottom: 6px;
+  border-bottom: 1px solid var(--border, #30363d);
+}
+
+.setting-card {
+  padding: 12px 16px;
+  border-radius: 6px;
+  border: 1px solid var(--border, #30363d);
+  margin-bottom: 12px;
+}
+
+.setting-card--ok   { border-color: var(--success, #238636); background: rgba(35, 134, 54, 0.06); }
+.setting-card--warn { border-color: var(--gold, #b8860b);    background: rgba(184, 134, 11, 0.06); }
+
+.setting-card__status  { font-size: 13px; margin-bottom: 8px; }
+.setting-card__actions { display: flex; gap: 8px; }