diff --git a/apps/desktop/src/main/__tests__/icon-system-contract.test.ts b/apps/desktop/src/main/__tests__/icon-system-contract.test.ts
new file mode 100644
index 00000000000..6a6d9ea5037
--- /dev/null
+++ b/apps/desktop/src/main/__tests__/icon-system-contract.test.ts
@@ -0,0 +1,70 @@
+import { strict as assert } from 'node:assert';
+import { readFile } from 'node:fs/promises';
+import { join, resolve } from 'node:path';
+import { describe, it } from 'node:test';
+
+// Chrome icon-size contract (PR-ICON-SCALE).
+//
+// The hand-rolled desktop chrome (left-nav glyphs + the `buttonVariants` button
+// icon) shares ONE size, expressed as the `--icon-size` token, so nav and
+// buttons can't drift apart again (the original defect: nav at 18px while
+// buttons sat at size-4/1rem). Deliberately small dense-meta icons (12-14px)
+// and large hero/emphasis icons (20px+) stay set at their call sites — they are
+// intentional, not drift, so this contract does NOT flatten them, and it
+// explicitly forbids reintroducing a blanket `svg.lucide { width }` rule that
+// would silently resize every icon in the app.
+
+const rendererDir = join(process.cwd(), 'src', 'renderer');
+const repoRoot = resolve(process.cwd(), '..', '..');
+
+function ruleBody(css: string, selector: string): string | undefined {
+  const escaped = selector.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+  return css.match(new RegExp(`(?:^|\\n)${escaped}\\s*\\{([^}]*)\\}`))?.[1];
+}
+
+describe('icon system contract (single chrome size token)', () => {
+  it('defines --icon-size as the chrome glyph token', async () => {
+    const tokens = await readFile(join(rendererDir, 'maka-tokens.css'), 'utf8');
+    assert.match(tokens, /--icon-size:\s*16px/, 'chrome icon size token = 16px');
+  });
+
+  it('routes nav glyphs through the token, not hardcoded px', async () => {
+    const styles = await readFile(join(rendererDir, 'styles.css'), 'utf8');
+    const navIcon = ruleBody(styles, '.maka-nav-icon');
+    const navPrimary = ruleBody(styles, '.maka-nav-primary-icon');
+    const navRow = ruleBody(styles, '.maka-nav-row');
+    assert.ok(navIcon && navPrimary && navRow, 'nav rules must exist');
+    assert.match(navIcon, /width:\s*var\(--icon-size\)/);
+    assert.match(navIcon, /height:\s*var\(--icon-size\)/);
+    assert.doesNotMatch(navIcon, /\b(width|height):\s*\d+px/, '.maka-nav-icon must not re-hardcode px');
+    assert.match(navPrimary, /width:\s*var\(--icon-size\)/);
+    assert.match(navPrimary, /height:\s*var\(--icon-size\)/);
+    assert.doesNotMatch(navPrimary, /\b(width|height):\s*\d+px/, '.maka-nav-primary-icon must not re-hardcode px');
+    assert.match(navRow, /grid-template-columns:\s*var\(--icon-size\)/, 'nav-row glyph column tracks the token');
+  });
+
+  it('routes the shared button icon through the same token', async () => {
+    const ui = await readFile(join(repoRoot, 'packages', 'ui', 'src', 'ui.tsx'), 'utf8');
+    assert.match(
+      ui,
+      /\[&_svg\]:size-\[var\(--icon-size,1rem\)\]/,
+      'buttonVariants svg size must consume --icon-size (1rem fallback keeps @maka/ui standalone)',
+    );
+  });
+
+  it('forbids a blanket svg.lucide size rule (no app-wide resize hammer)', async () => {
+    const styles = await readFile(join(rendererDir, 'styles.css'), 'utf8');
+    const blanket = ruleBody(styles, 'svg.lucide');
+    assert.ok(
+      !blanket || !/\b(width|height)\s*:/.test(blanket),
+      'a global `svg.lucide { width/height }` rule would silently resize every '
+        + 'icon, including intentional 11-14px dense glyphs — it must not exist',
+    );
+  });
+
+  it('registers the iconography contract in design-system.md', async () => {
+    const doc = await readFile(join(repoRoot, 'docs', 'design-system.md'), 'utf8');
+    assert.match(doc, /###\s*1\.9\s*图标/, 'design-system.md must carry §1.9 图标');
+    assert.match(doc, /--icon-size\b/, 'doc must register the icon-size token');
+  });
+});
diff --git a/apps/desktop/src/main/__tests__/localized-main-shell-contract.test.ts b/apps/desktop/src/main/__tests__/localized-main-shell-contract.test.ts
index 9d3c330aafc..14842214726 100644
--- a/apps/desktop/src/main/__tests__/localized-main-shell-contract.test.ts
+++ b/apps/desktop/src/main/__tests__/localized-main-shell-contract.test.ts
@@ -556,7 +556,7 @@ describe('localized main shell contract', () => {
     // top-actions — references the one var(--maka-titlebar-control-safe-top),
     // with its own per-container correction constant (not asserted).
     assert.match(sidebarTopBar, /padding-top:\s*calc\(var\(--maka-titlebar-control-safe-top\) - \d+px\)/);
-    assert.match(styles, /(?:^|\n)\.maka-nav-icon\s*\{[\s\S]*?width:\s*18px[\s\S]*?height:\s*18px/);
+    // nav-icon sizing is owned by icon-system-contract.test.ts (the --icon-size token).
     assert.match(styles, /\.maka-sidebar-modules\b/);
     assert.doesNotMatch(styles, /\.maka-sidebar-module-hint\b/);
     assert.match(styles, /\.maka-nav-row\b/);
diff --git a/apps/desktop/src/renderer/maka-tokens.css b/apps/desktop/src/renderer/maka-tokens.css
index 4f07e926e67..539bb59546c 100644
--- a/apps/desktop/src/renderer/maka-tokens.css
+++ b/apps/desktop/src/renderer/maka-tokens.css
@@ -210,6 +210,8 @@
   --radius-button: 6px;        /* buttons get a small radius for tactility */
   --radius-modal: 8px;
   --spacing: 0.25rem;          /* 4px base step */
+  --icon-size: 16px;           /* chrome glyph size (nav + button icons); dense
+                                  meta (12-14) and hero (20+) stay call-site */
 
   /* === motion ===
      Custom easing curves per emil-design-eng — the built-in CSS easings
diff --git a/apps/desktop/src/renderer/styles.css b/apps/desktop/src/renderer/styles.css
index 4032c9f484b..1c44f3bd1c6 100644
--- a/apps/desktop/src/renderer/styles.css
+++ b/apps/desktop/src/renderer/styles.css
@@ -892,8 +892,8 @@ button:active {
 }
 
 .maka-nav-primary-icon {
-  width: 15px;
-  height: 15px;
+  width: var(--icon-size);
+  height: var(--icon-size);
   color: currentColor;
   flex: 0 0 auto;
 }
@@ -921,8 +921,8 @@ button:active {
 }
 
 .maka-nav-icon {
-  width: 18px;
-  height: 18px;
+  width: var(--icon-size);
+  height: var(--icon-size);
   color: var(--foreground-50);
   justify-self: center;
 }
@@ -947,7 +947,7 @@ button:active {
   margin-inline: 6px;
   min-height: 0;
   display: grid;
-  grid-template-columns: 18px minmax(0, 1fr) auto;
+  grid-template-columns: var(--icon-size) minmax(0, 1fr) auto;
   align-items: center;
   gap: 7px;
   border: 0;
diff --git a/docs/design-system.md b/docs/design-system.md
index 1aed09be968..75d0d13f046 100644
--- a/docs/design-system.md
+++ b/docs/design-system.md
@@ -216,6 +216,24 @@ background / foreground / accent (purple) / info (amber) / success (green) / des
 
 ---
 
+### 1.9 图标（Iconography）
+
+图标用 `lucide-react`，按**语境分档**，不是全局统一一个尺寸。
+
+| 档 | 尺寸 | 设定方式 | 用途 |
+|---|---|---|---|
+| chrome | `--icon-size`（16px） | token | 左侧 nav 图标 + `buttonVariants` 按钮内图标 |
+| 密集 meta | 12–14px | call-site `size={…}` | 状态点、footer 操作、chip、与小字号同行的内联图标 |
+| 强调 / hero | 20px+ | call-site `size={…}` | onboarding、错误页、settings about、permission 等单个语义图标 |
+
+规则：
+
+- **chrome 是唯一被 token 化的档。** nav 图标（`.maka-nav-icon` / `.maka-nav-primary-icon`）和 `packages/ui/src/ui.tsx` 的 `buttonVariants`（`[&_svg]:size-[var(--icon-size,1rem)]`）都消费 `--icon-size`，所以两者不会再各走各的（历史缺陷：nav 18px 而按钮 1rem）。改这一个 token 同时移动两者。
+- **密集 / hero 是 call-site 刻意值，不收敛。** 它们是有意的视觉层级，不是漂移；不要用全局 `svg.lucide { width }` 之类的规则一锅端，那会把 11–14px 的小图标静默放大、把 hero 压小。
+- `packages/ui/src/primitives/*` 是另一套组件库，有自己的响应式图标尺寸（`size-4.5`/`size-4`），不归本节管。
+
+---
+
 ## 2. 密度契约（Density contract）
 
 三档密度对应 `:root[data-ui-density="..."]`：
diff --git a/packages/ui/src/ui.tsx b/packages/ui/src/ui.tsx
index ac718b57a0f..d9753e8c56d 100644
--- a/packages/ui/src/ui.tsx
+++ b/packages/ui/src/ui.tsx
@@ -31,7 +31,7 @@ export const buttonVariants = cva(
     'transition-[background,border-color,box-shadow,transform,opacity] duration-150 ease-[var(--ease-maka)]',
     'focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 focus-visible:ring-offset-background',
     'active:scale-[0.98] disabled:pointer-events-none disabled:opacity-45',
-    '[&_svg]:size-4 [&_svg]:shrink-0',
+    '[&_svg]:size-[var(--icon-size,1rem)] [&_svg]:shrink-0',
   ],
   {
     variants: {