diff --git a/.github/pr-assets/preview-line-numbers.png b/.github/pr-assets/preview-line-numbers.png
new file mode 100644
index 00000000..9357ce15
Binary files /dev/null and b/.github/pr-assets/preview-line-numbers.png differ
diff --git a/apps/preview/app/src/components/code/code-block.tsx b/apps/preview/app/src/components/code/code-block.tsx
index 17cb98d2..549108af 100644
--- a/apps/preview/app/src/components/code/code-block.tsx
+++ b/apps/preview/app/src/components/code/code-block.tsx
@@ -1,6 +1,7 @@
 import { Check, Copy, Download } from 'iconoir-react';
 import beautify from 'js-beautify';
 import { useMemo, useState } from 'react';
+import type { ShikiTransformer } from 'shiki';
 import { createHighlighterCoreSync } from 'shiki/core';
 import { createJavaScriptRegexEngine } from 'shiki/engine/javascript';
 import shikiHtmlLang from 'shiki/langs/html.mjs';
@@ -15,6 +16,31 @@ const shiki = createHighlighterCoreSync({
   themes: [shikiGithubLightTheme, shikiGithubDarkHighContrastTheme]
 });
 
+const lineNumberTransformer: ShikiTransformer = {
+  name: 'jsx-email-preview-line-numbers',
+  line(node, line) {
+    const { children } = node;
+    node.children = [
+      {
+        type: 'element',
+        tagName: 'span',
+        properties: {
+          ariaHidden: 'true',
+          className: ['code-line-number'],
+          dataLineNumber: String(line)
+        },
+        children: [{ type: 'text', value: String(line) }]
+      },
+      {
+        type: 'element',
+        tagName: 'span',
+        properties: { className: ['code-line-content'] },
+        children
+      }
+    ];
+  }
+};
+
 interface CodeBlockProps {
   code: string;
   fileName: string;
@@ -26,17 +52,28 @@ export function formatCode(code: string, lang: CodeBlockProps['lang']) {
   return code;
 }
 
+export function codeToLineNumberedHtml(
+  code: string,
+  lang: CodeBlockProps['lang'],
+  theme: 'github-light' | 'github-dark-high-contrast'
+) {
+  if (lang === 'text') return escapeHtml(code);
+  return shiki.codeToHtml(code, {
+    lang,
+    theme,
+    transformers: [lineNumberTransformer]
+  });
+}
+
 export function CodeBlock({ code, fileName, lang }: CodeBlockProps) {
   const [copied, setCopied] = useState(false);
   const visibleCode = useMemo(() => formatCode(code, lang), [code, lang]);
   const html = useMemo(() => {
-    if (lang === 'text') return escapeHtml(visibleCode);
-    return shiki.codeToHtml(visibleCode, {
-      lang,
-      theme: document.documentElement.classList.contains('dark')
-        ? 'github-dark-high-contrast'
-        : 'github-light'
-    });
+    const theme = document.documentElement.classList.contains('dark')
+      ? 'github-dark-high-contrast'
+      : 'github-light';
+
+    return codeToLineNumberedHtml(visibleCode, lang, theme);
   }, [lang, visibleCode]);
 
   async function copy() {
@@ -68,7 +105,7 @@ export function CodeBlock({ code, fileName, lang }: CodeBlockProps) {
         </button>
       </div>
       <div
-        className="card-code h-full overflow-auto rounded-[6px] border border-[var(--border)] p-4 pr-24 text-xs leading-5"
+        className="card-code h-full overflow-auto rounded-[6px] border border-[var(--border)] py-4 pl-3 pr-24 text-xs leading-5"
         dangerouslySetInnerHTML={{ __html: html }}
       />
     </div>
@@ -76,8 +113,14 @@ export function CodeBlock({ code, fileName, lang }: CodeBlockProps) {
 }
 
 function escapeHtml(value: string) {
-  return `<pre class="shiki"><code>${value
-    .replaceAll('&', '&amp;')
-    .replaceAll('<', '&lt;')
-    .replaceAll('>', '&gt;')}</code></pre>`;
+  const lines = value.split('\n');
+  return `<pre class="shiki"><code>${lines
+    .map((line, index) => {
+      const lineNumber = index + 1;
+      return `<span class="line"><span class="code-line-number" aria-hidden="true" data-line-number="${lineNumber}">${lineNumber}</span><span class="code-line-content">${line
+        .replaceAll('&', '&amp;')
+        .replaceAll('<', '&lt;')
+        .replaceAll('>', '&gt;')}</span></span>`;
+    })
+    .join('')}</code></pre>`;
 }
diff --git a/apps/preview/app/src/index.css b/apps/preview/app/src/index.css
index 100de19a..a3fe8e75 100644
--- a/apps/preview/app/src/index.css
+++ b/apps/preview/app/src/index.css
@@ -683,6 +683,31 @@ body {
   padding: 0;
 }
 
+.card-code code {
+  display: grid;
+  min-width: max-content;
+}
+
+.card-code .line {
+  display: grid;
+  grid-template-columns: 2.5rem minmax(0, 1fr);
+  min-height: 1.25rem;
+}
+
+.card-code .code-line-number {
+  border-right: 1px solid var(--border);
+  color: var(--text-subtle);
+  padding-right: 0.75rem;
+  text-align: right;
+  user-select: none;
+}
+
+.card-code .code-line-content {
+  padding-left: 1rem;
+  padding-right: 1rem;
+  white-space: pre;
+}
+
 .code-block-wrap {
   position: relative;
 }
diff --git a/apps/preview/app/test/components/code/code-block.test.ts b/apps/preview/app/test/components/code/code-block.test.ts
new file mode 100644
index 00000000..4fffceed
--- /dev/null
+++ b/apps/preview/app/test/components/code/code-block.test.ts
@@ -0,0 +1,27 @@
+import { describe, expect, it } from 'vitest';
+
+import { codeToLineNumberedHtml, formatCode } from '../../../src/components/code/code-block';
+
+describe('codeToLineNumberedHtml', () => {
+  it('adds aligned line number markup to highlighted TSX code', () => {
+    const html = codeToLineNumberedHtml(
+      ['const subject = "Hi";', '<Text>{subject}</Text>'].join('\n'),
+      'tsx',
+      'github-light'
+    );
+
+    expect(html).toContain('class="line"');
+    expect(html).toContain('class="code-line-number"');
+    expect(html).toContain('data-line-number="1"');
+    expect(html).toContain('data-line-number="2"');
+    expect(html).toContain('class="code-line-content"');
+  });
+});
+
+describe('formatCode', () => {
+  it('formats HTML before it is highlighted', () => {
+    expect(formatCode('<main><p>Hello</p></main>', 'html')).toBe(
+      ['<main>', '  <p>Hello</p>', '</main>'].join('\n')
+    );
+  });
+});
diff --git a/apps/preview/scripts/pack-preview.ts b/apps/preview/scripts/pack-preview.ts
index 96e9fbb0..70d94203 100644
--- a/apps/preview/scripts/pack-preview.ts
+++ b/apps/preview/scripts/pack-preview.ts
@@ -68,6 +68,7 @@ const importHeader = `import React, {
 import ReactDOM from 'react-dom/client';
 import { createPortal } from 'react-dom';
 import { createRoot } from 'react-dom/client';
+import type { ShikiTransformer } from 'shiki';
 import {
   Check,
   Copy,
diff --git a/scripts/agents/capture-preview-line-numbers.ts b/scripts/agents/capture-preview-line-numbers.ts
new file mode 100644
index 00000000..d465b374
--- /dev/null
+++ b/scripts/agents/capture-preview-line-numbers.ts
@@ -0,0 +1,40 @@
+import { chromium } from 'playwright';
+
+const defaultUrl = 'http://localhost:8789';
+const defaultPath = '/tmp/preview-line-numbers.png';
+
+function getArg(name: string, fallback: string) {
+  const index = process.argv.indexOf(name);
+  return index === -1 ? fallback : (process.argv[index + 1] ?? fallback);
+}
+
+async function main() {
+  const url = getArg('--url', defaultUrl);
+  const path = getArg('--path', defaultPath);
+  const browser = await chromium.launch({ headless: true });
+  const page = await browser.newPage({
+    deviceScaleFactor: 2,
+    viewport: { height: 900, width: 1280 }
+  });
+
+  await page.goto(`${url}?lineNumbers=${Date.now()}`, { waitUntil: 'networkidle' });
+  await page.getByRole('button', { exact: true, name: 'Google Play Policy Update' }).click();
+  await page.waitForTimeout(900);
+  await page.getByRole('tab', { exact: true, name: 'JSX' }).click();
+  await page.waitForTimeout(300);
+
+  const card = page.locator('main article').filter({ hasText: 'Google Play Policy Update' });
+  await card.screenshot({ path });
+
+  const lineNumbers = await card.locator('.code-line-number').count();
+  const firstLine = await card.locator('.code-line-number').first().textContent();
+  const hasCodeContent = (await card.locator('.code-line-content').count()) > 0;
+  await browser.close();
+
+  console.log(JSON.stringify({ firstLine, hasCodeContent, lineNumbers, path }, null, 2));
+}
+
+main().catch((error) => {
+  console.error(error);
+  process.exitCode = 1;
+});