diff --git a/packages/app-core/src/lib/markdown.test.ts b/packages/app-core/src/lib/markdown.test.ts
index 85b7bfd4..24e7e2b0 100644
--- a/packages/app-core/src/lib/markdown.test.ts
+++ b/packages/app-core/src/lib/markdown.test.ts
@@ -4,6 +4,17 @@ import { describe, expect, it } from 'vitest'
 import { renderMarkdown } from './markdown'
 
 describe('renderMarkdown', () => {
+  it('hides leading YAML/TOML frontmatter in preview output', () => {
+    const yaml = renderMarkdown('---\ntitle: Hidden\ntags: [a, b]\n---\n\n# Visible')
+    expect(yaml).toContain('<h1 data-source-line="6">Visible</h1>')
+    expect(yaml).not.toContain('title: Hidden')
+    expect(yaml).not.toContain('<hr')
+
+    const toml = renderMarkdown('+++\ntitle = "Hidden"\n+++\n\nBody')
+    expect(toml).toContain('<p data-source-line="5">Body</p>')
+    expect(toml).not.toContain('title =')
+  })
+
   it('sanitizes raw HTML and javascript URLs', () => {
     const html = renderMarkdown(
       [
diff --git a/packages/app-core/src/styles/index.css b/packages/app-core/src/styles/index.css
index 891b05d0..c8a19fa6 100644
--- a/packages/app-core/src/styles/index.css
+++ b/packages/app-core/src/styles/index.css
@@ -2065,9 +2065,33 @@ html[data-completed-task-style="gray-strikethrough"] .cm-editor .cm-task-done *
   border-left: 1px solid rgb(var(--z-grey-0) / 0.13);
   border-right: 1px solid rgb(var(--z-grey-0) / 0.13);
 }
-.cm-editor .cm-frontmatter-line :is(.tok-meta, .tok-string, .tok-keyword, .tok-atom) {
+.cm-editor .cm-frontmatter-line
+  :is(
+    .tok-meta,
+    .tok-string,
+    .tok-keyword,
+    .tok-atom,
+    .tok-heading,
+    .tok-heading1,
+    .tok-heading2,
+    .tok-heading3,
+    .tok-heading4,
+    .tok-heading5,
+    .tok-heading6
+  ) {
   color: inherit;
 }
+/* Without a blank line before the closing `---`, CodeMirror's markdown parser
+ * can tokenize the previous frontmatter line as a setext heading. The metadata
+ * card owns frontmatter presentation, so suppress body heading typography here. */
+.cm-editor .cm-frontmatter-line
+  :is(.tok-heading, .tok-heading1, .tok-heading2, .tok-heading3, .tok-heading4, .tok-heading5, .tok-heading6) {
+  font-size: inherit;
+  font-weight: inherit;
+  line-height: inherit;
+  text-transform: none;
+  letter-spacing: 0;
+}
 /* The key (before the `:`) is a muted label; the value keeps the normal color. */
 .cm-editor .cm-frontmatter-key,
 .cm-editor .cm-frontmatter-key :is(.tok-meta, .tok-string, .tok-keyword, .tok-atom) {