diff --git a/src/channels/telegram-markdown-sanitize.test.ts b/src/channels/telegram-markdown-sanitize.test.ts
index 89fd8e393..076f4970b 100644
--- a/src/channels/telegram-markdown-sanitize.test.ts
+++ b/src/channels/telegram-markdown-sanitize.test.ts
@@ -65,4 +65,16 @@ describe('sanitizeTelegramLegacyMarkdown', () => {
   it('preserves indented list structure', () => {
     expect(sanitizeTelegramLegacyMarkdown('  - nested')).toBe('  • nested');
   });
+
+  it('flattens Markdown horizontal rules (---, ***, ___)', () => {
+    const input = 'before\n---\n***\n___\nafter';
+    expect(sanitizeTelegramLegacyMarkdown(input)).toBe(
+      'before\n⎯⎯⎯\n⎯⎯⎯\n⎯⎯⎯\nafter',
+    );
+  });
+
+  it('leaves horizontal rules inside code blocks alone', () => {
+    const input = '```\n---\n```';
+    expect(sanitizeTelegramLegacyMarkdown(input)).toBe(input);
+  });
 });
diff --git a/src/channels/telegram-markdown-sanitize.ts b/src/channels/telegram-markdown-sanitize.ts
index be9295467..c848c1132 100644
--- a/src/channels/telegram-markdown-sanitize.ts
+++ b/src/channels/telegram-markdown-sanitize.ts
@@ -28,6 +28,11 @@ export function sanitizeTelegramLegacyMarkdown(input: string): string {
   // as prose.
   text = text.replace(/^(\s*)[-+]\s+/gm, '$1• ');
 
+  // Flatten Markdown horizontal rules (bare --- / *** / ___ lines) to a
+  // plain Unicode divider. The parser doesn't understand HR syntax and the
+  // `*` / `_` characters would otherwise unbalance the delimiter counts below.
+  text = text.replace(/^[ \t]*[-_*]{3,}[ \t]*$/gm, '⎯⎯⎯');
+
   text = text.replace(/\*\*([^*\n]+?)\*\*/g, '*$1*');
   text = text.replace(/__([^_\n]+?)__/g, '_$1_');