fix(markdown): preserve horizontal rule markup

src/extensions/RichText.js

@@ -8,7 +8,6 @@ import { Extension } from '@tiptap/core'
 /* eslint-disable import/no-named-as-default */
 import Blockquote from '@tiptap/extension-blockquote'
 import Document from '@tiptap/extension-document'
-import HorizontalRule from '@tiptap/extension-horizontal-rule'
 import { ListItem } from '@tiptap/extension-list'
 import Placeholder from '@tiptap/extension-placeholder'
 import Text from '@tiptap/extension-text'
@@ -17,6 +16,7 @@ import { CharacterCount, Dropcursor, Gapcursor } from '@tiptap/extensions'
 import { common, createLowlight } from 'lowlight'
 import MentionSuggestion from '../components/Suggestion/Mention/suggestions.js'
 import Heading from '../nodes/Heading.js'
+import HorizontalRule from '../nodes/HorizontalRule.ts'
 import EmojiSuggestion from './../components/Suggestion/Emoji/suggestions.js'
 import LinkBubble from './../extensions/LinkBubble.js'
 import LinkPicker from './../extensions/LinkPicker.js'

src/markdownit/index.js

@@ -48,6 +48,10 @@ const markdownit = MarkdownIt('commonmark', { html: false, breaks: false })
 markdownit.renderer.rules.front_matter = (tokens, idx, options) =>
 	`<pre id="frontmatter"><code>${escapeHtml(tokens[idx].meta)}</code></pre>`
 
+// Render horizontal rules with markup attribute
+markdownit.renderer.rules.hr = (tokens, idx) =>
+	`<hr data-markup="${escapeHtml(tokens[idx].markup || '---')}" />\n`
+
 // Render lists with bullet attribute
 markdownit.renderer.rules.bullet_list_open = (tokens, idx, options) => {
 	tokens[idx].attrs = [

src/nodes/HorizontalRule.ts

@@ -0,0 +1,39 @@
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { nodeInputRule } from '@tiptap/core'
+import TiptapHorizontalRule from '@tiptap/extension-horizontal-rule'
+
+const HorizontalRule = TiptapHorizontalRule.extend({
+	addAttributes() {
+		return {
+			markup: {
+				default: '---',
+				parseHTML: (el) => el.getAttribute('data-markup') || '---',
+				renderHTML: (attrs) => {
+					if (!attrs.markup || attrs.markup === '---') {
+						return {}
+					}
+					return { 'data-markup': attrs.markup }
+				},
+			},
+		}
+	},
+
+	// Same triggers as upsream, but capture typed marker so it can be preserved
+	addInputRules() {
+		return [
+			nodeInputRule({
+				find: /^(?:(---|—-)|(___|\*\*\*)\s)$/,
+				type: this.type,
+				getAttributes: (match) => ({
+					markup: match[2] ?? '---',
+				}),
+			}),
+		]
+	},
+})
+
+export default HorizontalRule

src/tests/markdown.spec.js

@@ -135,6 +135,12 @@ describe('Markdown though editor', () => {
 		expect(markdownThroughEditor('foo\n\n---\n\nfoobar')).toBe(
 			'foo\n\n---\n\nfoobar',
 		)
+		expect(markdownThroughEditor('***\n\n- [ ] task\n\n***')).toBe(
+			'***\n\n- [ ] task\n\n***',
+		)
+		expect(markdownThroughEditor('___\n\n- [ ] task\n\n___')).toBe(
+			'___\n\n- [ ] task\n\n___',
+		)
 	})
 
 	test('table', () => {

src/tests/markdownit/commonmark.spec.js

@@ -24,6 +24,7 @@ describe('Commonmark', () => {
 			.replace(/<blockquote><\/blockquote>/g, '<blockquote>\n</blockquote>')
 			.replace(/<span class="keep-md">([^<]+)<\/span>/g, '$1')
 			.replace(/<br data-syntax=".{1,2}" \/>/g, '<br />\n')
+			.replace(/<hr data-markup="[*_-]+"/g, '<hr')
 			.replace(/<ul data-bullet="."/g, '<ul')
 	}