From ce8f93cb567b0469d5d423b2b478f5ecb3226c8f Mon Sep 17 00:00:00 2001
From: Neil <neil@stably.ai>
Date: Fri, 18 Sep 2026 02:04:20 -0700
Subject: [PATCH] fix(editor): preserve zero-start ordered lists

---
 .../editor/rich-markdown-list-item.ts         | 15 +++++++-
 .../editor/rich-markdown-ordered-list.test.ts | 35 ++++++++++++++++++
 .../editor/rich-markdown-ordered-list.ts      | 36 +++++++++++++++++--
 3 files changed, 83 insertions(+), 3 deletions(-)
 create mode 100644 src/renderer/src/components/editor/rich-markdown-ordered-list.test.ts

diff --git a/src/renderer/src/components/editor/rich-markdown-list-item.ts b/src/renderer/src/components/editor/rich-markdown-list-item.ts
index 9852bb5a822..7af460469c1 100644
--- a/src/renderer/src/components/editor/rich-markdown-list-item.ts
+++ b/src/renderer/src/components/editor/rich-markdown-list-item.ts
@@ -17,6 +17,17 @@ function markerWidth(context: RenderContext): number {
   return `${listStart(context) + (context.index ?? 0)}. `.length
 }
 
+function renderZeroStartMarker(rendered: string, context: RenderContext): string {
+  if (context.parentType !== 'orderedList' || listStart(context) !== 0) {
+    return rendered
+  }
+  const index = context.index ?? 0
+  const baseMarker = `${index + 1}. `
+  return rendered.startsWith(baseMarker)
+    ? `${index}. ${rendered.slice(baseMarker.length)}`
+    : rendered
+}
+
 function paragraphLineCount(node: JSONContent): number {
   const first = Array.isArray(node.content) ? node.content[0] : undefined
   if (first?.type !== 'paragraph') {
@@ -41,7 +52,9 @@ export const RichMarkdownListItem = ListItem.extend({
       return baseRenderMarkdown(node, helpers, context)
     }
     const width = markerWidth(context)
-    const lines = baseRenderMarkdown(node, helpers, context).split('\n')
+    const lines = renderZeroStartMarker(baseRenderMarkdown(node, helpers, context), context).split(
+      '\n'
+    )
     const paragraphLines = paragraphLineCount(node)
     const paragraph = indentParagraphContinuations(lines.slice(0, paragraphLines).join('\n'), width)
     const blocks = lines
diff --git a/src/renderer/src/components/editor/rich-markdown-ordered-list.test.ts b/src/renderer/src/components/editor/rich-markdown-ordered-list.test.ts
new file mode 100644
index 00000000000..1c4585beb11
--- /dev/null
+++ b/src/renderer/src/components/editor/rich-markdown-ordered-list.test.ts
@@ -0,0 +1,35 @@
+import { Editor } from '@tiptap/core'
+import { describe, expect, it } from 'vitest'
+import { encodeRawMarkdownHtmlForRichEditor } from './raw-markdown-html'
+import { createRichMarkdownExtensions } from './rich-markdown-extensions'
+import { createRichMarkdownEditorCodec } from './rich-markdown-source-transport'
+function roundTrip(source: string): string {
+  const codec = createRichMarkdownEditorCodec()
+  const editor = new Editor({
+    element: null,
+    extensions: createRichMarkdownExtensions({ codec }),
+    content: encodeRawMarkdownHtmlForRichEditor(source, codec),
+    contentType: 'markdown'
+  })
+  try {
+    return editor.getMarkdown().trimEnd()
+  } finally {
+    editor.destroy()
+  }
+}
+describe('ordered list start values', () => {
+  it('preserves a zero-start ordered list', () => {
+    const source = '0. zero\n1. one'
+    expect(roundTrip(source)).toBe(source)
+  })
+  it('keeps a zero-start list stable across repeated saves', () => {
+    let current = '0. zero\n1. one'
+    for (let cycle = 0; cycle < 3; cycle += 1) {
+      current = roundTrip(current)
+    }
+    expect(current).toBe('0. zero\n1. one')
+  })
+  it('does not change ordinary ordered lists', () => {
+    expect(roundTrip('1. one\n2. two')).toBe('1. one\n2. two')
+  })
+})
diff --git a/src/renderer/src/components/editor/rich-markdown-ordered-list.ts b/src/renderer/src/components/editor/rich-markdown-ordered-list.ts
index 4ccf53eae77..7347b3b373e 100644
--- a/src/renderer/src/components/editor/rich-markdown-ordered-list.ts
+++ b/src/renderer/src/components/editor/rich-markdown-ordered-list.ts
@@ -1,9 +1,30 @@
-import type { MarkdownTokenizer } from '@tiptap/core'
+import type { MarkdownParseResult, MarkdownToken, MarkdownTokenizer } from '@tiptap/core'
 import { OrderedList, ORDERED_LIST_MARKER_PATTERN } from '@tiptap/extension-list'
 
 const orderedListStart = new RegExp(`^\\s*(?:${ORDERED_LIST_MARKER_PATTERN})[.)]\\s`)
+const zeroOrderedListStart = /^\s*0[.)]\s/
 
 const baseTokenizer = OrderedList.config.markdownTokenizer as MarkdownTokenizer
+const baseParseMarkdown = OrderedList.config.parseMarkdown
+
+function withZeroStart(parsed: MarkdownParseResult, token: MarkdownToken): MarkdownParseResult {
+  if (
+    token.start !== 0 ||
+    !parsed ||
+    Array.isArray(parsed) ||
+    !('type' in parsed) ||
+    parsed.type !== 'orderedList'
+  ) {
+    return parsed
+  }
+  return {
+    ...parsed,
+    attrs: {
+      ...parsed.attrs,
+      start: 0
+    }
+  }
+}
 
 export const RichMarkdownOrderedList = OrderedList.extend({
   markdownTokenizer: {
@@ -13,7 +34,18 @@ export const RichMarkdownOrderedList = OrderedList.extend({
       if (!orderedListStart.test(src)) {
         return undefined
       }
-      return baseTokenizer.tokenize(src, tokens, lexer)
+      const token = baseTokenizer.tokenize(src, tokens, lexer)
+      if (zeroOrderedListStart.test(src) && token && typeof token === 'object') {
+        token.start = 0
+      }
+      return token
     }
+  },
+  parseMarkdown: (token, helpers) => {
+    const parsed = baseParseMarkdown?.(token, helpers)
+    if (!parsed) {
+      return []
+    }
+    return withZeroStart(parsed, token)
   }
 })