fix exponential backtracking in regex

apps/client/src/features/editor/components/slash-menu/menu-items.ts

@@ -389,6 +389,14 @@ const CommandGroups: SlashMenuGroupedItemsType = {
       command: ({ editor, range }: CommandProps) =>
         editor.chain().focus().deleteRange(range).setDetails().run(),
     },
+    {
+      title: "Tabs",
+      description: "Insert a multi-tab content block.",
+      searchTerms: ["tabs", "tabbed", "multi", "panel"],
+      icon: IconSitemap,
+      command: ({ editor, range }: CommandProps) =>
+        editor.chain().focus().deleteRange(range).insertTabs().run(),
+    },
     {
       title: "Callout",
       description: "Insert callout notice.",

apps/client/src/features/editor/components/tabs/tabs-menu.tsx

@@ -0,0 +1,167 @@
+import { BubbleMenu } from "@tiptap/react/menus";
+import React, { useCallback } from "react";
+import { EditorMenuProps, ShouldShowProps } from "../table/types/types";
+import { isEditorReady, isTextSelected } from "@docmost/editor-ext";
+import { Node as PMNode } from "@tiptap/pm/model";
+import { findParentNode, posToDOMRect } from "@tiptap/core";
+import classes from "../common/toolbar-menu.module.css";
+import { ActionIcon, Tooltip } from "@mantine/core";
+import { useTranslation } from "react-i18next";
+import {
+  IconChevronLeft,
+  IconChevronRight,
+  IconColumnInsertLeft,
+  IconColumnInsertRight,
+  IconColumnRemove,
+  IconTrashX,
+} from "@tabler/icons-react";
+
+const TabsMenu = React.memo(({ editor }: EditorMenuProps) => {
+  const { t } = useTranslation();
+
+  const shouldShow = useCallback(
+    ({ state }: ShouldShowProps) => {
+      if (!state) {
+        return false;
+      }
+
+      if (isTextSelected(editor)) return false;
+
+      return editor.isActive("tabs");
+    },
+    [editor]
+  );
+
+  const getReferencedVirtualElement = useCallback(() => {
+    if (!isEditorReady(editor)) return;
+    const { selection } = editor.state;
+    const predicate = (node: PMNode) => node.type.name === "tabs";
+    const parent = findParentNode(predicate)(selection);
+
+    if (parent) {
+      const dom = editor.view.nodeDOM(parent?.pos) as HTMLElement;
+      const domRect = dom.getBoundingClientRect();
+      return {
+        getBoundingClientRect: () => domRect,
+        getClientRects: () => [domRect],
+      };
+    }
+
+    const domRect = posToDOMRect(editor.view, selection.from, selection.to);
+    return {
+      getBoundingClientRect: () => domRect,
+      getClientRects: () => [domRect],
+    };
+  }, [editor]);
+
+  const handleAddTabLeft = useCallback(() => {
+    editor.chain().focus().insertTab("left").run();
+  }, [editor]);
+
+  const handleAddTabRight = useCallback(() => {
+    editor.chain().focus().insertTab("right").run();
+  }, [editor]);
+
+  const handleMoveTabRight = useCallback(() => {
+    editor.chain().focus().moveTab("right").run();
+  }, [editor]);
+
+  const handleMoveTabLeft = useCallback(() => {
+    editor.chain().focus().moveTab("left").run();
+  }, [editor]);
+
+  const handleDeleteTab = useCallback(() => {
+    editor.chain().focus().deleteTab().run();
+  }, [editor]);
+
+  const handleDelete = useCallback(() => {
+    editor.chain().focus().deleteTabs().run();
+  }, [editor]);
+
+  return (
+    <BubbleMenu
+      style={{ zIndex: 99 }}
+      editor={editor}
+      pluginKey="tabs-menu"
+      resizeDelay={0}
+      getReferencedVirtualElement={getReferencedVirtualElement}
+      shouldShow={shouldShow}
+      options={{
+        placement: "top",
+        offset: false,
+        flip: false,
+      }}
+    >
+      <div className={classes.toolbar}>
+        <Tooltip position="top" label={t("Add left tab")} withinPortal={false}>
+          <ActionIcon
+            onClick={handleAddTabLeft}
+            variant="subtle"
+            size="lg"
+            aria-label={t("Add left tab")}
+          >
+            <IconColumnInsertLeft size={18} />
+          </ActionIcon>
+        </Tooltip>
+        <Tooltip position="top" label={t("Add right tab")} withinPortal={false}>
+          <ActionIcon
+            onClick={handleAddTabRight}
+            variant="subtle"
+            size="lg"
+            aria-label={t("Add right tab")}
+          >
+            <IconColumnInsertRight size={18} />
+          </ActionIcon>
+        </Tooltip>
+        <Tooltip position="top" label={t("Delete tab")} withinPortal={false}>
+          <ActionIcon
+            onClick={handleDeleteTab}
+            variant="subtle"
+            size="lg"
+            aria-label={t("Delete tab")}
+          >
+            <IconColumnRemove size={18} />
+          </ActionIcon>
+        </Tooltip>
+
+        <div className={classes.divider} />
+
+        <Tooltip position="top" label={t("Move tab left")} withinPortal={false}>
+          <ActionIcon
+            onClick={handleMoveTabLeft}
+            variant="subtle"
+            size="lg"
+            aria-label={t("Move tab left")}
+          >
+            <IconChevronLeft size={18} />
+          </ActionIcon>
+        </Tooltip>
+
+        <Tooltip position="top" label={t("Move tab right")} withinPortal={false}>
+          <ActionIcon
+            onClick={handleMoveTabRight}
+            variant="subtle"
+            size="lg"
+            aria-label={t("Move tab right")}
+          >
+            <IconChevronRight size={18} />
+          </ActionIcon>
+        </Tooltip>
+        <div className={classes.divider} />
+
+        <Tooltip position="top" label={t("Delete")} withinPortal={false}>
+          <ActionIcon
+            onClick={handleDelete}
+            variant="subtle"
+            size="lg"
+            aria-label={t("Delete")}
+          >
+            <IconTrashX size={18} />
+          </ActionIcon>
+        </Tooltip>
+      </div>
+    </BubbleMenu>
+  );
+});
+
+export default TabsMenu;

apps/client/src/features/editor/components/tabs/tabs-view.tsx

@@ -0,0 +1,140 @@
+import React, {
+  ChangeEvent,
+  useCallback,
+  useEffect,
+  useMemo,
+  useRef,
+  useState,
+  type KeyboardEvent,
+} from "react";
+import { NodeViewContent, NodeViewWrapper, type NodeViewProps } from "@tiptap/react";
+import { Tabs, TextInput } from "@mantine/core";
+
+export default function TabsView(props: NodeViewProps) {
+  const { node, editor, getPos } = props;
+  const isEditable = editor.isEditable;
+  const allowFocusRef = useRef(false);
+
+  const tabs = useMemo(() => {
+    return Array.from({ length: node.childCount }, (_, index) => {
+      const labelNode = node.child(index)?.child(0);
+      const labelText = labelNode?.textContent;
+      const labelId = node.child(index)?.attrs?.id;
+
+      return {
+        label: labelText ?? "",
+        id: labelId ?? index,
+      };
+    });
+  }, [node]);
+
+  const activeTab = clampIndex(node.attrs.activeTab);
+  const [activeLabel, setActiveLabel] = useState(tabs[activeTab].label ?? "");
+
+  useEffect(() => {
+    setActiveLabel(tabs[activeTab].label);
+  }, [activeTab, tabs]);
+
+  const handleMouseDown = useCallback((event: React.MouseEvent) => {
+    const previous = document.activeElement as HTMLElement | null;
+    const input = event.currentTarget;
+
+    if (!previous?.contains(input)) {
+      allowFocusRef.current = true;
+      return;
+    }
+
+    allowFocusRef.current = true;
+  }, []);
+
+  const handleFocus = useCallback(
+    (event: React.FocusEvent<HTMLInputElement>) => {
+      if (!allowFocusRef.current || !isEditable) {
+        event.preventDefault();
+        event.target.blur();
+      }
+    },
+    [isEditable]
+  );
+
+  const handleBlur = useCallback(() => {
+    allowFocusRef.current = false;
+  }, []);
+
+  const commitLabel = useCallback(
+    (event: ChangeEvent<HTMLInputElement>) => {
+      const label = event.currentTarget.value;
+      setActiveLabel(label);
+
+      if (label === tabs[activeTab].label) return;
+      if (typeof getPos === "function") {
+        editor.commands.updateTabLabel?.(activeTab, label, getPos());
+      }
+    },
+    [activeTab, editor, getPos, tabs]
+  );
+
+  const handleLabelKeyDown = useCallback(
+    (event: KeyboardEvent<HTMLInputElement>) => {
+      event.stopPropagation();
+      if (event.key === "Escape") {
+        event.preventDefault();
+        event.currentTarget.blur();
+      }
+    },
+    []
+  );
+
+  return (
+    <NodeViewWrapper data-type="tabs">
+      <Tabs value={String(activeTab)}>
+        <Tabs.List style={{ marginBottom: 10 }}>
+          {tabs.map(({ label, id }, index) => (
+            <Tabs.Tab
+              key={id}
+              value={index.toString()}
+              onFocus={(event) => event.currentTarget.blur()}
+              onClick={(e) => {
+                e.preventDefault();
+                if (typeof getPos === "function") {
+                  editor.commands.setActiveTab?.(index, getPos());
+                }
+              }}
+            >
+              <TextInput
+                aria-label="Edit tab label"
+                onMouseDown={handleMouseDown}
+                onFocus={handleFocus}
+                onBlur={handleBlur}
+                onChange={commitLabel}
+                onKeyDown={handleLabelKeyDown}
+                variant="unstyled"
+                size="xs"
+                value={
+                  index === activeTab && allowFocusRef.current ? activeLabel : label
+                }
+                styles={{
+                  input: {
+                    minWidth: 80,
+                    padding: 0,
+                    cursor: "pointer",
+                  },
+                }}
+              />
+            </Tabs.Tab>
+          ))}
+        </Tabs.List>
+      </Tabs>
+
+      <div className="dm-tabs__content">
+        <NodeViewContent as="div" />
+      </div>
+    </NodeViewWrapper>
+  );
+}
+
+const clampIndex = (value: unknown, length = Number.MAX_SAFE_INTEGER) => {
+  const parsed = Number(value ?? 0);
+  if (!Number.isFinite(parsed) || length <= 0) return 0;
+  return Math.max(0, Math.min(Math.trunc(parsed), length - 1));
+};

apps/client/src/features/editor/extensions/drag-handle.ts

@@ -5,8 +5,9 @@ import {
   PluginKey,
   TextSelection,
 } from "@tiptap/pm/state";
-import { Fragment, Slice, Node } from "@tiptap/pm/model";
+import { Fragment, Slice } from "@tiptap/pm/model";
-import { EditorView } from "@tiptap/pm/view";
+import type { Node, ResolvedPos } from "@tiptap/pm/model";
+import type { EditorView } from "@tiptap/pm/view";
 
 export interface GlobalDragHandleOptions {
   /**
@@ -150,9 +151,126 @@ function isCustomNodeDOM(
   return false;
 }
 
+function getDirectTarget($pos: ResolvedPos, ancestorDepth: number) {
+  const ancestor = $pos.node(ancestorDepth);
+
+  if (ancestor.childCount === 0) return null;
+
+  if ($pos.depth > ancestorDepth) {
+    const childDepth = ancestorDepth + 1;
+    return {
+      pos: $pos.before(childDepth),
+      node: $pos.node(childDepth),
+    };
+  }
+
+  const index = $pos.index(ancestorDepth);
+  const childIndex = Math.min(index, ancestor.childCount - 1);
+  if (childIndex < 0) return null;
+
+  return {
+    pos: $pos.posAtIndex(childIndex, ancestorDepth),
+    node: ancestor.child(childIndex),
+  };
+}
+
+type DragSource = { from: number; to: number; node: Node };
+
+function dragSourceFromDOM(view: EditorView, dom: Element): DragSource | null {
+  let pos: number;
+  try {
+    pos = view.posAtDOM(dom, 0);
+  } catch {
+    return null;
+  }
+
+  const $pos = view.state.doc.resolve(pos);
+  if ($pos.depth === 0) return null;
+
+  const from = $pos.before($pos.depth);
+  const node = $pos.node($pos.depth);
+  return { from, to: from + node.nodeSize, node };
+}
+
+function resolveMoveSource(
+  view: EditorView,
+  hint: DragSource | null,
+): DragSource | null {
+  const { state } = view;
+
+  if (hint) {
+    const current = state.doc.nodeAt(hint.from);
+    if (current?.eq(hint.node)) return hint;
+  }
+
+  if (state.selection instanceof NodeSelection) {
+    return {
+      from: state.selection.from,
+      to: state.selection.from + state.selection.node.nodeSize,
+      node: state.selection.node,
+    };
+  }
+
+  return null;
+}
+
+function moveNodeWithinTabPanel(
+  view: EditorView,
+  dropPos: number,
+  source: DragSource,
+): boolean {
+  const { state } = view;
+  const { from: sourceFrom, to: sourceTo, node: sourceNode } = source;
+
+  const $drop = state.doc.resolve(dropPos);
+  const panelDepth = view.state.doc.resolve(dropPos).depth
+  if (panelDepth < 0) return false;
+
+  if (dropPos > sourceFrom && dropPos < sourceTo) return false;
+
+  let insertPos: number;
+  const target = getDirectTarget($drop, panelDepth);
+  if (!target) {
+    insertPos = $drop.start(panelDepth);
+  } else {
+    const targetStart = target.pos;
+    const targetEnd = targetStart + target.node.nodeSize;
+    const midpoint = (targetStart + targetEnd) / 2;
+    insertPos = dropPos >= midpoint ? targetEnd : targetStart;
+  }
+
+  // Already in place.
+  if (insertPos === sourceFrom || insertPos === sourceTo) return false;
+
+  const tr = state.tr;
+  tr.delete(sourceFrom, sourceTo);
+
+  const insertAt = tr.mapping.map(insertPos, -1);
+  const $insert = tr.doc.resolve(insertAt);
+  const index = $insert.index();
+
+  if (!$insert.parent.canReplace(index, index, Fragment.from(sourceNode))) {
+    return false;
+  }
+
+  tr.insert(insertAt, sourceNode);
+
+  const $placed = tr.doc.resolve(
+    Math.min(insertAt, tr.doc.content.size),
+  );
+  tr.setSelection(NodeSelection.near($placed));
+  tr.scrollIntoView();
+
+  view.dispatch(tr);
+  return true;
+}
+
+const NON_PROMOTABLE_PARENTS = new Set(["tabs", "tab", "tabPanel"]);
+
 function calcNodePos(pos: number, view: EditorView) {
   const $pos = view.state.doc.resolve(pos);
-  if ($pos.depth > 1) return $pos.before($pos.depth);
+  if ($pos.depth > 1 && !NON_PROMOTABLE_PARENTS.has($pos.node($pos.depth).type.name))
+    return $pos.before($pos.depth);
   return pos;
 }
 
@@ -160,6 +278,8 @@ export function DragHandlePlugin(
   options: GlobalDragHandleOptions & { pluginKey: string },
 ) {
   let listType = "";
+  let dragSource: DragSource | null = null;
+
   function handleDragStart(event: DragEvent, view: EditorView) {
     view.focus();
 
@@ -176,6 +296,8 @@ export function DragHandlePlugin(
 
     if (!(node instanceof Element)) return;
 
+    dragSource = dragSourceFromDOM(view, node);
+
     let draggedNodePos = nodePosAtDOM(node, view, options);
     if (draggedNodePos == null || draggedNodePos < 0) return;
     draggedNodePos = calcNodePos(draggedNodePos, view);
@@ -401,6 +523,7 @@ export function DragHandlePlugin(
           );
 
           const notDragging = node?.closest(".not-draggable");
+          const notDraggingMatch = node?.matches(".not-draggable-match")
           const excludedTagList = options.excludedTags
             .concat(["ol", "ul"])
             .join(", ");
@@ -408,7 +531,8 @@ export function DragHandlePlugin(
           if (
             !(node instanceof Element) ||
             node.matches(excludedTagList) ||
-            notDragging
+            notDragging ||
+            notDraggingMatch
           ) {
             hideDragHandle();
             return;
@@ -496,6 +620,22 @@ export function DragHandlePlugin(
           const isDroppedInsideList =
             resolvedPos.parent.type.name === "listItem";
 
+          const isDroppedInsideTabPanel =
+            resolvedPos.parent.type.name === "tabPanel";
+
+          if (isDroppedInsideTabPanel) {
+            const source = resolveMoveSource(view, dragSource);
+            const moved = source
+              ? moveNodeWithinTabPanel(view, dropPos.pos, source)
+              : false;
+   
+            // even when not moved swallow the drop so ProseMirror doesn't insert a copy.
+            event.preventDefault();
+            view.dragging = null;
+            dragSource = null;
+            return moved;
+          }
+
           // If the selected node is a list item and is not dropped inside a list, we need to wrap it inside <ol> tag otherwise ol list items will be transformed into ul list item when dropped
           if (
             view.state.selection instanceof NodeSelection &&
@@ -513,6 +653,7 @@ export function DragHandlePlugin(
         },
         dragend: (view) => {
           view.dom.classList.remove("dragging");
+          dragSource = null;
         },
       },
     },
@@ -526,6 +667,7 @@ const GlobalDragHandle = Extension.create({
     return {
       dragHandleWidth: 20,
       scrollThreshold: 100,
+      dragHandleSelector: undefined,
       excludedTags: [],
       customNodes: [],
       atomNodes: [],

apps/client/src/features/editor/extensions/extensions.ts

@@ -62,6 +62,10 @@ import {
   TransclusionReference,
   TableView,
   BaseEmbed as BaseEmbedNode,
+  Tabs,
+  Tab,
+  TabLabel,
+  TabPanel,
 } from "@docmost/editor-ext";
 import {
   randomElement,
@@ -90,6 +94,7 @@ import ExcalidrawView from "@/features/editor/components/excalidraw/excalidraw-v
 import EmbedView from "@/features/editor/components/embed/embed-view.tsx";
 import PdfView from "@/features/editor/components/pdf/pdf-view.tsx";
 import SubpagesView from "@/features/editor/components/subpages/subpages-view.tsx";
+import TabsView from "@/features/editor/components/tabs/tabs-view.tsx";
 import TransclusionView from "@/features/editor/components/transclusion/transclusion-view.tsx";
 import TransclusionReferenceView from "@/features/editor/components/transclusion/transclusion-reference-view.tsx";
 import { BaseEmbedView } from "@/features/editor/components/base-embed/base-embed-view.tsx";
@@ -234,7 +239,7 @@ export const mainExtensions = [
   Typography,
   TrailingNode,
   GlobalDragHandle.configure({
-    customNodes: ["transclusionSource", "transclusionReference"],
+    customNodes: ["transclusionSource", "transclusionReference", "tabPanel"],
     atomNodes: ["base"],
   }),
   TextStyle,
@@ -289,6 +294,12 @@ export const mainExtensions = [
   Details,
   DetailsSummary,
   DetailsContent,
+  Tabs.configure({
+    view: TabsView,
+  }),
+  Tab,
+  TabLabel,
+  TabPanel,
   Youtube.configure({
     addPasteHandler: false,
     controls: true,

apps/client/src/features/editor/page-editor.tsx

@@ -82,6 +82,7 @@ import {
   getCollabSocket,
   releaseCollabSocket,
 } from "@/features/editor/collab-socket";
+import TabsMenu from "./components/tabs/tabs-menu";
 
 interface PageEditorProps {
   pageId: string;
@@ -453,6 +454,7 @@ function CollabPageEditor({
             <ExcalidrawMenu editor={editor} />
             <DrawioMenu editor={editor} />
             <ColumnsMenu editor={editor} />
+            <TabsMenu editor={editor} />
           </div>
         )}
         {editor && !editorIsEditable && (editable || canComment) && (

apps/client/src/features/editor/styles/index.css

@@ -17,4 +17,5 @@
 @import "./indent.css";
 @import "./columns.css";
 @import "./status.css";
+@import "./tabs.css";
 @import "./base-embed.css";

apps/client/src/features/editor/styles/tabs.css

@@ -0,0 +1,15 @@
+.ProseMirror {
+  [data-type="tabs"] {
+    button {
+      outline: none;
+    }
+  }
+  
+  [data-type="tabLabel"] {
+    display: none;
+  }
+
+  [data-type="tabPanel"] {
+    outline: none;
+  }
+}

apps/server/src/collaboration/collaboration.util.ts

@@ -45,6 +45,10 @@ import {
   TransclusionSource,
   TransclusionReference,
   BaseEmbed,
+  Tabs,
+  Tab,
+  TabLabel,
+  TabPanel,
 } from '@docmost/editor-ext';
 import { generateText, getSchema, JSONContent } from '@tiptap/core';
 import { generateHTML, generateJSON } from '../common/helpers/prosemirror/html';
@@ -87,6 +91,10 @@ export const tiptapExtensions = [
   Details,
   DetailsContent,
   DetailsSummary,
+  Tabs,
+  Tab,
+  TabLabel,
+  TabPanel,
   CustomTable,
   TableCell,
   TableRow,

packages/editor-ext/src/index.ts

@@ -30,6 +30,7 @@ export * from "./lib/shared-storage";
 export * from "./lib/recreate-transform";
 export * from "./lib/columns";
 export * from "./lib/status";
+export * from "./lib/tabs";
 export * from "./lib/pdf";
 export * from "./lib/page-break";
 export * from "./lib/resizable-nodeview";

packages/editor-ext/src/lib/markdown/utils/marked.utils.ts

@@ -2,6 +2,7 @@ import { marked } from "marked";
 import { calloutExtension } from "./callout.marked";
 import { mathBlockExtension } from "./math-block.marked";
 import { mathInlineExtension } from "./math-inline.marked";
+import { tabsExtension } from "./tabs.marked";
 
 marked.use({
   renderer: {
@@ -34,7 +35,12 @@ marked.use({
 });
 
 marked.use({
-  extensions: [calloutExtension, mathBlockExtension, mathInlineExtension],
+  extensions: [
+    calloutExtension,
+    mathBlockExtension,
+    mathInlineExtension,
+    tabsExtension,
+  ],
 });
 
 marked.setOptions({ breaks: true });

packages/editor-ext/src/lib/markdown/utils/tabs.marked.ts

@@ -0,0 +1,152 @@
+import { marked, type Token } from 'marked';
+
+interface MarkdownTab {
+  label: string;
+  text: string;
+  forceActive: boolean;
+}
+
+interface TabbedToken {
+  type: 'tabbed';
+  raw: string;
+  tabs: MarkdownTab[];
+  activeTabIndex: number;
+}
+
+const HEADER_RE =
+  /^===([!+])?\s*["'“”‘’]((?:\\["\\]|[^\\"'“”‘’\n])+?)["'“”‘’]\s*$/gm;
+
+export const tabsExtension = {
+  name: 'tabbed',
+  level: 'block',
+  start(src: string) {
+    return src.search(/^===(?:[!+])?\s*["'“”‘’]/m);
+  },
+  tokenizer(src: string): TabbedToken | undefined {
+    if (src.indexOf('===') === -1) return;
+
+    const headers: Array<{
+      index: number;
+      raw: string;
+      marker: string;
+      label: string;
+    }> = [];
+
+    HEADER_RE.lastIndex = 0;
+
+    for (let m = HEADER_RE.exec(src); m !== null; m = HEADER_RE.exec(src)) {
+      headers.push({
+        index: m.index,
+        raw: m[0],
+        marker: m[1] ?? '',
+        label: unescapeTabLabel(m[2].trim()),
+      });
+    }
+
+    if (headers.length < 1 || headers[0].index !== 0) return;
+
+    const tabs: MarkdownTab[] = [];
+    let consumed = 0;
+    let breakOutOfTabSet = false;
+
+    for (let i = 0; i < headers.length; i++) {
+      const h = headers[i];
+
+      if (i > 0 && h.marker === '!') break;
+
+      const headerEnd = h.index + h.raw.length;
+      const bodyStart =
+        src.charCodeAt(headerEnd) === 10 ? headerEnd + 1 : headerEnd;
+
+      const next = headers[i + 1];
+      const bodyLimit = next ? next.index : src.length;
+      let bodyEnd = bodyLimit;
+      let lineStart = bodyStart;
+      
+      while (lineStart < bodyLimit) {
+        const newlineIndex = src.indexOf('\n', lineStart);
+        const lineEnd =
+          newlineIndex === -1 || newlineIndex > bodyLimit
+            ? bodyLimit
+            : newlineIndex;
+
+        const line = src.slice(lineStart, lineEnd);
+        const isBlank = line.trim() === '';
+        const isIndented = /^( {2,4}|\t)/.test(line);
+
+        if (!isBlank && !isIndented) {
+          bodyEnd = lineStart;
+          breakOutOfTabSet = true;
+          break;
+        }
+
+        lineStart = lineEnd < bodyLimit ? lineEnd + 1 : bodyLimit;
+      }
+
+      let body = src.slice(bodyStart, bodyEnd).replace(/\n+$/, '');
+
+      if (body.length > 0) {
+        body = body
+          .split('\n')
+          .map((line) => line.replace(/^(?:\t| {2,4})/, ''))
+          .join('\n');
+      }
+
+      tabs.push({
+        label: h.label,
+        text: body,
+        forceActive: h.marker === '+',
+      });
+
+      consumed = bodyEnd;
+
+      if (breakOutOfTabSet) break;
+    }
+
+    if (tabs.length < 1) return;
+
+    const forcedActiveIndex = tabs.findIndex((t) => t.forceActive);
+
+    return {
+      type: 'tabbed',
+      raw: src.slice(0, consumed),
+      tabs,
+      activeTabIndex: Math.max(forcedActiveIndex, 0),
+    };
+  },
+  renderer(token: Token) {
+    const tabbedToken = token as TabbedToken;
+
+    const activeTabIndex = Math.max(
+      0,
+      Math.min(tabbedToken.activeTabIndex ?? 0, tabbedToken.tabs.length - 1),
+    );
+
+    const sections = tabbedToken.tabs.map((tab, index) => {
+      const label = escapeHtml(tab.label);
+      const panel = marked.parse(tab.text || '').toString();
+      const isActive = index === activeTabIndex;
+
+      const activeAttrs = isActive
+        ? 'data-tab-active="true"'
+        : 'data-tab-active="false"';
+
+      return `<div data-type="tab" aria-hidden="true" ${activeAttrs}><div data-type="tabLabel">${label}</div><div data-type="tabPanel" >${panel}</div></div>`;
+    });
+
+    return `<div data-type="tabs" data-active-tab="${activeTabIndex}">${sections.join('')}</div>`;
+  },
+};
+
+function unescapeTabLabel(value: string): string {
+  return value.replace(/\\(["\\])/g, '$1');
+}
+
+function escapeHtml(value: string): string {
+  return value
+    .replace(/&/g, '&amp;')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;')
+    .replace(/"/g, '&quot;')
+    .replace(/'/g, '&#39;');
+}

packages/editor-ext/src/lib/markdown/utils/turndown.utils.ts

@@ -24,6 +24,7 @@ export function htmlToMarkdown(html: string): string {
     TurndownPluginGfm.tables,
     TurndownPluginGfm.strikethrough,
     TurndownPluginGfm.highlightedCodeBlock,
+    tabs,
     taskList,
     callout,
     preserveDetail,
@@ -38,6 +39,64 @@ export function htmlToMarkdown(html: string): string {
   return turndownService.turndown(html).replaceAll('<br>', ' ');
 }
 
+const hasPreviousTabs = (node: HTMLElement) => {
+  // we want to make this as cheap as reasonable since it
+  // would be preferable to return a false positive
+  // than to make the editor noticably slower
+  let el = node.previousElementSibling;
+  let checks = 0;
+
+  while (el) {
+    if (el.getAttribute('data-type') === 'tabs') return true;
+    el = el.previousElementSibling;
+    checks += 1;
+
+    if (checks === 100) return true;
+  }
+
+  return false;
+};
+
+function tabs(turndownService: _TurndownService) {
+  turndownService.addRule('tabs', {
+    filter: (node: HTMLInputElement) =>
+      node.nodeName === 'DIV' && node.getAttribute('data-type') === 'tabs',
+    replacement: (content: string, node: HTMLInputElement) => {
+      const tabNodes = Array.from(
+        node.querySelectorAll(':scope > div[data-type="tab"]'),
+      );
+      if (tabNodes.length === 0) return content;
+
+      const isNestedTabsNode =
+        node.parentElement?.closest('div[data-type="tabs"]') !== null;
+
+      const tabBlocks = tabNodes.map((tabNode, index) => {
+        const labelNode = tabNode.querySelector(
+          ':scope > div[data-type="tabLabel"]',
+        );
+        const panelNode = tabNode.querySelector(
+          ':scope > div[data-type="tabPanel"]',
+        );
+
+        const label = sanitizeTabLabel(labelNode?.textContent || 'Tab');
+        const panelMarkdown = panelNode
+          ? turndownService.turndown(panelNode.innerHTML).trim()
+          : '';
+
+        const isFirstTabInSet = index === 0;
+        const marker =
+          isFirstTabInSet && !isNestedTabsNode && hasPreviousTabs(node)
+            ? '!'
+            : '';
+
+        return `===${marker} "${label}"\n${indentMarkdownBlock(panelMarkdown)}`;
+      });
+
+      return `\n\n${tabBlocks.join('\n\n')}\n\n`;
+    },
+  });
+}
+
 function listParagraph(turndownService: _TurndownService) {
   turndownService.addRule('paragraph', {
     filter: ['p'],
@@ -53,7 +112,9 @@ function listParagraph(turndownService: _TurndownService) {
 function orderedListItem(turndownService: _TurndownService) {
   turndownService.addRule('orderedListItem', {
     filter: function (node: HTMLInputElement) {
-      return node.nodeName === 'LI' && node.getAttribute('data-type') !== 'taskItem';
+      return (
+        node.nodeName === 'LI' && node.getAttribute('data-type') !== 'taskItem'
+      );
     },
     replacement: (content: string, node: HTMLInputElement, options: any) => {
       const parent = node.parentNode as HTMLElement;
@@ -114,9 +175,7 @@ function taskList(turndownService: _TurndownService) {
       const prefix = `- ${isChecked ? '[x]' : '[ ]'} `;
 
       return (
-        prefix +
+        prefix + text + (node.nextSibling && !/\n$/.test(text) ? '\n' : '')
-        text +
-        (node.nextSibling && !/\n$/.test(text) ? '\n' : '')
       );
     },
   });
@@ -211,10 +270,25 @@ function video(turndownService: _TurndownService) {
     replacement: function (_content: string, node: HTMLInputElement) {
       const src = node.getAttribute('src') || '';
       const ariaLabel = node.getAttribute('aria-label');
-      const name = sanitizeMdLinkText(
+      const name = sanitizeMdLinkText(ariaLabel || getBasename(src) || src);
-        ariaLabel || getBasename(src) || src,
-      );
       return '[' + name + '](' + src + ')';
     },
   });
 }
+
+function sanitizeTabLabel(value: string): string {
+  return value
+    .replace(/[\r\n]+/g, ' ')
+    .replace(/\\/g, '\\\\')
+    .replace(/"/g, '\\"')
+    .trim();
+}
+
+function indentMarkdownBlock(content: string): string {
+  if (!content) return '\t';
+
+  return content
+    .split('\n')
+    .map((line) => (line.trim() ? `\t${line}` : ''))
+    .join('\n');
+}

packages/editor-ext/src/lib/tabs/index.ts

@@ -0,0 +1,8 @@
+export { Tabs } from "./tabs";
+export { Tab } from "./tab";
+export { TabLabel } from "./tab-label";
+export { TabPanel } from "./tab-panel";
+export type { TabsOptions } from "./tabs";
+export type { TabOptions } from "./tab";
+export type { TabLabelOptions } from "./tab-label";
+export type { TabPanelOptions } from "./tab-panel";

packages/editor-ext/src/lib/tabs/tab-label.ts

@@ -0,0 +1,42 @@
+import { mergeAttributes, Node } from "@tiptap/core";
+
+export interface TabLabelOptions {
+  HTMLAttributes: Record<string, unknown>;
+}
+
+export const TabLabel = Node.create<TabLabelOptions>({
+  name: "tabLabel",
+  content: "inline*",
+  defining: true,
+  selectable: false,
+
+  addOptions() {
+    return {
+      HTMLAttributes: {},
+    };
+  },
+
+  parseHTML() {
+    return [
+      {
+        tag: `div[data-type="${this.name}"]`,
+      },
+    ];
+  },
+
+  renderHTML({ HTMLAttributes }) {
+    return [
+      "div",
+      mergeAttributes(
+        {
+          "data-type": this.name,
+          "aria-hidden": "true",
+          class: "not-draggable-match"
+        },
+        this.options.HTMLAttributes,
+        HTMLAttributes,
+      ),
+      0,
+    ];
+  },
+});

packages/editor-ext/src/lib/tabs/tab-panel.ts

@@ -0,0 +1,37 @@
+import { mergeAttributes, Node } from "@tiptap/core";
+
+export interface TabPanelOptions {
+  HTMLAttributes: Record<string, unknown>;
+}
+
+export const TabPanel = Node.create<TabPanelOptions>({
+  name: "tabPanel",
+  content: "block+",
+  defining: true,
+
+  addOptions() {
+    return {
+      HTMLAttributes: {},
+    };
+  },
+
+  parseHTML() {
+    return [
+      {
+        tag: `div[data-type="${this.name}"]`,
+      },
+    ];
+  },
+
+  renderHTML({ HTMLAttributes }) {
+    return [
+      "div",
+      mergeAttributes(
+        { "data-type": this.name, role: "tabpanel", class: "not-draggable-match" },
+        this.options.HTMLAttributes,
+        HTMLAttributes,
+      ),
+      0,
+    ];
+  },
+});

packages/editor-ext/src/lib/tabs/tab.ts

@@ -0,0 +1,72 @@
+import { mergeAttributes, Node } from '@tiptap/core';
+import { generateNodeId } from "../utils";
+
+export interface TabOptions {
+  HTMLAttributes: Record<string, unknown>;
+}
+
+export const Tab = Node.create<TabOptions>({
+  name: 'tab',
+  content: 'tabLabel tabPanel',
+  defining: true,
+  isolating: true,
+
+  addOptions() {
+    return {
+      HTMLAttributes: {},
+    };
+  },
+
+  addAttributes() {
+    return {
+      id: {
+        default: '',
+        parseHTML: (element: HTMLElement) =>
+          element.getAttribute('data-tab-id') ?? generateNodeId(),
+        renderHTML: (attributes: { id?: string }) => ({
+          'data-tab-id': attributes.id ?? '',
+        }),
+      },
+      active: {
+        default: true,
+        parseHTML: (element: HTMLElement) => {
+          const rawValue = element.getAttribute('data-tab-active');
+          if (rawValue === null) {
+            return !element.hasAttribute('hidden');
+          }
+
+          return rawValue === 'true';
+        },
+        renderHTML: (attributes: { active?: boolean }) => {
+          const isActive = attributes.active !== false;
+
+          return {
+            'data-tab-active': isActive ? 'true' : 'false',
+            'aria-hidden': isActive ? 'false' : 'true',
+            ...(isActive ? {} : { hidden: 'hidden' }),
+          };
+        },
+      },
+    };
+  },
+
+  parseHTML() {
+    return [
+      {
+        tag: `div[data-type="${this.name}"]`,
+      },
+    ];
+  },
+
+  renderHTML({ HTMLAttributes }) {
+    return [
+      'div',
+      mergeAttributes(
+        { 'data-type': this.name },
+        this.options.HTMLAttributes,
+        HTMLAttributes,
+      ),
+      0,
+    ];
+  },
+});

packages/editor-ext/src/lib/tabs/tabs.ts

@@ -0,0 +1,463 @@
+import { InputRule, Node, Range, mergeAttributes } from '@tiptap/core';
+import { Fragment, type Node as PMNode } from '@tiptap/pm/model';
+import {
+  TextSelection,
+  type Transaction,
+  type EditorState,
+} from '@tiptap/pm/state';
+import { ReactNodeViewRenderer, type ReactNodeViewProps } from '@tiptap/react';
+import type { ComponentType } from 'react';
+import { generateNodeId } from '../utils';
+import { findParentNode } from '../table/utils';
+
+export interface TabsOptions {
+  HTMLAttributes: Record<string, unknown>;
+  view: ComponentType<ReactNodeViewProps<HTMLElement>> | null;
+}
+
+const TAB_INPUT_REGEX =
+  /^\s*===\s*["'“”‘’]((?:\\["\\]|[^\\"'“”‘’\n])+?)["'“”‘’]\s+$/;
+
+declare module '@tiptap/core' {
+  interface Commands<ReturnType> {
+    tabs: {
+      insertTabs: (tabName?: string, range?: Range) => ReturnType;
+      insertTab: (pos: 'right' | 'left') => ReturnType;
+      moveTab: (pos: 'right' | 'left') => ReturnType;
+      setActiveTab: (index: number, tabsPos: number) => ReturnType;
+      deleteTabs: () => ReturnType;
+      updateTabLabel: (
+        index: number,
+        label: string,
+        tabsPos: number,
+      ) => ReturnType;
+    };
+  }
+}
+
+export const Tabs = Node.create<TabsOptions>({
+  name: 'tabs',
+  group: 'block',
+  content: 'tab+',
+  defining: true,
+  isolating: true,
+
+  addOptions() {
+    return { HTMLAttributes: {}, view: null };
+  },
+
+  addAttributes() {
+    return {
+      activeTab: {
+        default: 0,
+        parseHTML: (element) =>
+          Number(element.getAttribute('data-active-tab')) || 0,
+        renderHTML: (attributes) => ({
+          'data-active-tab': clampIndex(attributes.activeTab),
+        }),
+      },
+    };
+  },
+
+  parseHTML() {
+    return [{ tag: `div[data-type="${this.name}"]` }];
+  },
+
+  renderHTML({ HTMLAttributes }) {
+    return [
+      'div',
+      mergeAttributes(
+        { 'data-type': this.name },
+        this.options.HTMLAttributes,
+        HTMLAttributes,
+      ),
+      0,
+    ];
+  },
+
+  addNodeView() {
+    if (!this.options.view) return undefined;
+    this.editor.isInitialized = true;
+    return ReactNodeViewRenderer(this.options.view);
+  },
+
+  addInputRules() {
+    return [
+      new InputRule({
+        find: TAB_INPUT_REGEX,
+        handler: ({ range, match }) => {
+          const rawLabel = typeof match[1] === 'string' ? match[1] : 'Tab 1';
+          const label = rawLabel.replace(/\\(["\\])/g, '$1').trim();
+
+          this.editor.commands.insertTabs(label, range);
+        },
+      }),
+    ];
+  },
+
+  addCommands() {
+    const createTab = (
+      schema: EditorState['schema'],
+      label: string,
+      active: boolean,
+    ) => {
+      const { tab, tabLabel, tabPanel, paragraph } = schema.nodes;
+      if (!tab || !tabLabel || !tabPanel || !paragraph) return null;
+
+      return tab.create({ id: generateNodeId(), active }, [
+        tabLabel.create(null, schema.text(label || ' ')),
+        tabPanel.create(null, paragraph.create()),
+      ]);
+    };
+
+    const getTabPos = (doc: PMNode, tabsPos: number, tabIndex: number) => {
+      const pos = doc.resolve(tabsPos + 1);
+      return pos.posAtIndex(tabIndex, pos.depth);
+    };
+
+    const applyActiveTabState = (
+      tr: Transaction,
+      tabsPos: number,
+      previousIndex: number,
+      nextIndex: number,
+    ) => {
+      const tabsNode = tr.doc.nodeAt(tabsPos);
+      if (tabsNode?.type.name !== 'tabs' || tabsNode.childCount <= 0) {
+        return null;
+      }
+
+      const prev = clampIndex(previousIndex, tabsNode.childCount);
+      const next = clampIndex(nextIndex, tabsNode.childCount);
+
+      tr.setNodeMarkup(tabsPos, undefined, {
+        ...tabsNode.attrs,
+        activeTab: next,
+      });
+
+      const prevTabPos = getTabPos(tr.doc, tabsPos, prev);
+      const nextTabPos = getTabPos(tr.doc, tabsPos, next);
+
+      if (prev !== next) {
+        const prevTabNode = tr.doc.nodeAt(prevTabPos);
+        if (prevTabNode) {
+          tr.setNodeMarkup(prevTabPos, undefined, {
+            ...prevTabNode.attrs,
+            active: false,
+          });
+        }
+      }
+
+      const nextTabNode = tr.doc.nodeAt(nextTabPos);
+      if (nextTabNode) {
+        tr.setNodeMarkup(nextTabPos, undefined, {
+          ...nextTabNode.attrs,
+          active: true,
+        });
+      }
+
+      return nextTabPos;
+    };
+
+    const selectTabPanel = (
+      tr: Transaction,
+      tabsPos: number,
+      tabPos: number,
+    ) => {
+      const tabsNode = tr.doc.nodeAt(tabsPos);
+      if (tabsNode?.type.name !== 'tabs' || tabsNode.childCount <= 0) {
+        return null;
+      }
+
+      const tabNode = tr.doc.nodeAt(tabPos);
+      const labelSize = tabNode?.child(0).nodeSize ?? 0;
+      const panelContentPos = tabPos + 1 + labelSize + 1;
+
+      tr.setSelection(TextSelection.near(tr.doc.resolve(panelContentPos), 1));
+    };
+
+    return {
+      insertTabs:
+        (tabName?: string, range?: Range) =>
+        ({ tr, state, dispatch }) => {
+          const firstTab = createTab(state.schema, tabName ?? 'Tab 1', true);
+          if (!firstTab) return false;
+
+          const tabsNode = this.type.create(
+            {
+              activeTab: 0,
+            },
+            Fragment.fromArray([firstTab]),
+          );
+
+          const insertionPos = tr.selection.from;
+
+          if (range) {
+            tr.replaceRangeWith(
+              range.from,
+              range.to,
+              tabsNode,
+            ).scrollIntoView();
+          } else {
+            tr.replaceSelectionWith(tabsNode).scrollIntoView();
+          }
+
+          const firstTabPos = getTabPos(tr.doc, insertionPos, 0);
+          const firstTabNode = tr.doc.nodeAt(firstTabPos);
+          if (!firstTabNode) return false;
+
+          if (!range) {
+            const labelSize = firstTabNode.child(0)?.nodeSize ?? 0;
+            const panelContentPos = firstTabPos + 2 + labelSize + 2;
+
+            tr.setSelection(
+              TextSelection.near(tr.doc.resolve(panelContentPos), 1),
+            );
+          }
+
+          if (dispatch) dispatch(tr);
+          return true;
+        },
+
+      insertTab:
+        (pos: 'left' | 'right') =>
+        ({ state, tr, dispatch }) => {
+          const { $from } = state.selection;
+          const tabs = findParentNode(
+            (node) => node.type.name === this.name,
+            $from,
+          );
+          if (!tabs || tabs.node.childCount <= 0) return false;
+
+          const currentTabIndex = clampIndex(
+            tabs.node.attrs.activeTab,
+            tabs.node.childCount,
+          );
+
+          const insertIndex =
+            pos === 'right' ? currentTabIndex + 1 : currentTabIndex;
+
+          const newTab = createTab(state.schema, 'Tab', false);
+          if (!newTab) return false;
+
+          const insertPos = getTabPos(state.doc, tabs.pos, insertIndex);
+          tr.insert(insertPos, newTab);
+
+          const insertedTabPos = getTabPos(tr.doc, tabs.pos, insertIndex);
+          tr.setNodeMarkup(insertedTabPos, undefined, {
+            ...newTab.attrs,
+            active: true,
+          });
+
+          const previousActiveIndex =
+            pos === 'left' ? currentTabIndex + 1 : currentTabIndex;
+
+          const activeTabPos = applyActiveTabState(
+            tr,
+            tabs.pos,
+            previousActiveIndex,
+            insertIndex,
+          );
+          if (activeTabPos == null) return false;
+
+          selectTabPanel(tr, tabs.pos, insertedTabPos);
+          if (dispatch) dispatch(tr);
+          return true;
+        },
+
+      moveTab:
+        (pos: 'left' | 'right') =>
+        ({ state, tr, dispatch }) => {
+          const { $from } = state.selection;
+          const tabs = findParentNode(
+            (node) => node.type.name === this.name,
+            $from,
+          );
+          if (!tabs || tabs.node.childCount <= 1) return false;
+
+          const currentTabIndex = clampIndex(
+            tabs.node.attrs.activeTab,
+            tabs.node.childCount,
+          );
+
+          const targetIndex =
+            pos === 'left' ? currentTabIndex - 1 : currentTabIndex + 1;
+
+          if (targetIndex < 0 || targetIndex >= tabs.node.childCount)
+            return false;
+
+          const currentTabPos = getTabPos(state.doc, tabs.pos, currentTabIndex);
+          const currentTabNode = state.doc.nodeAt(currentTabPos);
+          if (!currentTabNode) return false;
+
+          const mappedCurrentTabPos = tr.mapping.map(currentTabPos);
+          tr.delete(
+            mappedCurrentTabPos,
+            mappedCurrentTabPos + currentTabNode.nodeSize,
+          );
+
+          const insertPos = getTabPos(tr.doc, tabs.pos, targetIndex);
+          tr.insert(insertPos, currentTabNode);
+
+          const movedTabPos = applyActiveTabState(
+            tr,
+            tabs.pos,
+            targetIndex,
+            targetIndex,
+          );
+          selectTabPanel(tr, tabs.pos, movedTabPos);
+
+          if (dispatch) dispatch(tr.scrollIntoView());
+          return true;
+        },
+
+      setActiveTab:
+        (index, tabsPos) =>
+        ({ state, tr, dispatch }) => {
+          const tabsNode = state.doc.nodeAt(tabsPos);
+          if (tabsNode?.childCount <= 0) return false;
+
+          const nextIndex = clampIndex(index, tabsNode.childCount);
+          const prevIndex = clampIndex(
+            tabsNode.attrs.activeTab,
+            tabsNode.childCount,
+          );
+
+          const activeTabPos = applyActiveTabState(
+            tr,
+            tabsPos,
+            prevIndex,
+            nextIndex,
+          );
+          if (activeTabPos == null) return false;
+
+          selectTabPanel(tr, tabsPos, activeTabPos);
+          if (dispatch) dispatch(tr.scrollIntoView());
+          return true;
+        },
+
+      updateTabLabel:
+        (index, label, tabsPos) =>
+        ({ state, tr, dispatch }) => {
+          const tabsNode = state.doc.nodeAt(tabsPos);
+          if (!tabsNode) return false;
+
+          const labelIndex = clampIndex(index, tabsNode.childCount);
+          const $tabs = state.doc.resolve(tabsPos + 1);
+          const tabPos = $tabs.posAtIndex(labelIndex, $tabs.depth);
+
+          const labelNode = state.doc.nodeAt(tabPos + 1);
+          const labelContentPos = tabPos + 2;
+
+          tr.replaceWith(
+            labelContentPos,
+            labelContentPos + labelNode.content.size,
+            state.schema.text(label || ' '),
+          );
+
+          if (dispatch) dispatch(tr);
+          return true;
+        },
+
+      deleteTab:
+        () =>
+        ({ state, tr, dispatch }) => {
+          const { $from } = state.selection;
+          const tabs = findParentNode(
+            (node) => node.type.name === this.name,
+            $from,
+          );
+          if (!tabs) return false;
+
+          if (tabs.node.childCount < 2) {
+            this.editor.commands.deleteTabs();
+            return true;
+          }
+
+          const currentTabIndex = clampIndex(
+            tabs.node.attrs.activeTab,
+            tabs.node.childCount,
+          );
+
+          const currentTabPos = getTabPos(state.doc, tabs.pos, currentTabIndex);
+          const currentTabNode = state.doc.nodeAt(currentTabPos);
+          if (!currentTabNode) return false;
+
+          const nextTabIndex =
+            currentTabIndex < tabs.node.childCount - 1
+              ? currentTabIndex
+              : currentTabIndex - 1;
+
+          tr.delete(currentTabPos, currentTabPos + currentTabNode.nodeSize);
+
+          const activeTabPos = applyActiveTabState(
+            tr,
+            tabs.pos,
+            nextTabIndex,
+            nextTabIndex,
+          );
+          if (activeTabPos == null) return false;
+
+          selectTabPanel(tr, tabs.pos, activeTabPos);
+
+          if (dispatch) dispatch(tr);
+          return true;
+        },
+
+      deleteTabs:
+        () =>
+        ({ state, tr, dispatch }) => {
+          const { $from } = state.selection;
+          const tabs = findParentNode(
+            (node) => node.type.name === this.name,
+            $from,
+          );
+          if (tabs?.node.childCount <= 0) return false;
+
+          tr.delete(tabs.pos, tabs.pos + tabs.node.nodeSize);
+
+          if (dispatch) dispatch(tr);
+          return true;
+        },
+    };
+  },
+
+  addKeyboardShortcuts() {
+    return {
+      Enter: ({ editor }) => {
+        const { state } = editor;
+        const { $from, empty } = state.selection;
+
+        if (!empty) return false;
+        if ($from.parent.content.size > 0) return false;
+
+        const tabsNode = findParentNode(
+          (node) => node.type.name === this.name,
+          $from,
+        );
+
+        if (!tabsNode) return false;
+        return editor
+          .chain()
+          .command(({ tr, state }) => {
+            const posAfter = $from.after(tabsNode.depth);
+            tr.delete($from.before(), $from.after());
+
+            const targetPos = tr.mapping.map(posAfter);
+            const paragraph = state.schema.nodes.paragraph.create();
+
+            tr.insert(targetPos, paragraph);
+            tr.setSelection(TextSelection.create(tr.doc, targetPos + 1));
+            return true;
+          })
+          .scrollIntoView()
+          .run();
+      },
+    };
+  },
+});
+
+const clampIndex = (value: unknown, length = Number.MAX_SAFE_INTEGER) => {
+  const parsed = Number(value ?? 0);
+  if (!Number.isFinite(parsed) || length <= 0) return 0;
+  return Math.max(0, Math.min(Math.trunc(parsed), length - 1));
+};