[nd 6/5] Back NotebookDocument cell text with Loro CRDT

frontend/src/core/codemirror/cells/extensions.ts

@@ -317,6 +317,16 @@ function cellKeymaps({
 function cellCodeEditing(hotkeys: HotkeyProvider): Extension[] {
   const onChangePlugin = EditorView.updateListener.of((update) => {
     if (update.docChanged) {
+      // Skip changes that came from Loro sync (RTC) — these are
+      // already reflected in the shared LoroDoc and don't need to
+      // round-trip through the transaction middleware.
+      const isLoroSync = update.transactions.some(
+        (tr) => tr.annotation(loroSyncAnnotation) != null,
+      );
+      if (isLoroSync) {
+        return;
+      }
+
       // Check if the doc update was a formatting change
       // e.g. changing from python to markdown
       const isFormattingChange = update.transactions.some((tr) =>

marimo/_notebook/__init__.py

@@ -0,0 +1,30 @@
+# Copyright 2026 Marimo. All rights reserved.
+"""Notebook document model — canonical representation of notebook structure."""
+
+from marimo._messaging.notebook.changes import (
+    CreateCell,
+    DeleteCell,
+    DocumentChange,
+    MoveCell,
+    ReorderCells,
+    SetCode,
+    SetConfig,
+    SetName,
+    Transaction,
+)
+from marimo._notebook.document import CellMeta, NotebookCell, NotebookDocument
+
+__all__ = [
+    "CellMeta",
+    "CreateCell",
+    "DeleteCell",
+    "DocumentChange",
+    "MoveCell",
+    "NotebookCell",
+    "NotebookDocument",
+    "ReorderCells",
+    "SetCode",
+    "SetConfig",
+    "SetName",
+    "Transaction",
+]

marimo/_notebook/_loro.py

@@ -0,0 +1,27 @@
+# Copyright 2026 Marimo. All rights reserved.
+"""Typed wrappers for ``loro`` APIs with incomplete stubs.
+
+The ``loro`` stubs omit return types on ``__new__`` and the
+``ValueOrContainer`` union lacks a typed ``.container`` accessor.
+These helpers isolate the ``type: ignore`` comments so the rest of
+the codebase stays clean.
+"""
+
+from __future__ import annotations
+
+from loro import LoroDoc, LoroText, ValueOrContainer
+
+
+def create_doc() -> LoroDoc:
+    return LoroDoc()  # type: ignore[no-untyped-call]
+
+
+def create_text() -> LoroText:
+    return LoroText()  # type: ignore[no-untyped-call]
+
+
+def unwrap_text(val: ValueOrContainer) -> LoroText:
+    """Extract a ``LoroText`` from a ``ValueOrContainer``."""
+    container = val.container  # type: ignore[union-attr,attr-defined]
+    assert isinstance(container, LoroText)
+    return container