From 9791ff1170356c9313edea507b87629fe810f9a3 Mon Sep 17 00:00:00 2001
From: Tom Moor <tom@getoutline.com>
Date: Thu, 11 Jun 2026 09:04:38 -0400
Subject: [PATCH] fix: Prevent selecting word-joiner characters around
 multiplayer cursor (#12660)

* Possible fix for word-joiner characters copied on Chrome+Windows

* simplify
---
 app/editor/extensions/Multiplayer.ts      |  3 ++-
 shared/editor/components/Styles.ts        | 11 ++++++-----
 shared/editor/styles/EditorStyleHelper.ts |  8 ++++++++
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/app/editor/extensions/Multiplayer.ts b/app/editor/extensions/Multiplayer.ts
index 4aa2000bfe..8bfe608f0f 100644
--- a/app/editor/extensions/Multiplayer.ts
+++ b/app/editor/extensions/Multiplayer.ts
@@ -13,6 +13,7 @@ import {
 import * as Y from "yjs";
 import Extension from "@shared/editor/lib/Extension";
 import { isRemoteTransaction } from "@shared/editor/lib/multiplayer";
+import { EditorStyleHelper } from "@shared/editor/styles/EditorStyleHelper";
 import { Second } from "@shared/utils/time";
 
 type UserAwareness = {
@@ -107,7 +108,7 @@ export default class Multiplayer extends Extension<MultiplayerOptions> {
 
       return {
         style: `background-color: ${u.color}${opacity}`,
-        class: "ProseMirror-yjs-selection",
+        class: EditorStyleHelper.multiplayerSelection,
       };
     };
 
diff --git a/shared/editor/components/Styles.ts b/shared/editor/components/Styles.ts
index a199663ccd..16dfb5529a 100644
--- a/shared/editor/components/Styles.ts
+++ b/shared/editor/components/Styles.ts
@@ -596,7 +596,7 @@ width: 100%;
   padding: ${props.editorStyle?.padding ?? "initial"};
   margin: ${props.editorStyle?.margin ?? "initial"};
 
-  & > .ProseMirror-yjs-cursor {
+  & > .${EditorStyleHelper.multiplayerCursor} {
     display: none;
   }
 
@@ -670,11 +670,11 @@ width: 100%;
   h5 { font-size: var(--font-size-h5); }
   h6 { font-size: var(--font-size-h6); }
 
-  .ProseMirror-yjs-selection {
+  .${EditorStyleHelper.multiplayerSelection} {
     transition: background-color 500ms ease-in-out;
   }
 
-  .ProseMirror-yjs-cursor {
+  .${EditorStyleHelper.multiplayerCursor} {
     position: relative;
     margin-left: -1px;
     margin-right: -1px;
@@ -682,6 +682,7 @@ width: 100%;
     border-right: 1px solid black;
     height: 1em;
     word-break: normal;
+    user-select: none;
 
     &::after {
       content: "";
@@ -719,7 +720,7 @@ width: 100%;
   }
 }
 
-&.show-cursor-names .ProseMirror-yjs-cursor > div {
+&.show-cursor-names .${EditorStyleHelper.multiplayerCursor} > div {
   opacity: 1;
 }
 
@@ -998,7 +999,7 @@ img.ProseMirror-separator {
 
 .${EditorStyleHelper.headingPositionAnchor}:first-child,
 // Edge case where multiplayer cursor is between start of cell and heading
-.${EditorStyleHelper.headingPositionAnchor}:first-child + .ProseMirror-yjs-cursor,
+.${EditorStyleHelper.headingPositionAnchor}:first-child + .${EditorStyleHelper.multiplayerCursor},
 // Edge case where table grips are between start of cell and heading
 .${EditorStyleHelper.headingPositionAnchor}:first-child + [role=button] + [role=button] {
   & + h1,
diff --git a/shared/editor/styles/EditorStyleHelper.ts b/shared/editor/styles/EditorStyleHelper.ts
index a77f34e033..bbb5abf1c8 100644
--- a/shared/editor/styles/EditorStyleHelper.ts
+++ b/shared/editor/styles/EditorStyleHelper.ts
@@ -22,6 +22,14 @@ export class EditorStyleHelper {
 
   static readonly comment = "comment-marker";
 
+  // Multiplayer
+
+  /** Remote collaborator's cursor */
+  static readonly multiplayerCursor = "ProseMirror-yjs-cursor";
+
+  /** Remote collaborator's selection */
+  static readonly multiplayerSelection = "ProseMirror-yjs-selection";
+
   // Code
 
   static readonly codeBlock = "code-block";