From 7ff86a3bc75ab71127ce08f5a70bc95f605ad66d Mon Sep 17 00:00:00 2001
From: Serhii Dziupin <serkraser@gmail.com>
Date: Wed, 5 Aug 2026 13:44:36 +0300
Subject: [PATCH] fix(composer): restore Shift+Enter newline on iOS

CodeMirror defers Enter on iOS (and Chrome Android): the real keydown is
captured without running the keymaps and the keymaps then run against a
synthetic keydown that dispatchKey builds from the key name alone, with
no modifier keys. The composer's Shift+Enter thus arrived as a plain
Enter, and on devices where Enter sends (iPad Safari/PWA, where the
desktop layout applies) it submitted the message instead of inserting a
newline.

Record the real Enter keydown's shift state on the view's contentDOM and
restore it onto the deferred synthetic event before the caller's
onKeyDown policy runs, so Shift+Enter means newline again on every
runtime. Plain Enter behavior is untouched: on iOS it still follows the
same deferred path it used before this change.

Fixes #2558
---
 .../chat/composer/editor/ComposerEditor.tsx   | 47 ++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/packages/ui/src/components/chat/composer/editor/ComposerEditor.tsx b/packages/ui/src/components/chat/composer/editor/ComposerEditor.tsx
index f3715dd7..41a2825f 100644
--- a/packages/ui/src/components/chat/composer/editor/ComposerEditor.tsx
+++ b/packages/ui/src/components/chat/composer/editor/ComposerEditor.tsx
@@ -130,6 +130,16 @@ function insertedTextOf(transaction: { changes: { iterChanges: (fn: (fromA: numb
     return inserted;
 }
 
+/**
+ * True for keydown events CodeMirror re-dispatches after deferring the real
+ * one (iOS Enter/Backspace/Delete, Chrome Android Enter): `dispatchKey`
+ * stamps the replacement event with a `synthetic` expando. These events are
+ * built from the key name alone, so they carry no modifier keys.
+ */
+function isDeferredSyntheticEvent(event: KeyboardEvent): boolean {
+    return Boolean((event as unknown as { synthetic?: boolean }).synthetic);
+}
+
 /**
  * Compartments are configuration keys, not per-view state, so one set can serve
  * every editor. They live at module scope because a kept-alive view outlives
@@ -160,6 +170,14 @@ export const ComposerEditor = React.forwardRef<ComposerEditorHandle, ComposerEdi
         const hostRef = React.useRef<HTMLDivElement | null>(null);
         const viewRef = React.useRef<EditorView | null>(null);
 
+        // The real keydown's shift state for the LAST Enter that reached the
+        // editor. CodeMirror defers Enter on iOS (and Chrome Android) and
+        // re-dispatches it as a synthetic keydown built from the key name
+        // alone, dropping every modifier (see `trackRealEnterShift` and the
+        // `interceptKeys` handler below); this ref is what lets the deferred
+        // event still tell Shift+Enter from Enter.
+        const lastRealEnterShiftRef = React.useRef(false);
+
         // Callbacks reach the CodeMirror extensions through a ref: the view is
         // built once and must not be torn down when a handler identity changes,
         // which would drop focus mid-typing. When a view store is supplied the
@@ -200,7 +218,15 @@ export const ComposerEditor = React.forwardRef<ComposerEditorHandle, ComposerEdi
             }
 
             const interceptKeys: KeyBinding[] = [{
-                any: (_view, event) => handlersRef.current.onKeyDown?.(event) ?? false,
+                any: (_view, event) => {
+                    // A deferred Enter lost its modifiers in the re-dispatch;
+                    // give the caller's policy (Enter vs Shift+Enter) back the
+                    // shift state it saw on the real keydown.
+                    if (event.key === 'Enter' && isDeferredSyntheticEvent(event) && lastRealEnterShiftRef.current) {
+                        Object.defineProperty(event, 'shiftKey', { value: true });
+                    }
+                    return handlersRef.current.onKeyDown?.(event) ?? false;
+                },
             }];
 
             const view = new EditorView({
@@ -276,6 +302,25 @@ export const ComposerEditor = React.forwardRef<ComposerEditorHandle, ComposerEdi
             viewRef.current = view;
             if (store) store.view = view;
 
+            // CodeMirror defers Enter on iOS (and Chrome Android): the real
+            // keydown is captured without running the keymaps, the browser's
+            // native newline goes through, and the keymaps then run against a
+            // synthetic keydown `dispatchKey` builds from the key name alone —
+            // which has NO modifiers. Recording the real shift state here (a
+            // plain listener, registered after CodeMirror's own, so it runs
+            // after the deferral decision but before the deferred dispatch)
+            // lets the deferred Enter be re-presented with Shift+Enter intact
+            // instead of arriving as a plain Enter that "sends" where Enter
+            // sends. Without it, Shift+Enter on iOS/Android submits the
+            // message instead of inserting a newline. The listener lives on
+            // the kept-alive view's contentDOM, so it stays across mounts and
+            // keeps feeding the same ref the `interceptKeys` closure reads.
+            const trackRealEnterShift = (event: KeyboardEvent) => {
+                if (event.key !== 'Enter' || isDeferredSyntheticEvent(event)) return;
+                lastRealEnterShiftRef.current = event.shiftKey;
+            };
+            view.contentDOM.addEventListener('keydown', trackRealEnterShift);
+
             return () => {
                 viewRef.current = null;
                 // A stored view is detached, not destroyed: the store owns its