[codex] fix mobile composer Enter behavior

apps/web/src/components/chat/ChatComposer.tsx

@@ -41,6 +41,7 @@ import {
   detectComposerTrigger,
   expandCollapsedComposerCursor,
   replaceTextRange,
+  shouldSubmitComposerOnEnter,
 } from "../../composer-logic";
 import { deriveComposerSendState, readFileAsDataUrl } from "../ChatView.logic";
 import {
@@ -1750,7 +1751,10 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
         return true;
       }
     }
-    if (key === "Enter" && !event.shiftKey) {
+    if (
+      key === "Enter" &&
+      shouldSubmitComposerOnEnter({ isMobileViewport, shiftKey: event.shiftKey })
+    ) {
       submitComposer();
       return true;
     }

apps/web/src/composer-logic.test.ts

@@ -8,9 +8,24 @@ import {
   isCollapsedCursorAdjacentToInlineToken,
   parseStandaloneComposerSlashCommand,
   replaceTextRange,
+  shouldSubmitComposerOnEnter,
 } from "./composer-logic";
 import { INLINE_TERMINAL_CONTEXT_PLACEHOLDER } from "./lib/terminalContext";
 
+describe("shouldSubmitComposerOnEnter", () => {
+  it("submits plain Enter on desktop", () => {
+    expect(shouldSubmitComposerOnEnter({ isMobileViewport: false, shiftKey: false })).toBe(true);
+  });
+
+  it("inserts a newline for plain Enter on mobile", () => {
+    expect(shouldSubmitComposerOnEnter({ isMobileViewport: true, shiftKey: false })).toBe(false);
+  });
+
+  it("inserts a newline for Shift+Enter", () => {
+    expect(shouldSubmitComposerOnEnter({ isMobileViewport: false, shiftKey: true })).toBe(false);
+  });
+});
+
 describe("detectComposerTrigger", () => {
   it("detects @path trigger at cursor", () => {
     const text = "Please check @src/com";

apps/web/src/composer-logic.ts

@@ -11,6 +11,13 @@ export interface ComposerTrigger {
   rangeEnd: number;
 }
 
+export function shouldSubmitComposerOnEnter(input: {
+  isMobileViewport: boolean;
+  shiftKey: boolean;
+}): boolean {
+  return !input.isMobileViewport && !input.shiftKey;
+}
+
 const isInlineTokenSegment = (
   segment:
     | { type: "text"; text: string }