fix(frontend): Prevent message submission during IME composition (#6025)

frontend/__tests__/components/chat/chat-input.test.tsx

@@ -218,4 +218,30 @@ describe("ChatInput", () => {
     // Verify image paste was handled
     expect(onImagePaste).toHaveBeenCalledWith([file]);
   });
+
+  it("should not submit when Enter is pressed during IME composition", async () => {
+    const user = userEvent.setup();
+    render(<ChatInput onSubmit={onSubmitMock} />);
+    const textarea = screen.getByRole("textbox");
+
+    await user.type(textarea, "こんにちは");
+
+    // Simulate Enter during IME composition
+    fireEvent.keyDown(textarea, {
+      key: "Enter",
+      isComposing: true,
+      nativeEvent: { isComposing: true },
+    });
+
+    expect(onSubmitMock).not.toHaveBeenCalled();
+
+    // Simulate normal Enter after composition is done
+    fireEvent.keyDown(textarea, {
+      key: "Enter",
+      isComposing: false,
+      nativeEvent: { isComposing: false },
+    });
+
+    expect(onSubmitMock).toHaveBeenCalledWith("こんにちは");
+  });
 });

frontend/src/components/features/chat/chat-input.tsx

@@ -94,7 +94,12 @@ export function ChatInput({
   };
 
   const handleKeyPress = (event: React.KeyboardEvent<HTMLTextAreaElement>) => {
-    if (event.key === "Enter" && !event.shiftKey && !disabled) {
+    if (
+      event.key === "Enter" &&
+      !event.shiftKey &&
+      !disabled &&
+      !event.nativeEvent.isComposing
+    ) {
       event.preventDefault();
       handleSubmitMessage();
     }