Bug: Enter key used to confirm Japanese IME composition submits answer in Plan Mode

Version

Codex App: 260206.1448 (build 565)

Subscription

ChatGPT Plus

Model

GPT-5.3-Codex(Extra High)

Platform

macOS 26.2 (Build 25C56)

What happened

In Plan Mode, while answering a question in Japanese, pressing Enter to confirm an IME conversion candidate sends the answer immediately.

Steps to reproduce

1. Open Codex desktop app and enter Plan Mode.
2. Ask/receive a question that requires a typed response.
3. Type Japanese text with IME and trigger conversion candidates.
4. Press Enter to confirm a candidate.

Expected behavior

Enter during IME composition should only confirm composition, not submit the answer.
Submission should occur only when composition is finalized and the user explicitly submits.

Actual behavior

Candidate-confirmation Enter is interpreted as submit.

Frequency

Always