CJK and other IME users confirm a candidate from the input-method popup by pressing Enter. The chat composer and the in-place message editor each bind a keydown handler that treats Enter (without Shift) as "submit", but they did not exclude the composition state. Pressing Enter to accept an IME candidate therefore sent the half-composed text (e.g. a stray "ce's") instead of just confirming the candidate.
These textareas intentionally hijack Enter to submit (Enter sends, Shift+Enter inserts a newline), which bypasses the browser's native form submission and the IME guard that comes with it, so the guard has to be re-added explicitly.
Add '&& !e.isComposing' to the three Enter-to-submit handlers: static/app.js (the main composer's button-submit path and its send/new-chat path) and static/js/chat.js (the editor for an already-sent message). Normal Enter (isComposing false) still submits; Shift+Enter still inserts a newline.
Tested: node --check on both files; manually verified with a Chinese IME that pressing Enter to pick a candidate no longer sends, and a message is sent only after composition ends.
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