The form-submit handler in chat.html was setting
``textarea.disabled = true`` synchronously before the browser actually
serialized the form. Disabled form fields are excluded from
submission, so the request body contained ``prose=""`` even when the
user had typed text — which the server (correctly) rejected with the
new empty-prose 400. Net effect: typing "hello" + Send gave a "prose
cannot be empty" error.
Switched to ``readOnly``: same UX (user can't edit while streaming)
but the field IS submitted. The unlock path now also clears the
textarea and refocuses for the next turn.
Joseph Doherty
f0742dd4f9