const viewport = document.querySelector('aparte-chat-viewport');
viewport.appendMessage({
id: 'preview',
role: 'assistant',
timestamp: Date.now(),
segments: [
// No `collapsed` key, so it renders CLOSED — see the field's own note below.
{
id: 's1',
type: 'thinking',
label: 'Reasoning',
content: 'The question is about transports, so name the two and say where the key lives.',
},
],
});