let text = '';
let stalled;

const resetStall = () => {
  clearTimeout(stalled);
  // A stream that simply stops emitting never "fails" on its own
  stalled = setTimeout(() => controller.abort(), 30_000);
};

for await (const event of stream) {
  resetStall();

  switch (event.type) {
    case 'content_block_delta':
      text += event.delta.text ?? '';    // APPEND, never assign
      break;
    case 'content_block_stop':
      render(text);                       // flush here, not per delta
      break;
    case 'error':
      // Text may already be on screen — say it is incomplete
      showPartialWarning(text, event.error);
      break;
  }
}
clearTimeout(stalled);