styles.css

:root {
  --bslib-sidebar-main-bg: #f8f8f8;
}

.popover {
  --bs-popover-header-bg: #222;
  --bs-popover-header-color: #fff;
}

.popover .btn-close {
  filter: var(--bs-btn-close-white-filter);
}
shiny-chat-message table td,
shiny-chat-message table th {
  border: var(--bs-border-width) var(--bs-border-style) var(--bs-border-color);
  padding: 3px;
}

shiny-chat-message table td {
  font-family: var(--bs-font-monospace);
}

#show_title:empty, #show_query:empty {
  /* Prevent empty title/query blocks from taking any space */
  border: 0;
  padding: 0;
  margin-bottom: 0;
}

#show_title:empty, #show_query {
  /* We can't affect the flex parent's gap, so instead we use a negative margin
      to counteract it. In the case of #show_query, we don't even want the gap
      even when it's showing, as it results in too much space between the two. */
  margin-top: calc(-1 * var(--bslib-mb-spacer));
}