.scroll-to-bottom-btn {
  position: absolute;
  bottom: calc(var(--toolbar-height, 78px) + var(--composer-height, 0px) + 16px + env(safe-area-inset-bottom));
  right: 16px;
  z-index: 38;
  width: 44px;
  height: 44px;
  margin: 0;
  padding: 0;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border-subtle);
  border-radius: 50%;
  color: var(--text-primary);
  background: var(--surface);
  box-shadow: 0 4px 14px color-mix(in srgb, var(--background) 40%, transparent), 0 2px 6px rgba(0, 0, 0, 0.12);
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  opacity: 0;
  pointer-events: none;
  transform: translateY(8px);
  transition: opacity 0.18s ease, transform 0.18s ease, background-color 0.16s ease;
}

.scroll-to-bottom-btn__icon { display: inline-flex; }
.scroll-to-bottom-btn__icon svg { width: 22px; height: 22px; stroke-width: 2.2; }

.scroll-to-bottom-btn.is-visible {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}

.scroll-to-bottom-btn:hover { background: var(--surface-selected); }
.scroll-to-bottom-btn:active { transform: scale(0.95); }
.scroll-to-bottom-btn:focus-visible { outline: 2px solid var(--focus-ring); outline-offset: 2px; }

.app-shell--scroll-nested.keyboard-open .scroll-to-bottom-btn {
  bottom: calc(var(--keyboard-offset, 0px) + var(--composer-height, 0px) + 16px);
}

@media (prefers-reduced-motion: reduce) {
  .scroll-to-bottom-btn { transition: none; transform: none; }
}