takahe/templates/activities/_boost.html

{% if post.pk in interactions.boost %}
    <a title="Unboost" class="active" hx-post="{{ post.urls.action_unboost }}" hx-swap="outerHTML">
        <i class="fa-solid fa-retweet"></i>
    </a>
{% else %}
    <a title="Boost" hx-post="{{ post.urls.action_boost }}" hx-swap="outerHTML">
        <i class="fa-solid fa-retweet"></i>
    </a>
{% endif %}