A host that is already leaving installs nothing

Some hosts live for a moment on purpose. When the portal starts, it briefly builds a host for each node type it ships, only to learn what kind of content that type carries, and lets it go at once. The same happens when an assistant checks a piece of content against a type's schema.

Starting a host is a short list of steps that runs shortly after it is created — subscribe to its own node, install a helper or two, start a ticker. When such a moment-long host was let go before that list had run, the list ran anyway, on a host that was already on its way out. Every step then installed something that was dead on arrival, and one of them — creating a helper — was refused with a warning: Rejecting hosted hub creation … during disposal. On a typical start the warning appeared for most of those brief hosts; it meant nothing was wrong, and it was the one line that could turn a clean-teardown check red.

A host that has begun to leave now skips the rest of its start-up list. Nothing is installed on it, nothing is refused, and the teardown finishes exactly as before. Hosts that are staying start exactly as they always did.