MAX_SITEMAP_INDEX_ENTRIES

const MAX_SITEMAP_INDEX_ENTRIES: 50000 = 50_000

A sitemap index may reference at most this many sitemaps, and may not reference another index — the protocol allows exactly one level. Unreachable at the default caps (50,000 shards of 50,000 URLs is 2.5 billion URLs) and defined anyway, because an unreachable case with no stated behaviour is how the next person finds out there wasn’t one.