Headers-only mode

Caching never needs credentials; purging does. A CDN driver without its API credentials runs in headers-only mode:

it still emits every cache header (TTL, tags, ETag) and the X-Inertia-Static-Cache header;
pages expire by revalidate + stale-while-revalidate only;
StaticCache::purge*() and HasStaticTags queue nothing (a notice is logged);
php artisan inertia-static:purge refuses with a clear message, and inertia-static:doctor reports the mode;
StaticCache::canPurge() returns false.

Add the credentials later and purges start working, with no code change.

ini

INERTIA_STATIC_CDN=cloudflare      # no CLOUDFLARE_* variables = headers-only

The `X-Inertia-Static-Cache` header

Every response of a static route carries a stable header you can build CDN rules on:

Value	Meaning
`cacheable`	a shared cache may store this response
`bypass`	never store it (leak, `Authorization`, 5xx, SSR down, partial reload…)
(absent)	not a static route

The name is configurable (INERTIA_STATIC_CACHE_HEADER; empty disables it).

Each CDN page shows how to store only responses marked cacheable: Cloudflare, Fastly, Bunny, CloudFront, Varnish, nginx.