For shared caches, a valid s-maxage delta-seconds value overrides max-age/Expires and carries proxy-revalidate semantics; malformed or duplicate values are treated as unusable freshness information.

A valid s-maxage delta-seconds value is also required before using s-maxage to permit shared-cache reuse of authorized responses.

Sources: RFC 9111 §5.2.2.8, §5.2.2.10, §3.5.

Unsafe requests now invalidate stored responses for their target URI after a non-error response. Unknown extension methods are treated conservatively as unsafe because methods are only safe when defined as safe.

Non-error responses for this invalidation rule are 2xx or 3xx responses, so informational 1xx responses do not trigger invalidation.

Sources: RFC 9111 §4, §4.4; RFC 9110 §9.2.1.

The cache now recognizes all RFC 9111 status codes that are heuristically cacheable by default, including 308, 405, 414, and 501.

Responses with other final status codes can also be stored when explicit freshness information permits it, except for 206 and standalone 304 responses which this client does not store.

Non-default status codes only use heuristic freshness when the response is explicitly marked public.

Sources: RFC 9111 §3, §4.2.1, §4.2.2.

Cached responses now account for Date, Age, response delay, and resident time when computing current_age.

The generated Age header on cached responses is based on that current_age calculation instead of only the originally stored Age value.

Sources: RFC 9111 §4.2.3, §5.1.

Cached responses no longer store hop-by-hop fields named by the Connection header.

The cache continues to exclude the fixed connection-specific fields that must not be stored.

Sources: RFC 9111 §3.1; RFC 9110 §7.6.1.

A 304 response now freshens a cached response only when response validators match the stored response.

Client conditional requests pass through 304 responses instead of being replaced by cached 200 responses, and fresh cached responses can answer matching client conditionals with 304.

Sources: RFC 9111 §4.3.2, §4.3.4.

When a cached response is freshened by a matching 304 response, the stored metadata, headers, age information, and freshness lifetime are updated from the 304 response.

If the updated metadata changes Vary handling or makes the response no longer cacheable, the stored variant metadata is removed instead of being reused incorrectly.

Sources: RFC 9111 §4.1, §4.2.3, §4.3.4.

Request Cache-Control directives now affect cache lookup, revalidation, and storage decisions.

no-cache forces validation before reuse, no-store bypasses lookup and prevents storage, max-age limits the acceptable current age, and only-if-cached returns a gateway timeout on cache miss instead of contacting the origin.

Sources: RFC 9111 §5.2.1.1, §5.2.1.4, §5.2.1.5, §5.2.1.7.