Cache API

HTTPX has no in-memory HTTP cache subsystem. HTTP caching is handled where it is actually implemented:

• Static files: server.static(mount, dir) serves with ETags and honors If-None-Match conditional requests (304 Not Modified). Embedded assets carry content-hash ETags.
• Client downloads: .existing = .verifyExisting skips re-downloads of files already on disk, and .replaceIfChanged uses conditional headers.
• DNS: the client caches resolutions (dnsCache: .{ .enable, .ttlMs, .negativeTtlMs, .maxEntries } in ClientConfig).

See Static Files, Single File, and Client Basics.