WeakMap-keyed memoization (createAsyncManifestMemo / createManifestMemo) scoped to an SSR manifest object, so cached middleware/actions/loggers are invalidated when the manifest is replaced (HMR/restarts). A clean, extractable 'cache scoped to object identity' primitive that solves stale-state bugs in long-lived servers.

AsyncLocalStorage-based render scope that collects per-render metadata (content entry keys, static image transforms) without leaking between concurrent requests or builds, with a noop fallback for edge runtimes lacking AsyncLocalStorage. A textbook, extractable pattern for request-scoped state in server frameworks.

AstroCookies implements a typed cookie jar over the Request/Response header cycle: parsing incoming Cookie headers, set/merge/delete with proper expiration semantics, and serializing back to Set-Cookie. Self-contained and portable to any server-side TypeScript HTTP project.

Platform-neutral CDN caching utilities: builds stale-while-revalidate Cache-Control directives, ETag/If-None-Match conditional headers, cache tags, and invalidation tag collection. Shared by Vercel/Netlify/Cloudflare providers and directly reusable in any edge or SSR project needing consistent HTTP cache semantics.

Runtime CSP header builder that partitions directives by kind (static vs per-request hash additions), deduplicates directive values including src/hash special cases, and injects script/style hashes discovered during render. Solves the classic 'CSP with dynamic inline scripts' problem and is extractable as a general CSP construction utility.

Compiles route patterns ([id], [...rest], literal segments) into path-to-regexp-compatible regexes with parameter extraction, supporting case-sensitivity rules and custom segment encoders. A standalone, well-tested route-matching primitive that any web framework or router library could reuse.