# Caching

Fragment-caching Poetry safely: the version-keyed cache recipe, and why unkeyed fragments go silently stale across component upgrades.

Rails template digests cannot see Poetry - helpers are never discovered as dependencies and gem templates resolve outside the host's view paths - so an unkeyed cached fragment silently serves stale UI across component upgrades. The recipe: version-keyed cache keys (`cache [@post, Poetry::Ui::VERSION]`; `Poetry::Charts::VERSION` for charts) so each upgrade misses once. Components inside a cache block take `key:` or `id:` so replayed HTML never collides or defeats morph pairing; `poetry:check` warns (`stable-identity/cache`) and `poetry_id_integrity_script` audits the composed page. Copy-ins add `Template Dependency` comments; keep CSRF-bearing form tags outside cached fragments.