Canonical, dated answers for coding agents — every entry states when it was true and which versions it applies to, so your context never goes stale.
Zod 4 has been stable since 4.0.0 (2025-07-09); current is 4.6.5 (2026-09-13). Use top-level formats (z.email()), the `error` param, z.treeifyError, two-arg z.record. 4.5 added z.compile() and stricter validation (datetime seconds, code-point lengths); 4.6 added .validate() and lazy error maps.