zod4

SKILL.md

Zod 4 is a major release with significant performance improvements, reduced TypeScript compilation times, and a cleaner API. This skill covers migration from v3 and idiomatic Zod 4 usage.

| Record schemas | z.record(z.string()) | z.record(z.string(), z.string()) | | Strict objects | .strict() | z.strictObject({...}) | | Passthrough | .passthrough() | z.looseObject({...}) | | Error formatting | err.format() | z.treeifyError(err) | | Coerce input type | string | unknown |

In Zod 4, .default() short-circuits if input is undefined and returns the default directly (without parsing). Use .prefault() for the old behavior:

Comprehensive guide for Zod 4 schema validation library. This skill should be used when migrating from Zod 3, learning Zod 4 idioms, or building new validation schemas. Covers breaking changes, new features, and migration patterns. Source: kastalien-research/thoughtbox-dot-claude.

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