Zod4

kastalien-research/thoughtbox-dot-claude

Zod 4 is a major breaking release with real performance wins and faster TypeScript compilation, but you'll need to update your code. The biggest gotchas are z.record() now requiring two arguments instead of one, strict objects moving from .strict() to z.strictObject(), and .default() behavior changing in ways that'll bite you if you're using transforms. This guide walks through the migration with a quick reference table, covers new features like z.file() and z.templateLiteral(), and includes find-replace patterns for the common breaks. If you're maintaining a Zod 3 codebase or starting fresh with v4, this gives you the specifics without having to dig through changelog noise.

skills.sh installs: 289
GitHub stars: 9
last updated: Aug 21, 2026

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Install

$ npx -y skills add kastalien-research/thoughtbox-dot-claude --skill zod4 --agent claude-code

Installs into .claude/skills of the current project.

Files

Zod 4 Expert Guide

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.

Quick Migration Checklist

Before diving deep, address these high-impact breaking changes:

Change	Zod 3	Zod 4
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`

Install Zod 4:

npm install zod@^4.0.0

For detailed breaking changes, see ./reference/breaking-changes.md.

Key Breaking Changes

1. z.record() Requires Two Arguments

// Zod 3 (BROKEN in v4)
z.record(z.string());

// Zod 4 (REQUIRED)
z.record(z.string(), z.string());

2. Strict/Loose Object Syntax

// Zod 3
z.object({ name: z.string() }).strict();
z.object({ name: z.string() }).passthrough();

SKILL.md on GitHub

Details

Repository: github.com/kastalien-research/thoughtbox-dot-claude
Categories: Documentation, Data Science & ML
First seen: Jun 3, 2026