# zod

A set of 46 validation and type inference rules for Zod 4 in TypeScript projects. Helps agents write schemas, handle errors, and clean up deprecated syntax.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 476 installs · ★ 39
- Author: PyModel
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/PyModel/react-frontend-skills/tree/HEAD/skills/zod/SKILL.md
- Updated: 2026-10-21
- HTML: https://affpapa.org/en/nevibecode/skills/pymodel-zod

## What it does

This skill supplies coding assistants with 46 prioritized rules for Zod 4 in TypeScript applications. The guidelines are grouped into eight categories covering schema definitions, safe parsing, type inference with `z.infer`, error handling, and performance tuning with Zod Mini. You can inspect project code against these rules using the `detect` and `scan` commands from `@pymodel/react-frontend-skills`.

The guidelines rely strictly on Zod 4 conventions. Several rules depend on specific minor releases, such as bidirectional transforms with `z.codec()` in 4.1+, compiled schemas via `z.compile` in 4.5+, and the `validate()` helper in 4.6+. Running this against a Zod 3 codebase will cause syntax mismatches because older versions lack these methods. Each rule includes an explanation alongside bad and good code examples.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add PyModel/react-frontend-skills --skill zod -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/zod/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/zod/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add PyModel/react-frontend-skills --skill zod -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/zod/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add PyModel/react-frontend-skills --skill zod -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/zod/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install PyModel/react-frontend-skills zod
```

2. **Manually: put the files in place**
- File: `.github/skills/zod/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add PyModel/react-frontend-skills --skill zod -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/PyModel/react-frontend-skills --path skills/zod
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/zod/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add PyModel/react-frontend-skills --skill zod -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/PyModel/react-frontend-skills/tree/HEAD/skills/zod/SKILL.md

## When to use it
- enforce runtime validation on user input with `safeParse()`
- infer TypeScript types automatically without manual duplication using `z.infer`
- scan codebases for deprecated Zod syntax using the CLI scanner
- build recursive object schemas safely with `z.lazy()`
- optimize hot validation paths with compiled schemas via `z.compile`

## Example prompts
- Review the schema in `src/auth.ts` against Zod 4 best practices and switch from `parse()` to `safeParse()`.
- Run `npx -y @pymodel/react-frontend-skills scan --skill zod` and identify outdated schema patterns in this repo.
- Generate inferred types using `z.infer` and configure path-based error reporting for nested profile fields.

## Source text · SKILL.md · MIT

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BEGIN THIRD-PARTY FILE cce0beefac04ea33
```text
---
name: zod
description: Zod 4 schema validation and type inference.
---

# Zod Best Practices

Comprehensive schema validation guide for Zod 4 in TypeScript applications. Contains 46 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.

## When to Apply

Reference these guidelines when:
- Writing new Zod schemas
- Choosing between parse() and safeParse()
- Implementing type inference with z.infer
- Handling validation errors for user feedback
- Composing complex object schemas
- Using refinements and transforms
- Optimizing bundle size and validation performance
- Reviewing Zod code for best practices

## Rule Categories by Priority

| Priority | Category | Impact | Prefix |
|----------|----------|--------|--------|
| 1 | Schema Definition | CRITICAL | `schema-` |
| 2 | Parsing & Validation | CRITICAL | `parse-` |
| 3 | Type Inference | HIGH | `type-` |
| 4 | Error Handling | HIGH | `error-` |
| 5 | Object Schemas | MEDIUM-HIGH | `object-` |
| 6 | Schema Composition | MEDIUM | `compose-` |
| 7 | Refinements & Transforms | MEDIUM | `refine-` |
| 8 | Performance & Bundle | LOW-MEDIUM | `perf-` |

## Quick Reference

### 1. Schema Definition (CRITICAL)

- `schema-use-primitives-correctly` - Use correct primitive schemas for each type
- `schema-use-unknown-not-any` - Use z.unknown() instead of z.any() for type safety
- `schema-avoid-optional-abuse` - Avoid overusing optional fields
- `schema-string-validations` - Apply string validations at schema definition
- `schema-use-enums` - Use enums for fixed string values
- `schema-coercion-for-form-data` - Use coercion for form and query data

### 2. Parsing & Validation (CRITICAL)

- `parse-use-safeparse` - Use safeParse() for user input
- `parse-async-for-async-refinements` - Use parseAsync for async refinements
- `parse-handle-all-issues` - Handle all validation issues not just first
- `parse-validate-early` - Validate at system boundaries
- `parse-avoid-double-validation` - Avoid validating same data twice
- `parse-never-trust-json` - Never trust JSON.parse output
- `parse-validate-for-boolean-checks` - Use validate() for yes/no checks (Zod 4.6+)

### 3. Type Inference (HIGH)

- `type-use-z-infer` - Use z.infer instead of manual types
- `type-input-vs-output` - Distinguish z.input from z.infer for transforms
- `type-export-schemas-and-types` - Export both schemas and inferred types
- `type-branded-types` - Use branded types for domain safety
- `type-enable-strict-mode` - Enable TypeScript strict mode

### 4. Error Handling (HIGH)

- `error-custom-messages` - Provide custom error messages
- `error-use-flatten` - Use Zod 4 error formatting helpers
- `error-path-for-nested` - Use issue.path for nested error location
- `error-i18n` - Implement internationalized error messages
```
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