zod

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Zod 4 schema validation best practices for type safety, parsing, and error handling. Use when defining schemas, validating string formats, calling safeParse, formatting Zod errors, or inferring input/output types. React Hook Form integration is covered by the react-hook-form skill.

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Sourcepymodel/react-frontend-skills

Added on2026-08-24

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npx skill4agent add pymodel/react-frontend-skills zod

SKILL.md Content

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Zod Best Practices

Comprehensive schema validation guide for Zod 4 in TypeScript applications. Contains 43 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


schema-
parse-
type-
error-
object-
compose-
refine-
perf-

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

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
```
error-avoid-throwing-in-refine
```
- Return false instead of throwing in refine

5. Object Schemas (MEDIUM-HIGH)

```
object-strict-vs-strip
```
- Choose an explicit unknown-key policy
```
object-partial-for-updates
```
- Use partial() for update schemas
```
object-pick-omit
```
- Use pick() and omit() for schema variants
```
object-extend-for-composition
```
- Use extend() for adding fields
```
object-optional-vs-nullable
```
- Distinguish optional() from nullable()
```
object-discriminated-unions
```
- Use discriminated unions for type narrowing

6. Schema Composition (MEDIUM)

```
compose-shared-schemas
```
- Extract shared schemas into reusable modules
```
compose-intersection
```
- Use intersection() for type combinations
```
compose-lazy-recursive
```
- Use z.lazy() for recursive schemas
```
compose-preprocess
```
- Use preprocess() for data normalization
```
compose-pipe
```
- Use pipe() for multi-stage validation

7. Refinements & Transforms (MEDIUM)

```
refine-vs-superrefine
```
- Choose refine() vs superRefine() correctly
```
refine-transform-coerce
```
- Distinguish transform() from refine() and coerce()
```
refine-add-path
```
- Add path to refinement errors
```
refine-defaults
```
- Use default() for optional fields with defaults
```
refine-catch
```
- Use catch() for fault-tolerant parsing

8. Performance & Bundle (LOW-MEDIUM)

```
perf-cache-schemas
```
- Cache schema instances
```
perf-zod-mini
```
- Use Zod Mini for bundle-sensitive applications
```
perf-avoid-dynamic-creation
```
- Avoid dynamic schema creation in hot paths
```
perf-lazy-loading
```
- Lazy load large schemas
```
perf-arrays
```
- Optimize large array validation

How to Use

Read individual reference files for detailed explanations and code examples:

Section definitions - Category structure and impact levels
Individual rules:
```
references/{prefix}-{slug}.md
```

Full Compiled Document

For the complete guide with all rules expanded:

AGENTS.md

Related Skills

For React Hook Form integration, see
```
react-hook-form
```
skill

zod