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effect-schema-v4

Migrate Effect TypeScript Schema code from v3 to v4 patterns.

22|1|Updated Apr 14, 2026
Search Tags:#typescript#schema migration#effect#type-safe decoding#api renames#codec validation#v4 changes
One-click install
npx skills add https://github.com/mpsuesser/pi-effect-harness --skill effect-schema-v4
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: effect-schema-v4
Source: https://github.com/mpsuesser/pi-effect-harness/tree/main/harnesses/effect/skills/effect-schema-v4
Command: npx skills add https://github.com/mpsuesser/pi-effect-harness --skill effect-schema-v4

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Effect Schema v4 API changes make it easy to accidentally keep v3 patterns (renamed functions, changed signatures, and removed modules), leading to broken codecs and confusing runtime/typing errors during migrations.

Core Features & Use Cases

  • Authoritative v4 migration guidance: Provides a migration reference for key v4 Schema API renames and behavioral changes from v3.
  • Concrete change tables & patterns: Covers function/constructor renames, variadic-to-array signature shifts, filter-to-check migration, and transform API redesigns.
  • Migration cheat-sheets for common pitfalls: Highlights removed APIs (like Schema.Data), optional-key semantics, and recommended replacements.

Quick Start

Use the effect-schema-v4 skill to look up the correct v4 Schema API name and signature before writing or refactoring your migration from v3 Schema code.

Frequently Asked Questions about effect-schema-v4

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I migrate Effect Schema from v3 to v4?▼

To migrate Effect Schema from v3 to v4, use this skill to look up the correct v4 API names and signatures before refactoring, preventing broken codecs and typing errors.

Why does my TypeScript codec validation break after upgrading to Effect Schema v4?▼

Codec validation breaks after upgrading to Effect Schema v4 because of renamed functions, changed variadic-to-array signatures, and removed modules that require updating your v3 patterns.

What changed in the Effect Schema v4 filter and transform APIs?▼

Effect Schema v4 replaced the filter API with check and redesigned the transform APIs, requiring you to map v3 patterns to the new signatures to maintain type-safe decoding.

Does Effect Schema v4 still support the Schema.Data module?▼

No, Effect Schema v4 removed the Schema.Data module, requiring you to use the recommended replacement patterns documented in the migration reference to fix resulting runtime errors.

How do I fix optional-key semantics when writing new Effect Schema v4 definitions?▼

To fix optional-key semantics in Effect Schema v4, reference the migration cheat-sheets to understand the updated behavior and apply the correct v4 constructor signatures.

What is the best way to debug type-safe decoding errors during an Effect Schema v4 migration?▼

The best way to debug type-safe decoding errors during an Effect Schema v4 migration is to cross-reference your code against the v3-to-v4 rename tables and authoritative source files.

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