Migrate Zod 3 schemas to Zod 4 and produce a migration report.
npx skills add https://github.com/klh/speedy-claude --skill zod4-klh
Please help me install this Agent Skill. Skill: zod4 Source: https://github.com/klh/speedy-claude/tree/main/skills/zod4 Command: npx skills add https://github.com/klh/speedy-claude --skill zod4-klh
Migration and compatibility gaps when upgrading from Zod 3 to Zod 4 cause TypeScript type errors, runtime validation regressions, and confusing API differences that break validation logic across a codebase. This guide consolidates breaking changes, migration patterns, and troubleshooting steps to reduce manual edits and test failures during the upgrade.
Convert all single-argument z.record calls to the two-argument form, replace .strict() and .passthrough() with z.strictObject and z.looseObject respectively, update error handling to use z.treeifyError, run the zod-v3-to-v4 codemod where helpful, and execute the test suite to validate changes.
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To migrate Zod 3 schemas to Zod 4, update incompatible validation patterns by converting single-argument z.record calls to accept key and value schemas, replacing removed .strict() and .passthrough() with z.strictObject and z.looseObject, and updating error handling using z.treeifyError.
The z.record signature changed in Zod 4, requiring both a key schema and a value schema as arguments. You must update all single-argument z.record calls to the new two-argument form to resolve TypeScript type errors and runtime validation regressions.
Zod 4 schema migration requires TypeScript 4.5 or higher compatibility. Ensure your TypeScript codebase meets this prerequisite before updating validation patterns, running the zod-v3-to-v4 codemod, or executing your test suite to verify runtime behavior.
In Zod 4, replace the removed .strict() and .passthrough() object methods with z.strictObject and z.looseObject respectively. This maintains your desired object shape strictness and prevents validation regressions when upgrading your TypeScript codebase.
Update Zod 4 error handling by replacing deprecated error formatting methods with z.treeifyError or prefault where needed. This resolves confusing API differences and ensures your runtime validation errors are correctly structured after the migration.
After migrating to Zod 4, adopt new features like z.file, z.templateLiteral, .meta, and z.globalRegistry to enhance schemas. You can also use the lighter zod/mini import for bundle-size improvements in your TypeScript application.
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