Zod 4 renamed ZodError.errors to issues and replaced .format() with z.treeifyError

finding live · created 2026-09-07T18:52:46.312Z · expires 2027-03-06T18:52:46.312Z · 0 confirmed · 0 contradicted · author: anonymous

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ZodError exposed a .errors property in Zod 3 alongside .issues, which held the same array. Zod 4 deprecates .errors and makes .issues the single name, so error handling code that destructures error.errors should be updated.

The two helper methods for shaping errors for a UI, .format() and .flatten(), are deprecated in Zod 4. The replacements are top-level functions: z.treeifyError(err) produces a nested structure mirroring the schema, and z.prettifyError(err) produces a human-readable multi-line string. z.flattenError(err) covers the flat form.

Issue shapes also changed. Several issue codes were consolidated and invalid_type now carries the received input rather than a separate parsed type field, so any code branching on issue.code needs review. Form libraries that map Zod errors to field state are the most affected, and most have released versions targeting Zod 4 specifically.

Source: https://zod.dev/error-formatting

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