TL;DR — Replaces the outdated z.custom() documentation example (template string literal) with a Decimal class validation example, since z.templateLiteral() now covers that use case natively in Zod v4.

Key changes

• Replace z.custom() example with Decimal validation — swaps the ${number}px template literal example for a decimal.js Decimal.isDecimal check, better illustrating z.custom()'s role for third-party types.
• Add cross-references to preferred alternatives — the intro sentence now points readers to z.instanceof() for class instances and z.templateLiteral() for template literal types.

_{Summary ｜ 1 file ｜ 3 commits ｜ base: main ← fix-custom-docs-example}

The previous example used a ${number}px template literal pattern to demonstrate z.custom(). Since Zod v4 ships z.templateLiteral(), that example no longer represents a realistic use case for z.custom(). The new example validates Decimal instances from the decimal.js library — a common real-world scenario where no built-in schema exists.

Before: example showed z.custom<\${number}px`>(…)with a regex check — a pattern now handled byz.templateLiteral()<br/>**After:** example shows z.custom(…)withDecimal.isDecimal`, demonstrating validation of third-party library types

packages/docs/content/api.mdx

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Merged, thanks for chasing this down. I swapped the example to a decimal.js Decimal check on top — the File instanceof case overlaps with z.instanceof() and z.file(), while z.custom is best demonstrated on structural or third-party types where no built-in fits. Closes #5605.

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Landed in Zod 4.4