Valibot

The validation library — modular, tree-shakeable, functional composition via pipes. See the valibot-superforms skill for schema syntax.

Why was it chosen?

• ~1.4 KB vs Zod's ~13.5 KB, only bundling the validators used — keeps client bundles small.

Superforms integration

• Native Valibot adapter (sveltekit-superforms/adapters), automatic FormData coercion.
• Schema must be defined at module top-level for caching.

Known limitations

• No method chaining — functional composition instead (v.parse(schema, data), not schema.parse(data)).
• @valibot/to-json-schema does not support transform actions.

Related

• superforms.md - Form handling
• ../core/sveltekit.md - Server validation