devtools.fm: Developer Tools, Open Source, Software Development Fabian Hiller - Valibot, Standard Schema, Formisch
Feb 2, 2026
Fabian Hiller, creator of Valibot, Standard Schema, and Formish; software engineer and open-source maintainer. He tells the story behind Valibot and its modular, tiny-bundle design. He explains the Standard Schema effort to unify schema libraries and using schema metadata for AI. He also describes Formish’s framework-agnostic core and how it injects native reactivity.
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Thesis Turned Into An OSS Hit
- Fabian built Valibot as part of his bachelor's thesis and published it while writing the paper.
- The thesis combined research, implementation, and community feedback which accelerated adoption.
Design For Tree-Shaking Early
- Design libraries modularly or provide a compiler to reduce bundle size and allow tree-shaking.
- Focus early on clear contracts so building blocks remain replaceable and consistent.
Modularity Drives Small Bundles
- Valibot achieves tiny bundle size by using a modular architecture so you only import what you use.
- Modular design plus consistent implementation enables high gzip compression and small incremental schema cost.