rxwei on Jev: Co-Designing SDKs and Models Unlocks a New Paradigm

rxwei · x · 2026-09-21

rxwei, a core developer of Swift and Apple's Foundation Models framework, called Jev a fantastic example of co-designing SDKs and models to unlock a new paradigm. He recalls designing the framework's Swift API two years ago: the @Generable API made type-safe structured responses the standard, using constrained decoding to eliminate structural hallucinations in tool call arguments and responses — especially important for small on-device models.

He suggests it would be fascinating for decision models to conform to the LanguageModel protocol and work with @Generable natively: Bools map to "noul", enums represent choices, and @Guide descriptions act as instructions — a Swift implementation only needs to handle a schema conversation, since the APIs are already there.

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