native-monad/src/option/CLAUDE.md

Option conventions

• match() takes 2 callbacks: (onSome, onNone)
• filter() takes ONLY a predicate — no errorFactory (unlike Result)
• mapErr() and flatMapErr() do NOT exist on Option
• none() returns a frozen singleton
• Option.from() treats only null | undefined as None — 0, false, "" become Some
• flatMap callback must return Option<any>
• Async return type: OptionPromise<T> — never Promise<Option<T>>

See /native-monad-option skill for full API reference.