Type Alias ContextType<T>

ContextType: T extends {
    decode: (decodable: BytesLike, context?: infer Context) => unknown;
}
    ? Extract<IsAny<Context> extends true ? unknown : Context, Context>
    : unknown

The context a codec specifically requires when composed with other codecs. Legacy any is normalized to unknown, while Extract preserves that the normalized type is assignable to the codec's original context.