import { z } from 'zod';
/**
 * Env vars that are set as the strings `"true"` or `"false"`, parsed to booleans.
 * Any other value fails validation.
 */
export declare function envBooleanStringOptional(): z.ZodEffects<z.ZodOptional<z.ZodEnum<["true", "false"]>>, boolean | undefined, "true" | "false" | undefined>;
export declare function envBooleanStringDefaultFalse(): z.ZodEffects<z.ZodDefault<z.ZodEnum<["true", "false"]>>, boolean, "true" | "false" | undefined>;
/**
 * Like {@link envBooleanStringOptional}, but also accepts `"1"` as true (common for `CI`).
 */
export declare function envCiBooleanOptional(): z.ZodEffects<z.ZodOptional<z.ZodUnion<[z.ZodLiteral<"true">, z.ZodLiteral<"false">, z.ZodLiteral<"1">]>>, boolean | undefined, "1" | "true" | "false" | undefined>;
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