import { type UserConfig } from 'vite';
/** Env var prefix consumed at config time. */
export declare const ENV_PREFIX = "LIT_PLUGIN";
/** Parse a boolean-ish env string; `undefined` when unset/unrecognized. */
export declare const envBool: (v: string | undefined) => boolean | undefined;
/** Parse a numeric env string; `undefined` when unset/non-numeric. */
export declare const envNum: (v: string | undefined) => number | undefined;
/**
 * Parse a string against a closed set of values; `undefined` (with a warning)
 * when set to something outside it, so a typo falls back to the default
 * instead of silently disabling a feature.
 */
export declare const envEnum: <T extends string>(v: string | undefined, allowed: readonly T[], source: string) => T | undefined;
/**
 * The `LIT_PLUGIN_*` env for a `config` hook: `.env*` files from the env dir
 * (root by default) merged with matching `process.env` keys. Explicit options
 * still win; resolving them is the caller's job.
 */
export declare const loadPluginEnv: (viteConfig: UserConfig, mode: string) => Record<string, string>;
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