/** Represents any valid configuration value (primitives, arrays, or nested config objects). */
type ConfigValue = string | number | boolean | null | undefined | ConfigValue[] | ConfigObject;
interface ConfigObject {
    [key: string]: ConfigValue;
}
/** A signal object with a required name property; compatible with vega-typings InitSignal | NewSignal. */
interface NamedSignal {
    name: string;
    [key: string]: ConfigValue;
}
/** Represents top-level Vega configuration object; compatible with vega-typings Config. */
interface VegaConfig extends ConfigObject {
    signals?: NamedSignal[];
}
/** Internal type used to determine which properties should be recursively merged. Currently only supports legend layout and style blocks */
type RecurseStrategy = Record<string, unknown> | boolean | null;
/** Merges Vega config objects. Signals merged by name (source takes precedence),
 * legend.layout recursively merged, style fully recursive, others shallow.
 * Return type is compatible with vega-typings Config. */
export declare function mergeConfig(...configs: Partial<VegaConfig>[]): VegaConfig;
/** Writes config value to output with optional recursion, rejecting illegal keys that could be used to modify the prototype chain */
export declare function writeConfig(output: ConfigObject, key: string, value: ConfigValue, recurse?: RecurseStrategy): void;
export {};
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