/**
 * Messages sentinel for injecting conversation history into prompts
 */
export declare const MESSAGES_SYMBOL: unique symbol;
export interface HistoryMessage {
    role: 'user' | 'assistant';
    content: string;
}
export interface MessagesSentinel {
    readonly [MESSAGES_SYMBOL]: true;
    readonly messages: HistoryMessage[];
}
export declare function createMessagesSentinel(messages: HistoryMessage[]): MessagesSentinel;
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