import { VoiceSessionState } from '../managers/StateManager';
/**
 * Format conversation history for system prompt injection
 *
 * Converts transcript array into a structured text block that can be
 * prepended to system instructions, giving the AI context about
 * previous conversation turns.
 *
 * @param transcripts - Array of conversation transcripts
 * @param options - Formatting options
 * @param options.maxTurns - Maximum number of turns to include (default: all)
 * @param options.includeTimestamps - Include timestamps in output (default: false)
 * @returns Formatted history string for system prompt
 *
 * @example
 * ```ts
 * const history = formatHistoryForPrompt(state.transcripts);
 * const instructions = `${history}\n\n${baseInstructions}`;
 * ```
 */
export declare function formatHistoryForPrompt(transcripts: VoiceSessionState['transcripts'], options?: {
    maxTurns?: number;
    includeTimestamps?: boolean;
}): string;
/**
 * Truncate conversation history to fit within token limits
 *
 * Estimates token count and removes oldest turns until within limit.
 * Uses rough heuristic: 1 token ≈ 4 characters.
 *
 * @param transcripts - Array of conversation transcripts
 * @param maxTokens - Maximum tokens to allow (default: 32000)
 * @returns Truncated transcript array
 *
 * @example
 * ```ts
 * const truncated = truncateHistory(state.transcripts, 32000);
 * ```
 */
export declare function truncateHistory(transcripts: VoiceSessionState['transcripts'], maxTokens?: number): VoiceSessionState['transcripts'];
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