import type { GCMessage } from "./sdk-types.js";
/** Rough token estimate: 1 token ≈ 4 chars */
export declare function estimateTokens(text: string): number;
/** Estimate total tokens across a message array */
export declare function estimateMessageTokens(messages: GCMessage[]): number;
/** Check if messages are approaching context limit and need compaction */
export declare function needsCompaction(messages: GCMessage[], contextWindow?: number): {
    needed: boolean;
    tokenEstimate: number;
    ratio: number;
};
/** Truncate oversized tool results, keeping first and last portions */
export declare function truncateToolResults(messages: GCMessage[], maxCharsPerResult?: number): GCMessage[];
/**
 * Build a text representation of messages for summarization.
 * Strips deltas and system messages, keeps the substantive conversation.
 */
export declare function messagesToText(messages: GCMessage[]): string;
/**
 * Generate a compaction prompt that can be sent to the model to summarize
 * the conversation so far. The caller runs the actual query.
 */
export declare function buildCompactPrompt(messages: GCMessage[]): string;