/**
 * Token estimation utilities for compaction.
 *
 * Pure functions for estimating context tokens, message sizes, and compaction
 * token metrics.
 */
import type { AgentMessage } from "../../../agent-core/index.js";
import type { Usage } from "../../../ai/index.js";
import type { SessionEntry } from "../session-manager.js";
import type { CompactionPreparation, CompactionResult, CompactionSettings } from "./compaction.js";
export interface CompactionTokenSourceBucket {
    type: "role" | "tool" | "source";
    name: string;
    tokens: number;
}
/**
 * Calculate total context tokens from usage.
 * Uses the native totalTokens field when available, falls back to computing from components.
 */
export declare function calculateContextTokens(usage: Usage): number;
/**
 * Find the last non-aborted assistant message usage from session entries.
 */
export declare function getLastAssistantUsage(entries: SessionEntry[]): Usage | undefined;
export interface ContextUsageEstimate {
    tokens: number;
    usageTokens: number;
    trailingTokens: number;
    lastUsageIndex: number | null;
}
/**
 * Estimate context tokens from messages, using the last assistant usage when available.
 * If there are messages after the last usage, estimate their tokens with estimateTokens.
 */
export declare function estimateContextTokens(messages: AgentMessage[]): ContextUsageEstimate;
/**
 * Check if compaction should trigger based on context usage.
 */
export declare function shouldCompact(contextTokens: number, contextWindow: number, settings: CompactionSettings): boolean;
/**
 * Estimate token count for a message using chars/4 heuristic.
 * This is conservative (overestimates tokens).
 */
export declare function estimateTokens(message: AgentMessage): number;
export declare function estimateTextTokens(text: string): number;
export declare function estimateCompactionTokenMetrics(preparation: Pick<CompactionPreparation, "messagesToSummarize" | "turnPrefixMessages"> & Partial<Pick<CompactionPreparation, "compactionNumber">>, summary: string): Pick<CompactionResult, "tokensCompacted" | "tokensRemoved" | "summaryTokens" | "reductionPercent" | "compactionNumber" | "largestTokenSources">;
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