import type { TurnResult } from '../types/channel.js';
import type { RunContext } from '../types/run-context.js';
export declare const TOKEN_USAGE_STATE_KEY = "__tokenUsage";
export declare const LAST_PROMPT_TOKENS_KEY = "__lastPromptTokens";
/**
 * Peak prompt size within the CURRENT user turn.
 *
 * A flow turn calls `driver.runAgentTurn` once per node, and each call builds a fresh usage
 * snapshot — so `LAST_PROMPT_TOKENS_KEY` alone records whichever node ran last. On a flow
 * turn that is typically a small extraction call, which is why a turn that sent 22,226
 * tokens reported a context of 2,166. Reset at turn open; maxed on every node.
 */
export declare const TURN_PEAK_PROMPT_TOKENS_KEY = "__turnPeakPromptTokens";
/** Called when a user turn opens, so the peak measures one turn and not the session. */
export declare function resetTurnPeakPromptTokens(state: Record<string, unknown>): void;
export declare function readTurnPeakPromptTokens(state: Record<string, unknown>): number | undefined;
export interface PersistedTokenUsage {
    inputTokens: number;
    outputTokens: number;
    totalTokens: number;
    cacheReadTokens?: number;
    cacheWriteTokens?: number;
}
/** Record real turn usage onto run state (survives across turns via persistence). */
export declare function persistTurnUsageFromTurn(ctx: Pick<RunContext, 'runState' | 'runStore'>, turn: Pick<TurnResult, 'usage'>): Promise<void>;
export declare function readLastPromptTokens(state: Record<string, unknown>): number | undefined;
/** The session-cumulative usage persisted on run state (or undefined before any turn). */
export declare function readCumulativeUsage(state: Record<string, unknown>): PersistedTokenUsage | undefined;
export interface TraceTurnUsage {
    /** Input tokens consumed by THIS turn (cumulative delta since the turn opened). */
    inputTokens?: number;
    /** Output tokens generated by THIS turn (cumulative delta since the turn opened). */
    outputTokens?: number;
    /** Context-window occupancy — the last prompt's token count (not a per-turn delta). */
    contextTokens?: number;
    /** Prompt-cache read tokens for THIS turn (delta). */
    cacheReadTokens?: number;
    /** Prompt-cache write tokens for THIS turn (delta). */
    cacheWriteTokens?: number;
}
/** Per-turn token usage for a trace's `done` event. `baseline` is the cumulative
 *  usage captured when the turn OPENED, so input/output are strictly this turn's
 *  consumption (correct for cost attribution — never the running session total).
 *  `contextTokens` is the current window occupancy, which is inherently a snapshot. */
export declare function computeTurnTraceUsage(baseline: PersistedTokenUsage | undefined, state: Record<string, unknown>): TraceTurnUsage;