/**
 * Per-WorkItem token usage and cost (#812).
 *
 * A WorkItem's `inputTokens` / `outputTokens` / `cost` describe what that one
 * task spent. The agent session's totals are cumulative across every task the
 * session ever ran, so copying them onto a WorkItem charged the whole history
 * to whichever item finished next (a morning briefing "cost" $576).
 *
 * The task's usage is the session's usage between the moment the item started
 * running and the moment it completed — the delta between the cumulative
 * figures at those two points.
 */
import type { WorkItem } from '../../types/v2/work-item.types.js';
/** Token usage and cost attributed to one WorkItem. */
export interface WorkItemUsage {
    /** Input tokens the session consumed while the item ran */
    inputTokens: number;
    /** Output tokens the session generated while the item ran */
    outputTokens: number;
    /** Cost in USD of that usage (internal; owners see tokens) */
    cost: number;
    /**
     * Tokens in the owner-facing unit (input incl. cached + output, see
     * `eventTokens`); 0 when the source does not report it
     */
    totalTokens: number;
    /** Of {@link totalTokens}, the cached input */
    cachedInputTokens: number;
}
/** The slice of TokenUsageService this helper needs (windowed session usage). */
export interface SessionUsageWindowSource {
    getSessionUsageSince(sessionName: string, since: Date, until?: Date): {
        inputTokens: number;
        outputTokens: number;
        cost: number;
        totalTokens?: number;
        cachedInputTokens?: number;
    };
}
/**
 * Compute the token usage and cost of one WorkItem: the session's usage from
 * when the item started running (`startedAt`, falling back to `createdAt` for
 * items completed without a claim) to when it completed (`completedAt`,
 * falling back to `now`).
 *
 * @param item - The WorkItem (only its timestamps are read)
 * @param sessionName - The agent session that ran it
 * @param source - Windowed usage source (TokenUsageService)
 * @param now - End of the window when the item has no `completedAt`
 * @returns The per-task usage, or null when the window is unusable
 */
export declare function computeWorkItemUsage(item: Pick<WorkItem, 'createdAt' | 'startedAt' | 'completedAt'>, sessionName: string, source: SessionUsageWindowSource, now?: Date): WorkItemUsage | null;
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