/**
 * Backfills `turn.completed` events with model + token usage by tail-reading
 * the Claude Code transcript JSONL named in the hook payload's
 * `transcript_path`. The assistant's message text itself comes straight off
 * the Stop hook payload (`last_assistant_message`, see normalizer.ts) — it's
 * available synchronously and doesn't depend on the transcript file, which
 * may not exist on disk yet (or at all) at the moment Stop fires. This
 * module only ever *supplements* that with model/usage, and falls back to
 * its own transcript-derived text if the hook payload somehow didn't have
 * one.
 *
 * Transcripts can grow to hundreds of MB over a long session, so this only
 * ever reads the last ~2MB from the end of the file.
 */
import type { AnalyticsEvent } from "../../shared/types.js";
export interface TranscriptTurn {
    model: string | null;
    assistantText: string | null;
    usage: {
        inputTokens: number | null;
        outputTokens: number | null;
    } | null;
}
/**
 * Read the last `maxBytes` of a transcript JSONL file and return the most
 * recent assistant turn found in it, or `null` if the file is missing,
 * unreadable, or has no assistant turn in the tail window.
 */
export declare function readLastAssistantTurn(transcriptPath: string, maxBytes?: number): Promise<TranscriptTurn | null>;
/**
 * Enrich a `turn.completed` event's payload with transcript data (model,
 * usage, and a fallback assistantText). No-op for any other event type, or
 * when no transcript path is available, or when the transcript can't be
 * read (e.g. not written to disk yet) — none of that should ever clobber
 * the assistantText the Stop hook payload already supplied.
 */
export declare function enrichTurnCompleted(event: AnalyticsEvent, transcriptPath: string | undefined, maxBytes?: number): Promise<AnalyticsEvent>;
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