/**
 * The size of the context a Claude Code session is carrying right now, read from
 * the tail of its transcript. See docs/DATA_SOURCES.md §2.12.
 *
 * Every turn re-sends the whole conversation, so the LAST real assistant turn's
 * input side -- fresh input plus cache reads plus cache writes -- is how many
 * tokens the next message will re-read. This is not a usage total and is never
 * stored: it is a gauge of the moment, which is why it reads the file directly
 * and neither syncs nor touches the database.
 */
/** Tail window the first read covers; each retry multiplies it by GROWTH. */
export declare const INITIAL_WINDOW_BYTES: number;
/**
 * The context size in tokens, or `null` when it cannot be known.
 *
 * Unknown is a real answer, not a failure, and is never replaced with an older
 * number:
 *  - a `compact_boundary` line AFTER the last assistant usage means the context
 *    was just compacted and no turn has measured the new one. The last usage
 *    still describes the PRE-compact context (seen live: 458k shown when the real
 *    context was ~73k), so it must not be reported;
 *  - an unreadable, missing or empty transcript, or one with no usable turn yet.
 *
 * Never throws: it runs inside a status line and a prompt hook, and neither may
 * fail on a transcript it cannot read.
 */
export declare function readContextSize(transcriptPath: string, options?: {
    initialWindowBytes?: number;
}): number | null;