/**
 * Reading a line-delimited log without loading it.
 *
 * A session file on a working machine can be hundreds of megabytes -- the largest
 * on the machine this was written on is 204MB -- so nothing here reads a whole
 * file, and the read it does make does not block the process making it. The head
 * goes into a fixed buffer and the last partial line is dropped, because half a JSON object parses as nothing and a caller that did not
 * know it was truncated would report a clean pass over a file it barely opened.
 */
/** How much of one session file is read when a caller does not say. */
export declare const DEFAULT_MAX_BYTES: number;
export interface HeadResult {
    readonly lines: readonly string[];
    /** True when the file was longer than the budget. */
    readonly truncated: boolean;
}
/** Read up to `maxBytes` of a file and split it into whole lines. */
export declare function readJsonlHead(path: string, maxBytes?: number): Promise<HeadResult>;
/** Parse a line, or return null. A corrupt line is one lost record, not a crash. */
export declare function parseLine(line: string): Record<string, unknown> | null;
/** Flatten whatever a log put where text belongs into one string. */
export declare function textOf(value: unknown, limit?: number): string;
/** A string field, or ''. */
export declare function stringField(record: Record<string, unknown>, key: string): string;
/** A nested record, or null. */
export declare function recordField(record: Record<string, unknown>, key: string): Record<string, unknown> | null;
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