/**
 * File-locked JSONL append for concurrent write safety.
 *
 * When multiple workers write to the same shared JSONL (orchestrator pattern),
 * this module ensures atomic appends via advisory file locking (flock).
 * Each write acquires an exclusive lock, appends the JSON line, and releases.
 *
 * Diagnostics: logs lock contention (wait > 100ms) and tracks write durations.
 */
/**
 * Append a JSON line to a JSONL file with process-level serialization.
 *
 * Uses an in-process queue (Promise chain) to serialize writes to the same file.
 * For multi-process safety (multiple gateway instances), the append is atomic
 * at the OS level for small writes (< PIPE_BUF, typically 4KB on Linux).
 *
 * @param filePath - Absolute path to the JSONL file
 * @param data - Object to serialize as a JSON line
 * @param writer - Optional label for diagnostic logging (e.g., "worker-1713000000")
 * @returns The serialized JSON line that was written
 */
export declare function lockedAppend(filePath: string, data: unknown, writer?: string): Promise<string>;
/**
 * Validate JSONL file integrity — check each line is parseable JSON.
 * Returns corrupted line numbers (1-indexed) and their raw content.
 */
export declare function validateJsonl(filePath: string): {
    valid: boolean;
    corrupted: Array<{
        line: number;
        raw: string;
    }>;
};
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