export type SessionTraceSignals = {
    turnCount: number;
    distinctToolNames: string[];
    toolCallEntries: Array<{
        name: string;
        ok?: boolean;
        errorText?: string;
    }>;
    hadErrors: boolean;
};
/**
 * Read the last MAX_TAIL_BYTES of the session log and extract signals.
 * Returns zeros / empty arrays if the log is missing or unreadable.
 */
export declare function readSessionTraceSignals(params: {
    agentId?: string;
    sessionId: string;
}): Promise<SessionTraceSignals>;