/**
 * Metrics Collector - Prometheus-compatible metrics for AgentProbe.
 *
 * Tracks test counts, durations, costs, and exposes a /metrics endpoint.
 */
export type MetricType = 'counter' | 'gauge' | 'histogram' | 'summary';
export interface MetricLabel {
    [key: string]: string;
}
interface MetricEntry {
    name: string;
    type: MetricType;
    help: string;
    values: Map<string, number>;
    observations?: Map<string, number[]>;
}
export declare class MetricsRegistry {
    private metrics;
    counter(name: string, help: string): Counter;
    gauge(name: string, help: string): Gauge;
    histogram(name: string, help: string, buckets?: number[]): Histogram;
    summary(name: string, help: string, quantiles?: number[]): Summary;
    private getOrCreate;
    /**
     * Render all metrics in Prometheus exposition format.
     */
    serialize(): string;
    reset(): void;
    getMetricNames(): string[];
}
export declare class Counter {
    private entry;
    constructor(entry: MetricEntry);
    inc(labels?: MetricLabel, value?: number): void;
    get(labels?: MetricLabel): number;
}
export declare class Gauge {
    private entry;
    constructor(entry: MetricEntry);
    set(labels: MetricLabel, value: number): void;
    set(value: number): void;
    inc(labels?: MetricLabel, value?: number): void;
    dec(labels?: MetricLabel, value?: number): void;
    get(labels?: MetricLabel): number;
}
export declare class Histogram {
    private entry;
    readonly buckets: number[];
    constructor(entry: MetricEntry, buckets: number[]);
    observe(labels: MetricLabel, value: number): void;
    observe(value: number): void;
}
export declare class Summary {
    private entry;
    readonly quantiles: number[];
    constructor(entry: MetricEntry, quantiles: number[]);
    observe(labels: MetricLabel, value: number): void;
    observe(value: number): void;
}
export declare const defaultRegistry: MetricsRegistry;
export declare const testsTotal: Counter;
export declare const testDuration: Summary;
export declare const costTotal: Counter;
export declare const activeTests: Gauge;
export declare const tokensTotal: Counter;
/**
 * Record results from a completed test.
 */
export declare function recordTestResult(testName: string, passed: boolean, durationMs: number, model?: string, costUsd?: number): void;
/**
 * Get Prometheus-format metrics string from the default registry.
 */
export declare function getMetrics(): string;
export {};
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