import type { HealthRegistry, MetricsSink, MetricsSnapshot } from '../types/observability.js';
/** TLS options for HTTPS metrics endpoint. */
export interface MetricsTlsOptions {
    cert: string;
    key: string;
}
/**
 * Render a `MetricsSnapshot` as Prometheus text-format bytes. The output
 * always ends with a trailing newline (Prometheus requires it).
 */
export declare function renderPrometheus(snapshot: MetricsSnapshot): string;
/** MIME type Prometheus servers must respond with on /metrics. */
export declare const PROMETHEUS_CONTENT_TYPE = "text/plain; version=0.0.4; charset=utf-8";
export interface MetricsServerOptions {
    port: number;
    /** Bind address. Defaults to 127.0.0.1 so we don't accidentally expose metrics publicly. */
    host?: string | undefined;
    sink: MetricsSink;
    /** Path to serve on. Defaults to /metrics. */
    path?: string | undefined;
    /**
     * V2-C: optional health registry. When provided, the server also responds
     * on `/healthz` (configurable via `healthPath`) with a JSON aggregate of
     * every registered health check. K8s probes expect a single HTTP server
     * exposing both `/metrics` and `/healthz`, so we mount them on the same
     * port rather than opening a sibling listener.
     */
    healthRegistry?: HealthRegistry | undefined;
    /** Path to serve health JSON on. Defaults to /healthz. */
    healthPath?: string | undefined;
    /** Enable HTTPS by providing TLS key/cert. Both required. */
    tls?: MetricsTlsOptions | undefined;
}
export interface MetricsServerHandle {
    port: number;
    url: string;
    close(): Promise<void>;
}
/**
 * Start an HTTP server that exposes a Prometheus scrape endpoint.
 * Uses node:http directly to avoid pulling a framework into the core graph.
 *
 * Why bind to 127.0.0.1 by default: telemetry endpoints inside an agent
 * process can leak prompt content via metric labels (tool name, error
 * message, etc.). The default keeps that on the loopback interface;
 * operators who want network scraping opt in explicitly with host: '0.0.0.0'.
 */
export declare function startMetricsServer(opts: MetricsServerOptions): Promise<MetricsServerHandle>;
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