/**
 * W3C Trace Context provider.
 *
 * Reads the consumer's currently-active OTel `Context` and serializes the
 * active span's `SpanContext` into a W3C `traceparent` header value
 * (`00-<trace_id>-<span_id>-<trace_flags>`). The `tracestate` arm carries any
 * vendor-specific propagation data attached upstream.
 *
 * Without an `OTelAPI` (or with an OTel API but no active recording span), the
 * provider falls back to the per-envelope filler — a fresh, valid 55-char
 * `traceparent` per call. The QAR server tolerates the synthetic value; what it
 * doesn't tolerate is an empty string (the schema enforces the regex).
 */
import type { OTelAPI } from '../tracing/types.js';
/** Concrete `trace_context` value the SDK writes onto every outbound envelope. */
export interface TraceContextValue {
    /** Always present, always 55 chars (`00-<32hex>-<16hex>-<2hex>`). */
    readonly traceparent: string;
    /** Optional, only when the active context has a non-empty tracestate. */
    readonly tracestate?: string;
}
/** Build a W3C `traceparent` from the components of a SpanContext. */
export declare function formatTraceparent(traceId: string, spanId: string, traceFlags: number): string;
/**
 * Provider for the per-envelope `trace_context`. Stateless — every call reads
 * the live OTel context anew. Cheap; no caching needed (a hot envelope path
 * does ~1 read per send).
 */
export declare class TraceContextProvider {
    private readonly otel;
    /**
     * @param otel  Optional OTel API. When `undefined`, every `current()` call
     *              returns a fresh random traceparent.
     */
    constructor(otel: OTelAPI | undefined);
    /**
     * The wire `trace_context` for an outbound envelope — always a valid value.
     *
     * Returns {@link active}'s resolved SpanContext when a recording span is
     * live (stitching the envelope into the consumer's trace), otherwise a fresh
     * random 55-char filler. This is the WS arm: the envelope schema requires a
     * non-empty `trace_context` on every send, so there's no "omit" option here.
     */
    current(): TraceContextValue;
    /**
     * Resolve the active SpanContext, or `undefined` when there's no real
     * recording span to propagate.
     *
     * This is the HTTP-header arm: unlike the WS envelope (whose schema requires
     * a `trace_context` on every send, hence {@link current}'s filler fallback),
     * an outbound HTTP request has no such requirement. Returning `undefined`
     * lets the caller omit `traceparent` entirely when OTel isn't active —
     * fabricating a fresh random trace that continues nowhere is just noise on
     * the HTTP path.
     */
    active(): TraceContextValue | undefined;
    /** The currently-active recording span, or `undefined` if no OTel / no span. */
    private activeSpan;
}
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