/**
 * SEP-414 W3C Trace Context propagation.
 *
 * On the 2026-07-28 revision, distributed-tracing keys travel in the per-request
 * `_meta` envelope under fixed names: `traceparent`, `tracestate`, `baggage`.
 * NitroStack lifts them into `ExecutionContext.trace` so guards, interceptors,
 * and loggers can correlate a tool call across the host, this server, and any
 * downstream call — without NitroStack introducing its own tracing backend.
 *
 * @module
 */
/**
 * W3C Trace Context extracted from a request `_meta` envelope.
 */
export interface TraceContext {
    /** `traceparent` header value (W3C Trace Context). */
    traceparent?: string;
    /** `tracestate` header value. */
    tracestate?: string;
    /** `baggage` header value (W3C Baggage). */
    baggage?: string;
}
/**
 * Extract a `TraceContext` from an envelope/meta object, or `undefined` when no
 * trace keys are present. Accepts either the lifted `_meta` envelope
 * (`ctx.mcpReq.envelope`) or a raw `_meta` record; both the bare
 * (`traceparent`) and reverse-DNS (`io.modelcontextprotocol/traceparent`)
 * forms are recognized.
 */
export declare function extractTraceContext(source: Record<string, unknown> | undefined | null): TraceContext | undefined;
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