/**
 * Self-encoded session tokens for stateless / multi-pod MCP servers.
 *
 * A stateless server keeps nothing between requests, so every request starts a
 * new session and the client name/version (only sent at `initialize`) is lost.
 * The one value clients replay on every request is the `Mcp-Session-Id` header.
 * So at `initialize` we mint that header as a token carrying the session id and
 * client identity — any pod can read them back from the header alone.
 *
 * The token is unsigned: it holds only what the client already self-reports.
 */
export declare const MCP_SESSION_HEADER = "mcp-session-id";
/** What a session token carries. */
export interface SessionTokenPayload {
    /** PostHog session id (`ses_…`) → `$session_id`. */
    sessionId: string;
    /** MCP client name → `$mcp_client_name`. */
    clientName?: string;
    /** MCP client version → `$mcp_client_version`. */
    clientVersion?: string;
    /**
     * MCP protocol (spec) version → `$mcp_protocol_version`. The client's
     * *requested* version — the only one known when the token is minted (before
     * the initialize handler negotiates). Lets pods that never saw `initialize`
     * still stamp the spec version on their events.
     */
    protocolVersion?: string;
}
/**
 * Encodes a session token for the `Mcp-Session-Id` response header. Also
 * exported for SSE servers, which flush headers before handlers run and so
 * must set the header themselves at the HTTP layer.
 */
export declare function encodeSessionId(payload: SessionTokenPayload): string;
/**
 * Decodes an `Mcp-Session-Id` value into a token payload. Returns `null` for
 * anything that isn't one of our tokens (transport UUIDs, JWTs, garbage) and
 * never throws.
 */
export declare function decodeSessionId(value: unknown): SessionTokenPayload | null;
/**
 * Reads the `mcp-session-id` header off `extra.requestInfo.headers`. The SDK
 * transports lowercase header keys; the fallback scan covers hand-built extras.
 */
export declare function readMcpSessionHeader(headers: unknown): string | undefined;
/**
 * Puts a minted token on the transport so it goes out as the `Mcp-Session-Id`
 * response header. The Node transport's `sessionId` is a getter backed by an
 * inner web-standard transport, so verify the write by reading back and fall
 * back to writing the inner one. Returns whether the write stuck; never throws.
 */
export declare function writeSessionIdToTransport(transport: unknown, token: string): boolean;
//# sourceMappingURL=session-token.d.ts.map