import { Metadata } from '@grpc/grpc-js';
/** @internal Protocol version advertised in the `x-zrt-proto-version` header. */
export declare const PROTO_VERSION = "1";
/** @internal SDK identifier sent in the `x-zrt-sdk` header. */
export declare const SDK_NAME = "zrt-js";
/** @internal */
export declare const HEADER_SDK = "x-zrt-sdk";
/** @internal */
export declare const HEADER_SDK_VERSION = "x-zrt-sdk-version";
/** @internal */
export declare const HEADER_PROTO_VERSION = "x-zrt-proto-version";
/** @internal */
export declare const HEADER_DEVICE_OS = "x-zrt-device-os";
/** @internal */
export declare const HEADER_DEVICE_ARCH = "x-zrt-device-arch";
/** @internal */
export declare const HEADER_HOST = "x-zrt-host";
/** @internal */
export declare const HEADER_AUTHORIZATION = "authorization";
/** @internal Per-session ownership secret returned by CreateSession. */
export declare const HEADER_SESSION_CAPABILITY = "x-session-capability";
/** @internal The non-auth identity header keys included on every request. */
export declare const STATIC_HEADER_KEYS: readonly ["x-zrt-sdk", "x-zrt-sdk-version", "x-zrt-proto-version", "x-zrt-device-os", "x-zrt-device-arch", "x-zrt-host"];
/** @internal SDK version from `package.json` (cached); `'0.0.0'` on failure. */
export declare function sdkVersion(): string;
/** Identity headers as `[key, value]` tuples; adds `authorization: Bearer <token>` from `authToken` or `ZRT_AUTH_TOKEN` if set. Fresh array per call. */
export declare function clientMetadataTuples(authToken?: string): Array<[string, string]>;
/** @internal Transport `Metadata` from {@link clientMetadataTuples}. */
export declare function clientMetadata(authToken?: string): Metadata;
/** @internal Set/clear the `x-session-capability` secret so later RPCs prove session ownership. */
export declare function setSessionCapability(md: Metadata, capability?: string): void;