/**
 * Header sniffing: identify a `.rcap` and read its versions from the CLEARTEXT prefix — the magic and
 * the two varuint versions live outside the gzip precisely so tooling can route/filter/version-gate
 * files without decompressing (FileFormat.md "Overall layout"). Detection is by magic bytes, never by
 * file extension. Returns `null` for anything that isn't a well-formed `.rcap` prefix; it never
 * throws. Unlike `unpack`, an unknown codec version is still REPORTED here (the header is readable
 * even when the body isn't walkable) — that is what lets a tool say "newer than this build" precisely.
 *
 * Deliberately self-contained (magic + two LEB128 reads) rather than reusing the body decoder: sniff
 * must stay cheap to import and total over hostile input, where the body reader is right to throw.
 */
export interface RcapHeader {
    codecVersion: number;
    formatVersion: number;
    /** Whether THIS build's `unpack` can walk the body (`codecVersion` ≤ its `CODEC_VERSION`). */
    readable: boolean;
}
export declare function sniff(bytes: Uint8Array | ArrayBuffer): RcapHeader | null;
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