/**
 * Base64 encoding for binary data.
 *
 * Used by the request layer (`request.ts`) and session recording
 * (`extensions/replay/session-recording.ts`) to send gzip-compressed bodies
 * over `navigator.sendBeacon` as **text** rather than as a binary `Blob`.
 *
 * Why this exists:
 *
 *   `sendBeacon(url, blob)` with a binary `Blob` (e.g. a gzipped Uint8Array)
 *   is racy. Browsers queue the beacon synchronously, then serialize the
 *   body to the network *after* the JS context has been torn down on
 *   `pagehide` / tab discard. If the underlying `ArrayBuffer` is detached
 *   or GC'd before that flush, the wire body ends up empty or truncated —
 *   while the URL we already committed still carries `?compression=gzip-js`.
 *   The server then tries `gunzipSync` against an empty buffer and throws
 *   `Z_BUF_ERROR: unexpected end of file`.
 *
 *   Sending the gzip bytes as a base64 *string* sidesteps the problem
 *   entirely: `Blob([string])` owns its own UTF-8 encoded copy, and
 *   `sendBeacon` is reliable for text bodies. The server already accepts
 *   `?compression=base64` for this exact path.
 */
/**
 * Encode a `Uint8Array` to a base64 string using `btoa`.
 *
 * Chunks the bytes through `String.fromCharCode` so we don't blow the
 * argument-count limit on `apply()` for large buffers.
 */
export declare function uint8ArrayToBase64(bytes: Uint8Array): string;