Variable: CLIENT_ERROR_CODES

const CLIENT_ERROR_CODES: readonly ["transport_closed", "timeout", "invalid_state", "device_error", "media_failed", "token_required", "cancelled"];

Codes the client raises on its own, which the server has no vocabulary for.

Deliberately disjoint from the server's list: a host that logs err.code and finds transport_closed knows no server ever said it, and one that finds permission_denied knows one did.