diff --git a/benchmarks/actions/002_info.rb b/benchmarks/actions/002_info.rb
index ef99119d28..1b095ab02e 100644
--- a/benchmarks/actions/002_info.rb
+++ b/benchmarks/actions/002_info.rb
@@ -14,7 +14,6 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
-
 require_relative '../lib/benchmarks'
 
 Benchmarks.register \
diff --git a/elasticsearch-api/elasticsearch-api.gemspec b/elasticsearch-api/elasticsearch-api.gemspec
index b5d9602099..e9aa5f48c3 100644
--- a/elasticsearch-api/elasticsearch-api.gemspec
+++ b/elasticsearch-api/elasticsearch-api.gemspec
@@ -49,7 +49,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'ansi'
   s.add_development_dependency 'bundler'
   s.add_development_dependency 'elasticsearch'
-  s.add_development_dependency 'elasticsearch-transport'
   s.add_development_dependency 'minitest'
   s.add_development_dependency 'minitest-reporters'
   s.add_development_dependency 'mocha'
diff --git a/elasticsearch-api/spec/spec_helper.rb b/elasticsearch-api/spec/spec_helper.rb
index 0983297570..82a66f5bf3 100644
--- a/elasticsearch-api/spec/spec_helper.rb
+++ b/elasticsearch-api/spec/spec_helper.rb
@@ -28,7 +28,6 @@
 require 'jbuilder'
 require 'jsonify'
 require 'elasticsearch'
-require 'elasticsearch-transport'
 require 'elasticsearch-api'
 
 require 'ansi'
diff --git a/elasticsearch-transport/lib/elasticsearch/transport.rb b/elasticsearch-transport/lib/elasticsearch/transport.rb
index 696a469973..c142d8228f 100644
--- a/elasticsearch-transport/lib/elasticsearch/transport.rb
+++ b/elasticsearch-transport/lib/elasticsearch/transport.rb
@@ -35,15 +35,3 @@
 require "elasticsearch/transport/redacted"
 
 require "elasticsearch/transport/version"
-
-module Elasticsearch
-  module Client
-
-    # A convenience wrapper for {::Elasticsearch::Transport::Client#initialize}.
-    #
-    def new(arguments={}, &block)
-      Elasticsearch::Transport::Client.new(arguments, &block)
-    end
-    extend self
-  end
-end
diff --git a/elasticsearch-transport/lib/elasticsearch/transport/client.rb b/elasticsearch-transport/lib/elasticsearch/transport/client.rb
index 12885aab65..bbaee5e849 100644
--- a/elasticsearch-transport/lib/elasticsearch/transport/client.rb
+++ b/elasticsearch-transport/lib/elasticsearch/transport/client.rb
@@ -49,11 +49,6 @@ class Client
       # @since 7.0.0
       DEFAULT_HOST = 'localhost:9200'.freeze
 
-      # The default port to use if connecting using a Cloud ID.
-      #
-      # @since 7.2.0
-      DEFAULT_CLOUD_PORT = 9243
-
       # The default port to use if not otherwise specified.
       #
       # @since 7.2.0
@@ -118,18 +113,13 @@ class Client
       #   The default is false. Responses will automatically be inflated if they are compressed.
       #   If a custom transport object is used, it must handle the request compression and response inflation.
       #
-      # @option api_key [String, Hash] :api_key Use API Key Authentication, either the base64 encoding of `id` and `api_key`
-      #                                         joined by a colon as a String, or a hash with the `id` and `api_key` values.
-      # @option opaque_id_prefix [String] :opaque_id_prefix set a prefix for X-Opaque-Id when initializing the client.
-      #                                                     This will be prepended to the id you set before each request
-      #                                                     if you're using X-Opaque-Id
       # @option enable_meta_header [Boolean] :enable_meta_header Enable sending the meta data header to Cloud.
       #                                                          (Default: true)
       #
       # @yield [faraday] Access and configure the `Faraday::Connection` instance directly with a block
       #
       def initialize(arguments = {}, &block)
-        @options = arguments.each_with_object({}) { |(k, v), args| args[k.to_sym] = v }
+        @options = arguments.transform_keys(&:to_sym)
         @arguments = @options
         @arguments[:logger] ||= @arguments[:log]   ? DEFAULT_LOGGER.call() : nil
         @arguments[:tracer] ||= @arguments[:trace] ? DEFAULT_TRACER.call() : nil
@@ -139,21 +129,17 @@ def initialize(arguments = {}, &block)
         @arguments[:randomize_hosts]    ||= false
         @arguments[:transport_options]  ||= {}
         @arguments[:http]               ||= {}
-        @arguments[:enable_meta_header] = arguments.fetch(:enable_meta_header) { true }
+        @arguments[:enable_meta_header] = arguments.fetch(:enable_meta_header, true)
         @options[:http]                 ||= {}
 
-        set_api_key if (@api_key = @arguments[:api_key])
-
-        @seeds = extract_cloud_creds(@arguments)
-        @seeds ||= __extract_hosts(@arguments[:hosts] ||
-                                   @arguments[:host] ||
-                                   @arguments[:url] ||
-                                   @arguments[:urls] ||
-                                   ENV['ELASTICSEARCH_URL'] ||
-                                   DEFAULT_HOST)
+        @hosts = __extract_hosts(@arguments[:hosts] ||
+                                 @arguments[:host] ||
+                                 @arguments[:url] ||
+                                 @arguments[:urls] ||
+                                 ENV['ELASTICSEARCH_URL'] ||
+                                 DEFAULT_HOST)
 
         @send_get_body_as = @arguments[:send_get_body_as] || 'GET'
-        @opaque_id_prefix = @arguments[:opaque_id_prefix] || nil
 
         if @arguments[:request_timeout]
           @arguments[:transport_options][:request] = { timeout: @arguments[:request_timeout] }
@@ -166,38 +152,25 @@ def initialize(arguments = {}, &block)
           @transport = if @transport_class == Transport::HTTP::Faraday
                          @arguments[:adapter] ||= __auto_detect_adapter
                          set_meta_header # from include MetaHeader
-                         @transport_class.new(hosts: @seeds, options: @arguments) do |faraday|
+                         @transport_class.new(hosts: @hosts, options: @arguments) do |faraday|
                            faraday.adapter(@arguments[:adapter])
                            block&.call faraday
                          end
                        else
                          set_meta_header # from include MetaHeader
-                         @transport_class.new(hosts: @seeds, options: @arguments)
+                         @transport_class.new(hosts: @hosts, options: @arguments)
                        end
         end
       end
-
       # Performs a request through delegation to {#transport}.
       #
       def perform_request(method, path, params = {}, body = nil, headers = nil)
         method = @send_get_body_as if 'GET' == method && body
-        if (opaque_id = params.delete(:opaque_id))
-          headers = {} if headers.nil?
-          opaque_id = @opaque_id_prefix ? "#{@opaque_id_prefix}#{opaque_id}" : opaque_id
-          headers.merge!('X-Opaque-Id' => opaque_id)
-        end
         transport.perform_request(method, path, params, body, headers)
       end
 
       private
 
-      def set_api_key
-        @api_key = __encode(@api_key) if @api_key.is_a? Hash
-        add_header('Authorization' => "ApiKey #{@api_key}")
-        @arguments.delete(:user)
-        @arguments.delete(:password)
-      end
-
       def add_header(header)
         headers = @arguments[:transport_options]&.[](:headers) || {}
         headers.merge!(header)
@@ -206,30 +179,6 @@ def add_header(header)
         )
       end
 
-      def extract_cloud_creds(arguments)
-        return unless arguments[:cloud_id] && !arguments[:cloud_id].empty?
-
-        name = arguments[:cloud_id].split(':')[0]
-        cloud_url, elasticsearch_instance = Base64.decode64(arguments[:cloud_id].gsub("#{name}:", '')).split('$')
-
-        if cloud_url.include?(':')
-          url, port = cloud_url.split(':')
-          host = "#{elasticsearch_instance}.#{url}"
-        else
-          host = "#{elasticsearch_instance}.#{cloud_url}"
-          port = arguments[:port] || DEFAULT_CLOUD_PORT
-        end
-        [
-          {
-            scheme: 'https',
-            user: arguments[:user],
-            password: arguments[:password],
-            host: host,
-            port: port.to_i
-          }
-        ]
-      end
-
       # Normalizes and returns hosts configuration.
       #
       # Arrayifies the `hosts_config` argument and extracts `host` and `port` info from strings.
@@ -328,13 +277,6 @@ def __auto_detect_adapter
           ::Faraday.default_adapter
         end
       end
-
-      # Encode credentials for the Authorization Header
-      # Credentials is the base64 encoding of id and api_key joined by a colon
-      # @see https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-create-api-key.html
-      def __encode(api_key)
-        Base64.strict_encode64([api_key[:id], api_key[:api_key]].join(':'))
-      end
     end
   end
 end
diff --git a/elasticsearch-transport/spec/elasticsearch/transport/base_spec.rb b/elasticsearch-transport/spec/elasticsearch/transport/base_spec.rb
index 6fa7d3500a..c93c25061f 100644
--- a/elasticsearch-transport/spec/elasticsearch/transport/base_spec.rb
+++ b/elasticsearch-transport/spec/elasticsearch/transport/base_spec.rb
@@ -31,14 +31,14 @@
       it 'does not include the password in the logged string' do
         expect(logger).not_to receive(:error).with(/secret_password/)
         expect {
-          client.cluster.stats
+          client.perform_request('GET', '/_cluster/stats')
         }.to raise_exception(Faraday::ConnectionFailed)
       end
 
       it 'replaces the password with the string \'REDACTED\'' do
         expect(logger).to receive(:error).with(/REDACTED/)
         expect {
-          client.cluster.stats
+          client.perform_request('GET', '/_cluster/stats')
         }.to raise_exception(Faraday::ConnectionFailed)
       end
     end
@@ -93,7 +93,7 @@
     end
 
     it 'raises an exception' do
-      expect { client.info }.to raise_exception(Faraday::ConnectionFailed)
+      expect { client.perform_request('GET', '/info') }.to raise_exception(Faraday::ConnectionFailed)
     end
   end
 
diff --git a/elasticsearch-transport/spec/elasticsearch/transport/client_spec.rb b/elasticsearch-transport/spec/elasticsearch/transport/client_spec.rb
index cea79bbdac..fa731f4f5f 100644
--- a/elasticsearch-transport/spec/elasticsearch/transport/client_spec.rb
+++ b/elasticsearch-transport/spec/elasticsearch/transport/client_spec.rb
@@ -24,10 +24,6 @@
     end
   end
 
-  it 'is aliased as Elasticsearch::Client' do
-    expect(Elasticsearch::Client.new).to be_a(described_class)
-  end
-
   it 'has a default transport' do
     expect(client.transport).to be_a(Elasticsearch::Transport::Client::DEFAULT_TRANSPORT_CLASS)
   end
@@ -70,48 +66,6 @@
     end
   end
 
-  context 'when an encoded api_key is provided' do
-    let(:client) do
-      described_class.new(api_key: 'an_api_key')
-    end
-    let(:authorization_header) do
-      client.transport.connections.first.connection.headers['Authorization']
-    end
-
-    it 'Adds the ApiKey header to the connection' do
-      expect(authorization_header).to eq('ApiKey an_api_key')
-    end
-  end
-
-  context 'when an un-encoded api_key is provided' do
-    let(:client) do
-      described_class.new(api_key: { id: 'my_id', api_key: 'my_api_key' })
-    end
-    let(:authorization_header) do
-      client.transport.connections.first.connection.headers['Authorization']
-    end
-
-    it 'Adds the ApiKey header to the connection' do
-      expect(authorization_header).to eq("ApiKey #{Base64.strict_encode64('my_id:my_api_key')}")
-    end
-  end
-
-  context 'when basic auth and api_key are provided' do
-    let(:client) do
-      described_class.new(
-        api_key: { id: 'my_id', api_key: 'my_api_key' },
-        host: 'http://elastic:password@localhost:9200'
-      )
-    end
-    let(:authorization_header) do
-      client.transport.connections.first.connection.headers['Authorization']
-    end
-
-    it 'removes basic auth credentials' do
-      expect(authorization_header).not_to match(/^Basic/)
-      expect(authorization_header).to match(/^ApiKey/)
-    end
-  end
 
   context 'when a user-agent header is specified as client option in lower-case' do
 
@@ -327,158 +281,6 @@
     end
   end
 
-  context 'when cloud credentials are provided' do
-    let(:client) do
-      described_class.new(
-        cloud_id: 'name:bG9jYWxob3N0JGFiY2QkZWZnaA==',
-        user: 'elastic',
-        password: 'changeme'
-      )
-    end
-
-    let(:hosts) do
-      client.transport.hosts
-    end
-
-    it 'extracts the cloud credentials' do
-      expect(hosts[0][:host]).to eq('abcd.localhost')
-      expect(hosts[0][:protocol]).to eq('https')
-      expect(hosts[0][:user]).to eq('elastic')
-      expect(hosts[0][:password]).to eq('changeme')
-      expect(hosts[0][:port]).to eq(9243)
-    end
-
-    it 'creates the correct full url' do
-      expect(
-        client.transport.__full_url(client.transport.hosts[0])
-      ).to eq('https://elastic:changeme@abcd.localhost:9243')
-    end
-
-    context 'when a port is specified' do
-      let(:client) do
-        described_class.new(
-          cloud_id: 'name:bG9jYWxob3N0JGFiY2QkZWZnaA==',
-          user: 'elastic',
-          password: 'changeme',
-          port: 9250
-        )
-      end
-
-      it 'sets the specified port along with the cloud credentials' do
-        expect(hosts[0][:host]).to eq('abcd.localhost')
-        expect(hosts[0][:protocol]).to eq('https')
-        expect(hosts[0][:user]).to eq('elastic')
-        expect(hosts[0][:password]).to eq('changeme')
-        expect(hosts[0][:port]).to eq(9250)
-      end
-
-      it 'creates the correct full url' do
-        expect(client.transport.__full_url(client.transport.hosts[0])).to eq('https://elastic:changeme@abcd.localhost:9250')
-      end
-    end
-
-    context 'when the cluster has alternate names' do
-      let(:client) do
-        described_class.new(
-          cloud_id: 'myCluster:bG9jYWxob3N0JGFiY2QkZWZnaA==',
-          user: 'elasticfantastic',
-          password: 'tobechanged'
-        )
-      end
-
-      let(:hosts) do
-        client.transport.hosts
-      end
-
-      it 'extracts the cloud credentials' do
-        expect(hosts[0][:host]).to eq('abcd.localhost')
-        expect(hosts[0][:protocol]).to eq('https')
-        expect(hosts[0][:user]).to eq('elasticfantastic')
-        expect(hosts[0][:password]).to eq('tobechanged')
-        expect(hosts[0][:port]).to eq(9243)
-      end
-
-      it 'creates the correct full url' do
-        expect(
-          client.transport.__full_url(client.transport.hosts[0])
-        ).to eq('https://elasticfantastic:tobechanged@abcd.localhost:9243')
-      end
-    end
-
-    context 'when decoded cloud id has a trailing dollar sign' do
-      let(:client) do
-        described_class.new(
-          cloud_id: 'a_cluster:bG9jYWxob3N0JGFiY2Qk',
-          user: 'elasticfantastic',
-          password: 'changeme'
-        )
-      end
-
-      let(:hosts) do
-        client.transport.hosts
-      end
-
-      it 'extracts the cloud credentials' do
-        expect(hosts[0][:host]).to eq('abcd.localhost')
-        expect(hosts[0][:protocol]).to eq('https')
-        expect(hosts[0][:user]).to eq('elasticfantastic')
-        expect(hosts[0][:password]).to eq('changeme')
-        expect(hosts[0][:port]).to eq(9243)
-      end
-
-      it 'creates the correct full url' do
-        expect(
-          client.transport.__full_url(client.transport.hosts[0])
-        ).to eq('https://elasticfantastic:changeme@abcd.localhost:9243')
-      end
-    end
-
-    context 'when the cloud host provides a port' do
-      let(:client) do
-        described_class.new(
-          cloud_id: 'name:ZWxhc3RpY19zZXJ2ZXI6OTI0MyRlbGFzdGljX2lk',
-          user: 'elastic',
-          password: 'changeme'
-        )
-      end
-
-      let(:hosts) do
-        client.transport.hosts
-      end
-
-      it 'creates the correct full url' do
-        expect(hosts[0][:host]).to eq('elastic_id.elastic_server')
-        expect(hosts[0][:protocol]).to eq('https')
-        expect(hosts[0][:user]).to eq('elastic')
-        expect(hosts[0][:password]).to eq('changeme')
-        expect(hosts[0][:port]).to eq(9243)
-      end
-    end
-
-    context 'when the cloud host provides a port and the port is also specified' do
-      let(:client) do
-        described_class.new(
-          cloud_id: 'name:ZWxhc3RpY19zZXJ2ZXI6OTI0MyRlbGFzdGljX2lk',
-          user: 'elastic',
-          password: 'changeme',
-          port: 9200
-        )
-      end
-
-      let(:hosts) do
-        client.transport.hosts
-      end
-
-      it 'creates the correct full url' do
-        expect(hosts[0][:host]).to eq('elastic_id.elastic_server')
-        expect(hosts[0][:protocol]).to eq('https')
-        expect(hosts[0][:user]).to eq('elastic')
-        expect(hosts[0][:password]).to eq('changeme')
-        expect(hosts[0][:port]).to eq(9243)
-      end
-    end
-  end
-
   shared_examples_for 'a client that extracts hosts' do
     context 'when the host is a String' do
       context 'when there is a protocol specified' do
@@ -553,7 +355,6 @@
           end
 
           context 'when there is a port specified \'http://myhost:7101\'' do
-
             let(:host) do
               'http://myhost:7101'
             end
@@ -571,7 +372,6 @@
             end
 
             context 'when there is a path specified \'http://myhost:7101/api\'' do
-
               let(:host) do
                 'http://myhost:7101/api'
               end
@@ -603,9 +403,7 @@
         end
 
         context 'when the protocol is https' do
-
           context 'when there is no port specified \'https://myhost\'' do
-
             let(:host) do
               'https://myhost'
             end
@@ -624,7 +422,6 @@
           end
 
           context 'when there is a port specified \'https://myhost:7101\'' do
-
             let(:host) do
               'https://myhost:7101'
             end
@@ -1026,7 +823,6 @@
     end
 
     context 'when the hosts is invalid' do
-
       let(:host) do
         123
       end
@@ -1040,7 +836,6 @@
   end
 
   context 'when hosts are specified with the \'host\' key' do
-
     let(:client) do
       described_class.new(host: ['host1', 'host2', 'host3', 'host4'], randomize_hosts: true)
     end
@@ -1055,7 +850,6 @@
   end
 
   context 'when hosts are specified with the \'host\' key as a String' do
-
     let(:client) do
       described_class.new('host' => ['host1', 'host2', 'host3', 'host4'], 'randomize_hosts' => true)
     end
@@ -1070,7 +864,6 @@
   end
 
   context 'when hosts are specified with the \'hosts\' key' do
-
     let(:client) do
       described_class.new(hosts: host)
     end
@@ -1083,7 +876,6 @@
   end
 
   context 'when hosts are specified with the \'hosts\' key as a String' do
-
     let(:client) do
       described_class.new('hosts' => host)
     end
@@ -1096,7 +888,6 @@
   end
 
   context 'when hosts are specified with the \'url\' key' do
-
     let(:client) do
       described_class.new(url: host)
     end
@@ -1109,7 +900,6 @@
   end
 
   context 'when hosts are specified with the \'url\' key as a String' do
-
     let(:client) do
       described_class.new('url' => host)
     end
@@ -1122,7 +912,6 @@
   end
 
   context 'when hosts are specified with the \'urls\' key' do
-
     let(:client) do
       described_class.new(urls: host)
     end
@@ -1135,7 +924,6 @@
   end
 
   context 'when hosts are specified with the \'urls\' key as a String' do
-
     let(:client) do
       described_class.new('urls' => host)
     end
@@ -1332,7 +1120,6 @@
     end
 
     context 'when \'request_timeout\' is defined' do
-
       let(:client) do
         described_class.new(request_timeout: 120)
       end
@@ -1343,7 +1130,6 @@
     end
 
     context 'when \'request_timeout\' is defined as a String key' do
-
       let(:client) do
         described_class.new('request_timeout' => 120)
       end
@@ -1355,7 +1141,6 @@
   end
 
   describe '#perform_request' do
-
     let(:transport_instance) do
       Class.new { def initialize(*); end }.new
     end
@@ -1370,15 +1155,17 @@
     end
 
     context 'when the \'send_get_body_as\' option is specified' do
-
       let(:client) do
         described_class.new(transport: transport_instance, :send_get_body_as => 'POST')
       end
 
       before do
-        expect(transport_instance).to receive(:perform_request).with('POST', '/', {},
-                                                                     '{"foo":"bar"}',
-                                                                     '{"Content-Type":"application/x-ndjson"}').and_return(true)
+        expect(transport_instance).to receive(:perform_request)
+                                        .with(
+                                          'POST', '/', {},
+                                          '{"foo":"bar"}',
+                                          '{"Content-Type":"application/x-ndjson"}'
+                                        ).and_return(true)
       end
 
       let(:request) do
@@ -1390,40 +1177,6 @@
       end
     end
 
-    context 'when x-opaque-id is set' do
-      let(:client) { described_class.new(host: hosts) }
-
-      it 'uses x-opaque-id on a request' do
-        expect(client.perform_request('GET', '/', { opaque_id: '12345' }).headers['x-opaque-id']).to eq('12345')
-      end
-    end
-
-    context 'when an x-opaque-id prefix is set on initialization' do
-      let(:prefix) { 'elastic_cloud' }
-      let(:client) do
-        described_class.new(host: hosts, opaque_id_prefix: prefix)
-      end
-
-      it 'uses x-opaque-id on a request' do
-        expect(client.perform_request('GET', '/', { opaque_id: '12345' }).headers['x-opaque-id']).to eq("#{prefix}12345")
-      end
-
-      context 'when using an API call' do
-        let(:client) { described_class.new(host: hosts) }
-
-        it 'doesnae raise an ArgumentError' do
-          expect { client.search(opaque_id: 'no_error') }.not_to raise_error
-        end
-
-        it 'uses X-Opaque-Id in the header' do
-          allow(client).to receive(:perform_request) { OpenStruct.new(body: '') }
-          expect { client.search(opaque_id: 'opaque_id') }.not_to raise_error
-          expect(client).to have_received(:perform_request)
-                              .with('GET', '_search', { opaque_id: 'opaque_id' }, nil, {})
-        end
-      end
-    end
-
     context 'when Elasticsearch response includes a warning header' do
       let(:client) do
         Elasticsearch::Transport::Client.new(hosts: hosts)
@@ -1449,39 +1202,6 @@
         end
       end
     end
-
-    context 'when a header is set on an endpoint request' do
-      let(:client) { described_class.new(host: hosts) }
-      let(:headers) { { 'user-agent' => 'my ruby app' } }
-
-      it 'performs the request with the header' do
-        allow(client).to receive(:perform_request) { OpenStruct.new(body: '') }
-        expect { client.search(headers: headers) }.not_to raise_error
-        expect(client).to have_received(:perform_request)
-                            .with('GET', '_search', {}, nil, headers)
-      end
-    end
-
-    context 'when a header is set on an endpoint request and on initialization' do
-      let!(:client) do
-        described_class.new(
-          host: hosts,
-          transport_options: { headers: instance_headers }
-        )
-      end
-      let(:instance_headers) { { set_in_instantiation: 'header value' } }
-      let(:param_headers) {{'user-agent' => 'My Ruby Tests', 'set-on-method-call' => 'header value'}}
-
-      it 'performs the request with the header' do
-        expected_headers = client.transport.connections.connections.first.connection.headers.merge(param_headers)
-
-        expect_any_instance_of(Faraday::Connection)
-          .to receive(:run_request)
-                .with(:get, "http://#{hosts[0]}/_search", nil, expected_headers) { OpenStruct.new(body: '')}
-
-        client.search(headers: param_headers)
-      end
-    end
   end
 
   context 'when the client connects to Elasticsearch' do
diff --git a/elasticsearch-transport/spec/elasticsearch/transport/meta_header_spec.rb b/elasticsearch-transport/spec/elasticsearch/transport/meta_header_spec.rb
index c70086f930..9eca75b85c 100644
--- a/elasticsearch-transport/spec/elasticsearch/transport/meta_header_spec.rb
+++ b/elasticsearch-transport/spec/elasticsearch/transport/meta_header_spec.rb
@@ -78,22 +78,6 @@ def meta_version
       end
     end
 
-    context 'when using API Key' do
-      let(:client) do
-        described_class.new(api_key: 'an_api_key', adapter: adapter)
-      end
-
-      let(:authorization_header) do
-        client.transport.connections.first.connection.headers['Authorization']
-      end
-
-      it 'adds the ApiKey header to the connection' do
-        expect(authorization_header).to eq('ApiKey an_api_key')
-        expect(subject['x-elastic-client-meta']).to match(regexp)
-        expect(subject).to include('x-elastic-client-meta' => meta_header)
-      end
-    end
-
     context 'adapters' do
       let(:meta_header) do
         if jruby?
@@ -258,8 +242,8 @@ class MyTransport
         include Elasticsearch::Transport::Transport::Base
         def initialize(args); end
       end
-      let(:client) { Elasticsearch::Client.new(transport_class: MyTransport) }
-      let(:subject){ client.instance_variable_get("@arguments")[:transport_options][:headers] }
+      let(:client) { Elasticsearch::Transport::Client.new(transport_class: MyTransport) }
+      let(:subject) { client.instance_variable_get('@arguments')[:transport_options][:headers] }
       let(:meta_header) do
         if jruby?
           "es=#{meta_version},rb=#{RUBY_VERSION},t=#{Elasticsearch::Transport::VERSION},jv=#{ENV_JAVA['java.version']},jr=#{JRUBY_VERSION}"
diff --git a/elasticsearch-xpack/lib/elasticsearch/xpack.rb b/elasticsearch-xpack/lib/elasticsearch/xpack.rb
index 9255e1629d..b7d45ac5e0 100644
--- a/elasticsearch-xpack/lib/elasticsearch/xpack.rb
+++ b/elasticsearch-xpack/lib/elasticsearch/xpack.rb
@@ -44,128 +44,117 @@ class Client
 Elasticsearch::API::COMMON_PARAMS.push :job_id, :datafeed_id, :filter_id, :snapshot_id, :category_id, :policy_id
 
 module Elasticsearch
-  module Transport
-    class Client
-      # When a method is called on the client, if it's one of the xpack root
-      # namespace methods, send them to the xpack client.
-      # E.g.: client.xpack.usage => client.usage
-      # Excluding `info` since OSS and XPACK both have info endpoints.
-      TOP_LEVEL_METHODS = [
-        :open_point_in_time,
-        :close_point_in_time,
-        :terms_enum,
-        :usage
-      ].freeze
-
-      def method_missing(method, *args, &block)
-        return xpack.send(method, *args, &block) if TOP_LEVEL_METHODS.include?(method)
-
-        super
-      end
+  class Client
+    # When a method is called on the client, if it's one of the xpack root
+    # namespace methods, send them to the xpack client.
+    # E.g.: client.xpack.usage => client.usage
+    # Excluding `info` since OSS and XPACK both have info endpoints.
+    TOP_LEVEL_METHODS = [:open_point_in_time, :close_point_in_time, :terms_enum, :usage].freeze
 
-      def respond_to_missing?(method_name, *args)
-        TOP_LEVEL_METHODS.include?(method_name) || super
+    TOP_LEVEL_METHODS.each do |method|
+      define_method :"#{method}" do |value|
+        xpack.send(method, *[value])
       end
+    end
 
-      def xpack
-        @xpack ||= Elasticsearch::XPack::API::Client.new(self)
-      end
+    def xpack
+      @xpack ||= Elasticsearch::XPack::API::Client.new(self)
+    end
 
-      def security
-        @security ||= xpack.security
-      end
+    def security
+      @security ||= xpack.security
+    end
 
-      def ml
-        @ml ||= xpack.ml
-      end
+    def ml
+      @ml ||= xpack.ml
+    end
 
-      def rollup
-        @rollup ||= xpack.rollup
-      end
+    def rollup
+      @rollup ||= xpack.rollup
+    end
 
-      def watcher
-        @watcher ||= xpack.watcher
-      end
+    def watcher
+      @watcher ||= xpack.watcher
+    end
 
-      def graph
-        @graph ||= xpack.graph
-      end
+    def graph
+      @graph ||= xpack.graph
+    end
 
-      def migration
-        @migration ||= xpack.migration
-      end
+    def migration
+      @migration ||= xpack.migration
+    end
 
-      def sql
-        @sql ||= xpack.sql
-      end
+    def sql
+      @sql ||= xpack.sql
+    end
 
-      def deprecation
-        @deprecation ||= xpack.deprecation
-      end
+    def deprecation
+      @deprecation ||= xpack.deprecation
+    end
 
-      def data_frame
-        @data_frame ||= xpack.data_frame
-      end
+    def data_frame
+      @data_frame ||= xpack.data_frame
+    end
 
-      def ilm
-        @ilm ||= xpack.ilm
-      end
+    def ilm
+      @ilm ||= xpack.ilm
+    end
 
-      def license
-        @license ||= xpack.license
-      end
+    def license
+      @license ||= xpack.license
+    end
 
-      def transform
-        @transform ||= xpack.transform
-      end
+    def transform
+      @transform ||= xpack.transform
+    end
 
-      def async_search
-        @async_search ||= xpack.async_search
-      end
+    def async_search
+      @async_search ||= xpack.async_search
+    end
 
-      def cat
-        @cat ||= xpack.cat
-      end
+    def cat
+      @cat ||= xpack.cat
+    end
 
-      def indices
-        @indices ||= xpack.indices
-      end
+    def indices
+      @indices ||= xpack.indices
+    end
 
-      def searchable_snapshots
-        @searchable_snapshots ||= xpack.searchable_snapshots
-      end
+    def searchable_snapshots
+      @searchable_snapshots ||= xpack.searchable_snapshots
+    end
 
-      def cross_cluster_replication
-        @cross_cluster_replication ||= xpack.cross_cluster_replication
-      end
+    def cross_cluster_replication
+      @cross_cluster_replication ||= xpack.cross_cluster_replication
+    end
 
-      def autoscaling
-        @autoscaling ||= xpack.autoscaling
-      end
+    def autoscaling
+      @autoscaling ||= xpack.autoscaling
+    end
 
-      def enrich
-        @enrich ||= xpack.enrich
-      end
+    def enrich
+      @enrich ||= xpack.enrich
+    end
 
-      def eql
-        @eql ||= xpack.eql
-      end
+    def eql
+      @eql ||= xpack.eql
+    end
 
-      def snapshot_lifecycle_management
-        @snapshot_lifecycle_management ||= xpack.snapshot_lifecycle_management
-      end
+    def snapshot_lifecycle_management
+      @snapshot_lifecycle_management ||= xpack.snapshot_lifecycle_management
+    end
 
-      def text_structure
-        @text_structure ||= xpack.text_structure
-      end
+    def text_structure
+      @text_structure ||= xpack.text_structure
+    end
 
-      def logstash
-        @logstash ||= xpack.logstash
-      end
+    def logstash
+      @logstash ||= xpack.logstash
+    end
 
-      def fleet
-        @fleet ||= xpack.fleet
-      end
+    def fleet
+      @fleet ||= xpack.fleet
     end
   end
-end if defined?(Elasticsearch::Transport::Client)
+end if defined?(Elasticsearch::Client)
diff --git a/elasticsearch-xpack/test/test_helper.rb b/elasticsearch-xpack/test/test_helper.rb
index 3772e020c9..c452cc462b 100644
--- a/elasticsearch-xpack/test/test_helper.rb
+++ b/elasticsearch-xpack/test/test_helper.rb
@@ -26,7 +26,7 @@
 
 require 'ansi'
 
-require 'elasticsearch/transport'
+require 'elasticsearch'
 require 'elasticsearch/xpack'
 
 Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
@@ -58,7 +58,7 @@ def perform_request(method, path, params, body)
       end
 
       # Top level methods:
-      Elasticsearch::Transport::Client::TOP_LEVEL_METHODS.each do |method|
+      Elasticsearch::Client::TOP_LEVEL_METHODS.each do |method|
         define_method method do |*args|
           xpack.send(method, *args)
         end
diff --git a/elasticsearch/lib/elasticsearch.rb b/elasticsearch/lib/elasticsearch.rb
index 1267f62377..d407394b3e 100644
--- a/elasticsearch/lib/elasticsearch.rb
+++ b/elasticsearch/lib/elasticsearch.rb
@@ -20,12 +20,102 @@
 require 'elasticsearch/api'
 
 module Elasticsearch
-  module Transport
-    class Client
-      include Elasticsearch::API
+  # This is the stateful Elasticsearch::Client, using an instance of elasticsearch-transport.
+  class Client
+    include Elasticsearch::API
+    # The default port to use if connecting using a Cloud ID.
+    # Updated from 9243 to 443 in client version 7.10.1
+    #
+    # @since 7.2.0
+    DEFAULT_CLOUD_PORT = 443
+
+    # Create a client connected to an Elasticsearch cluster.
+    #
+    # @option arguments [String] :cloud_id - The Cloud ID to connect to Elastic Cloud
+    # @option api_key [String, Hash] :api_key Use API Key Authentication, either the base64 encoding of `id` and `api_key`
+    #                                         joined by a colon as a String, or a hash with the `id` and `api_key` values.
+    # @option opaque_id_prefix [String] :opaque_id_prefix set a prefix for X-Opaque-Id when initializing the client.
+    #                                                     This will be prepended to the id you set before each request
+    #                                                     if you're using X-Opaque-Id
+    def initialize(arguments = {}, &block)
+      @opaque_id_prefix = arguments[:opaque_id_prefix] || nil
+      api_key(arguments) if arguments[:api_key]
+      if arguments[:cloud_id]
+        arguments[:hosts] = setup_cloud_host(
+          arguments[:cloud_id],
+          arguments[:user],
+          arguments[:password],
+          arguments[:port]
+        )
+      end
+      @transport = Elasticsearch::Transport::Client.new(arguments, &block)
+    end
+
+    def method_missing(name, *args, &block)
+      if methods.include?(name)
+        super
+      elsif name == :perform_request
+        # The signature for perform_request is:
+        # method, path, params, body, headers
+        if (opaque_id = args[2]&.delete(:opaque_id))
+          headers = args[4] || {}
+          opaque_id = @opaque_id_prefix ? "#{@opaque_id_prefix}#{opaque_id}" : opaque_id
+          args[4] = headers.merge('X-Opaque-Id' => opaque_id)
+        end
+        @transport.send(name, *args, &block)
+      else
+        @transport.send(name, *args, &block)
+      end
+    end
+
+    def respond_to_missing?(method_name, *args)
+      @transport.respond_to?(method_name) || super
+    end
+
+    private
+
+    def setup_cloud_host(cloud_id, user, password, port)
+      name = cloud_id.split(':')[0]
+      cloud_url, elasticsearch_instance = Base64.decode64(cloud_id.gsub("#{name}:", '')).split('$')
+
+      if cloud_url.include?(':')
+        url, port = cloud_url.split(':')
+        host = "#{elasticsearch_instance}.#{url}"
+      else
+        host = "#{elasticsearch_instance}.#{cloud_url}"
+        port ||= DEFAULT_CLOUD_PORT
+      end
+      [{ scheme: 'https', user: user, password: password, host: host, port: port.to_i }]
+    end
+
+    def api_key(arguments)
+      api_key = if arguments[:api_key].is_a? Hash
+                  encode(arguments[:api_key])
+                else
+                  arguments[:api_key]
+                end
+      arguments.delete(:user)
+      arguments.delete(:password)
+      authorization = { 'Authorization' => "ApiKey #{api_key}" }
+      if (headers = arguments.dig(:transport_options, :headers))
+        headers.merge!(authorization)
+      else
+        arguments[:transport_options] = {
+          headers: authorization
+        }
+      end
+    end
+
+    # Encode credentials for the Authorization Header
+    # Credentials is the base64 encoding of id and api_key joined by a colon
+    # @see https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-create-api-key.html
+    def encode(api_key)
+      Base64.strict_encode64([api_key[:id], api_key[:api_key]].join(':'))
     end
   end
 end
+
+# Helper for the meta-header value for Cloud
 module Elastic
   # If the version is X.X.X.pre/alpha/beta, use X.X.Xp for the meta-header:
   def self.client_meta_version
diff --git a/elasticsearch/spec/integration/client_integration_spec.rb b/elasticsearch/spec/integration/client_integration_spec.rb
index 2a55c1c8f7..d0f07b9471 100644
--- a/elasticsearch/spec/integration/client_integration_spec.rb
+++ b/elasticsearch/spec/integration/client_integration_spec.rb
@@ -17,9 +17,8 @@
 ELASTICSEARCH_URL = ENV['TEST_ES_SERVER'] || "http://localhost:#{(ENV['PORT'] || 9200)}"
 raise URI::InvalidURIError unless ELASTICSEARCH_URL =~ /\A#{URI::DEFAULT_PARSER.make_regexp}\z/
 
-require 'elasticsearch'
+require 'spec_helper'
 require 'logger'
-require 'rspec'
 
 context 'Elasticsearch client' do
   let(:logger) { Logger.new($stderr) }
diff --git a/elasticsearch/spec/spec_helper.rb b/elasticsearch/spec/spec_helper.rb
new file mode 100644
index 0000000000..0750a40696
--- /dev/null
+++ b/elasticsearch/spec/spec_helper.rb
@@ -0,0 +1,31 @@
+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. licenses this file to you under
+# the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+require 'elasticsearch'
+require 'rspec'
+
+RSpec.configure do |config|
+  config.formatter = :documentation
+end
+
+def meta_version
+  client.send(:client_meta_version, Elasticsearch::VERSION)
+end
+
+def jruby?
+  defined?(JRUBY_VERSION)
+end
diff --git a/elasticsearch/spec/unit/api_key_spec.rb b/elasticsearch/spec/unit/api_key_spec.rb
new file mode 100644
index 0000000000..5df47bd76d
--- /dev/null
+++ b/elasticsearch/spec/unit/api_key_spec.rb
@@ -0,0 +1,101 @@
+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. licenses this file to you under
+# the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+require 'spec_helper'
+
+describe Elasticsearch::Client do
+  context 'when using API Key' do
+    let(:authorization_header) do
+      client.transport.connections.first.connection.headers['Authorization']
+    end
+
+    context 'when an encoded api_key is provided' do
+      let(:client) do
+        described_class.new(api_key: 'an_api_key')
+      end
+
+      it 'Adds the ApiKey header to the connection' do
+        expect(authorization_header).to eq('ApiKey an_api_key')
+      end
+    end
+
+    context 'when an un-encoded api_key is provided' do
+      let(:client) do
+        described_class.new(api_key: { id: 'my_id', api_key: 'my_api_key' })
+      end
+
+      it 'Adds the ApiKey header to the connection' do
+        expect(authorization_header).to eq("ApiKey #{Base64.strict_encode64('my_id:my_api_key')}")
+      end
+    end
+
+    context 'when basic auth and api_key are provided' do
+      let(:client) do
+        described_class.new(
+          api_key: { id: 'my_id', api_key: 'my_api_key' },
+          host: 'http://elastic:password@localhost:9200'
+        )
+      end
+
+      it 'removes basic auth credentials' do
+        expect(authorization_header).not_to match(/^Basic/)
+        expect(authorization_header).to match(/^ApiKey/)
+      end
+    end
+
+    context 'when other headers where specified' do
+      let(:client) do
+        described_class.new(
+          api_key: 'elasticsearch_api_key',
+          transport_options: { headers: { 'x-test-header' => 'test' } }
+        )
+      end
+
+      it 'Adds the ApiKey header to the connection and keeps the header' do
+        header = client.transport.connections.first.connection.headers
+        expect(header['Authorization']).to eq('ApiKey elasticsearch_api_key')
+        expect(header['X-Test-Header']).to eq('test')
+      end
+    end
+
+    context 'Metaheader' do
+      let(:adapter_code) { "nh=#{defined?(Net::HTTP::VERSION) ? Net::HTTP::VERSION : Net::HTTP::HTTPVersion}" }
+      let(:meta_header) do
+        if jruby?
+          "es=#{meta_version},rb=#{RUBY_VERSION},t=#{Elasticsearch::Transport::VERSION},jv=#{ENV_JAVA['java.version']},jr=#{JRUBY_VERSION},fd=#{Faraday::VERSION},#{adapter_code}"
+        else
+          "es=#{meta_version},rb=#{RUBY_VERSION},t=#{Elasticsearch::Transport::VERSION},fd=#{Faraday::VERSION},#{adapter_code}"
+        end
+      end
+
+      context 'when using API Key' do
+        let(:client) do
+          described_class.new(api_key: 'an_api_key')
+        end
+
+        let(:headers) do
+          client.transport.connections.first.connection.headers
+        end
+
+        it 'adds the ApiKey header to the connection' do
+          expect(authorization_header).to eq('ApiKey an_api_key')
+          expect(headers).to include('x-elastic-client-meta' => meta_header)
+        end
+      end
+    end
+  end
+end
diff --git a/elasticsearch/spec/unit/cloud_credentials_spec.rb b/elasticsearch/spec/unit/cloud_credentials_spec.rb
new file mode 100644
index 0000000000..11b411eec8
--- /dev/null
+++ b/elasticsearch/spec/unit/cloud_credentials_spec.rb
@@ -0,0 +1,167 @@
+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. licenses this file to you under
+# the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+require 'spec_helper'
+
+describe Elasticsearch::Client do
+  context 'when cloud credentials are provided' do
+    let(:client) do
+      described_class.new(
+        cloud_id: 'name:bG9jYWxob3N0JGFiY2QkZWZnaA==',
+        user: 'elastic',
+        password: 'changeme'
+      )
+    end
+
+    let(:hosts) do
+      client.transport.hosts
+    end
+
+    it 'extracts the cloud credentials' do
+      expect(hosts[0][:host]).to eq('abcd.localhost')
+      expect(hosts[0][:protocol]).to eq('https')
+      expect(hosts[0][:user]).to eq('elastic')
+      expect(hosts[0][:password]).to eq('changeme')
+      expect(hosts[0][:port]).to eq(443)
+    end
+
+    it 'creates the correct full url' do
+      expect(
+        client.transport.__full_url(client.transport.hosts[0])
+      ).to eq('https://elastic:changeme@abcd.localhost:443')
+    end
+
+    context 'when a port is specified' do
+      let(:client) do
+        described_class.new(cloud_id: 'name:bG9jYWxob3N0JGFiY2QkZWZnaA==', user: 'elastic', password: 'changeme', port: 9250)
+      end
+
+      it 'sets the specified port along with the cloud credentials' do
+        expect(hosts[0][:host]).to eq('abcd.localhost')
+        expect(hosts[0][:protocol]).to eq('https')
+        expect(hosts[0][:user]).to eq('elastic')
+        expect(hosts[0][:password]).to eq('changeme')
+        expect(hosts[0][:port]).to eq(9250)
+      end
+
+      it 'creates the correct full url' do
+        expect(client.transport.__full_url(client.transport.hosts[0])).to eq('https://elastic:changeme@abcd.localhost:9250')
+      end
+    end
+
+    context 'when the cluster has alternate names' do
+      let(:client) do
+        described_class.new(
+          cloud_id: 'myCluster:bG9jYWxob3N0JGFiY2QkZWZnaA==',
+          user: 'elasticfantastic',
+          password: 'tobechanged'
+        )
+      end
+
+      let(:hosts) do
+        client.transport.hosts
+      end
+
+      it 'extracts the cloud credentials' do
+        expect(hosts[0][:host]).to eq('abcd.localhost')
+        expect(hosts[0][:protocol]).to eq('https')
+        expect(hosts[0][:user]).to eq('elasticfantastic')
+        expect(hosts[0][:password]).to eq('tobechanged')
+        expect(hosts[0][:port]).to eq(443)
+      end
+
+      it 'creates the correct full url' do
+        expect(
+          client.transport.__full_url(client.transport.hosts[0])
+        ).to eq('https://elasticfantastic:tobechanged@abcd.localhost:443')
+      end
+    end
+
+    context 'when decoded cloud id has a trailing dollar sign' do
+      let(:client) do
+        described_class.new(
+          cloud_id: 'a_cluster:bG9jYWxob3N0JGFiY2Qk',
+          user: 'elasticfantastic',
+          password: 'changeme'
+        )
+      end
+
+      let(:hosts) do
+        client.transport.hosts
+      end
+
+      it 'extracts the cloud credentials' do
+        expect(hosts[0][:host]).to eq('abcd.localhost')
+        expect(hosts[0][:protocol]).to eq('https')
+        expect(hosts[0][:user]).to eq('elasticfantastic')
+        expect(hosts[0][:password]).to eq('changeme')
+        expect(hosts[0][:port]).to eq(443)
+      end
+
+      it 'creates the correct full url' do
+        expect(
+          client.transport.__full_url(client.transport.hosts[0])
+        ).to eq('https://elasticfantastic:changeme@abcd.localhost:443')
+      end
+    end
+
+    context 'when the cloud host provides a port' do
+      let(:client) do
+        described_class.new(
+          cloud_id: 'name:ZWxhc3RpY19zZXJ2ZXI6OTI0MyRlbGFzdGljX2lk',
+          user: 'elastic',
+          password: 'changeme'
+        )
+      end
+
+      let(:hosts) do
+        client.transport.hosts
+      end
+
+      it 'creates the correct full url' do
+        expect(hosts[0][:host]).to eq('elastic_id.elastic_server')
+        expect(hosts[0][:protocol]).to eq('https')
+        expect(hosts[0][:user]).to eq('elastic')
+        expect(hosts[0][:password]).to eq('changeme')
+        expect(hosts[0][:port]).to eq(9243)
+      end
+    end
+
+    context 'when the cloud host provides a port and the port is also specified' do
+      let(:client) do
+        described_class.new(
+          cloud_id: 'name:ZWxhc3RpY19zZXJ2ZXI6OTI0MyRlbGFzdGljX2lk',
+          user: 'elastic',
+          password: 'changeme',
+          port: 9200
+        )
+      end
+
+      let(:hosts) do
+        client.transport.hosts
+      end
+
+      it 'creates the correct full url' do
+        expect(hosts[0][:host]).to eq('elastic_id.elastic_server')
+        expect(hosts[0][:protocol]).to eq('https')
+        expect(hosts[0][:user]).to eq('elastic')
+        expect(hosts[0][:password]).to eq('changeme')
+        expect(hosts[0][:port]).to eq(9243)
+      end
+    end
+  end
+end
diff --git a/elasticsearch/spec/unit/custom_transport_implementation_spec.rb b/elasticsearch/spec/unit/custom_transport_implementation_spec.rb
new file mode 100644
index 0000000000..9b004e3f54
--- /dev/null
+++ b/elasticsearch/spec/unit/custom_transport_implementation_spec.rb
@@ -0,0 +1,43 @@
+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. licenses this file to you under
+# the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+require 'spec_helper'
+
+describe Elasticsearch::Client do
+  context 'when using custom transport implementation' do
+    class MyTransport
+      include Elasticsearch::Transport::Transport::Base
+      def initialize(args); end
+    end
+    let(:client) { Elasticsearch::Client.new(transport_class: MyTransport) }
+    let(:arguments) { client.instance_variable_get('@transport').instance_variable_get('@arguments') }
+    let(:subject) do
+      arguments[:transport_options][:headers]
+    end
+
+    let(:meta_header) do
+      if jruby?
+        "es=#{meta_version},rb=#{RUBY_VERSION},t=#{Elasticsearch::Transport::VERSION},jv=#{ENV_JAVA['java.version']},jr=#{JRUBY_VERSION}"
+      else
+        "es=#{meta_version},rb=#{RUBY_VERSION},t=#{Elasticsearch::Transport::VERSION}"
+      end
+    end
+
+    it 'doesnae set any info about the implementation in the metaheader' do
+      expect(subject).to include('x-elastic-client-meta' => meta_header)
+    end
+  end
+end
diff --git a/elasticsearch/spec/unit/headers_spec.rb b/elasticsearch/spec/unit/headers_spec.rb
new file mode 100644
index 0000000000..75a7ba6375
--- /dev/null
+++ b/elasticsearch/spec/unit/headers_spec.rb
@@ -0,0 +1,53 @@
+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. licenses this file to you under
+# the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+require 'spec_helper'
+require 'ostruct'
+
+describe Elasticsearch::Client do
+  context 'when a header is set on an endpoint request' do
+    let(:client) { described_class.new }
+    let(:headers) { { 'user-agent' => 'my ruby app' } }
+
+    it 'performs the request with the header' do
+      allow(client).to receive(:perform_request) { OpenStruct.new(body: '') }
+      expect { client.search(headers: headers) }.not_to raise_error
+      expect(client).to have_received(:perform_request)
+                          .with('GET', '_search', {}, nil, headers)
+    end
+  end
+
+  context 'when a header is set on an endpoint request and on initialization' do
+    let!(:client) do
+      described_class.new(
+        host: 'http://localhost:9200',
+        transport_options: { headers: instance_headers }
+      )
+    end
+    let(:instance_headers) { { set_in_instantiation: 'header value' } }
+    let(:param_headers) {{'user-agent' => 'My Ruby Tests', 'set-on-method-call' => 'header value'}}
+
+    it 'performs the request with the header' do
+      expected_headers = client.transport.connections.connections.first.connection.headers.merge(param_headers)
+
+      expect_any_instance_of(Faraday::Connection)
+        .to receive(:run_request)
+              .with(:get, "http://localhost:9200/_search", nil, expected_headers) { OpenStruct.new(body: '')}
+
+      client.search(headers: param_headers)
+    end
+  end
+end
diff --git a/elasticsearch/spec/unit/opaque_id_spec.rb b/elasticsearch/spec/unit/opaque_id_spec.rb
new file mode 100644
index 0000000000..40678f70ba
--- /dev/null
+++ b/elasticsearch/spec/unit/opaque_id_spec.rb
@@ -0,0 +1,48 @@
+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. licenses this file to you under
+# the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+require 'spec_helper'
+require 'ostruct'
+
+describe Elasticsearch::Client do
+  let(:transport) { client.instance_variable_get('@transport') }
+  let(:client) { described_class.new }
+
+  before do
+    allow(transport).to receive(:perform_request) { OpenStruct.new(body: '') }
+  end
+
+  context 'when x-opaque-id is set' do
+    it 'uses x-opaque-id on a request' do
+      client.search(opaque_id: '12345')
+      expect(transport).to have_received(:perform_request)
+                             .with('GET', '_search', {}, nil, { 'X-Opaque-Id' => '12345' })
+    end
+  end
+
+  context 'when an x-opaque-id prefix is set on initialization' do
+    let(:prefix) { 'elastic_cloud' }
+    let(:client) do
+      described_class.new(opaque_id_prefix: prefix)
+    end
+
+    it 'uses x-opaque-id on a request' do
+      expect { client.search(opaque_id: '12345') }.not_to raise_error
+      expect(transport).to have_received(:perform_request)
+                             .with('GET', '_search', {}, nil, { 'X-Opaque-Id' => 'elastic_cloud12345' })
+    end
+  end
+end
diff --git a/elasticsearch/spec/unit/wrapper_gem_spec.rb b/elasticsearch/spec/unit/wrapper_gem_spec.rb
index 1f37132a56..5ad4382752 100644
--- a/elasticsearch/spec/unit/wrapper_gem_spec.rb
+++ b/elasticsearch/spec/unit/wrapper_gem_spec.rb
@@ -14,7 +14,8 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
-require 'elasticsearch'
+
+require 'spec_helper'
 
 describe 'Elasticsearch: wrapper gem' do
   it 'requires all neccessary subgems' do