diff --git a/.buildkite/pipeline.yml b/.buildkite/pipeline.yml
index cf0cc0171b..bc0960e180 100644
--- a/.buildkite/pipeline.yml
+++ b/.buildkite/pipeline.yml
@@ -5,7 +5,7 @@ steps:
     env:
       RUBY_VERSION: "{{ matrix.ruby }}"
       TEST_SUITE: "{{ matrix.suite }}"
-      STACK_VERSION: 8.18.4-SNAPSHOT
+      STACK_VERSION: 8.18.6-SNAPSHOT
       TRANSPORT_VERSION: "{{ matrix.transport }}"
       RUBY_SOURCE: "{{ matrix.ruby_source }}"
       QUIET: false
@@ -62,7 +62,7 @@ steps:
       provider: "gcp"
     env:
       RUBY_VERSION: "3.4"
-      STACK_VERSION: 8.18.4-SNAPSHOT
+      STACK_VERSION: 8.18.6-SNAPSHOT
       ES_YAML_TESTS_BRANCH: "8.18"
       TRANSPORT_VERSION: "8.3"
       RUBY_SOURCE: "ruby"
diff --git a/.github/workflows/8.18.yml b/.github/workflows/8.18.yml
index 40ccce6adf..9e97a9179a 100644
--- a/.github/workflows/8.18.yml
+++ b/.github/workflows/8.18.yml
@@ -26,7 +26,7 @@ jobs:
         sudo sysctl -w vm.max_map_count=262144
     - uses: elastic/elastic-github-actions/elasticsearch@master
       with:
-        stack-version: 8.18.4-SNAPSHOT
+        stack-version: 8.18.6-SNAPSHOT
         security-enabled: false
     - uses: ruby/setup-ruby@v1
       with:
@@ -40,4 +40,4 @@ jobs:
     - name: elasticsearch
       run: cd elasticsearch && bundle exec rake test:all
     - name: elasticsearch-api
-      run: rake es:download_artifacts[8.18.4-SNAPSHOT] && cd elasticsearch-api && bundle exec rake test:spec test:platinum:unit
+      run: rake es:download_artifacts[8.18.6-SNAPSHOT] && cd elasticsearch-api && bundle exec rake test:spec test:platinum:unit
diff --git a/.github/workflows/otel.yml b/.github/workflows/otel.yml
index 53365c4159..b022a8b1e5 100644
--- a/.github/workflows/otel.yml
+++ b/.github/workflows/otel.yml
@@ -28,7 +28,7 @@ jobs:
           sudo sysctl -w vm.max_map_count=262144
       - uses: elastic/elastic-github-actions/elasticsearch@master
         with:
-          stack-version: 8.18.4-SNAPSHOT
+          stack-version: 8.18.6-SNAPSHOT
           security-enabled: false
       - uses: ruby/setup-ruby@v1
         with:
@@ -42,4 +42,4 @@ jobs:
       - name: elasticsearch
         run: cd elasticsearch && bundle exec rake test:all
       - name: elasticsearch-api
-        run: rake es:download_artifacts[8.18.4-SNAPSHOT] && cd elasticsearch-api && bundle exec rake test:spec test:platinum:unit
+        run: rake es:download_artifacts[8.18.6-SNAPSHOT] && cd elasticsearch-api && bundle exec rake test:spec test:platinum:unit
diff --git a/elasticsearch-api/lib/elasticsearch/api/actions/inference/put_custom.rb b/elasticsearch-api/lib/elasticsearch/api/actions/inference/put_custom.rb
new file mode 100644
index 0000000000..51f3435223
--- /dev/null
+++ b/elasticsearch-api/lib/elasticsearch/api/actions/inference/put_custom.rb
@@ -0,0 +1,65 @@
+# 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.
+#
+# Auto generated from build hash f284cc16f4d4b4289bc679aa1529bb504190fe80
+# @see https://github.com/elastic/elasticsearch/tree/main/rest-api-spec
+#
+module Elasticsearch
+  module API
+    module Inference
+      module Actions
+        # Configure a custom inference endpoint
+        #
+        # @option arguments [String] :task_type The task type
+        # @option arguments [String] :custom_inference_id The inference Id
+        # @option arguments [Hash] :headers Custom HTTP headers
+        # @option arguments [Hash] :body The inference endpoint's task and service settings
+        #
+        # @see https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-inference-put-custom
+        #
+        def put_custom(arguments = {})
+          request_opts = { endpoint: arguments[:endpoint] || 'inference.put_custom' }
+
+          defined_params = %i[task_type custom_inference_id].each_with_object({}) do |variable, set_variables|
+            set_variables[variable] = arguments[variable] if arguments.key?(variable)
+          end
+          request_opts[:defined_params] = defined_params unless defined_params.empty?
+
+          raise ArgumentError, "Required argument 'task_type' missing" unless arguments[:task_type]
+          raise ArgumentError, "Required argument 'custom_inference_id' missing" unless arguments[:custom_inference_id]
+
+          arguments = arguments.clone
+          headers = arguments.delete(:headers) || {}
+
+          body = arguments.delete(:body)
+
+          _task_type = arguments.delete(:task_type)
+
+          _custom_inference_id = arguments.delete(:custom_inference_id)
+
+          method = Elasticsearch::API::HTTP_PUT
+          path   = "_inference/#{Utils.__listify(_task_type)}/#{Utils.__listify(_custom_inference_id)}"
+          params = {}
+
+          Elasticsearch::API::Response.new(
+            perform_request(method, path, params, body, headers, request_opts)
+          )
+        end
+      end
+    end
+  end
+end
diff --git a/elasticsearch-api/lib/elasticsearch/api/actions/transform/set_upgrade_mode.rb b/elasticsearch-api/lib/elasticsearch/api/actions/transform/set_upgrade_mode.rb
new file mode 100644
index 0000000000..aa808b4ac1
--- /dev/null
+++ b/elasticsearch-api/lib/elasticsearch/api/actions/transform/set_upgrade_mode.rb
@@ -0,0 +1,52 @@
+# 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.
+#
+# Auto generated from build hash f284cc16f4d4b4289bc679aa1529bb504190fe80
+# @see https://github.com/elastic/elasticsearch/tree/main/rest-api-spec
+#
+module Elasticsearch
+  module API
+    module Transform
+      module Actions
+        # Sets a cluster wide upgrade_mode setting that prepares transform indices for an upgrade.
+        #
+        # @option arguments [Boolean] :enabled Whether to enable upgrade_mode Transform setting or not. Defaults to false.
+        # @option arguments [Time] :timeout Controls the time to wait before action times out. Defaults to 30 seconds
+        # @option arguments [Hash] :headers Custom HTTP headers
+        #
+        # @see https://www.elastic.co/guide/en/elasticsearch/reference/8.18/transform-set-upgrade-mode.html
+        #
+        def set_upgrade_mode(arguments = {})
+          request_opts = { endpoint: arguments[:endpoint] || 'transform.set_upgrade_mode' }
+
+          arguments = arguments.clone
+          headers = arguments.delete(:headers) || {}
+
+          body   = nil
+
+          method = Elasticsearch::API::HTTP_POST
+          path   = '_transform/set_upgrade_mode'
+          params = Utils.process_params(arguments)
+
+          Elasticsearch::API::Response.new(
+            perform_request(method, path, params, body, headers, request_opts)
+          )
+        end
+      end
+    end
+  end
+end
diff --git a/elasticsearch-api/spec/elasticsearch/api/actions/inference/put_custom_spec.rb b/elasticsearch-api/spec/elasticsearch/api/actions/inference/put_custom_spec.rb
new file mode 100644
index 0000000000..a409676f1b
--- /dev/null
+++ b/elasticsearch-api/spec/elasticsearch/api/actions/inference/put_custom_spec.rb
@@ -0,0 +1,36 @@
+# 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 'client#inference.put_custom' do
+  let(:expected_args) do
+    [
+      'PUT',
+      '_inference/foo/baz',
+      {},
+      nil,
+      {},
+      { defined_params: { custom_inference_id: 'baz', task_type: 'foo' },
+        endpoint: 'inference.put_custom' }
+    ]
+  end
+
+  it 'performs the request' do
+    expect(client_double.inference.put_custom(task_type: 'foo', custom_inference_id: 'baz')).to be_a Elasticsearch::API::Response
+  end
+end
diff --git a/elasticsearch-api/spec/elasticsearch/api/actions/transform/set_upgrade_mode_spec.rb b/elasticsearch-api/spec/elasticsearch/api/actions/transform/set_upgrade_mode_spec.rb
new file mode 100644
index 0000000000..9dd1b158c1
--- /dev/null
+++ b/elasticsearch-api/spec/elasticsearch/api/actions/transform/set_upgrade_mode_spec.rb
@@ -0,0 +1,35 @@
+# 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 'client.transform#set_upgrade_mode' do
+  let(:expected_args) do
+    [
+      'POST',
+      '_transform/set_upgrade_mode',
+      {},
+      nil,
+      {},
+      { endpoint: 'transform.set_upgrade_mode' }
+    ]
+  end
+
+  it 'performs the request' do
+    expect(client_double.transform.set_upgrade_mode).to be_a Elasticsearch::API::Response
+  end
+end