diff --git a/controllers/client.rb b/controllers/client.rb
index d43fe13..11a99e0 100644
--- a/controllers/client.rb
+++ b/controllers/client.rb
@@ -17,6 +17,8 @@ class Client
 
       DEFAULT_SERVICE_VERSION = 'v1'
 
+      attr_reader :base_address
+
       def initialize(config)
         @service = config[:credentials][:service]
 
@@ -54,12 +56,12 @@ def initialize(config)
 
         @service_version = config.dig(:credentials, :version) || DEFAULT_SERVICE_VERSION
 
-        @base_address = case @service
-                        when 'vertex-ai-api'
-                          "https://#{config[:credentials][:region]}-aiplatform.googleapis.com/#{@service_version}/projects/#{@project_id}/locations/#{config[:credentials][:region]}"
-                        when 'generative-language-api'
-                          "https://generativelanguage.googleapis.com/#{@service_version}"
-                        end
+        @base_address = config[:credentials][:base_address] || case @service
+                                                               when 'vertex-ai-api'
+                                                                 "https://#{config[:credentials][:region]}-aiplatform.googleapis.com/#{@service_version}/projects/#{@project_id}/locations/#{config[:credentials][:region]}"
+                                                               when 'generative-language-api'
+                                                                 "https://generativelanguage.googleapis.com/#{@service_version}"
+                                                               end
 
         @model_address = case @service
                          when 'vertex-ai-api'
@@ -81,6 +83,8 @@ def initialize(config)
                            else
                              {}
                            end
+
+        @custom_headers = config.dig(:options, :headers) || {}
       end
 
       def avoid_conflicting_credentials!(credentials)
@@ -179,7 +183,7 @@ def request(path, payload, server_sent_events: nil, request_method: 'POST', &cal
         method_to_call = request_method.to_s.strip.downcase.to_sym
 
         response = Faraday.new(request: @request_options) do |faraday|
-          faraday.adapter @faraday_adapter
+          faraday.adapter(*@faraday_adapter)
           faraday.response :raise_error
         end.send(method_to_call) do |request|
           request.url url
@@ -187,6 +191,7 @@ def request(path, payload, server_sent_events: nil, request_method: 'POST', &cal
           if @authentication == :service_account || @authentication == :default_credentials
             request.headers['Authorization'] = "Bearer #{@authorizer.fetch_access_token!['access_token']}"
           end
+          @custom_headers.each { |key, value| request.headers[key] = value }
 
           request.body = payload.to_json unless payload.nil?
 
diff --git a/spec/controllers/client_spec.rb b/spec/controllers/client_spec.rb
index 6c7df9c..6cf03aa 100644
--- a/spec/controllers/client_spec.rb
+++ b/spec/controllers/client_spec.rb
@@ -45,4 +45,64 @@
       "You must choose either 'file_contents', or 'file_path'."
     )
   end
+
+  describe 'custom base address' do
+    it 'uses the custom base address when provided' do
+      custom_base_address = 'https://custom-gemini-api.example.com/v1'
+      client = described_class.new(
+        credentials: {
+          service: 'vertex-ai-api',
+          region: 'us-east4',
+          base_address: custom_base_address,
+          api_key: 'key'
+        },
+        options: { model: 'gemini-pro' }
+      )
+
+      expect(client.base_address).to eq(custom_base_address)
+    end
+
+    it 'uses the default base address when not provided' do
+      client = described_class.new(
+        credentials: {
+          service: 'vertex-ai-api',
+          region: 'us-east4',
+          api_key: 'key'
+        },
+        options: { model: 'gemini-pro' }
+      )
+
+      expect(client.base_address).to include('aiplatform.googleapis.com')
+    end
+  end
+
+  describe 'custom headers' do
+    let(:stubs) { Faraday::Adapter::Test::Stubs.new }
+    let(:faraday_test_adapter) { :test }
+
+    it 'sends custom headers with the request' do
+      custom_headers = { 'X-Custom-Header' => 'CustomValue' }
+
+      stubs.post(/.*/) do |env|
+        expect(env.request_headers).to include(custom_headers)
+        [200, {}, '{}']
+      end
+
+      client = described_class.new(
+        credentials: {
+          service: 'vertex-ai-api',
+          region: 'us-east4',
+          api_key: 'key'
+        },
+        options: {
+          model: 'gemini-pro',
+          headers: custom_headers,
+          connection: { adapter: [:test, stubs] }
+        }
+      )
+
+      client.predict({ content: 'Test' })
+      stubs.verify_stubbed_calls
+    end
+  end
 end