diff --git a/enterprise/lib/captain/conversation_completion_service.rb b/enterprise/lib/captain/conversation_completion_service.rb
index 6ac45421c..e9cdc8937 100644
--- a/enterprise/lib/captain/conversation_completion_service.rb
+++ b/enterprise/lib/captain/conversation_completion_service.rb
@@ -56,6 +56,14 @@ class Captain::ConversationCompletionService < Captain::BaseTaskService
     { complete: false, reason: reason }
   end
 
+  # Prefer the system API key over the account's OpenAI hook key.
+  # This is an internal operational evaluation, not a customer-triggered feature,
+  # so it should not consume the customer's OpenAI credits on hosted platforms.
+  # Falls back to the account hook for self-hosted deployments without a system key.
+  def api_key
+    @api_key ||= system_api_key.presence || openai_hook&.settings&.dig('api_key')
+  end
+
   def event_name
     'captain.conversation_completion'
   end
diff --git a/spec/enterprise/lib/captain/conversation_completion_service_spec.rb b/spec/enterprise/lib/captain/conversation_completion_service_spec.rb
index 51d7fa807..58b2b2ce6 100644
--- a/spec/enterprise/lib/captain/conversation_completion_service_spec.rb
+++ b/spec/enterprise/lib/captain/conversation_completion_service_spec.rb
@@ -126,6 +126,33 @@ RSpec.describe Captain::ConversationCompletionService do
       end
     end
 
+    context 'when account has its own OpenAI hook' do
+      before do
+        create(:message, conversation: conversation, message_type: :incoming, content: 'Hello')
+        create(:integrations_hook, :openai, account: account, settings: { 'api_key' => 'customer-own-key' })
+      end
+
+      it 'uses the system API key instead of the account hook key' do
+        expect(Llm::Config).to receive(:with_api_key).with('test-key', api_base: anything).and_yield(mock_context)
+        allow(mock_chat).to receive(:ask).and_return(
+          instance_double(RubyLLM::Message, content: { 'complete' => true, 'reason' => 'Done' }, input_tokens: 10, output_tokens: 5)
+        )
+
+        service.perform
+      end
+
+      it 'falls back to the account hook key when no system key exists' do
+        InstallationConfig.find_by(name: 'CAPTAIN_OPEN_AI_API_KEY').update!(value: nil)
+
+        expect(Llm::Config).to receive(:with_api_key).with('customer-own-key', api_base: anything).and_yield(mock_context)
+        allow(mock_chat).to receive(:ask).and_return(
+          instance_double(RubyLLM::Message, content: { 'complete' => true, 'reason' => 'Done' }, input_tokens: 10, output_tokens: 5)
+        )
+
+        service.perform
+      end
+    end
+
     context 'when customer quota is exhausted' do
       let(:mock_response) do
         instance_double(