feat: add model based usage helper

enterprise/app/models/enterprise/account/plan_usage_and_limits.rb

@@ -21,6 +21,12 @@ module Enterprise::Account::PlanUsageAndLimits
     save
   end
 
+  def increment_response_usage_for_model(model)
+    credits = using_openai_hook_key? ? 1 : Llm::Models.credit_multiplier_for(model)
+    Rails.logger.info("[CAPTAIN] Incrementing response usage for account #{id} by #{credits} credits (model: #{model})")
+    increment_response_usage(credits: credits)
+  end
+
   def reset_response_usage
     custom_attributes[CAPTAIN_RESPONSES_USAGE] = 0
     save

spec/enterprise/models/enterprise/account/plan_usage_and_limits_spec.rb

@@ -28,4 +28,27 @@ RSpec.describe Enterprise::Account::PlanUsageAndLimits do
       expect(account.custom_attributes['captain_responses_usage']).to eq(2)
     end
   end
+
+  describe '#increment_response_usage_for_model' do
+    it 'increments by model credit multiplier when using system key' do
+      # gpt-5.1 has credit_multiplier of 2
+      account.increment_response_usage_for_model('gpt-5.1')
+      account.reload
+      expect(account.custom_attributes['captain_responses_usage']).to eq(2)
+    end
+
+    it 'increments by 1 when using hook key' do
+      create(:integrations_hook, account: account, app_id: 'openai', status: 'enabled', settings: { 'api_key' => 'user-key' })
+      # gpt-5.1 has credit_multiplier of 2, but hook key overrides to 1
+      account.increment_response_usage_for_model('gpt-5.1')
+      account.reload
+      expect(account.custom_attributes['captain_responses_usage']).to eq(1)
+    end
+
+    it 'defaults to 1 credit for unknown models' do
+      account.increment_response_usage_for_model('unknown-model')
+      account.reload
+      expect(account.custom_attributes['captain_responses_usage']).to eq(1)
+    end
+  end
 end