fix: atomic update of captain usage under load

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

@@ -15,10 +15,18 @@ module Enterprise::Account::PlanUsageAndLimits
     }
   end
 
+  # Use atomic SQL update to prevent race condition when multiple jobs
+  # increment concurrently. The previous read-modify-write pattern caused
+  # lost updates under high concurrency
+  # Skipping validations is safe: no validations on custom_attributes, no dependent callbacks.
   def increment_response_usage
-    current_usage = custom_attributes[CAPTAIN_RESPONSES_USAGE].to_i || 0
-    custom_attributes[CAPTAIN_RESPONSES_USAGE] = current_usage + 1
-    save
+    self.class.where(id: id).update_all( # rubocop:disable Rails/SkipsModelValidations
+      "custom_attributes = jsonb_set(
+        custom_attributes,
+        '{#{CAPTAIN_RESPONSES_USAGE}}',
+        (COALESCE((custom_attributes->>'#{CAPTAIN_RESPONSES_USAGE}')::int, 0) + 1)::text::jsonb
+      )"
+    )
   end
 
   def reset_response_usage

spec/enterprise/models/account_spec.rb

@@ -70,6 +70,7 @@ RSpec.describe Account, type: :model do
       ## Responses
       it 'incrementing responses updates usage_limits' do
         account.increment_response_usage
+        account.reload
 
         responses_limits = account.usage_limits[:captain][:responses]