FIX Read-Modify-Write issue with dynamic fields (#290)

* FIX Read-Modify-Write issue with dynamic fields

Ruby caching + queueing updates might cause some dynamic fields to not be updated.

* Small fix for true dynamic fields

* Add suite of tests for new settings page

* Treat nil values as deletions to keep the hash clean

* Test fix

app/controllers/settings/providers_controller.rb

@@ -28,6 +28,9 @@ class Settings::ProvidersController < ApplicationController
 
     updated_fields = []
 
+    # This hash will store only the updates for dynamic (non-declared) fields
+    dynamic_updates = {}
+
     # Perform all updates within a transaction for consistency
     Setting.transaction do
       provider_params.each do |param_key, param_value|
@@ -44,10 +47,42 @@ class Settings::ProvidersController < ApplicationController
           next
         end
 
-        # Set the value using dynamic hash-style access
-        Setting[field.setting_key] = value
+        key_str = field.setting_key.to_s
+
+        # Check if the setting is a declared field in setting.rb
+        # Use method_defined? to check if the setter actually exists on the singleton class,
+        # not just respond_to? which returns true for dynamic fields due to respond_to_missing?
+        if Setting.singleton_class.method_defined?("#{key_str}=")
+          # If it's a declared field (e.g., openai_model), set it directly.
+          # This is safe and uses the proper setter.
+          Setting.public_send("#{key_str}=", value)
+        else
+          # If it's a dynamic field, add it to our batch hash
+          # to avoid the Read-Modify-Write conflict.
+          dynamic_updates[key_str] = value
+        end
+
         updated_fields << param_key
       end
+
+      # Now, if we have any dynamic updates, apply them all at once
+      if dynamic_updates.any?
+        # 1. READ the current hash once
+        current_dynamic = Setting.dynamic_fields.dup
+
+        # 2. MODIFY by merging changes
+        # Treat nil values as deletions to keep the hash clean
+        dynamic_updates.each do |key, value|
+          if value.nil?
+            current_dynamic.delete(key)
+          else
+            current_dynamic[key] = value
+          end
+        end
+
+        # 3. WRITE the complete, merged hash back once
+        Setting.dynamic_fields = current_dynamic
+      end
     end
 
     if updated_fields.any?
@@ -61,6 +96,9 @@ class Settings::ProvidersController < ApplicationController
   rescue => error
     Rails.logger.error("Failed to update provider settings: #{error.message}")
     flash.now[:alert] = "Failed to update provider settings: #{error.message}"
+    # Set @provider_configurations so the view can render properly
+    Provider::Factory.ensure_adapters_loaded
+    @provider_configurations = Provider::ConfigurationRegistry.all
     render :show, status: :unprocessable_entity
   end