diff --git a/lib/ai_helper/assistant.rb b/lib/ai_helper/assistant.rb
index 8081e9cd..550a3362 100644
--- a/lib/ai_helper/assistant.rb
+++ b/lib/ai_helper/assistant.rb
@@ -320,6 +320,13 @@ module DiscourseAi
         if model_id.present?
           LlmModel.find_by(id: model_id)
         else
+          last_model_id = LlmModel.last&.id
+
+          # SiteSetting.ai_default_llm_model shouldn't be empty, but if it is, we set it to the last model.
+          if last_model_id.present? && SiteSetting.ai_default_llm_model.empty?
+            SiteSetting.set_and_log("ai_default_llm_model", "custom:#{last_model_id}", Discourse.system_user) # Remove legacy custom provider.
+          end
+
           LlmModel.last
         end
       end
diff --git a/lib/embeddings/semantic_search.rb b/lib/embeddings/semantic_search.rb
index 3ed27920..a1c0b01e 100644
--- a/lib/embeddings/semantic_search.rb
+++ b/lib/embeddings/semantic_search.rb
@@ -215,9 +215,19 @@ module DiscourseAi
         model_id =
           persona_klass.default_llm_id || SiteSetting.ai_default_llm_model&.split(":")&.last # Remove legacy custom provider.
 
-        return if model_id.blank?
+        if model_id.present?
+          LlmModel.find_by(id: model_id)
+        else
+          last_model_id = LlmModel.last&.id
+
+          # SiteSetting.ai_default_llm_model shouldn't be empty, but if it is, we set it to the last model.
+          if last_model_id.present? && SiteSetting.ai_default_llm_model.empty?
+            SiteSetting.set_and_log("ai_default_llm_model", "custom:#{last_model_id}", Discourse.system_user) # Remove legacy custom provider.
+          end
+
+          LlmModel.last
+        end
 
-        LlmModel.find_by(id: model_id)
       end
 
       private
diff --git a/lib/summarization.rb b/lib/summarization.rb
index f530b89b..e4706cbd 100644
--- a/lib/summarization.rb
+++ b/lib/summarization.rb
@@ -62,6 +62,13 @@ module DiscourseAi
         if model_id.present?
           LlmModel.find_by(id: model_id)
         else
+          last_model_id = LlmModel.last&.id
+
+          # SiteSetting.ai_default_llm_model shouldn't be empty, but if it is, we set it to the last model.
+          if last_model_id.present? && SiteSetting.ai_default_llm_model.empty?
+            SiteSetting.set_and_log("ai_default_llm_model", "custom:#{last_model_id}", Discourse.system_user) # Remove legacy custom provider.
+          end
+
           LlmModel.last
         end
       end