Appends the system parameter to Anthropic chat if instructions are sp…

…ecified, regardless of whether or not tools are being used. (#695)

Co-authored-by: Andrei Bondarev <andrei@sourcelabs.io>

lib/langchain/assistants/assistant.rb

@@ -258,21 +258,25 @@ def chat_with_llm
 
       params = {messages: thread.array_of_message_hashes}
 
-      if tools.any?
-        if llm.is_a?(Langchain::LLM::OpenAI)
+      if llm.is_a?(Langchain::LLM::OpenAI)
+        if tools.any?
           params[:tools] = tools.map(&:to_openai_tools).flatten
           params[:tool_choice] = "auto"
-        elsif llm.is_a?(Langchain::LLM::Anthropic)
+        end
+      elsif llm.is_a?(Langchain::LLM::Anthropic)
+        if tools.any?
           params[:tools] = tools.map(&:to_anthropic_tools).flatten
-          params[:system] = instructions if instructions
           params[:tool_choice] = {type: "auto"}
-        elsif [Langchain::LLM::GoogleGemini, Langchain::LLM::GoogleVertexAI].include?(llm.class)
+        end
+        params[:system] = instructions if instructions
+      elsif [Langchain::LLM::GoogleGemini, Langchain::LLM::GoogleVertexAI].include?(llm.class)
+        if tools.any?
           params[:tools] = tools.map(&:to_google_gemini_tools).flatten
           params[:system] = instructions if instructions
           params[:tool_choice] = "auto"
         end
-        # TODO: Not sure that tool_choice should always be "auto"; Maybe we can let the user toggle it.
       end
+      # TODO: Not sure that tool_choice should always be "auto"; Maybe we can let the user toggle it.
 
       llm.chat(**params)
     end

spec/langchain/assistants/assistant_spec.rb

@@ -437,6 +437,27 @@
         }
       end
 
+      context "when not using tools" do
+        subject {
+          described_class.new(
+            llm: llm,
+            thread: thread,
+            instructions: instructions
+          )
+        }
+
+        it "adds a system param to chat when instructions are given" do
+          expect(subject.llm).to receive(:chat)
+            .with(
+              hash_including(
+                system: instructions
+              )
+            ).and_return(Langchain::LLM::AnthropicResponse.new(raw_anthropic_response))
+          subject.add_message content: "Please calculate 2+2"
+          subject.run
+        end
+      end
+
       context "when auto_tool_execution is false" do
         before do
           allow(subject.llm).to receive(:chat)
@@ -456,6 +477,17 @@
           expect(subject.thread.messages.last.role).to eq("assistant")
           expect(subject.thread.messages.last.tool_calls).to eq([raw_anthropic_response["content"].first])
         end
+
+        it "adds a system param to chat when instructions are given" do
+          expect(subject.llm).to receive(:chat)
+            .with(
+              hash_including(
+                system: instructions
+              )
+            ).and_return(Langchain::LLM::AnthropicResponse.new(raw_anthropic_response))
+          subject.add_message content: "Please calculate 2+2"
+          subject.run
+        end
       end
 
       context "when auto_tool_execution is true" do