Update QuestionRephraser to always rephrase post Sonnet 4.0

We want to update the QuestionRephraser to always rephrase the question,
even if it is the users first question.

This updates the QuestionRephraser to do this for all models except
Sonnet 4.0 as we don't have updated prompts for that model so it should
continue to use the existing implementation.

We've also got a slight change due to always rephrasing, in that we need
two user prompts. One for when there is history, and one for when there
isn't.

I've added some basic tests to check that the correct system prompt is
being used in both situations.

Author: davidgisbey

lib/answer_composition/pipeline/question_rephraser.rb

@@ -18,11 +18,11 @@ def initialize(context)
       end
 
       def call
-        return if message_records.blank?
+        return if message_records.blank? && model_name == :claude_sonnet_4_0
 
         start_time = Clock.monotonic_time
         response = anthropic_bedrock_client.messages.create(
-          system: [{ type: "text", text: config[:system_prompt] }],
+          system: [{ type: "text", text: system_prompt }],
           model: model_id,
           messages:,
           **inference_config,
@@ -78,10 +78,25 @@ def inference_config
         }
       end
 
+      def system_prompt
+        return config[:system_prompt] if model_name == :claude_sonnet_4_0
+
+        config[:system_prompt_always_rephrase]
+      end
+
       def user_prompt
-        config[:user_prompt]
-          .sub("{question}", question_message)
-          .sub("{message_history}", message_history)
+        if model_name == :claude_sonnet_4_0
+          return config[:user_prompt].sub("{question}", question_message)
+                                     .sub("{message_history}", message_history)
+
+        end
+
+        if message_records.present?
+          config[:user_prompt_with_history].sub("{question}", question_message)
+                                           .sub("{message_history}", message_history)
+        else
+          config[:user_prompt_without_history].sub("{question}", question_message)
+        end
       end
 
       def messages

spec/lib/answer_composition/pipeline/question_rephraser_spec.rb

@@ -30,96 +30,100 @@
     end
   end
 
-  context "when the question is the beginning of the conversation" do
-    let(:context) { build(:answer_pipeline_context) }
-
-    it "returns nil" do
-      expect(described_class.call(context)).to be_nil
-    end
+  it "includes the current question in the user prompt" do
+    described_class.call(context)
+    expect(stub).to have_been_requested
   end
 
-  context "when all other recent answers have statuses in Answer::STATUSES_EXCLUDED_FROM_REPHRASING" do
-    it "returns nil" do
-      conversation = create(:conversation)
-      create(:question, conversation:)
-      Answer::STATUSES_EXCLUDED_FROM_REPHRASING.sample(4) do |status|
-        question = create(:question, conversation:)
-        create(:answer, question:, status:)
-      end
-      latest_question = create(:question, conversation:)
-      context = build(:answer_pipeline_context, question: latest_question)
+  it "includes the message_history in the user prompt" do
+    message_history = <<~HISTORY.strip
+      user:
+      """
+      How do I pay my tax
+      """
+      assistant:
+      """
+      What type of tax
+      """
+      user:
+      """
+      What types are there
+      """
+      assistant:
+      """
+      Self-assessment, PAYE, Corporation tax
+      """
+    HISTORY
 
-      expect(described_class.call(context)).to be_nil
-    end
+    anthropic_request = stub_claude_question_rephrasing(
+      Regexp.new(message_history),
+      rephrased,
+    )
+
+    described_class.call(context)
+
+    expect(anthropic_request).to have_been_made
   end
 
-  context "when the question is part of an ongoing chat" do
-    it "includes the current question in the user prompt" do
-      described_class.call(context)
-      expect(stub).to have_been_requested
-    end
+  it "updates the context's question_message with the rephrased question" do
+    described_class.call(context)
+    expect(context.question_message).to eq(rephrased)
+  end
 
-    it "includes the message_history in the user prompt" do
-      message_history = <<~HISTORY.strip
-        user:
-        """
-        How do I pay my tax
-        """
-        assistant:
-        """
-        What type of tax
-        """
-        user:
-        """
-        What types are there
-        """
-        assistant:
-        """
-        Self-assessment, PAYE, Corporation tax
-        """
-      HISTORY
+  it "assigns metrics to the answer" do
+    allow(Clock).to receive(:monotonic_time).and_return(100.0, 101.5)
 
-      anthropic_request = stub_claude_question_rephrasing(
-        Regexp.new(message_history),
-        rephrased,
-      )
+    described_class.call(context)
 
-      described_class.call(context)
+    expect(context.answer.metrics["question_rephrasing"])
+      .to eq({
+        duration: 1.5,
+        llm_prompt_tokens: 10,
+        llm_completion_tokens: 20,
+        llm_cached_tokens: nil,
+        model: BedrockModels.model_id(described_class::DEFAULT_MODEL),
+      })
+  end
 
-      expect(anthropic_request).to have_been_made
-    end
+  it "assigns the llm response to the answer" do
+    described_class.call(context)
 
-    it "updates the context's question_message with the rephrased question" do
-      described_class.call(context)
-      expect(context.question_message).to eq(rephrased)
-    end
+    expected_llm_response = claude_messages_response(
+      content: [claude_messages_text_block(rephrased)],
+      usage: claude_messages_usage_block(input_tokens: 10, output_tokens: 20),
+      bedrock_model: described_class::DEFAULT_MODEL,
+    ).to_h
 
-    it "assigns metrics to the answer" do
-      allow(Clock).to receive(:monotonic_time).and_return(100.0, 101.5)
+    expect(context.answer.llm_responses["question_rephrasing"])
+      .to eq(expected_llm_response)
+  end
 
+  context "when the question is the first in the conversation" do
+    let(:question) { create(:question) }
+    let(:context) { build(:answer_pipeline_context, question:) }
+    let!(:stub) { stub_claude_question_rephrasing(question.message, rephrased) }
+
+    it "calls the llm and rephrases the question" do
       described_class.call(context)
 
-      expect(context.answer.metrics["question_rephrasing"])
-        .to eq({
-          duration: 1.5,
-          llm_prompt_tokens: 10,
-          llm_completion_tokens: 20,
-          llm_cached_tokens: nil,
-          model: BedrockModels.model_id(described_class::DEFAULT_MODEL),
-        })
+      expect(stub).to have_been_requested
+      expect(context.question_message).to eq(rephrased)
     end
 
-    it "assigns the llm response to the answer" do
-      described_class.call(context)
+    it "uses the user_prompt_without_history prompt" do
+      expected_prompt = AnswerComposition::Pipeline::Prompts.config(
+        :question_rephraser, described_class::DEFAULT_MODEL
+      )[:user_prompt_without_history]
+      .sub("{question}", question.message)
+
+      anthropic_request = stub_claude_question_rephrasing(
+        expected_prompt,
+        rephrased,
+      )
 
-      expected_llm_response = claude_messages_response(
-        content: [claude_messages_text_block(rephrased)],
-        usage: claude_messages_usage_block(input_tokens: 10, output_tokens: 20),
-        bedrock_model: described_class::DEFAULT_MODEL,
-      ).to_h
+      described_class.call(context)
 
-      expect(context.answer.llm_responses["question_rephrasing"])
-        .to eq(expected_llm_response)
+      expect(anthropic_request).to have_been_made
     end
   end
 
@@ -225,4 +229,60 @@
       expect(anthropic_request).to have_been_made
     end
   end
+
+  context "when the model is claude_sonnet_4_0" do
+    let!(:stub) do
+      stub_claude_question_rephrasing(
+        question.message, rephrased, chat_options: { bedrock_model: :claude_sonnet_4_0 }
+      )
+    end
+
+    before { stub_const("#{described_class}::DEFAULT_MODEL", :claude_sonnet_4_0) }
+
+    it "uses the system prompt configured for claude_sonnet_4_0" do
+      allow(AnswerComposition::Pipeline::Prompts.config(:question_rephraser, :claude_sonnet_4_0))
+        .to receive(:[]).and_call_original
+
+      described_class.call(context)
+
+      expect(AnswerComposition::Pipeline::Prompts.config(:question_rephraser, :claude_sonnet_4_0))
+        .to have_received(:[]).with(:system_prompt)
+    end
+
+    it "calls the llm when there is message history" do
+      described_class.call(context)
+
+      expect(stub).to have_been_requested
+      expect(context.question_message).to eq(rephrased)
+    end
+
+    context "and all other recent answers have statuses in Answer::STATUSES_EXCLUDED_FROM_REPHRASING" do
+      it "returns nil" do
+        conversation = create(:conversation)
+        create(:question, conversation:)
+        Answer::STATUSES_EXCLUDED_FROM_REPHRASING.sample(4) do |status|
+          question = create(:question, conversation:)
+          create(:answer, question:, status:)
+        end
+        latest_question = create(:question, conversation:)
+        context = build(:answer_pipeline_context, question: latest_question)
+
+        expect(described_class.call(context)).to be_nil
+        expect(stub).not_to have_been_requested
+      end
+    end
+
+    context "and there is no message history" do
+      let(:conversation) { create(:conversation) }
+      let(:question) { create(:question, conversation:) }
+      let(:context) { build(:answer_pipeline_context, question:) }
+
+      it "returns nil" do
+        result = described_class.call(context)
+
+        expect(stub).not_to have_been_requested
+        expect(result).to be_nil
+      end
+    end
+  end
 end

spec/support/system_spec_helpers.rb

@@ -35,18 +35,13 @@ def given_i_am_an_admin_with_the_settings_permission
 
   def stubs_for_mock_answer(question,
                             answer,
-                            rephrase_question: false,
                             sources_used: [],
                             create_content_chunk: true)
     stub_claude_jailbreak_guardrails(question)
+    rephrased_question = "Rephrased #{question}"
+    stub_claude_question_rephrasing(question, rephrased_question)
 
-    if rephrase_question
-      rephrased_question = "Rephrased #{question}"
-
-      stub_claude_question_rephrasing(question, rephrased_question)
-
-      question = rephrased_question
-    end
+    question = rephrased_question
 
     stub_bedrock_titan_embedding(question)
 

spec/system/conversation_js_features_spec.rb

@@ -182,7 +182,6 @@ def when_the_second_answer_is_generated
 
     stubs_for_mock_answer(@second_question,
                           @second_answer,
-                          rephrase_question: true,
                           sources_used: %w[link_1],
                           create_content_chunk: false)
 

spec/system/conversation_with_claude_structured_answer_spec.rb

@@ -66,7 +66,6 @@ def when_the_second_answer_is_generated
 
     stubs_for_mock_answer(@second_question,
                           @second_answer,
-                          rephrase_question: true,
                           sources_used: %w[link_1],
                           create_content_chunk: false)