Add inference happy path

Uses the OpenAI client SDK to call a real inference service.

The values in .env.example work for a local Ollama instance.

Author: mwtrew

.env.example

@@ -70,3 +70,8 @@ SCRATCH_ASSET_IMPORT_BASE_URL=https://example.com/assets/
 
 HOSTNAME=localhost
 LEARNER_EXPERIENCE_TESTS_DISPATCH_TOKEN=changeme
+
+# Friendly error messages
+FEM_INFERENCE_API_URL='http://localhost:11434/v1/'
+FEM_INFERENCE_API_KEY=''
+BYPASS_FEM_INFERENCE=true

Gemfile

@@ -87,3 +87,5 @@ group :test do
   gem 'webdrivers'
   gem 'webmock'
 end
+
+gem 'openai', '~> 0.115.0'

Gemfile.lock

@@ -324,6 +324,9 @@ GEM
       stringio
       time
       uri
+    openai (0.115.0)
+      connection_pool (>= 2.2.3)
+      logger
     paper_trail (17.0.0)
       activerecord (>= 7.1)
       request_store (~> 1.4)
@@ -603,6 +606,7 @@ DEPENDENCIES
   omniauth-rails_csrf_protection (~> 2.0.1)
   omniauth-rpi!
   open-uri
+  openai (~> 0.115.0)
   paper_trail
   pg (~> 1.7)
   postmark-rails

lib/friendly_error_messages_inference_client.rb

@@ -1,7 +1,22 @@
 # frozen_string_literal: true
 
 class FriendlyErrorMessagesInferenceClient
-  def get_message(_message, _trace, _runtime, _code)
-    'This is a placeholder friendly error message.'
+  def initialize
+    @client = OpenAI::Client.new(
+      base_url: ENV.fetch('FEM_INFERENCE_API_URL'),
+      api_key: ENV.fetch('FEM_INFERENCE_API_KEY')
+    )
+  end
+
+  def get_message(message, trace, runtime, code)
+    return 'This is a placeholder friendly error message.' if ENV.fetch('BYPASS_FEM_INFERENCE', nil) == 'true'
+
+    @client.responses.create(model: 'qwen3.5:9b', input:
+    JSON.dump({
+                message:,
+                trace:,
+                runtime:,
+                code:
+              })).output_text
   end
 end

spec/lib/friendly_error_messages_inference_client_spec.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe FriendlyErrorMessagesInferenceClient do
+  subject(:client) { described_class.new }
+
+  let(:openai_client) { instance_double(OpenAI::Client) }
+
+  context 'when BYPASS_FEM_INFERENCE is false' do
+    around do |example|
+      ClimateControl.modify(BYPASS_FEM_INFERENCE: 'false') do
+        example.run
+      end
+    end
+
+    it 'calls the inference server' do
+      responses = instance_double(OpenAI::Resources::Responses)
+      response = instance_double(OpenAI::Models::Responses::Response, output_text: 'A friendly error message')
+      allow(OpenAI::Client).to receive(:new).and_return(openai_client)
+      allow(openai_client).to receive(:responses).and_return(responses)
+      allow(responses).to receive(:create).and_return(response)
+
+      result = client.get_message('', '', '', '')
+      expect(result).to eq 'A friendly error message'
+    end
+  end
+
+  context 'when BYPASS_FEM_INFERENCE is true' do
+    around do |example|
+      ClimateControl.modify(BYPASS_FEM_INFERENCE: 'true') do
+        example.run
+      end
+    end
+
+    it 'returns a mock response' do
+      result = client.get_message('', '', '', '')
+      expect(result).to eq 'This is a placeholder friendly error message.'
+    end
+  end
+end

spec/requests/friendly_error_messages_spec.rb

@@ -12,6 +12,12 @@
       Flipper.enable(:ai_friendly_errors)
     end
 
+    around do |example|
+      ClimateControl.modify(BYPASS_FEM_INFERENCE: 'true') do
+        example.run
+      end
+    end
+
     it 'does not allow logged-out users' do
       post '/api/fem'