Filter out reasoning messages from Mistral

lib/ruby_llm/providers/mistral.rb

@@ -7,6 +7,7 @@ class Mistral < OpenAI
       include Mistral::Chat
       include Mistral::Models
       include Mistral::Embeddings
+      include Mistral::Streaming
 
       def api_base
         'https://api.mistral.ai/v1'

lib/ruby_llm/providers/mistral/streaming.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+module RubyLLM
+  module Providers
+    class Mistral
+      # Streaming methods of the Mistral API integration
+      module Streaming
+        module_function
+
+        def build_chunk(data)
+          Chunk.new(
+            role: :assistant,
+            model_id: data['model'],
+            content: extract_content(data),
+            tool_calls: parse_tool_calls(data.dig('choices', 0, 'delta', 'tool_calls'), parse_arguments: false),
+            input_tokens: data.dig('usage', 'prompt_tokens'),
+            output_tokens: data.dig('usage', 'completion_tokens')
+          )
+        end
+
+        def extract_content(data)
+          data = data.dig('choices', 0, 'delta', 'content')
+          return '' if data.is_a?(Array) || data.is_a?(Hash)
+
+          data.to_s
+        end
+      end
+    end
+  end
+end

spec/ruby_llm/providers/mistral/streaming_spec.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe RubyLLM::Providers::Mistral::Streaming do
+  let(:test_obj) do
+    Object.new.extend(described_class).tap do |obj|
+      allow(obj).to receive(:parse_tool_calls).and_return([]) # ignore tool calls
+    end
+  end
+
+  it 'correctly processes content on receiving reasoning messages (an array in choices.delta.content)' do
+    data = {
+      'choices' => [{
+        'index' => 0,
+        'delta' => {
+          'content' => [{
+            'type' => 'thinking',
+            'thinking' => [{ 'type' => 'text', 'text' => 'Okay' }]
+          }]
+        }
+      }]
+    }
+    expect(test_obj.send(:build_chunk, data).content).to eq('')
+  end
+
+  it 'correctly processes content on receiving normal messages' do
+    data = {
+      'choices' => [{
+        'index' => 0,
+        'delta' => { 'content' => 'thecontent' }
+      }]
+    }
+    expect(test_obj.send(:build_chunk, data).content).to eq('thecontent')
+  end
+end