feat: editable LLM prompts and per-family preferred model

app/controllers/api/v1/chats_controller.rb

@@ -24,7 +24,7 @@ def create
         @message = @chat.messages.build(
           content: chat_params[:message],
           type: "UserMessage",
-          ai_model: chat_params[:model].presence || Chat.default_model
+          ai_model: chat_params[:model].presence || Chat.default_model(Current.user.family)
         )
 
         if @message.save

app/controllers/api/v1/messages_controller.rb

@@ -9,7 +9,7 @@ def create
     @message = @chat.messages.build(
       content: message_params[:content],
       type: "UserMessage",
-      ai_model: message_params[:model].presence || Chat.default_model
+      ai_model: message_params[:model].presence || Chat.default_model(@chat.user.family)
     )
 
     if @message.save

app/controllers/chats_controller.rb

@@ -17,7 +17,8 @@ def new
   end
 
   def create
-    @chat = Current.user.chats.start!(chat_params[:content], model: chat_params[:ai_model])
+    default_model = Chat.default_model(Current.user.family)
+    @chat = Current.user.chats.start!(chat_params[:content], model: chat_params[:ai_model].presence || default_model)
     set_last_viewed_chat(@chat)
     redirect_to chat_path(@chat, thinking: true)
   end

app/controllers/messages_controller.rb

@@ -7,7 +7,7 @@ def create
     @message = UserMessage.create!(
       chat: @chat,
       content: message_params[:content],
-      ai_model: message_params[:ai_model].presence || Chat.default_model
+      ai_model: message_params[:ai_model].presence || Chat.default_model(@chat.user.family)
     )
 
     redirect_to chat_path(@chat, thinking: true)

app/controllers/settings/ai_prompts_controller.rb

@@ -1,12 +1,41 @@
 class Settings::AiPromptsController < ApplicationController
   layout "settings"
+  before_action :ensure_admin, only: [ :show, :update ]
+  before_action :set_family
 
   def show
-    @breadcrumbs = [
-      [ "Home", root_path ],
-      [ "AI Prompts", nil ]
-    ]
-    @family = Current.family
+    @breadcrumbs = [ [ "Home", root_path ], [ "AI Prompts", nil ] ]
     @assistant_config = Assistant.config_for(OpenStruct.new(user: Current.user))
+    @effective_model = Chat.default_model(@family)
+    @show_openai_prompts = show_openai_prompts?
   end
+
+  def update
+    if @family.update(family_ai_params)
+      redirect_to settings_ai_prompts_path, notice: t(".success")
+    else
+      @assistant_config = Assistant.config_for(OpenStruct.new(user: Current.user))
+      @effective_model = Chat.default_model(@family)
+      @show_openai_prompts = show_openai_prompts?
+      render :show, status: :unprocessable_entity
+    end
+  end
+
+  private
+
+    def ensure_admin
+      redirect_to root_path, alert: t("settings.ai_prompts.not_authorized") unless Current.user&.admin?
+    end
+
+    def set_family
+      @family = Current.family
+    end
+
+    def family_ai_params
+      params.require(:family).permit(:preferred_ai_model, :openai_uri_base)
+    end
+
+    def show_openai_prompts?
+      @effective_model.blank? || @effective_model.match?(/\A(gpt-|o1-|gpt4)/i)
+    end
 end

app/helpers/application_helper.rb

@@ -125,9 +125,8 @@ def assistant_icon
   end
 
   def default_ai_model
-    # Always return a valid model, never nil or empty
-    # Delegates to Chat.default_model for consistency
-    Chat.default_model
+    family = Current.user&.family
+    Chat.default_model(family)
   end
 
   # Renders Markdown text using Redcarpet

app/models/assistant/builtin.rb

@@ -2,18 +2,24 @@ class Assistant::Builtin < Assistant::Base
   include Assistant::Provided
   include Assistant::Configurable
 
-  attr_reader :instructions
+  attr_reader :instructions, :prompt_metadata
 
   class << self
     def for_chat(chat)
       config = config_for(chat)
-      new(chat, instructions: config[:instructions], functions: config[:functions])
+      new(
+        chat,
+        instructions: config[:instructions],
+        prompt_metadata: config[:prompt_metadata],
+        functions: config[:functions]
+      )
     end
   end
 
-  def initialize(chat, instructions: nil, functions: [])
+  def initialize(chat, instructions: nil, prompt_metadata: nil, functions: [])
     super(chat)
     @instructions = instructions
+    @prompt_metadata = prompt_metadata
     @functions = functions
   end
 
@@ -24,14 +30,15 @@ def respond_to(message)
       ai_model: message.ai_model
     )
 
-    llm_provider = get_model_provider(message.ai_model)
+    llm_provider = get_model_provider(message.ai_model, family: chat.user&.family)
     unless llm_provider
       raise StandardError, build_no_provider_error_message(message.ai_model)
     end
 
     responder = Assistant::Responder.new(
       message: message,
       instructions: instructions,
+      prompt_metadata: prompt_metadata,
       function_tool_caller: function_tool_caller,
       llm: llm_provider
     )

app/models/assistant/configurable.rb

@@ -3,24 +3,40 @@ module Assistant::Configurable
 
   class_methods do
     def config_for(chat)
-      preferred_currency = Money::Currency.new(chat.user.family.currency)
-      preferred_date_format = chat.user.family.date_format
+      family = chat.user.family
+      preferred_currency = Money::Currency.new(family.currency)
+      preferred_date_format = family.date_format
 
       if chat.user.ui_layout_intro?
-        {
-          instructions: intro_instructions(preferred_currency, preferred_date_format),
-          functions: []
-        }
+        instructions_config = intro_instructions_config(preferred_currency, preferred_date_format)
+        { instructions: instructions_config[:content], prompt_metadata: instructions_config[:prompt], functions: [] }
       else
-        {
-          instructions: default_instructions(preferred_currency, preferred_date_format),
-          functions: default_functions
-        }
+        instructions_config = default_instructions(preferred_currency, preferred_date_format)
+        { instructions: instructions_config[:content], prompt_metadata: instructions_config[:prompt], functions: default_functions }
       end
     end
 
     private
-      def intro_instructions(preferred_currency, preferred_date_format)
+      def intro_instructions_config(preferred_currency, preferred_date_format)
+        langfuse_intro = langfuse_intro_instructions(preferred_currency, preferred_date_format)
+        if langfuse_intro.present?
+          { content: langfuse_intro[:content], prompt: langfuse_intro }
+        else
+          content = fallback_intro_instructions(preferred_currency, preferred_date_format)
+          { content: content, prompt: { name: "intro_instructions", version: 0, template: nil, content: content } }
+        end
+      end
+
+      def langfuse_intro_instructions(preferred_currency, preferred_date_format)
+        fetch_langfuse_prompt("intro_instructions",
+          preferred_currency_symbol: preferred_currency.symbol,
+          preferred_currency_iso_code: preferred_currency.iso_code,
+          preferred_date_format: preferred_date_format,
+          current_date: Date.current
+        )
+      end
+
+      def fallback_intro_instructions(preferred_currency, preferred_date_format)
         <<~PROMPT
           ## Your identity
 
@@ -56,6 +72,30 @@ def default_functions
       end
 
       def default_instructions(preferred_currency, preferred_date_format)
+        langfuse_instructions = langfuse_default_instructions(preferred_currency, preferred_date_format)
+
+        if langfuse_instructions.present?
+          { content: langfuse_instructions[:content], prompt: langfuse_instructions }
+        else
+          content = fallback_default_instructions(preferred_currency, preferred_date_format)
+          { content: content, prompt: { name: "default_instructions", version: 0, template: nil, content: content } }
+        end
+      end
+
+      def langfuse_default_instructions(preferred_currency, preferred_date_format)
+        fetch_langfuse_prompt("default_instructions",
+          preferred_currency_symbol: preferred_currency.symbol,
+          preferred_currency_iso_code: preferred_currency.iso_code,
+          preferred_currency_default_precision: preferred_currency.default_precision,
+          preferred_currency_default_format: preferred_currency.default_format,
+          preferred_currency_separator: preferred_currency.separator,
+          preferred_currency_delimiter: preferred_currency.delimiter,
+          preferred_date_format: preferred_date_format,
+          current_date: Date.current
+        )
+      end
+
+      def fallback_default_instructions(preferred_currency, preferred_date_format)
         <<~PROMPT
           ## Your identity
 
@@ -111,5 +151,38 @@ def default_instructions(preferred_currency, preferred_date_format)
             the data you're presenting represents and what context it is in (i.e. date range, account, etc.)
         PROMPT
       end
+
+      def fetch_langfuse_prompt(name, compile_params)
+        return unless langfuse_client
+
+        prompt = langfuse_client.get_prompt(name)
+        compiled_prompt = prompt.compile(**compile_params)
+
+        content = case compiled_prompt
+        when String
+          compiled_prompt
+        when Array
+          compiled_prompt.filter_map { |message| message[:content] }.join("\n\n")
+        else
+          nil
+        end
+
+        return if content.blank?
+
+        template = prompt.respond_to?(:prompt) ? prompt.prompt : (prompt.respond_to?(:template) ? prompt.template : nil)
+        { name: prompt.name, version: prompt.version, template: template, content: content }
+      rescue => e
+        Rails.logger.warn("Langfuse prompt retrieval failed (#{name}): #{e.message}")
+        nil
+      end
+
+      def langfuse_client
+        return unless ENV["LANGFUSE_PUBLIC_KEY"].present? && ENV["LANGFUSE_SECRET_KEY"].present?
+
+        @langfuse_client ||= Langfuse.new
+      rescue => e
+        Rails.logger.warn("Langfuse client initialization failed: #{e.message}")
+        nil
+      end
   end
 end

app/models/assistant/provided.rb

@@ -1,7 +1,12 @@
 module Assistant::Provided
   extend ActiveSupport::Concern
 
-  def get_model_provider(ai_model)
+  def get_model_provider(ai_model, family: nil)
+    family_provider = family.present? ? Provider::Registry.openai_for_family(family) : nil
+    if family_provider&.supports_model?(ai_model)
+      return family_provider
+    end
+
     registry.providers.find { |provider| provider.supports_model?(ai_model) }
   end
 

app/models/assistant/responder.rb

@@ -1,9 +1,10 @@
 class Assistant::Responder
-  def initialize(message:, instructions:, function_tool_caller:, llm:)
+  def initialize(message:, instructions:, function_tool_caller:, llm:, prompt_metadata: nil)
     @message = message
     @instructions = instructions
     @function_tool_caller = function_tool_caller
     @llm = llm
+    @prompt_metadata = prompt_metadata
   end
 
   def on(event_name, &block)
@@ -44,7 +45,7 @@ def respond(previous_response_id: nil)
   end
 
   private
-    attr_reader :message, :instructions, :function_tool_caller, :llm
+    attr_reader :message, :instructions, :function_tool_caller, :llm, :prompt_metadata
 
     def handle_follow_up_response(response)
       streamer = proc do |chunk|
@@ -77,6 +78,7 @@ def get_llm_response(streamer:, function_results: [], previous_response_id: nil)
         message.content,
         model: message.ai_model,
         instructions: instructions,
+        prompt_metadata: prompt_metadata,
         functions: function_tool_caller.function_definitions,
         function_results: function_results,
         messages: conversation_history,

app/models/chat.rb

@@ -25,10 +25,13 @@ def generate_title(prompt)
       prompt.first(80)
     end
 
-    # Returns the default AI model to use for chats
-    # Priority: AI Config > Setting
-    def default_model
-      Provider::Openai.effective_model.presence || Setting.openai_model
+    # Returns the default AI model to use for chats.
+    # Priority: family preferred > Provider::Openai.effective_model (ENV > Setting > default).
+    # @param family [Family, nil] optional family for per-family preferred model
+    # @return [String]
+    def default_model(family = nil)
+      family&.preferred_ai_model.presence ||
+        Provider::Openai.effective_model
     end
   end
 

app/models/family.rb

@@ -45,15 +45,25 @@ class Family < ApplicationRecord
   has_many :llm_usages, dependent: :destroy
   has_many :recurring_transactions, dependent: :destroy
 
+  PREFERRED_AI_MODEL_MAX_LENGTH = 128
+  OPENAI_URI_BASE_MAX_LENGTH = 512
+
   validates :locale, inclusion: { in: I18n.available_locales.map(&:to_s) }
   validates :date_format, inclusion: { in: DATE_FORMATS.map(&:last) }
   validates :month_start_day, inclusion: { in: 1..28 }
   validates :moniker, inclusion: { in: MONIKERS }
   validates :assistant_type, inclusion: { in: ASSISTANT_TYPES }
   validates :default_account_sharing, inclusion: { in: SHARING_DEFAULTS }
+  validates :preferred_ai_model, length: { maximum: PREFERRED_AI_MODEL_MAX_LENGTH }, allow_blank: true
+  validates :openai_uri_base, length: { maximum: OPENAI_URI_BASE_MAX_LENGTH }, allow_blank: true
+  validate :preferred_ai_model_required_when_custom_endpoint
 
   before_validation :normalize_enabled_currencies!
 
+  def custom_openai_endpoint?
+    openai_uri_base.present?
+  end
+
   def primary_currency_code
     normalize_currency_code(currency) || "USD"
   end
@@ -80,7 +90,6 @@ def secondary_enabled_currency_objects(extra: [])
     enabled_currency_objects(extra:).reject { |currency| currency.iso_code == primary_currency_code }
   end
 
-
   def moniker_label
     moniker.presence || "Family"
   end
@@ -329,6 +338,13 @@ def self_hoster?
   end
 
   private
+
+    def preferred_ai_model_required_when_custom_endpoint
+      return unless openai_uri_base.present? && preferred_ai_model.blank?
+
+      errors.add(:preferred_ai_model, :blank)
+    end
+
     def normalize_enabled_currencies!
       if enabled_currencies.blank?
         self.enabled_currencies = nil

app/models/provider/llm_concept.rb

@@ -38,6 +38,7 @@ def chat_response(
     prompt,
     model:,
     instructions: nil,
+    prompt_metadata: nil,
     functions: [],
     function_results: [],
     messages: nil,