From 099b937a70485305d17134e6ddcb24e65e11d3e0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Jos=C3=A9=20Mata?= <jjmata@jjmata.com>
Date: Wed, 1 Oct 2025 20:04:59 +0200
Subject: [PATCH 1/4] Fetch Langfuse prompt for assistant instructions

---
 app/models/assistant.rb              | 13 ++++--
 app/models/assistant/configurable.rb | 68 +++++++++++++++++++++++++++-
 app/models/assistant/responder.rb    |  6 ++-
 app/models/provider/llm_concept.rb   |  1 +
 app/models/provider/openai.rb        | 60 +++++++++++++++---------
 5 files changed, 121 insertions(+), 27 deletions(-)

diff --git a/app/models/assistant.rb b/app/models/assistant.rb
index c077c2f0d94..7be7d5aa5db 100644
--- a/app/models/assistant.rb
+++ b/app/models/assistant.rb
@@ -1,18 +1,24 @@
 class Assistant
   include Provided, Configurable, Broadcastable
 
-  attr_reader :chat, :instructions
+  attr_reader :chat, :instructions, :instructions_prompt
 
   class << self
     def for_chat(chat)
       config = config_for(chat)
-      new(chat, instructions: config[:instructions], functions: config[:functions])
+      new(
+        chat,
+        instructions: config[:instructions],
+        instructions_prompt: config[:instructions_prompt],
+        functions: config[:functions]
+      )
     end
   end
 
-  def initialize(chat, instructions: nil, functions: [])
+  def initialize(chat, instructions: nil, instructions_prompt: nil, functions: [])
     @chat = chat
     @instructions = instructions
+    @instructions_prompt = instructions_prompt
     @functions = functions
   end
 
@@ -26,6 +32,7 @@ def respond_to(message)
     responder = Assistant::Responder.new(
       message: message,
       instructions: instructions,
+      instructions_prompt: instructions_prompt,
       function_tool_caller: function_tool_caller,
       llm: get_model_provider(message.ai_model)
     )
diff --git a/app/models/assistant/configurable.rb b/app/models/assistant/configurable.rb
index 1da95d14b87..d6cce302ae3 100644
--- a/app/models/assistant/configurable.rb
+++ b/app/models/assistant/configurable.rb
@@ -6,8 +6,11 @@ def config_for(chat)
       preferred_currency = Money::Currency.new(chat.user.family.currency)
       preferred_date_format = chat.user.family.date_format
 
+      instructions_config = default_instructions(preferred_currency, preferred_date_format)
+
       {
-        instructions: default_instructions(preferred_currency, preferred_date_format),
+        instructions: instructions_config[:content],
+        instructions_prompt: instructions_config[:prompt],
         functions: default_functions
       }
     end
@@ -23,6 +26,60 @@ 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),
+            prompt: nil
+          }
+        end
+      end
+
+      def langfuse_default_instructions(preferred_currency, preferred_date_format)
+        return unless langfuse_client
+
+        prompt = langfuse_client.get_prompt("default_instructions")
+
+        compiled_prompt = prompt.compile(
+          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
+        )
+
+        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?
+
+        {
+          name: prompt.name,
+          version: prompt.version,
+          template: prompt.prompt,
+          content: content
+        }
+      rescue => e
+        Rails.logger.warn("Langfuse prompt retrieval failed: #{e.message}")
+        nil
+      end
+
+      def fallback_default_instructions(preferred_currency, preferred_date_format)
         <<~PROMPT
           ## Your identity
 
@@ -78,5 +135,14 @@ 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 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
diff --git a/app/models/assistant/responder.rb b/app/models/assistant/responder.rb
index dffcf4dd0e5..516c1ea1de1 100644
--- a/app/models/assistant/responder.rb
+++ b/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:, instructions_prompt: nil)
     @message = message
     @instructions = instructions
     @function_tool_caller = function_tool_caller
     @llm = llm
+    @instructions_prompt = instructions_prompt
   end
 
   def on(event_name, &block)
@@ -31,7 +32,7 @@ def respond(previous_response_id: nil)
   end
 
   private
-    attr_reader :message, :instructions, :function_tool_caller, :llm
+    attr_reader :message, :instructions, :function_tool_caller, :llm, :instructions_prompt
 
     def handle_follow_up_response(response)
       streamer = proc do |chunk|
@@ -64,6 +65,7 @@ def get_llm_response(streamer:, function_results: [], previous_response_id: nil)
         message.content,
         model: message.ai_model,
         instructions: instructions,
+        instructions_prompt: instructions_prompt,
         functions: function_tool_caller.function_definitions,
         function_results: function_results,
         streamer: streamer,
diff --git a/app/models/provider/llm_concept.rb b/app/models/provider/llm_concept.rb
index be0b46a07ed..bf9e2251610 100644
--- a/app/models/provider/llm_concept.rb
+++ b/app/models/provider/llm_concept.rb
@@ -22,6 +22,7 @@ def chat_response(
     prompt,
     model:,
     instructions: nil,
+    instructions_prompt: nil,
     functions: [],
     function_results: [],
     streamer: nil,
diff --git a/app/models/provider/openai.rb b/app/models/provider/openai.rb
index ddde08bad4c..75bff06e1a7 100644
--- a/app/models/provider/openai.rb
+++ b/app/models/provider/openai.rb
@@ -62,6 +62,7 @@ def chat_response(
     prompt,
     model:,
     instructions: nil,
+    instructions_prompt: nil,
     functions: [],
     function_results: [],
     streamer: nil,
@@ -112,6 +113,7 @@ def chat_response(
           model: model,
           input: input_payload,
           output: response.messages.map(&:output_text).join("\n"),
+          prompt: instructions_prompt,
           session_id: session_id,
           user_identifier: user_identifier
         )
@@ -123,6 +125,7 @@ def chat_response(
           model: model,
           input: input_payload,
           output: parsed.messages.map(&:output_text).join("\n"),
+          prompt: instructions_prompt,
           usage: raw_response["usage"],
           session_id: session_id,
           user_identifier: user_identifier
@@ -141,26 +144,41 @@ def langfuse_client
       @langfuse_client = Langfuse.new
     end
 
-    def log_langfuse_generation(name:, model:, input:, output:, usage: nil, session_id: nil, user_identifier: nil)
-      return unless langfuse_client
-
-      trace = langfuse_client.trace(
-        name: "openai.#{name}",
-        input: input,
-        session_id: session_id,
-        user_id: user_identifier
-      )
-      trace.generation(
-        name: name,
-        model: model,
-        input: input,
-        output: output,
-        usage: usage,
-        session_id: session_id,
-        user_id: user_identifier
-      )
-      trace.update(output: output)
-    rescue => e
-      Rails.logger.warn("Langfuse logging failed: #{e.message}")
+  def log_langfuse_generation(name:, model:, input:, output:, usage: nil, session_id: nil, user_identifier: nil, prompt: nil)
+    return unless langfuse_client
+
+    trace = langfuse_client.trace(
+      name: "openai.#{name}",
+      input: input,
+      session_id: session_id,
+      user_id: user_identifier
+    )
+    generation_options = {
+      name: name,
+      model: model,
+      input: input,
+      output: output,
+      usage: usage,
+      session_id: session_id,
+      user_id: user_identifier
+    }
+
+    if prompt.present?
+      generation_options[:version] = prompt[:version] if prompt[:version]
+      metadata = {
+        prompt: {
+          name: prompt[:name],
+          version: prompt[:version],
+          content: prompt[:content],
+          template: prompt[:template]
+        }.compact
+      }
+      generation_options[:metadata] = metadata
     end
+
+    trace.generation(**generation_options)
+    trace.update(output: output)
+  rescue => e
+    Rails.logger.warn("Langfuse logging failed: #{e.message}")
+  end
 end

From d8804ea78bf0b595b23687a3f68c0008818b70ac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Jos=C3=A9=20Mata?= <jjmata@jjmata.com>
Date: Wed, 1 Oct 2025 20:45:07 +0200
Subject: [PATCH 2/4] Handle nil values when compiling Langfuse instructions

---
 app/models/assistant/configurable.rb | 53 ++++++++++++++++++----------
 1 file changed, 34 insertions(+), 19 deletions(-)

diff --git a/app/models/assistant/configurable.rb b/app/models/assistant/configurable.rb
index d6cce302ae3..ed794e6ded3 100644
--- a/app/models/assistant/configurable.rb
+++ b/app/models/assistant/configurable.rb
@@ -45,27 +45,14 @@ def langfuse_default_instructions(preferred_currency, preferred_date_format)
         return unless langfuse_client
 
         prompt = langfuse_client.get_prompt("default_instructions")
-
-        compiled_prompt = prompt.compile(
-          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
+        return if prompt.nil?
+        compiled_prompt = compile_langfuse_prompt(
+          prompt,
+          preferred_currency: preferred_currency,
+          preferred_date_format: preferred_date_format
         )
 
-        content = case compiled_prompt
-                  when String
-                    compiled_prompt
-                  when Array
-                    compiled_prompt.filter_map { |message| message[:content] }.join("\n\n")
-                  else
-                    nil
-                  end
-
+        content = extract_prompt_content(compiled_prompt)
         return if content.blank?
 
         {
@@ -79,6 +66,34 @@ def langfuse_default_instructions(preferred_currency, preferred_date_format)
         nil
       end
 
+      def compile_langfuse_prompt(prompt, preferred_currency:, preferred_date_format:)
+        variables = {
+          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
+        }.transform_values { |value| value.nil? ? "" : value.to_s }
+
+        prompt.compile(**variables)
+      end
+
+      def extract_prompt_content(compiled_prompt)
+        case compiled_prompt
+        when String
+          compiled_prompt
+        when Array
+          compiled_prompt.filter_map do |message|
+            message[:content] || message["content"]
+          end.join("\n\n")
+        else
+          nil
+        end
+      end
+
       def fallback_default_instructions(preferred_currency, preferred_date_format)
         <<~PROMPT
           ## Your identity

From 17f5c027d82bdb5d21fd64d7f36a704e63e39b27 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Jos=C3=A9=20Mata?= <juanjo.mata@gmail.com>
Date: Wed, 1 Oct 2025 19:47:19 +0000
Subject: [PATCH 3/4] Fixes and prompt support

---
 app/models/assistant/configurable.rb | 33 ++++++++++++-
 app/models/provider/openai.rb        | 74 +++++++++++++++-------------
 2 files changed, 70 insertions(+), 37 deletions(-)

diff --git a/app/models/assistant/configurable.rb b/app/models/assistant/configurable.rb
index ed794e6ded3..1fdca9a1ce6 100644
--- a/app/models/assistant/configurable.rb
+++ b/app/models/assistant/configurable.rb
@@ -46,8 +46,13 @@ def langfuse_default_instructions(preferred_currency, preferred_date_format)
 
         prompt = langfuse_client.get_prompt("default_instructions")
         return if prompt.nil?
+
+        # TODO: remove after we make the code resilient to chat vs. text types of prompts
+        Rails.logger.warn("Langfuse prompt retrieved: #{prompt.name} #{prompt.version}")
+        Rails.logger.warn("Langfuse prompt retrieved: #{prompt.prompt}")
+
         compiled_prompt = compile_langfuse_prompt(
-          prompt,
+          prompt.prompt.dig(0, "content"),
           preferred_currency: preferred_currency,
           preferred_date_format: preferred_date_format
         )
@@ -56,6 +61,7 @@ def langfuse_default_instructions(preferred_currency, preferred_date_format)
         return if content.blank?
 
         {
+          id: prompt.respond_to?(:id) ? prompt.id : (prompt[:id] rescue nil),
           name: prompt.name,
           version: prompt.version,
           template: prompt.prompt,
@@ -78,7 +84,30 @@ def compile_langfuse_prompt(prompt, preferred_currency:, preferred_date_format:)
           current_date: Date.current
         }.transform_values { |value| value.nil? ? "" : value.to_s }
 
-        prompt.compile(**variables)
+        # If the prompt object supports compilation, use it. Otherwise, perform
+        # a lightweight local interpolation for String/Array/Hash templates.
+        if prompt.respond_to?(:compile)
+          prompt.compile(**variables)
+        else
+          interpolate_template(prompt, variables)
+        end
+      end
+
+      def interpolate_template(template, variables)
+        case template
+        when String
+          # Replace {{ variable }} placeholders with provided variables
+          template.gsub(/\{\{\s*(\w+)\s*\}\}/) do
+            key = Regexp.last_match(1)
+            variables[key] || ""
+          end
+        when Array
+          template.map { |item| interpolate_template(item, variables) }
+        when Hash
+          template.transform_values { |v| interpolate_template(v, variables) }
+        else
+          template
+        end
       end
 
       def extract_prompt_content(compiled_prompt)
diff --git a/app/models/provider/openai.rb b/app/models/provider/openai.rb
index 75bff06e1a7..58a6ef94a3d 100644
--- a/app/models/provider/openai.rb
+++ b/app/models/provider/openai.rb
@@ -144,41 +144,45 @@ def langfuse_client
       @langfuse_client = Langfuse.new
     end
 
-  def log_langfuse_generation(name:, model:, input:, output:, usage: nil, session_id: nil, user_identifier: nil, prompt: nil)
-    return unless langfuse_client
-
-    trace = langfuse_client.trace(
-      name: "openai.#{name}",
-      input: input,
-      session_id: session_id,
-      user_id: user_identifier
-    )
-    generation_options = {
-      name: name,
-      model: model,
-      input: input,
-      output: output,
-      usage: usage,
-      session_id: session_id,
-      user_id: user_identifier
-    }
-
-    if prompt.present?
-      generation_options[:version] = prompt[:version] if prompt[:version]
-      metadata = {
-        prompt: {
-          name: prompt[:name],
-          version: prompt[:version],
-          content: prompt[:content],
-          template: prompt[:template]
-        }.compact
+    def log_langfuse_generation(name:, model:, input:, output:, usage: nil, session_id: nil, user_identifier: nil, prompt: nil)
+      return unless langfuse_client
+
+      trace = langfuse_client.trace(
+        name: "openai.#{name}",
+        input: input,
+        session_id: session_id,
+        user_id: user_identifier
+      )
+      generation_options = {
+        name: name,
+        model: model,
+        input: input,
+        output: output,
+        usage: usage,
+        session_id: session_id,
+        user_id: user_identifier
       }
-      generation_options[:metadata] = metadata
-    end
 
-    trace.generation(**generation_options)
-    trace.update(output: output)
-  rescue => e
-    Rails.logger.warn("Langfuse logging failed: #{e.message}")
-  end
+      if prompt.present?
+        generation_options[:prompt_name] = prompt[:name] if prompt[:name]
+        generation_options[:prompt_version] = prompt[:version] if prompt[:version]
+        generation_options[:prompt_id] = prompt[:id] if prompt[:id]
+
+        metadata = {
+          prompt: {
+            id: prompt[:id],
+            name: prompt[:name],
+            version: prompt[:version],
+            content: prompt[:content],
+            template: prompt[:template]
+          }.compact
+        }
+        generation_options[:metadata] = metadata
+      end
+
+      trace.generation(**generation_options)
+      trace.update(output: output)
+    rescue => e
+      Rails.logger.warn("Langfuse logging failed: #{e.message}")
+    end
 end

From 805d4051a59813cdf8238c3dfef16acbdc8b0178 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Jos=C3=A9=20Mata?= <juanjo.mata@gmail.com>
Date: Wed, 1 Oct 2025 20:30:22 +0000
Subject: [PATCH 4/4] Fix {{variable}} replacement

---
 app/models/assistant/configurable.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/models/assistant/configurable.rb b/app/models/assistant/configurable.rb
index 1fdca9a1ce6..8c78a72d236 100644
--- a/app/models/assistant/configurable.rb
+++ b/app/models/assistant/configurable.rb
@@ -98,7 +98,7 @@ def interpolate_template(template, variables)
         when String
           # Replace {{ variable }} placeholders with provided variables
           template.gsub(/\{\{\s*(\w+)\s*\}\}/) do
-            key = Regexp.last_match(1)
+            key = Regexp.last_match(1).to_sym
             variables[key] || ""
           end
         when Array