diff --git a/app/controllers/discourse_ai/admin/ai_personas_controller.rb b/app/controllers/discourse_ai/admin/ai_personas_controller.rb
index 8ef466f1..cac72815 100644
--- a/app/controllers/discourse_ai/admin/ai_personas_controller.rb
+++ b/app/controllers/discourse_ai/admin/ai_personas_controller.rb
@@ -111,55 +111,26 @@ module DiscourseAi
 
         topic_id = params[:topic_id].to_i
         topic = nil
-        post = nil
 
         if topic_id > 0
           topic = Topic.find(topic_id)
 
-          raise Discourse::NotFound if topic.nil?
-
           if topic.topic_allowed_users.where(user_id: user.id).empty?
             return render_json_error(I18n.t("discourse_ai.errors.user_not_allowed"))
           end
-
-          post =
-            PostCreator.create!(
-              user,
-              topic_id: topic_id,
-              raw: params[:query],
-              skip_validations: true,
-              custom_fields: {
-                DiscourseAi::AiBot::Playground::BYPASS_AI_REPLY_CUSTOM_FIELD => true,
-              },
-            )
-        else
-          post =
-            PostCreator.create!(
-              user,
-              title: I18n.t("discourse_ai.ai_bot.default_pm_prefix"),
-              raw: params[:query],
-              archetype: Archetype.private_message,
-              target_usernames: "#{user.username},#{persona.user.username}",
-              skip_validations: true,
-              custom_fields: {
-                DiscourseAi::AiBot::Playground::BYPASS_AI_REPLY_CUSTOM_FIELD => true,
-              },
-            )
-
-          topic = post.topic
         end
 
         hijack = request.env["rack.hijack"]
         io = hijack.call
 
-        user = current_user
-
         DiscourseAi::AiBot::ResponseHttpStreamer.queue_streamed_reply(
-          io,
-          persona,
-          user,
-          topic,
-          post,
+          io: io,
+          persona: persona,
+          user: user,
+          topic: topic,
+          query: params[:query].to_s,
+          custom_instructions: params[:custom_instructions].to_s,
+          current_user: current_user,
         )
       end
 
diff --git a/lib/ai_bot/personas/persona.rb b/lib/ai_bot/personas/persona.rb
index ca47df0a..73224808 100644
--- a/lib/ai_bot/personas/persona.rb
+++ b/lib/ai_bot/personas/persona.rb
@@ -171,6 +171,11 @@ module DiscourseAi
               DiscourseAi::Completions::Llm.proxy(self.class.question_consolidator_llm)
           end
 
+          if context[:custom_instructions].present?
+            prompt_insts << "\n"
+            prompt_insts << context[:custom_instructions]
+          end
+
           fragments_guidance =
             rag_fragments_prompt(
               context[:conversation_context].to_a,
diff --git a/lib/ai_bot/playground.rb b/lib/ai_bot/playground.rb
index 4f0648cb..af18f989 100644
--- a/lib/ai_bot/playground.rb
+++ b/lib/ai_bot/playground.rb
@@ -392,7 +392,7 @@ module DiscourseAi
         result
       end
 
-      def reply_to(post, &blk)
+      def reply_to(post, custom_instructions: nil, &blk)
         # this is a multithreading issue
         # post custom prompt is needed and it may not
         # be properly loaded, ensure it is loaded
@@ -413,6 +413,7 @@ module DiscourseAi
         context[:post_id] = post.id
         context[:topic_id] = post.topic_id
         context[:private_message] = post.topic.private_message?
+        context[:custom_instructions] = custom_instructions
 
         reply_user = bot.bot_user
         if bot.persona.class.respond_to?(:user_id)
diff --git a/lib/ai_bot/response_http_streamer.rb b/lib/ai_bot/response_http_streamer.rb
index 382c47f6..ac1758ff 100644
--- a/lib/ai_bot/response_http_streamer.rb
+++ b/lib/ai_bot/response_http_streamer.rb
@@ -31,9 +31,36 @@ module DiscourseAi
 
         # keeping this in a static method so we don't capture ENV and other bits
         # this allows us to release memory earlier
-        def queue_streamed_reply(io, persona, user, topic, post)
+        def queue_streamed_reply(
+          io:,
+          persona:,
+          user:,
+          topic:,
+          query:,
+          custom_instructions:,
+          current_user:
+        )
           schedule_block do
             begin
+              post_params = {
+                raw: query,
+                skip_validations: true,
+                custom_fields: {
+                  DiscourseAi::AiBot::Playground::BYPASS_AI_REPLY_CUSTOM_FIELD => true,
+                },
+              }
+
+              if topic
+                post_params[:topic_id] = topic.id
+              else
+                post_params[:title] = I18n.t("discourse_ai.ai_bot.default_pm_prefix")
+                post_params[:archetype] = Archetype.private_message
+                post_params[:target_usernames] = "#{user.username},#{persona.user.username}"
+              end
+
+              post = PostCreator.create!(user, post_params)
+              topic = post.topic
+
               io.write "HTTP/1.1 200 OK"
               io.write CRLF
               io.write "Content-Type: text/plain; charset=utf-8"
@@ -52,7 +79,7 @@ module DiscourseAi
               io.flush
 
               persona_class =
-                DiscourseAi::AiBot::Personas::Persona.find_by(id: persona.id, user: user)
+                DiscourseAi::AiBot::Personas::Persona.find_by(id: persona.id, user: current_user)
               bot = DiscourseAi::AiBot::Bot.as(persona.user, persona: persona_class.new)
 
               data =
@@ -69,7 +96,7 @@ module DiscourseAi
 
               DiscourseAi::AiBot::Playground
                 .new(bot)
-                .reply_to(post) do |partial|
+                .reply_to(post, custom_instructions: custom_instructions) do |partial|
                   next if partial.length == 0
 
                   data = { partial: partial }.to_json + "\n\n"
@@ -88,11 +115,11 @@ module DiscourseAi
               io.write CRLF
 
               io.flush
-              io.done
+              io.done if io.respond_to?(:done)
             rescue StandardError => e
               # make it a tiny bit easier to debug in dev, this is tricky
               # multi-threaded code that exhibits various limitations in rails
-              p e if Rails.env.development?
+              p e if Rails.env.development? || Rails.env.test?
               Discourse.warn_exception(e, message: "Discourse AI: Unable to stream reply")
             ensure
               io.close
diff --git a/lib/completions/endpoints/fake.rb b/lib/completions/endpoints/fake.rb
index d057fb15..a51ff3ac 100644
--- a/lib/completions/endpoints/fake.rb
+++ b/lib/completions/endpoints/fake.rb
@@ -104,6 +104,10 @@ module DiscourseAi
           @last_call = params
         end
 
+        def self.previous_calls
+          @previous_calls ||= []
+        end
+
         def self.reset!
           @last_call = nil
           @fake_content = nil
@@ -118,7 +122,11 @@ module DiscourseAi
           feature_name: nil,
           feature_context: nil
         )
-          self.class.last_call = { dialect: dialect, user: user, model_params: model_params }
+          last_call = { dialect: dialect, user: user, model_params: model_params }
+          self.class.last_call = last_call
+          self.class.previous_calls << last_call
+          # guard memory in test
+          self.class.previous_calls.shift if self.class.previous_calls.length > 10
 
           content = self.class.fake_content
 
diff --git a/spec/requests/admin/ai_personas_controller_spec.rb b/spec/requests/admin/ai_personas_controller_spec.rb
index 50f71009..fb42506e 100644
--- a/spec/requests/admin/ai_personas_controller_spec.rb
+++ b/spec/requests/admin/ai_personas_controller_spec.rb
@@ -500,6 +500,7 @@ RSpec.describe DiscourseAi::Admin::AiPersonasController do
         allowed_group_ids: [Group::AUTO_GROUPS[:trust_level_0]],
         default_llm: "custom:#{llm.id}",
         allow_personal_messages: true,
+        system_prompt: "you are a helpful bot",
       )
 
       io_out, io_in = IO.pipe
@@ -510,6 +511,7 @@ RSpec.describe DiscourseAi::Admin::AiPersonasController do
              query: "how are you today?",
              user_unique_id: "site:test.com:user_id:1",
              preferred_username: "test_user",
+             custom_instructions: "To be appended to system prompt",
            },
            env: {
              "rack.hijack" => lambda { io_in },
@@ -521,6 +523,10 @@ RSpec.describe DiscourseAi::Admin::AiPersonasController do
       raw = io_out.read
       context_info = validate_streamed_response(raw, "This is a test! Testing!")
 
+      system_prompt = fake_endpoint.previous_calls[-2][:dialect].prompt.messages.first[:content]
+
+      expect(system_prompt).to eq("you are a helpful bot\nTo be appended to system prompt")
+
       expect(context_info["topic_id"]).to be_present
       topic = Topic.find(context_info["topic_id"])
       last_post = topic.posts.order(:created_at).last