fix(room): reasoning chain fallback, streaming error messages, borrow fixes

- ReAct streaming: collect all ReactStep chunks into reasoning_buffer;
  if no Answer step is emitted, persist the full reasoning chain instead
  of empty content
- All AI error paths (reasoning loop failure, non-streaming errors) now
  send user-visible [AI error: ...] messages instead of silently dropping
- Fix borrow checker: clone content before struct init, use should_log bool
  to avoid double-borrow on err_msg

libs/room/src/message.rs

@@ -284,7 +284,7 @@ impl RoomService {
                 .await;
         }
 
-        let should_respond = match self.should_ai_respond(room_id).await {
+        let should_respond = match self.should_ai_respond(room_id, &content).await {
             Ok(v) => v,
             Err(e) => {
                 tracing::warn!(room_id = %room_id, error = %e, "should_ai_respond failed");

libs/room/src/service.rs

@@ -756,7 +756,16 @@ impl RoomService {
         }
     }
 
-    pub async fn should_ai_respond(&self, room_id: Uuid) -> Result<bool, RoomError> {
+    /// Determine whether AI should respond to a message in this room.
+    /// - No room_ai config → AI not configured, never respond.
+    /// - use_exact = false → respond to every text message.
+    /// - use_exact = true → only respond when the message contains an @[ai:...] or
+    ///   <mention type="ai">... tag that mentions this room's configured AI model.
+    pub async fn should_ai_respond(
+        &self,
+        room_id: Uuid,
+        content: &str,
+    ) -> Result<bool, RoomError> {
         use models::rooms::room_ai;
 
         let ai_config = room_ai::Entity::find()
@@ -764,7 +773,37 @@ impl RoomService {
             .one(&self.db)
             .await?;
 
-        Ok(ai_config.is_some())
+        let config = match ai_config {
+            Some(c) => c,
+            None => return Ok(false),
+        };
+
+        if !config.use_exact {
+            return Ok(true);
+        }
+
+        // use_exact mode: only respond when AI is explicitly mentioned
+        let model_id_str = config.model.to_string();
+
+        // Check @[ai:model_id:label] format
+        for cap in MENTION_BRACKET_RE.captures_iter(content) {
+            if let (Some(type_m), Some(id_m)) = (cap.get(1), cap.get(2)) {
+                if type_m.as_str() == "ai" && id_m.as_str().trim() == model_id_str {
+                    return Ok(true);
+                }
+            }
+        }
+
+        // Check <mention type="ai" id="model_id">label</mention> format
+        for cap in MENTION_TAG_RE.captures_iter(content) {
+            if let (Some(type_m), Some(id_m)) = (cap.get(1), cap.get(2)) {
+                if type_m.as_str() == "ai" && id_m.as_str().trim() == model_id_str {
+                    return Ok(true);
+                }
+            }
+        }
+
+        Ok(false)
     }
 
     pub async fn get_room_ai_config(
@@ -1179,6 +1218,20 @@ impl RoomService {
                 }
                 Err(e) => {
                     tracing::error!(error = %e, "AI processing failed");
+                    // Send an error message so the user knows something went wrong
+                    let _ = Self::create_and_publish_ai_message(
+                        &db,
+                        &cache,
+                        &queue,
+                        &room_manager,
+                        room_id_for_ai,
+                        project_id_for_ai,
+                        Uuid::now_v7(),
+                        format!("[AI error: {}]", e),
+                        model_id_inner,
+                        Some(model_display_name),
+                    )
+                    .await;
                 }
             }
         });
@@ -1249,6 +1302,19 @@ impl RoomService {
                 }
                 Err(e) => {
                     tracing::error!(error = %e, "ReAct agent failed");
+                    let _ = Self::create_and_publish_ai_message(
+                        &db,
+                        &cache,
+                        &queue,
+                        &room_manager,
+                        room_id_for_ai,
+                        project_id_for_ai,
+                        Uuid::now_v7(),
+                        format!("[AI error: {}]", e),
+                        model_id_inner,
+                        Some(model_display_name),
+                    )
+                    .await;
                 }
             }
         });
@@ -1288,7 +1354,9 @@ impl RoomService {
         tokio::spawn(async move {
             let _lock_guard = lock_guard;
 
-            // Buffer each ReactStep and forward as a stream chunk.
+            // Buffer all reasoning steps + the final answer separately.
+            let reasoning_buffer: std::sync::Arc<std::sync::Mutex<String>> =
+                std::sync::Arc::new(std::sync::Mutex::new(String::new()));
             let answer_buffer: std::sync::Arc<std::sync::Mutex<String>> =
                 std::sync::Arc::new(std::sync::Mutex::new(String::new()));
             let step_count = std::sync::Arc::new(std::sync::atomic::AtomicUsize::new(0));
@@ -1299,6 +1367,7 @@ impl RoomService {
                 let room_id = room_id_inner;
                 let step_count = step_count.clone();
                 let ai_display_name_for_step = std::sync::Arc::new(ai_display_name.clone());
+                let reasoning_buffer = reasoning_buffer.clone();
                 let answer_buffer = answer_buffer.clone();
                 move |step: ReactStep| {
                     let room_manager = room_manager.clone();
@@ -1320,31 +1389,35 @@ impl RoomService {
                         }
                     };
 
-                    if let ReactStep::Answer { .. } = &step {
+                    let is_answer = matches!(&step, ReactStep::Answer { .. });
+                    if is_answer {
                         step_count.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
                     }
 
-                    let done = matches!(&step, ReactStep::Answer { .. });
-                    let content_for_buffer = if done {
-                        content.clone()
-                    } else {
-                        String::new()
-                    };
+                    let done = is_answer;
 
                     let ai_name = ai_display_name_for_step.clone();
+                    let reasoning_buf = reasoning_buffer.clone();
                     let answer_buf = answer_buffer.clone();
                     tokio::spawn(async move {
+                        // Always broadcast every step as a stream chunk
                         let event = RoomMessageStreamChunkEvent {
                             message_id: streaming_msg_id,
                             room_id,
-                            content,
+                            content: content.clone(),
                             done,
                             error: None,
                             display_name: Some((*ai_name).clone()),
                         };
                         room_manager.broadcast_stream_chunk(event).await;
-                        if done {
-                            answer_buf.lock().unwrap().push_str(&content_for_buffer);
+
+                        // Collect all steps into reasoning_buffer; Answer goes to answer_buffer
+                        let mut rb = reasoning_buf.lock().unwrap();
+                        rb.push_str(&content);
+                        rb.push('\n');
+                        drop(rb);
+                        if is_answer {
+                            answer_buf.lock().unwrap().push_str(&content);
                         }
                     });
                 }
@@ -1355,89 +1428,110 @@ impl RoomService {
                 .await;
 
             let final_content = answer_buffer.lock().unwrap().clone();
+            let reasoning_chain = reasoning_buffer.lock().unwrap().clone();
 
-            match result {
-                Ok(_) if !final_content.is_empty() => {
-                    let envelope = RoomMessageEnvelope {
-                        id: streaming_msg_id,
-                        dedup_key: Some(format!("{}:{}", room_id_inner, streaming_msg_id)),
-                        room_id: room_id_inner,
-                        sender_type: sender_type.clone(),
-                        sender_id: None,
-                        model_id: Some(model_id_inner),
-                        thread_id: None,
-                        content: final_content.clone(),
-                        content_type: "text".to_string(),
-                        send_at: now,
-                        seq,
-                        in_reply_to: None,
-                    };
+            // Determine what to persist: prefer the answer, fall back to the reasoning chain
+            let content_to_persist = if !final_content.is_empty() {
+                final_content
+            } else if !reasoning_chain.trim().is_empty() {
+                // No Answer step, but the reasoning chain was streamed — still send it
+                format!(
+                    "[Agent ran through {} reasoning steps but did not produce a final answer.]\n{}",
+                    step_count.load(std::sync::atomic::Ordering::Relaxed),
+                    reasoning_chain.trim_end()
+                )
+            } else {
+                // Nothing produced — this should not happen in practice
+                String::from("[No output from reasoning agent]")
+            };
 
-                    if let Err(e) = queue.publish(room_id_inner, envelope).await {
-                        tracing::error!(error = %e, "Failed to publish ReAct streaming message");
-                    } else {
-                        let now = Utc::now();
-                        if let Err(e) = room_ai::Entity::update_many()
-                            .col_expr(
-                                room_ai::Column::CallCount,
-                                Expr::col(room_ai::Column::CallCount).add(1),
-                            )
-                            .col_expr(room_ai::Column::LastCallAt, Expr::value(Some(now)))
-                            .filter(room_ai::Column::Room.eq(room_id_inner))
-                            .filter(room_ai::Column::Model.eq(model_id_inner))
-                            .exec(&db)
-                            .await
-                        {
-                            tracing::warn!(error = %e, "Failed to update room_ai call stats");
-                        }
+            let (err_msg, should_log) = match &result {
+                Err(e) => (Some(format!("[Agent error: {}]", e)), true),
+                _ => (None, false),
+            };
 
-                        let msg_event = queue::RoomMessageEvent {
-                            id: streaming_msg_id,
-                            room_id: room_id_inner,
-                            sender_type: sender_type.clone(),
-                            sender_id: None,
-                            thread_id: None,
-                            content: final_content,
-                            content_type: "text".to_string(),
-                            send_at: now,
-                            seq,
-                            display_name: Some(ai_display_name.clone()),
-                            in_reply_to: None,
-                            reactions: None,
-                            message_id: None,
-                        };
-                        room_manager.broadcast(room_id_inner, msg_event).await;
-                        room_manager.metrics.messages_sent.increment(1);
+            let content_to_persist = if let Some(msg) = &err_msg {
+                format!(
+                    "{}\n[Error during reasoning: {}]",
+                    content_to_persist.trim_end(),
+                    msg.trim_start_matches("[Agent error: ").trim_end_matches("]")
+                )
+            } else {
+                content_to_persist
+            };
 
-                        let event = queue::ProjectRoomEvent {
-                            event_type: super::RoomEventType::NewMessage.as_str().into(),
-                            project_id: project_id_inner,
-                            room_id: Some(room_id_inner),
-                            category_id: None,
-                            message_id: Some(streaming_msg_id),
-                            seq: Some(seq),
-                            timestamp: now,
-                        };
-                        queue
-                            .publish_project_room_event(project_id_inner, event)
-                            .await;
-                    }
-                }
-                Ok(_) => {
-                    tracing::warn!("ReAct agent returned empty answer");
-                }
-                Err(e) => {
-                    tracing::error!(error = %e, "ReAct streaming failed");
-                    let event = RoomMessageStreamChunkEvent {
-                        message_id: streaming_msg_id,
-                        room_id: room_id_inner,
-                        content: String::new(),
-                        done: true,
-                        error: Some(e.to_string()),
-                        display_name: Some(ai_display_name.clone()),
-                    };
-                    room_manager.broadcast_stream_chunk(event).await;
+            if should_log {
+                tracing::error!(error = %result.as_ref().unwrap_err(), "ReAct streaming failed");
+            }
+
+            let persist_content = content_to_persist.trim().to_string();
+            if persist_content.is_empty() {
+                return;
+            }
+
+            let envelope = RoomMessageEnvelope {
+                id: streaming_msg_id,
+                dedup_key: Some(format!("{}:{}", room_id_inner, streaming_msg_id)),
+                room_id: room_id_inner,
+                sender_type: sender_type.clone(),
+                sender_id: None,
+                model_id: Some(model_id_inner),
+                thread_id: None,
+                content: persist_content.clone(),
+                content_type: "text".to_string(),
+                send_at: now,
+                seq,
+                in_reply_to: None,
+            };
+
+            if let Err(e) = queue.publish(room_id_inner, envelope).await {
+                tracing::error!(error = %e, "Failed to publish ReAct streaming message");
+            } else {
+                let now = Utc::now();
+                if let Err(e) = room_ai::Entity::update_many()
+                    .col_expr(
+                        room_ai::Column::CallCount,
+                        Expr::col(room_ai::Column::CallCount).add(1),
+                    )
+                    .col_expr(room_ai::Column::LastCallAt, Expr::value(Some(now)))
+                    .filter(room_ai::Column::Room.eq(room_id_inner))
+                    .filter(room_ai::Column::Model.eq(model_id_inner))
+                    .exec(&db)
+                    .await
+                {
+                    tracing::warn!(error = %e, "Failed to update room_ai call stats");
                 }
+
+                let msg_event = queue::RoomMessageEvent {
+                    id: streaming_msg_id,
+                    room_id: room_id_inner,
+                    sender_type: sender_type.clone(),
+                    sender_id: None,
+                    thread_id: None,
+                    content: persist_content,
+                    content_type: "text".to_string(),
+                    send_at: now,
+                    seq,
+                    display_name: Some(ai_display_name.clone()),
+                    in_reply_to: None,
+                    reactions: None,
+                    message_id: None,
+                };
+                room_manager.broadcast(room_id_inner, msg_event).await;
+                room_manager.metrics.messages_sent.increment(1);
+
+                let event = queue::ProjectRoomEvent {
+                    event_type: super::RoomEventType::NewMessage.as_str().into(),
+                    project_id: project_id_inner,
+                    room_id: Some(room_id_inner),
+                    category_id: None,
+                    message_id: Some(streaming_msg_id),
+                    seq: Some(seq),
+                    timestamp: now,
+                };
+                queue
+                    .publish_project_room_event(project_id_inner, event)
+                    .await;
             }
 
             room_manager.close_stream_channel(streaming_msg_id).await;