diff --git a/server/router/api/v1/memo_service.go b/server/router/api/v1/memo_service.go
index 47f3a9c36..70a6a2790 100644
--- a/server/router/api/v1/memo_service.go
+++ b/server/router/api/v1/memo_service.go
@@ -142,8 +142,8 @@ func (s *APIV1Service) CreateMemo(ctx context.Context, request *v1pb.CreateMemoR
 	}
 
 	// Broadcast live refresh event.
-	s.SSEHub.Broadcast(&MemoEvent{
-		Type: MemoEventCreated,
+	s.SSEHub.Broadcast(&SSEEvent{
+		Type: SSEEventMemoCreated,
 		Name: memoMessage.Name,
 	})
 
@@ -478,8 +478,8 @@ func (s *APIV1Service) UpdateMemo(ctx context.Context, request *v1pb.UpdateMemoR
 	}
 
 	// Broadcast live refresh event.
-	s.SSEHub.Broadcast(&MemoEvent{
-		Type: MemoEventUpdated,
+	s.SSEHub.Broadcast(&SSEEvent{
+		Type: SSEEventMemoUpdated,
 		Name: memoMessage.Name,
 	})
 
@@ -552,8 +552,8 @@ func (s *APIV1Service) DeleteMemo(ctx context.Context, request *v1pb.DeleteMemoR
 	}
 
 	// Broadcast live refresh event.
-	s.SSEHub.Broadcast(&MemoEvent{
-		Type: MemoEventDeleted,
+	s.SSEHub.Broadcast(&SSEEvent{
+		Type: SSEEventMemoDeleted,
 		Name: request.Name,
 	})
 
diff --git a/server/router/api/v1/reaction_service.go b/server/router/api/v1/reaction_service.go
index a7c7cc3bd..a4c521fe8 100644
--- a/server/router/api/v1/reaction_service.go
+++ b/server/router/api/v1/reaction_service.go
@@ -97,6 +97,12 @@ func (s *APIV1Service) UpsertMemoReaction(ctx context.Context, request *v1pb.Ups
 
 	reactionMessage := convertReactionFromStore(reaction)
 
+	// Broadcast live refresh event (reaction belongs to a memo).
+	s.SSEHub.Broadcast(&SSEEvent{
+		Type: SSEEventReactionUpserted,
+		Name: request.Reaction.ContentId,
+	})
+
 	return reactionMessage, nil
 }
 
@@ -136,6 +142,12 @@ func (s *APIV1Service) DeleteMemoReaction(ctx context.Context, request *v1pb.Del
 		return nil, status.Errorf(codes.Internal, "failed to delete reaction")
 	}
 
+	// Broadcast live refresh event (reaction belongs to a memo).
+	s.SSEHub.Broadcast(&SSEEvent{
+		Type: SSEEventReactionDeleted,
+		Name: reaction.ContentID,
+	})
+
 	return &emptypb.Empty{}, nil
 }
 
diff --git a/server/router/api/v1/sse_hub.go b/server/router/api/v1/sse_hub.go
index accebe97a..c75c3cc2c 100644
--- a/server/router/api/v1/sse_hub.go
+++ b/server/router/api/v1/sse_hub.go
@@ -5,24 +5,27 @@ import (
 	"sync"
 )
 
-// MemoEventType represents the type of memo change event.
-type MemoEventType string
+// SSEEventType represents the type of change event.
+type SSEEventType string
 
 const (
-	MemoEventCreated MemoEventType = "memo.created"
-	MemoEventUpdated MemoEventType = "memo.updated"
-	MemoEventDeleted MemoEventType = "memo.deleted"
+	SSEEventMemoCreated     SSEEventType = "memo.created"
+	SSEEventMemoUpdated     SSEEventType = "memo.updated"
+	SSEEventMemoDeleted     SSEEventType = "memo.deleted"
+	SSEEventReactionUpserted SSEEventType = "reaction.upserted"
+	SSEEventReactionDeleted  SSEEventType = "reaction.deleted"
 )
 
-// MemoEvent represents a memo change event sent to SSE clients.
-type MemoEvent struct {
-	Type MemoEventType `json:"type"`
-	// Name is the memo resource name (e.g., "memos/xxxx").
+// SSEEvent represents a change event sent to SSE clients.
+type SSEEvent struct {
+	Type SSEEventType `json:"type"`
+	// Name is the affected resource name (e.g., "memos/xxxx").
+	// For reaction events, this is the memo resource name that the reaction belongs to.
 	Name string `json:"name"`
 }
 
 // JSON returns the JSON representation of the event.
-func (e *MemoEvent) JSON() []byte {
+func (e *SSEEvent) JSON() []byte {
 	data, _ := json.Marshal(e)
 	return data
 }
@@ -72,7 +75,7 @@ func (h *SSEHub) Unsubscribe(c *sseClient) {
 // Broadcast sends an event to all connected clients.
 // Slow clients that have a full buffer will have the event dropped
 // to avoid blocking the broadcaster.
-func (h *SSEHub) Broadcast(event *MemoEvent) {
+func (h *SSEHub) Broadcast(event *SSEEvent) {
 	data := event.JSON()
 	h.mu.RLock()
 	defer h.mu.RUnlock()
diff --git a/web/src/hooks/useLiveMemoRefresh.ts b/web/src/hooks/useLiveMemoRefresh.ts
index e1a220d40..8dc9c40c1 100644
--- a/web/src/hooks/useLiveMemoRefresh.ts
+++ b/web/src/hooks/useLiveMemoRefresh.ts
@@ -81,7 +81,7 @@ export function useLiveMemoRefresh() {
                 const jsonStr = line.slice(6);
                 try {
                   const event = JSON.parse(jsonStr) as { type: string; name: string };
-                  handleMemoEvent(event, queryClient);
+                  handleSSEEvent(event, queryClient);
                 } catch {
                   // Ignore malformed JSON.
                 }
@@ -119,12 +119,12 @@ export function useLiveMemoRefresh() {
   }, [queryClient]);
 }
 
-interface MemoChangeEvent {
+interface SSEChangeEvent {
   type: string;
   name: string;
 }
 
-function handleMemoEvent(event: MemoChangeEvent, queryClient: ReturnType<typeof useQueryClient>) {
+function handleSSEEvent(event: SSEChangeEvent, queryClient: ReturnType<typeof useQueryClient>) {
   switch (event.type) {
     case "memo.created":
       // Invalidate memo lists so new memos appear.
@@ -148,5 +148,13 @@ function handleMemoEvent(event: MemoChangeEvent, queryClient: ReturnType<typeof
       // Invalidate user stats (memo count changed).
       queryClient.invalidateQueries({ queryKey: userKeys.stats() });
       break;
+
+    case "reaction.upserted":
+    case "reaction.deleted":
+      // Reactions are embedded in the memo object, so invalidate the memo detail
+      // and lists to reflect the updated reaction state.
+      queryClient.invalidateQueries({ queryKey: memoKeys.detail(event.name) });
+      queryClient.invalidateQueries({ queryKey: memoKeys.lists() });
+      break;
   }
 }