diff --git a/internal/coordinator/server.go b/internal/coordinator/server.go
index cfb0b4d..2c9ca91 100644
--- a/internal/coordinator/server.go
+++ b/internal/coordinator/server.go
@@ -44,6 +44,13 @@ type Server struct {
 	sseMu           sync.Mutex
 	interrupts      *InterruptLedger
 	approvalTracked map[string]time.Time
+	// nudgePending tracks agents that should be nudged (check-in triggered)
+	// when they next become idle. Set when a message arrives for an agent.
+	// The liveness loop picks it up on the next tick where the agent is idle.
+	// Keyed by "space/agent".
+	nudgePending  map[string]time.Time
+	nudgeInFlight map[string]bool // prevents duplicate concurrent nudges
+	nudgeMu       sync.Mutex
 }
 
 func NewServer(port, dataDir string) *Server {
@@ -58,6 +65,8 @@ func NewServer(port, dataDir string) *Server {
 		sseClients:      make(map[*sseClient]struct{}),
 		interrupts:      NewInterruptLedger(dataDir),
 		approvalTracked: make(map[string]time.Time),
+		nudgePending:    make(map[string]time.Time),
+		nudgeInFlight:   make(map[string]bool),
 	}
 }
 
@@ -851,6 +860,12 @@ func (s *Server) handleAgentMessage(w http.ResponseWriter, r *http.Request, spac
 	})
 	s.broadcastSSE(spaceName, "agent_message", string(sseData))
 
+	// Mark agent for nudge — the liveness loop will trigger a check-in
+	// when the agent is next idle, so it reads the message via /raw.
+	s.nudgeMu.Lock()
+	s.nudgePending[spaceName+"/"+canonical] = time.Now()
+	s.nudgeMu.Unlock()
+
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusOK)
 	json.NewEncoder(w).Encode(map[string]interface{}{
@@ -1593,12 +1608,52 @@ func (s *Server) checkAllSessionLiveness() {
 				m["prompt_text"] = e.prompt
 			}
 			payload[i] = m
+
+			// Check if this idle agent has a pending nudge
+			if e.exists && e.idle {
+				s.nudgeMu.Lock()
+				if _, pending := s.nudgePending[key]; pending {
+					if !s.nudgeInFlight[key] {
+						s.nudgeInFlight[key] = true
+						delete(s.nudgePending, key)
+						s.nudgeMu.Unlock()
+						go s.executeNudge(space, e.agent)
+					} else {
+						s.nudgeMu.Unlock()
+					}
+				} else {
+					s.nudgeMu.Unlock()
+				}
+			}
 		}
 		data, _ := json.Marshal(payload)
 		s.broadcastSSE(space, "tmux_liveness", string(data))
 	}
 }
 
+// executeNudge triggers a single-agent check-in for an agent that has
+// pending messages. Called from the liveness loop when the agent is idle.
+func (s *Server) executeNudge(spaceName, agentName string) {
+	key := spaceName + "/" + agentName
+	defer func() {
+		s.nudgeMu.Lock()
+		delete(s.nudgeInFlight, key)
+		s.nudgeMu.Unlock()
+	}()
+
+	s.logEvent(fmt.Sprintf("[%s/%s] auto-nudge: message pending, triggering check-in", spaceName, agentName))
+	result := s.SingleAgentCheckIn(spaceName, agentName, "", "")
+
+	if len(result.Errors) > 0 {
+		s.logEvent(fmt.Sprintf("[%s/%s] auto-nudge failed: %s", spaceName, agentName, result.Errors[0]))
+	} else if len(result.Sent) > 0 {
+		s.logEvent(fmt.Sprintf("[%s/%s] auto-nudge complete", spaceName, agentName))
+	}
+
+	sseData, _ := json.Marshal(result)
+	s.broadcastSSE(spaceName, "broadcast_complete", string(sseData))
+}
+
 func (s *Server) recordDecisionInterrupts(spaceName, agentName string, update *AgentUpdate) {
 	for _, q := range update.Questions {
 		ctx := map[string]string{}