diff --git a/daemon.go b/daemon.go
index 4dc8415..7b7ac13 100644
--- a/daemon.go
+++ b/daemon.go
@@ -168,6 +168,8 @@ type Daemon struct {
 	httpServer        *http.Server
 	lastHookTime      time.Time
 	mu                sync.Mutex // protects lastHookTime
+	notifier          Notifier
+	focus             *FocusTimer
 }
 
 // NewDaemon creates a daemon ready to start.
@@ -181,6 +183,8 @@ func NewDaemon(sockPath, procDir, claudeDir string, labels *LabelStore) *Daemon
 		pollInterval: 5 * time.Second,
 		stopCh:       make(chan struct{}),
 		hookPort:     3119,
+		notifier:     &ExecNotifier{},
+		focus:        &FocusTimer{},
 	}
 }
 
@@ -439,6 +443,15 @@ func (d *Daemon) handleConnection(conn net.Conn) {
 		}
 		writeResponse(conn, Response{OK: true})
 
+	case "focus":
+		var args FocusArgs
+		if err := json.Unmarshal(req.Args, &args); err != nil {
+			writeResponse(conn, Response{Error: "invalid focus args: " + err.Error()})
+			return
+		}
+		d.focus.Set(time.Duration(args.Minutes) * time.Minute)
+		writeResponse(conn, Response{OK: true, FocusRemaining: d.focus.Remaining().Minutes()})
+
 	case "stop":
 		writeResponse(conn, Response{OK: true})
 		d.Stop()
diff --git a/daemon_test.go b/daemon_test.go
index a894ad2..03ada50 100644
--- a/daemon_test.go
+++ b/daemon_test.go
@@ -432,6 +432,122 @@ func TestDaemonLabelOverSocket(t *testing.T) {
 	}
 }
 
+// spyNotifier records calls to Notify for test assertions.
+type spyNotifier struct {
+	calls []struct{ title, body string }
+}
+
+func (s *spyNotifier) Notify(title, body string) error {
+	s.calls = append(s.calls, struct{ title, body string }{title, body})
+	return nil
+}
+
+func TestNotification_WorkingToNeedsInput(t *testing.T) {
+	d := newTestDaemon(t)
+	spy := &spyNotifier{}
+	d.notifier = spy
+
+	// Seed session as Working
+	d.registry.UpdateFromHook("sess-1", "Working", "", "/tmp/proj")
+
+	// Transition to Needs Input
+	d.processHookEvent(HookEvent{
+		SessionID:     "sess-1",
+		HookEventName: "Stop",
+		Cwd:           "/tmp/proj",
+	})
+
+	if len(spy.calls) != 1 {
+		t.Fatalf("notify calls = %d, want 1", len(spy.calls))
+	}
+	if spy.calls[0].title != "vmux: proj" {
+		t.Errorf("title = %q, want %q", spy.calls[0].title, "vmux: proj")
+	}
+}
+
+func TestNotification_IdleToNeedsInput(t *testing.T) {
+	d := newTestDaemon(t)
+	spy := &spyNotifier{}
+	d.notifier = spy
+
+	// Seed session as Idle (not Working)
+	d.registry.UpdateFromHook("sess-1", "Idle", "", "/tmp/proj")
+
+	// Transition to Needs Input from Idle
+	d.processHookEvent(HookEvent{
+		SessionID:     "sess-1",
+		HookEventName: "Stop",
+		Cwd:           "/tmp/proj",
+	})
+
+	if len(spy.calls) != 0 {
+		t.Errorf("notify calls = %d, want 0 (Idle -> Needs Input should not notify)", len(spy.calls))
+	}
+}
+
+func TestNotification_FocusActive(t *testing.T) {
+	d := newTestDaemon(t)
+	spy := &spyNotifier{}
+	d.notifier = spy
+	d.focus.Set(30 * time.Minute)
+
+	// Seed session as Working
+	d.registry.UpdateFromHook("sess-1", "Working", "", "/tmp/proj")
+
+	// Transition to Needs Input (but focus active)
+	d.processHookEvent(HookEvent{
+		SessionID:     "sess-1",
+		HookEventName: "Stop",
+		Cwd:           "/tmp/proj",
+	})
+
+	if len(spy.calls) != 0 {
+		t.Errorf("notify calls = %d, want 0 (focus active should suppress)", len(spy.calls))
+	}
+}
+
+func TestNotification_FocusExpired(t *testing.T) {
+	d := newTestDaemon(t)
+	spy := &spyNotifier{}
+	d.notifier = spy
+	d.focus.Set(0) // expired immediately
+
+	// Seed session as Working
+	d.registry.UpdateFromHook("sess-1", "Working", "", "/tmp/proj")
+
+	// Transition to Needs Input (focus expired)
+	d.processHookEvent(HookEvent{
+		SessionID:     "sess-1",
+		HookEventName: "Stop",
+		Cwd:           "/tmp/proj",
+	})
+
+	if len(spy.calls) != 1 {
+		t.Fatalf("notify calls = %d, want 1 (focus expired should notify)", len(spy.calls))
+	}
+}
+
+func TestFocusHandler(t *testing.T) {
+	d := newTestDaemon(t)
+
+	if err := d.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	defer d.Stop()
+
+	args, _ := json.Marshal(FocusArgs{Minutes: 30})
+	resp := sendRequest(t, d.sockPath, Request{Action: "focus", Args: args})
+	if !resp.OK {
+		t.Fatalf("focus resp.OK = false, error = %q", resp.Error)
+	}
+	if !d.focus.IsActive() {
+		t.Error("focus should be active after handler")
+	}
+	if resp.FocusRemaining <= 0 {
+		t.Errorf("FocusRemaining = %v, want > 0", resp.FocusRemaining)
+	}
+}
+
 func TestDaemonUnknownAction(t *testing.T) {
 	d := newTestDaemon(t)
 
diff --git a/hook.go b/hook.go
index eaf97a7..2cf7aa6 100644
--- a/hook.go
+++ b/hook.go
@@ -70,8 +70,24 @@ func (d *Daemon) processHookEvent(event HookEvent) {
 		return
 	}
 
+	// Read PrevState BEFORE UpdateFromHook overwrites it
+	d.registry.mu.RLock()
+	prevState := ""
+	if ts, ok := d.registry.sessions[event.SessionID]; ok {
+		prevState = ts.PrevState
+	}
+	d.registry.mu.RUnlock()
+
 	d.registry.UpdateFromHook(event.SessionID, state, waitType, event.Cwd)
 
+	// Notify only on Working -> Needs Input transition (D-01)
+	if state == "Needs Input" && prevState == "Working" && !d.focus.IsActive() {
+		d.registry.mu.RLock()
+		info := d.registry.sessions[event.SessionID].Info
+		d.registry.mu.RUnlock()
+		d.notifier.Notify("vmux: "+shortName(info), "Session needs input ("+waitType+")")
+	}
+
 	d.mu.Lock()
 	d.lastHookTime = time.Now()
 	d.mu.Unlock()
diff --git a/main.go b/main.go
index 75fbd1f..35c5141 100644
--- a/main.go
+++ b/main.go
@@ -6,6 +6,7 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"
 
@@ -100,6 +101,33 @@ func main() {
 		}
 		fmt.Println("Label set.")
 
+	case "focus":
+		if len(filteredArgs) < 2 {
+			fmt.Fprintf(os.Stderr, "Usage: vmux focus <minutes>\n")
+			os.Exit(1)
+		}
+		minutes, err := strconv.Atoi(filteredArgs[1])
+		if err != nil || minutes < 0 {
+			fmt.Fprintf(os.Stderr, "Error: invalid minutes %q\n", filteredArgs[1])
+			os.Exit(1)
+		}
+		if err := EnsureDaemon(sockPath); err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			os.Exit(1)
+		}
+		client := NewClient(sockPath)
+		focusArgs, _ := json.Marshal(FocusArgs{Minutes: minutes})
+		resp, err := client.Send(Request{Action: "focus", Args: focusArgs})
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			os.Exit(1)
+		}
+		if !resp.OK {
+			fmt.Fprintf(os.Stderr, "Error: %s\n", resp.Error)
+			os.Exit(1)
+		}
+		fmt.Printf("Focus mode: notifications suppressed for %d minutes\n", minutes)
+
 	case "stop":
 		client := NewClient(sockPath)
 		resp, err := client.Send(Request{Action: "stop"})
@@ -170,6 +198,7 @@ Commands:
   list              List active Claude Code sessions
   switch <query>    Switch to the workspace of the matching session
   label <id> <text> Assign a label to a session
+  focus <minutes>   Suppress notifications for N minutes
   stop              Stop the vmux daemon
   daemon            Run the daemon in foreground (used internally)
 
diff --git a/protocol.go b/protocol.go
index d2ceb18..f8ba263 100644
--- a/protocol.go
+++ b/protocol.go
@@ -13,9 +13,10 @@ type Request struct {
 
 // Response is the JSON message sent back by the daemon.
 type Response struct {
-	OK       bool          `json:"ok"`
-	Error    string        `json:"error,omitempty"`
-	Sessions []SessionInfo `json:"sessions,omitempty"`
+	OK             bool          `json:"ok"`
+	Error          string        `json:"error,omitempty"`
+	Sessions       []SessionInfo `json:"sessions,omitempty"`
+	FocusRemaining float64       `json:"focus_remaining,omitempty"`
 }
 
 // SessionInfo is the wire format for a session in IPC responses.
@@ -42,3 +43,8 @@ type LabelArgs struct {
 	SessionID string `json:"session_id"`
 	Label     string `json:"label"`
 }
+
+// FocusArgs carries the duration for the focus command.
+type FocusArgs struct {
+	Minutes int `json:"minutes"`
+}