diff --git a/cmd/search.go b/cmd/search.go
index 3554baa..d092501 100644
--- a/cmd/search.go
+++ b/cmd/search.go
@@ -52,6 +52,10 @@ func runSearch(cmd *cobra.Command, args []string) error {
 		after = searchAroundFlag
 	}
 
+	if before < 0 || after < 0 {
+		return fmt.Errorf("--before, --after, and --around must be non-negative")
+	}
+
 	client := daemon.NewClient()
 	if err := client.EnsureDaemon(); err != nil {
 		return fmt.Errorf("daemon: %w", err)
diff --git a/internal/daemon/server.go b/internal/daemon/server.go
index c6b1ef9..8a8225c 100644
--- a/internal/daemon/server.go
+++ b/internal/daemon/server.go
@@ -17,6 +17,21 @@ import (
 	"github.com/schovi/shelli/internal/ansi"
 )
 
+type ptyHandle struct {
+	f         *os.File
+	closeOnce sync.Once
+}
+
+func (p *ptyHandle) Close() {
+	p.closeOnce.Do(func() {
+		p.f.Close()
+	})
+}
+
+func (p *ptyHandle) File() *os.File {
+	return p.f
+}
+
 type Session struct {
 	Name      string       `json:"name"`
 	PID       int          `json:"pid"`
@@ -38,7 +53,7 @@ type SessionInfo struct {
 type Server struct {
 	mu             sync.Mutex
 	sessions       map[string]*Session
-	ptys           map[string]*os.File
+	ptys           map[string]*ptyHandle
 	cmds           map[string]*exec.Cmd
 	doneChans      map[string]chan struct{}
 	frameDetectors map[string]*ansi.FrameDetector
@@ -87,7 +102,7 @@ func NewServer(opts ...ServerOption) (*Server, error) {
 
 	s := &Server{
 		sessions:        make(map[string]*Session),
-		ptys:            make(map[string]*os.File),
+		ptys:            make(map[string]*ptyHandle),
 		cmds:            make(map[string]*exec.Cmd),
 		doneChans:       make(map[string]chan struct{}),
 		frameDetectors:  make(map[string]*ansi.FrameDetector),
@@ -162,7 +177,10 @@ func (s *Server) Start() error {
 	for {
 		conn, err := listener.Accept()
 		if err != nil {
-			if s.listener == nil {
+			s.mu.Lock()
+			isShutdown := s.listener == nil
+			s.mu.Unlock()
+			if isShutdown {
 				return nil
 			}
 			return err
@@ -211,8 +229,8 @@ func (s *Server) Shutdown() {
 			if done, ok := s.doneChans[name]; ok {
 				close(done)
 			}
-			if ptmx, ok := s.ptys[name]; ok {
-				ptmx.Close()
+			if handle, ok := s.ptys[name]; ok {
+				handle.Close()
 			}
 			if cmd, ok := s.cmds[name]; ok {
 				cmd.Process.Kill()
@@ -380,8 +398,9 @@ func (s *Server) handleCreate(req Request) Response {
 		CreatedAt: now,
 	}
 
+	handle := &ptyHandle{f: ptmx}
 	s.sessions[req.Name] = sess
-	s.ptys[req.Name] = ptmx
+	s.ptys[req.Name] = handle
 	s.cmds[req.Name] = cmd
 	s.doneChans[req.Name] = make(chan struct{})
 	if req.TUIMode {
@@ -389,7 +408,7 @@ func (s *Server) handleCreate(req Request) Response {
 		s.responders[req.Name] = ansi.NewTerminalResponder(ptmx)
 	}
 
-	go s.captureOutput(req.Name, ptmx, cmd)
+	go s.captureOutput(req.Name, handle, cmd)
 
 	return Response{Success: true, Data: map[string]interface{}{
 		"name":       sess.Name,
@@ -401,7 +420,7 @@ func (s *Server) handleCreate(req Request) Response {
 	}}
 }
 
-func (s *Server) captureOutput(name string, ptmx *os.File, cmd *exec.Cmd) {
+func (s *Server) captureOutput(name string, handle *ptyHandle, cmd *exec.Cmd) {
 	s.mu.Lock()
 	done := s.doneChans[name]
 	detector := s.frameDetectors[name]
@@ -409,6 +428,8 @@ func (s *Server) captureOutput(name string, ptmx *os.File, cmd *exec.Cmd) {
 	storage := s.storage
 	s.mu.Unlock()
 
+	f := handle.File()
+
 	if detector != nil {
 		defer func() {
 			if pending := detector.Flush(); len(pending) > 0 {
@@ -425,8 +446,8 @@ func (s *Server) captureOutput(name string, ptmx *os.File, cmd *exec.Cmd) {
 		default:
 		}
 
-		ptmx.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
-		n, err := ptmx.Read(buf)
+		f.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+		n, err := f.Read(buf)
 		if n > 0 {
 			data := buf[:n]
 			if responder != nil {
@@ -450,7 +471,7 @@ func (s *Server) captureOutput(name string, ptmx *os.File, cmd *exec.Cmd) {
 	}
 
 	cmd.Wait()
-	ptmx.Close()
+	handle.Close()
 
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -626,11 +647,12 @@ func (s *Server) handleSnapshot(req Request) Response {
 		s.mu.Unlock()
 		return Response{Success: false, Error: fmt.Sprintf("session %q is not in TUI mode (snapshot requires --tui)", req.Name)}
 	}
-	ptmx, ok := s.ptys[req.Name]
+	handle, ok := s.ptys[req.Name]
 	if !ok {
 		s.mu.Unlock()
 		return Response{Success: false, Error: fmt.Sprintf("session %q PTY not available", req.Name)}
 	}
+	ptmx := handle.File()
 	cmd := s.cmds[req.Name]
 	storage := s.storage
 	s.mu.Unlock()
@@ -793,7 +815,7 @@ func (s *Server) handleSend(req Request) Response {
 		s.mu.Unlock()
 		return Response{Success: false, Error: fmt.Sprintf("session %q is stopped", req.Name)}
 	}
-	ptmx, ok := s.ptys[req.Name]
+	handle, ok := s.ptys[req.Name]
 	s.mu.Unlock()
 
 	if !ok {
@@ -805,7 +827,7 @@ func (s *Server) handleSend(req Request) Response {
 		data += "\n"
 	}
 
-	if _, err := ptmx.WriteString(data); err != nil {
+	if _, err := handle.File().WriteString(data); err != nil {
 		return Response{Success: false, Error: err.Error()}
 	}
 
@@ -830,8 +852,8 @@ func (s *Server) handleStop(req Request) Response {
 		delete(s.doneChans, req.Name)
 	}
 
-	if ptmx, ok := s.ptys[req.Name]; ok {
-		ptmx.Close()
+	if handle, ok := s.ptys[req.Name]; ok {
+		handle.Close()
 		delete(s.ptys, req.Name)
 	}
 
@@ -863,29 +885,25 @@ func (s *Server) handleStop(req Request) Response {
 
 func (s *Server) handleKill(req Request) Response {
 	s.mu.Lock()
-	defer s.mu.Unlock()
 
 	sess, exists := s.sessions[req.Name]
 	if !exists {
+		s.mu.Unlock()
 		return Response{Success: false, Error: fmt.Sprintf("session %q not found", req.Name)}
 	}
 
+	var proc *os.Process
 	if sess.State == StateRunning {
 		if done, ok := s.doneChans[req.Name]; ok {
 			close(done)
 			delete(s.doneChans, req.Name)
 		}
-
-		if ptmx, ok := s.ptys[req.Name]; ok {
-			ptmx.Close()
+		if handle, ok := s.ptys[req.Name]; ok {
+			handle.Close()
 			delete(s.ptys, req.Name)
 		}
-
 		if cmd, ok := s.cmds[req.Name]; ok {
-			cmd.Process.Signal(syscall.SIGTERM)
-			time.Sleep(KillGracePeriod)
-			cmd.Process.Signal(syscall.SIGKILL)
-			cmd.Wait()
+			proc = cmd.Process
 			delete(s.cmds, req.Name)
 		}
 	}
@@ -894,6 +912,16 @@ func (s *Server) handleKill(req Request) Response {
 	delete(s.sessions, req.Name)
 	delete(s.frameDetectors, req.Name)
 	delete(s.responders, req.Name)
+	s.mu.Unlock()
+
+	if proc != nil {
+		go func() {
+			proc.Signal(syscall.SIGTERM)
+			time.Sleep(KillGracePeriod)
+			proc.Signal(syscall.SIGKILL)
+			proc.Wait()
+		}()
+	}
 
 	return Response{Success: true}
 }
@@ -916,6 +944,10 @@ func (s *Server) handleSize(req Request) Response {
 }
 
 func (s *Server) handleSearch(req Request) Response {
+	if req.Before < 0 || req.After < 0 {
+		return Response{Success: false, Error: "before and after must be non-negative"}
+	}
+
 	s.mu.Lock()
 	_, exists := s.sessions[req.Name]
 	if !exists {
@@ -1056,7 +1088,7 @@ func (s *Server) handleResize(req Request) Response {
 		return Response{Success: false, Error: fmt.Sprintf("session %q is stopped", req.Name)}
 	}
 
-	ptmx, ok := s.ptys[req.Name]
+	handle, ok := s.ptys[req.Name]
 	if !ok {
 		s.mu.Unlock()
 		return Response{Success: false, Error: fmt.Sprintf("session %q not running", req.Name)}
@@ -1078,7 +1110,7 @@ func (s *Server) handleResize(req Request) Response {
 		rows = meta.Rows
 	}
 
-	if err := pty.Setsize(ptmx, &pty.Winsize{Cols: clampUint16(cols), Rows: clampUint16(rows)}); err != nil {
+	if err := pty.Setsize(handle.File(), &pty.Winsize{Cols: clampUint16(cols), Rows: clampUint16(rows)}); err != nil {
 		return Response{Success: false, Error: fmt.Sprintf("resize: %v", err)}
 	}
 
diff --git a/internal/mcp/tools.go b/internal/mcp/tools.go
index 57d6920..99925d4 100644
--- a/internal/mcp/tools.go
+++ b/internal/mcp/tools.go
@@ -831,6 +831,10 @@ func (r *ToolRegistry) callSearch(args json.RawMessage) (*CallToolResult, error)
 		after = a.Around
 	}
 
+	if before < 0 || after < 0 {
+		return nil, fmt.Errorf("before, after, and around must be non-negative")
+	}
+
 	resp, err := r.client.Search(daemon.SearchRequest{
 		Name:       a.Name,
 		Pattern:    a.Pattern,