diff --git a/client/internal/pqkem/manager.go b/client/internal/pqkem/manager.go
index 429d38716..cb92a9b2e 100644
--- a/client/internal/pqkem/manager.go
+++ b/client/internal/pqkem/manager.go
@@ -57,7 +57,8 @@ type Transport interface {
 	// Run starts delivering inbound datagrams as (source endpoint, msg) to onInbound
 	// and returns immediately; it runs until Close.
 	Run(onInbound func(src netip.AddrPort, msg []byte))
-	// Close stops delivery and releases the socket.
+	// Close stops delivery, drains any in-flight onInbound callback, and releases the
+	// socket, so no callback is still running when Close returns.
 	Close() error
 }
 
@@ -281,19 +282,25 @@ func (m *Manager) Stop() {
 	// has cancelled here no new Add can race Wait.
 	m.mu.Lock()
 	m.rootCancel()
-	m.mu.Unlock()
-	m.wait.Wait()
-	m.mu.Lock()
 	t := m.transport
 	m.transport = nil
-	m.exchanges = make(map[RemoteID]*exchangeCtl)
-	m.psks = make(map[RemoteID]PSK)
 	m.mu.Unlock()
+
+	// Close and drain the data-path receive loop BEFORE clearing peer state: Close waits
+	// for any in-flight onInbound to return, so no inbound message can derive a PSK into a
+	// cleared map, and the engine only tears the WireGuard interface down after this Stop
+	// returns, so no late SetPresharedKey hits a torn-down device.
 	if t != nil {
 		if err := t.Close(); err != nil {
 			m.logger.Warn("pqkem: closing data-path transport", "err", err)
 		}
 	}
+	m.wait.Wait()
+
+	m.mu.Lock()
+	m.exchanges = make(map[RemoteID]*exchangeCtl)
+	m.psks = make(map[RemoteID]PSK)
+	m.mu.Unlock()
 }
 
 // ---- Signalling channel (host-driven; rides the host's negotiation) ----
diff --git a/client/internal/pqkem_transport.go b/client/internal/pqkem_transport.go
index 920e655c4..7096c9e9d 100644
--- a/client/internal/pqkem_transport.go
+++ b/client/internal/pqkem_transport.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net"
 	"net/netip"
+	"sync"
 
 	log "github.com/sirupsen/logrus"
 )
@@ -20,6 +21,7 @@ const DefaultPort = 51833
 type pqTransport struct {
 	conn *net.UDPConn
 	port int
+	wg   sync.WaitGroup
 }
 
 // newPQTransport binds a UDP socket on the WG overlay IP, preferring DefaultPort and
@@ -58,7 +60,9 @@ func (t *pqTransport) LocalPort() int { return t.port }
 // Run implements pqkem.Transport: the receive loop, delivering each datagram as
 // (source endpoint, msg). Exits when the socket is closed.
 func (t *pqTransport) Run(onInbound func(src netip.AddrPort, msg []byte)) {
+	t.wg.Add(1)
 	go func() {
+		defer t.wg.Done()
 		buf := make([]byte, 2048)
 		for {
 			n, src, err := t.conn.ReadFromUDPAddrPort(buf)
@@ -72,5 +76,10 @@ func (t *pqTransport) Run(onInbound func(src netip.AddrPort, msg []byte)) {
 	}()
 }
 
-// Close implements pqkem.Transport.
-func (t *pqTransport) Close() error { return t.conn.Close() }
+// Close implements pqkem.Transport. It closes the socket (unblocking the read) and drains
+// the receive loop, so no onInbound callback is still running when Close returns.
+func (t *pqTransport) Close() error {
+	err := t.conn.Close()
+	t.wg.Wait()
+	return err
+}