diff --git a/client/internal/routeselector/routeselector.go b/client/internal/routeselector/routeselector.go
index 1254b384d..bfcf71552 100644
--- a/client/internal/routeselector/routeselector.go
+++ b/client/internal/routeselector/routeselector.go
@@ -32,6 +32,23 @@ func (rs *RouteSelector) SelectRoutes(routes []route.NetID, appendRoute bool, al
 	rs.mu.Lock()
 	defer rs.mu.Unlock()
 
+	// Validate before mutating: a non-append selection wipes the current selection first, so
+	// a request naming only unavailable routes would deselect everything the user had and put
+	// nothing in its place. Requesting no routes at all is a different thing - that's the
+	// caller asking to deselect all - and still goes through.
+	var err *multierror.Error
+	available := make([]route.NetID, 0, len(routes))
+	for _, r := range routes {
+		if !slices.Contains(allRoutes, r) {
+			err = multierror.Append(err, fmt.Errorf("route '%s' is not available", r))
+			continue
+		}
+		available = append(available, r)
+	}
+	if len(available) == 0 && err != nil {
+		return errors.FormatErrorOrNil(err)
+	}
+
 	if !appendRoute || rs.deselectAll {
 		if rs.deselectedRoutes == nil {
 			rs.deselectedRoutes = map[route.NetID]struct{}{}
@@ -46,14 +63,9 @@ func (rs *RouteSelector) SelectRoutes(routes []route.NetID, appendRoute bool, al
 		}
 	}
 
-	var err *multierror.Error
-	for _, route := range routes {
-		if !slices.Contains(allRoutes, route) {
-			err = multierror.Append(err, fmt.Errorf("route '%s' is not available", route))
-			continue
-		}
-		delete(rs.deselectedRoutes, route)
-		rs.selectedRoutes[route] = struct{}{}
+	for _, r := range available {
+		delete(rs.deselectedRoutes, r)
+		rs.selectedRoutes[r] = struct{}{}
 	}
 
 	rs.deselectAll = false
diff --git a/client/internal/routeselector/routeselector_test.go b/client/internal/routeselector/routeselector_test.go
index 2b1ba3fb9..3181d90d0 100644
--- a/client/internal/routeselector/routeselector_test.go
+++ b/client/internal/routeselector/routeselector_test.go
@@ -887,3 +887,40 @@ func TestRouteSelector_EnableExitNodeKeepsOtherRoutes(t *testing.T) {
 	assert.True(t, rs.IsSelected("lan1"), "non-exit route must stay selected")
 	assert.True(t, rs.IsSelected("lan2"), "non-exit route must stay selected")
 }
+
+// TestRouteSelector_SelectRoutes_AllUnavailableKeepsSelection covers the destructive case: a
+// non-append selection clears the current selection before applying the requested one, so a
+// request naming only unavailable routes used to leave everything deselected while still
+// returning an error - a typo in a route ID silently dropped the user's exit node. A request
+// with at least one available route keeps applying the valid part (see "Select non-existing
+// route" above); this is only about the all-invalid case.
+func TestRouteSelector_SelectRoutes_AllUnavailableKeepsSelection(t *testing.T) {
+	allRoutes := []route.NetID{"route1", "route2", "route3"}
+
+	rs := routeselector.NewRouteSelector()
+	require.NoError(t, rs.SelectRoutes([]route.NetID{"route1"}, false, allRoutes))
+
+	err := rs.SelectRoutes([]route.NetID{"Route1", "route4"}, false, allRoutes)
+
+	assert.Error(t, err, "an unavailable route ID must still be reported")
+	assert.True(t, rs.IsSelected("route1"), "the previous selection must survive a fully invalid request")
+	for _, id := range []route.NetID{"route2", "route3"} {
+		assert.False(t, rs.IsSelected(id), "no other route may become selected")
+	}
+}
+
+// TestRouteSelector_SelectRoutes_EmptyRequestStillDeselectsAll guards the boundary of the check
+// above: asking for no routes is the caller deselecting everything, not a failed request, so it
+// must keep working.
+func TestRouteSelector_SelectRoutes_EmptyRequestStillDeselectsAll(t *testing.T) {
+	allRoutes := []route.NetID{"route1", "route2", "route3"}
+
+	rs := routeselector.NewRouteSelector()
+	require.NoError(t, rs.SelectRoutes([]route.NetID{"route1"}, false, allRoutes))
+
+	require.NoError(t, rs.SelectRoutes(nil, false, allRoutes))
+
+	for _, id := range allRoutes {
+		assert.False(t, rs.IsSelected(id), "an empty selection request must deselect everything")
+	}
+}