From a23a8fad9afa1db2e5339f6eaf90e89f727bb357 Mon Sep 17 00:00:00 2001
From: rcourtman <courtmanr@gmail.com>
Date: Sat, 11 Jul 2026 19:02:14 +0100
Subject: [PATCH] Addresses #1558

---
 internal/api/router.go                        |  3 +
 .../api/router_set_monitor_agents_test.go     | 58 +++++++++++++++++++
 2 files changed, 61 insertions(+)
 create mode 100644 internal/api/router_set_monitor_agents_test.go

diff --git a/internal/api/router.go b/internal/api/router.go
index 274bb038b..bfaa3bc97 100644
--- a/internal/api/router.go
+++ b/internal/api/router.go
@@ -1361,6 +1361,9 @@ func (r *Router) SetMonitor(m *monitoring.Monitor) {
 	if r.unifiedAgentHandlers != nil {
 		r.unifiedAgentHandlers.SetMonitor(m)
 	}
+	if r.kubernetesAgentHandlers != nil {
+		r.kubernetesAgentHandlers.SetMonitor(m)
+	}
 	if r.systemSettingsHandler != nil {
 		r.systemSettingsHandler.SetMonitor(m)
 	}
diff --git a/internal/api/router_set_monitor_agents_test.go b/internal/api/router_set_monitor_agents_test.go
new file mode 100644
index 000000000..b196c52b9
--- /dev/null
+++ b/internal/api/router_set_monitor_agents_test.go
@@ -0,0 +1,58 @@
+package api
+
+import (
+	"context"
+	"testing"
+
+	"github.com/rcourtman/pulse-go-rewrite/internal/config"
+	"github.com/rcourtman/pulse-go-rewrite/internal/monitoring"
+)
+
+// TestRouterSetMonitor_UpdatesAgentHandlers verifies the fix for issue #1558:
+// Router.SetMonitor must repoint the kubernetes agent handlers at the new
+// monitor, exactly as it does for the docker agent handlers. Without this,
+// kubernetes agent reports resolved through the single-tenant fallback keep
+// landing in the orphaned pre-reload monitor after a config reload, so the
+// cluster flaps in the UI.
+func TestRouterSetMonitor_UpdatesAgentHandlers(t *testing.T) {
+	tempDir := t.TempDir()
+	cfg := &config.Config{
+		DataPath:   tempDir,
+		ConfigPath: tempDir,
+	}
+
+	monitor1, err := monitoring.New(cfg)
+	if err != nil {
+		t.Fatalf("monitoring.New (initial): %v", err)
+	}
+	t.Cleanup(func() { monitor1.Stop() })
+
+	monitor2, err := monitoring.New(cfg)
+	if err != nil {
+		t.Fatalf("monitoring.New (reload): %v", err)
+	}
+	t.Cleanup(func() { monitor2.Stop() })
+
+	// No multi-tenant monitor: getMonitor resolves via the defaultMonitor
+	// fallback, which is exactly the field SetMonitor must refresh.
+	kubernetesHandlers := NewKubernetesAgentHandlers(nil, monitor1, nil)
+	dockerHandlers := NewDockerAgentHandlers(nil, monitor1, nil, cfg)
+
+	// Minimal router, as in TestReloadSystemSettings_AppliesWebhookCIDRsToNewMonitor:
+	// SetMonitor only touches the handlers that are non-nil.
+	router := &Router{
+		config:                  cfg,
+		kubernetesAgentHandlers: kubernetesHandlers,
+		dockerAgentHandlers:     dockerHandlers,
+	}
+
+	router.SetMonitor(monitor2)
+
+	ctx := context.Background()
+	if got := kubernetesHandlers.getMonitor(ctx); got != monitor2 {
+		t.Fatal("kubernetes agent handlers still resolve the pre-reload monitor after Router.SetMonitor")
+	}
+	if got := dockerHandlers.getMonitor(ctx); got != monitor2 {
+		t.Fatal("docker agent handlers still resolve the pre-reload monitor after Router.SetMonitor")
+	}
+}