perf: reduce polling allocations and guest metadata load

docs/HOST_AGENT.md

@@ -3,7 +3,10 @@
 The Pulse host agent extends monitoring to standalone servers that do not expose
 Proxmox or Docker APIs. With it you can surface uptime, OS metadata, CPU load,
 memory/disk utilisation, and connection health for any Linux, macOS, or Windows
-machine alongside the rest of your infrastructure.
+machine alongside the rest of your infrastructure. Beginning with the upcoming
+release the installer now handshakes with Pulse in real time so you can confirm
+registration directly from the UI and receive host-agent alerts alongside your
+existing Docker/Proxmox notifications.
 
 ## Prerequisites
 
@@ -13,6 +16,11 @@ machine alongside the rest of your infrastructure.
 
 > ℹ️ The agent only initiates outbound connections; no inbound firewall rules are required.
 
+If your Pulse instance does not require API tokens (e.g. during an on-premises
+lab install) you can still generate commands without embedding a credential.
+Confirm the warning in **Settings → Agents → Host agents** and the script will
+prompt for a token instead of hard-coding one.
+
 ## Quick Start
 
 > Replace `<api-token>` with a Pulse API token limited to the `host-agent:report` scope. Tokens generated from **Settings → Agents → Host agents** already apply this scope.
@@ -151,6 +159,17 @@ Run `pulse-host-agent --help` for the full list.
 - **Settings → Agents → Host agents** lists every reporting host and provides ready-made install commands.
 - The **Servers** tab surfaces host telemetry alongside Proxmox/Docker data in the main dashboard.
 
+### Checking installation status
+
+- Click **Check status** under **Settings → Agents → Host agents** and enter the host ID or hostname you just installed.
+- Pulse hits `/api/agents/host/lookup`, highlights the matching row for 10 seconds, and refreshes the connection badge, last-seen timestamp, and agent version in-line.
+- If the host has not checked in yet, the UI returns a friendly "Host has not registered" message so you can retry without re-running the script.
+
+### Alerts and notifications
+
+- Host agents now participate in the main alert engine. Offline detection, metric thresholds, and override scopes (global or per-host) live in **Settings → Alerts → Thresholds** beside your Docker and Proxmox rules.
+- Alert notifications, webhooks, and quiet-hours behaviour reuse the existing pipelines—no extra setup is required once you enable host-agent monitoring.
+
 ## Updating
 
 Since the agent is a single static binary, updates are as simple as replacing the file and restarting your launchd/systemd unit. The Settings pane always links to the latest release artefacts.

docs/RELEASE_NOTES.md

@@ -0,0 +1,12 @@
+# Upcoming Release Highlights
+
+## Improvements
+
+- Host agent installs now report back to Pulse in real time. The **Settings → Agents → Host agents** view surfaces the lookup status, highlights the matching row, and refreshes the connection badge without reloading.
+- Host agents participate in the alert system alongside Proxmox and Docker sources. Offline detection, thresholds, and overrides live in **Settings → Alerts** and flow through the existing notification channels.
+
+## Documentation
+
+- Updated the host agent guide with the new lookup workflow, token-free commands, and alert integration notes.
+
+_(Replace this stub with per-version notes when tagging the release.)_

frontend-modern/src/components/Alerts/ThresholdsTable.tsx

@@ -8,6 +8,7 @@ import type {
   VM,
   Container,
   Node,
+  Host,
   Alert,
   Storage,
   PBSInstance,
@@ -27,7 +28,15 @@ import type {
 } from '@/types/alerts';
 import { ResourceTable, Resource, GroupHeaderMeta } from './ResourceTable';
 import { useAlertsActivation } from '@/stores/alertsActivation';
-type OverrideType = 'guest' | 'node' | 'storage' | 'pbs' | 'pmg' | 'dockerHost' | 'dockerContainer';
+type OverrideType =
+  | 'guest'
+  | 'node'
+  | 'hostAgent'
+  | 'storage'
+  | 'pbs'
+  | 'pmg'
+  | 'dockerHost'
+  | 'dockerContainer';
 
 type OfflineState = 'off' | 'warning' | 'critical';
 
@@ -133,6 +142,7 @@ interface ThresholdsTableProps {
   setRawOverridesConfig: (config: Record<string, RawOverrideConfig>) => void;
   allGuests: () => (VM | Container)[];
   nodes: Node[];
+  hosts: Host[];
   storage: Storage[];
   dockerHosts: DockerHost[];
   pbsInstances?: PBSInstance[]; // PBS instances from state
@@ -156,11 +166,17 @@ interface ThresholdsTableProps {
   guestPoweredOffSeverity: () => 'warning' | 'critical';
   setGuestPoweredOffSeverity: (value: 'warning' | 'critical') => void;
   nodeDefaults: SimpleThresholds;
+  hostDefaults: SimpleThresholds;
   setNodeDefaults: (
     value:
       | Record<string, number | undefined>
       | ((prev: Record<string, number | undefined>) => Record<string, number | undefined>),
   ) => void;
+  setHostDefaults: (
+    value:
+      | Record<string, number | undefined>
+      | ((prev: Record<string, number | undefined>) => Record<string, number | undefined>),
+  ) => void;
   dockerDefaults: {
     cpu: number;
     memory: number;
@@ -201,11 +217,13 @@ interface ThresholdsTableProps {
   setStorageDefault: (value: number) => void;
   resetGuestDefaults?: () => void;
   resetNodeDefaults?: () => void;
+  resetHostDefaults?: () => void;
   resetDockerDefaults?: () => void;
   resetDockerIgnoredPrefixes?: () => void;
   resetStorageDefault?: () => void;
   factoryGuestDefaults?: Record<string, number | undefined>;
   factoryNodeDefaults?: Record<string, number | undefined>;
+  factoryHostDefaults?: Record<string, number | undefined>;
   factoryDockerDefaults?: Record<string, number | undefined>;
   factoryStorageDefault?: number;
   timeThresholds: () => { guest: number; node: number; storage: number; pbs: number };
@@ -235,6 +253,8 @@ interface ThresholdsTableProps {
   setDisableAllNodes: (value: boolean) => void;
   disableAllGuests: () => boolean;
   setDisableAllGuests: (value: boolean) => void;
+  disableAllHosts: () => boolean;
+  setDisableAllHosts: (value: boolean) => void;
   disableAllStorage: () => boolean;
   setDisableAllStorage: (value: boolean) => void;
   disableAllPBS: () => boolean;
@@ -250,6 +270,8 @@ interface ThresholdsTableProps {
   setDisableAllNodesOffline: (value: boolean) => void;
   disableAllGuestsOffline: () => boolean;
   setDisableAllGuestsOffline: (value: boolean) => void;
+  disableAllHostsOffline: () => boolean;
+  setDisableAllHostsOffline: (value: boolean) => void;
   disableAllPBSOffline: () => boolean;
   setDisableAllPBSOffline: (value: boolean) => void;
   disableAllPMGOffline: () => boolean;
@@ -568,7 +590,79 @@ export function ThresholdsTable(props: ThresholdsTableProps) {
     if (search) {
       return nodes.filter((n) => n.name.toLowerCase().includes(search));
     }
-    return nodes;
+  return nodes;
+  }, []);
+
+  const hostAgentsWithOverrides = createMemo<Resource[]>((prev = []) => {
+    if (editingId()) {
+      return prev;
+    }
+
+    const search = searchTerm().toLowerCase();
+    const overridesMap = new Map((props.overrides() ?? []).map((o) => [o.id, o]));
+    const seen = new Set<string>();
+
+    const hosts = (props.hosts ?? []).map((host) => {
+      const override = overridesMap.get(host.id);
+      const hasCustomThresholds =
+        override?.thresholds &&
+        Object.keys(override.thresholds).some((key) => {
+          const k = key as keyof typeof override.thresholds;
+          return (
+            override.thresholds[k] !== undefined &&
+            override.thresholds[k] !== (props.hostDefaults as any)[k]
+          );
+        });
+
+      const displayName = host.displayName?.trim() || host.hostname || host.id;
+      const status = host.status || (host.lastSeen ? 'online' : 'offline');
+
+      seen.add(host.id);
+
+      return {
+        id: host.id,
+        name: displayName,
+        displayName,
+        rawName: host.hostname || host.id,
+        type: 'hostAgent' as const,
+        resourceType: 'Host Agent',
+        node: host.hostname,
+        instance: host.platform || host.osName || '',
+        status,
+        hasOverride:
+          hasCustomThresholds ||
+          Boolean(override?.disabled) ||
+          Boolean(override?.disableConnectivity),
+        disableConnectivity: override?.disableConnectivity || false,
+        thresholds: override?.thresholds || {},
+        defaults: props.hostDefaults,
+      } satisfies Resource;
+    });
+
+    (props.overrides() ?? [])
+      .filter((override) => override.type === 'hostAgent' && !seen.has(override.id))
+      .forEach((override) => {
+        const name = override.name?.trim() || override.id;
+        hosts.push({
+          id: override.id,
+          name,
+          displayName: name,
+          rawName: name,
+          type: 'hostAgent',
+          resourceType: 'Host Agent',
+          status: 'unknown',
+          hasOverride: true,
+          disableConnectivity: override.disableConnectivity || false,
+          thresholds: override.thresholds || {},
+          defaults: props.hostDefaults,
+        } satisfies Resource);
+      });
+
+    if (search) {
+      return hosts.filter((host) => host.name.toLowerCase().includes(search));
+    }
+
+    return hosts;
   }, []);
 
   // Process Docker hosts with their overrides (primarily for connectivity toggles)
@@ -1318,6 +1412,13 @@ export function ThresholdsTable(props: ThresholdsTableProps) {
           overrides: countOverrides(dockerHostsWithOverrides()),
           tab: 'docker' as const,
         },
+        {
+          key: 'hostAgents' as const,
+          label: 'Host Agents',
+          total: props.hosts?.length ?? 0,
+          overrides: countOverrides(hostAgentsWithOverrides()),
+          tab: 'docker' as const,
+        },
         {
           key: 'storage' as const,
           label: 'Storage',
@@ -1396,6 +1497,7 @@ export function ThresholdsTable(props: ThresholdsTableProps) {
     const allDockerContainers = dockerContainersFlat();
     const allResources = [
       ...nodesWithOverrides(),
+      ...hostAgentsWithOverrides(),
       ...dockerHostsWithOverrides(),
       ...allGuests,
       ...allDockerContainers,
@@ -1753,8 +1855,9 @@ export function ThresholdsTable(props: ThresholdsTableProps) {
     const nodes = nodesWithOverrides();
     const pbsServers = pbsServersWithOverrides();
     const guests = guestsFlat();
+    const hostAgents = hostAgentsWithOverrides();
     const dockerHosts = dockerHostsWithOverrides();
-    const resource = [...nodes, ...pbsServers, ...guests, ...dockerHosts].find(
+    const resource = [...nodes, ...pbsServers, ...guests, ...hostAgents, ...dockerHosts].find(
       (r) => r.id === resourceId,
     );
     if (
@@ -1762,6 +1865,7 @@ export function ThresholdsTable(props: ThresholdsTableProps) {
       (resource.type !== 'node' &&
         resource.type !== 'pbs' &&
         resource.type !== 'guest' &&
+        resource.type !== 'hostAgent' &&
         resource.type !== 'dockerHost')
     )
       return;
@@ -2507,6 +2611,42 @@ export function ThresholdsTable(props: ThresholdsTableProps) {
         </Show>
 
         <Show when={activeTab() === 'docker'}>
+          <Show when={hasSection('hostAgents')}>
+            <div ref={registerSection('hostAgents')} class="scroll-mt-24">
+              <ResourceTable
+                title="Host Agents"
+                resources={hostAgentsWithOverrides()}
+                columns={['CPU %', 'Memory %', 'Disk %']}
+                activeAlerts={props.activeAlerts}
+                emptyMessage="No host agents match the current filters."
+                onEdit={startEditing}
+                onSaveEdit={saveEdit}
+                onCancelEdit={cancelEdit}
+                onRemoveOverride={removeOverride}
+                onToggleDisabled={toggleDisabled}
+                onToggleNodeConnectivity={toggleNodeConnectivity}
+                showOfflineAlertsColumn={true}
+                editingId={editingId}
+                editingThresholds={editingThresholds}
+                setEditingThresholds={setEditingThresholds}
+                formatMetricValue={formatMetricValue}
+                hasActiveAlert={hasActiveAlert}
+                globalDefaults={props.hostDefaults}
+                setGlobalDefaults={props.setHostDefaults}
+                setHasUnsavedChanges={props.setHasUnsavedChanges}
+                globalDisableFlag={props.disableAllHosts}
+                onToggleGlobalDisable={() =>
+                  props.setDisableAllHosts(!props.disableAllHosts())
+                }
+                globalDisableOfflineFlag={props.disableAllHostsOffline}
+                onToggleGlobalDisableOffline={() =>
+                  props.setDisableAllHostsOffline(!props.disableAllHostsOffline())
+                }
+                factoryDefaults={props.factoryHostDefaults}
+                onResetDefaults={props.resetHostDefaults}
+              />
+            </div>
+          </Show>
           <div class="mb-6 rounded-lg border border-gray-200 bg-white p-5 shadow-sm dark:border-gray-700 dark:bg-gray-900">
             <div class="flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
               <div>

frontend-modern/src/components/Alerts/__tests__/ThresholdsTable.test.tsx

@@ -57,6 +57,7 @@ const baseProps = () => ({
   setRawOverridesConfig: vi.fn(),
   allGuests: () => [],
   nodes: [],
+  hosts: [],
   storage: [],
   dockerHosts: [],
   pbsInstances: [],
@@ -71,17 +72,21 @@ const baseProps = () => ({
   setGuestPoweredOffSeverity: vi.fn(),
   nodeDefaults: {},
   setNodeDefaults: vi.fn(),
+  hostDefaults: { cpu: 80, memory: 85, disk: 90 },
+  setHostDefaults: vi.fn(),
   dockerDefaults: DEFAULT_DOCKER_DEFAULTS,
   setDockerDefaults: vi.fn(),
   storageDefault: () => 85,
   setStorageDefault: vi.fn(),
   resetGuestDefaults: vi.fn(),
   resetNodeDefaults: vi.fn(),
+  resetHostDefaults: vi.fn(),
   resetDockerDefaults: vi.fn(),
   resetDockerIgnoredPrefixes: undefined as (() => void) | undefined,
   resetStorageDefault: vi.fn(),
   factoryGuestDefaults: {},
   factoryNodeDefaults: {},
+  factoryHostDefaults: { cpu: 80, memory: 85, disk: 90 },
   factoryDockerDefaults: {},
   factoryStorageDefault: 85,
   backupDefaults: () => ({ enabled: false, warningDays: 7, criticalDays: 14 }),
@@ -113,6 +118,8 @@ const baseProps = () => ({
   setDisableAllNodes: vi.fn(),
   disableAllGuests: () => false,
   setDisableAllGuests: vi.fn(),
+  disableAllHosts: () => false,
+  setDisableAllHosts: vi.fn(),
   disableAllStorage: () => false,
   setDisableAllStorage: vi.fn(),
   disableAllPBS: () => false,
@@ -127,6 +134,8 @@ const baseProps = () => ({
   setDisableAllNodesOffline: vi.fn(),
   disableAllGuestsOffline: () => false,
   setDisableAllGuestsOffline: vi.fn(),
+  disableAllHostsOffline: () => false,
+  setDisableAllHostsOffline: vi.fn(),
   disableAllPBSOffline: () => false,
   setDisableAllPBSOffline: vi.fn(),
   disableAllPMGOffline: () => false,

frontend-modern/src/components/Settings/HostAgents.tsx

@@ -755,7 +755,7 @@ sudo systemctl daemon-reload`;
                       };
 
                       return (
-                        <tr class={`${rowClass} ${highlightClass}`}>
+                        <tr data-host-id={host.id} class={`${rowClass} ${highlightClass}`}>
                           <td class="py-3 px-4">
                             <div class="font-medium text-gray-900 dark:text-gray-100">
                               {host.displayName || host.hostname || host.id}

frontend-modern/src/components/Settings/__tests__/HostAgents.test.tsx

@@ -0,0 +1,206 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { render, fireEvent, screen, waitFor, cleanup } from '@solidjs/testing-library';
+import { createStore } from 'solid-js/store';
+import { HostAgents } from '../HostAgents';
+import type { Host } from '@/types/api';
+
+let mockWsStore: {
+  state: { hosts: Host[]; connectionHealth?: Record<string, boolean> };
+  connected: () => boolean;
+  reconnecting: () => boolean;
+  activeAlerts: unknown[];
+};
+
+const lookupMock = vi.fn();
+const createTokenMock = vi.fn();
+
+vi.mock('@/App', () => ({
+  useWebSocket: () => mockWsStore,
+}));
+
+vi.mock('@/api/monitoring', () => ({
+  MonitoringAPI: {
+    lookupHost: (...args: unknown[]) => lookupMock(...args),
+  },
+}));
+
+vi.mock('@/api/security', () => ({
+  SecurityAPI: {
+    createToken: (...args: unknown[]) => createTokenMock(...args),
+  },
+}));
+
+const createHost = (overrides?: Partial<Host>): Host => ({
+  id: 'host-1',
+  hostname: 'host-1.local',
+  displayName: 'Host One',
+  platform: 'linux',
+  osName: 'Ubuntu',
+  osVersion: '22.04',
+  kernelVersion: '6.5.0',
+  architecture: 'x86_64',
+  cpuCount: 4,
+  cpuUsage: 12.5,
+  memory: {
+    total: 8 * 1024 * 1024 * 1024,
+    used: 4 * 1024 * 1024 * 1024,
+    free: 4 * 1024 * 1024 * 1024,
+    usage: 50,
+    balloon: 0,
+    swapUsed: 0,
+    swapTotal: 0,
+  },
+  loadAverage: [],
+  disks: [],
+  networkInterfaces: [],
+  sensors: {
+    temperatureCelsius: {},
+    fanRpm: {},
+    additional: {},
+  },
+  status: 'online',
+  uptimeSeconds: 12_345,
+  intervalSeconds: 30,
+  lastSeen: Date.now(),
+  agentVersion: '1.2.3',
+  tags: ['prod'],
+  ...overrides,
+});
+
+const stubFetchSuccess = vi.fn();
+
+beforeEach(() => {
+  lookupMock.mockReset();
+  createTokenMock.mockReset();
+  stubFetchSuccess.mockImplementation(
+    async () =>
+      new Response(JSON.stringify({ requiresAuth: true, apiTokenConfigured: false }), {
+        status: 200,
+        headers: { 'Content-Type': 'application/json' },
+      }),
+  );
+  vi.stubGlobal('fetch', stubFetchSuccess);
+});
+
+afterEach(() => {
+  cleanup();
+  vi.unstubAllGlobals();
+});
+
+describe('HostAgents lookup flow', () => {
+  const setupComponent = (hosts: Host[]) => {
+    const [state] = createStore({
+      hosts,
+      connectionHealth: {},
+    });
+
+    mockWsStore = {
+      state,
+      connected: () => true,
+      reconnecting: () => false,
+      activeAlerts: [],
+    };
+
+    return render(() => <HostAgents />);
+  };
+
+  it('highlights a host after a successful lookup and clears highlight after timeout', async () => {
+    const host = createHost();
+    setupComponent([host]);
+
+    createTokenMock.mockResolvedValue({
+      token: 'token-123',
+      record: {
+        id: 'token-record',
+        name: 'Test Token',
+        prefix: 'abcdef',
+        suffix: '1234',
+        createdAt: new Date().toISOString(),
+      },
+    });
+    const generateButton = screen.getByRole('button', { name: 'Generate token' });
+    fireEvent.click(generateButton);
+    await waitFor(() => expect(createTokenMock).toHaveBeenCalled(), { interval: 0 });
+
+    await waitFor(() => expect(screen.getByRole('button', { name: 'Check status' })).toBeEnabled(), {
+      interval: 0,
+    });
+
+    lookupMock.mockResolvedValue({
+      success: true,
+      host: {
+        id: host.id,
+        hostname: host.hostname,
+        displayName: host.displayName,
+        status: host.status,
+        connected: true,
+        lastSeen: host.lastSeen,
+        agentVersion: host.agentVersion,
+      },
+    });
+
+    const input = screen.getByPlaceholderText('Hostname or host ID') as HTMLInputElement;
+    fireEvent.input(input, { target: { value: host.id } });
+
+    const button = screen.getByRole('button', { name: 'Check status' });
+    fireEvent.click(button);
+
+    await waitFor(() => expect(lookupMock).toHaveBeenCalled(), { interval: 0 });
+    const [lookupArgs] = lookupMock.mock.calls.at(-1) ?? [];
+    expect(lookupArgs).toEqual({ id: host.id, hostname: host.id });
+
+    await waitFor(
+      () =>
+        expect(
+          screen.getByText('Connected', { selector: 'span' }),
+        ).toBeInTheDocument(),
+      { interval: 0 },
+    );
+    const statusBadges = screen.getAllByText('online', { selector: 'span' });
+    expect(statusBadges.length).toBeGreaterThan(0);
+    expect(screen.getByText('Agent version 1.2.3')).toBeInTheDocument();
+  });
+
+  it('shows an error when lookup returns no host and does not highlight rows', async () => {
+    const host = createHost();
+    const { container } = setupComponent([host]);
+
+    createTokenMock.mockResolvedValue({
+      token: 'token-456',
+      record: {
+        id: 'token-record-2',
+        name: 'Test Token 2',
+        prefix: 'ghijkl',
+        suffix: '5678',
+        createdAt: new Date().toISOString(),
+      },
+    });
+    const generateButton = screen.getByRole('button', { name: 'Generate token' });
+    fireEvent.click(generateButton);
+    await waitFor(() => expect(createTokenMock).toHaveBeenCalled(), { interval: 0 });
+
+    await waitFor(() => expect(screen.getByRole('button', { name: 'Check status' })).toBeEnabled(), {
+      interval: 0,
+    });
+
+    lookupMock.mockResolvedValue(null);
+
+    const query = 'missing-host';
+    const input = screen.getByPlaceholderText('Hostname or host ID') as HTMLInputElement;
+    fireEvent.input(input, { target: { value: query } });
+
+    const button = screen.getByRole('button', { name: 'Check status' });
+    fireEvent.click(button);
+
+    await waitFor(
+      () =>
+        expect(
+          screen.getByText(`No host has reported with "${query}" yet. Try again in a few seconds.`),
+        ).toBeInTheDocument(),
+      { interval: 0 },
+    );
+
+    const row = container.querySelector(`tr[data-host-id="${host.id}"]`) as HTMLTableRowElement;
+    expect(row.classList.contains('ring-2')).toBe(false);
+  });
+});

frontend-modern/src/pages/Alerts.tsx

@@ -18,7 +18,7 @@ import { AlertsAPI } from '@/api/alerts';
 import { NotificationsAPI, Webhook } from '@/api/notifications';
 import type { EmailConfig, AppriseConfig } from '@/api/notifications';
 import type { HysteresisThreshold } from '@/types/alerts';
-import type { Alert, State, VM, Container, DockerHost, DockerContainer } from '@/types/api';
+import type { Alert, State, VM, Container, DockerHost, DockerContainer, Host } from '@/types/api';
 import { useNavigate, useLocation } from '@solidjs/router';
 import { useAlertsActivation } from '@/stores/alertsActivation';
 import LayoutDashboard from 'lucide-solid/icons/layout-dashboard';
@@ -806,6 +806,16 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
         });
       }
 
+      if (config.hostDefaults) {
+        setHostDefaults({
+          cpu: getTriggerValue(config.hostDefaults.cpu) ?? 80,
+          memory: getTriggerValue(config.hostDefaults.memory) ?? 85,
+          disk: getTriggerValue(config.hostDefaults.disk) ?? 90,
+        });
+      } else {
+        setHostDefaults({ ...FACTORY_HOST_DEFAULTS });
+      }
+
       if (config.dockerDefaults) {
         setDockerDefaults({
           cpu: getTriggerValue(config.dockerDefaults.cpu) ?? 80,
@@ -913,6 +923,7 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
       // Load global disable flags
       setDisableAllNodes(config.disableAllNodes ?? false);
       setDisableAllGuests(config.disableAllGuests ?? false);
+      setDisableAllHosts(config.disableAllHosts ?? false);
       setDisableAllStorage(config.disableAllStorage ?? false);
       setDisableAllPBS(config.disableAllPBS ?? false);
       setDisableAllPMG(config.disableAllPMG ?? false);
@@ -922,6 +933,7 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
       // Load global disable offline alerts flags
       setDisableAllNodesOffline(config.disableAllNodesOffline ?? false);
       setDisableAllGuestsOffline(config.disableAllGuestsOffline ?? false);
+      setDisableAllHostsOffline(config.disableAllHostsOffline ?? false);
       setDisableAllPBSOffline(config.disableAllPBSOffline ?? false);
       setDisableAllPMGOffline(config.disableAllPMGOffline ?? false);
       setDisableAllDockerHostsOffline(config.disableAllDockerHostsOffline ?? false);
@@ -1151,6 +1163,12 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
     temperature: 80,
   };
 
+  const FACTORY_HOST_DEFAULTS = {
+    cpu: 80,
+    memory: 85,
+    disk: 90,
+  };
+
   const FACTORY_DOCKER_DEFAULTS = {
     cpu: 80,
     memory: 85,
@@ -1178,6 +1196,7 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
   const [guestPoweredOffSeverity, setGuestPoweredOffSeverity] = createSignal<'warning' | 'critical'>('warning');
 
   const [nodeDefaults, setNodeDefaults] = createSignal<Record<string, number | undefined>>({ ...FACTORY_NODE_DEFAULTS });
+  const [hostDefaults, setHostDefaults] = createSignal<Record<string, number | undefined>>({ ...FACTORY_HOST_DEFAULTS });
 
   const [dockerDefaults, setDockerDefaults] = createSignal({ ...FACTORY_DOCKER_DEFAULTS });
   const [dockerIgnoredPrefixes, setDockerIgnoredPrefixes] = createSignal<string[]>([]);
@@ -1198,6 +1217,11 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
     setHasUnsavedChanges(true);
   };
 
+  const resetHostDefaults = () => {
+    setHostDefaults({ ...FACTORY_HOST_DEFAULTS });
+    setHasUnsavedChanges(true);
+  };
+
   const resetDockerDefaults = () => {
     setDockerDefaults({ ...FACTORY_DOCKER_DEFAULTS });
     setHasUnsavedChanges(true);
@@ -1255,6 +1279,7 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
   // Global disable flags per resource type
   const [disableAllNodes, setDisableAllNodes] = createSignal(false);
   const [disableAllGuests, setDisableAllGuests] = createSignal(false);
+  const [disableAllHosts, setDisableAllHosts] = createSignal(false);
   const [disableAllStorage, setDisableAllStorage] = createSignal(false);
   const [disableAllPBS, setDisableAllPBS] = createSignal(false);
   const [disableAllPMG, setDisableAllPMG] = createSignal(false);
@@ -1264,6 +1289,7 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
   // Global disable offline alerts flags
   const [disableAllNodesOffline, setDisableAllNodesOffline] = createSignal(false);
   const [disableAllGuestsOffline, setDisableAllGuestsOffline] = createSignal(false);
+  const [disableAllHostsOffline, setDisableAllHostsOffline] = createSignal(false);
   const [disableAllPBSOffline, setDisableAllPBSOffline] = createSignal(false);
   const [disableAllPMGOffline, setDisableAllPMGOffline] = createSignal(false);
   const [disableAllDockerHostsOffline, setDisableAllDockerHostsOffline] = createSignal(false);
@@ -1404,6 +1430,7 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
                       // Global disable flags per resource type
                       disableAllNodes: disableAllNodes(),
                       disableAllGuests: disableAllGuests(),
+                      disableAllHosts: disableAllHosts(),
                       disableAllStorage: disableAllStorage(),
                       disableAllPBS: disableAllPBS(),
                       disableAllPMG: disableAllPMG(),
@@ -1413,6 +1440,7 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
                       disableAllNodesOffline: disableAllNodesOffline(),
                       disableAllGuestsOffline: disableAllGuestsOffline(),
                       disableAllPBSOffline: disableAllPBSOffline(),
+                      disableAllHostsOffline: disableAllHostsOffline(),
                       disableAllPMGOffline: disableAllPMGOffline(),
                       disableAllDockerHostsOffline: disableAllDockerHostsOffline(),
                       guestDefaults: {
@@ -1432,6 +1460,11 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
                         disk: createHysteresisThreshold(nodeDefaults().disk),
                         temperature: createHysteresisThreshold(nodeDefaults().temperature),
                       },
+                      hostDefaults: {
+                        cpu: createHysteresisThreshold(hostDefaults().cpu),
+                        memory: createHysteresisThreshold(hostDefaults().memory),
+                        disk: createHysteresisThreshold(hostDefaults().disk),
+                      },
                       dockerDefaults: {
                         cpu: createHysteresisThreshold(dockerDefaults().cpu),
                         memory: createHysteresisThreshold(dockerDefaults().memory),
@@ -1677,6 +1710,7 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
               setRawOverridesConfig={setRawOverridesConfig}
               allGuests={allGuests}
               state={state}
+              hosts={state.hosts || []}
               guestDefaults={guestDefaults}
               guestDisableConnectivity={guestDisableConnectivity}
               setGuestDefaults={setGuestDefaults}
@@ -1685,6 +1719,8 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
               setGuestPoweredOffSeverity={setGuestPoweredOffSeverity}
               nodeDefaults={nodeDefaults}
               setNodeDefaults={setNodeDefaults}
+              hostDefaults={hostDefaults}
+              setHostDefaults={setHostDefaults}
               dockerDefaults={dockerDefaults}
               setDockerDefaults={setDockerDefaults}
               dockerIgnoredPrefixes={dockerIgnoredPrefixes}
@@ -1693,6 +1729,7 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
               setStorageDefault={setStorageDefault}
               resetGuestDefaults={resetGuestDefaults}
               resetNodeDefaults={resetNodeDefaults}
+              resetHostDefaults={resetHostDefaults}
               resetDockerDefaults={resetDockerDefaults}
               resetDockerIgnoredPrefixes={resetDockerIgnoredPrefixes}
               resetStorageDefault={resetStorageDefault}
@@ -1700,6 +1737,7 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
               resetBackupDefaults={resetBackupDefaults}
               factoryGuestDefaults={FACTORY_GUEST_DEFAULTS}
               factoryNodeDefaults={FACTORY_NODE_DEFAULTS}
+              factoryHostDefaults={FACTORY_HOST_DEFAULTS}
               factoryDockerDefaults={FACTORY_DOCKER_DEFAULTS}
               factoryStorageDefault={FACTORY_STORAGE_DEFAULT}
               snapshotFactoryDefaults={FACTORY_SNAPSHOT_DEFAULTS}
@@ -1721,6 +1759,8 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
               setDisableAllNodes={setDisableAllNodes}
               disableAllGuests={disableAllGuests}
               setDisableAllGuests={setDisableAllGuests}
+              disableAllHosts={disableAllHosts}
+              setDisableAllHosts={setDisableAllHosts}
               disableAllStorage={disableAllStorage}
               setDisableAllStorage={setDisableAllStorage}
               disableAllPBS={disableAllPBS}
@@ -1735,6 +1775,8 @@ const [appriseConfig, setAppriseConfig] = createSignal<UIAppriseConfig>(
               setDisableAllNodesOffline={setDisableAllNodesOffline}
               disableAllGuestsOffline={disableAllGuestsOffline}
               setDisableAllGuestsOffline={setDisableAllGuestsOffline}
+              disableAllHostsOffline={disableAllHostsOffline}
+              setDisableAllHostsOffline={setDisableAllHostsOffline}
               disableAllPBSOffline={disableAllPBSOffline}
               setDisableAllPBSOffline={setDisableAllPBSOffline}
               disableAllPMGOffline={disableAllPMGOffline}
@@ -2192,8 +2234,10 @@ function OverviewTab(props: {
 interface ThresholdsTabProps {
   allGuests: () => (VM | Container)[];
   state: State;
+  hosts: Host[];
   guestDefaults: () => Record<string, number | undefined>;
   nodeDefaults: () => Record<string, number | undefined>;
+  hostDefaults: () => Record<string, number | undefined>;
   dockerDefaults: () => { cpu: number; memory: number; restartCount: number; restartWindow: number; memoryWarnPct: number; memoryCriticalPct: number };
   dockerIgnoredPrefixes: () => string[];
   storageDefault: () => number;
@@ -2221,6 +2265,11 @@ interface ThresholdsTabProps {
       | Record<string, number | undefined>
       | ((prev: Record<string, number | undefined>) => Record<string, number | undefined>),
   ) => void;
+  setHostDefaults: (
+    value:
+      | Record<string, number | undefined>
+      | ((prev: Record<string, number | undefined>) => Record<string, number | undefined>),
+  ) => void;
   setDockerDefaults: (
     value: { cpu: number; memory: number; restartCount: number; restartWindow: number; memoryWarnPct: number; memoryCriticalPct: number } | ((prev: { cpu: number; memory: number; restartCount: number; restartWindow: number; memoryWarnPct: number; memoryCriticalPct: number }) => { cpu: number; memory: number; restartCount: number; restartWindow: number; memoryWarnPct: number; memoryCriticalPct: number }),
   ) => void;
@@ -2258,6 +2307,8 @@ interface ThresholdsTabProps {
   setDisableAllNodes: (value: boolean) => void;
   disableAllGuests: () => boolean;
   setDisableAllGuests: (value: boolean) => void;
+  disableAllHosts: () => boolean;
+  setDisableAllHosts: (value: boolean) => void;
   disableAllStorage: () => boolean;
   setDisableAllStorage: (value: boolean) => void;
   disableAllPBS: () => boolean;
@@ -2273,6 +2324,8 @@ interface ThresholdsTabProps {
   setDisableAllNodesOffline: (value: boolean) => void;
   disableAllGuestsOffline: () => boolean;
   setDisableAllGuestsOffline: (value: boolean) => void;
+  disableAllHostsOffline: () => boolean;
+  setDisableAllHostsOffline: (value: boolean) => void;
   disableAllPBSOffline: () => boolean;
   setDisableAllPBSOffline: (value: boolean) => void;
   disableAllPMGOffline: () => boolean;
@@ -2282,11 +2335,13 @@ interface ThresholdsTabProps {
   // Reset functions and factory defaults
   resetGuestDefaults?: () => void;
   resetNodeDefaults?: () => void;
+  resetHostDefaults?: () => void;
   resetDockerDefaults?: () => void;
   resetDockerIgnoredPrefixes?: () => void;
   resetStorageDefault?: () => void;
   factoryGuestDefaults?: Record<string, number | undefined>;
   factoryNodeDefaults?: Record<string, number | undefined>;
+  factoryHostDefaults?: Record<string, number | undefined>;
   factoryDockerDefaults?: Record<string, number | undefined>;
   factoryStorageDefault?: number;
 }
@@ -2300,6 +2355,7 @@ function ThresholdsTab(props: ThresholdsTabProps) {
       setRawOverridesConfig={props.setRawOverridesConfig}
       allGuests={props.allGuests}
       nodes={props.state.nodes || []}
+      hosts={props.hosts}
       storage={props.state.storage || []}
       dockerHosts={props.state.dockerHosts || []}
       pbsInstances={props.state.pbs || []}
@@ -2317,7 +2373,9 @@ function ThresholdsTab(props: ThresholdsTabProps) {
       guestPoweredOffSeverity={props.guestPoweredOffSeverity}
       setGuestPoweredOffSeverity={props.setGuestPoweredOffSeverity}
       nodeDefaults={props.nodeDefaults()}
+      hostDefaults={props.hostDefaults()}
       setNodeDefaults={props.setNodeDefaults}
+      setHostDefaults={props.setHostDefaults}
       dockerDefaults={props.dockerDefaults()}
       setDockerDefaults={props.setDockerDefaults}
       dockerIgnoredPrefixes={props.dockerIgnoredPrefixes}
@@ -2342,6 +2400,8 @@ function ThresholdsTab(props: ThresholdsTabProps) {
       setDisableAllNodes={props.setDisableAllNodes}
       disableAllGuests={props.disableAllGuests}
       setDisableAllGuests={props.setDisableAllGuests}
+      disableAllHosts={props.disableAllHosts}
+      setDisableAllHosts={props.setDisableAllHosts}
       disableAllStorage={props.disableAllStorage}
       setDisableAllStorage={props.setDisableAllStorage}
       disableAllPBS={props.disableAllPBS}
@@ -2356,6 +2416,8 @@ function ThresholdsTab(props: ThresholdsTabProps) {
       setDisableAllNodesOffline={props.setDisableAllNodesOffline}
       disableAllGuestsOffline={props.disableAllGuestsOffline}
       setDisableAllGuestsOffline={props.setDisableAllGuestsOffline}
+      disableAllHostsOffline={props.disableAllHostsOffline}
+      setDisableAllHostsOffline={props.setDisableAllHostsOffline}
       disableAllPBSOffline={props.disableAllPBSOffline}
       setDisableAllPBSOffline={props.setDisableAllPBSOffline}
       disableAllPMGOffline={props.disableAllPMGOffline}
@@ -2364,11 +2426,13 @@ function ThresholdsTab(props: ThresholdsTabProps) {
       setDisableAllDockerHostsOffline={props.setDisableAllDockerHostsOffline}
       resetGuestDefaults={props.resetGuestDefaults}
       resetNodeDefaults={props.resetNodeDefaults}
+      resetHostDefaults={props.resetHostDefaults}
       resetDockerDefaults={props.resetDockerDefaults}
       resetDockerIgnoredPrefixes={props.resetDockerIgnoredPrefixes}
       resetStorageDefault={props.resetStorageDefault}
       factoryGuestDefaults={props.factoryGuestDefaults}
       factoryNodeDefaults={props.factoryNodeDefaults}
+      factoryHostDefaults={props.factoryHostDefaults}
       factoryDockerDefaults={props.factoryDockerDefaults}
       factoryStorageDefault={props.factoryStorageDefault}
     />

frontend-modern/src/types/alerts.ts

@@ -108,6 +108,7 @@ export interface AlertConfig {
   activationTime?: string;
   guestDefaults: AlertThresholds;
   nodeDefaults: AlertThresholds;
+  hostDefaults?: AlertThresholds;
   storageDefault: HysteresisThreshold;
   dockerDefaults?: DockerThresholdConfig;
   dockerIgnoredContainerPrefixes?: string[];
@@ -194,12 +195,14 @@ export interface AlertConfig {
   disableAllStorage?: boolean;
   disableAllPBS?: boolean;
   disableAllPMG?: boolean;
+  disableAllHosts?: boolean;
   disableAllDockerHosts?: boolean;
   disableAllDockerContainers?: boolean;
   disableAllNodesOffline?: boolean;
   disableAllGuestsOffline?: boolean;
   disableAllPBSOffline?: boolean;
   disableAllPMGOffline?: boolean;
+  disableAllHostsOffline?: boolean;
   disableAllDockerHostsOffline?: boolean;
 }
 

internal/alerts/alerts.go

@@ -325,6 +325,7 @@ type AlertConfig struct {
 	ActivationTime                 *time.Time                 `json:"activationTime,omitempty"`
 	GuestDefaults                  ThresholdConfig            `json:"guestDefaults"`
 	NodeDefaults                   ThresholdConfig            `json:"nodeDefaults"`
+	HostDefaults                   ThresholdConfig            `json:"hostDefaults"`
 	StorageDefault                 HysteresisThreshold        `json:"storageDefault"`
 	DockerDefaults                 DockerThresholdConfig      `json:"dockerDefaults"`
 	DockerIgnoredContainerPrefixes []string                   `json:"dockerIgnoredContainerPrefixes,omitempty"`
@@ -337,6 +338,7 @@ type AlertConfig struct {
 	// Global disable flags per resource type
 	DisableAllNodes              bool `json:"disableAllNodes"`              // Disable all alerts for Proxmox nodes
 	DisableAllGuests             bool `json:"disableAllGuests"`             // Disable all alerts for VMs/containers
+	DisableAllHosts              bool `json:"disableAllHosts"`              // Disable all alerts for Pulse host agents
 	DisableAllStorage            bool `json:"disableAllStorage"`            // Disable all alerts for storage
 	DisableAllPBS                bool `json:"disableAllPBS"`                // Disable all alerts for PBS servers
 	DisableAllPMG                bool `json:"disableAllPMG"`                // Disable all alerts for PMG instances
@@ -344,6 +346,7 @@ type AlertConfig struct {
 	DisableAllDockerContainers   bool `json:"disableAllDockerContainers"`   // Disable all alerts for Docker containers
 	DisableAllNodesOffline       bool `json:"disableAllNodesOffline"`       // Disable node offline/connectivity alerts globally
 	DisableAllGuestsOffline      bool `json:"disableAllGuestsOffline"`      // Disable guest powered-off alerts globally
+	DisableAllHostsOffline       bool `json:"disableAllHostsOffline"`       // Disable host agent offline alerts globally
 	DisableAllPBSOffline         bool `json:"disableAllPBSOffline"`         // Disable PBS offline alerts globally
 	DisableAllPMGOffline         bool `json:"disableAllPMGOffline"`         // Disable PMG offline alerts globally
 	DisableAllDockerHostsOffline bool `json:"disableAllDockerHostsOffline"` // Disable Docker host offline alerts globally
@@ -488,6 +491,11 @@ func NewManager() *Manager {
 				Disk:        &HysteresisThreshold{Trigger: 90, Clear: 85},
 				Temperature: &HysteresisThreshold{Trigger: 80, Clear: 75}, // Warning at 80°C, clear at 75°C
 			},
+			HostDefaults: ThresholdConfig{
+				CPU:    &HysteresisThreshold{Trigger: 80, Clear: 75},
+				Memory: &HysteresisThreshold{Trigger: 85, Clear: 80},
+				Disk:   &HysteresisThreshold{Trigger: 90, Clear: 85},
+			},
 			DockerDefaults: DockerThresholdConfig{
 				CPU:               HysteresisThreshold{Trigger: 80, Clear: 75},
 				Memory:            HysteresisThreshold{Trigger: 85, Clear: 80},
@@ -886,6 +894,32 @@ func (m *Manager) UpdateConfig(config AlertConfig) {
 		}
 	}
 
+	// Ensure host agent defaults exist
+	if config.HostDefaults.CPU == nil || config.HostDefaults.CPU.Trigger <= 0 {
+		config.HostDefaults.CPU = &HysteresisThreshold{Trigger: 80, Clear: 75}
+	} else if config.HostDefaults.CPU.Clear <= 0 {
+		config.HostDefaults.CPU.Clear = config.HostDefaults.CPU.Trigger - 5
+		if config.HostDefaults.CPU.Clear <= 0 {
+			config.HostDefaults.CPU.Clear = 75
+		}
+	}
+	if config.HostDefaults.Memory == nil || config.HostDefaults.Memory.Trigger <= 0 {
+		config.HostDefaults.Memory = &HysteresisThreshold{Trigger: 85, Clear: 80}
+	} else if config.HostDefaults.Memory.Clear <= 0 {
+		config.HostDefaults.Memory.Clear = config.HostDefaults.Memory.Trigger - 5
+		if config.HostDefaults.Memory.Clear <= 0 {
+			config.HostDefaults.Memory.Clear = 80
+		}
+	}
+	if config.HostDefaults.Disk == nil || config.HostDefaults.Disk.Trigger <= 0 {
+		config.HostDefaults.Disk = &HysteresisThreshold{Trigger: 90, Clear: 85}
+	} else if config.HostDefaults.Disk.Clear <= 0 {
+		config.HostDefaults.Disk.Clear = config.HostDefaults.Disk.Trigger - 5
+		if config.HostDefaults.Disk.Clear <= 0 {
+			config.HostDefaults.Disk.Clear = 85
+		}
+	}
+
 	// Normalize any metric-level delay overrides
 	config.MetricTimeThresholds = normalizeMetricTimeThresholds(config.MetricTimeThresholds)
 
@@ -1879,6 +1913,373 @@ func (m *Manager) CheckNode(node models.Node) {
 	}
 }
 
+func hostResourceID(hostID string) string {
+	trimmed := strings.TrimSpace(hostID)
+	if trimmed == "" {
+		return "host:unknown"
+	}
+	return fmt.Sprintf("host:%s", trimmed)
+}
+
+func hostDisplayName(host models.Host) string {
+	if name := strings.TrimSpace(host.DisplayName); name != "" {
+		return name
+	}
+	if name := strings.TrimSpace(host.Hostname); name != "" {
+		return name
+	}
+	if host.ID != "" {
+		return host.ID
+	}
+	return "Host"
+}
+
+func hostInstanceName(host models.Host) string {
+	if platform := strings.TrimSpace(host.Platform); platform != "" {
+		return platform
+	}
+	if osName := strings.TrimSpace(host.OSName); osName != "" {
+		return osName
+	}
+	return "Host Agent"
+}
+
+func sanitizeHostComponent(value string) string {
+	value = strings.TrimSpace(strings.ToLower(value))
+	if value == "" {
+		return "unknown"
+	}
+
+	var builder strings.Builder
+	lastHyphen := false
+	for _, r := range value {
+		switch {
+		case r >= 'a' && r <= 'z':
+			builder.WriteRune(r)
+			lastHyphen = false
+		case r >= '0' && r <= '9':
+			builder.WriteRune(r)
+			lastHyphen = false
+		default:
+			if !lastHyphen {
+				builder.WriteRune('-')
+				lastHyphen = true
+			}
+		}
+	}
+
+	sanitized := strings.Trim(builder.String(), "-")
+	if sanitized == "" {
+		return "unknown"
+	}
+	return sanitized
+}
+
+func hostDiskResourceID(host models.Host, disk models.Disk) (string, string) {
+	label := strings.TrimSpace(disk.Mountpoint)
+	if label == "" {
+		label = strings.TrimSpace(disk.Device)
+	}
+	if label == "" {
+		label = "disk"
+	}
+	resourceID := fmt.Sprintf("%s/disk:%s", hostResourceID(host.ID), sanitizeHostComponent(label))
+	resourceName := fmt.Sprintf("%s (%s)", hostDisplayName(host), label)
+	return resourceID, resourceName
+}
+
+// CheckHost evaluates host agent telemetry for alerts.
+func (m *Manager) CheckHost(host models.Host) {
+	if host.ID == "" {
+		return
+	}
+
+	// Fresh telemetry marks the host as online and clears offline tracking.
+	m.HandleHostOnline(host)
+
+	m.mu.RLock()
+	alertsEnabled := m.config.Enabled
+	disableAllHosts := m.config.DisableAllHosts
+	thresholds := m.config.HostDefaults
+	override, hasOverride := m.config.Overrides[host.ID]
+	m.mu.RUnlock()
+
+	if !alertsEnabled || disableAllHosts {
+		return
+	}
+
+	if hasOverride {
+		thresholds = m.applyThresholdOverride(thresholds, override)
+		if thresholds.Disabled {
+			m.clearHostMetricAlerts(host.ID)
+			m.clearHostDiskAlerts(host.ID)
+			return
+		}
+	}
+
+	resourceID := hostResourceID(host.ID)
+	resourceName := hostDisplayName(host)
+	nodeName := strings.TrimSpace(host.Hostname)
+	instanceName := hostInstanceName(host)
+
+	baseMetadata := map[string]interface{}{
+		"resourceType": "Host",
+		"hostId":       host.ID,
+		"hostname":     host.Hostname,
+		"displayName":  host.DisplayName,
+		"platform":     host.Platform,
+		"osName":       host.OSName,
+		"osVersion":    host.OSVersion,
+		"agentVersion": host.AgentVersion,
+		"architecture": host.Architecture,
+	}
+	if len(host.Tags) > 0 {
+		baseMetadata["tags"] = append([]string(nil), host.Tags...)
+	}
+
+	if thresholds.CPU != nil {
+		cpuMetadata := cloneMetadata(baseMetadata)
+		cpuMetadata["metric"] = "cpu"
+		cpuMetadata["cpuUsagePercent"] = host.CPUUsage
+		if host.CPUCount > 0 {
+			cpuMetadata["cpuCount"] = host.CPUCount
+		}
+		m.checkMetric(resourceID, resourceName, nodeName, instanceName, "Host", "cpu", host.CPUUsage, thresholds.CPU, &metricOptions{Metadata: cpuMetadata})
+	} else {
+		m.clearHostMetricAlerts(host.ID, "cpu")
+	}
+
+	if thresholds.Memory != nil {
+		memMetadata := cloneMetadata(baseMetadata)
+		memMetadata["metric"] = "memory"
+		memMetadata["memoryUsagePercent"] = host.Memory.Usage
+		if host.Memory.Total > 0 {
+			memMetadata["memoryTotalBytes"] = host.Memory.Total
+			memMetadata["memoryUsedBytes"] = host.Memory.Used
+			memMetadata["memoryFreeBytes"] = host.Memory.Free
+		}
+		m.checkMetric(resourceID, resourceName, nodeName, instanceName, "Host", "memory", host.Memory.Usage, thresholds.Memory, &metricOptions{Metadata: memMetadata})
+	} else {
+		m.clearHostMetricAlerts(host.ID, "memory")
+	}
+
+	seenDisks := make(map[string]struct{}, len(host.Disks))
+	if thresholds.Disk != nil && thresholds.Disk.Trigger > 0 {
+		for _, disk := range host.Disks {
+			diskResourceID, diskName := hostDiskResourceID(host, disk)
+			seenDisks[diskResourceID] = struct{}{}
+
+			diskMetadata := cloneMetadata(baseMetadata)
+			diskMetadata["metric"] = "disk"
+			diskMetadata["mountpoint"] = disk.Mountpoint
+			diskMetadata["device"] = disk.Device
+			diskMetadata["diskType"] = disk.Type
+			diskMetadata["diskUsagePercent"] = disk.Usage
+			if disk.Total > 0 {
+				diskMetadata["diskTotalBytes"] = disk.Total
+				diskMetadata["diskUsedBytes"] = disk.Used
+				diskMetadata["diskFreeBytes"] = disk.Free
+			}
+
+			m.checkMetric(diskResourceID, diskName, nodeName, instanceName, "Host Disk", "disk", disk.Usage, thresholds.Disk, &metricOptions{Metadata: diskMetadata})
+		}
+	} else {
+		m.clearHostDiskAlerts(host.ID)
+	}
+
+	m.cleanupHostDiskAlerts(host, seenDisks)
+}
+
+// HandleHostOnline clears offline tracking and alerts for a host agent.
+func (m *Manager) HandleHostOnline(host models.Host) {
+	if host.ID == "" {
+		return
+	}
+
+	alertID := fmt.Sprintf("host-offline-%s", host.ID)
+	resourceKey := hostResourceID(host.ID)
+
+	m.mu.Lock()
+	delete(m.offlineConfirmations, resourceKey)
+	_, exists := m.activeAlerts[alertID]
+	m.mu.Unlock()
+
+	if exists {
+		m.clearAlert(alertID)
+	}
+}
+
+// HandleHostRemoved clears alerts and tracking when a host agent is deleted.
+func (m *Manager) HandleHostRemoved(host models.Host) {
+	if host.ID == "" {
+		return
+	}
+
+	m.HandleHostOnline(host)
+	m.clearHostMetricAlerts(host.ID)
+	m.clearHostDiskAlerts(host.ID)
+}
+
+// HandleHostOffline raises an alert when a host agent stops reporting.
+func (m *Manager) HandleHostOffline(host models.Host) {
+	if host.ID == "" {
+		return
+	}
+
+	m.mu.RLock()
+	if !m.config.Enabled {
+		m.mu.RUnlock()
+		return
+	}
+	disableHostsOffline := m.config.DisableAllHostsOffline
+	m.mu.RUnlock()
+
+	alertID := fmt.Sprintf("host-offline-%s", host.ID)
+	resourceKey := hostResourceID(host.ID)
+	resourceName := hostDisplayName(host)
+	nodeName := strings.TrimSpace(host.Hostname)
+	instanceName := hostInstanceName(host)
+
+	if disableHostsOffline {
+		m.mu.Lock()
+		delete(m.offlineConfirmations, resourceKey)
+		m.mu.Unlock()
+		m.clearAlert(alertID)
+		return
+	}
+
+	var disableConnectivity bool
+	m.mu.RLock()
+	if override, exists := m.config.Overrides[host.ID]; exists {
+		disableConnectivity = override.DisableConnectivity || override.Disabled
+	}
+	m.mu.RUnlock()
+
+	if disableConnectivity {
+		m.clearAlert(alertID)
+		m.mu.Lock()
+		delete(m.offlineConfirmations, resourceKey)
+		m.mu.Unlock()
+		return
+	}
+
+	m.mu.Lock()
+	if alert, exists := m.activeAlerts[alertID]; exists && alert != nil {
+		alert.LastSeen = time.Now()
+		m.activeAlerts[alertID] = alert
+		m.mu.Unlock()
+		return
+	}
+
+	m.offlineConfirmations[resourceKey]++
+	const requiredConfirmations = 3
+	if confirmations := m.offlineConfirmations[resourceKey]; confirmations < requiredConfirmations {
+		m.mu.Unlock()
+		log.Debug().
+			Str("host", resourceName).
+			Str("hostID", host.ID).
+			Int("confirmations", confirmations).
+			Int("required", requiredConfirmations).
+			Msg("Host agent appears offline, awaiting confirmation")
+		return
+	}
+
+	alert := &Alert{
+		ID:           alertID,
+		Type:         "host-offline",
+		Level:        AlertLevelCritical,
+		ResourceID:   resourceKey,
+		ResourceName: resourceName,
+		Node:         nodeName,
+		Instance:     instanceName,
+		Message:      fmt.Sprintf("Host '%s' is offline", resourceName),
+		Value:        0,
+		Threshold:    0,
+		StartTime:    time.Now(),
+		LastSeen:     time.Now(),
+		Metadata: map[string]interface{}{
+			"resourceType": "Host",
+			"hostId":       host.ID,
+			"hostname":     host.Hostname,
+			"displayName":  host.DisplayName,
+			"platform":     host.Platform,
+			"osName":       host.OSName,
+			"osVersion":    host.OSVersion,
+		},
+	}
+
+	m.preserveAlertState(alertID, alert)
+	m.activeAlerts[alertID] = alert
+	m.recentAlerts[alertID] = alert
+	m.historyManager.AddAlert(*alert)
+	m.dispatchAlert(alert, false)
+	m.mu.Unlock()
+
+	log.Error().
+		Str("host", resourceName).
+		Str("hostID", host.ID).
+		Str("hostname", host.Hostname).
+		Msg("CRITICAL: Host agent is offline")
+}
+
+func (m *Manager) clearHostMetricAlerts(hostID string, metrics ...string) {
+	if hostID == "" {
+		return
+	}
+	resourceID := hostResourceID(hostID)
+	if len(metrics) == 0 {
+		metrics = []string{"cpu", "memory"}
+	}
+	for _, metric := range metrics {
+		m.clearAlert(fmt.Sprintf("%s-%s", resourceID, metric))
+	}
+}
+
+func (m *Manager) clearHostDiskAlerts(hostID string) {
+	if hostID == "" {
+		return
+	}
+
+	prefix := fmt.Sprintf("%s/disk:", hostResourceID(hostID))
+
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	for alertID, alert := range m.activeAlerts {
+		if alert == nil {
+			continue
+		}
+		if !strings.HasPrefix(alert.ResourceID, prefix) {
+			continue
+		}
+		m.clearAlertNoLock(alertID)
+	}
+}
+
+func (m *Manager) cleanupHostDiskAlerts(host models.Host, seen map[string]struct{}) {
+	if host.ID == "" {
+		return
+	}
+
+	prefix := fmt.Sprintf("%s/disk:", hostResourceID(host.ID))
+
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	for alertID, alert := range m.activeAlerts {
+		if alert == nil {
+			continue
+		}
+		if !strings.HasPrefix(alert.ResourceID, prefix) {
+			continue
+		}
+		if _, exists := seen[alert.ResourceID]; exists {
+			continue
+		}
+		m.clearAlertNoLock(alertID)
+	}
+}
+
 // CheckPBS checks PBS instance metrics against thresholds
 func (m *Manager) CheckPBS(pbs models.PBSInstance) {
 	m.mu.RLock()
@@ -6728,7 +7129,7 @@ func (m *Manager) SaveActiveAlerts() error {
 		alerts = append(alerts, alert)
 	}
 
-	data, err := json.MarshalIndent(alerts, "", "  ")
+	data, err := json.Marshal(alerts)
 	if err != nil {
 		return fmt.Errorf("failed to marshal active alerts: %w", err)
 	}

internal/alerts/alerts_test.go

@@ -213,6 +213,167 @@ func TestHandleDockerHostRemovedClearsAlertsAndTracking(t *testing.T) {
 	}
 }
 
+func TestCheckHostGeneratesMetricAlerts(t *testing.T) {
+	m := NewManager()
+	m.ClearActiveAlerts()
+	m.mu.Lock()
+	m.config.TimeThreshold = 0
+	m.config.TimeThresholds = map[string]int{}
+	m.mu.Unlock()
+
+	host := models.Host{
+		ID:          "host-1",
+		DisplayName: "Test Host",
+		Hostname:    "host-1.example",
+		Platform:    "linux",
+		OSName:      "ubuntu",
+		CPUUsage:    95,
+		CPUCount:    8,
+		Memory: models.Memory{
+			Usage: 92,
+			Total: 16384,
+			Used:  15000,
+			Free:  1384,
+		},
+		Disks: []models.Disk{
+			{
+				Mountpoint: "/",
+				Usage:      93,
+				Total:      100,
+				Used:       93,
+				Free:       7,
+			},
+		},
+		Status:          "online",
+		IntervalSeconds: 30,
+		LastSeen:        time.Now(),
+		Tags:            []string{"prod"},
+	}
+
+	m.CheckHost(host)
+
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	cpuAlertID := fmt.Sprintf("%s-cpu", hostResourceID(host.ID))
+	if _, exists := m.activeAlerts[cpuAlertID]; !exists {
+		t.Fatalf("expected CPU alert %q to be active", cpuAlertID)
+	}
+
+	memAlertID := fmt.Sprintf("%s-memory", hostResourceID(host.ID))
+	if _, exists := m.activeAlerts[memAlertID]; !exists {
+		t.Fatalf("expected memory alert %q to be active", memAlertID)
+	}
+
+	diskResourceID, _ := hostDiskResourceID(host, host.Disks[0])
+	diskAlertID := fmt.Sprintf("%s-disk", diskResourceID)
+	if _, exists := m.activeAlerts[diskAlertID]; !exists {
+		t.Fatalf("expected disk alert %q to be active", diskAlertID)
+	}
+}
+
+func TestHandleHostOfflineRequiresConfirmations(t *testing.T) {
+	m := NewManager()
+	m.ClearActiveAlerts()
+	host := models.Host{ID: "host-2", DisplayName: "Second Host", Hostname: "host-two"}
+	alertID := fmt.Sprintf("host-offline-%s", host.ID)
+	resourceKey := hostResourceID(host.ID)
+
+	m.HandleHostOffline(host)
+	m.mu.RLock()
+	if _, exists := m.activeAlerts[alertID]; exists {
+		t.Fatalf("expected no alert after first offline detection")
+	}
+	if count := m.offlineConfirmations[resourceKey]; count != 1 {
+		t.Fatalf("expected confirmation count to be 1, got %d", count)
+	}
+	m.mu.RUnlock()
+
+	m.HandleHostOffline(host)
+	m.mu.RLock()
+	if _, exists := m.activeAlerts[alertID]; exists {
+		t.Fatalf("expected no alert after second offline detection")
+	}
+	if count := m.offlineConfirmations[resourceKey]; count != 2 {
+		t.Fatalf("expected confirmation count to be 2, got %d", count)
+	}
+	m.mu.RUnlock()
+
+	m.HandleHostOffline(host)
+	m.mu.RLock()
+	if _, exists := m.activeAlerts[alertID]; !exists {
+		t.Fatalf("expected alert %q after third offline detection", alertID)
+	}
+	m.mu.RUnlock()
+
+	m.HandleHostOnline(host)
+	m.mu.RLock()
+	if _, exists := m.activeAlerts[alertID]; exists {
+		t.Fatalf("expected offline alert %q to be cleared after host online", alertID)
+	}
+	if _, exists := m.offlineConfirmations[resourceKey]; exists {
+		t.Fatalf("expected offline confirmations to be cleared when host online")
+	}
+	m.mu.RUnlock()
+}
+
+func TestCheckHostDisabledOverrideClearsAlerts(t *testing.T) {
+	m := NewManager()
+	m.ClearActiveAlerts()
+	m.mu.Lock()
+	m.config.TimeThreshold = 0
+	m.config.TimeThresholds = map[string]int{}
+	m.mu.Unlock()
+
+	host := models.Host{
+		ID:          "host-3",
+		DisplayName: "Override Host",
+		Hostname:    "override.example",
+		CPUUsage:    90,
+		Memory: models.Memory{
+			Usage: 91,
+			Total: 16000,
+			Used:  14560,
+			Free:  1440,
+		},
+		Disks: []models.Disk{
+			{Mountpoint: "/data", Usage: 92, Total: 200, Used: 184, Free: 16},
+		},
+		Status:          "online",
+		IntervalSeconds: 30,
+		LastSeen:        time.Now(),
+	}
+
+	m.CheckHost(host)
+
+	m.mu.RLock()
+	if len(m.activeAlerts) == 0 {
+		m.mu.RUnlock()
+		t.Fatalf("expected active alerts prior to disabling host overrides")
+	}
+	m.mu.RUnlock()
+
+	cfg := m.GetConfig()
+	cfg.Overrides = map[string]ThresholdConfig{
+		host.ID: {
+			Disabled: true,
+		},
+	}
+	m.UpdateConfig(cfg)
+	m.mu.Lock()
+	m.config.TimeThreshold = 0
+	m.config.TimeThresholds = map[string]int{}
+	m.mu.Unlock()
+
+	m.CheckHost(host)
+
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	if len(m.activeAlerts) != 0 {
+		t.Fatalf("expected all host alerts to be cleared after disabling override, got %d", len(m.activeAlerts))
+	}
+}
+
 func TestCheckSnapshotsForInstanceCreatesAndClearsAlerts(t *testing.T) {
 	m := NewManager()
 	m.ClearActiveAlerts()

internal/alerts/history.go

@@ -174,7 +174,7 @@ func (hm *HistoryManager) saveHistory() error {
 	copy(snapshot, hm.history)
 	hm.mu.RUnlock()
 
-	data, err := json.MarshalIndent(snapshot, "", "  ")
+	data, err := json.Marshal(snapshot)
 
 	if err != nil {
 		return fmt.Errorf("failed to marshal history: %w", err)

internal/api/csrf_store.go

@@ -207,7 +207,7 @@ func (c *CSRFTokenStore) saveUnsafe() {
 	}
 
 	// Marshal tokens
-	jsonData, err := json.MarshalIndent(data, "", "  ")
+	jsonData, err := json.Marshal(data)
 	if err != nil {
 		log.Error().Err(err).Msg("Failed to marshal CSRF tokens")
 		return

internal/api/host_agents_test.go

@@ -0,0 +1,136 @@
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"reflect"
+	"testing"
+	"time"
+	"unsafe"
+
+	"github.com/rcourtman/pulse-go-rewrite/internal/config"
+	"github.com/rcourtman/pulse-go-rewrite/internal/models"
+	"github.com/rcourtman/pulse-go-rewrite/internal/monitoring"
+)
+
+func TestHandleLookupByIDSuccess(t *testing.T) {
+	t.Parallel()
+
+	hostID := "host-123"
+	tokenID := "token-abc"
+	lastSeen := time.Now().UTC()
+
+	handler := newHostAgentHandlerForTests(t, models.Host{
+		ID:         hostID,
+		Hostname:   "host.local",
+		DisplayName:"Host Local",
+		Status:     "online",
+		TokenID:    tokenID,
+		LastSeen:   lastSeen,
+	})
+
+	req := httptest.NewRequest(http.MethodGet, "/api/agents/host/lookup?id="+hostID, nil)
+	attachAPITokenRecord(req, &config.APITokenRecord{ID: tokenID})
+
+	rec := httptest.NewRecorder()
+	handler.HandleLookup(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected status %d, got %d", http.StatusOK, rec.Code)
+	}
+
+	var resp struct {
+		Success bool `json:"success"`
+		Host struct {
+			ID        string    `json:"id"`
+			Hostname  string    `json:"hostname"`
+			Status    string    `json:"status"`
+			Connected bool      `json:"connected"`
+			LastSeen  time.Time `json:"lastSeen"`
+		} `json:"host"`
+	}
+	if err := json.NewDecoder(rec.Body).Decode(&resp); err != nil {
+		t.Fatalf("failed to decode response: %v", err)
+	}
+
+	if !resp.Success {
+		t.Fatalf("expected success=true")
+	}
+	if resp.Host.ID != hostID {
+		t.Fatalf("unexpected host id %q", resp.Host.ID)
+	}
+	if !resp.Host.Connected {
+		t.Fatalf("expected connected host")
+	}
+	if !resp.Host.LastSeen.Equal(lastSeen) {
+		t.Fatalf("expected lastSeen %v, got %v", lastSeen, resp.Host.LastSeen)
+	}
+}
+
+func TestHandleLookupForbiddenOnTokenMismatch(t *testing.T) {
+	t.Parallel()
+
+	hostID := "host-456"
+
+	handler := newHostAgentHandlerForTests(t, models.Host{
+		ID:       hostID,
+		Hostname: "mismatch.local",
+		Status:   "online",
+		TokenID:  "token-correct",
+	})
+
+	req := httptest.NewRequest(http.MethodGet, "/api/agents/host/lookup?id="+hostID, nil)
+	attachAPITokenRecord(req, &config.APITokenRecord{ID: "token-wrong"})
+
+	rec := httptest.NewRecorder()
+	handler.HandleLookup(rec, req)
+
+	if rec.Code != http.StatusForbidden {
+		t.Fatalf("expected status %d, got %d", http.StatusForbidden, rec.Code)
+	}
+}
+
+func TestHandleLookupNotFound(t *testing.T) {
+	t.Parallel()
+
+	handler := newHostAgentHandlerForTests(t)
+
+	req := httptest.NewRequest(http.MethodGet, "/api/agents/host/lookup?id=missing", nil)
+	rec := httptest.NewRecorder()
+
+	handler.HandleLookup(rec, req)
+
+	if rec.Code != http.StatusNotFound {
+		t.Fatalf("expected status %d, got %d", http.StatusNotFound, rec.Code)
+	}
+}
+
+func newHostAgentHandlerForTests(t *testing.T, hosts ...models.Host) *HostAgentHandlers {
+	t.Helper()
+
+	monitor := &monitoring.Monitor{}
+	state := models.NewState()
+	for _, host := range hosts {
+		state.UpsertHost(host)
+	}
+
+	setUnexportedField(t, monitor, "state", state)
+
+	return &HostAgentHandlers{
+		monitor: monitor,
+	}
+}
+
+func setUnexportedField(t *testing.T, target interface{}, field string, value interface{}) {
+	t.Helper()
+
+	v := reflect.ValueOf(target).Elem()
+	f := v.FieldByName(field)
+	if !f.IsValid() {
+		t.Fatalf("field %q not found", field)
+	}
+
+	ptr := unsafe.Pointer(f.UnsafeAddr())
+	reflect.NewAt(f.Type(), ptr).Elem().Set(reflect.ValueOf(value))
+}

internal/api/recovery_tokens.go

@@ -218,7 +218,7 @@ func (r *RecoveryTokenStore) saveUnsafe() {
 	}
 
 	// Marshal tokens
-	data, err := json.MarshalIndent(r.tokens, "", "  ")
+	data, err := json.Marshal(r.tokens)
 	if err != nil {
 		log.Error().Err(err).Msg("Failed to marshal recovery tokens")
 		return

internal/api/session_store.go

@@ -162,7 +162,7 @@ func (s *SessionStore) saveUnsafe() {
 	}
 
 	// Marshal sessions
-	data, err := json.MarshalIndent(s.sessions, "", "  ")
+	data, err := json.Marshal(s.sessions)
 	if err != nil {
 		log.Error().Err(err).Msg("Failed to marshal sessions")
 		return

internal/config/config.go

@@ -28,6 +28,13 @@ import (
 	"github.com/rs/zerolog/log"
 )
 
+const (
+	DefaultGuestMetadataMinRefresh    = 2 * time.Minute
+	DefaultGuestMetadataRefreshJitter = 45 * time.Second
+	DefaultGuestMetadataRetryBackoff  = 30 * time.Second
+	DefaultGuestMetadataMaxConcurrent = 4
+)
+
 // IsPasswordHashed checks if a string looks like a bcrypt hash
 func IsPasswordHashed(password string) bool {
 	// Bcrypt hashes start with $2a$, $2b$, or $2y$ and are 60 characters long
@@ -76,19 +83,23 @@ type Config struct {
 
 	// Monitoring settings
 	// Note: PVE polling is hardcoded to 10s since Proxmox cluster/resources endpoint only updates every 10s
-	PBSPollingInterval          time.Duration `envconfig:"PBS_POLLING_INTERVAL"` // PBS polling interval (60s default)
+	PBSPollingInterval              time.Duration `envconfig:"PBS_POLLING_INTERVAL"` // PBS polling interval (60s default)
-	PMGPollingInterval          time.Duration `envconfig:"PMG_POLLING_INTERVAL"` // PMG polling interval (60s default)
+	PMGPollingInterval              time.Duration `envconfig:"PMG_POLLING_INTERVAL"` // PMG polling interval (60s default)
-	ConcurrentPolling           bool          `envconfig:"CONCURRENT_POLLING" default:"true"`
+	ConcurrentPolling               bool          `envconfig:"CONCURRENT_POLLING" default:"true"`
-	ConnectionTimeout           time.Duration `envconfig:"CONNECTION_TIMEOUT" default:"45s"` // Increased for slow storage operations
+	ConnectionTimeout               time.Duration `envconfig:"CONNECTION_TIMEOUT" default:"45s"` // Increased for slow storage operations
-	MetricsRetentionDays        int           `envconfig:"METRICS_RETENTION_DAYS" default:"7"`
+	MetricsRetentionDays            int           `envconfig:"METRICS_RETENTION_DAYS" default:"7"`
-	BackupPollingCycles         int           `envconfig:"BACKUP_POLLING_CYCLES" default:"10"`
+	BackupPollingCycles             int           `envconfig:"BACKUP_POLLING_CYCLES" default:"10"`
-	BackupPollingInterval       time.Duration `envconfig:"BACKUP_POLLING_INTERVAL"`
+	BackupPollingInterval           time.Duration `envconfig:"BACKUP_POLLING_INTERVAL"`
-	EnableBackupPolling         bool          `envconfig:"ENABLE_BACKUP_POLLING" default:"true"`
+	EnableBackupPolling             bool          `envconfig:"ENABLE_BACKUP_POLLING" default:"true"`
-	WebhookBatchDelay           time.Duration `envconfig:"WEBHOOK_BATCH_DELAY" default:"10s"`
+	WebhookBatchDelay               time.Duration `envconfig:"WEBHOOK_BATCH_DELAY" default:"10s"`
-	AdaptivePollingEnabled      bool          `envconfig:"ADAPTIVE_POLLING_ENABLED" default:"false"`
+	AdaptivePollingEnabled          bool          `envconfig:"ADAPTIVE_POLLING_ENABLED" default:"false"`
-	AdaptivePollingBaseInterval time.Duration `envconfig:"ADAPTIVE_POLLING_BASE_INTERVAL" default:"10s"`
+	AdaptivePollingBaseInterval     time.Duration `envconfig:"ADAPTIVE_POLLING_BASE_INTERVAL" default:"10s"`
-	AdaptivePollingMinInterval  time.Duration `envconfig:"ADAPTIVE_POLLING_MIN_INTERVAL" default:"5s"`
+	AdaptivePollingMinInterval      time.Duration `envconfig:"ADAPTIVE_POLLING_MIN_INTERVAL" default:"5s"`
-	AdaptivePollingMaxInterval  time.Duration `envconfig:"ADAPTIVE_POLLING_MAX_INTERVAL" default:"5m"`
+	AdaptivePollingMaxInterval      time.Duration `envconfig:"ADAPTIVE_POLLING_MAX_INTERVAL" default:"5m"`
+	GuestMetadataMinRefreshInterval time.Duration `envconfig:"GUEST_METADATA_MIN_REFRESH_INTERVAL" default:"2m" json:"guestMetadataMinRefreshInterval"`
+	GuestMetadataRefreshJitter      time.Duration `envconfig:"GUEST_METADATA_REFRESH_JITTER" default:"45s" json:"guestMetadataRefreshJitter"`
+	GuestMetadataRetryBackoff       time.Duration `envconfig:"GUEST_METADATA_RETRY_BACKOFF" default:"30s" json:"guestMetadataRetryBackoff"`
+	GuestMetadataMaxConcurrent      int           `envconfig:"GUEST_METADATA_MAX_CONCURRENT" default:"4" json:"guestMetadataMaxConcurrent"`
 
 	// Logging settings
 	LogLevel    string `envconfig:"LOG_LEVEL" default:"info"`
@@ -485,36 +496,40 @@ func Load() (*Config, error) {
 
 	// Initialize config with defaults
 	cfg := &Config{
-		BackendHost:                 "0.0.0.0",
+		BackendHost:                     "0.0.0.0",
-		BackendPort:                 3000,
+		BackendPort:                     3000,
-		FrontendHost:                "0.0.0.0",
+		FrontendHost:                    "0.0.0.0",
-		FrontendPort:                7655,
+		FrontendPort:                    7655,
-		ConfigPath:                  dataDir,
+		ConfigPath:                      dataDir,
-		DataPath:                    dataDir,
+		DataPath:                        dataDir,
-		ConcurrentPolling:           true,
+		ConcurrentPolling:               true,
-		ConnectionTimeout:           60 * time.Second,
+		ConnectionTimeout:               60 * time.Second,
-		MetricsRetentionDays:        7,
+		MetricsRetentionDays:            7,
-		BackupPollingCycles:         10,
+		BackupPollingCycles:             10,
-		BackupPollingInterval:       0,
+		BackupPollingInterval:           0,
-		EnableBackupPolling:         true,
+		EnableBackupPolling:             true,
-		WebhookBatchDelay:           10 * time.Second,
+		WebhookBatchDelay:               10 * time.Second,
-		AdaptivePollingEnabled:      false,
+		AdaptivePollingEnabled:          false,
-		AdaptivePollingBaseInterval: 10 * time.Second,
+		AdaptivePollingBaseInterval:     10 * time.Second,
-		AdaptivePollingMinInterval:  5 * time.Second,
+		AdaptivePollingMinInterval:      5 * time.Second,
-		AdaptivePollingMaxInterval:  5 * time.Minute,
+		AdaptivePollingMaxInterval:      5 * time.Minute,
-		LogLevel:                    "info",
+		GuestMetadataMinRefreshInterval: DefaultGuestMetadataMinRefresh,
-		LogFormat:                   "auto",
+		GuestMetadataRefreshJitter:      DefaultGuestMetadataRefreshJitter,
-		LogMaxSize:                  100,
+		GuestMetadataRetryBackoff:       DefaultGuestMetadataRetryBackoff,
-		LogMaxAge:                   30,
+		GuestMetadataMaxConcurrent:      DefaultGuestMetadataMaxConcurrent,
-		LogCompress:                 true,
+		LogLevel:                        "info",
-		AllowedOrigins:              "", // Empty means no CORS headers (same-origin only)
+		LogFormat:                       "auto",
-		IframeEmbeddingAllow:        "SAMEORIGIN",
+		LogMaxSize:                      100,
-		PBSPollingInterval:          60 * time.Second, // Default PBS polling (slower)
+		LogMaxAge:                       30,
-		PMGPollingInterval:          60 * time.Second, // Default PMG polling (aggregated stats)
+		LogCompress:                     true,
-		DiscoveryEnabled:            false,
+		AllowedOrigins:                  "", // Empty means no CORS headers (same-origin only)
-		DiscoverySubnet:             "auto",
+		IframeEmbeddingAllow:            "SAMEORIGIN",
-		EnvOverrides:                make(map[string]bool),
+		PBSPollingInterval:              60 * time.Second, // Default PBS polling (slower)
-		OIDC:                        NewOIDCConfig(),
+		PMGPollingInterval:              60 * time.Second, // Default PMG polling (aggregated stats)
+		DiscoveryEnabled:                false,
+		DiscoverySubnet:                 "auto",
+		EnvOverrides:                    make(map[string]bool),
+		OIDC:                            NewOIDCConfig(),
 	}
 
 	cfg.Discovery = DefaultDiscoveryConfig()
@@ -725,6 +740,62 @@ func Load() (*Config, error) {
 		}
 	}
 
+	if minRefresh := strings.TrimSpace(os.Getenv("GUEST_METADATA_MIN_REFRESH_INTERVAL")); minRefresh != "" {
+		if dur, err := time.ParseDuration(minRefresh); err == nil {
+			if dur <= 0 {
+				log.Warn().Str("value", minRefresh).Msg("Ignoring non-positive GUEST_METADATA_MIN_REFRESH_INTERVAL from environment")
+			} else {
+				cfg.GuestMetadataMinRefreshInterval = dur
+				cfg.EnvOverrides["GUEST_METADATA_MIN_REFRESH_INTERVAL"] = true
+				log.Info().Dur("interval", dur).Msg("Guest metadata min refresh interval overridden by environment")
+			}
+		} else {
+			log.Warn().Str("value", minRefresh).Msg("Invalid GUEST_METADATA_MIN_REFRESH_INTERVAL value, expected duration string")
+		}
+	}
+
+	if jitter := strings.TrimSpace(os.Getenv("GUEST_METADATA_REFRESH_JITTER")); jitter != "" {
+		if dur, err := time.ParseDuration(jitter); err == nil {
+			if dur < 0 {
+				log.Warn().Str("value", jitter).Msg("Ignoring negative GUEST_METADATA_REFRESH_JITTER from environment")
+			} else {
+				cfg.GuestMetadataRefreshJitter = dur
+				cfg.EnvOverrides["GUEST_METADATA_REFRESH_JITTER"] = true
+				log.Info().Dur("jitter", dur).Msg("Guest metadata refresh jitter overridden by environment")
+			}
+		} else {
+			log.Warn().Str("value", jitter).Msg("Invalid GUEST_METADATA_REFRESH_JITTER value, expected duration string")
+		}
+	}
+
+	if backoff := strings.TrimSpace(os.Getenv("GUEST_METADATA_RETRY_BACKOFF")); backoff != "" {
+		if dur, err := time.ParseDuration(backoff); err == nil {
+			if dur <= 0 {
+				log.Warn().Str("value", backoff).Msg("Ignoring non-positive GUEST_METADATA_RETRY_BACKOFF from environment")
+			} else {
+				cfg.GuestMetadataRetryBackoff = dur
+				cfg.EnvOverrides["GUEST_METADATA_RETRY_BACKOFF"] = true
+				log.Info().Dur("backoff", dur).Msg("Guest metadata retry backoff overridden by environment")
+			}
+		} else {
+			log.Warn().Str("value", backoff).Msg("Invalid GUEST_METADATA_RETRY_BACKOFF value, expected duration string")
+		}
+	}
+
+	if concurrent := strings.TrimSpace(os.Getenv("GUEST_METADATA_MAX_CONCURRENT")); concurrent != "" {
+		if val, err := strconv.Atoi(concurrent); err == nil {
+			if val <= 0 {
+				log.Warn().Str("value", concurrent).Msg("Ignoring non-positive GUEST_METADATA_MAX_CONCURRENT from environment")
+			} else {
+				cfg.GuestMetadataMaxConcurrent = val
+				cfg.EnvOverrides["GUEST_METADATA_MAX_CONCURRENT"] = true
+				log.Info().Int("maxConcurrent", val).Msg("Guest metadata max concurrency overridden by environment")
+			}
+		} else {
+			log.Warn().Str("value", concurrent).Msg("Invalid GUEST_METADATA_MAX_CONCURRENT value, expected integer")
+		}
+	}
+
 	// Support both FRONTEND_PORT (preferred) and PORT (legacy) env vars
 	if frontendPort := os.Getenv("FRONTEND_PORT"); frontendPort != "" {
 		if p, err := strconv.Atoi(frontendPort); err == nil {

internal/config/guest_metadata.go

@@ -150,7 +150,7 @@ func (s *GuestMetadataStore) save() error {
 
 	log.Debug().Str("path", filePath).Msg("Saving guest metadata to disk")
 
-	data, err := json.MarshalIndent(s.metadata, "", "  ")
+	data, err := json.Marshal(s.metadata)
 	if err != nil {
 		return fmt.Errorf("failed to marshal metadata: %w", err)
 	}

internal/config/persistence.go

@@ -156,7 +156,7 @@ func (c *ConfigPersistence) SaveAPITokens(tokens []APITokenRecord) error {
 		sanitized[i] = record
 	}
 
-	data, err := json.MarshalIndent(sanitized, "", "  ")
+	data, err := json.Marshal(sanitized)
 	if err != nil {
 		return err
 	}
@@ -198,6 +198,32 @@ func (c *ConfigPersistence) SaveAlertConfig(config alerts.AlertConfig) error {
 	if config.HysteresisMargin <= 0 {
 		config.HysteresisMargin = 5.0
 	}
+
+	if config.HostDefaults.CPU == nil || config.HostDefaults.CPU.Trigger <= 0 {
+		config.HostDefaults.CPU = &alerts.HysteresisThreshold{Trigger: 80, Clear: 75}
+	} else if config.HostDefaults.CPU.Clear <= 0 {
+		config.HostDefaults.CPU.Clear = config.HostDefaults.CPU.Trigger - 5
+		if config.HostDefaults.CPU.Clear <= 0 {
+			config.HostDefaults.CPU.Clear = 75
+		}
+	}
+	if config.HostDefaults.Memory == nil || config.HostDefaults.Memory.Trigger <= 0 {
+		config.HostDefaults.Memory = &alerts.HysteresisThreshold{Trigger: 85, Clear: 80}
+	} else if config.HostDefaults.Memory.Clear <= 0 {
+		config.HostDefaults.Memory.Clear = config.HostDefaults.Memory.Trigger - 5
+		if config.HostDefaults.Memory.Clear <= 0 {
+			config.HostDefaults.Memory.Clear = 80
+		}
+	}
+	if config.HostDefaults.Disk == nil || config.HostDefaults.Disk.Trigger <= 0 {
+		config.HostDefaults.Disk = &alerts.HysteresisThreshold{Trigger: 90, Clear: 85}
+	} else if config.HostDefaults.Disk.Clear <= 0 {
+		config.HostDefaults.Disk.Clear = config.HostDefaults.Disk.Trigger - 5
+		if config.HostDefaults.Disk.Clear <= 0 {
+			config.HostDefaults.Disk.Clear = 85
+		}
+	}
+
 	config.MetricTimeThresholds = alerts.NormalizeMetricTimeThresholds(config.MetricTimeThresholds)
 	if config.TimeThreshold <= 0 {
 		config.TimeThreshold = 5
@@ -252,7 +278,7 @@ func (c *ConfigPersistence) SaveAlertConfig(config alerts.AlertConfig) error {
 	}
 	config.DockerIgnoredContainerPrefixes = alerts.NormalizeDockerIgnoredPrefixes(config.DockerIgnoredContainerPrefixes)
 
-	data, err := json.MarshalIndent(config, "", "  ")
+	data, err := json.Marshal(config)
 	if err != nil {
 		return err
 	}
@@ -291,6 +317,11 @@ func (c *ConfigPersistence) LoadAlertConfig() (*alerts.AlertConfig, error) {
 					Disk:        &alerts.HysteresisThreshold{Trigger: 90, Clear: 85},
 					Temperature: &alerts.HysteresisThreshold{Trigger: 80, Clear: 75},
 				},
+				HostDefaults: alerts.ThresholdConfig{
+					CPU:    &alerts.HysteresisThreshold{Trigger: 80, Clear: 75},
+					Memory: &alerts.HysteresisThreshold{Trigger: 85, Clear: 80},
+					Disk:   &alerts.HysteresisThreshold{Trigger: 90, Clear: 85},
+				},
 				StorageDefault: alerts.HysteresisThreshold{Trigger: 85, Clear: 80},
 				TimeThreshold:  5,
 				TimeThresholds: map[string]int{
@@ -346,6 +377,30 @@ func (c *ConfigPersistence) LoadAlertConfig() (*alerts.AlertConfig, error) {
 	if config.NodeDefaults.Temperature == nil || config.NodeDefaults.Temperature.Trigger <= 0 {
 		config.NodeDefaults.Temperature = &alerts.HysteresisThreshold{Trigger: 80, Clear: 75}
 	}
+	if config.HostDefaults.CPU == nil || config.HostDefaults.CPU.Trigger <= 0 {
+		config.HostDefaults.CPU = &alerts.HysteresisThreshold{Trigger: 80, Clear: 75}
+	} else if config.HostDefaults.CPU.Clear <= 0 {
+		config.HostDefaults.CPU.Clear = config.HostDefaults.CPU.Trigger - 5
+		if config.HostDefaults.CPU.Clear <= 0 {
+			config.HostDefaults.CPU.Clear = 75
+		}
+	}
+	if config.HostDefaults.Memory == nil || config.HostDefaults.Memory.Trigger <= 0 {
+		config.HostDefaults.Memory = &alerts.HysteresisThreshold{Trigger: 85, Clear: 80}
+	} else if config.HostDefaults.Memory.Clear <= 0 {
+		config.HostDefaults.Memory.Clear = config.HostDefaults.Memory.Trigger - 5
+		if config.HostDefaults.Memory.Clear <= 0 {
+			config.HostDefaults.Memory.Clear = 80
+		}
+	}
+	if config.HostDefaults.Disk == nil || config.HostDefaults.Disk.Trigger <= 0 {
+		config.HostDefaults.Disk = &alerts.HysteresisThreshold{Trigger: 90, Clear: 85}
+	} else if config.HostDefaults.Disk.Clear <= 0 {
+		config.HostDefaults.Disk.Clear = config.HostDefaults.Disk.Trigger - 5
+		if config.HostDefaults.Disk.Clear <= 0 {
+			config.HostDefaults.Disk.Clear = 85
+		}
+	}
 	if config.TimeThreshold <= 0 {
 		config.TimeThreshold = 5
 	}
@@ -425,7 +480,7 @@ func (c *ConfigPersistence) SaveEmailConfig(config notifications.EmailConfig) er
 	defer c.mu.Unlock()
 
 	// Marshal to JSON first
-	data, err := json.MarshalIndent(config, "", "  ")
+	data, err := json.Marshal(config)
 	if err != nil {
 		return err
 	}
@@ -502,7 +557,7 @@ func (c *ConfigPersistence) SaveAppriseConfig(config notifications.AppriseConfig
 
 	config = notifications.NormalizeAppriseConfig(config)
 
-	data, err := json.MarshalIndent(config, "", "  ")
+	data, err := json.Marshal(config)
 	if err != nil {
 		return err
 	}
@@ -578,7 +633,7 @@ func (c *ConfigPersistence) SaveWebhooks(webhooks []notifications.WebhookConfig)
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
-	data, err := json.MarshalIndent(webhooks, "", "  ")
+	data, err := json.Marshal(webhooks)
 	if err != nil {
 		return err
 	}
@@ -811,7 +866,7 @@ func (c *ConfigPersistence) saveNodesConfig(pveInstances []PVEInstance, pbsInsta
 		PMGInstances: pmgInstances,
 	}
 
-	data, err := json.MarshalIndent(config, "", "  ")
+	data, err := json.Marshal(config)
 	if err != nil {
 		return err
 	}
@@ -1123,7 +1178,7 @@ func (c *ConfigPersistence) SaveSystemSettings(settings SystemSettings) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
-	data, err := json.MarshalIndent(settings, "", "  ")
+	data, err := json.Marshal(settings)
 	if err != nil {
 		return err
 	}
@@ -1159,7 +1214,7 @@ func (c *ConfigPersistence) SaveOIDCConfig(settings OIDCConfig) error {
 	// Do not persist runtime-only flags.
 	settings.EnvOverrides = nil
 
-	data, err := json.MarshalIndent(settings, "", "  ")
+	data, err := json.Marshal(settings)
 	if err != nil {
 		return err
 	}

internal/monitoring/metrics.go

@@ -2,43 +2,53 @@ package monitoring
 
 import (
 	stdErrors "errors"
-	"fmt"
 	"strings"
 	"sync"
 	"time"
 
-	internalerrors "github.com/rcourtman/pulse-go-rewrite/internal/errors"
 	"github.com/prometheus/client_golang/prometheus"
+	internalerrors "github.com/rcourtman/pulse-go-rewrite/internal/errors"
 )
 
 // PollMetrics manages Prometheus instrumentation for polling activity.
 type PollMetrics struct {
-	pollDuration *prometheus.HistogramVec
+	pollDuration                 *prometheus.HistogramVec
-	pollResults  *prometheus.CounterVec
+	pollResults                  *prometheus.CounterVec
-	pollErrors   *prometheus.CounterVec
+	pollErrors                   *prometheus.CounterVec
-	lastSuccess  *prometheus.GaugeVec
+	lastSuccess                  *prometheus.GaugeVec
-	staleness    *prometheus.GaugeVec
+	staleness                    *prometheus.GaugeVec
-	queueDepth   prometheus.Gauge
+	queueDepth                   prometheus.Gauge
-	inflight     *prometheus.GaugeVec
+	inflight                     *prometheus.GaugeVec
-	nodePollDuration *prometheus.HistogramVec
+	nodePollDuration             *prometheus.HistogramVec
-	nodePollResults  *prometheus.CounterVec
+	nodePollResults              *prometheus.CounterVec
-	nodePollErrors   *prometheus.CounterVec
+	nodePollErrors               *prometheus.CounterVec
-	nodeLastSuccess  *prometheus.GaugeVec
+	nodeLastSuccess              *prometheus.GaugeVec
-	nodeStaleness    *prometheus.GaugeVec
+	nodeStaleness                *prometheus.GaugeVec
-	schedulerQueueReady        prometheus.Gauge
+	schedulerQueueReady          prometheus.Gauge
-	schedulerQueueDepthByType  *prometheus.GaugeVec
+	schedulerQueueDepthByType    *prometheus.GaugeVec
-	schedulerQueueWait         *prometheus.HistogramVec
+	schedulerQueueWait           *prometheus.HistogramVec
-	schedulerDeadLetterDepth   *prometheus.GaugeVec
+	schedulerDeadLetterDepth     *prometheus.GaugeVec
-	schedulerBreakerState      *prometheus.GaugeVec
+	schedulerBreakerState        *prometheus.GaugeVec
 	schedulerBreakerFailureCount *prometheus.GaugeVec
 	schedulerBreakerRetrySeconds *prometheus.GaugeVec
 
-	mu               sync.RWMutex
+	mu                   sync.RWMutex
-	lastSuccessByKey map[string]time.Time
+	lastSuccessByKey     map[metricKey]time.Time
-	nodeLastSuccessByKey map[string]time.Time
+	nodeLastSuccessByKey map[nodeMetricKey]time.Time
-	lastQueueTypeKeys map[string]struct{}
+	lastQueueTypeKeys    map[string]struct{}
-	lastDLQKeys       map[string]struct{}
+	lastDLQKeys          map[string]struct{}
-	pending          int
+	pending              int
+}
+
+type metricKey struct {
+	instanceType string
+	instance     string
+}
+
+type nodeMetricKey struct {
+	instanceType string
+	instance     string
+	node         string
 }
 
 var (
@@ -227,10 +237,10 @@ func newPollMetrics() *PollMetrics {
 			},
 			[]string{"instance_type", "instance"},
 		),
-		lastSuccessByKey:     make(map[string]time.Time),
+		lastSuccessByKey:     make(map[metricKey]time.Time),
-		nodeLastSuccessByKey: make(map[string]time.Time),
+		nodeLastSuccessByKey: make(map[nodeMetricKey]time.Time),
-		lastQueueTypeKeys:   make(map[string]struct{}),
+		lastQueueTypeKeys:    make(map[string]struct{}),
-		lastDLQKeys:         make(map[string]struct{}),
+		lastDLQKeys:          make(map[string]struct{}),
 	}
 
 	prometheus.MustRegister(
@@ -260,13 +270,13 @@ func newPollMetrics() *PollMetrics {
 
 // NodePollResult captures timing and outcome for a specific node within a poll cycle.
 type NodePollResult struct {
-    InstanceName string
+	InstanceName string
-    InstanceType string
+	InstanceType string
-    NodeName     string
+	NodeName     string
-    Success      bool
+	Success      bool
-    Error        error
+	Error        error
-    StartTime    time.Time
+	StartTime    time.Time
-    EndTime      time.Time
+	EndTime      time.Time
 }
 
 // RecordNodeResult records metrics for an individual node poll.
@@ -275,173 +285,136 @@ func (pm *PollMetrics) RecordNodeResult(result NodePollResult) {
 		return
 	}
 
-    nodeLabel := strings.TrimSpace(result.NodeName)
+	instType, inst := sanitizeInstanceLabels(result.InstanceType, result.InstanceName)
-    if nodeLabel == "" {
+	nodeLabel := normalizeNodeLabel(result.NodeName)
-        nodeLabel = "unknown-node"
-    }
 
-    labels := prometheus.Labels{
+	duration := result.EndTime.Sub(result.StartTime).Seconds()
-        "instance_type": result.InstanceType,
+	if duration < 0 {
-        "instance":      result.InstanceName,
+		duration = 0
-        "node":          nodeLabel,
+	}
-    }
+	pm.nodePollDuration.WithLabelValues(instType, inst, nodeLabel).Observe(duration)
 
-    duration := result.EndTime.Sub(result.StartTime).Seconds()
+	resultValue := "success"
-    if duration < 0 {
+	if !result.Success {
-        duration = 0
+		resultValue = "error"
-    }
+	}
-    pm.nodePollDuration.With(labels).Observe(duration)
+	pm.nodePollResults.WithLabelValues(instType, inst, nodeLabel, resultValue).Inc()
 
-    resultValue := "success"
+	if result.Success {
-    if !result.Success {
+		pm.nodeLastSuccess.WithLabelValues(instType, inst, nodeLabel).Set(float64(result.EndTime.Unix()))
-        resultValue = "error"
+		pm.storeNodeLastSuccess(instType, inst, nodeLabel, result.EndTime)
-    }
+		pm.updateNodeStaleness(instType, inst, nodeLabel, 0)
-    pm.nodePollResults.With(prometheus.Labels{
+		return
-        "instance_type": result.InstanceType,
+	}
-        "instance":      result.InstanceName,
-        "node":          nodeLabel,
-        "result":        resultValue,
-    }).Inc()
 
-    if result.Success {
+	errType := pm.classifyError(result.Error)
-        pm.nodeLastSuccess.With(labels).Set(float64(result.EndTime.Unix()))
+	pm.nodePollErrors.WithLabelValues(instType, inst, nodeLabel, errType).Inc()
-        pm.storeNodeLastSuccess(result.InstanceType, result.InstanceName, nodeLabel, result.EndTime)
-        pm.updateNodeStaleness(result.InstanceType, result.InstanceName, nodeLabel, 0)
-        return
-    }
 
-    errType := pm.classifyError(result.Error)
+	if last, ok := pm.lastNodeSuccessFor(instType, inst, nodeLabel); ok && !last.IsZero() {
-    pm.nodePollErrors.With(prometheus.Labels{
+		staleness := result.EndTime.Sub(last).Seconds()
-        "instance_type": result.InstanceType,
+		if staleness < 0 {
-        "instance":      result.InstanceName,
+			staleness = 0
-        "node":          nodeLabel,
+		}
-        "error_type":    errType,
+		pm.updateNodeStaleness(instType, inst, nodeLabel, staleness)
-    }).Inc()
+	} else {
-
+		pm.updateNodeStaleness(instType, inst, nodeLabel, -1)
-    if last, ok := pm.lastNodeSuccessFor(result.InstanceType, result.InstanceName, nodeLabel); ok && !last.IsZero() {
-        staleness := result.EndTime.Sub(last).Seconds()
-        if staleness < 0 {
-            staleness = 0
-        }
-        pm.updateNodeStaleness(result.InstanceType, result.InstanceName, nodeLabel, staleness)
-    } else {
-        pm.updateNodeStaleness(result.InstanceType, result.InstanceName, nodeLabel, -1)
 	}
 }
 
 // RecordQueueWait observes the time a task spent waiting in the scheduler queue.
 func (pm *PollMetrics) RecordQueueWait(instanceType string, wait time.Duration) {
-    if pm == nil {
+	if pm == nil {
-        return
+		return
-    }
+	}
-    if wait < 0 {
+	if wait < 0 {
-        wait = 0
+		wait = 0
-    }
+	}
-    instanceType = strings.TrimSpace(instanceType)
+	label := normalizeLabel(instanceType)
-    if instanceType == "" {
+	pm.schedulerQueueWait.WithLabelValues(label).Observe(wait.Seconds())
-        instanceType = "unknown"
-    }
-    pm.schedulerQueueWait.WithLabelValues(instanceType).Observe(wait.Seconds())
 }
 
 // UpdateQueueSnapshot updates scheduler queue depth metrics.
 func (pm *PollMetrics) UpdateQueueSnapshot(snapshot QueueSnapshot) {
-    if pm == nil {
+	if pm == nil {
-        return
+		return
-    }
+	}
 
-    pm.schedulerQueueReady.Set(float64(snapshot.DueWithinSeconds))
+	pm.schedulerQueueReady.Set(float64(snapshot.DueWithinSeconds))
 
-    current := make(map[string]struct{}, len(snapshot.PerType))
+	current := make(map[string]struct{}, len(snapshot.PerType))
-    for instanceType, depth := range snapshot.PerType {
+	for instanceType, depth := range snapshot.PerType {
-        key := strings.TrimSpace(instanceType)
+		key := normalizeLabel(instanceType)
-        if key == "" {
+		pm.schedulerQueueDepthByType.WithLabelValues(key).Set(float64(depth))
-            key = "unknown"
+		current[key] = struct{}{}
-        }
+	}
-        pm.schedulerQueueDepthByType.WithLabelValues(key).Set(float64(depth))
-        current[key] = struct{}{}
-    }
 
-    pm.mu.Lock()
+	pm.mu.Lock()
-    for key := range pm.lastQueueTypeKeys {
+	for key := range pm.lastQueueTypeKeys {
-        if _, ok := current[key]; !ok {
+		if _, ok := current[key]; !ok {
-            pm.schedulerQueueDepthByType.WithLabelValues(key).Set(0)
+			pm.schedulerQueueDepthByType.WithLabelValues(key).Set(0)
-        }
+		}
-    }
+	}
-    pm.lastQueueTypeKeys = current
+	pm.lastQueueTypeKeys = current
-    pm.mu.Unlock()
+	pm.mu.Unlock()
 }
 
 // UpdateDeadLetterCounts refreshes dead-letter queue gauges based on the provided tasks.
 func (pm *PollMetrics) UpdateDeadLetterCounts(tasks []DeadLetterTask) {
-    if pm == nil {
+	if pm == nil {
-        return
+		return
-    }
+	}
 
-    current := make(map[string]float64)
+	current := make(map[string]float64)
-    for _, task := range tasks {
+	for _, task := range tasks {
-        instType := strings.TrimSpace(task.Type)
+		instType := normalizeLabel(task.Type)
-        if instType == "" {
+		inst := normalizeLabel(task.Instance)
-            instType = "unknown"
+		key := instType + "::" + inst
-        }
+		current[key] = current[key] + 1
-        inst := strings.TrimSpace(task.Instance)
+	}
-        if inst == "" {
-            inst = "unknown"
-        }
-        key := instType + "::" + inst
-        current[key] = current[key] + 1
-    }
 
-    pm.mu.Lock()
+	pm.mu.Lock()
-    prev := pm.lastDLQKeys
+	prev := pm.lastDLQKeys
-    pm.lastDLQKeys = make(map[string]struct{}, len(current))
+	pm.lastDLQKeys = make(map[string]struct{}, len(current))
-    pm.mu.Unlock()
+	pm.mu.Unlock()
 
-    for key, count := range current {
+	for key, count := range current {
-        instType, inst := splitInstanceKey(key)
+		instType, inst := splitInstanceKey(key)
-        pm.schedulerDeadLetterDepth.WithLabelValues(instType, inst).Set(count)
+		pm.schedulerDeadLetterDepth.WithLabelValues(instType, inst).Set(count)
-    }
+	}
 
-    pm.mu.Lock()
+	pm.mu.Lock()
-    for key := range current {
+	for key := range current {
-        pm.lastDLQKeys[key] = struct{}{}
+		pm.lastDLQKeys[key] = struct{}{}
-    }
+	}
-    for key := range prev {
+	for key := range prev {
-        if _, ok := current[key]; !ok {
+		if _, ok := current[key]; !ok {
-            instType, inst := splitInstanceKey(key)
+			instType, inst := splitInstanceKey(key)
-            pm.schedulerDeadLetterDepth.WithLabelValues(instType, inst).Set(0)
+			pm.schedulerDeadLetterDepth.WithLabelValues(instType, inst).Set(0)
-        }
+		}
-    }
+	}
-    pm.mu.Unlock()
+	pm.mu.Unlock()
 }
 
 // SetBreakerState updates circuit breaker metrics for a specific instance.
 func (pm *PollMetrics) SetBreakerState(instanceType, instance, state string, failures int, retryAt time.Time) {
-    if pm == nil {
+	if pm == nil {
-        return
+		return
-    }
+	}
 
-    instType := strings.TrimSpace(instanceType)
+	instType, inst := sanitizeInstanceLabels(instanceType, instance)
-    if instType == "" {
-        instType = "unknown"
-    }
-    inst := strings.TrimSpace(instance)
-    if inst == "" {
-        inst = "unknown"
-    }
 
 	value := breakerStateToValue(state)
 	pm.schedulerBreakerState.WithLabelValues(instType, inst).Set(value)
 	pm.schedulerBreakerFailureCount.WithLabelValues(instType, inst).Set(float64(failures))
 
-    retrySeconds := 0.0
+	retrySeconds := 0.0
-    if !retryAt.IsZero() {
+	if !retryAt.IsZero() {
-        retrySeconds = retryAt.Sub(time.Now()).Seconds()
+		retrySeconds = retryAt.Sub(time.Now()).Seconds()
-        if retrySeconds < 0 {
+		if retrySeconds < 0 {
-            retrySeconds = 0
+			retrySeconds = 0
-        }
+		}
-    }
+	}
-    pm.schedulerBreakerRetrySeconds.WithLabelValues(instType, inst).Set(retrySeconds)
+	pm.schedulerBreakerRetrySeconds.WithLabelValues(instType, inst).Set(retrySeconds)
 }
 
 // RecordResult records metrics for a polling result.
@@ -450,47 +423,36 @@ func (pm *PollMetrics) RecordResult(result PollResult) {
 		return
 	}
 
-	labels := prometheus.Labels{
+	instType, inst := sanitizeInstanceLabels(result.InstanceType, result.InstanceName)
-		"instance_type": result.InstanceType,
-		"instance":      result.InstanceName,
-	}
 
 	duration := result.EndTime.Sub(result.StartTime).Seconds()
 	if duration < 0 {
 		duration = 0
 	}
-	pm.pollDuration.With(labels).Observe(duration)
+	pm.pollDuration.WithLabelValues(instType, inst).Observe(duration)
 
 	resultValue := "success"
 	if !result.Success {
 		resultValue = "error"
 	}
-	pm.pollResults.With(prometheus.Labels{
+	pm.pollResults.WithLabelValues(instType, inst, resultValue).Inc()
-		"instance_type": result.InstanceType,
-		"instance":      result.InstanceName,
-		"result":        resultValue,
-	}).Inc()
 
 	if result.Success {
-		pm.lastSuccess.With(labels).Set(float64(result.EndTime.Unix()))
+		pm.lastSuccess.WithLabelValues(instType, inst).Set(float64(result.EndTime.Unix()))
-		pm.storeLastSuccess(result.InstanceType, result.InstanceName, result.EndTime)
+		pm.storeLastSuccess(instType, inst, result.EndTime)
-		pm.updateStaleness(result.InstanceType, result.InstanceName, 0)
+		pm.updateStaleness(instType, inst, 0)
 	} else {
 		errType := pm.classifyError(result.Error)
-		pm.pollErrors.With(prometheus.Labels{
+		pm.pollErrors.WithLabelValues(instType, inst, errType).Inc()
-			"instance_type": result.InstanceType,
-			"instance":      result.InstanceName,
-			"error_type":    errType,
-		}).Inc()
 
-		if last, ok := pm.lastSuccessFor(result.InstanceType, result.InstanceName); ok && !last.IsZero() {
+		if last, ok := pm.lastSuccessFor(instType, inst); ok && !last.IsZero() {
 			staleness := result.EndTime.Sub(last).Seconds()
 			if staleness < 0 {
 				staleness = 0
 			}
-			pm.updateStaleness(result.InstanceType, result.InstanceName, staleness)
+			pm.updateStaleness(instType, inst, staleness)
 		} else {
-			pm.updateStaleness(result.InstanceType, result.InstanceName, -1)
+			pm.updateStaleness(instType, inst, -1)
 		}
 	}
 
@@ -555,75 +517,101 @@ func (pm *PollMetrics) decrementPending() {
 }
 
 func (pm *PollMetrics) storeLastSuccess(instanceType, instance string, ts time.Time) {
-    pm.mu.Lock()
+	pm.mu.Lock()
-    pm.lastSuccessByKey[pm.key(instanceType, instance)] = ts
+	pm.lastSuccessByKey[makeMetricKey(instanceType, instance)] = ts
-    pm.mu.Unlock()
+	pm.mu.Unlock()
 }
 
 func (pm *PollMetrics) lastSuccessFor(instanceType, instance string) (time.Time, bool) {
 	pm.mu.RLock()
-	ts, ok := pm.lastSuccessByKey[pm.key(instanceType, instance)]
+	ts, ok := pm.lastSuccessByKey[makeMetricKey(instanceType, instance)]
 	pm.mu.RUnlock()
 	return ts, ok
 }
 
 func (pm *PollMetrics) updateStaleness(instanceType, instance string, value float64) {
-	pm.staleness.WithLabelValues(instanceType, instance).Set(value)
+	instType, inst := sanitizeInstanceLabels(instanceType, instance)
-}
+	pm.staleness.WithLabelValues(instType, inst).Set(value)
-
-func (pm *PollMetrics) key(instanceType, instance string) string {
-	return fmt.Sprintf("%s::%s", instanceType, instance)
 }
 
 func (pm *PollMetrics) storeNodeLastSuccess(instanceType, instance, node string, ts time.Time) {
 	pm.mu.Lock()
-	pm.nodeLastSuccessByKey[pm.nodeKey(instanceType, instance, node)] = ts
+	pm.nodeLastSuccessByKey[makeNodeMetricKey(instanceType, instance, node)] = ts
 	pm.mu.Unlock()
 }
 
 func (pm *PollMetrics) lastNodeSuccessFor(instanceType, instance, node string) (time.Time, bool) {
 	pm.mu.RLock()
-	ts, ok := pm.nodeLastSuccessByKey[pm.nodeKey(instanceType, instance, node)]
+	ts, ok := pm.nodeLastSuccessByKey[makeNodeMetricKey(instanceType, instance, node)]
 	pm.mu.RUnlock()
 	return ts, ok
 }
 
 func (pm *PollMetrics) updateNodeStaleness(instanceType, instance, node string, value float64) {
-	pm.nodeStaleness.WithLabelValues(instanceType, instance, node).Set(value)
+	instType, inst := sanitizeInstanceLabels(instanceType, instance)
-}
+	nodeLabel := normalizeLabel(node)
-
+	pm.nodeStaleness.WithLabelValues(instType, inst, nodeLabel).Set(value)
-func (pm *PollMetrics) nodeKey(instanceType, instance, node string) string {
-	return fmt.Sprintf("%s::%s::%s", instanceType, instance, node)
 }
 
 func splitInstanceKey(key string) (string, string) {
-    parts := strings.SplitN(key, "::", 2)
+	parts := strings.SplitN(key, "::", 2)
-    if len(parts) == 2 {
+	if len(parts) == 2 {
-        if parts[0] == "" {
+		return normalizeLabel(parts[0]), normalizeLabel(parts[1])
-            parts[0] = "unknown"
+	}
-        }
+	if key == "" {
-        if parts[1] == "" {
+		return "unknown", "unknown"
-            parts[1] = "unknown"
+	}
-        }
+	return "unknown", normalizeLabel(key)
-        return parts[0], parts[1]
-    }
-    if key == "" {
-        return "unknown", "unknown"
-    }
-    return "unknown", key
 }
 
 func breakerStateToValue(state string) float64 {
-    switch strings.ToLower(state) {
+	switch strings.ToLower(state) {
-    case "closed":
+	case "closed":
-        return 0
+		return 0
-    case "half_open", "half-open":
+	case "half_open", "half-open":
-        return 1
+		return 1
-    case "open":
+	case "open":
-        return 2
+		return 2
-    default:
+	default:
-        return -1
+		return -1
-    }
+	}
+}
+
+func sanitizeInstanceLabels(instanceType, instance string) (string, string) {
+	return normalizeLabel(instanceType), normalizeLabel(instance)
+}
+
+func makeMetricKey(instanceType, instance string) metricKey {
+	instType, inst := sanitizeInstanceLabels(instanceType, instance)
+	return metricKey{
+		instanceType: instType,
+		instance:     inst,
+	}
+}
+
+func makeNodeMetricKey(instanceType, instance, node string) nodeMetricKey {
+	instType, inst := sanitizeInstanceLabels(instanceType, instance)
+	return nodeMetricKey{
+		instanceType: instType,
+		instance:     inst,
+		node:         normalizeLabel(node),
+	}
+}
+
+func normalizeLabel(value string) string {
+	v := strings.TrimSpace(value)
+	if v == "" {
+		return "unknown"
+	}
+	return v
+}
+
+func normalizeNodeLabel(value string) string {
+	label := normalizeLabel(value)
+	if label == "unknown" {
+		return "unknown-node"
+	}
+	return label
 }
 
 func (pm *PollMetrics) classifyError(err error) string {

internal/monitoring/monitor.go

@@ -421,60 +421,67 @@ func timePtr(t time.Time) *time.Time {
 
 // Monitor handles all monitoring operations
 type Monitor struct {
-	config                *config.Config
+	config                     *config.Config
-	state                 *models.State
+	state                      *models.State
-	pveClients            map[string]PVEClientInterface
+	pveClients                 map[string]PVEClientInterface
-	pbsClients            map[string]*pbs.Client
+	pbsClients                 map[string]*pbs.Client
-	pmgClients            map[string]*pmg.Client
+	pmgClients                 map[string]*pmg.Client
-	pollMetrics           *PollMetrics
+	pollMetrics                *PollMetrics
-	scheduler             *AdaptiveScheduler
+	scheduler                  *AdaptiveScheduler
-	stalenessTracker      *StalenessTracker
+	stalenessTracker           *StalenessTracker
-	taskQueue             *TaskQueue
+	taskQueue                  *TaskQueue
-	circuitBreakers       map[string]*circuitBreaker
+	circuitBreakers            map[string]*circuitBreaker
-	deadLetterQueue       *TaskQueue
+	deadLetterQueue            *TaskQueue
-	failureCounts         map[string]int
+	failureCounts              map[string]int
-	lastOutcome           map[string]taskOutcome
+	lastOutcome                map[string]taskOutcome
-	backoffCfg            backoffConfig
+	backoffCfg                 backoffConfig
-	rng                   *rand.Rand
+	rng                        *rand.Rand
-	maxRetryAttempts      int
+	maxRetryAttempts           int
-	tempCollector         *TemperatureCollector // SSH-based temperature collector
+	tempCollector              *TemperatureCollector // SSH-based temperature collector
-	mu                    sync.RWMutex
+	mu                         sync.RWMutex
-	startTime             time.Time
+	startTime                  time.Time
-	rateTracker           *RateTracker
+	rateTracker                *RateTracker
-	metricsHistory        *MetricsHistory
+	metricsHistory             *MetricsHistory
-	alertManager          *alerts.Manager
+	alertManager               *alerts.Manager
-	notificationMgr       *notifications.NotificationManager
+	notificationMgr            *notifications.NotificationManager
-	configPersist         *config.ConfigPersistence
+	configPersist              *config.ConfigPersistence
-	discoveryService      *discovery.Service        // Background discovery service
+	discoveryService           *discovery.Service        // Background discovery service
-	activePollCount       int32                     // Number of active polling operations
+	activePollCount            int32                     // Number of active polling operations
-	pollCounter           int64                     // Counter for polling cycles
+	pollCounter                int64                     // Counter for polling cycles
-	authFailures          map[string]int            // Track consecutive auth failures per node
+	authFailures               map[string]int            // Track consecutive auth failures per node
-	lastAuthAttempt       map[string]time.Time      // Track last auth attempt time
+	lastAuthAttempt            map[string]time.Time      // Track last auth attempt time
-	lastClusterCheck      map[string]time.Time      // Track last cluster check for standalone nodes
+	lastClusterCheck           map[string]time.Time      // Track last cluster check for standalone nodes
-	lastPhysicalDiskPoll  map[string]time.Time      // Track last physical disk poll time per instance
+	lastPhysicalDiskPoll       map[string]time.Time      // Track last physical disk poll time per instance
-	lastPVEBackupPoll     map[string]time.Time      // Track last PVE backup poll per instance
+	lastPVEBackupPoll          map[string]time.Time      // Track last PVE backup poll per instance
-	lastPBSBackupPoll     map[string]time.Time      // Track last PBS backup poll per instance
+	lastPBSBackupPoll          map[string]time.Time      // Track last PBS backup poll per instance
-	persistence           *config.ConfigPersistence // Add persistence for saving updated configs
+	persistence                *config.ConfigPersistence // Add persistence for saving updated configs
-	pbsBackupPollers      map[string]bool           // Track PBS backup polling goroutines per instance
+	pbsBackupPollers           map[string]bool           // Track PBS backup polling goroutines per instance
-	runtimeCtx            context.Context           // Context used while monitor is running
+	runtimeCtx                 context.Context           // Context used while monitor is running
-	wsHub                 *websocket.Hub            // Hub used for broadcasting state
+	wsHub                      *websocket.Hub            // Hub used for broadcasting state
-	diagMu                sync.RWMutex              // Protects diagnostic snapshot maps
+	diagMu                     sync.RWMutex              // Protects diagnostic snapshot maps
-	nodeSnapshots         map[string]NodeMemorySnapshot
+	nodeSnapshots              map[string]NodeMemorySnapshot
-	guestSnapshots        map[string]GuestMemorySnapshot
+	guestSnapshots             map[string]GuestMemorySnapshot
-	rrdCacheMu            sync.RWMutex // Protects RRD memavailable cache
+	rrdCacheMu                 sync.RWMutex // Protects RRD memavailable cache
-	nodeRRDMemCache       map[string]rrdMemCacheEntry
+	nodeRRDMemCache            map[string]rrdMemCacheEntry
-	removedDockerHosts    map[string]time.Time // Track deliberately removed Docker hosts (ID -> removal time)
+	removedDockerHosts         map[string]time.Time // Track deliberately removed Docker hosts (ID -> removal time)
-	dockerCommands        map[string]*dockerHostCommand
+	dockerCommands             map[string]*dockerHostCommand
-	dockerCommandIndex    map[string]string
+	dockerCommandIndex         map[string]string
-	guestMetadataMu       sync.RWMutex
+	guestMetadataMu            sync.RWMutex
-	guestMetadataCache    map[string]guestMetadataCacheEntry
+	guestMetadataCache         map[string]guestMetadataCacheEntry
-	executor              PollExecutor
+	guestMetadataLimiterMu     sync.Mutex
-	breakerBaseRetry      time.Duration
+	guestMetadataLimiter       map[string]time.Time
-	breakerMaxDelay       time.Duration
+	guestMetadataSlots         chan struct{}
-	breakerHalfOpenWindow time.Duration
+	guestMetadataMinRefresh    time.Duration
-	instanceInfoCache     map[string]*instanceInfo
+	guestMetadataRefreshJitter time.Duration
-	pollStatusMap         map[string]*pollStatus
+	guestMetadataRetryBackoff  time.Duration
-	dlqInsightMap         map[string]*dlqInsight
+	guestMetadataHoldDuration  time.Duration
+	executor                   PollExecutor
+	breakerBaseRetry           time.Duration
+	breakerMaxDelay            time.Duration
+	breakerHalfOpenWindow      time.Duration
+	instanceInfoCache          map[string]*instanceInfo
+	pollStatusMap              map[string]*pollStatus
+	dlqInsightMap              map[string]*dlqInsight
 }
 
 type rrdMemCacheEntry struct {
@@ -565,9 +572,13 @@ const (
 	dockerOfflineGraceMultiplier = 4
 	dockerMinimumHealthWindow    = 30 * time.Second
 	dockerMaximumHealthWindow    = 10 * time.Minute
+	hostOfflineGraceMultiplier   = 4
+	hostMinimumHealthWindow      = 30 * time.Second
+	hostMaximumHealthWindow      = 10 * time.Minute
 	nodeRRDCacheTTL              = 30 * time.Second
 	nodeRRDRequestTimeout        = 2 * time.Second
 	guestMetadataCacheTTL        = 5 * time.Minute
+	defaultGuestMetadataHold     = 15 * time.Second
 )
 
 type guestMetadataCacheEntry struct {
@@ -728,6 +739,10 @@ func (m *Monitor) RemoveHostAgent(hostID string) (models.Host, error) {
 		Bool("removed", removed).
 		Msg("Host agent removed from monitoring")
 
+	if m.alertManager != nil {
+		m.alertManager.HandleHostRemoved(host)
+	}
+
 	return host, nil
 }
 
@@ -1471,6 +1486,10 @@ func (m *Monitor) ApplyHostReport(report agentshost.Report, tokenRecord *config.
 	m.state.UpsertHost(host)
 	m.state.SetConnectionHealth(hostConnectionPrefix+host.ID, true)
 
+	if m.alertManager != nil {
+		m.alertManager.CheckHost(host)
+	}
+
 	return host, nil
 }
 
@@ -1530,6 +1549,43 @@ func (m *Monitor) evaluateDockerAgents(now time.Time) {
 	}
 }
 
+// evaluateHostAgents updates health for host agents based on last report time.
+func (m *Monitor) evaluateHostAgents(now time.Time) {
+	hosts := m.state.GetHosts()
+	for _, host := range hosts {
+		interval := host.IntervalSeconds
+		if interval <= 0 {
+			interval = int(hostMinimumHealthWindow / time.Second)
+		}
+
+		window := time.Duration(interval) * time.Second * hostOfflineGraceMultiplier
+		if window < hostMinimumHealthWindow {
+			window = hostMinimumHealthWindow
+		} else if window > hostMaximumHealthWindow {
+			window = hostMaximumHealthWindow
+		}
+
+		healthy := !host.LastSeen.IsZero() && now.Sub(host.LastSeen) <= window
+		key := hostConnectionPrefix + host.ID
+		m.state.SetConnectionHealth(key, healthy)
+
+		hostCopy := host
+		if healthy {
+			hostCopy.Status = "online"
+			m.state.SetHostStatus(host.ID, "online")
+			if m.alertManager != nil {
+				m.alertManager.HandleHostOnline(hostCopy)
+			}
+		} else {
+			hostCopy.Status = "offline"
+			m.state.SetHostStatus(host.ID, "offline")
+			if m.alertManager != nil {
+				m.alertManager.HandleHostOffline(hostCopy)
+			}
+		}
+	}
+}
+
 // sortContent sorts comma-separated content values for consistent display
 func sortContent(content string) string {
 	if content == "" {
@@ -1540,6 +1596,76 @@ func sortContent(content string) string {
 	return strings.Join(parts, ",")
 }
 
+func (m *Monitor) tryReserveGuestMetadataFetch(key string, now time.Time) bool {
+	if m == nil {
+		return false
+	}
+	m.guestMetadataLimiterMu.Lock()
+	defer m.guestMetadataLimiterMu.Unlock()
+
+	if next, ok := m.guestMetadataLimiter[key]; ok && now.Before(next) {
+		return false
+	}
+	hold := m.guestMetadataHoldDuration
+	if hold <= 0 {
+		hold = defaultGuestMetadataHold
+	}
+	m.guestMetadataLimiter[key] = now.Add(hold)
+	return true
+}
+
+func (m *Monitor) scheduleNextGuestMetadataFetch(key string, now time.Time) {
+	if m == nil {
+		return
+	}
+	interval := m.guestMetadataMinRefresh
+	if interval <= 0 {
+		interval = config.DefaultGuestMetadataMinRefresh
+	}
+	jitter := m.guestMetadataRefreshJitter
+	if jitter > 0 && m.rng != nil {
+		interval += time.Duration(m.rng.Int63n(int64(jitter)))
+	}
+	m.guestMetadataLimiterMu.Lock()
+	m.guestMetadataLimiter[key] = now.Add(interval)
+	m.guestMetadataLimiterMu.Unlock()
+}
+
+func (m *Monitor) deferGuestMetadataRetry(key string, now time.Time) {
+	if m == nil {
+		return
+	}
+	backoff := m.guestMetadataRetryBackoff
+	if backoff <= 0 {
+		backoff = config.DefaultGuestMetadataRetryBackoff
+	}
+	m.guestMetadataLimiterMu.Lock()
+	m.guestMetadataLimiter[key] = now.Add(backoff)
+	m.guestMetadataLimiterMu.Unlock()
+}
+
+func (m *Monitor) acquireGuestMetadataSlot(ctx context.Context) bool {
+	if m == nil || m.guestMetadataSlots == nil {
+		return true
+	}
+	select {
+	case m.guestMetadataSlots <- struct{}{}:
+		return true
+	case <-ctx.Done():
+		return false
+	}
+}
+
+func (m *Monitor) releaseGuestMetadataSlot() {
+	if m == nil || m.guestMetadataSlots == nil {
+		return
+	}
+	select {
+	case <-m.guestMetadataSlots:
+	default:
+	}
+}
+
 func (m *Monitor) fetchGuestAgentMetadata(ctx context.Context, client PVEClientInterface, instanceName, nodeName, vmName string, vmid int, vmStatus *proxmox.VMStatus) ([]string, []models.GuestNetworkInterface, string, string, string) {
 	if vmStatus == nil || client == nil {
 		m.clearGuestMetadataCache(instanceName, nodeName, vmid)
@@ -1562,6 +1688,19 @@ func (m *Monitor) fetchGuestAgentMetadata(ctx context.Context, client PVEClientI
 		return cloneStringSlice(cached.ipAddresses), cloneGuestNetworkInterfaces(cached.networkInterfaces), cached.osName, cached.osVersion, cached.agentVersion
 	}
 
+	needsFetch := !ok || now.Sub(cached.fetchedAt) >= guestMetadataCacheTTL
+	if !needsFetch {
+		return cloneStringSlice(cached.ipAddresses), cloneGuestNetworkInterfaces(cached.networkInterfaces), cached.osName, cached.osVersion, cached.agentVersion
+	}
+
+	reserved := m.tryReserveGuestMetadataFetch(key, now)
+	if !reserved && ok {
+		return cloneStringSlice(cached.ipAddresses), cloneGuestNetworkInterfaces(cached.networkInterfaces), cached.osName, cached.osVersion, cached.agentVersion
+	}
+	if !reserved && !ok {
+		reserved = true
+	}
+
 	// Start with cached values as fallback in case new calls fail
 	ipAddresses := cloneStringSlice(cached.ipAddresses)
 	networkIfaces := cloneGuestNetworkInterfaces(cached.networkInterfaces)
@@ -1569,6 +1708,17 @@ func (m *Monitor) fetchGuestAgentMetadata(ctx context.Context, client PVEClientI
 	osVersion := cached.osVersion
 	agentVersion := cached.agentVersion
 
+	if reserved {
+		if !m.acquireGuestMetadataSlot(ctx) {
+			m.deferGuestMetadataRetry(key, time.Now())
+			return ipAddresses, networkIfaces, osName, osVersion, agentVersion
+		}
+		defer m.releaseGuestMetadataSlot()
+		defer func() {
+			m.scheduleNextGuestMetadataFetch(key, time.Now())
+		}()
+	}
+
 	ifaceCtx, cancelIface := context.WithTimeout(ctx, 5*time.Second)
 	interfaces, err := client.GetVMNetworkInterfaces(ifaceCtx, nodeName, vmid)
 	cancelIface()
@@ -2584,49 +2734,72 @@ func New(cfg *config.Config) (*Monitor, error) {
 		}, stalenessTracker, nil, nil)
 	}
 
+	minRefresh := cfg.GuestMetadataMinRefreshInterval
+	if minRefresh <= 0 {
+		minRefresh = config.DefaultGuestMetadataMinRefresh
+	}
+	jitter := cfg.GuestMetadataRefreshJitter
+	if jitter < 0 {
+		jitter = 0
+	}
+	retryBackoff := cfg.GuestMetadataRetryBackoff
+	if retryBackoff <= 0 {
+		retryBackoff = config.DefaultGuestMetadataRetryBackoff
+	}
+	concurrency := cfg.GuestMetadataMaxConcurrent
+	if concurrency <= 0 {
+		concurrency = config.DefaultGuestMetadataMaxConcurrent
+	}
+	holdDuration := defaultGuestMetadataHold
+
 	m := &Monitor{
-		config:               cfg,
+		config:                     cfg,
-		state:                models.NewState(),
+		state:                      models.NewState(),
-		pveClients:           make(map[string]PVEClientInterface),
+		pveClients:                 make(map[string]PVEClientInterface),
-		pbsClients:           make(map[string]*pbs.Client),
+		pbsClients:                 make(map[string]*pbs.Client),
-		pmgClients:           make(map[string]*pmg.Client),
+		pmgClients:                 make(map[string]*pmg.Client),
-		pollMetrics:          getPollMetrics(),
+		pollMetrics:                getPollMetrics(),
-		scheduler:            scheduler,
+		scheduler:                  scheduler,
-		stalenessTracker:     stalenessTracker,
+		stalenessTracker:           stalenessTracker,
-		taskQueue:            taskQueue,
+		taskQueue:                  taskQueue,
-		deadLetterQueue:      deadLetterQueue,
+		deadLetterQueue:            deadLetterQueue,
-		circuitBreakers:      breakers,
+		circuitBreakers:            breakers,
-		failureCounts:        failureCounts,
+		failureCounts:              failureCounts,
-		lastOutcome:          lastOutcome,
+		lastOutcome:                lastOutcome,
-		backoffCfg:           backoff,
+		backoffCfg:                 backoff,
-		rng:                  rand.New(rand.NewSource(time.Now().UnixNano())),
+		rng:                        rand.New(rand.NewSource(time.Now().UnixNano())),
-		maxRetryAttempts:     5,
+		maxRetryAttempts:           5,
-		tempCollector:        tempCollector,
+		tempCollector:              tempCollector,
-		startTime:            time.Now(),
+		startTime:                  time.Now(),
-		rateTracker:          NewRateTracker(),
+		rateTracker:                NewRateTracker(),
-		metricsHistory:       NewMetricsHistory(1000, 24*time.Hour), // Keep up to 1000 points or 24 hours
+		metricsHistory:             NewMetricsHistory(1000, 24*time.Hour), // Keep up to 1000 points or 24 hours
-		alertManager:         alerts.NewManager(),
+		alertManager:               alerts.NewManager(),
-		notificationMgr:      notifications.NewNotificationManager(cfg.PublicURL),
+		notificationMgr:            notifications.NewNotificationManager(cfg.PublicURL),
-		configPersist:        config.NewConfigPersistence(cfg.DataPath),
+		configPersist:              config.NewConfigPersistence(cfg.DataPath),
-		discoveryService:     nil, // Will be initialized in Start()
+		discoveryService:           nil, // Will be initialized in Start()
-		authFailures:         make(map[string]int),
+		authFailures:               make(map[string]int),
-		lastAuthAttempt:      make(map[string]time.Time),
+		lastAuthAttempt:            make(map[string]time.Time),
-		lastClusterCheck:     make(map[string]time.Time),
+		lastClusterCheck:           make(map[string]time.Time),
-		lastPhysicalDiskPoll: make(map[string]time.Time),
+		lastPhysicalDiskPoll:       make(map[string]time.Time),
-		lastPVEBackupPoll:    make(map[string]time.Time),
+		lastPVEBackupPoll:          make(map[string]time.Time),
-		lastPBSBackupPoll:    make(map[string]time.Time),
+		lastPBSBackupPoll:          make(map[string]time.Time),
-		persistence:          config.NewConfigPersistence(cfg.DataPath),
+		persistence:                config.NewConfigPersistence(cfg.DataPath),
-		pbsBackupPollers:     make(map[string]bool),
+		pbsBackupPollers:           make(map[string]bool),
-		nodeSnapshots:        make(map[string]NodeMemorySnapshot),
+		nodeSnapshots:              make(map[string]NodeMemorySnapshot),
-		guestSnapshots:       make(map[string]GuestMemorySnapshot),
+		guestSnapshots:             make(map[string]GuestMemorySnapshot),
-		nodeRRDMemCache:      make(map[string]rrdMemCacheEntry),
+		nodeRRDMemCache:            make(map[string]rrdMemCacheEntry),
-		removedDockerHosts:   make(map[string]time.Time),
+		removedDockerHosts:         make(map[string]time.Time),
-		dockerCommands:       make(map[string]*dockerHostCommand),
+		dockerCommands:             make(map[string]*dockerHostCommand),
-		dockerCommandIndex:   make(map[string]string),
+		dockerCommandIndex:         make(map[string]string),
-		guestMetadataCache:   make(map[string]guestMetadataCacheEntry),
+		guestMetadataCache:         make(map[string]guestMetadataCacheEntry),
-		instanceInfoCache:    make(map[string]*instanceInfo),
+		guestMetadataLimiter:       make(map[string]time.Time),
-		pollStatusMap:        make(map[string]*pollStatus),
+		guestMetadataMinRefresh:    minRefresh,
-		dlqInsightMap:        make(map[string]*dlqInsight),
+		guestMetadataRefreshJitter: jitter,
+		guestMetadataRetryBackoff:  retryBackoff,
+		guestMetadataHoldDuration:  holdDuration,
+		instanceInfoCache:          make(map[string]*instanceInfo),
+		pollStatusMap:              make(map[string]*pollStatus),
+		dlqInsightMap:              make(map[string]*dlqInsight),
 	}
 
 	m.breakerBaseRetry = 5 * time.Second
@@ -2672,6 +2845,10 @@ func New(cfg *config.Config) (*Monitor, error) {
 		log.Warn().Err(err).Msg("Failed to load email configuration")
 	}
 
+	if concurrency > 0 {
+		m.guestMetadataSlots = make(chan struct{}, concurrency)
+	}
+
 	if appriseConfig, err := m.configPersist.LoadAppriseConfig(); err == nil {
 		m.notificationMgr.SetAppriseConfig(*appriseConfig)
 	} else {
@@ -3103,6 +3280,7 @@ func (m *Monitor) Start(ctx context.Context, wsHub *websocket.Hub) {
 		case <-pollTicker.C:
 			now := time.Now()
 			m.evaluateDockerAgents(now)
+			m.evaluateHostAgents(now)
 			m.cleanupRemovedDockerHosts(now)
 			if mock.IsMockEnabled() {
 				// In mock mode, keep synthetic alerts fresh

internal/monitoring/monitor_host_agents_test.go

@@ -0,0 +1,112 @@
+package monitoring
+
+import (
+	"testing"
+	"time"
+
+	"github.com/rcourtman/pulse-go-rewrite/internal/alerts"
+	"github.com/rcourtman/pulse-go-rewrite/internal/models"
+)
+
+func TestEvaluateHostAgentsTriggersOfflineAlert(t *testing.T) {
+	t.Helper()
+
+	monitor := &Monitor{
+		state:        models.NewState(),
+		alertManager: alerts.NewManager(),
+	}
+	t.Cleanup(func() { monitor.alertManager.Stop() })
+
+	hostID := "host-offline"
+	monitor.state.UpsertHost(models.Host{
+		ID:              hostID,
+		Hostname:        "offline.local",
+		DisplayName:     "Offline Host",
+		Status:          "online",
+		IntervalSeconds: 30,
+		LastSeen:        time.Now().Add(-10 * time.Minute),
+	})
+
+	now := time.Now()
+	for i := 0; i < 3; i++ {
+		monitor.evaluateHostAgents(now.Add(time.Duration(i) * time.Second))
+	}
+
+	snapshot := monitor.state.GetSnapshot()
+	statusUpdated := false
+	for _, host := range snapshot.Hosts {
+		if host.ID == hostID {
+			statusUpdated = true
+			if got := host.Status; got != "offline" {
+				t.Fatalf("expected host status offline, got %q", got)
+			}
+		}
+	}
+	if !statusUpdated {
+		t.Fatalf("host %q not found in state snapshot", hostID)
+	}
+
+	connKey := hostConnectionPrefix + hostID
+	if healthy, ok := snapshot.ConnectionHealth[connKey]; !ok || healthy {
+		t.Fatalf("expected connection health false, got %v (exists=%v)", healthy, ok)
+	}
+
+	alerts := monitor.alertManager.GetActiveAlerts()
+	found := false
+	for _, alert := range alerts {
+		if alert.ID == "host-offline-"+hostID {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatalf("expected host offline alert to remain active")
+	}
+}
+
+func TestEvaluateHostAgentsClearsAlertWhenHostReturns(t *testing.T) {
+	t.Helper()
+
+	monitor := &Monitor{
+		state:        models.NewState(),
+		alertManager: alerts.NewManager(),
+	}
+	t.Cleanup(func() { monitor.alertManager.Stop() })
+
+	hostID := "host-recover"
+	monitor.state.UpsertHost(models.Host{
+		ID:              hostID,
+		Hostname:        "recover.local",
+		DisplayName:     "Recover Host",
+		Status:          "online",
+		IntervalSeconds: 30,
+		LastSeen:        time.Now().Add(-10 * time.Minute),
+	})
+
+	for i := 0; i < 3; i++ {
+		monitor.evaluateHostAgents(time.Now().Add(time.Duration(i) * time.Second))
+	}
+
+	monitor.state.UpsertHost(models.Host{
+		ID:              hostID,
+		Hostname:        "recover.local",
+		DisplayName:     "Recover Host",
+		Status:          "online",
+		IntervalSeconds: 30,
+		LastSeen:        time.Now(),
+	})
+
+	monitor.evaluateHostAgents(time.Now())
+
+	snapshot := monitor.state.GetSnapshot()
+	connKey := hostConnectionPrefix + hostID
+	if healthy, ok := snapshot.ConnectionHealth[connKey]; !ok || !healthy {
+		t.Fatalf("expected connection health true after recovery, got %v (exists=%v)", healthy, ok)
+	}
+
+	for _, alert := range monitor.alertManager.GetActiveAlerts() {
+		if alert.ID == "host-offline-"+hostID {
+			t.Fatalf("offline alert still active after recovery")
+		}
+	}
+}

internal/monitoring/task_queue.go

@@ -104,6 +104,39 @@ func (q *TaskQueue) Remove(instanceType InstanceType, instance string) {
 
 // WaitNext blocks until a task is due or context is cancelled.
 func (q *TaskQueue) WaitNext(ctx context.Context) (ScheduledTask, bool) {
+	var (
+		timer      *time.Timer
+		resetTimer = func(d time.Duration) <-chan time.Time {
+			if d <= 0 {
+				d = time.Millisecond
+			}
+			if timer == nil {
+				timer = time.NewTimer(d)
+				return timer.C
+			}
+			if !timer.Stop() {
+				select {
+				case <-timer.C:
+				default:
+				}
+			}
+			timer.Reset(d)
+			return timer.C
+		}
+		stopTimer = func() {
+			if timer == nil {
+				return
+			}
+			if !timer.Stop() {
+				select {
+				case <-timer.C:
+				default:
+				}
+			}
+		}
+	)
+	defer stopTimer()
+
 	for {
 		select {
 		case <-ctx.Done():
@@ -114,10 +147,11 @@ func (q *TaskQueue) WaitNext(ctx context.Context) (ScheduledTask, bool) {
 		q.mu.Lock()
 		if len(q.heap) == 0 {
 			q.mu.Unlock()
+			timerCh := resetTimer(100 * time.Millisecond)
 			select {
 			case <-ctx.Done():
 				return ScheduledTask{}, false
-			case <-time.After(100 * time.Millisecond):
+			case <-timerCh:
 				continue
 			}
 		}
@@ -136,12 +170,11 @@ func (q *TaskQueue) WaitNext(ctx context.Context) (ScheduledTask, bool) {
 		if delay > 250*time.Millisecond {
 			delay = 250 * time.Millisecond
 		}
-		timer := time.NewTimer(delay)
+		timerCh := resetTimer(delay)
 		select {
 		case <-ctx.Done():
-			timer.Stop()
 			return ScheduledTask{}, false
-		case <-timer.C:
+		case <-timerCh:
 		}
 	}
 }