CUB-200: fix event-loss race — register handlers before readLoop starts

Move registerEventHandlers() call before the readLoop goroutine starts
in connectAndRun(). This eliminates the startup window where live gateway
events were actively read and dropped as 'unhandled' because handler
registration happened only after initialSync completed.

The handlers only depend on c.agents and c.broker, which are wired in the
constructor — they do not require initialSync to have completed.

Also adds TestConnectAndRun_EventNotLostDuringSync regression test that
sends a live presence event during initial sync and asserts it is not lost.

All gateway tests pass with -race.

.env.example

@@ -32,7 +32,7 @@ GATEWAY_POLL_INTERVAL=5s
 # When using docker-compose, these are set in the services section
 # See docker-compose.yml for service-specific environment variables
 
-# ── Database Configuration ─────────────────────────────────────────────
+# ── Database Configuration ───────────────────────────────────────────────
 # Set in the db service environment section of docker-compose.yml
 # POSTGRES_USER=controlcenter
 # POSTGRES_PASSWORD=controlcenter

frontend/package.json

@@ -7,7 +7,9 @@
     "dev": "vite",
     "build": "tsc -b && vite build",
     "lint": "eslint .",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "dependencies": {
     "@tanstack/react-query": "^5.100.9",
@@ -20,6 +22,8 @@
   "devDependencies": {
     "@eslint/js": "^10.0.1",
     "@tailwindcss/vite": "^4.2.4",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
     "@types/node": "^24.12.2",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
@@ -29,10 +33,12 @@
     "eslint-plugin-react-hooks": "^7.1.1",
     "eslint-plugin-react-refresh": "^0.5.2",
     "globals": "^17.5.0",
+    "jsdom": "^29.1.1",
     "postcss": "^8.5.14",
     "tailwindcss": "^4.2.4",
     "typescript": "~6.0.2",
     "typescript-eslint": "^8.58.2",
-    "vite": "^8.0.10"
+    "vite": "^8.0.10",
+    "vitest": "^4.1.7"
   }
 }

frontend/src/components/Layout.tsx

@@ -1,6 +1,8 @@
 import { useState } from 'react'
 import { NavLink } from 'react-router-dom'
-import { Command, Activity, FolderKanban, Monitor, Settings, Menu, X } from 'lucide-react'
+import { Command, Activity, FolderKanban, Monitor, Settings, Menu, X, Wifi, WifiOff, Loader } from 'lucide-react'
+import { useSSEContext } from '../contexts/SSEContext'
+import type { SSEStatus } from '../hooks/useSSE'
 
 const navItems = [
   { to: '/', icon: Command, label: 'Hub' },
@@ -10,9 +12,29 @@ const navItems = [
   { to: '/settings', icon: Settings, label: 'Settings' },
 ]
 
+/** Small status pill shown in the sidebar footer and mobile header. */
+function SSEStatusBadge({ status, showLabel = false }: { status: SSEStatus; showLabel?: boolean }) {
+  const cfg = {
+    connected: { icon: Wifi, color: 'text-green-500', label: 'Live' },
+    connecting: { icon: Loader, color: 'text-yellow-500 animate-spin', label: 'Connecting' },
+    reconnecting: { icon: Loader, color: 'text-yellow-500 animate-spin', label: 'Reconnecting' },
+    error: { icon: WifiOff, color: 'text-red-500', label: 'Disconnected' },
+  }[status]
+
+  const Icon = cfg.icon
+
+  return (
+    <div className="flex items-center gap-1.5" title={cfg.label}>
+      <Icon size={14} className={cfg.color} />
+      {showLabel && <span className={`text-xs ${cfg.color}`}>{cfg.label}</span>}
+    </div>
+  )
+}
+
 export default function Layout({ children }: { children: React.ReactNode }) {
   const [expanded, setExpanded] = useState(false)
   const [mobileOpen, setMobileOpen] = useState(false)
+  const { sseStatus } = useSSEContext()
 
   return (
     <div className="flex min-h-screen bg-surface-darkest text-on-surface">
@@ -46,6 +68,15 @@ export default function Layout({ children }: { children: React.ReactNode }) {
             </NavLink>
           ))}
         </nav>
+        {/* SSE connection status — footer of sidebar */}
+        <div className="px-4 py-3 border-t border-surface-light flex items-center gap-2">
+          <SSEStatusBadge status={sseStatus} />
+          {expanded && (
+            <span className="text-xs text-on-surface-muted whitespace-nowrap">
+              {sseStatus === 'connected' ? 'Live updates on' : sseStatus}
+            </span>
+          )}
+        </div>
       </aside>
 
       {/* Mobile Header + Bottom Nav */}
@@ -54,6 +85,7 @@ export default function Layout({ children }: { children: React.ReactNode }) {
           <div className="flex items-center gap-2">
             <Command size={22} className="text-primary" />
             <span className="font-bold">Control Center</span>
+            <SSEStatusBadge status={sseStatus} />
           </div>
           <button onClick={() => setMobileOpen(!mobileOpen)} className="p-2">
             {mobileOpen ? <X size={22} /> : <Menu size={22} />}

frontend/src/contexts/SSEContext.tsx

@@ -0,0 +1,23 @@
+/**
+ * SSEContext — provides SSE connection status throughout the component tree.
+ * Mount <SSEProvider> once inside QueryClientProvider.
+ */
+import { createContext, useContext, type ReactNode } from 'react'
+import { useRealtimeSync } from '../hooks/useRealtimeSync'
+import type { SSEStatus } from '../hooks/useSSE'
+
+interface SSEContextValue {
+  sseStatus: SSEStatus
+}
+
+const SSEContext = createContext<SSEContextValue>({ sseStatus: 'connecting' })
+
+export function SSEProvider({ children }: { children: ReactNode }) {
+  const { sseStatus } = useRealtimeSync()
+  return <SSEContext.Provider value={{ sseStatus }}>{children}</SSEContext.Provider>
+}
+
+/** Access the SSE connection status from any component. */
+export function useSSEContext(): SSEContextValue {
+  return useContext(SSEContext)
+}

frontend/src/hooks/useRealtimeSync.test.tsx

@@ -0,0 +1,129 @@
+/**
+ * Tests for useRealtimeSync — event → query invalidation mapping.
+ *
+ * Uses .tsx extension so Vite/OXC can parse JSX in the wrapper component.
+ */
+import { renderHook } from '@testing-library/react'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import * as useSSEModule from './useSSE'
+import { useRealtimeSync } from './useRealtimeSync'
+import React from 'react'
+import type { SSEMessage } from '../services/sse'
+
+describe('useRealtimeSync', () => {
+  let queryClient: QueryClient
+  let mockSSEOnMessage: ((msg: { type: string; data: unknown }) => void) | null = null
+
+  beforeEach(() => {
+    queryClient = new QueryClient({
+      defaultOptions: { queries: { retry: false } },
+    })
+    mockSSEOnMessage = null
+
+    // Spy on useSSE to capture the onMessage callback
+    vi.spyOn(useSSEModule, 'useSSE').mockImplementation((opts) => {
+      mockSSEOnMessage = opts?.onMessage ?? null
+      return { status: 'connected' }
+    })
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  function render() {
+    return renderHook(() => useRealtimeSync(), {
+      wrapper: ({ children }: { children: React.ReactNode }) => (
+        React.createElement(QueryClientProvider, { client: queryClient }, children)
+      ),
+    })
+  }
+
+  it('invalidates ["agents"] on agent.status event', async () => {
+    const invalidateSpy = vi.spyOn(queryClient, 'invalidateQueries')
+    render()
+
+    const msg: SSEMessage = {
+      type: 'agent.status',
+      data: { agentId: 'a1', status: 'active' },
+    }
+    mockSSEOnMessage!(msg)
+
+    expect(invalidateSpy).toHaveBeenCalledWith({ queryKey: ['agents'] })
+    expect(invalidateSpy).toHaveBeenCalledTimes(1)
+  })
+
+  it('invalidates ["tasks"] and ["agents"] on agent.task event', async () => {
+    const invalidateSpy = vi.spyOn(queryClient, 'invalidateQueries')
+    render()
+
+    const msg: SSEMessage = {
+      type: 'agent.task',
+      data: { agentId: 'a1', taskId: 't1', title: 'Test', action: 'assigned' },
+    }
+    mockSSEOnMessage!(msg)
+
+    expect(invalidateSpy).toHaveBeenCalledWith({ queryKey: ['tasks'] })
+    expect(invalidateSpy).toHaveBeenCalledWith({ queryKey: ['agents'] })
+    expect(invalidateSpy).toHaveBeenCalledTimes(2)
+  })
+
+  it('invalidates ["tasks"] and ["agents"] on agent.progress event', async () => {
+    const invalidateSpy = vi.spyOn(queryClient, 'invalidateQueries')
+    render()
+
+    const msg: SSEMessage = {
+      type: 'agent.progress',
+      data: { agentId: 'a1', taskId: 't1', progress: 50, message: 'working' },
+    }
+    mockSSEOnMessage!(msg)
+
+    expect(invalidateSpy).toHaveBeenCalledWith({ queryKey: ['tasks'] })
+    expect(invalidateSpy).toHaveBeenCalledWith({ queryKey: ['agents'] })
+    expect(invalidateSpy).toHaveBeenCalledTimes(2)
+  })
+
+  it('invalidates ["agents"], ["sessions"], ["tasks"] on fleet.update event', async () => {
+    const invalidateSpy = vi.spyOn(queryClient, 'invalidateQueries')
+    render()
+
+    const msg: SSEMessage = {
+      type: 'fleet.update',
+      data: { timestamp: '2026-05-20T12:00:00Z', agentCount: 5 },
+    }
+    mockSSEOnMessage!(msg)
+
+    expect(invalidateSpy).toHaveBeenCalledWith({ queryKey: ['agents'] })
+    expect(invalidateSpy).toHaveBeenCalledWith({ queryKey: ['sessions'] })
+    expect(invalidateSpy).toHaveBeenCalledWith({ queryKey: ['tasks'] })
+    expect(invalidateSpy).toHaveBeenCalledTimes(3)
+  })
+
+  it('does nothing on connected event', async () => {
+    const invalidateSpy = vi.spyOn(queryClient, 'invalidateQueries')
+    render()
+
+    const msg: SSEMessage = {
+      type: 'connected',
+      data: { clientCount: 1 },
+    }
+    mockSSEOnMessage!(msg)
+
+    expect(invalidateSpy).not.toHaveBeenCalled()
+  })
+
+  it('does nothing on unknown event types', async () => {
+    const invalidateSpy = vi.spyOn(queryClient, 'invalidateQueries')
+    render()
+
+    mockSSEOnMessage!({ type: 'unknown.event', data: {} })
+
+    expect(invalidateSpy).not.toHaveBeenCalled()
+  })
+
+  it('returns sseStatus from useSSE', () => {
+    const { result } = render()
+    expect(result.current.sseStatus).toBe('connected')
+  })
+})

frontend/src/hooks/useRealtimeSync.ts

@@ -0,0 +1,64 @@
+/**
+ * useRealtimeSync — mounts the SSE connection once at the app level and
+ * wires incoming events to React Query cache invalidation.
+ *
+ * Event → query key mapping:
+ *   agent.status   → ['agents']
+ *   agent.task     → ['tasks'], ['agents']
+ *   agent.progress → ['tasks'], ['agents']
+ *   fleet.update   → ['agents'], ['sessions'], ['tasks']
+ */
+import { useQueryClient } from '@tanstack/react-query'
+import { useCallback } from 'react'
+import { useSSE, type SSEStatus } from './useSSE'
+import type { SSEMessage } from '../services/sse'
+
+export function useRealtimeSync(): { sseStatus: SSEStatus } {
+  const queryClient = useQueryClient()
+
+  const handleMessage = useCallback(
+    (raw: { type: string; data: unknown }) => {
+      // Cast to discriminated union — the backend contract guarantees these shapes
+      const msg = raw as SSEMessage
+
+      switch (msg.type) {
+        case 'agent.status':
+          // msg.data: AgentStatusEvent { agentId, status, reason? }
+          void msg.data.agentId // retained for type-narrowing — ensures payload matches contract
+          queryClient.invalidateQueries({ queryKey: ['agents'] })
+          break
+
+        case 'agent.task':
+          // msg.data: AgentTaskEvent { agentId, taskId, title, action }
+          void msg.data.agentId
+          queryClient.invalidateQueries({ queryKey: ['tasks'] })
+          queryClient.invalidateQueries({ queryKey: ['agents'] })
+          break
+
+        case 'agent.progress':
+          // msg.data: AgentProgressEvent { agentId, taskId, progress, message? }
+          void msg.data.agentId
+          queryClient.invalidateQueries({ queryKey: ['tasks'] })
+          queryClient.invalidateQueries({ queryKey: ['agents'] })
+          break
+
+        case 'fleet.update':
+          // msg.data: FleetUpdateEvent { timestamp, agentCount }
+          void msg.data.agentCount
+          queryClient.invalidateQueries({ queryKey: ['agents'] })
+          queryClient.invalidateQueries({ queryKey: ['sessions'] })
+          queryClient.invalidateQueries({ queryKey: ['tasks'] })
+          break
+
+        default:
+          // 'connected' and unknown events — no action needed
+          break
+      }
+    },
+    [queryClient],
+  )
+
+  const { status: sseStatus } = useSSE({ onMessage: handleMessage })
+
+  return { sseStatus }
+}

frontend/src/hooks/useSSE.test.ts

@@ -0,0 +1,267 @@
+/**
+ * Tests for useSSE — SSE connection lifecycle, back-off, event parsing, and cleanup.
+ *
+ * jsdom does not include EventSource, so we mock it completely.
+ */
+import { renderHook, act, waitFor } from '@testing-library/react'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { useSSE } from './useSSE'
+
+// ---------------------------------------------------------------------------
+// Mock EventSource — defined as a plain class so `new EventSource()` works
+// ---------------------------------------------------------------------------
+class MockEventSource {
+  url: string
+  onopen: (() => void) | null = null
+  onerror: ((evt: Event) => void) | null = null
+  onmessage: ((evt: MessageEvent) => void) | null = null
+  private listeners: Map<string, Array<(evt: Event) => void>> = new Map()
+  readyState: number = 0
+
+  constructor(url: string) {
+    this.url = url
+  }
+
+  addEventListener(type: string, handler: (evt: Event) => void) {
+    if (!this.listeners.has(type)) this.listeners.set(type, [])
+    this.listeners.get(type)!.push(handler)
+  }
+
+  removeEventListener() { /* no-op for tests */ }
+
+  close() {
+    this.readyState = 2
+    this.onopen = null
+    this.onerror = null
+    this.onmessage = null
+    this.listeners.clear()
+  }
+
+  // Test helpers
+  _simulateOpen() { this.onopen?.() }
+  _simulateError() { this.onerror?.(new Event('error')) }
+  _simulateNamedEvent(type: string, data: string) {
+    const handlers = this.listeners.get(type)
+    if (handlers) {
+      const evt = new MessageEvent(type, { data }) as Event
+      handlers.forEach((h) => h(evt))
+    }
+  }
+  _simulateMessage(data: string) {
+    this.onmessage?.(new MessageEvent('message', { data }) as MessageEvent)
+  }
+
+  static readonly CONNECTING = 0
+  static readonly OPEN = 1
+  static readonly CLOSED = 2
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+let esInstances: MockEventSource[]
+
+describe('useSSE', () => {
+  beforeEach(() => {
+    esInstances = []
+    // Replace global EventSource with our mock class
+    Object.defineProperty(globalThis, 'EventSource', {
+      // The mock must use a class for `new EventSource()` to work
+      value: class extends MockEventSource {
+        constructor(url: string) {
+          super(url)
+          esInstances.push(this)
+        }
+      },
+      writable: true,
+      configurable: true,
+    })
+    vi.useFakeTimers({ shouldAdvanceTime: true })
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+    vi.useRealTimers()
+  })
+
+  // ── Initial connection ──────────────────────────────────────────────────
+  it('starts in "connecting" state and creates an EventSource', () => {
+    const { result } = renderHook(() => useSSE({ url: '/api/events' }))
+
+    expect(result.current.status).toBe('connecting')
+    expect(esInstances.length).toBeGreaterThanOrEqual(1)
+    expect(esInstances[0].url).toBe('/api/events')
+  })
+
+  it('transitions to "connected" on open', async () => {
+    const onOpen = vi.fn()
+    const { result } = renderHook(() => useSSE({ url: '/api/events', onOpen }))
+
+    act(() => { esInstances[0]._simulateOpen() })
+
+    await waitFor(() => {
+      expect(result.current.status).toBe('connected')
+    })
+    expect(onOpen).toHaveBeenCalledTimes(1)
+  })
+
+  // ── Reconnection with exponential back-off ──────────────────────────────
+  it('retries after error with exponential back-off', async () => {
+    const { result } = renderHook(() =>
+      useSSE({ url: '/api/events', reconnectBaseMs: 1000, reconnectMaxMs: 30000 }),
+    )
+
+    // First error → reconnecting, retry at 1s
+    act(() => { esInstances[0]._simulateError() })
+    await waitFor(() => { expect(result.current.status).toBe('reconnecting') })
+    expect(esInstances).toHaveLength(1)
+
+    // Advance 1000ms → second EventSource created
+    act(() => { vi.advanceTimersByTime(1000) })
+    expect(esInstances).toHaveLength(2)
+
+    // Second error → reconnecting, retry at 2s
+    act(() => { esInstances[1]._simulateError() })
+    await waitFor(() => { expect(result.current.status).toBe('reconnecting') })
+    act(() => { vi.advanceTimersByTime(2000) })
+    expect(esInstances).toHaveLength(3)
+
+    // Third error → reconnecting, retry at 4s
+    act(() => { esInstances[2]._simulateError() })
+    act(() => { vi.advanceTimersByTime(4000) })
+    expect(esInstances).toHaveLength(4)
+  })
+
+  it('caps reconnect delay at reconnectMaxMs', async () => {
+    renderHook(() =>
+      useSSE({ url: '/api/events', reconnectBaseMs: 1000, reconnectMaxMs: 10000 }),
+    )
+
+    // Force 5 errors to push the exponent past the cap
+    for (let i = 0; i < 5; i++) {
+      act(() => { esInstances[i]._simulateError() })
+      const expectedDelay = Math.min(1000 * 2 ** i, 10000)
+      act(() => { vi.advanceTimersByTime(expectedDelay) })
+    }
+
+    // 6 ES instances created (initial + 5 retries)
+    expect(esInstances).toHaveLength(6)
+  })
+
+  // ── Circuit-breaker (max retries) ───────────────────────────────────────
+  it('transitions to "error" after reconnectLimit is exceeded', async () => {
+    const { result } = renderHook(() =>
+      useSSE({ url: '/api/events', reconnectBaseMs: 100, reconnectLimit: 2 }),
+    )
+
+    // First error → reconnecting
+    act(() => { esInstances[0]._simulateError() })
+    await waitFor(() => { expect(result.current.status).toBe('reconnecting') })
+
+    // Advance → retry
+    act(() => { vi.advanceTimersByTime(100) })
+
+    // Second error → reconnecting (attempt 2, still ≤ limit)
+    act(() => { esInstances[1]._simulateError() })
+    await waitFor(() => { expect(result.current.status).toBe('reconnecting') })
+    act(() => { vi.advanceTimersByTime(200) })
+
+    // Third error → limit exceeded (3 > 2) → error
+    act(() => { esInstances[2]._simulateError() })
+    await waitFor(() => { expect(result.current.status).toBe('error') })
+  })
+
+  it('resets reconnect counter on successful connection', async () => {
+    const { result } = renderHook(() =>
+      useSSE({ url: '/api/events', reconnectBaseMs: 100, reconnectLimit: 3 }),
+    )
+
+    // Two errors then a successful connect
+    act(() => { esInstances[0]._simulateError() })
+    act(() => { vi.advanceTimersByTime(100) })
+
+    act(() => { esInstances[1]._simulateOpen() })
+    await waitFor(() => { expect(result.current.status).toBe('connected') })
+
+    // Now error again — counter should be reset, so we get fresh attempts
+    act(() => { esInstances[1]._simulateError() })
+    await waitFor(() => { expect(result.current.status).toBe('reconnecting') })
+    expect(result.current.status).toBe('reconnecting')
+  })
+
+  // ── Cleanup on unmount ───────────────────────────────────────────────────
+  it('closes EventSource on unmount', () => {
+    const closeSpy = vi.spyOn(MockEventSource.prototype, 'close')
+    const { unmount } = renderHook(() => useSSE({ url: '/api/events' }))
+
+    unmount()
+    expect(closeSpy).toHaveBeenCalled()
+  })
+
+  it('does not update state after unmount', async () => {
+    const { result, unmount } = renderHook(() => useSSE({ url: '/api/events' }))
+
+    unmount()
+
+    // These should be no-ops after unmount (mountedRef guards)
+    act(() => { esInstances[0]._simulateOpen() })
+    act(() => { esInstances[0]._simulateError() })
+
+    // State should not have changed
+    expect(result.current.status).toBe('connecting')
+  })
+
+  // ── Event parsing ───────────────────────────────────────────────────────
+  it('parses valid JSON data into objects', async () => {
+    const onMessage = vi.fn()
+    renderHook(() => useSSE({ url: '/api/events', onMessage }))
+
+    act(() => {
+      esInstances[0]._simulateNamedEvent('agent.status', JSON.stringify({ agentId: 'a1', status: 'active' }))
+    })
+
+    expect(onMessage).toHaveBeenCalledWith({
+      type: 'agent.status',
+      data: { agentId: 'a1', status: 'active' },
+    })
+  })
+
+  it('passes invalid JSON through as raw string', async () => {
+    const onMessage = vi.fn()
+    renderHook(() => useSSE({ url: '/api/events', onMessage }))
+
+    act(() => {
+      esInstances[0]._simulateNamedEvent('agent.status', 'not valid json {{{')
+    })
+
+    expect(onMessage).toHaveBeenCalledWith({
+      type: 'agent.status',
+      data: 'not valid json {{{',
+    })
+  })
+
+  // ── enabled=false skips connection ──────────────────────────────────────
+  it('does not create EventSource when enabled=false', () => {
+    const { result } = renderHook(() => useSSE({ url: '/api/events', enabled: false }))
+
+    expect(esInstances).toHaveLength(0)
+    expect(result.current.status).toBe('connecting')
+  })
+
+  // ── onError callback ────────────────────────────────────────────────────
+  it('calls onError on connection failure', async () => {
+    const onError = vi.fn()
+    renderHook(() =>
+      useSSE({ url: '/api/events', onError, reconnectBaseMs: 100 }),
+    )
+
+    act(() => { esInstances[0]._simulateError() })
+    expect(onError).toHaveBeenCalledTimes(1)
+  })
+
+  // ── Default URL ─────────────────────────────────────────────────────────
+  it('uses /api/events as default URL', () => {
+    renderHook(() => useSSE())
+    expect(esInstances[0].url).toBe('/api/events')
+  })
+})

frontend/src/hooks/useSSE.ts

@@ -0,0 +1,180 @@
+import { useEffect, useRef, useCallback, useState } from 'react'
+
+/** SSE connection state reported to consumers. */
+export type SSEStatus = 'connecting' | 'connected' | 'reconnecting' | 'error'
+
+/** Typed SSE event received from the backend. */
+export interface SSEMessage {
+  /** event: field from the SSE frame */
+  type: string
+  /** parsed JSON from the data: field */
+  data: unknown
+}
+
+export interface UseSSEOptions {
+  /** Endpoint URL — defaults to /api/events */
+  url?: string
+  /** Called for every SSE message (all event types) */
+  onMessage?: (msg: SSEMessage) => void
+  /** Called when connection opens or reconnects */
+  onOpen?: () => void
+  /** Called on every connection error (both transient and terminal) */
+  onError?: (err: Event) => void
+  /** Base delay in ms before the first reconnect attempt (default 1 000) */
+  reconnectBaseMs?: number
+  /** Maximum reconnect delay in ms (default 30 000) */
+  reconnectMaxMs?: number
+  /**
+   * Maximum number of consecutive reconnect attempts before giving up.
+   * When the limit is reached, status transitions to 'error'.
+   * Default undefined (unlimited).
+   */
+  reconnectLimit?: number
+  /** Set false to disable auto-connect (useful in tests) */
+  enabled?: boolean
+}
+
+const SSE_EVENTS = ['agent.status', 'agent.task', 'agent.progress', 'fleet.update', 'connected'] as const
+
+/**
+ * useSSE — mounts a persistent SSE connection to the Control Center backend.
+ *
+ * Handles:
+ *  - Initial connection on mount
+ *  - Exponential back-off reconnection on drop (1s → 2s → 4s … capped at reconnectMaxMs)
+ *  - Circuit-breaker: after reconnectLimit consecutive failures, transitions to 'error'
+ *  - Cleanup on unmount
+ *  - All five event types: agent.status, agent.task, agent.progress, fleet.update, connected
+ *
+ * The 'connected' SSE event is an application-level handshake sent by the backend
+ * after the transport opens. This is distinct from onOpen, which fires at the
+ * transport level when the EventSource HTTP connection is established.
+ */
+export function useSSE({
+  url = '/api/events',
+  onMessage,
+  onOpen,
+  onError,
+  reconnectBaseMs = 1_000,
+  reconnectMaxMs = 30_000,
+  reconnectLimit,
+  enabled = true,
+}: UseSSEOptions = {}): { status: SSEStatus } {
+  const [status, setStatus] = useState<SSEStatus>('connecting')
+
+  // Stable refs so the effect doesn't need to re-run when callbacks change
+  const onMessageRef = useRef(onMessage)
+  const onOpenRef = useRef(onOpen)
+  const onErrorRef = useRef(onError)
+  onMessageRef.current = onMessage
+  onOpenRef.current = onOpen
+  onErrorRef.current = onError
+
+  const reconnectAttemptRef = useRef(0)
+  const reconnectTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const esRef = useRef<EventSource | null>(null)
+  const mountedRef = useRef(true)
+
+  const clearReconnectTimer = useCallback(() => {
+    if (reconnectTimerRef.current !== null) {
+      clearTimeout(reconnectTimerRef.current)
+      reconnectTimerRef.current = null
+    }
+  }, [])
+
+  const connect = useCallback(() => {
+    if (!mountedRef.current || !enabled) return
+
+    // Clean up any existing connection
+    if (esRef.current) {
+      esRef.current.close()
+      esRef.current = null
+    }
+
+    setStatus(reconnectAttemptRef.current === 0 ? 'connecting' : 'reconnecting')
+
+    const es = new EventSource(url)
+    esRef.current = es
+
+    es.onopen = () => {
+      if (!mountedRef.current) return
+      reconnectAttemptRef.current = 0
+      setStatus('connected')
+      onOpenRef.current?.()
+    }
+
+    es.onerror = (evt) => {
+      if (!mountedRef.current) return
+
+      // EventSource auto-retries but we manage our own to get back-off control
+      es.close()
+      esRef.current = null
+
+      onErrorRef.current?.(evt)
+
+      reconnectAttemptRef.current += 1
+
+      // Circuit-breaker: give up after reconnectLimit consecutive failures
+      if (reconnectLimit !== undefined && reconnectAttemptRef.current > reconnectLimit) {
+        setStatus('error')
+        return
+      }
+
+      // Exponential back-off: 1s, 2s, 4s … capped at reconnectMaxMs
+      // Note: attempt is 1-based here (already incremented), so we use attempt-1 for the exponent
+      const delay = Math.min(
+        reconnectBaseMs * 2 ** (reconnectAttemptRef.current - 1),
+        reconnectMaxMs,
+      )
+      setStatus('reconnecting')
+
+      clearReconnectTimer()
+      reconnectTimerRef.current = setTimeout(() => {
+        if (mountedRef.current) connect()
+      }, delay)
+    }
+
+    // Register listeners for all known event types
+    for (const eventType of SSE_EVENTS) {
+      es.addEventListener(eventType, (evt: MessageEvent) => {
+        if (!mountedRef.current) return
+        let data: unknown = evt.data
+        try {
+          data = JSON.parse(evt.data as string)
+        } catch {
+          // leave as raw string
+        }
+        onMessageRef.current?.({ type: eventType, data })
+      })
+    }
+
+    // Catch-all for unnamed events (type == 'message').
+    // Won't fire for the named events registered via addEventListener above.
+    es.onmessage = (evt: MessageEvent) => {
+      if (!mountedRef.current) return
+      let data: unknown = evt.data
+      try {
+        data = JSON.parse(evt.data as string)
+      } catch {
+        // leave as raw string
+      }
+      onMessageRef.current?.({ type: 'message', data })
+    }
+  }, [url, enabled, reconnectBaseMs, reconnectMaxMs, reconnectLimit, clearReconnectTimer])
+
+  useEffect(() => {
+    mountedRef.current = true
+    if (enabled) connect()
+
+    return () => {
+      mountedRef.current = false
+      clearReconnectTimer()
+      if (esRef.current) {
+        esRef.current.close()
+        esRef.current = null
+      }
+    }
+  }, [connect, enabled, clearReconnectTimer])
+
+  return { status }
+}

frontend/src/main.tsx

@@ -4,13 +4,16 @@ import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
 import { BrowserRouter } from 'react-router-dom'
 import ErrorBoundary from './components/ErrorBoundary'
 import { ThemeProvider } from './hooks/useTheme'
+import { SSEProvider } from './contexts/SSEContext'
 import './index.css'
 import App from './App'
 
 const queryClient = new QueryClient({
   defaultOptions: {
     queries: {
-      staleTime: 30_000,
+      // No polling — real-time updates come through SSE.
+      // staleTime is kept high; data is pushed, not pulled.
+      staleTime: 60_000,
       refetchOnWindowFocus: false,
       retry: 1,
     },
@@ -22,9 +25,13 @@ createRoot(document.getElementById('root')!).render(
     <ErrorBoundary>
       <ThemeProvider>
         <QueryClientProvider client={queryClient}>
+          {/* SSEProvider must live inside QueryClientProvider so it can call
+              useQueryClient() to invalidate caches on incoming events. */}
+          <SSEProvider>
             <BrowserRouter>
               <App />
             </BrowserRouter>
+          </SSEProvider>
         </QueryClientProvider>
       </ThemeProvider>
     </ErrorBoundary>

frontend/src/pages/SettingsPage.tsx

@@ -1,18 +1,36 @@
 import { useTheme } from '../hooks/useTheme'
 import { useLocalStorage } from '../hooks/useLocalStorage'
-import { Sun, Moon, Monitor, Zap, Clock } from 'lucide-react'
+import { useSSEContext } from '../contexts/SSEContext'
+import { Sun, Moon, Monitor, Zap, Radio } from 'lucide-react'
 
-const REFRESH_PRESETS = [
+const SSE_STATUS_COPY: Record<string, { label: string; description: string; color: string }> = {
-  { label: '5s', value: 5_000 },
+  connected: {
-  { label: '10s', value: 10_000 },
+    label: 'Connected',
-  { label: '30s', value: 30_000 },
+    description: 'Real-time updates are active. Agent status, tasks, and progress stream live.',
-  { label: '60s', value: 60_000 },
+    color: 'text-green-500',
-]
+  },
+  connecting: {
+    label: 'Connecting…',
+    description: 'Establishing SSE connection to the backend.',
+    color: 'text-yellow-500',
+  },
+  reconnecting: {
+    label: 'Reconnecting…',
+    description: 'Connection lost. Retrying with exponential back-off.',
+    color: 'text-yellow-500',
+  },
+  error: {
+    label: 'Disconnected',
+    description: 'Could not connect to the SSE endpoint. Check that the backend is reachable.',
+    color: 'text-red-500',
+  },
+}
 
 export default function SettingsPage() {
   const { isDark, toggleTheme } = useTheme()
   const [gatewayUrl, setGatewayUrl] = useLocalStorage('cc-gateway-url', '')
-  const [refreshInterval, setRefreshInterval] = useLocalStorage('cc-refresh-interval', 30_000)
+  const { sseStatus } = useSSEContext()
+  const sseInfo = SSE_STATUS_COPY[sseStatus] ?? SSE_STATUS_COPY.error
 
   return (
     <div className="space-y-8 max-w-2xl">
@@ -80,45 +98,31 @@ export default function SettingsPage() {
         </div>
       </section>
 
-      {/* Refresh */}
+      {/* Real-time connection status */}
       <section className="space-y-4">
         <h2 className="text-lg font-semibold flex items-center gap-2">
-          <Clock size={20} className="text-primary" />
+          <Radio size={20} className="text-primary" />
-          Auto Refresh
+          Real-time Updates
         </h2>
 
         <div className="p-5 rounded-xl border border-surface-light bg-surface-dark space-y-3">
-          <p className="text-sm text-on-surface-variant">Data refresh interval for agent status and logs</p>
+          <div className="flex items-center justify-between">
-
+            <div>
-          <div className="flex flex-col gap-2">
+              <p className="font-medium">SSE Connection</p>
-            <input
+              <p className="text-sm text-on-surface-variant mt-0.5">{sseInfo.description}</p>
-              type="range"
-              min="0"
-              max="3"
-              step="1"
-              value={REFRESH_PRESETS.findIndex((p) => p.value === refreshInterval)}
-              onChange={(e) => {
-                const idx = parseInt(e.target.value)
-                setRefreshInterval(REFRESH_PRESETS[idx].value)
-              }}
-              className="w-full accent-primary"
-            />
-            <div className="flex justify-between text-xs text-on-surface-muted">
-              {REFRESH_PRESETS.map((p) => (
-                <button
-                  key={p.label}
-                  onClick={() => setRefreshInterval(p.value)}
-                  className={`px-3 py-1 rounded-lg transition-colors ${
-                    refreshInterval === p.value
-                      ? 'bg-primary/10 text-primary'
-                      : 'hover:bg-surface-light'
-                  }`}
-                >
-                  {p.label}
-                </button>
-              ))}
             </div>
+            <span className={`text-sm font-semibold whitespace-nowrap ${sseInfo.color}`}>
+              {sseInfo.label}
+            </span>
           </div>
+          <p className="text-xs text-on-surface-muted">
+            Endpoint: <code className="bg-surface-light px-1.5 py-0.5 rounded text-on-surface-variant">/api/events</code>
+            &nbsp;·&nbsp;Events: agent.status, agent.task, agent.progress, fleet.update
+          </p>
+          <p className="text-xs text-on-surface-muted">
+            Polling is disabled. All status updates are pushed from the server over a persistent SSE connection.
+            The client reconnects automatically with exponential back-off on drop.
+          </p>
         </div>
       </section>
     </div>

frontend/src/services/sse.ts

@@ -0,0 +1,72 @@
+/**
+ * SSE event payload types matching the Go backend (internal/handler/sse.go).
+ *
+ * Event format on the wire:
+ *   event: <eventType>
+ *   data: <json>
+ *
+ * The types below define the backend contract. The SSEPayloadMap maps
+ * each event type string to its expected payload shape. SSEMessage is a
+ * discriminated union on `type` — when you switch on msg.type, TypeScript
+ * narrows msg.data to the correct payload interface automatically.
+ */
+
+import type { AgentStatus } from '../types'
+
+/** agent.status — agent came online, went offline, changed state */
+export interface AgentStatusEvent {
+  agentId: string
+  status: AgentStatus
+  /** Optional human-readable reason (e.g. error message) */
+  reason?: string
+}
+
+/** agent.task — a task was assigned to or completed by an agent */
+export interface AgentTaskEvent {
+  agentId: string
+  taskId: string
+  title: string
+  action: 'assigned' | 'completed' | 'failed'
+}
+
+/** agent.progress — incremental progress update for a running task */
+export interface AgentProgressEvent {
+  agentId: string
+  taskId: string
+  progress: number
+  /** Optional description of what is currently happening */
+  message?: string
+}
+
+/**
+ * fleet.update — bulk refresh of all agents (e.g. after a deployment).
+ * The backend may send partial or complete agent state.
+ */
+export interface FleetUpdateEvent {
+  /** ISO timestamp of when the snapshot was taken */
+  timestamp: string
+  /** Number of agents in the fleet */
+  agentCount: number
+}
+
+/** Union of all SSE data payloads keyed by event type. */
+export type SSEPayloadMap = {
+  'agent.status': AgentStatusEvent
+  'agent.task': AgentTaskEvent
+  'agent.progress': AgentProgressEvent
+  'fleet.update': FleetUpdateEvent
+  connected: { clientCount: number }
+  message: unknown
+}
+
+/**
+ * Discriminated SSE message — the `type` field narrows `data` via SSEPayloadMap.
+ *
+ * Usage:
+ *   if (msg.type === 'agent.status') {
+ *     msg.data.agentId  // ✅ TypeScript knows this is AgentStatusEvent
+ *   }
+ */
+export type SSEMessage = {
+  [K in keyof SSEPayloadMap]: { type: K; data: SSEPayloadMap[K] }
+}[keyof SSEPayloadMap]

frontend/src/test-setup.ts

@@ -0,0 +1 @@
+import '@testing-library/jest-dom'

frontend/src/types/index.ts

@@ -1,4 +1,4 @@
-export type AgentStatus = 'active' | 'idle' | 'thinking' | 'error'
+export type AgentStatus = 'active' | 'idle' | 'thinking' | 'error' | 'offline'
 
 export interface Agent {
   id: string

frontend/tsconfig.app.json

@@ -4,7 +4,7 @@
     "target": "es2023",
     "lib": ["ES2023", "DOM"],
     "module": "esnext",
-    "types": ["vite/client"],
+    "types": ["vite/client", "vitest/globals"],
     "skipLibCheck": true,
 
     /* Bundler mode */

frontend/tsconfig.node.json

@@ -20,5 +20,5 @@
     "erasableSyntaxOnly": true,
     "noFallthroughCasesInSwitch": true
   },
-  "include": ["vite.config.ts"]
+  "include": ["vite.config.ts", "vitest.config.ts"]
 }

frontend/vitest.config.ts

@@ -0,0 +1,11 @@
+import { defineConfig } from 'vitest/config'
+import react from '@vitejs/plugin-react'
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    environment: 'jsdom',
+    globals: true,
+    setupFiles: ['./src/test-setup.ts'],
+  },
+})

go-backend/cmd/server/main.go

@@ -112,7 +112,7 @@ func main() {
 	<-quit
 	slog.Info("shutting down server...")
 
-	cancel() // stop gateway polling
+	cancel() // stop gateway clients
 
 	shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 15*time.Second)
 	defer shutdownCancel()

go-backend/internal/gateway/client.go

@@ -1,6 +1,10 @@
 // Package gateway provides an OpenClaw gateway integration client that
 // polls agent states, persists them via the repository layer, and broadcasts
 // changes through the SSE broker for real-time frontend updates.
+//
+// When a WSClient is wired via SetWSClient, the REST poller becomes a
+// fallback: it waits for the WS client to signal readiness, and only starts
+// polling if WS fails to connect within 30 seconds.
 package gateway
 
 import (
@@ -140,7 +144,6 @@ func (c *Client) poll(ctx context.Context) {
 	}
 
 	for _, ga := range agents {
-		// Check if agent already exists; if so, update; otherwise create.
 		existing, err := c.agents.Get(ctx, ga.ID)
 		if err != nil {
 			// Not found — create it

go-backend/internal/gateway/events_test.go

@@ -0,0 +1,516 @@
+package gateway
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"sync"
+	"testing"
+
+	"code.cubecraftcreations.com/CubeCraft-Creations/Control-Center/go-backend/internal/handler"
+	"code.cubecraftcreations.com/CubeCraft-Creations/Control-Center/go-backend/internal/models"
+)
+
+// ── Mock AgentRepo ────────────────────────────────────────────────────────
+
+type mockAgentRepo struct {
+	mu          sync.Mutex
+	agents      map[string]models.AgentCardData
+	updateCalls []updateCall
+}
+
+type updateCall struct {
+	id  string
+	req models.UpdateAgentRequest
+}
+
+func (m *mockAgentRepo) Get(_ context.Context, id string) (models.AgentCardData, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	a, ok := m.agents[id]
+	if !ok {
+		return models.AgentCardData{}, errNotFound
+	}
+	return a, nil
+}
+
+func (m *mockAgentRepo) Update(_ context.Context, id string, req models.UpdateAgentRequest) (models.AgentCardData, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	a, ok := m.agents[id]
+	if !ok {
+		return models.AgentCardData{}, errNotFound
+	}
+
+	if req.Status != nil {
+		a.Status = *req.Status
+	}
+	if req.DisplayName != nil {
+		a.DisplayName = *req.DisplayName
+	}
+	if req.Role != nil {
+		a.Role = *req.Role
+	}
+	if req.Channel != nil {
+		a.Channel = *req.Channel
+	}
+	if req.CurrentTask != nil {
+		a.CurrentTask = req.CurrentTask
+	}
+	if req.TaskProgress != nil {
+		a.TaskProgress = req.TaskProgress
+	}
+	if req.TaskElapsed != nil {
+		a.TaskElapsed = req.TaskElapsed
+	}
+	if req.ErrorMessage != nil {
+		a.ErrorMessage = req.ErrorMessage
+	}
+	if req.LastActivityAt != nil {
+		a.LastActivity = *req.LastActivityAt
+	}
+
+	m.agents[id] = a
+	m.updateCalls = append(m.updateCalls, updateCall{id, req})
+	return a, nil
+}
+
+func (m *mockAgentRepo) Create(_ context.Context, a models.AgentCardData) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.agents[a.ID] = a
+	return nil
+}
+
+func (m *mockAgentRepo) List(_ context.Context, statusFilter models.AgentStatus) ([]models.AgentCardData, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	var result []models.AgentCardData
+	for _, a := range m.agents {
+		if statusFilter == "" || a.Status == statusFilter {
+			result = append(result, a)
+		}
+	}
+	return result, nil
+}
+
+func (m *mockAgentRepo) Delete(_ context.Context, id string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	delete(m.agents, id)
+	return nil
+}
+
+func (m *mockAgentRepo) Count(_ context.Context) (int, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return len(m.agents), nil
+}
+
+// errNotFound is returned by the mock repo when an agent is not found.
+var errNotFound = fmt.Errorf("not found")
+
+// ── Broadcast capture helper ───────────────────────────────────────────────
+
+// broadcastCapture wraps a real Broker and captures all broadcasts
+// via a subscribed channel. Use captured() to retrieve events that have
+// been received so far. Call close() to unsubscribe when done.
+type broadcastCapture struct {
+	broker *handler.Broker
+	ch     chan handler.SSEEvent
+}
+
+func newBroadcastCapture(broker *handler.Broker) *broadcastCapture {
+	return &broadcastCapture{
+		broker: broker,
+		ch:     broker.Subscribe(),
+	}
+}
+
+// captured drains all pending events from the subscription channel
+// and returns them. This is synchronous — it only returns events that
+// have already been sent to the channel.
+func (bc *broadcastCapture) captured() []handler.SSEEvent {
+	var events []handler.SSEEvent
+	for {
+		select {
+		case evt := <-bc.ch:
+			events = append(events, evt)
+		default:
+			return events
+		}
+	}
+}
+
+func (bc *broadcastCapture) close() {
+	bc.broker.Unsubscribe(bc.ch)
+}
+
+// ── Test helpers ──────────────────────────────────────────────────────────
+
+// newTestWSClient creates a WSClient wired to a mock repo and a real broker.
+// Returns the client, the mock repo, and a broadcast capture.
+func newTestWSClient() (*WSClient, *mockAgentRepo, *handler.Broker, *broadcastCapture) {
+	repo := &mockAgentRepo{agents: make(map[string]models.AgentCardData)}
+	broker := handler.NewBroker()
+	capture := newBroadcastCapture(broker)
+	client := NewWSClient(WSConfig{}, repo, broker, slog.Default())
+	return client, repo, broker, capture
+}
+
+// ── Tests ─────────────────────────────────────────────────────────────────
+
+func TestHandleSessionsChanged_Active(t *testing.T) {
+	client, repo, _, capture := newTestWSClient()
+	defer capture.close()
+
+	repo.agents["otto"] = models.AgentCardData{
+		ID:          "otto",
+		DisplayName: "Otto",
+		Status:      models.AgentStatusIdle,
+	}
+
+	payload := json.RawMessage(`{
+		"sessionKey": "s1",
+		"agentId":    "otto",
+		"status":     "running",
+		"totalTokens": 500,
+		"currentTask": "Orchestrating tasks"
+	}`)
+
+	client.handleSessionsChanged(payload)
+
+	// Verify: agent status updated to active
+	repo.mu.Lock()
+	agent := repo.agents["otto"]
+	calls := make([]updateCall, len(repo.updateCalls))
+	copy(calls, repo.updateCalls)
+	repo.mu.Unlock()
+
+	if agent.Status != models.AgentStatusActive {
+		t.Errorf("agent status = %q, want %q", agent.Status, models.AgentStatusActive)
+	}
+
+	// Verify: update was called
+	if len(calls) == 0 {
+		t.Fatal("expected at least one update call")
+	}
+	if calls[0].id != "otto" {
+		t.Errorf("update call agentId = %q, want %q", calls[0].id, "otto")
+	}
+
+	// Verify: broker broadcast "agent.status"
+	events := capture.captured()
+	found := false
+	for _, evt := range events {
+		if evt.EventType == "agent.status" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Error("expected broker broadcast with event type 'agent.status'")
+	}
+}
+
+func TestHandleSessionsChanged_Idle(t *testing.T) {
+	client, repo, _, capture := newTestWSClient()
+	defer capture.close()
+
+	repo.agents["dex"] = models.AgentCardData{
+		ID:          "dex",
+		DisplayName: "Dex",
+		Status:      models.AgentStatusActive,
+		CurrentTask: strPtr("Writing API"),
+	}
+
+	payload := json.RawMessage(`{
+		"sessionKey": "s2",
+		"agentId":    "dex",
+		"status":     "done",
+		"totalTokens": 1000
+	}`)
+
+	client.handleSessionsChanged(payload)
+
+	repo.mu.Lock()
+	agent := repo.agents["dex"]
+	repo.mu.Unlock()
+
+	// Verify: agent goes idle
+	if agent.Status != models.AgentStatusIdle {
+		t.Errorf("agent status = %q, want %q", agent.Status, models.AgentStatusIdle)
+	}
+
+	// Verify: current task cleared (set to empty string)
+	if agent.CurrentTask != nil && *agent.CurrentTask != "" {
+		t.Errorf("current task = %q, want empty (cleared on idle)", *agent.CurrentTask)
+	}
+
+	// Verify: broker fires "agent.status"
+	events := capture.captured()
+	found := false
+	for _, evt := range events {
+		if evt.EventType == "agent.status" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Error("expected broker broadcast with event type 'agent.status'")
+	}
+}
+
+func TestHandleSessionsChanged_ArrayPayload(t *testing.T) {
+	client, repo, _, capture := newTestWSClient()
+	defer capture.close()
+
+	repo.agents["otto"] = models.AgentCardData{ID: "otto", DisplayName: "Otto", Status: models.AgentStatusIdle}
+	repo.agents["dex"] = models.AgentCardData{ID: "dex", DisplayName: "Dex", Status: models.AgentStatusIdle}
+
+	payload := json.RawMessage(`[
+		{"sessionKey":"s1","agentId":"otto","status":"running","totalTokens":100},
+		{"sessionKey":"s2","agentId":"dex","status":"streaming","totalTokens":200}
+	]`)
+
+	client.handleSessionsChanged(payload)
+
+	repo.mu.Lock()
+	otto := repo.agents["otto"]
+	dex := repo.agents["dex"]
+	repo.mu.Unlock()
+
+	if otto.Status != models.AgentStatusActive {
+		t.Errorf("otto status = %q, want active", otto.Status)
+	}
+	if dex.Status != models.AgentStatusActive {
+		t.Errorf("dex status = %q, want active", dex.Status)
+	}
+
+	// Both should produce broadcasts
+	events := capture.captured()
+	statusCount := 0
+	for _, evt := range events {
+		if evt.EventType == "agent.status" {
+			statusCount++
+		}
+	}
+	if statusCount < 2 {
+		t.Errorf("expected at least 2 agent.status broadcasts, got %d", statusCount)
+	}
+}
+
+func TestHandleSessionsChanged_SkipsEmptyAgentID(t *testing.T) {
+	client, _, _, capture := newTestWSClient()
+	defer capture.close()
+
+	payload := json.RawMessage(`{"sessionKey":"s1","agentId":"","status":"running"}`)
+	client.handleSessionsChanged(payload)
+
+	events := capture.captured()
+	if len(events) > 0 {
+		t.Errorf("expected no broadcasts for empty agentId, got %d", len(events))
+	}
+}
+
+func TestHandleSessionsChanged_UnparseablePayload(t *testing.T) {
+	client, _, _, capture := newTestWSClient()
+	defer capture.close()
+
+	payload := json.RawMessage(`not json at all`)
+	client.handleSessionsChanged(payload)
+
+	events := capture.captured()
+	if len(events) > 0 {
+		t.Errorf("expected no broadcasts for unparseable payload, got %d", len(events))
+	}
+}
+
+func TestHandlePresence(t *testing.T) {
+	client, repo, _, capture := newTestWSClient()
+	defer capture.close()
+
+	repo.agents["pip"] = models.AgentCardData{
+		ID:          "pip",
+		DisplayName: "Pip",
+		Status:      models.AgentStatusActive,
+	}
+
+	payload := json.RawMessage(`{
+		"agentId":        "pip",
+		"connected":      true,
+		"lastActivityAt": "2025-01-01T00:00:00Z"
+	}`)
+
+	client.handlePresence(payload)
+
+	repo.mu.Lock()
+	agent := repo.agents["pip"]
+	calls := make([]updateCall, len(repo.updateCalls))
+	copy(calls, repo.updateCalls)
+	repo.mu.Unlock()
+
+	// Agent should still be active (connected=true doesn't change status)
+	if agent.Status != models.AgentStatusActive {
+		t.Errorf("agent status = %q, want active", agent.Status)
+	}
+
+	// Update should have been called (for lastActivityAt)
+	if len(calls) == 0 {
+		t.Fatal("expected at least one update call")
+	}
+
+	// Verify broadcast
+	events := capture.captured()
+	found := false
+	for _, evt := range events {
+		if evt.EventType == "agent.status" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Error("expected broker broadcast with event type 'agent.status'")
+	}
+}
+
+func TestHandlePresence_Disconnect(t *testing.T) {
+	client, repo, _, capture := newTestWSClient()
+	defer capture.close()
+
+	repo.agents["pip"] = models.AgentCardData{
+		ID:          "pip",
+		DisplayName: "Pip",
+		Status:      models.AgentStatusActive,
+	}
+
+	payload := json.RawMessage(`{
+		"agentId":   "pip",
+		"connected": false
+	}`)
+
+	client.handlePresence(payload)
+
+	repo.mu.Lock()
+	agent := repo.agents["pip"]
+	repo.mu.Unlock()
+
+	// Agent should go idle on disconnect
+	if agent.Status != models.AgentStatusIdle {
+		t.Errorf("agent status = %q, want idle after disconnect", agent.Status)
+	}
+
+	events := capture.captured()
+	found := false
+	for _, evt := range events {
+		if evt.EventType == "agent.status" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Error("expected broker broadcast with event type 'agent.status' on disconnect")
+	}
+}
+
+func TestHandlePresence_EmptyAgentID(t *testing.T) {
+	client, _, _, capture := newTestWSClient()
+	defer capture.close()
+
+	payload := json.RawMessage(`{"agentId":"","connected":true}`)
+	client.handlePresence(payload)
+
+	events := capture.captured()
+	if len(events) > 0 {
+		t.Errorf("expected no broadcasts for empty agentId, got %d", len(events))
+	}
+}
+
+func TestHandleAgentConfig(t *testing.T) {
+	client, repo, _, capture := newTestWSClient()
+	defer capture.close()
+
+	repo.agents["rex"] = models.AgentCardData{
+		ID:          "rex",
+		DisplayName:  "Rex",
+		Role:        "Frontend Dev",
+		Status:      models.AgentStatusIdle,
+		Channel:     "discord",
+	}
+
+	payload := json.RawMessage(`{
+		"id":      "rex",
+		"name":    "Rex the Dev",
+		"role":    "Senior Frontend",
+		"channel": "telegram"
+	}`)
+
+	client.handleAgentConfig(payload)
+
+	repo.mu.Lock()
+	agent := repo.agents["rex"]
+	calls := make([]updateCall, len(repo.updateCalls))
+	copy(calls, repo.updateCalls)
+	repo.mu.Unlock()
+
+	// Verify DisplayName and Role updated
+	if agent.DisplayName != "Rex the Dev" {
+		t.Errorf("displayName = %q, want %q", agent.DisplayName, "Rex the Dev")
+	}
+	if agent.Role != "Senior Frontend" {
+		t.Errorf("role = %q, want %q", agent.Role, "Senior Frontend")
+	}
+	if agent.Channel != "telegram" {
+		t.Errorf("channel = %q, want %q", agent.Channel, "telegram")
+	}
+
+	// Verify update was called
+	if len(calls) == 0 {
+		t.Fatal("expected at least one update call")
+	}
+
+	// Verify broker fires "fleet.update"
+	events := capture.captured()
+	found := false
+	for _, evt := range events {
+		if evt.EventType == "fleet.update" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Error("expected broker broadcast with event type 'fleet.update'")
+	}
+}
+
+func TestHandleAgentConfig_EmptyID(t *testing.T) {
+	client, _, _, capture := newTestWSClient()
+	defer capture.close()
+
+	payload := json.RawMessage(`{"id":"","name":"Ghost"}`)
+	client.handleAgentConfig(payload)
+
+	events := capture.captured()
+	if len(events) > 0 {
+		t.Errorf("expected no broadcasts for empty id, got %d", len(events))
+	}
+}
+
+func TestHandleAgentConfig_NotFound(t *testing.T) {
+	client, _, _, capture := newTestWSClient()
+	defer capture.close()
+
+	payload := json.RawMessage(`{"id":"unknown","name":"Ghost","role":"Phantom"}`)
+	client.handleAgentConfig(payload)
+
+	// Agent doesn't exist in repo, so Update will fail → handler logs warning, returns early
+	events := capture.captured()
+	for _, evt := range events {
+		if evt.EventType == "fleet.update" {
+			t.Error("fleet.update should not be broadcast when agent update fails")
+		}
+	}
+}

go-backend/internal/gateway/sync_test.go

@@ -0,0 +1,236 @@
+package gateway
+
+import (
+	"context"
+	"testing"
+
+	"code.cubecraftcreations.com/CubeCraft-Creations/Control-Center/go-backend/internal/handler"
+	"code.cubecraftcreations.com/CubeCraft-Creations/Control-Center/go-backend/internal/models"
+)
+
+func TestInitialSync(t *testing.T) {
+	_ = &mockAgentRepo{agents: make(map[string]models.AgentCardData)} // verify mock compiles
+	broker := handler.NewBroker()
+	capture := newBroadcastCapture(broker)
+	defer capture.close()
+
+	// --- Test agentItemToCard + session merge (the core of initialSync) ---
+
+	agentItems := []agentListItem{
+		{ID: "otto", Name: "Otto", Role: "Orchestrator", Channel: "discord"},
+		{ID: "dex", Name: "Dex", Role: "Backend Dev", Channel: "telegram"},
+	}
+
+	sessionItems := []sessionListItem{
+		{SessionKey: "s1", AgentID: "otto", Status: "running", TotalTokens: 500, LastActivityAt: "2025-05-20T12:00:00Z"},
+		{SessionKey: "s2", AgentID: "dex", Status: "done", TotalTokens: 1000, LastActivityAt: "2025-05-20T11:00:00Z"},
+	}
+
+	// Build sessionByAgent map (mirrors initialSync logic)
+	sessionByAgent := make(map[string]sessionListItem)
+	for _, s := range sessionItems {
+		if s.AgentID != "" {
+			sessionByAgent[s.AgentID] = s
+		}
+	}
+
+	// Merge and verify
+	merged := make([]models.AgentCardData, 0, len(agentItems))
+	for _, item := range agentItems {
+		card := agentItemToCard(item)
+
+		if session, ok := sessionByAgent[item.ID]; ok {
+			card.SessionKey = session.SessionKey
+			card.Status = mapSessionStatus(session.Status)
+			card.LastActivity = session.LastActivityAt
+
+			if session.TotalTokens > 0 {
+				prog := min(session.TotalTokens/100, 100)
+				card.TaskProgress = &prog
+			}
+		}
+
+		merged = append(merged, card)
+	}
+
+	// Verify otto: running → active
+	if merged[0].ID != "otto" {
+		t.Errorf("merged[0].ID = %q, want %q", merged[0].ID, "otto")
+	}
+	if merged[0].Status != models.AgentStatusActive {
+		t.Errorf("otto status = %q, want %q (running → active)", merged[0].Status, models.AgentStatusActive)
+	}
+	if merged[0].SessionKey != "s1" {
+		t.Errorf("otto sessionKey = %q, want %q", merged[0].SessionKey, "s1")
+	}
+	if merged[0].TaskProgress == nil || *merged[0].TaskProgress != 5 {
+		t.Errorf("otto taskProgress = %v, want 5", merged[0].TaskProgress)
+	}
+
+	// Verify dex: done → idle
+	if merged[1].ID != "dex" {
+		t.Errorf("merged[1].ID = %q, want %q", merged[1].ID, "dex")
+	}
+	if merged[1].Status != models.AgentStatusIdle {
+		t.Errorf("dex status = %q, want %q (done → idle)", merged[1].Status, models.AgentStatusIdle)
+	}
+	if merged[1].SessionKey != "s2" {
+		t.Errorf("dex sessionKey = %q, want %q", merged[1].SessionKey, "s2")
+	}
+}
+
+func TestInitialSync_PersistCreatesNew(t *testing.T) {
+	repo := &mockAgentRepo{agents: make(map[string]models.AgentCardData)}
+	broker := handler.NewBroker()
+	capture := newBroadcastCapture(broker)
+	defer capture.close()
+
+	// Simulate the persist logic from initialSync:
+	// new agents should be created
+	card := agentItemToCard(agentListItem{ID: "otto", Name: "Otto", Role: "Orchestrator", Channel: "discord"})
+
+	ctx := context.Background()
+
+	// Agent doesn't exist → create
+	_, err := repo.Get(ctx, card.ID)
+	if err == nil {
+		t.Fatal("expected agent to not exist yet")
+	}
+
+	if err := repo.Create(ctx, card); err != nil {
+		t.Fatalf("Create failed: %v", err)
+	}
+
+	got, err := repo.Get(ctx, card.ID)
+	if err != nil {
+		t.Fatalf("Get after Create failed: %v", err)
+	}
+
+	if got.ID != "otto" {
+		t.Errorf("got.ID = %q, want %q", got.ID, "otto")
+	}
+	if got.DisplayName != "Otto" {
+		t.Errorf("got.DisplayName = %q, want %q", got.DisplayName, "Otto")
+	}
+	if got.Role != "Orchestrator" {
+		t.Errorf("got.Role = %q, want %q", got.Role, "Orchestrator")
+	}
+}
+
+func TestInitialSync_PersistUpdatesExisting(t *testing.T) {
+	repo := &mockAgentRepo{agents: make(map[string]models.AgentCardData)}
+	broker := handler.NewBroker()
+	capture := newBroadcastCapture(broker)
+	defer capture.close()
+
+	ctx := context.Background()
+
+	// Pre-populate with existing agent
+	repo.agents["otto"] = models.AgentCardData{
+		ID:          "otto",
+		DisplayName:  "Otto",
+		Role:        "Old Role",
+		Status:      models.AgentStatusIdle,
+	}
+
+	// Simulate initialSync: agent exists, name/role changed → update
+	newName := "Otto Prime"
+	newRole := "Super Orchestrator"
+	_, err := repo.Update(ctx, "otto", models.UpdateAgentRequest{
+		DisplayName: &newName,
+		Role:        &newRole,
+	})
+	if err != nil {
+		t.Fatalf("Update failed: %v", err)
+	}
+
+	got, err := repo.Get(ctx, "otto")
+	if err != nil {
+		t.Fatalf("Get after Update failed: %v", err)
+	}
+
+	if got.DisplayName != "Otto Prime" {
+		t.Errorf("displayName = %q, want %q", got.DisplayName, "Otto Prime")
+	}
+	if got.Role != "Super Orchestrator" {
+		t.Errorf("role = %q, want %q", got.Role, "Super Orchestrator")
+	}
+}
+
+func TestInitialSync_MergesSessionStatus(t *testing.T) {
+	// When initialSync merges session state, an agent whose existing status
+	// differs from the session-derived status should be updated.
+	repo := &mockAgentRepo{agents: make(map[string]models.AgentCardData)}
+	ctx := context.Background()
+
+	repo.agents["otto"] = models.AgentCardData{
+		ID:          "otto",
+		DisplayName:  "Otto",
+		Role:        "Orchestrator",
+		Status:      models.AgentStatusIdle,
+	}
+
+	// Simulate session merge: session says "running" → agent should go active
+	activeStatus := mapSessionStatus("running")
+	if activeStatus != models.AgentStatusActive {
+		t.Fatalf("mapSessionStatus(running) = %q, want active", activeStatus)
+	}
+
+	_, err := repo.Update(ctx, "otto", models.UpdateAgentRequest{
+		Status: &activeStatus,
+	})
+	if err != nil {
+		t.Fatalf("Update failed: %v", err)
+	}
+
+	got, err := repo.Get(ctx, "otto")
+	if err != nil {
+		t.Fatalf("Get failed: %v", err)
+	}
+
+	if got.Status != models.AgentStatusActive {
+		t.Errorf("status after merge = %q, want %q", got.Status, models.AgentStatusActive)
+	}
+}
+
+func TestInitialSync_BroadcastsFleet(t *testing.T) {
+	repo := &mockAgentRepo{agents: make(map[string]models.AgentCardData)}
+	broker := handler.NewBroker()
+	capture := newBroadcastCapture(broker)
+	defer capture.close()
+
+	// Create some agents in the repo
+	repo.agents["otto"] = models.AgentCardData{ID: "otto", DisplayName: "Otto", Status: models.AgentStatusActive}
+	repo.agents["dex"] = models.AgentCardData{ID: "dex", DisplayName: "Dex", Status: models.AgentStatusIdle}
+
+	// Simulate the final broadcast from initialSync
+	mergedAgents := []models.AgentCardData{
+		repo.agents["otto"],
+		repo.agents["dex"],
+	}
+	broker.Broadcast("fleet.update", mergedAgents)
+
+	events := capture.captured()
+	if len(events) == 0 {
+		t.Fatal("expected at least one broadcast event")
+	}
+
+	found := false
+	for _, evt := range events {
+		if evt.EventType == "fleet.update" {
+			found = true
+			// Verify data is the merged agents list
+			agents, ok := evt.Data.([]models.AgentCardData)
+			if !ok {
+				t.Fatalf("fleet.update data type = %T, want []models.AgentCardData", evt.Data)
+			}
+			if len(agents) != 2 {
+				t.Errorf("fleet.update agents count = %d, want 2", len(agents))
+			}
+			break
+		}
+	}
+	if !found {
+		t.Error("expected fleet.update broadcast event")
+	}
+}

go-backend/internal/gateway/wsclient.go

@@ -229,7 +229,34 @@ func (c *WSClient) connectAndRun(ctx context.Context) error {
 	c.connId = helloOK.ConnID
 	c.connMu.Unlock()
 
-	// Notify REST client that WS is live so it stands down
+	// Step 2b: Register live event handlers BEFORE starting the read
+	// loop. This eliminates the race window where readLoop dispatches
+	// live events as "unhandled" because no handlers are registered yet.
+	// The handlers only depend on c.agents and c.broker, which are wired
+	// in the constructor — they do not need initialSync to have completed.
+	c.registerEventHandlers()
+
+	// Step 2c: Start the read loop in a goroutine so that Send() in
+	// initialSync can receive responses. The read loop goroutine will
+	// continue running after initialSync completes, routing live events
+	// and any future RPC responses. Because handlers are already
+	// registered, any events arriving during or after initialSync are
+	// dispatched correctly.
+	readLoopErrCh := make(chan error, 1)
+	go func() {
+		readLoopErrCh <- c.readLoop(ctx, conn)
+	}()
+
+	// Step 2d: Initial sync — fetch agents + sessions from gateway.
+	// This works because the read loop is active and will route
+	// response frames back to Send() via handleResponse.
+	if err := c.initialSync(ctx); err != nil {
+		c.logger.Warn("initial sync failed, will continue with read loop", "error", err)
+	}
+
+	// Notify REST client that WS is live so it stands down.
+	// This must happen AFTER initialSync so that the REST poller
+	// doesn't start polling while we're still syncing.
 	if c.restClient != nil {
 		c.restClient.MarkWSReady()
 		c.logger.Info("ws client notified REST fallback to stand down")
@@ -238,16 +265,9 @@ func (c *WSClient) connectAndRun(ctx context.Context) error {
 	// Reset wsReadyOnce so MarkWSReady can fire again after a reconnect
 	c.wsReadyOnce = sync.Once{}
 
-	// Step 2b: Initial sync — fetch agents + sessions from gateway
+	// Step 3: Wait for the read loop goroutine to finish (blocks
-	if err := c.initialSync(ctx); err != nil {
+	// until the connection drops or context is cancelled).
-		c.logger.Warn("initial sync failed, will continue with read loop", "error", err)
+	return <-readLoopErrCh
-	}
-
-	// Step 2c: Register live event handlers
-	c.registerEventHandlers()
-
-	// Step 3: Read loop
-	return c.readLoop(ctx, conn)
 }
 
 // readChallenge reads the first frame from the gateway, which must be a

go-backend/internal/gateway/wsclient_test.go

@@ -11,6 +11,7 @@ import (
 	"testing"
 	"time"
 
+	"code.cubecraftcreations.com/CubeCraft-Creations/Control-Center/go-backend/internal/handler"
 	"code.cubecraftcreations.com/CubeCraft-Creations/Control-Center/go-backend/internal/models"
 
 	"github.com/gorilla/websocket"
@@ -466,6 +467,236 @@ func TestAgentItemToCard(t *testing.T) {
 	})
 }
 
+// ── 6. Test: Initial sync ordering (readLoop active before Send) ──────────
+
+// TestConnectAndRun_InitialSyncOrdering verifies that the WS client
+// completes initial sync successfully. This test would hang/timeout if
+// readLoop were NOT started before initialSync, because Send() relies on
+// readLoop→routeFrame→handleResponse to deliver RPC responses.
+func TestConnectAndRun_InitialSyncOrdering(t *testing.T) {
+	repo := &mockAgentRepo{agents: make(map[string]models.AgentCardData)}
+	broker := handler.NewBroker()
+	capture := newBroadcastCapture(broker)
+	defer capture.close()
+
+	srv := newTestWSServer(t, func(conn *websocket.Conn) {
+		// Handshake
+		handleHandshake(t, conn)
+
+		// After handshake, respond to RPCs
+		for {
+			var req map[string]any
+			if err := conn.ReadJSON(&req); err != nil {
+				break
+			}
+			reqID, _ := req["id"].(string)
+			method, _ := req["method"].(string)
+
+			var result any
+			switch method {
+			case "agents.list":
+				result = []map[string]any{
+					{"id": "otto", "name": "Otto", "role": "Orchestrator", "channel": "discord"},
+					{"id": "dex", "name": "Dex", "role": "Backend Dev", "channel": "telegram"},
+				}
+			case "sessions.list":
+				result = []map[string]any{
+					{"sessionKey": "s1", "agentId": "otto", "status": "running", "totalTokens": 500, "lastActivityAt": "2025-05-20T12:00:00Z"},
+				}
+			default:
+				result = map[string]any{}
+			}
+
+			res := map[string]any{
+				"type":   "res",
+				"id":     reqID,
+				"ok":     true,
+				"result": result,
+			}
+			if err := conn.WriteJSON(res); err != nil {
+				break
+			}
+		}
+	})
+	defer srv.Close()
+
+	client := NewWSClient(WSConfig{URL: wsURL(srv), AuthToken: "test-token"}, repo, broker, slog.Default())
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	done := make(chan struct{})
+	go func() {
+		client.Start(ctx)
+		close(done)
+	}()
+
+	// Wait for initial sync to complete by checking repo state.
+	// The agents should be persisted from the RPC responses.
+	deadline := time.Now().Add(5 * time.Second)
+	for time.Now().Before(deadline) {
+		repo.mu.Lock()
+		_, ottoOK := repo.agents["otto"]
+		_, dexOK := repo.agents["dex"]
+		repo.mu.Unlock()
+		if ottoOK && dexOK {
+			break
+		}
+		time.Sleep(50 * time.Millisecond)
+	}
+
+	repo.mu.Lock()
+	_, ottoOK := repo.agents["otto"]
+	_, dexOK := repo.agents["dex"]
+	repo.mu.Unlock()
+
+	if !ottoOK {
+		t.Error("otto not found in repo after initial sync — readLoop may not have been active before Send()")
+	}
+	if !dexOK {
+		t.Error("dex not found in repo after initial sync — readLoop may not have been active before Send()")
+	}
+
+	cancel()
+	select {
+	case <-done:
+	case <-time.After(3 * time.Second):
+		t.Fatal("WSClient did not shut down cleanly")
+	}
+}
+
+// ── 7. Test: Event not lost during initial sync (regression) ───────────────
+
+// TestConnectAndRun_EventNotLostDuringSync verifies that live gateway events
+// arriving during initial sync are NOT dropped. This is a regression test
+// for the race where readLoop started before registerEventHandlers(),
+// causing events read during that window to be logged as "unhandled" and lost.
+//
+// The mock server sends a live event (sessions.changed) right after the
+// handshake, interleaved with the RPC responses for agents.list and
+// sessions.list. The test asserts the event is received by the handler.
+func TestConnectAndRun_EventNotLostDuringSync(t *testing.T) {
+	repo := &mockAgentRepo{agents: make(map[string]models.AgentCardData)}
+	broker := handler.NewBroker()
+	capture := newBroadcastCapture(broker)
+	defer capture.close()
+
+	// Pre-seed an agent so the event handler can update it.
+	repo.agents["otto"] = models.AgentCardData{
+		ID:          "otto",
+		DisplayName: "Otto",
+		Status:      models.AgentStatusIdle,
+	}
+
+	srv := newTestWSServer(t, func(conn *websocket.Conn) {
+		// Handshake
+		handleHandshake(t, conn)
+
+		// After handshake, process RPCs and inject a live event.
+		for {
+			var req map[string]any
+			if err := conn.ReadJSON(&req); err != nil {
+				break
+			}
+			reqID, _ := req["id"].(string)
+			method, _ := req["method"].(string)
+
+			// Respond to agents.list RPC
+			if method == "agents.list" {
+				// Before responding, inject a live event — simulates
+				// a gateway pushing a presence update during sync.
+				evt := map[string]any{
+					"type":   "event",
+					"event":  "presence",
+					"params": map[string]any{"agentId": "otto", "connected": true, "lastActivityAt": "2025-05-20T12:30:00Z"},
+				}
+				if err := conn.WriteJSON(evt); err != nil {
+					break
+				}
+
+				// Now send the RPC response
+				res := map[string]any{
+					"type":   "res",
+					"id":     reqID,
+					"ok":     true,
+					"result": []map[string]any{
+						{"id": "otto", "name": "Otto", "role": "Orchestrator", "channel": "discord"},
+					},
+				}
+				if err := conn.WriteJSON(res); err != nil {
+					break
+				}
+				continue
+			}
+
+			// Respond to sessions.list RPC
+			if method == "sessions.list" {
+				res := map[string]any{
+					"type":   "res",
+					"id":     reqID,
+					"ok":     true,
+					"result": []map[string]any{},
+				}
+				if err := conn.WriteJSON(res); err != nil {
+					break
+				}
+				continue
+			}
+
+			// Default response for other methods
+			res := map[string]any{
+				"type":   "res",
+				"id":     reqID,
+				"ok":     true,
+				"result": map[string]any{},
+			}
+			if err := conn.WriteJSON(res); err != nil {
+				break
+			}
+		}
+	})
+	defer srv.Close()
+
+	client := NewWSClient(WSConfig{URL: wsURL(srv), AuthToken: "test-token"}, repo, broker, slog.Default())
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	done := make(chan struct{})
+	go func() {
+		client.Start(ctx)
+		close(done)
+	}()
+
+	// Wait for the presence event to be processed by checking the repo.
+	// The presence handler updates the agent, so we check for the
+	// lastActivityAt change.
+	deadline := time.Now().Add(5 * time.Second)
+	var lastActivity string
+	for time.Now().Before(deadline) {
+		repo.mu.Lock()
+		if a, ok := repo.agents["otto"]; ok {
+			lastActivity = a.LastActivity
+		}
+		repo.mu.Unlock()
+		if lastActivity == "2025-05-20T12:30:00Z" {
+			break
+		}
+		time.Sleep(50 * time.Millisecond)
+	}
+
+	if lastActivity != "2025-05-20T12:30:00Z" {
+		t.Errorf("presence event during sync was lost: lastActivity = %q, want %q", lastActivity, "2025-05-20T12:30:00Z")
+	}
+
+	cancel()
+	select {
+	case <-done:
+	case <-time.After(3 * time.Second):
+		t.Fatal("WSClient did not shut down cleanly")
+	}
+}
+
 func TestStrPtr(t *testing.T) {
 	s := "hello"
 	p := strPtr(s)