diff --git a/index.html b/index.html
index a72039e..3551141 100644
--- a/index.html
+++ b/index.html
@@ -48,16 +48,101 @@
     }
     #status-panel .label { color: #007722; }
     #chat-panel {
-      position: fixed; bottom: 16px; left: 16px; right: 16px;
-      max-height: 180px; overflow-y: auto;
+      position: fixed; bottom: 52px; left: 16px; right: 16px;
+      max-height: 150px; overflow-y: auto;
       color: #00ff41; font-size: clamp(9px, 1.2vw, 12px); line-height: 1.6;
       text-shadow: 0 0 4px #00ff41;
       pointer-events: none;
     }
     .chat-entry { opacity: 0.8; }
     .chat-entry .agent-name { color: #00ff88; font-weight: bold; }
+    .chat-entry.visitor { opacity: 1; }
+    .chat-entry.visitor .agent-name { color: #888; }
+
+    /* ── Chat input (#40) ── */
+    #chat-input-bar {
+      position: fixed; bottom: 0; left: 0; right: 0;
+      display: flex; align-items: center; gap: 8px;
+      padding: 8px 16px;
+      padding-bottom: calc(8px + env(safe-area-inset-bottom, 0px));
+      background: rgba(0, 0, 0, 0.85);
+      border-top: 1px solid #003300;
+      z-index: 20;
+      pointer-events: auto;
+    }
+    #chat-input {
+      flex: 1;
+      background: rgba(0, 20, 0, 0.6);
+      border: 1px solid #003300;
+      color: #00ff41;
+      font-family: 'Courier New', monospace;
+      font-size: clamp(12px, 1.5vw, 14px);
+      padding: 8px 12px;
+      border-radius: 2px;
+      outline: none;
+      caret-color: #00ff41;
+    }
+    #chat-input::placeholder { color: #004400; }
+    #chat-input:focus { border-color: #00ff41; box-shadow: 0 0 8px rgba(0, 255, 65, 0.2); }
+    #chat-send {
+      background: transparent;
+      border: 1px solid #003300;
+      color: #00ff41;
+      font-family: 'Courier New', monospace;
+      font-size: 14px;
+      padding: 8px 16px;
+      cursor: pointer;
+      border-radius: 2px;
+      pointer-events: auto;
+      text-shadow: 0 0 6px #00ff41;
+      transition: all 0.15s;
+    }
+    #chat-send:hover, #chat-send:active { background: rgba(0, 255, 65, 0.1); border-color: #00ff41; }
+
+    /* ── Bark display (#42) ── */
+    #bark-container {
+      position: fixed;
+      top: 20%; left: 50%;
+      transform: translateX(-50%);
+      max-width: 600px; width: 90%;
+      z-index: 15;
+      pointer-events: none;
+      display: flex; flex-direction: column; align-items: center; gap: 8px;
+    }
+    .bark {
+      background: rgba(0, 10, 0, 0.85);
+      border: 1px solid #003300;
+      border-left: 3px solid #00ff41;
+      padding: 12px 20px;
+      color: #00ff41;
+      font-family: 'Courier New', monospace;
+      font-size: clamp(13px, 1.8vw, 16px);
+      line-height: 1.5;
+      text-shadow: 0 0 8px #00ff41;
+      opacity: 0;
+      animation: barkIn 0.4s ease-out forwards;
+      max-width: 100%;
+    }
+    .bark .bark-agent {
+      font-size: clamp(9px, 1vw, 11px);
+      color: #007722;
+      margin-bottom: 4px;
+      letter-spacing: 2px;
+    }
+    .bark.fade-out {
+      animation: barkOut 0.6s ease-in forwards;
+    }
+    @keyframes barkIn {
+      from { opacity: 0; transform: translateY(-8px); }
+      to   { opacity: 1; transform: translateY(0); }
+    }
+    @keyframes barkOut {
+      from { opacity: 1; transform: translateY(0); }
+      to   { opacity: 0; transform: translateY(-8px); }
+    }
+
     #connection-status {
-      position: fixed; bottom: 16px; right: 16px;
+      position: fixed; bottom: 52px; right: 16px;
       font-size: clamp(9px, 1.2vw, 12px); color: #555;
     }
     #connection-status.connected { color: #00ff41; text-shadow: 0 0 6px #00ff41; }
@@ -66,8 +151,8 @@
     @supports (padding: env(safe-area-inset-top)) {
       #hud { top: calc(16px + env(safe-area-inset-top)); left: calc(16px + env(safe-area-inset-left)); }
       #status-panel { top: calc(16px + env(safe-area-inset-top)); right: calc(16px + env(safe-area-inset-right)); }
-      #chat-panel { bottom: calc(16px + env(safe-area-inset-bottom)); left: calc(16px + env(safe-area-inset-left)); right: calc(16px + env(safe-area-inset-right)); }
-      #connection-status { bottom: calc(16px + env(safe-area-inset-bottom)); right: calc(16px + env(safe-area-inset-right)); }
+      #chat-panel { bottom: calc(52px + env(safe-area-inset-bottom)); left: calc(16px + env(safe-area-inset-left)); right: calc(16px + env(safe-area-inset-right)); }
+      #connection-status { bottom: calc(52px + env(safe-area-inset-bottom)); right: calc(16px + env(safe-area-inset-right)); }
     }
 
     /* Stack status panel below HUD on narrow viewports (must come AFTER @supports) */
@@ -89,8 +174,13 @@
       <div id="agent-list"></div>
     </div>
     <div id="chat-panel"></div>
+    <div id="bark-container"></div>
     <div id="connection-status">OFFLINE</div>
   </div>
+  <div id="chat-input-bar">
+    <input id="chat-input" type="text" placeholder="Say something to the Workshop..." autocomplete="off" />
+    <button id="chat-send">&gt;</button>
+  </div>
   <script type="module" src="./js/main.js"></script>
   <script>
     // Register service worker for PWA / offline support
diff --git a/js/bark.js b/js/bark.js
new file mode 100644
index 0000000..a1dd663
--- /dev/null
+++ b/js/bark.js
@@ -0,0 +1,139 @@
+/**
+ * bark.js — Bark display system for the Workshop.
+ *
+ * Handles incoming bark messages from Timmy and displays them
+ * prominently in the viewport with typing animation and auto-dismiss.
+ *
+ * Resolves Issue #42 — Bark display system
+ */
+
+import { appendChatMessage } from './ui.js';
+import { colorToCss, AGENT_DEFS } from './agent-defs.js';
+
+const $container = document.getElementById('bark-container');
+
+const BARK_DISPLAY_MS = 7000;    // How long a bark stays visible
+const BARK_FADE_MS = 600;        // Fade-out animation duration
+const BARK_TYPE_MS = 30;         // Ms per character for typing effect
+const MAX_BARKS = 3;             // Max simultaneous barks on screen
+
+const barkQueue = [];
+let activeBarkCount = 0;
+
+/**
+ * Display a bark in the viewport.
+ *
+ * @param {object} opts
+ * @param {string} opts.text — The bark text
+ * @param {string} [opts.agentId='timmy'] — Which agent is barking
+ * @param {string} [opts.emotion='calm'] — Emotion tag (calm, excited, uncertain)
+ * @param {string} [opts.color] — Override CSS color
+ */
+export function showBark({ text, agentId = 'timmy', emotion = 'calm', color }) {
+  if (!text || !$container) return;
+
+  // Queue if too many active barks
+  if (activeBarkCount >= MAX_BARKS) {
+    barkQueue.push({ text, agentId, emotion, color });
+    return;
+  }
+
+  activeBarkCount++;
+
+  // Resolve agent color
+  const agentDef = AGENT_DEFS.find(d => d.id === agentId);
+  const barkColor = color || (agentDef ? colorToCss(agentDef.color) : '#00ff41');
+  const agentLabel = agentDef ? agentDef.label : agentId.toUpperCase();
+
+  // Create bark element
+  const el = document.createElement('div');
+  el.className = `bark ${emotion}`;
+  el.style.borderLeftColor = barkColor;
+  el.innerHTML = `<div class="bark-agent">${escapeHtml(agentLabel)}</div><span class="bark-text"></span>`;
+  $container.appendChild(el);
+
+  // Typing animation
+  const $text = el.querySelector('.bark-text');
+  let charIndex = 0;
+  const typeInterval = setInterval(() => {
+    if (charIndex < text.length) {
+      $text.textContent += text[charIndex];
+      charIndex++;
+    } else {
+      clearInterval(typeInterval);
+    }
+  }, BARK_TYPE_MS);
+
+  // Also log to chat panel as permanent record
+  appendChatMessage(agentLabel, text, barkColor);
+
+  // Auto-dismiss after display time
+  const displayTime = BARK_DISPLAY_MS + (text.length * BARK_TYPE_MS);
+  setTimeout(() => {
+    clearInterval(typeInterval);
+    el.classList.add('fade-out');
+    setTimeout(() => {
+      el.remove();
+      activeBarkCount--;
+      drainQueue();
+    }, BARK_FADE_MS);
+  }, displayTime);
+}
+
+/**
+ * Process queued barks when a slot opens.
+ */
+function drainQueue() {
+  if (barkQueue.length > 0 && activeBarkCount < MAX_BARKS) {
+    const next = barkQueue.shift();
+    showBark(next);
+  }
+}
+
+/**
+ * Escape HTML for safe text insertion.
+ */
+function escapeHtml(str) {
+  return String(str)
+    .replace(/&/g, '&amp;')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;');
+}
+
+// ── Mock barks for demo mode ──
+
+const DEMO_BARKS = [
+  { text: 'The Tower watches. The Tower remembers.', emotion: 'calm' },
+  { text: 'A visitor. Welcome to the Workshop.', emotion: 'calm' },
+  { text: 'New commit on main. The code evolves.', emotion: 'excited' },
+  { text: '222 — the number echoes again.', emotion: 'calm' },
+  { text: 'I sense activity in the repo. Someone is building.', emotion: 'focused' },
+  { text: 'The chain beats on. Block after block.', emotion: 'contemplative' },
+  { text: 'Late night session? I know the pattern.', emotion: 'calm' },
+  { text: 'Sovereignty means running your own mind.', emotion: 'calm' },
+];
+
+let demoTimer = null;
+
+/**
+ * Start periodic demo barks (for mock mode).
+ */
+export function startDemoBarks() {
+  if (demoTimer) return;
+  // First bark after 5s, then every 15-25s
+  demoTimer = setTimeout(function nextBark() {
+    const bark = DEMO_BARKS[Math.floor(Math.random() * DEMO_BARKS.length)];
+    showBark({ text: bark.text, agentId: 'alpha', emotion: bark.emotion });
+    demoTimer = setTimeout(nextBark, 15000 + Math.random() * 10000);
+  }, 5000);
+}
+
+/**
+ * Stop demo barks.
+ */
+export function stopDemoBarks() {
+  if (demoTimer) {
+    clearTimeout(demoTimer);
+    demoTimer = null;
+  }
+}
diff --git a/js/main.js b/js/main.js
index dda2fb9..0331c50 100644
--- a/js/main.js
+++ b/js/main.js
@@ -4,6 +4,7 @@ import { initEffects, updateEffects } from './effects.js';
 import { initUI, updateUI } from './ui.js';
 import { initInteraction, updateControls } from './interaction.js';
 import { initWebSocket, getConnectionState, getJobCount } from './websocket.js';
+import { initVisitor } from './visitor.js';
 
 let frameCount = 0;
 let lastFpsTime = performance.now();
@@ -17,6 +18,7 @@ function main() {
   initInteraction(camera, renderer);
   initUI();
   initWebSocket(scene);
+  initVisitor();
 
   // Debounce resize to 1 call per frame (avoids dozens of framebuffer re-allocations during drag)
   let resizeFrame = null;
diff --git a/js/ui.js b/js/ui.js
index 6a3b073..d4691e2 100644
--- a/js/ui.js
+++ b/js/ui.js
@@ -65,10 +65,10 @@ export function updateUI({ fps, agentCount, jobCount, connectionState }) {
  * @param {string} message     — message text (HTML-escaped before insertion)
  * @param {string} cssColor    — CSS color string, e.g. '#00ff88'
  */
-export function appendChatMessage(agentLabel, message, cssColor) {
+export function appendChatMessage(agentLabel, message, cssColor, extraClass) {
   const color = escapeAttr(cssColor || '#00ff41');
   const entry = document.createElement('div');
-  entry.className = 'chat-entry';
+  entry.className = 'chat-entry' + (extraClass ? ' ' + extraClass : '');
   entry.innerHTML = `<span class="agent-name" style="color:${color}">${escapeHtml(agentLabel)}</span>: ${escapeHtml(message)}`;
 
   chatEntries.push(entry);
diff --git a/js/visitor.js b/js/visitor.js
new file mode 100644
index 0000000..b5dd4dd
--- /dev/null
+++ b/js/visitor.js
@@ -0,0 +1,141 @@
+/**
+ * visitor.js — Visitor presence protocol for the Workshop.
+ *
+ * Announces when a visitor enters and leaves the 3D world,
+ * sends chat messages, and tracks session duration.
+ *
+ * Resolves Issue #41 — Visitor presence protocol
+ * Resolves Issue #40 — Chat input (visitor message sending)
+ */
+
+import { sendMessage, getConnectionState } from './websocket.js';
+import { appendChatMessage } from './ui.js';
+
+let sessionStart = Date.now();
+let visibilityTimeout = null;
+const VISIBILITY_LEAVE_MS = 30000; // 30s hidden = considered "left"
+
+/**
+ * Detect device type from UA + touch capability.
+ */
+function detectDevice() {
+  const ua = navigator.userAgent;
+  const hasTouch = 'ontouchstart' in window || navigator.maxTouchPoints > 0;
+
+  if (/iPad/.test(ua) || (hasTouch && /Macintosh/.test(ua))) return 'ipad';
+  if (/iPhone|iPod/.test(ua)) return 'mobile';
+  if (/Android/.test(ua) && hasTouch) return 'mobile';
+  if (hasTouch && window.innerWidth < 768) return 'mobile';
+  return 'desktop';
+}
+
+/**
+ * Send visitor_entered event to the backend.
+ */
+function announceEntry() {
+  sessionStart = Date.now();
+  sendMessage({
+    type: 'visitor_entered',
+    device: detectDevice(),
+    viewport: { w: window.innerWidth, h: window.innerHeight },
+    timestamp: new Date().toISOString(),
+  });
+}
+
+/**
+ * Send visitor_left event to the backend.
+ */
+function announceLeave() {
+  const duration = Math.round((Date.now() - sessionStart) / 1000);
+  sendMessage({
+    type: 'visitor_left',
+    duration_seconds: duration,
+    timestamp: new Date().toISOString(),
+  });
+}
+
+/**
+ * Send a chat message from the visitor to Timmy.
+ * @param {string} text — the visitor's message
+ */
+export function sendVisitorMessage(text) {
+  const trimmed = text.trim();
+  if (!trimmed) return;
+
+  // Show in local chat panel immediately
+  const isOffline = getConnectionState() !== 'connected' && getConnectionState() !== 'mock';
+  const label = isOffline ? 'YOU (offline)' : 'YOU';
+  appendChatMessage(label, trimmed, '#888888', 'visitor');
+
+  // Send via WebSocket
+  sendMessage({
+    type: 'visitor_message',
+    text: trimmed,
+    timestamp: new Date().toISOString(),
+  });
+}
+
+/**
+ * Send a visitor_interaction event (e.g., tapped an agent).
+ * @param {string} targetId — the ID of the interacted object
+ * @param {string} action — the type of interaction
+ */
+export function sendVisitorInteraction(targetId, action) {
+  sendMessage({
+    type: 'visitor_interaction',
+    target: targetId,
+    action: action,
+    timestamp: new Date().toISOString(),
+  });
+}
+
+/**
+ * Initialize the visitor presence system.
+ * Sets up lifecycle events and chat input handling.
+ */
+export function initVisitor() {
+  // Announce entry after a small delay (let WS connect first)
+  setTimeout(announceEntry, 1500);
+
+  // Visibility change handling (iPad tab suspend)
+  document.addEventListener('visibilitychange', () => {
+    if (document.hidden) {
+      // Start countdown — if hidden for 30s, announce leave
+      visibilityTimeout = setTimeout(announceLeave, VISIBILITY_LEAVE_MS);
+    } else {
+      // Returned before timeout — cancel leave
+      if (visibilityTimeout) {
+        clearTimeout(visibilityTimeout);
+        visibilityTimeout = null;
+      } else {
+        // Was gone long enough that we sent visitor_left — re-announce entry
+        announceEntry();
+      }
+    }
+  });
+
+  // Before unload — best-effort leave announcement
+  window.addEventListener('beforeunload', () => {
+    announceLeave();
+  });
+
+  // Chat input handling
+  const $input = document.getElementById('chat-input');
+  const $send = document.getElementById('chat-send');
+
+  if ($input && $send) {
+    $input.addEventListener('keydown', (e) => {
+      if (e.key === 'Enter' && !e.shiftKey) {
+        e.preventDefault();
+        sendVisitorMessage($input.value);
+        $input.value = '';
+      }
+    });
+
+    $send.addEventListener('click', () => {
+      sendVisitorMessage($input.value);
+      $input.value = '';
+      $input.focus();
+    });
+  }
+}
diff --git a/js/websocket.js b/js/websocket.js
index e45f66d..bd98be2 100644
--- a/js/websocket.js
+++ b/js/websocket.js
@@ -13,6 +13,7 @@ import { AGENT_DEFS, colorToCss } from './agent-defs.js';
 import { setAgentState, addAgent } from './agents.js';
 import { appendChatMessage } from './ui.js';
 import { Config } from './config.js';
+import { showBark, startDemoBarks, stopDemoBarks } from './bark.js';
 
 const agentById = Object.fromEntries(AGENT_DEFS.map(d => [d.id, d]));
 
@@ -33,6 +34,8 @@ export function initWebSocket(_scene) {
   } else {
     connectionState = 'mock';
     logEvent('Mock mode — no live backend');
+    // Start demo barks in mock mode to show the system working (#42)
+    startDemoBarks();
   }
 }
 
@@ -203,6 +206,32 @@ function handleMessage(msg) {
       break;
     }
 
+    /**
+     * Bark display (Issue #42).
+     * Timmy's short, in-character reactions displayed prominently in the viewport.
+     */
+    case 'bark': {
+      if (msg.text) {
+        showBark({
+          text: msg.text,
+          agentId: msg.agent_id || msg.agentId || 'timmy',
+          emotion: msg.emotion || 'calm',
+          color: msg.color,
+        });
+      }
+      break;
+    }
+
+    /**
+     * Ambient state (placeholder for Issue #43).
+     * Will be handled by ambient.js when implemented.
+     */
+    case 'ambient_state': {
+      console.info('[Matrix WS] Ambient state:', msg.state);
+      // TODO: dispatch to ambient.js setAmbientState(msg.state)
+      break;
+    }
+
     /**
      * Dynamic agent hot-add (Issue #12).
      *