diff --git a/extension/content.js b/extension/content.js
new file mode 100644
index 0000000..df00446
--- /dev/null
+++ b/extension/content.js
@@ -0,0 +1,42 @@
+const CHAT_ORIGIN = 'https://inquid.github.io/github-chat'
+const CHAT_URL = CHAT_ORIGIN + '/index.html'
+
+let chatFrame = null
+let toggleBtn = null
+let isOpen = false
+
+function createToggle() {
+  toggleBtn = document.createElement('button')
+  toggleBtn.id = 'ghchat-toggle'
+  toggleBtn.innerHTML = `
+    <svg width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+      <path d="M21 15a2 2 0 0 1-2 2H7l-4 4V5a2 2 0 0 1 2-2h14a2 2 0 0 1 2 2z"></path>
+    </svg>
+  `
+  toggleBtn.setAttribute('aria-label', 'Toggle chat')
+  toggleBtn.addEventListener('click', toggleChat)
+  document.body.appendChild(toggleBtn)
+}
+
+function createChatFrame() {
+  chatFrame = document.createElement('div')
+  chatFrame.id = 'ghchat-frame'
+  chatFrame.innerHTML = `
+    <div id="ghchat-header">
+      <span>GitHub Chat</span>
+      <button id="ghchat-close" aria-label="Close chat">&times;</button>
+    </div>
+    <iframe src="${CHAT_URL}" id="ghchat-iframe" frameborder="0"></iframe>
+  `
+  chatFrame.querySelector('#ghchat-close').addEventListener('click', toggleChat)
+  document.body.appendChild(chatFrame)
+}
+
+function toggleChat() {
+  isOpen = !isOpen
+  chatFrame.classList.toggle('ghchat-open', isOpen)
+  toggleBtn.classList.toggle('ghchat-hidden', isOpen)
+}
+
+createToggle()
+createChatFrame()
diff --git a/extension/icons/icon128.png b/extension/icons/icon128.png
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diff --git a/extension/icons/icon16.png b/extension/icons/icon16.png
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diff --git a/extension/icons/icon48.png b/extension/icons/icon48.png
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diff --git a/extension/manifest.json b/extension/manifest.json
new file mode 100644
index 0000000..dfcafbc
--- /dev/null
+++ b/extension/manifest.json
@@ -0,0 +1,21 @@
+{
+  "manifest_version": 3,
+  "name": "GitHub Chat",
+  "version": "1.0.0",
+  "description": "Floating chat panel for GitHub pages. Toggle in the bottom-right corner.",
+  "permissions": [],
+  "host_permissions": ["https://github.com/*"],
+  "content_scripts": [
+    {
+      "matches": ["https://github.com/*"],
+      "js": ["content.js"],
+      "css": ["styles.css"],
+      "run_at": "document_end"
+    }
+  ],
+  "icons": {
+    "16": "icons/icon16.png",
+    "48": "icons/icon48.png",
+    "128": "icons/icon128.png"
+  }
+}
diff --git a/extension/styles.css b/extension/styles.css
new file mode 100644
index 0000000..25988d4
--- /dev/null
+++ b/extension/styles.css
@@ -0,0 +1,83 @@
+#ghchat-toggle {
+  position: fixed;
+  bottom: 20px;
+  right: 20px;
+  z-index: 999999;
+  width: 48px;
+  height: 48px;
+  border-radius: 50%;
+  background: #2da44e;
+  color: #fff;
+  border: none;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  box-shadow: 0 4px 12px rgba(0,0,0,0.25);
+  transition: transform 0.2s, opacity 0.2s, visibility 0.2s;
+}
+#ghchat-toggle:hover {
+  transform: scale(1.1);
+  background: #2c974b;
+}
+#ghchat-toggle.ghchat-hidden {
+  opacity: 0;
+  visibility: hidden;
+  transform: scale(0.8);
+}
+
+#ghchat-frame {
+  position: fixed;
+  bottom: 20px;
+  right: 20px;
+  z-index: 999999;
+  width: 360px;
+  height: 500px;
+  border-radius: 12px;
+  overflow: hidden;
+  box-shadow: 0 8px 32px rgba(0,0,0,0.3);
+  display: flex;
+  flex-direction: column;
+  transform: translateY(20px);
+  opacity: 0;
+  visibility: hidden;
+  transition: transform 0.25s ease, opacity 0.25s ease, visibility 0.25s;
+}
+#ghchat-frame.ghchat-open {
+  transform: translateY(0);
+  opacity: 1;
+  visibility: visible;
+}
+
+#ghchat-header {
+  background: #2da44e;
+  color: #fff;
+  padding: 10px 16px;
+  font: 14px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
+  font-weight: 600;
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  flex-shrink: 0;
+}
+#ghchat-header button {
+  background: none;
+  border: none;
+  color: #fff;
+  font-size: 20px;
+  cursor: pointer;
+  padding: 0 4px;
+  line-height: 1;
+  opacity: 0.8;
+}
+#ghchat-header button:hover {
+  opacity: 1;
+}
+
+#ghchat-iframe {
+  flex: 1;
+  width: 100%;
+  height: 100%;
+  background: #fff;
+  border: none;
+}