diff --git a/extension/.gitignore b/extension/.gitignore
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--- /dev/null
+++ b/extension/.gitignore
@@ -0,0 +1,4 @@
+node_modules/
+web-ext-artifacts/
+.web-ext-id
+.amo-upload-uuid
diff --git a/extension/README.md b/extension/README.md
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+++ b/extension/README.md
@@ -0,0 +1,45 @@
+# FabledCurator Firefox Extension
+
+Self-hosted Firefox extension that pushes session cookies from supported
+platforms (Patreon, SubscribeStar, Hentai-Foundry, Discord, Pixiv,
+DeviantArt) into FabledCurator, and lets you add a creator as a Source
+from their page in one click.
+
+## Install (operator)
+
+The signed XPI is bundled into the FC Docker image. Open FC →
+Settings → Maintenance → Browser extension → click "Install Firefox
+extension". Firefox shows its native install prompt. After installing,
+open the extension's options page (about:addons → FabledCurator →
+Preferences) and paste in the FC URL + extension API key shown on the
+same card.
+
+## Develop
+
+```sh
+cd extension/
+npm install --no-save        # web-ext only
+npm run lint                 # web-ext lint
+npm run start                # launches Firefox with extension loaded
+npm run build                # unsigned XPI in web-ext-artifacts/
+```
+
+## Smoke checklist (after every release that touches `extension/**`)
+
+- [ ] `npm run lint` passes
+- [ ] `npm run start` loads the extension in a clean Firefox profile
+- [ ] Options page accepts FC URL + key, indicator turns green
+- [ ] Cookie export: log into patreon.com, click Patreon card → "X cookies exported"
+- [ ] Discord token: open discord.com, click Discord card → "Token captured"
+- [ ] Pixiv OAuth: click Pixiv card → login redirects, token stored
+- [ ] Add as source: visit patreon.com/<creator>, click floating button → toast
+- [ ] Subscriptions list: popup → "Sources" tab → list renders
+- [ ] Check now: click play icon on source row → no error toast
+
+## Release
+
+Bump `manifest.json` + `package.json` SemVer (both files) and commit
+under `extension/**`. The `.forgejo/workflows/extension.yml` workflow
+runs `web-ext sign` on main, commits the signed XPI to
+`frontend/public/extension/`, and the next FC server build bundles it
+into the Docker image.
diff --git a/extension/icons/icon.svg b/extension/icons/icon.svg
new file mode 100644
index 0000000..95f1e2d
--- /dev/null
+++ b/extension/icons/icon.svg
@@ -0,0 +1,5 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 96 96" width="96" height="96">
+  <rect width="96" height="96" rx="16" fill="#14171A"/>
+  <text x="48" y="62" font-family="Georgia, serif" font-size="56" font-weight="500"
+        fill="#F4BA7A" text-anchor="middle">F</text>
+</svg>
diff --git a/extension/manifest.json b/extension/manifest.json
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+++ b/extension/manifest.json
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+{
+  "manifest_version": 3,
+  "name": "FabledCurator",
+  "version": "1.0.0",
+  "description": "Export cookies from supported platforms to FabledCurator and add creators as sources in one click.",
+
+  "browser_specific_settings": {
+    "gecko": {
+      "id": "fabledcurator@fabledsword.com",
+      "strict_min_version": "115.0"
+    }
+  },
+
+  "permissions": [
+    "cookies",
+    "storage",
+    "tabs",
+    "activeTab",
+    "webRequest",
+    "webRequestBlocking"
+  ],
+
+  "host_permissions": [
+    "*://*.patreon.com/*",
+    "*://*.subscribestar.com/*",
+    "*://*.subscribestar.adult/*",
+    "*://*.hentai-foundry.com/*",
+    "*://*.discord.com/*",
+    "*://*.pixiv.net/*",
+    "*://*.deviantart.com/*",
+    "*://app-api.pixiv.net/*",
+    "*://oauth.secure.pixiv.net/*",
+    "*://*/*"
+  ],
+
+  "action": {
+    "default_popup": "popup/popup.html",
+    "default_icon": "icons/icon.svg",
+    "default_title": "FabledCurator"
+  },
+
+  "background": {
+    "scripts": ["lib/platforms.js", "lib/cookies.js", "lib/api.js", "background/background.js"]
+  },
+
+  "options_ui": {
+    "page": "options/options.html",
+    "browser_style": true
+  },
+
+  "content_scripts": [
+    {
+      "matches": [
+        "*://*.patreon.com/*",
+        "*://*.subscribestar.com/*",
+        "*://*.subscribestar.adult/*",
+        "*://*.hentai-foundry.com/*",
+        "*://*.deviantart.com/*",
+        "*://*.pixiv.net/*"
+      ],
+      "js": ["lib/platforms.js", "content/content-script.js"],
+      "css": ["content/content-script.css"],
+      "run_at": "document_idle"
+    }
+  ],
+
+  "icons": {
+    "48": "icons/icon.svg",
+    "96": "icons/icon.svg"
+  }
+}
diff --git a/extension/package.json b/extension/package.json
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+++ b/extension/package.json
@@ -0,0 +1,15 @@
+{
+  "name": "fabledcurator-extension",
+  "version": "1.0.0",
+  "private": true,
+  "description": "Firefox extension for FabledCurator",
+  "scripts": {
+    "lint":  "web-ext lint --source-dir=.",
+    "start": "web-ext run --source-dir=. --firefox=firefox",
+    "build": "web-ext build --source-dir=. --overwrite-dest",
+    "sign":  "web-ext sign --source-dir=. --channel=unlisted --api-key=$WEB_EXT_API_KEY --api-secret=$WEB_EXT_API_SECRET"
+  },
+  "devDependencies": {
+    "web-ext": "^8.0.0"
+  }
+}
diff --git a/extension/web-ext-config.cjs b/extension/web-ext-config.cjs
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index 0000000..019579a
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+++ b/extension/web-ext-config.cjs
@@ -0,0 +1,13 @@
+module.exports = {
+  sourceDir: '.',
+  artifactsDir: './web-ext-artifacts',
+  ignoreFiles: [
+    'package.json',
+    'package-lock.json',
+    'web-ext-config.cjs',
+    'web-ext-artifacts',
+    'node_modules',
+    'README.md',
+    '.gitignore',
+  ],
+};