diff --git a/README.md b/README.md
index b9352ee..8c7216f 100644
--- a/README.md
+++ b/README.md
@@ -89,8 +89,9 @@ hyprcrd/
 ├── docker-entrypoint.sh
 ├── dist.sh                 # Build distribution ZIP
 ├── src/
-│   ├── bootstrap.php       # Initialization
+│   ├── bootstrap.php       # Initialization + plugin discovery
 │   ├── Database.php        # SQLite schema & migrations
+│   ├── PluginManager.php   # Plugin scanner & asset/slot renderer
 │   ├── CalDavClient.php    # CalDAV HTTP client + iCal parser
 │   └── CalDavSync.php      # Bidirectional CalDAV sync engine
 ├── public/                 # Document root
@@ -103,9 +104,13 @@ hyprcrd/
 │   │   └── vendor/         # Phosphor Icons CSS + fonts
 │   ├── fonts/              # JetBrains Mono & Silkscreen
 │   ├── js/
+│   │   ├── hyprcrd.js      # Plugin API (window.hyprcrd, sync-loaded)
 │   │   ├── app.js          # Orchestrator
-│   │   ├── modules/        # Feature modules
+│   │   ├── modules/        # Core feature modules
 │   │   └── vendor/         # marked.js, DOMPurify
+│   ├── plugins/            # Optional, drop-in plugin folders
+│   │   ├── canvas/         # ASCII art canvas editor
+│   │   └── tests/          # UI + state test runner
 │   └── uploads/            # User media (writable)
 ├── relay/                  # Relay service (mobile inbox + card sharing)
 │   ├── index.php           # Single-file API + Mobile UI
@@ -121,7 +126,7 @@ hyprcrd/
 - **Cards** with markdown body, color, tags, and position
 - **Buckets** for organizing cards into groups
 - **Tags** written as `#tagname` or hierarchical `#parent/child` in card body, extracted automatically
-- **Markdown** with `[[Card Title]]` wiki-links, ```` ```gallery ```` image galleries, ```` ```tree ```` list views
+- **Markdown** with `[[Card Title]]` wiki-links, ```` ```gallery ```` image galleries, ```` ```tree ```` list views, ```` ```ascii ```` art canvas (via canvas plugin)
 - **Search** combining text and `#tag` filters (e.g. `#project meeting notes`)
 - **Image gallery** with orphan detection and fullscreen viewer
 - **Split view** showing tag-related and content-related cards
@@ -138,6 +143,101 @@ hyprcrd/
 - **Superview** compact multi-column list with hover cards
 - **Keyboard shortcuts**: `Ctrl+K` search, `F1` help, `Shift+scroll` zoom, arrow keys in autocomplete
 
+## Plugins
+
+hyprcrd has a drop-in plugin system. A plugin is just a folder under `public/plugins/` with a `plugin.json` manifest. The core scans the directory at startup, loads each plugin's CSS/JS/HTML, and the plugin self-registers against `window.hyprcrd`. Plugins are entirely optional — removing a plugin folder removes the feature, with no code changes anywhere else.
+
+### Bundled plugins
+
+- **`canvas/`** — ASCII art canvas editor. Adds a toolbar button + ` ```ascii ` fenced block. Draw with brush, line, rectangle, ellipse, fill, and text tools using a monospace character grid.
+- **`tests/`** — UI + state test runner (40+ test files). Loaded only when `?test` is in the URL or `Ctrl+Shift+T` is pressed, so production users pay no cost for it.
+
+### Plugin layout
+
+```
+public/plugins/myplugin/
+├── plugin.json     # Manifest (required)
+├── myplugin.js     # Entry point (loaded as ES module)
+├── myplugin.css    # Optional styles
+├── myplugin.html   # Optional HTML fragment (overlays, modals, etc.)
+└── backend.php     # Optional PHP hooks
+```
+
+**`plugin.json`:**
+
+```json
+{
+    "name": "myplugin",
+    "version": "1.0.0",
+    "description": "What this plugin does",
+    "frontend": {
+        "js":   ["myplugin.js"],
+        "css":  ["myplugin.css"],
+        "html": ["myplugin.html"]
+    },
+    "backend": "backend.php"
+}
+```
+
+### Plugin API (`window.hyprcrd`)
+
+Loaded synchronously before any module, so plugins can register handlers immediately:
+
+| Namespace | Methods | Purpose |
+|---|---|---|
+| `hyprcrd.editor` | `registerCommand(name, fn)`, `getCommand(name)`, `api.{body, insertMd, updatePreview}` | Add toolbar commands. The `data-md="<name>"` button dispatches to the registered handler. `api` is set after the editor initializes. |
+| `hyprcrd.markdown` | `registerFencedBlock(lang, fn)`, `registerPreProcessor(fn)`, `registerPostProcessor(fn)` | Add ` ```<lang> ` block renderers (returns HTML, passes through DOMPurify). Pre/post processors run on the source/HTML around `marked.parse()`. |
+| `hyprcrd.hooks` | `on(name, fn)`, `off(name, fn)`, `emit(name, data)` | Generic event bus. Use for cross-plugin or core→plugin signaling. |
+| `hyprcrd.util` | `$(idOrSel)`, `$$(sel)`, `esc(s)` | Lightweight DOM/escape helpers so plugins don't need to import core modules. |
+| `hyprcrd.registerPlugin(meta)` | — | Register the plugin's metadata for introspection. |
+
+### Minimal plugin example
+
+`public/plugins/hello/plugin.json`:
+
+```json
+{
+    "name": "hello",
+    "version": "1.0.0",
+    "description": "Inserts a greeting",
+    "frontend": { "js": ["hello.js"] }
+}
+```
+
+`public/plugins/hello/hello.js`:
+
+```js
+const h = window.hyprcrd;
+
+h.editor.registerCommand('hello', () => {
+    h.editor.api.insertMd('Hello, world! ', '', '');
+});
+
+// Inject a toolbar button
+const btn = document.createElement('button');
+btn.dataset.md = 'hello';
+btn.className = 'toolbar-btn';
+btn.title = 'Hello';
+btn.textContent = '👋';
+document.getElementById('md-toolbar').appendChild(btn);
+
+h.registerPlugin({ name: 'hello', version: '1.0.0' });
+```
+
+That's the entire plugin. Drop the folder in, reload, the button appears.
+
+### Backend hooks (PHP)
+
+If a plugin needs server-side code, set `"backend": "backend.php"` in the manifest. The file is `require_once`'d during bootstrap. Backend plugins can use `PluginManager::instance()->addToSlot('slot-name', '<html>')` to inject HTML into named slots in `index.php` (e.g. `md-toolbar`).
+
+### Removing a plugin
+
+```bash
+rm -rf public/plugins/canvas
+```
+
+That's it. The toolbar button, overlay, CSS, and markdown handler all disappear together. The core has no awareness of any specific plugin.
+
 ## Data & Backup
 
 All data lives in two places:
@@ -318,8 +418,8 @@ After changing Tailwind utility classes in HTML or JS files:
 # Download standalone CLI (once)
 curl -sL https://github.com/tailwindlabs/tailwindcss/releases/latest/download/tailwindcss-linux-x64 -o tailwindcss && chmod +x tailwindcss
 
-# Build
-./tailwindcss --input public/css/tailwind.css --output public/css/tailwind.out.css --content "public/index.php,public/js/**/*.js" --minify
+# Build (includes plugins so plugin HTML/JS contributes utility classes)
+./tailwindcss --input public/css/tailwind.css --output public/css/tailwind.out.css --content "public/index.php,public/js/**/*.js,public/plugins/**/*.{js,html}" --minify
 ```
 
 ## Security
diff --git a/public/css/style.css b/public/css/style.css
index 1c5b7fc..5d24de1 100644
--- a/public/css/style.css
+++ b/public/css/style.css
@@ -499,16 +499,6 @@ body.detail-image-fs-open { overflow: hidden; }
 #editor-gutter > div { padding-right: 2px; box-sizing: border-box; }
 .gutter-active { color: var(--t-accent) !important; font-weight: 700; background: var(--t-raised); }
 
-/* ASCII Canvas */
-#ascii-canvas-overlay { background: rgba(0,0,0,0.5); backdrop-filter: blur(2px); }
-.ascii-grid { white-space: pre; user-select: none; -webkit-user-select: none; display: inline-block; width: max-content; }
-.ascii-cursor { background: var(--t-accent); color: var(--t-bg); }
-.ascii-char-btn { font-family: var(--t-font-mono, monospace); font-size: 13px; width: 22px; height: 22px; display: inline-flex; align-items: center; justify-content: center; border: 1px solid var(--t-border); border-radius: 3px; background: var(--t-bg); color: var(--t-text); cursor: pointer; transition: all 0.1s; padding: 0; line-height: 1; }
-.ascii-char-btn:hover { background: var(--t-raised); color: var(--t-bright); }
-.ascii-char-btn.active { background: var(--t-accent); color: var(--t-bg); border-color: var(--t-accent); }
-.ascii-char-group { display: inline-flex; gap: 2px; margin-right: 6px; }
-#ascii-canvas-toolbar .toolbar-btn.active { background: var(--t-accent); color: var(--t-bg); }
-
 /* Search */
 #search { backdrop-filter: blur(4px); }
 #search-input { caret-color: var(--t-accent); }
@@ -563,7 +553,6 @@ body.detail-image-fs-open { overflow: hidden; }
 .prose code { background: var(--t-bg); border: 1px solid var(--t-border); padding: 0.15em 0.4em; border-radius: 3px; font-size: 0.88em; }
 .prose pre { background: var(--t-bg); border: 1px solid var(--t-border); padding: 0.8em 1em; overflow-x: auto; margin: 0.8em 0; border-radius: 3px; position: relative; }
 .prose pre code { background: none; border: none; padding: 0; font-size: 0.85em; }
-.prose pre.ascii-art { line-height: 1.35; letter-spacing: 0; white-space: pre; font-size: 0.85em; }
 .prose pre .code-copy {
     position: absolute; top: 4px; right: 4px;
     background: var(--t-surface); border: 1px solid var(--t-border);
diff --git a/public/index.php b/public/index.php
index 6b13394..954bd80 100644
--- a/public/index.php
+++ b/public/index.php
@@ -301,6 +301,33 @@ if (str_starts_with($route, '/api/')) {
         $card->execute(['id' => $m[1]]); echo json_encode($card->fetch()); exit;
     }
 
+    // Plugins
+    if ($route === '/api/plugins' && $method === 'GET') {
+        echo json_encode(PluginManager::instance()->pluginsForApi()); exit;
+    }
+
+    if ($route === '/api/plugins/toggle' && $method === 'POST') {
+        $input = json_decode(file_get_contents('php://input'), true);
+        $name = trim((string)($input['name'] ?? ''));
+        $enabled = !empty($input['enabled']);
+        if ($name === '') { http_response_code(400); echo json_encode(['error' => 'name required']); exit; }
+        $pm = PluginManager::instance();
+        $known = array_keys($pm->plugins());
+        if (!in_array($name, $known, true)) {
+            http_response_code(404); echo json_encode(['error' => 'plugin not found']); exit;
+        }
+        $disabled = $pm->disabledList();
+        if ($enabled) {
+            $disabled = array_values(array_diff($disabled, [$name]));
+        } else if (!in_array($name, $disabled, true)) {
+            $disabled[] = $name;
+        }
+        if (!$pm->setDisabled($disabled)) {
+            http_response_code(500); echo json_encode(['error' => 'failed to write state']); exit;
+        }
+        echo json_encode(['ok' => true, 'plugins' => $pm->pluginsForApi()]); exit;
+    }
+
     // Buckets
     if ($route === '/api/buckets' && $method === 'GET') {
         echo json_encode($db->query('SELECT * FROM buckets ORDER BY position ASC, created_at ASC')->fetchAll()); exit;
@@ -1012,6 +1039,7 @@ if (str_starts_with($route, '/api/')) {
     <script src="js/vendor/marked.min.js"></script>
     <script src="js/vendor/purify.min.js"></script>
     <link rel="stylesheet" href="css/style.css?v=<?= time() ?>">
+    <?= PluginManager::instance()->cssLinks() ?>
     <script>
     window.themes = {
         slate:    { label:'Slate',    vars:{ '--t-bg':'#1e293b','--t-surface':'#273349','--t-raised':'#2e3d56','--t-border':'#384a64','--t-dim':'#64748b','--t-muted':'#94a3b8','--t-text':'#cbd5e1','--t-bright':'#f1f5f9','--t-accent':'#38bdf8','--t-accent2':'#818cf8','--t-danger':'#fb7185','--t-scanline':'rgba(0,0,0,0.04)','--t-overlay':'rgba(15,23,42,0.75)','--t-font-pixel':'"Silkscreen", cursive','--t-cover-gradient':'linear-gradient(180deg, rgba(15,23,42,0.22) 0%, rgba(15,23,42,0.7) 62%, rgba(15,23,42,0.86) 100%)' }},
@@ -1350,6 +1378,7 @@ if (str_starts_with($route, '/api/')) {
                 <button class="settings-tab" data-tab="relay"><i class="ph ph-broadcast text-sm"></i><span class="font-pixel text-[10px]">relay</span></button>
                 <button class="settings-tab" data-tab="behavior"><i class="ph ph-sliders text-sm"></i><span class="font-pixel text-[10px]">behavior</span></button>
                 <button class="settings-tab" data-tab="notifications"><i class="ph ph-bell text-sm"></i><span class="font-pixel text-[10px]">notifications</span></button>
+                <button class="settings-tab" data-tab="plugins"><i class="ph ph-puzzle-piece text-sm"></i><span class="font-pixel text-[10px]">plugins</span></button>
             </div>
             <div class="flex-1 flex flex-col min-h-0">
                 <div class="flex items-center gap-3 px-5 py-3 border-b border-t-border shrink-0">
@@ -1521,6 +1550,18 @@ if (str_starts_with($route, '/api/')) {
                             <div id="notif-stream" class="max-h-64 overflow-y-auto space-y-1"></div>
                         </div>
                     </div>
+                    <div id="settings-panel-plugins" class="hidden space-y-4">
+                        <div>
+                            <div class="font-pixel text-[9px] uppercase tracking-wider text-t-dim mb-2"><i class="ph ph-puzzle-piece text-xs"></i> installed plugins</div>
+                            <p class="text-[10px] text-t-dim leading-relaxed mb-3">Plugins extend hyprcrd with optional features. Disable a plugin to skip loading its assets entirely. Toggling requires a page reload to take effect.</p>
+                            <div id="plugins-list" class="space-y-2"></div>
+                            <div id="plugins-reload-notice" class="hidden mt-3 flex items-center gap-2 px-3 py-2 border border-t-accent bg-t-accent/10 text-xs text-t-accent">
+                                <i class="ph ph-warning text-sm"></i>
+                                <span class="flex-1 font-pixel text-[10px]">reload required to apply changes</span>
+                                <button id="plugins-reload-btn" class="font-pixel text-[10px] underline hover:text-t-bright">reload now</button>
+                            </div>
+                        </div>
+                    </div>
                     <div id="settings-panel-account" class="hidden space-y-4">
                         <div>
                             <div class="font-pixel text-[9px] uppercase tracking-wider text-t-dim mb-2"><i class="ph ph-key text-xs"></i> vault key</div>
@@ -1826,7 +1867,7 @@ if (str_starts_with($route, '/api/')) {
                 <button data-md="hr" title="Divider" class="toolbar-btn"><i class="ph ph-minus text-sm"></i></button>
                 <div class="w-px h-4 bg-t-border mx-1"></div>
                 <button data-md="extract" title="Extract selection to new card" class="toolbar-btn"><i class="ph ph-scissors text-sm"></i></button>
-                <button data-md="asciiart" title="ASCII Canvas" class="toolbar-btn"><i class="ph ph-grid-four text-sm"></i></button>
+                <?= PluginManager::instance()->slot('md-toolbar') ?>
                 <div class="flex-1"></div>
                 <button id="toggle-lines" class="toolbar-btn flex items-center gap-1.5 px-2" title="line numbers"><i class="ph ph-hash text-sm"></i></button>
                 <button id="toggle-preview" class="toolbar-btn flex items-center gap-1.5 px-2"><i class="ph ph-eye text-sm"></i><span class="font-pixel text-[9px]">preview</span></button>
@@ -1843,51 +1884,14 @@ if (str_starts_with($route, '/api/')) {
         </div>
     </div>
 
-    <!-- ASCII Canvas Overlay -->
-    <div class="overlay fixed inset-0" id="ascii-canvas-overlay" style="z-index:80;">
-        <div class="ascii-canvas-modal bg-t-surface border border-t-border rounded-lg shadow-xl flex flex-col" style="width:90vw;max-width:960px;height:85vh;max-height:700px;margin:auto;position:absolute;inset:0;">
-            <!-- Toolbar -->
-            <div class="flex items-center gap-1 px-3 py-2 border-b border-t-border shrink-0 flex-wrap" id="ascii-canvas-toolbar">
-                <button data-tool="brush" class="toolbar-btn active" title="Brush (B)"><i class="ph ph-pencil-simple text-sm"></i></button>
-                <button data-tool="eraser" class="toolbar-btn" title="Eraser (E)"><i class="ph ph-eraser text-sm"></i></button>
-                <button data-tool="line" class="toolbar-btn" title="Line (L)"><i class="ph ph-line-segment text-sm"></i></button>
-                <button data-tool="rect" class="toolbar-btn" title="Rectangle (R)"><i class="ph ph-rectangle text-sm"></i></button>
-                <button data-tool="circle" class="toolbar-btn" title="Ellipse (O)"><i class="ph ph-circle text-sm"></i></button>
-                <button data-tool="fill" class="toolbar-btn" title="Fill (F)"><i class="ph ph-paint-bucket text-sm"></i></button>
-                <button data-tool="text" class="toolbar-btn" title="Text (T)"><i class="ph ph-text-t text-sm"></i></button>
-                <div class="w-px h-4 bg-t-border mx-1"></div>
-                <label class="flex items-center gap-1 text-t-muted text-xs">
-                    <span>Char:</span>
-                    <input id="ascii-char-input" type="text" value="#" maxlength="1" class="w-6 text-center bg-t-bg border border-t-border rounded text-t-text text-sm font-mono px-0 py-0">
-                </label>
-                <div class="w-px h-4 bg-t-border mx-1"></div>
-                <label class="flex items-center gap-1 text-t-muted text-xs">
-                    <span>W:</span>
-                    <input id="ascii-canvas-width" type="number" value="40" min="5" max="200" class="w-12 bg-t-bg border border-t-border rounded text-t-text text-xs text-center px-1 py-0">
-                </label>
-                <label class="flex items-center gap-1 text-t-muted text-xs">
-                    <span>H:</span>
-                    <input id="ascii-canvas-height" type="number" value="20" min="3" max="100" class="w-12 bg-t-bg border border-t-border rounded text-t-text text-xs text-center px-1 py-0">
-                </label>
-                <button id="ascii-canvas-resize" class="toolbar-btn text-xs" title="Resize"><i class="ph ph-arrows-out text-sm"></i></button>
-                <div class="w-px h-4 bg-t-border mx-1"></div>
-                <button id="ascii-canvas-clear" class="toolbar-btn text-xs" title="Clear"><i class="ph ph-trash text-sm"></i></button>
-                <div class="flex-1"></div>
-                <span id="ascii-canvas-coords" class="text-t-dim text-xs font-mono">1:1</span>
-            </div>
-            <!-- Char palette -->
-            <div id="ascii-char-palette" class="flex items-center gap-0.5 px-3 py-1.5 border-b border-t-border shrink-0 flex-wrap overflow-x-auto"></div>
-            <!-- Grid -->
-            <div class="flex-1 min-h-0 overflow-auto bg-t-bg p-2">
-                <pre id="ascii-canvas-grid" class="ascii-grid font-mono text-sm text-t-text select-none cursor-crosshair" style="line-height:1.35;letter-spacing:0;margin:0;"></pre>
-            </div>
-            <!-- Footer -->
-            <div class="flex items-center justify-end gap-2 px-3 py-2 border-t border-t-border shrink-0">
-                <button id="ascii-canvas-cancel" class="toolbar-btn text-xs px-3 py-1">Cancel</button>
-                <button id="ascii-canvas-ok" class="bg-t-accent text-t-bg text-xs font-bold px-4 py-1 rounded hover:opacity-90 cursor-pointer">Insert</button>
-            </div>
-        </div>
-    </div>
+    <!-- Plugin HTML fragments (overlays, modals, etc.) -->
+    <?= PluginManager::instance()->htmlFragments() ?>
+
+    <!-- Plugin API: must load BEFORE any ES module so window.hyprcrd exists -->
+    <script src="js/hyprcrd.js?v=<?= time() ?>"></script>
+
+    <!-- Plugin entry points (load before app.js so they self-register first) -->
+    <?= PluginManager::instance()->scriptTags() ?>
 
     <script type="module" src="js/app.js?v=<?= time() ?>"></script>
 </body>
diff --git a/public/js/app.js b/public/js/app.js
index dd4f892..577b3f0 100644
--- a/public/js/app.js
+++ b/public/js/app.js
@@ -17,6 +17,7 @@ import { openGallery, closeGallery } from './modules/gallery.js';
 import { refreshTasksView, openTasks, closeTasks } from './modules/tasks.js';
 import { openCalendar, closeCalendar, refreshCalendar } from './modules/calendar.js';
 import { startBackgroundSync, triggerSync, loadSettings as loadCaldavSettings, loadRelaySettings } from './modules/caldav.js';
+import { openPluginSettings } from './modules/plugin-settings.js';
 
 // ── Global API (for inline onclick handlers and cross-module calls) ──
 
@@ -28,6 +29,7 @@ window._closeTasks = closeTasks;
 window._renderBoard = renderBoard;
 window._openCalendar = openCalendar;
 window._triggerSync = triggerSync;
+window._openPluginSettings = openPluginSettings;
 window._loadCaldavSettings = loadCaldavSettings;
 window._loadRelaySettings = loadRelaySettings;
 window._renderTagBar = renderTagBar;
@@ -277,13 +279,4 @@ document.getElementById('quick-capture-input')?.addEventListener('keydown', asyn
 
 checkAuth();
 
-// ── Test runner (lazy-loaded, no cost in production) ──
-if (new URLSearchParams(location.search).has('test') || false) {
-    import('./test/tests.js');
-}
-document.addEventListener('keydown', e => {
-    if (e.ctrlKey && e.shiftKey && e.key === 'T') {
-        e.preventDefault();
-        import('./test/tests.js').then(() => import('./test/runner.js').then(m => m.open()));
-    }
-});
+// ── Test runner: now provided by the "tests" plugin (see public/plugins/tests/) ──
diff --git a/public/js/hyprcrd.js b/public/js/hyprcrd.js
new file mode 100644
index 0000000..c2fbc3f
--- /dev/null
+++ b/public/js/hyprcrd.js
@@ -0,0 +1,135 @@
+// ── hyprcrd Plugin API ──
+//
+// Loaded synchronously BEFORE any module script. Plugins and core both
+// register against window.hyprcrd. Plugins MUST NOT import from core
+// modules — use this global API instead so they remain decoupled.
+//
+// Available namespaces:
+//   hyprcrd.hooks      — generic event bus (on/emit)
+//   hyprcrd.editor     — toolbar command registry
+//   hyprcrd.markdown   — fenced block + post-processing registry
+//   hyprcrd.util       — DOM helpers exposed for plugin use
+//
+// Plugins are loaded as <script type="module"> tags after this script
+// but before app.js. They self-register on module evaluation; the core
+// then queries the registries when needed.
+
+(function () {
+    'use strict';
+
+    // ── Generic event bus ───────────────────────────────────────────
+    const hookListeners = Object.create(null);
+    const hooks = {
+        on(name, fn) {
+            if (typeof fn !== 'function') return;
+            (hookListeners[name] ||= []).push(fn);
+        },
+        off(name, fn) {
+            const arr = hookListeners[name];
+            if (!arr) return;
+            const idx = arr.indexOf(fn);
+            if (idx >= 0) arr.splice(idx, 1);
+        },
+        emit(name, data) {
+            const arr = hookListeners[name];
+            if (!arr) return data;
+            for (const fn of arr.slice()) {
+                try {
+                    const r = fn(data);
+                    if (r !== undefined) data = r;
+                } catch (err) {
+                    console.error(`[hyprcrd hook ${name}]`, err);
+                }
+            }
+            return data;
+        },
+    };
+
+    // ── Editor command registry ─────────────────────────────────────
+    // Toolbar buttons with `data-md="<name>"` dispatch to handlers
+    // registered here. Plugins inject buttons + register handlers.
+    const editorCommands = Object.create(null);
+    const editor = {
+        registerCommand(name, fn) {
+            if (typeof fn !== 'function') return;
+            editorCommands[name] = fn;
+        },
+        unregisterCommand(name) {
+            delete editorCommands[name];
+        },
+        getCommand(name) {
+            return editorCommands[name];
+        },
+        // Set by editor.js after init — gives plugins access to
+        // insertMd(before, after, placeholder) and the textarea body
+        // without forcing an import dependency.
+        api: null,
+    };
+
+    // ── Markdown fenced block registry ──────────────────────────────
+    // Each entry: { lang: string, handler: (content) => string }
+    // The handler receives the raw text inside ```<lang> ... ``` and
+    // must return safe HTML (it will pass through DOMPurify after).
+    const fencedBlocks = [];
+    // Pre/post processors run on the full source text, before/after
+    // marked.parse(). Useful for non-fenced syntax extensions.
+    const preProcessors = [];
+    const postProcessors = [];
+    const markdown = {
+        registerFencedBlock(lang, handler) {
+            if (typeof handler !== 'function') return;
+            fencedBlocks.push({ lang, handler });
+        },
+        getFencedBlocks() {
+            return fencedBlocks.slice();
+        },
+        registerPreProcessor(fn) {
+            if (typeof fn === 'function') preProcessors.push(fn);
+        },
+        getPreProcessors() {
+            return preProcessors.slice();
+        },
+        registerPostProcessor(fn) {
+            if (typeof fn === 'function') postProcessors.push(fn);
+        },
+        getPostProcessors() {
+            return postProcessors.slice();
+        },
+    };
+
+    // ── Util helpers (mirror of internal util.js) ───────────────────
+    const util = {
+        $(idOrSel) {
+            if (typeof idOrSel !== 'string') return null;
+            if (idOrSel.startsWith('#') || idOrSel.includes(' ') || idOrSel.includes('.') || idOrSel.includes('[')) {
+                return document.querySelector(idOrSel);
+            }
+            return document.getElementById(idOrSel);
+        },
+        $$(sel) {
+            return Array.from(document.querySelectorAll(sel));
+        },
+        esc(s) {
+            return String(s ?? '').replace(/[&<>"']/g, c => ({
+                '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;'
+            }[c]));
+        },
+    };
+
+    // ── Plugin metadata registry ────────────────────────────────────
+    // Plugins can register themselves here for introspection / debug.
+    const plugins = [];
+    const registerPlugin = (meta) => {
+        if (meta && meta.name) plugins.push(meta);
+    };
+
+    window.hyprcrd = {
+        hooks,
+        editor,
+        markdown,
+        util,
+        plugins,
+        registerPlugin,
+        version: '1.0',
+    };
+})();
diff --git a/public/js/modules/editor.js b/public/js/modules/editor.js
index baa8a2a..d3b9c0f 100644
--- a/public/js/modules/editor.js
+++ b/public/js/modules/editor.js
@@ -4,7 +4,6 @@ import { $, esc, api, escRe, getCsrf, fuzzyMatch } from './util.js';
 import { state, getChildren, CARD_COLORS } from './state.js';
 import { renderMd, addCodeCopyButtons, formatTodoItems } from './markdown.js';
 import { pushCardEdit, snapshotCard } from './undo.js';
-import { openCanvas } from './canvas.js';
 
 const modal = $('modal');
 const body = $('editor-body');
@@ -442,87 +441,72 @@ function insertMd(before, after = '', placeholder = '') {
     updatePreview();
 }
 
+// ── Built-in editor commands ──
+// All commands flow through the plugin command registry. Plugins can
+// register their own data-md="..." commands via window.hyprcrd.editor.
+const _hyprEd = (typeof window !== 'undefined' && window.hyprcrd?.editor) || null;
+const _registerCmd = (name, fn) => {
+    if (_hyprEd) _hyprEd.registerCommand(name, fn);
+};
+
+_registerCmd('heading', () => insertMd('## ', '', 'Heading'));
+_registerCmd('bold', () => insertMd('**', '**', 'bold'));
+_registerCmd('italic', () => insertMd('*', '*', 'italic'));
+_registerCmd('strikethrough', () => insertMd('~~', '~~', 'text'));
+_registerCmd('code', () => insertMd('`', '`', 'code'));
+_registerCmd('codeblock', () => insertMd('```\n', '\n```', 'code'));
+_registerCmd('ul', () => insertMd('- ', '', 'item'));
+_registerCmd('ol', () => insertMd('1. ', '', 'item'));
+_registerCmd('tree', () => insertMd('```tree\n- ', '\n  - child\n', 'parent'));
+_registerCmd('quote', () => insertMd('> ', '', 'quote'));
+_registerCmd('todo', () => {
+    const s = body.selectionStart, e = body.selectionEnd;
+    const sel = body.value.substring(s, e);
+    if (sel && sel.includes('\n') || (sel && /^[\s]*[-*+]\s/m.test(sel))) {
+        const lines = sel.split('\n');
+        const hasTodos = lines.some(l => /^\s*- \[[ x]\]/.test(l));
+        const converted = lines.map(l => {
+            const trimmed = l.trim();
+            if (!trimmed) return l;
+            if (hasTodos) return l.replace(/^(\s*)- \[[ x]\] /, '$1- ');
+            return l.replace(/^(\s*)(?:[-*+]|\d+\.)\s/, '$1').replace(/^(\s*)(.+)$/, '$1- [ ] $2');
+        }).join('\n');
+        body.setRangeText(converted, s, e, 'select');
+        body.selectionStart = s;
+        body.selectionEnd = s + converted.length;
+        updatePreview();
+    } else {
+        insertMd('- [ ] ', '', 'task');
+    }
+});
+_registerCmd('link', () => insertMd('[', '](url)', 'text'));
+_registerCmd('cardlink', () => { insertMd('[[', ']]', ''); showLinkAc(''); });
+_registerCmd('extract', async () => {
+    const sel = body.value.substring(body.selectionStart, body.selectionEnd);
+    if (!sel.trim()) return;
+    const title = sel.trim().split('\n')[0].replace(/^#+\s*/, '').replace(/^[-*]\s*/, '').trim();
+    await window._extractToCard(sel);
+    const link = `[[${title}]]`;
+    body.setRangeText(link, body.selectionStart, body.selectionEnd, 'end');
+    updatePreview();
+});
+_registerCmd('hr', () => insertMd('\n---\n'));
+
+// Expose editor API to plugins (textarea, insertMd, preview refresh)
+if (_hyprEd) {
+    _hyprEd.api = {
+        body,
+        insertMd,
+        updatePreview,
+    };
+}
+
+// Toolbar dispatch routes through the plugin registry
 $('md-toolbar')?.addEventListener('click', e => {
     const btn = e.target.closest('[data-md]');
     if (!btn) return;
-    const cmds = {
-        heading: () => insertMd('## ', '', 'Heading'), bold: () => insertMd('**', '**', 'bold'),
-        italic: () => insertMd('*', '*', 'italic'), strikethrough: () => insertMd('~~', '~~', 'text'),
-        code: () => insertMd('`', '`', 'code'), codeblock: () => insertMd('```\n', '\n```', 'code'),
-        ul: () => insertMd('- ', '', 'item'), ol: () => insertMd('1. ', '', 'item'),
-        tree: () => insertMd('```tree\n- ', '\n  - child\n', 'parent'),
-        quote: () => insertMd('> ', '', 'quote'),
-        todo: () => {
-            const s = body.selectionStart, e = body.selectionEnd;
-            const sel = body.value.substring(s, e);
-            if (sel && sel.includes('\n') || (sel && /^[\s]*[-*+]\s/m.test(sel))) {
-                // Multi-line or bullet list: convert each line
-                const lines = sel.split('\n');
-                const hasTodos = lines.some(l => /^\s*- \[[ x]\]/.test(l));
-                const converted = lines.map(l => {
-                    const trimmed = l.trim();
-                    if (!trimmed) return l;
-                    if (hasTodos) {
-                        // Toggle back: remove checkbox
-                        return l.replace(/^(\s*)- \[[ x]\] /, '$1- ');
-                    }
-                    // Add checkbox: strip existing bullet if present
-                    return l.replace(/^(\s*)(?:[-*+]|\d+\.)\s/, '$1').replace(/^(\s*)(.+)$/, '$1- [ ] $2');
-                }).join('\n');
-                body.setRangeText(converted, s, e, 'select');
-                body.selectionStart = s;
-                body.selectionEnd = s + converted.length;
-                updatePreview();
-            } else {
-                insertMd('- [ ] ', '', 'task');
-            }
-        },
-        link: () => insertMd('[', '](url)', 'text'),
-        cardlink: () => { insertMd('[[', ']]', ''); showLinkAc(''); },
-        extract: async () => {
-            const sel = body.value.substring(body.selectionStart, body.selectionEnd);
-            if (!sel.trim()) return;
-            const title = sel.trim().split('\n')[0].replace(/^#+\s*/, '').replace(/^[-*]\s*/, '').trim();
-            await window._extractToCard(sel);
-            // Replace selection with a card link
-            const link = `[[${title}]]`;
-            body.setRangeText(link, body.selectionStart, body.selectionEnd, 'end');
-            updatePreview();
-        },
-        hr: () => insertMd('\n---\n'),
-        asciiart: () => {
-            // Check if cursor is inside an existing ```ascii block to edit it
-            const val = body.value;
-            const pos = body.selectionStart;
-            const before = val.substring(0, pos);
-            const after = val.substring(pos);
-            const blockStart = before.lastIndexOf('```ascii\n');
-            const blockEndInBefore = blockStart >= 0 ? before.indexOf('\n```', blockStart + 9) : -1;
-            let existingText = null, replaceStart = 0, replaceEnd = 0;
-            if (blockStart >= 0 && blockEndInBefore < 0) {
-                // Cursor is inside a ```ascii block
-                const contentStart = blockStart + 9; // after "```ascii\n"
-                const endMark = val.indexOf('\n```', contentStart);
-                if (endMark >= 0) {
-                    existingText = val.substring(contentStart, endMark);
-                    replaceStart = blockStart;
-                    replaceEnd = endMark + 4;
-                }
-            }
-            openCanvas(text => {
-                const block = '```ascii\n' + text + '\n```';
-                if (existingText !== null) {
-                    body.setRangeText(block, replaceStart, replaceEnd, 'end');
-                } else {
-                    const s = body.selectionStart;
-                    const prefix = s > 0 && val[s - 1] !== '\n' ? '\n' : '';
-                    body.setRangeText(prefix + block + '\n', s, body.selectionEnd, 'end');
-                }
-                updatePreview();
-            }, existingText);
-        },
-    };
-    cmds[btn.dataset.md]?.();
+    const fn = _hyprEd?.getCommand(btn.dataset.md);
+    if (fn) fn();
 });
 
 const editorDivider = $('editor-divider');
diff --git a/public/js/modules/markdown.js b/public/js/modules/markdown.js
index afc80c4..50c7d6e 100644
--- a/public/js/modules/markdown.js
+++ b/public/js/modules/markdown.js
@@ -11,6 +11,32 @@ marked.use({ breaks: true, gfm: true, renderer: {
     }
 }});
 
+// ── Built-in fenced block handlers ──
+// Registered through the same plugin API so plugins and core use one path.
+if (typeof window !== 'undefined' && window.hyprcrd?.markdown) {
+    const md = window.hyprcrd.markdown;
+
+    // ```gallery — image grid
+    md.registerFencedBlock('gallery', (content, { esc: e }) => {
+        const imgs = [];
+        const imgRe = /!\[([^\]]*)\]\(([^)]+)\)/g;
+        let m;
+        while ((m = imgRe.exec(content)) !== null) imgs.push({ alt: m[1], src: m[2].split(/\s/)[0] });
+        if (!imgs.length) return '';
+        return '<div class="md-gallery">' + imgs.map(i =>
+            `<div class="md-gallery-item"><img src="${i.src}" alt="${e(i.alt)}" loading="lazy"></div>`
+        ).join('') + '</div>';
+    });
+
+    // ```tree / ```bullets — custom list rendering (handled via post-processor)
+    const listHandler = (kind) => (content, { normalizeListBlock: norm }) => {
+        const normalized = norm(content);
+        return `\n<!-- list:${kind} -->\n${normalized}\n`;
+    };
+    md.registerFencedBlock('tree', listHandler('tree'));
+    md.registerFencedBlock('bullets', listHandler('bullets'));
+}
+
 const purifyConfig = {
     ALLOWED_TAGS: ['h1','h2','h3','h4','h5','h6','p','br','hr','ul','ol','li','a','strong','em','del','code','pre','blockquote','table','thead','tbody','tr','th','td','img','input','span','div','audio','source'],
     ALLOWED_ATTR: ['href','src','alt','width','height','type','checked','disabled','class','style','data-card-id','title','controls','preload','target','rel','align'],
@@ -79,27 +105,32 @@ export function renderMd(src) {
             '</tbody></table>\n';
     });
 
+    // ── Fenced block registry ─────────────────────────────────────
+    // Apply all registered ```<lang> handlers (built-in + plugins).
+    // Plugins register via window.hyprcrd.markdown.registerFencedBlock().
+    const fencedBlocks = (typeof window !== 'undefined' && window.hyprcrd?.markdown?.getFencedBlocks)
+        ? window.hyprcrd.markdown.getFencedBlocks()
+        : [];
+    for (const { lang, handler } of fencedBlocks) {
+        // Escape regex metachars in lang (allow simple identifiers)
+        const safeLang = String(lang).replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+        const re = new RegExp('```' + safeLang + '\\s*\\n([\\s\\S]*?)(?:```|$)', 'g');
+        processed = processed.replace(re, (_, content) => {
+            try { return handler(content, { esc, normalizeListBlock }); }
+            catch (err) { console.error(`[markdown fenced ${lang}]`, err); return ''; }
+        });
+    }
+
+    // ── Plugin pre-processors ─────────────────────────────────────
+    const preProcessors = (typeof window !== 'undefined' && window.hyprcrd?.markdown?.getPreProcessors)
+        ? window.hyprcrd.markdown.getPreProcessors()
+        : [];
+    for (const fn of preProcessors) {
+        try { processed = fn(processed) ?? processed; }
+        catch (err) { console.error('[markdown pre]', err); }
+    }
+
     processed = processed
-        // ASCII canvas block: ```ascii
-        .replace(/```ascii\s*\n([\s\S]*?)(?:```|$)/g, (_, content) => {
-            return `<pre class="ascii-art">${esc(content.replace(/\s+$/, ''))}</pre>`;
-        })
-        // Gallery fenced block: ```gallery
-        .replace(/```gallery\s*\n([\s\S]*?)(?:```|$)/g, (_, content) => {
-            const imgs = [];
-            const imgRe = /!\[([^\]]*)\]\(([^)]+)\)/g;
-            let m;
-            while ((m = imgRe.exec(content)) !== null) imgs.push({ alt: m[1], src: m[2].split(/\s/)[0] });
-            if (!imgs.length) return '';
-            return '<div class="md-gallery">' + imgs.map(i =>
-                `<div class="md-gallery-item"><img src="${i.src}" alt="${esc(i.alt)}" loading="lazy"></div>`
-            ).join('') + '</div>';
-        })
-        // Custom fenced list blocks: ```tree / ```bullets with or without closing ```
-        .replace(/```(tree|bullets)\s*\n([\s\S]*?)(?:```|$)/g, (_, kind, content) => {
-            const normalized = normalizeListBlock(content);
-            return `\n<!-- list:${kind} -->\n${normalized}\n`;
-        })
         // Help parser: ensure a list can start after text without requiring manual blank line
         .replace(/([^\n])\n(?=(?: {0,3}[-*+]\s| {0,3}\d+\.\s))/g, '$1\n\n')
         // Preserve extra blank lines as <br> spacers (3+ newlines = 1+ extra blank lines)
@@ -124,6 +155,15 @@ export function renderMd(src) {
     html = html.replace(/<!--\s*list:tree\s*-->\s*<ul>/g, '<ul class="tree-list">');
     html = html.replace(/<!--\s*list:bullets\s*-->\s*<ul>/g, '<ul class="bullet-list">');
 
+    // ── Plugin post-processors (run on HTML, before sanitize) ──
+    const postProcessors = (typeof window !== 'undefined' && window.hyprcrd?.markdown?.getPostProcessors)
+        ? window.hyprcrd.markdown.getPostProcessors()
+        : [];
+    for (const fn of postProcessors) {
+        try { html = fn(html) ?? html; }
+        catch (err) { console.error('[markdown post]', err); }
+    }
+
     html = typeof DOMPurify !== 'undefined' ? DOMPurify.sanitize(html, purifyConfig) : html;
     return html;
 }
diff --git a/public/js/modules/plugin-settings.js b/public/js/modules/plugin-settings.js
new file mode 100644
index 0000000..9d2ec10
--- /dev/null
+++ b/public/js/modules/plugin-settings.js
@@ -0,0 +1,90 @@
+// ── Plugin Settings UI ──
+// Renders the list of installed plugins with on/off toggles in the
+// settings overlay. Disabled plugins are skipped at PHP render time;
+// toggling requires a reload to take effect (page must re-fetch the
+// new script/css/html tag set).
+
+import { $, esc, api } from './util.js';
+
+let pluginsCache = null;
+let dirtyAfterToggle = false;
+
+async function fetchPlugins() {
+    const res = await fetch('api/plugins');
+    if (!res.ok) throw new Error('failed to load plugins');
+    pluginsCache = await res.json();
+    return pluginsCache;
+}
+
+function render(list) {
+    const container = $('plugins-list');
+    if (!container) return;
+    if (!list.length) {
+        container.innerHTML = '<p class="text-xs text-t-dim italic">No plugins installed. Drop a plugin folder into <code>public/plugins/</code> to add one.</p>';
+        return;
+    }
+    container.innerHTML = list.map(p => `
+        <div class="flex items-start gap-3 px-3 py-2 border border-t-border bg-t-bg rounded-sm" data-plugin="${esc(p.name)}">
+            <div class="flex-1 min-w-0">
+                <div class="flex items-center gap-2">
+                    <span class="font-pixel text-[11px] text-t-bright">${esc(p.name)}</span>
+                    <span class="font-pixel text-[9px] text-t-dim">v${esc(p.version || '?')}</span>
+                    ${p.hasBackend ? '<span class="font-pixel text-[8px] px-1 py-0.5 border border-t-border text-t-muted uppercase">php</span>' : ''}
+                </div>
+                ${p.description ? `<div class="text-[10px] text-t-muted leading-snug mt-1">${esc(p.description)}</div>` : ''}
+            </div>
+            <label class="flex items-center cursor-pointer shrink-0 mt-0.5">
+                <input type="checkbox" class="plugin-toggle accent-t-accent w-4 h-4" ${p.enabled ? 'checked' : ''} data-name="${esc(p.name)}">
+            </label>
+        </div>
+    `).join('');
+
+    container.querySelectorAll('.plugin-toggle').forEach(input => {
+        input.addEventListener('change', onToggle);
+    });
+}
+
+async function onToggle(e) {
+    const input = e.currentTarget;
+    const name = input.dataset.name;
+    const enabled = input.checked;
+    input.disabled = true;
+    try {
+        const res = await api('api/plugins/toggle', {
+            method: 'POST',
+            body: { name, enabled },
+        });
+        if (res.error) throw new Error(res.error);
+        pluginsCache = res.plugins;
+        dirtyAfterToggle = true;
+        $('plugins-reload-notice')?.classList.remove('hidden');
+    } catch (err) {
+        // Revert UI on failure
+        input.checked = !enabled;
+        console.error('[plugins] toggle failed:', err);
+    } finally {
+        input.disabled = false;
+    }
+}
+
+export async function openPluginSettings() {
+    const container = $('plugins-list');
+    if (!container) return;
+    container.innerHTML = '<p class="text-xs text-t-dim italic">Loading...</p>';
+    if (!dirtyAfterToggle) {
+        $('plugins-reload-notice')?.classList.add('hidden');
+    }
+    try {
+        const list = await fetchPlugins();
+        render(list);
+    } catch (err) {
+        container.innerHTML = `<p class="text-xs text-t-danger">Failed to load plugins: ${esc(err.message)}</p>`;
+    }
+}
+
+// Wire reload button once at module load
+document.addEventListener('DOMContentLoaded', () => {
+    $('plugins-reload-btn')?.addEventListener('click', () => location.reload());
+}, { once: true });
+// In case DOMContentLoaded already fired (modules are deferred but safe to retry)
+$('plugins-reload-btn')?.addEventListener('click', () => location.reload());
diff --git a/public/js/modules/theme.js b/public/js/modules/theme.js
index 0ab4724..d11a29a 100644
--- a/public/js/modules/theme.js
+++ b/public/js/modules/theme.js
@@ -36,6 +36,7 @@ overlay?.querySelectorAll('.settings-tab').forEach(tab => {
         if (panel === 'relay') { window._loadRelaySettings?.(); }
         if (panel === 'notifications') renderNotifSettings();
         if (panel === 'behavior') initBehaviorSettings();
+        if (panel === 'plugins') window._openPluginSettings?.();
     });
 });
 
diff --git a/public/plugins/canvas/canvas.css b/public/plugins/canvas/canvas.css
new file mode 100644
index 0000000..3b7d23e
--- /dev/null
+++ b/public/plugins/canvas/canvas.css
@@ -0,0 +1,43 @@
+/* Canvas Plugin styles */
+#ascii-canvas-overlay { background: rgba(0,0,0,0.5); backdrop-filter: blur(2px); }
+.ascii-grid {
+    white-space: pre;
+    user-select: none;
+    -webkit-user-select: none;
+    display: inline-block;
+    width: max-content;
+}
+.ascii-cursor { background: var(--t-accent); color: var(--t-bg); }
+.ascii-char-btn {
+    font-family: var(--t-font-mono, monospace);
+    font-size: 13px;
+    width: 22px;
+    height: 22px;
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    border: 1px solid var(--t-border);
+    border-radius: 3px;
+    background: var(--t-bg);
+    color: var(--t-text);
+    cursor: pointer;
+    transition: all 0.1s;
+    padding: 0;
+    line-height: 1;
+}
+.ascii-char-btn:hover { background: var(--t-raised); color: var(--t-bright); }
+.ascii-char-btn.active {
+    background: var(--t-accent);
+    color: var(--t-bg);
+    border-color: var(--t-accent);
+}
+.ascii-char-group { display: inline-flex; gap: 2px; margin-right: 6px; }
+#ascii-canvas-toolbar .toolbar-btn.active { background: var(--t-accent); color: var(--t-bg); }
+
+/* Preview rendering of ```ascii blocks */
+.prose pre.ascii-art {
+    line-height: 1.35;
+    letter-spacing: 0;
+    white-space: pre;
+    font-size: 0.85em;
+}
diff --git a/public/plugins/canvas/canvas.html b/public/plugins/canvas/canvas.html
new file mode 100644
index 0000000..f676eb4
--- /dev/null
+++ b/public/plugins/canvas/canvas.html
@@ -0,0 +1,45 @@
+<!-- Canvas Plugin: ASCII art overlay -->
+<div class="overlay fixed inset-0" id="ascii-canvas-overlay" style="z-index:80;">
+    <div class="ascii-canvas-modal bg-t-surface border border-t-border rounded-lg shadow-xl flex flex-col" style="width:90vw;max-width:960px;height:85vh;max-height:700px;margin:auto;position:absolute;inset:0;">
+        <!-- Toolbar -->
+        <div class="flex items-center gap-1 px-3 py-2 border-b border-t-border shrink-0 flex-wrap" id="ascii-canvas-toolbar">
+            <button data-tool="brush" class="toolbar-btn active" title="Brush (B)"><i class="ph ph-pencil-simple text-sm"></i></button>
+            <button data-tool="eraser" class="toolbar-btn" title="Eraser (E)"><i class="ph ph-eraser text-sm"></i></button>
+            <button data-tool="line" class="toolbar-btn" title="Line (L)"><i class="ph ph-line-segment text-sm"></i></button>
+            <button data-tool="rect" class="toolbar-btn" title="Rectangle (R)"><i class="ph ph-rectangle text-sm"></i></button>
+            <button data-tool="circle" class="toolbar-btn" title="Ellipse (O)"><i class="ph ph-circle text-sm"></i></button>
+            <button data-tool="fill" class="toolbar-btn" title="Fill (F)"><i class="ph ph-paint-bucket text-sm"></i></button>
+            <button data-tool="text" class="toolbar-btn" title="Text (T)"><i class="ph ph-text-t text-sm"></i></button>
+            <div class="w-px h-4 bg-t-border mx-1"></div>
+            <label class="flex items-center gap-1 text-t-muted text-xs">
+                <span>Char:</span>
+                <input id="ascii-char-input" type="text" value="#" maxlength="1" class="w-6 text-center bg-t-bg border border-t-border rounded text-t-text text-sm font-mono px-0 py-0">
+            </label>
+            <div class="w-px h-4 bg-t-border mx-1"></div>
+            <label class="flex items-center gap-1 text-t-muted text-xs">
+                <span>W:</span>
+                <input id="ascii-canvas-width" type="number" value="40" min="5" max="200" class="w-12 bg-t-bg border border-t-border rounded text-t-text text-xs text-center px-1 py-0">
+            </label>
+            <label class="flex items-center gap-1 text-t-muted text-xs">
+                <span>H:</span>
+                <input id="ascii-canvas-height" type="number" value="20" min="3" max="100" class="w-12 bg-t-bg border border-t-border rounded text-t-text text-xs text-center px-1 py-0">
+            </label>
+            <button id="ascii-canvas-resize" class="toolbar-btn text-xs" title="Resize"><i class="ph ph-arrows-out text-sm"></i></button>
+            <div class="w-px h-4 bg-t-border mx-1"></div>
+            <button id="ascii-canvas-clear" class="toolbar-btn text-xs" title="Clear"><i class="ph ph-trash text-sm"></i></button>
+            <div class="flex-1"></div>
+            <span id="ascii-canvas-coords" class="text-t-dim text-xs font-mono">1:1</span>
+        </div>
+        <!-- Char palette -->
+        <div id="ascii-char-palette" class="flex items-center gap-0.5 px-3 py-1.5 border-b border-t-border shrink-0 flex-wrap overflow-x-auto"></div>
+        <!-- Grid -->
+        <div class="flex-1 min-h-0 overflow-auto bg-t-bg p-2">
+            <pre id="ascii-canvas-grid" class="ascii-grid font-mono text-sm text-t-text select-none cursor-crosshair" style="line-height:1.35;letter-spacing:0;margin:0;"></pre>
+        </div>
+        <!-- Footer -->
+        <div class="flex items-center justify-end gap-2 px-3 py-2 border-t border-t-border shrink-0">
+            <button id="ascii-canvas-cancel" class="toolbar-btn text-xs px-3 py-1">Cancel</button>
+            <button id="ascii-canvas-ok" class="bg-t-accent text-t-bg text-xs font-bold px-4 py-1 rounded hover:opacity-90 cursor-pointer">Insert</button>
+        </div>
+    </div>
+</div>
diff --git a/public/js/modules/canvas.js b/public/plugins/canvas/canvas.js
similarity index 83%
rename from public/js/modules/canvas.js
rename to public/plugins/canvas/canvas.js
index 3372ff1..7afd5ed 100644
--- a/public/js/modules/canvas.js
+++ b/public/plugins/canvas/canvas.js
@@ -1,6 +1,16 @@
-// ── ASCII Art Canvas ──
+// ── Canvas Plugin: ASCII Art Editor ──
+//
+// Self-registers via window.hyprcrd:
+//   - Markdown fenced block ```ascii``` → <pre class="ascii-art">
+//   - Editor toolbar button + "asciiart" command
+//   - Re-opens canvas to edit if cursor is inside an existing block
 
-import { $ } from './util.js';
+const hyprcrd = window.hyprcrd;
+if (!hyprcrd) {
+    throw new Error('[canvas plugin] window.hyprcrd not found — plugin API missing');
+}
+
+const $ = (id) => document.getElementById(id);
 
 const overlay = $('ascii-canvas-overlay');
 const grid = $('ascii-canvas-grid');
@@ -506,4 +516,73 @@ function init() {
 
 init();
 
-export { closeCanvas };
+// ── Plugin self-registration ──────────────────────────────────────
+
+// Register markdown fenced block: ```ascii``` → styled <pre>
+hyprcrd.markdown.registerFencedBlock('ascii', (content, { esc }) => {
+    return `<pre class="ascii-art">${esc(content.replace(/\s+$/, ''))}</pre>`;
+});
+
+// Register editor toolbar command "asciiart"
+hyprcrd.editor.registerCommand('asciiart', () => {
+    const ed = hyprcrd.editor.api;
+    if (!ed || !ed.body) return;
+    const body = ed.body;
+
+    // Detect if cursor is inside an existing ```ascii``` block (edit mode)
+    const val = body.value;
+    const pos = body.selectionStart;
+    const before = val.substring(0, pos);
+    const blockStart = before.lastIndexOf('```ascii\n');
+    const blockEndInBefore = blockStart >= 0 ? before.indexOf('\n```', blockStart + 9) : -1;
+    let existingText = null, replaceStart = 0, replaceEnd = 0;
+    if (blockStart >= 0 && blockEndInBefore < 0) {
+        const contentStart = blockStart + 9;
+        const endMark = val.indexOf('\n```', contentStart);
+        if (endMark >= 0) {
+            existingText = val.substring(contentStart, endMark);
+            replaceStart = blockStart;
+            replaceEnd = endMark + 4;
+        }
+    }
+
+    openCanvas(text => {
+        const block = '```ascii\n' + text + '\n```';
+        if (existingText !== null) {
+            body.setRangeText(block, replaceStart, replaceEnd, 'end');
+        } else {
+            const s = body.selectionStart;
+            const prefix = s > 0 && val[s - 1] !== '\n' ? '\n' : '';
+            body.setRangeText(prefix + block + '\n', s, body.selectionEnd, 'end');
+        }
+        ed.updatePreview?.();
+    }, existingText);
+});
+
+// Inject toolbar button into #md-toolbar (after the "extract" button if present)
+function injectToolbarButton() {
+    const toolbar = $('md-toolbar');
+    if (!toolbar) return;
+    if (toolbar.querySelector('[data-md="asciiart"]')) return; // already injected
+    const btn = document.createElement('button');
+    btn.setAttribute('data-md', 'asciiart');
+    btn.setAttribute('title', 'ASCII Canvas');
+    btn.className = 'toolbar-btn';
+    btn.innerHTML = '<i class="ph ph-grid-four text-sm"></i>';
+    // Insert before the right-side spacer (flex-1 div), or append at end
+    const spacer = toolbar.querySelector('.flex-1');
+    if (spacer) toolbar.insertBefore(btn, spacer);
+    else toolbar.appendChild(btn);
+}
+if (document.readyState === 'loading') {
+    document.addEventListener('DOMContentLoaded', injectToolbarButton);
+} else {
+    injectToolbarButton();
+}
+
+// Register plugin metadata for introspection
+hyprcrd.registerPlugin({
+    name: 'canvas',
+    version: '1.0.0',
+    description: 'ASCII art canvas editor',
+});
diff --git a/public/plugins/canvas/plugin.json b/public/plugins/canvas/plugin.json
new file mode 100644
index 0000000..c58b4eb
--- /dev/null
+++ b/public/plugins/canvas/plugin.json
@@ -0,0 +1,10 @@
+{
+    "name": "canvas",
+    "version": "1.0.0",
+    "description": "ASCII art canvas editor — draw with characters in a monospace grid and embed via ```ascii blocks.",
+    "frontend": {
+        "js":   ["canvas.js"],
+        "css":  ["canvas.css"],
+        "html": ["canvas.html"]
+    }
+}
diff --git a/public/plugins/tests/buckets.test.js b/public/plugins/tests/buckets.test.js
index 78bed26..9c9bd20 100644
--- a/public/plugins/tests/buckets.test.js
+++ b/public/plugins/tests/buckets.test.js
@@ -1,5 +1,5 @@
 import { describe, it, afterEach, expect, $, $$, click, sleep, closeAll, csrf } from './runner.js';
-import { state } from '../modules/state.js';
+import { state } from '../../js/modules/state.js';
 
 describe('Bucket Bar', () => {
     afterEach(() => closeAll());
diff --git a/public/plugins/tests/canvas.test.js b/public/plugins/tests/canvas.test.js
new file mode 100644
index 0000000..af65c7b
--- /dev/null
+++ b/public/plugins/tests/canvas.test.js
@@ -0,0 +1,377 @@
+import { describe, it, beforeEach, afterEach, expect, $, click, sleep, closeAll } from './runner.js';
+
+// ── Helpers ──
+
+async function openEditor() {
+    click('#add-btn');
+    await sleep(200);
+}
+
+async function openCanvas() {
+    await openEditor();
+    const btn = document.querySelector('[data-md="asciiart"]');
+    if (!btn) throw new Error('canvas toolbar button not found');
+    btn.click();
+    // openCanvas does layout in rAF
+    await sleep(100);
+}
+
+function closeCanvasIfOpen() {
+    const overlay = $('#ascii-canvas-overlay');
+    if (overlay?.classList.contains('open')) {
+        const cancel = $('#ascii-canvas-cancel');
+        cancel?.click();
+    }
+}
+
+function getGridText() {
+    return $('#ascii-canvas-grid')?.textContent || '';
+}
+
+function getGridLines() {
+    return getGridText().split('\n');
+}
+
+// Dispatch a mousedown at a logical (col, row) cell on the grid
+function clickCell(col, row) {
+    const grid = $('#ascii-canvas-grid');
+    const rect = grid.getBoundingClientRect();
+    const cols = parseInt($('#ascii-canvas-width').value);
+    const rows = parseInt($('#ascii-canvas-height').value);
+    const cellW = rect.width / cols;
+    const cellH = rect.height / rows;
+    const x = rect.left + cellW * col + cellW / 2;
+    const y = rect.top + cellH * row + cellH / 2;
+    grid.dispatchEvent(new MouseEvent('mousedown', { bubbles: true, button: 0, clientX: x, clientY: y }));
+    window.dispatchEvent(new MouseEvent('mouseup', { bubbles: true, button: 0, clientX: x, clientY: y }));
+}
+
+// ── Plugin Registration ──
+
+describe('Canvas Plugin: Registration', () => {
+    it('plugin is registered with hyprcrd', () => {
+        expect(window.hyprcrd).toExist();
+        const meta = window.hyprcrd.plugins.find(p => p.name === 'canvas');
+        expect(meta).toExist();
+    });
+
+    it('asciiart editor command is registered', () => {
+        expect(window.hyprcrd.editor.getCommand('asciiart')).toExist();
+    });
+
+    it('ascii fenced block handler is registered', () => {
+        const handlers = window.hyprcrd.markdown.getFencedBlocks();
+        const ascii = handlers.find(h => h.lang === 'ascii');
+        expect(ascii).toExist();
+    });
+
+    it('toolbar button is injected into md-toolbar', () => {
+        const btn = document.querySelector('#md-toolbar [data-md="asciiart"]');
+        expect(btn).toExist();
+    });
+});
+
+// ── Overlay Structure ──
+
+describe('Canvas Plugin: Overlay Structure', () => {
+    it('overlay element exists in DOM', () => {
+        expect($('#ascii-canvas-overlay')).toExist();
+    });
+
+    it('grid, toolbar, and inputs exist', () => {
+        expect($('#ascii-canvas-grid')).toExist();
+        expect($('#ascii-canvas-toolbar')).toExist();
+        expect($('#ascii-char-input')).toExist();
+        expect($('#ascii-canvas-width')).toExist();
+        expect($('#ascii-canvas-height')).toExist();
+    });
+
+    it('all 7 tool buttons exist', () => {
+        const tools = ['brush', 'eraser', 'line', 'rect', 'circle', 'fill', 'text'];
+        for (const t of tools) {
+            const btn = document.querySelector(`[data-tool="${t}"]`);
+            expect(btn).toExist();
+        }
+    });
+
+    it('action buttons exist (ok, cancel, clear, resize)', () => {
+        expect($('#ascii-canvas-ok')).toExist();
+        expect($('#ascii-canvas-cancel')).toExist();
+        expect($('#ascii-canvas-clear')).toExist();
+        expect($('#ascii-canvas-resize')).toExist();
+    });
+});
+
+// ── Open / Close ──
+
+describe('Canvas Plugin: Open & Close', () => {
+    afterEach(async () => {
+        closeCanvasIfOpen();
+        await closeAll();
+    });
+
+    it('overlay is hidden initially', () => {
+        const overlay = $('#ascii-canvas-overlay');
+        expect(overlay.classList.contains('open')).toBe(false);
+    });
+
+    it('opens via toolbar button', async () => {
+        await openCanvas();
+        expect($('#ascii-canvas-overlay').classList.contains('open')).toBe(true);
+    });
+
+    it('cancel button closes overlay', async () => {
+        await openCanvas();
+        click('#ascii-canvas-cancel');
+        await sleep(50);
+        expect($('#ascii-canvas-overlay').classList.contains('open')).toBe(false);
+    });
+
+    it('overlay is filled with character grid on open', async () => {
+        await openCanvas();
+        const lines = getGridLines();
+        const cols = parseInt($('#ascii-canvas-width').value);
+        const rows = parseInt($('#ascii-canvas-height').value);
+        expect(lines.length).toBe(rows);
+        expect(lines[0].length).toBe(cols);
+    });
+
+    it('palette is populated with character buttons', async () => {
+        await openCanvas();
+        const buttons = document.querySelectorAll('#ascii-char-palette .ascii-char-btn');
+        expect(buttons.length).toBeGreaterThan(10);
+    });
+});
+
+// ── Tool Selection ──
+
+describe('Canvas Plugin: Tool Selection', () => {
+    afterEach(async () => {
+        closeCanvasIfOpen();
+        await closeAll();
+    });
+
+    it('brush is the default active tool', async () => {
+        await openCanvas();
+        const brushBtn = document.querySelector('[data-tool="brush"]');
+        expect(brushBtn.classList.contains('active')).toBe(true);
+    });
+
+    it('clicking a tool button activates it and deactivates others', async () => {
+        await openCanvas();
+        click(document.querySelector('[data-tool="line"]'));
+        await sleep(20);
+        expect(document.querySelector('[data-tool="line"]').classList.contains('active')).toBe(true);
+        expect(document.querySelector('[data-tool="brush"]').classList.contains('active')).toBe(false);
+    });
+
+    it('keyboard shortcut switches tool', async () => {
+        await openCanvas();
+        const overlay = $('#ascii-canvas-overlay');
+        overlay.dispatchEvent(new KeyboardEvent('keydown', { key: 'r', bubbles: true }));
+        await sleep(20);
+        expect(document.querySelector('[data-tool="rect"]').classList.contains('active')).toBe(true);
+    });
+});
+
+// ── Drawing ──
+
+describe('Canvas Plugin: Drawing', () => {
+    afterEach(async () => {
+        closeCanvasIfOpen();
+        await closeAll();
+    });
+
+    it('brush click sets a character at the clicked cell', async () => {
+        await openCanvas();
+        // Use a known character
+        const charInput = $('#ascii-char-input');
+        charInput.value = 'X';
+        charInput.dispatchEvent(new Event('input', { bubbles: true }));
+        await sleep(20);
+
+        clickCell(5, 3);
+        await sleep(20);
+
+        const lines = getGridLines();
+        expect(lines[3][5]).toBe('X');
+    });
+
+    it('eraser replaces character with space', async () => {
+        await openCanvas();
+        // Draw first
+        const charInput = $('#ascii-char-input');
+        charInput.value = '#';
+        charInput.dispatchEvent(new Event('input', { bubbles: true }));
+        await sleep(20);
+        clickCell(2, 2);
+        await sleep(20);
+        expect(getGridLines()[2][2]).toBe('#');
+
+        // Switch to eraser and click same cell
+        click(document.querySelector('[data-tool="eraser"]'));
+        await sleep(20);
+        clickCell(2, 2);
+        await sleep(20);
+        expect(getGridLines()[2][2]).toBe(' ');
+    });
+
+    it('clear button empties the grid', async () => {
+        await openCanvas();
+        const charInput = $('#ascii-char-input');
+        charInput.value = '#';
+        charInput.dispatchEvent(new Event('input', { bubbles: true }));
+        await sleep(20);
+        clickCell(1, 1);
+        clickCell(2, 2);
+        clickCell(3, 3);
+        await sleep(20);
+
+        click('#ascii-canvas-clear');
+        await sleep(20);
+
+        const lines = getGridLines();
+        // All chars should be space
+        const allSpace = lines.every(l => /^ *$/.test(l));
+        expect(allSpace).toBe(true);
+    });
+});
+
+// ── Character Selection ──
+
+describe('Canvas Plugin: Character Selection', () => {
+    afterEach(async () => {
+        closeCanvasIfOpen();
+        await closeAll();
+    });
+
+    it('clicking palette button updates active char', async () => {
+        await openCanvas();
+        const targetBtn = document.querySelector('#ascii-char-palette .ascii-char-btn');
+        const ch = targetBtn.textContent;
+        click(targetBtn);
+        await sleep(20);
+
+        // Draw with that char
+        clickCell(0, 0);
+        await sleep(20);
+
+        const lines = getGridLines();
+        expect(lines[0][0]).toBe(ch);
+    });
+
+    it('typing in char input changes active character', async () => {
+        await openCanvas();
+        const charInput = $('#ascii-char-input');
+        charInput.value = '@';
+        charInput.dispatchEvent(new Event('input', { bubbles: true }));
+        await sleep(20);
+
+        clickCell(4, 4);
+        await sleep(20);
+
+        const lines = getGridLines();
+        expect(lines[4][4]).toBe('@');
+    });
+});
+
+// ── Insert into Editor ──
+
+describe('Canvas Plugin: Insert', () => {
+    afterEach(async () => {
+        closeCanvasIfOpen();
+        await closeAll();
+    });
+
+    it('OK button inserts ```ascii block into editor body', async () => {
+        await openCanvas();
+        const charInput = $('#ascii-char-input');
+        charInput.value = 'Z';
+        charInput.dispatchEvent(new Event('input', { bubbles: true }));
+        await sleep(20);
+
+        clickCell(0, 0);
+        clickCell(1, 0);
+        clickCell(2, 0);
+        await sleep(20);
+
+        click('#ascii-canvas-ok');
+        await sleep(50);
+
+        const body = $('#editor-body');
+        expect(body.value).toContain('```ascii');
+        expect(body.value).toContain('ZZZ');
+        expect(body.value).toContain('```\n');
+    });
+
+    it('cancel does NOT insert anything', async () => {
+        await openEditor();
+        const body = $('#editor-body');
+        const beforeLen = body.value.length;
+
+        const btn = document.querySelector('[data-md="asciiart"]');
+        btn.click();
+        await sleep(100);
+
+        const charInput = $('#ascii-char-input');
+        charInput.value = 'Q';
+        charInput.dispatchEvent(new Event('input', { bubbles: true }));
+        await sleep(20);
+        clickCell(0, 0);
+        await sleep(20);
+
+        click('#ascii-canvas-cancel');
+        await sleep(50);
+
+        expect(body.value.length).toBe(beforeLen);
+    });
+});
+
+// ── Edit existing block ──
+
+describe('Canvas Plugin: Edit Existing Block', () => {
+    afterEach(async () => {
+        closeCanvasIfOpen();
+        await closeAll();
+    });
+
+    it('cursor inside ```ascii block loads existing content', async () => {
+        await openEditor();
+        const body = $('#editor-body');
+        body.value = '```ascii\n###\n###\n```';
+        body.dispatchEvent(new Event('input', { bubbles: true }));
+        // Place cursor inside the block content
+        const insidePos = body.value.indexOf('###') + 1;
+        body.selectionStart = body.selectionEnd = insidePos;
+
+        const btn = document.querySelector('[data-md="asciiart"]');
+        btn.click();
+        await sleep(150);
+
+        const lines = getGridLines();
+        // First two lines should contain the existing # chars
+        expect(lines[0].startsWith('###')).toBe(true);
+        expect(lines[1].startsWith('###')).toBe(true);
+    });
+});
+
+// ── Markdown Rendering ──
+
+describe('Canvas Plugin: Markdown Rendering', () => {
+    it('```ascii fenced block renders as <pre class="ascii-art">', async () => {
+        // Use the registered handler directly via the registry
+        const handlers = window.hyprcrd.markdown.getFencedBlocks();
+        const ascii = handlers.find(h => h.lang === 'ascii');
+        expect(ascii).toExist();
+        const html = ascii.handler('###\n###\n###', { esc: window.hyprcrd.util.esc });
+        expect(html).toContain('<pre class="ascii-art">');
+        expect(html).toContain('###');
+    });
+
+    it('renderMd produces ascii-art pre when given an ```ascii block', async () => {
+        const { renderMd } = await import('../../js/modules/markdown.js');
+        const html = renderMd('```ascii\n***\n***\n```');
+        expect(html).toContain('ascii-art');
+        expect(html).toContain('***');
+    });
+});
diff --git a/public/plugins/tests/card-interactions.test.js b/public/plugins/tests/card-interactions.test.js
index 5e4fca7..452e78e 100644
--- a/public/plugins/tests/card-interactions.test.js
+++ b/public/plugins/tests/card-interactions.test.js
@@ -1,5 +1,5 @@
 import { describe, it, afterEach, expect, $, $$, click, rightClick, sleep, closeAll, csrf } from './runner.js';
-import { state } from '../modules/state.js';
+import { state } from '../../js/modules/state.js';
 
 describe('Card: Tag Operations', () => {
     afterEach(() => closeAll());
diff --git a/public/plugins/tests/datepicker.test.js b/public/plugins/tests/datepicker.test.js
index b454b1d..891ea8f 100644
--- a/public/plugins/tests/datepicker.test.js
+++ b/public/plugins/tests/datepicker.test.js
@@ -1,5 +1,5 @@
 import { describe, it, afterEach, expect, $, $$, click, sleep, closeAll } from './runner.js';
-import { showDialog } from '../modules/dialog.js';
+import { showDialog } from '../../js/modules/dialog.js';
 
 describe('Datepicker: Rendering', () => {
     afterEach(async () => {
diff --git a/public/plugins/tests/favorites.test.js b/public/plugins/tests/favorites.test.js
index 64b6a86..a2131ff 100644
--- a/public/plugins/tests/favorites.test.js
+++ b/public/plugins/tests/favorites.test.js
@@ -1,5 +1,5 @@
 import { describe, it, afterEach, expect, $, $$, click, sleep, closeAll, csrf } from './runner.js';
-import { state } from '../modules/state.js';
+import { state } from '../../js/modules/state.js';
 
 describe('Favorites Bucket', () => {
     afterEach(() => closeAll());
diff --git a/public/plugins/tests/filtering.test.js b/public/plugins/tests/filtering.test.js
index 959bdea..5166726 100644
--- a/public/plugins/tests/filtering.test.js
+++ b/public/plugins/tests/filtering.test.js
@@ -1,5 +1,5 @@
 import { describe, it, afterEach, expect, $, $$, click, sleep, closeAll, csrf } from './runner.js';
-import { state, parseTags, sortedCards } from '../modules/state.js';
+import { state, parseTags, sortedCards } from '../../js/modules/state.js';
 
 describe('Filtering: Tag AND Logic', () => {
     afterEach(async () => {
diff --git a/public/plugins/tests/image-fullscreen.test.js b/public/plugins/tests/image-fullscreen.test.js
index 40b4473..43ab2f4 100644
--- a/public/plugins/tests/image-fullscreen.test.js
+++ b/public/plugins/tests/image-fullscreen.test.js
@@ -30,7 +30,7 @@ describe('Image Fullscreen Viewer', () => {
 
         // Check that images in detail would get fullscreen handler
         // The overlay is created lazily, verify the create function structure
-        const { bindDetailImageFullscreen } = await import('../modules/detail.js');
+        const { bindDetailImageFullscreen } = await import('../../js/modules/detail.js');
         expect(typeof bindDetailImageFullscreen).toBe('function');
     });
 
diff --git a/public/plugins/tests/loader.js b/public/plugins/tests/loader.js
new file mode 100644
index 0000000..c94afba
--- /dev/null
+++ b/public/plugins/tests/loader.js
@@ -0,0 +1,31 @@
+// ── Tests Plugin: conditional loader ──
+//
+// The test runner is heavy (40+ test files), so we only load it when:
+//   - URL contains ?test query param  → auto-run
+//   - Ctrl+Shift+T pressed            → manual open
+//
+// Tests are completely optional — without this plugin the app has no
+// test runner code loaded at all.
+
+const hyprcrd = window.hyprcrd;
+
+// Auto-load if ?test in query string
+if (new URLSearchParams(location.search).has('test')) {
+    import('./tests.js');
+}
+
+// Keyboard shortcut: Ctrl+Shift+T → open runner
+document.addEventListener('keydown', e => {
+    if (e.ctrlKey && e.shiftKey && e.key === 'T') {
+        e.preventDefault();
+        import('./tests.js').then(() =>
+            import('./runner.js').then(m => m.open?.())
+        );
+    }
+});
+
+hyprcrd?.registerPlugin?.({
+    name: 'tests',
+    version: '1.0.0',
+    description: 'UI + state test runner',
+});
diff --git a/public/plugins/tests/markdown-edge.test.js b/public/plugins/tests/markdown-edge.test.js
index 3b170bf..2b93ed9 100644
--- a/public/plugins/tests/markdown-edge.test.js
+++ b/public/plugins/tests/markdown-edge.test.js
@@ -1,5 +1,5 @@
 import { describe, it, expect } from './runner.js';
-import { renderMd } from '../modules/markdown.js';
+import { renderMd } from '../../js/modules/markdown.js';
 
 describe('Markdown: Blank Lines', () => {
     it('image after blank lines renders', () => {
diff --git a/public/plugins/tests/markdown.test.js b/public/plugins/tests/markdown.test.js
index 87a64aa..b1f1787 100644
--- a/public/plugins/tests/markdown.test.js
+++ b/public/plugins/tests/markdown.test.js
@@ -1,6 +1,6 @@
 import { describe, it, expect } from './runner.js';
-import { renderMd, formatTodoItems, stripMd } from '../modules/markdown.js';
-import { state } from '../modules/state.js';
+import { renderMd, formatTodoItems, stripMd } from '../../js/modules/markdown.js';
+import { state } from '../../js/modules/state.js';
 
 describe('Markdown: Basic Rendering', () => {
     it('renders paragraph', () => {
diff --git a/public/plugins/tests/multiselect.test.js b/public/plugins/tests/multiselect.test.js
index 33482ea..b27f5a2 100644
--- a/public/plugins/tests/multiselect.test.js
+++ b/public/plugins/tests/multiselect.test.js
@@ -1,5 +1,5 @@
 import { describe, it, afterEach, expect, $, sleep, closeAll } from './runner.js';
-import { state } from '../modules/state.js';
+import { state } from '../../js/modules/state.js';
 
 describe('Multi-Select', () => {
     afterEach(() => closeAll());
diff --git a/public/plugins/tests/plugin.json b/public/plugins/tests/plugin.json
new file mode 100644
index 0000000..94fa8d6
--- /dev/null
+++ b/public/plugins/tests/plugin.json
@@ -0,0 +1,10 @@
+{
+    "name": "tests",
+    "version": "1.0.0",
+    "description": "UI + state test runner. Loads only when ?test query param is present or Ctrl+Shift+T is pressed.",
+    "frontend": {
+        "js":   ["loader.js"],
+        "css":  [],
+        "html": []
+    }
+}
diff --git a/public/plugins/tests/rrule.test.js b/public/plugins/tests/rrule.test.js
index 8f5929f..90378f6 100644
--- a/public/plugins/tests/rrule.test.js
+++ b/public/plugins/tests/rrule.test.js
@@ -1,5 +1,5 @@
 import { describe, it, expect } from './runner.js';
-import { state } from '../modules/state.js';
+import { state } from '../../js/modules/state.js';
 
 // RRULE is set by CalDAV sync, not via PATCH. Test the data model and existing cards.
 
diff --git a/public/plugins/tests/runner.js b/public/plugins/tests/runner.js
index 2cccded..4a7d3bf 100644
--- a/public/plugins/tests/runner.js
+++ b/public/plugins/tests/runner.js
@@ -4,8 +4,8 @@
 // Panel is hidden during test run so interactions are visible.
 // Backup is created before and auto-restored after every run.
 
-import { getCsrf } from '../modules/util.js';
-import { stopBackgroundSync, startBackgroundSync } from '../modules/caldav.js';
+import { getCsrf } from '../../js/modules/util.js';
+import { stopBackgroundSync, startBackgroundSync } from '../../js/modules/caldav.js';
 
 const suites = [];
 let currentSuite = null;
diff --git a/public/plugins/tests/settings.test.js b/public/plugins/tests/settings.test.js
index cf4fc8b..8931bf1 100644
--- a/public/plugins/tests/settings.test.js
+++ b/public/plugins/tests/settings.test.js
@@ -9,12 +9,12 @@ describe('Settings: Open/Close', () => {
         expect($('#settings-overlay')).toBeVisible();
     });
 
-    it('has all 7 tabs', async () => {
+    it('has all 8 tabs', async () => {
         click('#settings-btn');
         await sleep(100);
         const names = $$('.settings-tab').map(t => t.dataset.tab);
-        expect(names.length).toBe(7);
-        for (const tab of ['branding', 'account', 'theme', 'caldav', 'relay', 'behavior', 'notifications']) {
+        expect(names.length).toBe(8);
+        for (const tab of ['branding', 'account', 'theme', 'caldav', 'relay', 'behavior', 'notifications', 'plugins']) {
             expect(names).toContain(tab);
         }
     });
diff --git a/public/plugins/tests/sorting.test.js b/public/plugins/tests/sorting.test.js
index a464a50..9f43cf8 100644
--- a/public/plugins/tests/sorting.test.js
+++ b/public/plugins/tests/sorting.test.js
@@ -1,5 +1,5 @@
 import { describe, it, expect, csrf } from './runner.js';
-import { state, sortedCards } from '../modules/state.js';
+import { state, sortedCards } from '../../js/modules/state.js';
 
 describe('Sorting: All Modes', () => {
     it('manual sort by position', () => {
diff --git a/public/plugins/tests/state-functions.test.js b/public/plugins/tests/state-functions.test.js
index 02a424e..e4f9435 100644
--- a/public/plugins/tests/state-functions.test.js
+++ b/public/plugins/tests/state-functions.test.js
@@ -1,5 +1,5 @@
 import { describe, it, expect } from './runner.js';
-import { state, parseTags, sortedCards, getChildren, getGroupCards, getRecent, markRecent, getFavorites, toggleFavorite, isFavorite } from '../modules/state.js';
+import { state, parseTags, sortedCards, getChildren, getGroupCards, getRecent, markRecent, getFavorites, toggleFavorite, isFavorite } from '../../js/modules/state.js';
 
 describe('State: parseTags', () => {
     it('splits comma-separated tags', () => {
diff --git a/public/plugins/tests/tests.js b/public/plugins/tests/tests.js
index 93fb500..01fa474 100644
--- a/public/plugins/tests/tests.js
+++ b/public/plugins/tests/tests.js
@@ -29,6 +29,7 @@ import './editor-features.test.js';
 import './editor-save.test.js';
 import './editor-toolbar.test.js';
 import './line-numbers.test.js';
+import './canvas.test.js';
 import './snippets.test.js';
 import './image-fullscreen.test.js';
 import './markdown.test.js';
diff --git a/public/plugins/tests/toolbar.test.js b/public/plugins/tests/toolbar.test.js
index 0cb908d..1ff7c44 100644
--- a/public/plugins/tests/toolbar.test.js
+++ b/public/plugins/tests/toolbar.test.js
@@ -1,5 +1,5 @@
 import { describe, it, afterEach, expect, $, click, sleep, closeAll } from './runner.js';
-import { state } from '../modules/state.js';
+import { state } from '../../js/modules/state.js';
 
 describe('Toolbar: Filter Toggles', () => {
     afterEach(() => closeAll());
diff --git a/public/plugins/tests/undo.test.js b/public/plugins/tests/undo.test.js
index 587842a..80c081d 100644
--- a/public/plugins/tests/undo.test.js
+++ b/public/plugins/tests/undo.test.js
@@ -204,7 +204,7 @@ describe('Undo: Card Delete', () => {
         // The child might be inside a group view — let's just test via the undo module directly
 
         // Import undo and test directly
-        const { pushCardDelete, snapshotCard, undo, canUndo } = await import('../modules/undo.js');
+        const { pushCardDelete, snapshotCard, undo, canUndo } = await import('../../js/modules/undo.js');
         const snap = { ...child, parent_id: parent.id };
         pushCardDelete('test-del', snap);
         await fetch(`api/cards/${child.id}`, { method: 'DELETE', headers: { 'X-CSRF-Token': csrf() } });
@@ -317,7 +317,7 @@ describe('Undo: Multiple Undos', () => {
 
 describe('Undo: No-Op When Empty', () => {
     it('Ctrl+Z with empty stack does nothing', async () => {
-        const { canUndo } = await import('../modules/undo.js');
+        const { canUndo } = await import('../../js/modules/undo.js');
         // Clear stack by undoing everything
         while (canUndo()) {
             ctrlZ();
diff --git a/src/PluginManager.php b/src/PluginManager.php
new file mode 100644
index 0000000..ebb878a
--- /dev/null
+++ b/src/PluginManager.php
@@ -0,0 +1,169 @@
+<?php
+
+/**
+ * PluginManager — Plugin discovery, loading, and asset rendering.
+ *
+ * Plugins live in /public/plugins/<name>/ and must have a plugin.json manifest:
+ *   {
+ *     "name": "canvas",
+ *     "version": "1.0.0",
+ *     "description": "ASCII art canvas editor",
+ *     "frontend": {
+ *       "js":   ["canvas.js"],
+ *       "css":  ["canvas.css"],
+ *       "html": ["canvas.html"]
+ *     },
+ *     "backend": "backend.php"   // optional
+ *   }
+ *
+ * Plugins are entirely optional — the core works fine without any.
+ */
+class PluginManager {
+    private array $plugins = [];
+    private array $slots = [];
+    private array $disabled = [];        // names of plugins the user has disabled
+    private ?string $stateFile = null;   // path to plugins.json
+    private static ?PluginManager $instance = null;
+
+    public static function instance(): self {
+        if (self::$instance === null) self::$instance = new self();
+        return self::$instance;
+    }
+
+    /** Scan a directory for plugins. Each subdirectory with a plugin.json is registered. */
+    public function scan(string $dir): void {
+        if (!is_dir($dir)) return;
+        $entries = @scandir($dir);
+        if (!$entries) return;
+        sort($entries);
+        foreach ($entries as $entry) {
+            if ($entry === '.' || $entry === '..') continue;
+            $pluginDir = $dir . '/' . $entry;
+            if (!is_dir($pluginDir)) continue;
+            $manifestPath = $pluginDir . '/plugin.json';
+            if (!file_exists($manifestPath)) continue;
+            $raw = @file_get_contents($manifestPath);
+            $manifest = $raw ? json_decode($raw, true) : null;
+            if (!is_array($manifest)) continue;
+            $name = $manifest['name'] ?? $entry;
+            $this->plugins[$name] = [
+                'dir' => $pluginDir,
+                'slug' => $entry,
+                'manifest' => $manifest,
+            ];
+        }
+    }
+
+    /** After scan() and loadDisabled(), require_once the backend.php of every ENABLED plugin. */
+    public function loadBackends(): void {
+        foreach ($this->plugins as $name => $p) {
+            if (!$this->isEnabled($name)) continue;
+            $backend = $p['manifest']['backend'] ?? null;
+            if (!$backend) continue;
+            $backendPath = $p['dir'] . '/' . $backend;
+            if (file_exists($backendPath)) require_once $backendPath;
+        }
+    }
+
+    public function plugins(): array {
+        return $this->plugins;
+    }
+
+    /** Load the disabled-plugins state file. Creates it lazily on first write. */
+    public function loadDisabled(string $stateFile): void {
+        $this->stateFile = $stateFile;
+        if (!file_exists($stateFile)) { $this->disabled = []; return; }
+        $raw = @file_get_contents($stateFile);
+        if (!$raw) { $this->disabled = []; return; }
+        $data = json_decode($raw, true);
+        $list = is_array($data) ? ($data['disabled'] ?? []) : [];
+        $this->disabled = array_values(array_filter($list, 'is_string'));
+    }
+
+    /** Persist the disabled list to the state file. Returns true on success. */
+    public function setDisabled(array $names): bool {
+        if ($this->stateFile === null) return false;
+        $clean = array_values(array_unique(array_filter($names, 'is_string')));
+        $this->disabled = $clean;
+        $dir = dirname($this->stateFile);
+        if (!is_dir($dir)) @mkdir($dir, 0755, true);
+        $payload = json_encode(['disabled' => $clean], JSON_PRETTY_PRINT);
+        return @file_put_contents($this->stateFile, $payload) !== false;
+    }
+
+    public function isEnabled(string $name): bool {
+        return !in_array($name, $this->disabled, true);
+    }
+
+    public function disabledList(): array {
+        return $this->disabled;
+    }
+
+    /** Public-friendly plugin list for the API: [{name, version, description, enabled}]. */
+    public function pluginsForApi(): array {
+        $out = [];
+        foreach ($this->plugins as $name => $p) {
+            $m = $p['manifest'];
+            $out[] = [
+                'name' => $name,
+                'version' => $m['version'] ?? '',
+                'description' => $m['description'] ?? '',
+                'enabled' => $this->isEnabled($name),
+                'hasBackend' => !empty($m['backend']),
+            ];
+        }
+        return $out;
+    }
+
+    /** Append HTML content to a named slot. Backend plugins use this. */
+    public function addToSlot(string $slot, string $html): void {
+        $this->slots[$slot][] = $html;
+    }
+
+    /** Render a slot's accumulated HTML. */
+    public function slot(string $slot): string {
+        return implode("\n", $this->slots[$slot] ?? []);
+    }
+
+    /** Render <link> tags for enabled plugin CSS files. */
+    public function cssLinks(string $baseUrl = 'plugins'): string {
+        $out = [];
+        foreach ($this->plugins as $name => $p) {
+            if (!$this->isEnabled($name)) continue;
+            $cssList = $p['manifest']['frontend']['css'] ?? [];
+            foreach ($cssList as $css) {
+                $out[] = '<link rel="stylesheet" href="' . $baseUrl . '/' . $p['slug'] . '/' . $css . '?v=' . time() . '">';
+            }
+        }
+        return implode("\n    ", $out);
+    }
+
+    /** Render inlined HTML fragments from enabled plugins (for overlays etc.). */
+    public function htmlFragments(): string {
+        $out = [];
+        foreach ($this->plugins as $name => $p) {
+            if (!$this->isEnabled($name)) continue;
+            $htmlList = $p['manifest']['frontend']['html'] ?? [];
+            foreach ($htmlList as $htmlFile) {
+                $path = $p['dir'] . '/' . $htmlFile;
+                if (file_exists($path)) {
+                    $out[] = "<!-- plugin:{$p['slug']}:{$htmlFile} -->\n" . file_get_contents($path);
+                }
+            }
+        }
+        return implode("\n", $out);
+    }
+
+    /** Render <script type="module"> tags for enabled plugin JS entry points. */
+    public function scriptTags(string $baseUrl = 'plugins'): string {
+        $out = [];
+        foreach ($this->plugins as $name => $p) {
+            if (!$this->isEnabled($name)) continue;
+            $jsList = $p['manifest']['frontend']['js'] ?? [];
+            foreach ($jsList as $js) {
+                $out[] = '<script type="module" src="' . $baseUrl . '/' . $p['slug'] . '/' . $js . '?v=' . time() . '"></script>';
+            }
+        }
+        return implode("\n    ", $out);
+    }
+}
diff --git a/src/bootstrap.php b/src/bootstrap.php
index 79d644e..e21fe80 100644
--- a/src/bootstrap.php
+++ b/src/bootstrap.php
@@ -8,6 +8,7 @@ if (function_exists('opcache_invalidate')) {
 
 require_once $configPath;
 require_once __DIR__ . '/Database.php';
+require_once __DIR__ . '/PluginManager.php';
 
 // Ensure data directory is writable
 $dataDir = dirname(DB_PATH);
@@ -16,3 +17,9 @@ if (!is_writable($dataDir) && is_dir($dataDir)) {
     echo 'Data directory is not writable';
     exit(1);
 }
+
+// Discover plugins (each subdir of public/plugins/ with a plugin.json)
+$pluginManager = PluginManager::instance();
+$pluginManager->scan(__DIR__ . '/../public/plugins');
+$pluginManager->loadDisabled(dirname(DB_PATH) . '/plugins.json');
+$pluginManager->loadBackends(); // require_once enabled backend.php files