diff --git a/app/[locale]/page.tsx b/app/[locale]/page.tsx
index def07bca..fa929acf 100644
--- a/app/[locale]/page.tsx
+++ b/app/[locale]/page.tsx
@@ -45,6 +45,8 @@ import { Search, Filter, ChevronDown, X, Paperclip, Star, Mail, MailOpen, Rotate
 import { ResizeHandle } from "@/components/layout/resize-handle";
 import { Button } from "@/components/ui/button";
 import { useConfig } from "@/hooks/use-config";
+import { usePluginStore } from "@/stores/plugin-store";
+
 
 export default function Home() {
   const t = useTranslations();
@@ -266,6 +268,11 @@ export default function Home() {
     });
   }, [checkAuth]);
 
+  // Initialize plugins on mount (re-activates enabled plugins after refresh)
+  useEffect(() => {
+    usePluginStore.getState().initializePlugins();
+  }, []);
+
   // Hydrate persisted column widths from localStorage
   useEffect(() => {
     try {
@@ -1463,12 +1470,12 @@ export default function Home() {
           {/* Email Viewer / Composer - full screen on mobile, flex on tablet/desktop */}
           <div
             className={cn(
-              "flex flex-col h-full bg-background",
+              "flex flex-col h-full bg-background flex-1 min-w-0",
               // Mobile: full screen overlay when active
               "max-md:fixed max-md:inset-0 max-md:z-30",
               isMobile && activeView !== "viewer" && "max-md:hidden",
-              // Tablet/Desktop: flex grow, min-w-0 allows truncation of long subjects
-              "md:flex-1 md:min-w-0 md:relative"
+              // Tablet/Desktop: relative
+              "md:relative"
             )}
           >
             {/* Inline Composer - shown in viewer pane */}
diff --git a/components/email/email-viewer.tsx b/components/email/email-viewer.tsx
index 75be5bd6..4a14d1a0 100644
--- a/components/email/email-viewer.tsx
+++ b/components/email/email-viewer.tsx
@@ -57,6 +57,7 @@ import {
   MapPin,
   StickyNote,
   PanelRightClose,
+  PanelRightOpen,
   Send,
   FolderInput,
   Inbox,
@@ -96,6 +97,8 @@ import { parseTnef, isTnefAttachment } from "@/lib/tnef";
 import { debug } from "@/lib/debug";
 import type { TnefAttachment } from "@/lib/tnef";
 import { PluginSlot } from "@/components/plugins/plugin-slot";
+import { usePluginStore } from "@/stores/plugin-store";
+import { ResizeHandle } from "@/components/layout/resize-handle";
 
 interface EmailViewerProps {
   email: Email | null;
@@ -948,6 +951,13 @@ export function EmailViewer({
   const [embeddedEmailAttachments, setEmbeddedEmailAttachments] = useState<PostalMimeAttachment[]>([]);
   const [embeddedEmailUnwrapped, setEmbeddedEmailUnwrapped] = useState(false);
 
+  // Plugin detail sidebar state
+  const detailSlots = usePluginStore(s => s.slots['email-detail-sidebar']);
+  const hasDetailSidebar = detailSlots && detailSlots.length > 0;
+  const [detailSidebarCollapsed, setDetailSidebarCollapsed] = useState(false);
+  const [detailSidebarWidth, setDetailSidebarWidth] = useState(280);
+  const detailSidebarWidthRef = useRef(280);
+
   // Ensure S/MIME key records are loaded from IndexedDB
   useLayoutEffect(() => {
     smimeStore.load();
@@ -4445,7 +4455,7 @@ export function EmailViewer({
 
         <div>
 
-          <PluginSlot name="email-banner" />
+          <PluginSlot name="email-banner" extraProps={{ email }} />
 
           {/* Email Body */}
           <div className="email-content-wrapper overflow-x-auto">
@@ -4691,6 +4701,58 @@ export function EmailViewer({
       </nav>
     )}
 
+    {/* Plugin Detail Sidebar - resizable, collapsible */}
+    {hasDetailSidebar && !isMobile && (
+      <>
+        {/* Collapse toggle when sidebar is collapsed */}
+        {detailSidebarCollapsed && (
+          <div className="flex flex-col items-center border-l border-border bg-background">
+            <Button
+              variant="ghost"
+              size="icon"
+              onClick={() => setDetailSidebarCollapsed(false)}
+              className="h-8 w-8 m-1"
+              aria-label="Expand panel"
+            >
+              <PanelRightOpen className="w-4 h-4" />
+            </Button>
+          </div>
+        )}
+        {!detailSidebarCollapsed && (
+          <>
+            <ResizeHandle
+              onResizeStart={() => { detailSidebarWidthRef.current = detailSidebarWidth; }}
+              onResize={(delta) => {
+                const newWidth = Math.max(200, Math.min(500, detailSidebarWidthRef.current - delta));
+                setDetailSidebarWidth(newWidth);
+              }}
+              onResizeEnd={() => { detailSidebarWidthRef.current = detailSidebarWidth; }}
+              onDoubleClick={() => setDetailSidebarWidth(280)}
+            />
+            <div
+              className="flex flex-col h-full border-l border-border bg-background overflow-hidden"
+              style={{ width: detailSidebarWidth, minWidth: detailSidebarWidth }}
+            >
+              <div className="flex items-center justify-end px-1 py-1 border-b border-border shrink-0">
+                <Button
+                  variant="ghost"
+                  size="icon"
+                  onClick={() => setDetailSidebarCollapsed(true)}
+                  className="h-7 w-7"
+                  aria-label="Collapse panel"
+                >
+                  <PanelRightClose className="w-4 h-4" />
+                </Button>
+              </div>
+              <div className="flex-1 overflow-y-auto">
+                <PluginSlot name="email-detail-sidebar" extraProps={{ email }} />
+              </div>
+            </div>
+          </>
+        )}
+      </>
+    )}
+
     {/* Contact Detail Sidebar - desktop only */}
     {contactSidebarEmail && !isMobileDevice && (
       <ContactSidebarPanel
diff --git a/components/layout/sidebar.tsx b/components/layout/sidebar.tsx
index 51afb2af..71b537fe 100644
--- a/components/layout/sidebar.tsx
+++ b/components/layout/sidebar.tsx
@@ -657,9 +657,9 @@ export function Sidebar({
             )}
           </>
         )}
-      </div>
 
-      <PluginSlot name="sidebar-widget" />
+        {!isCollapsed && <PluginSlot name="sidebar-widget" className="border-t border-border" />}
+      </div>
 
       {/* Compose Button */}
       <div className={cn("border-t border-border", isCollapsed ? "flex justify-center py-3" : "px-3 py-3")}>
diff --git a/lib/__tests__/plugin-store.test.ts b/lib/__tests__/plugin-store.test.ts
index dbbbc378..3f1f9301 100644
--- a/lib/__tests__/plugin-store.test.ts
+++ b/lib/__tests__/plugin-store.test.ts
@@ -48,6 +48,7 @@ function resetStore() {
       'email-footer': [],
       'composer-toolbar': [],
       'sidebar-widget': [],
+      'email-detail-sidebar': [],
       'settings-section': [],
       'context-menu-email': [],
       'navigation-rail-bottom': [],
diff --git a/lib/plugin-api.ts b/lib/plugin-api.ts
index cc02b017..9831d61d 100644
--- a/lib/plugin-api.ts
+++ b/lib/plugin-api.ts
@@ -113,6 +113,7 @@ export interface PluginAPI {
     registerSettingsSection: (section: SettingsSection) => Disposable;
     registerComposerAction: (action: ComposerAction) => Disposable;
     registerSidebarWidget: (widget: SidebarWidget) => Disposable;
+    registerDetailSidebar: (widget: SidebarWidget) => Disposable;
     registerContextMenuItem: (item: ContextMenuItem) => Disposable;
     registerNavigationRailItem: (component: React.ComponentType) => Disposable;
   };
@@ -556,6 +557,11 @@ export function createPluginAPI(plugin: InstalledPlugin): PluginAPI {
         return registerSlot(plugin.id, 'sidebar-widget', widget.render as React.ComponentType<Record<string, unknown>>, widget.order ?? 100);
       },
 
+      registerDetailSidebar: (widget: SidebarWidget) => {
+        requirePermission(plugin, 'ui:sidebar-widget');
+        return registerSlot(plugin.id, 'email-detail-sidebar', widget.render as React.ComponentType<Record<string, unknown>>, widget.order ?? 100);
+      },
+
       registerContextMenuItem: (item: ContextMenuItem) => {
         requirePermission(plugin, 'ui:context-menu');
         const Component = () => {
diff --git a/lib/plugin-loader.ts b/lib/plugin-loader.ts
index 98873026..9dc835b3 100644
--- a/lib/plugin-loader.ts
+++ b/lib/plugin-loader.ts
@@ -49,6 +49,9 @@ export async function loadPlugin(plugin: InstalledPlugin): Promise<void> {
     return;
   }
 
+  // Ensure React/ReactDOM are exposed before any plugin module evaluates
+  exposePluginExternals();
+
   try {
     // 1. Read bundle from IndexedDB
     const code = await pluginStorage.getCode(plugin.id);
diff --git a/lib/plugin-types.ts b/lib/plugin-types.ts
index d679f898..05c8a6a6 100644
--- a/lib/plugin-types.ts
+++ b/lib/plugin-types.ts
@@ -85,6 +85,7 @@ export type SlotName =
   | 'email-footer'
   | 'composer-toolbar'
   | 'sidebar-widget'
+  | 'email-detail-sidebar'
   | 'settings-section'
   | 'context-menu-email'
   | 'navigation-rail-bottom';
diff --git a/proxy.ts b/proxy.ts
index bbf5c4f9..01a00312 100644
--- a/proxy.ts
+++ b/proxy.ts
@@ -9,8 +9,8 @@ export function proxy(request: NextRequest) {
   const isDev = process.env.NODE_ENV === "development";
 
   const scriptSrc = isDev
-    ? `'self' 'nonce-${nonce}' 'unsafe-eval'`
-    : `'self' 'nonce-${nonce}'`;
+    ? `'self' 'nonce-${nonce}' 'unsafe-eval' blob:`
+    : `'self' 'nonce-${nonce}' blob:`;
 
   const connectSrc = isDev ? `'self' https: ws: wss:` : `'self' https:`;
 
diff --git a/stores/email-store.ts b/stores/email-store.ts
index 675e126b..d347c6c4 100644
--- a/stores/email-store.ts
+++ b/stores/email-store.ts
@@ -4,6 +4,7 @@ import type { IJMAPClient } from "@/lib/jmap/client-interface";
 import { useSettingsStore } from "@/stores/settings-store";
 import { useCalendarStore } from "@/stores/calendar-store";
 import { SearchFilters, DEFAULT_SEARCH_FILTERS, buildJMAPFilter, isFilterEmpty } from "@/lib/jmap/search-utils";
+import { emailHooks } from "@/lib/plugin-hooks";
 
 interface EmailStore {
   emails: Email[];
@@ -159,7 +160,16 @@ export const useEmailStore = create<EmailStore>((set, get) => ({
 
   setEmails: (emails) => set({ emails }),
   setMailboxes: (mailboxes) => set({ mailboxes }),
-  selectEmail: (email) => set({ selectedEmail: email, lastSelectedEmailId: email?.id ?? get().lastSelectedEmailId }),
+  selectEmail: (email) => {
+    const prev = get().selectedEmail;
+    set({ selectedEmail: email, lastSelectedEmailId: email?.id ?? get().lastSelectedEmailId });
+    if (prev && (!email || email.id !== prev.id)) {
+      emailHooks.onEmailClose.emitSync(prev);
+    }
+    if (email && (!prev || email.id !== prev.id)) {
+      emailHooks.onEmailOpen.emitSync(email);
+    }
+  },
   selectKeyword: (keyword) => set({
     selectedKeyword: keyword,
     selectedEmail: null,
diff --git a/stores/plugin-store.ts b/stores/plugin-store.ts
index 86bd4e60..16d2c5cc 100644
--- a/stores/plugin-store.ts
+++ b/stores/plugin-store.ts
@@ -19,7 +19,7 @@ import { removeAllPluginHooks } from '@/lib/plugin-hooks';
 
 const SLOT_NAMES: SlotName[] = [
   'toolbar-actions', 'email-banner', 'email-footer', 'composer-toolbar',
-  'sidebar-widget', 'settings-section', 'context-menu-email', 'navigation-rail-bottom',
+  'sidebar-widget', 'email-detail-sidebar', 'settings-section', 'context-menu-email', 'navigation-rail-bottom',
 ];
 
 function emptySlots(): Record<SlotName, SlotRegistration[]> {
@@ -136,6 +136,10 @@ export const usePluginStore = create<PluginStoreState>()(
         const plugin = plugins.find(p => p.id === id);
         if (!plugin) return;
 
+        // Ensure bridges are wired before loading (may not have run initializePlugins yet)
+        setPluginStoreAccessor({ setPluginStatus: get().setPluginStatus });
+        setSlotRegistrationBridge(get().registerSlot);
+
         set({
           plugins: plugins.map(p =>
             p.id === id ? { ...p, enabled: true, status: 'enabled' as PluginStatus, error: undefined } : p