diff --git a/frontend/src/features/plugins/PluginRuntimeProvider.tsx b/frontend/src/features/plugins/PluginRuntimeProvider.tsx
index 026ee17..2ff26b5 100644
--- a/frontend/src/features/plugins/PluginRuntimeProvider.tsx
+++ b/frontend/src/features/plugins/PluginRuntimeProvider.tsx
@@ -38,6 +38,13 @@ const EMPTY_PLUGIN_RUNTIME: PluginRuntimeContextValue = {
 
 const PluginRuntimeContext = createContext<PluginRuntimeContextValue>(EMPTY_PLUGIN_RUNTIME);
 
+function describeError(e: unknown): string {
+  if (e && typeof e === "object" && "message" in e) {
+    return String((e as { message: unknown }).message);
+  }
+  return String(e);
+}
+
 interface PluginRuntimeProviderProps {
   children: ReactNode;
   /** Test/Storybook escape hatch — skips the gateway fetch and uses this value as-is. */
@@ -72,10 +79,19 @@ export function PluginRuntimeProvider({ children, value: injected }: PluginRunti
         if (cancelled) return;
         setValue({ registry: result.registry, failures: result.failures, loading: false });
       })
-      .catch(() => {
+      .catch((e: unknown) => {
         // No plugin gateway / catalog fetch failed: run with zero plugins
         // rather than blocking the app (full-trust plugins are additive).
-        if (!cancelled) setValue((prev) => ({ ...prev, loading: false }));
+        if (!cancelled) {
+          setValue((prev) => ({
+            ...prev,
+            failures: [
+              ...prev.failures,
+              { pluginId: "<runtime-catalog>", reason: describeError(e) },
+            ],
+            loading: false,
+          }));
+        }
       });
     return () => {
       cancelled = true;
diff --git a/frontend/src/features/plugins/PluginsPanel.tsx b/frontend/src/features/plugins/PluginsPanel.tsx
index 35e3d7f..6b1c6e4 100644
--- a/frontend/src/features/plugins/PluginsPanel.tsx
+++ b/frontend/src/features/plugins/PluginsPanel.tsx
@@ -167,7 +167,11 @@ export function PluginsPanel() {
                   )}
                 </div>
                 <div className="flex shrink-0 items-center gap-2">
-                  {p.enabled ? (
+                  {p.lifecycleState === "invalid" ? (
+                    <Button size="sm" variant="ghost" disabled>
+                      Isolé
+                    </Button>
+                  ) : p.enabled ? (
                     <Button
                       size="sm"
                       variant="ghost"
diff --git a/frontend/src/features/plugins/plugins.test.tsx b/frontend/src/features/plugins/plugins.test.tsx
index f9c1f7e..ccde192 100644
--- a/frontend/src/features/plugins/plugins.test.tsx
+++ b/frontend/src/features/plugins/plugins.test.tsx
@@ -7,6 +7,7 @@ import { describe, it, expect } from "vitest";
 import { render, screen, waitFor, fireEvent, within } from "@testing-library/react";
 
 import { MockPluginGateway, MockSystemGateway } from "@/adapters/mock";
+import type { PluginInstallResult, PluginRuntimeContributionCatalog } from "@/domain";
 import type { Gateways } from "@/ports";
 import { DIProvider } from "@/app/di";
 import { PluginRuntimeRegistry } from "@/plugins/runtime";
@@ -38,6 +39,44 @@ function renderPanel(
   };
 }
 
+function renderPanelWithLiveRuntime(plugin: MockPluginGateway, system = new MockSystemGateway()) {
+  const gateways = { plugin, system } as unknown as Gateways;
+  return render(
+    <DIProvider gateways={gateways}>
+      <PluginRuntimeProvider>
+        <PluginsPanel />
+      </PluginRuntimeProvider>
+    </DIProvider>,
+  );
+}
+
+class InvalidInstallPluginGateway extends MockPluginGateway {
+  async installFromDirectory(path: string): Promise<PluginInstallResult> {
+    const plugin = {
+      id: "dev.idea.fixtures.missing-main",
+      displayName: "Missing Main Plugin",
+      version: "0.1.0",
+      sourceKind: "directory" as const,
+      sourceLabel: path,
+      lifecycleState: "invalid" as const,
+      enabled: false,
+      pendingUninstall: false,
+      restartRequired: false,
+      trustLevel: "full" as const,
+      contributionSummary: { topLevelMenus: 1, menuItems: 1, layouts: 0, mcpServers: 0 },
+      error: "plugin main asset is missing: dist/index.js",
+    };
+    this._seedPlugin(plugin);
+    return { plugin, restartRequired: false };
+  }
+}
+
+class FailingRuntimeCatalogPluginGateway extends MockPluginGateway {
+  async listRuntimeContributions(): Promise<PluginRuntimeContributionCatalog> {
+    throw { code: "INVALID", message: "runtime catalog failed" };
+  }
+}
+
 describe("PluginsPanel", () => {
   it("shows an empty state with no plugins installed", async () => {
     renderPanel();
@@ -57,6 +96,15 @@ describe("PluginsPanel", () => {
     expect(screen.getByText(/Cannot use import statement outside a module/)).toBeTruthy();
   });
 
+  it("keeps the Plugins panel rendered when the runtime catalog fetch fails", async () => {
+    renderPanelWithLiveRuntime(new FailingRuntimeCatalogPluginGateway());
+
+    expect(await screen.findByText("Aucun plugin installé.")).toBeTruthy();
+    expect(screen.getByText("Certains plugins installés n'ont pas pu être chargés.")).toBeTruthy();
+    expect(screen.getByText("<runtime-catalog>")).toBeTruthy();
+    expect(screen.getByText(/runtime catalog failed/)).toBeTruthy();
+  });
+
   it("installs from an archive via the review dialog, mentioning full-trust", async () => {
     renderPanel();
     await screen.findByText("Aucun plugin installé.");
@@ -74,6 +122,21 @@ describe("PluginsPanel", () => {
     expect(screen.getByText("Activé")).toBeTruthy();
   });
 
+  it("renders an invalid plugin returned after install as isolated, without replacing the panel", async () => {
+    renderPanel(new InvalidInstallPluginGateway());
+    await screen.findByText("Aucun plugin installé.");
+
+    fireEvent.click(screen.getByRole("button", { name: "Installer depuis un dossier…" }));
+    const dialog = await screen.findByRole("dialog");
+    fireEvent.click(within(dialog).getByRole("button", { name: "Installer" }));
+
+    expect(await screen.findByText("Missing Main Plugin")).toBeTruthy();
+    expect(screen.getByText("Invalide")).toBeTruthy();
+    expect(screen.getByText("plugin main asset is missing: dist/index.js")).toBeTruthy();
+    expect(screen.getByRole("button", { name: "Isolé" }).hasAttribute("disabled")).toBe(true);
+    expect(screen.queryByRole("button", { name: "Activer" })).toBeNull();
+  });
+
   it("disables an installed plugin after confirmation", async () => {
     const plugin = new MockPluginGateway();
     plugin._seedPlugin({
diff --git a/frontend/src/plugins/runtime/loader.test.ts b/frontend/src/plugins/runtime/loader.test.ts
index 77528a6..79329d6 100644
--- a/frontend/src/plugins/runtime/loader.test.ts
+++ b/frontend/src/plugins/runtime/loader.test.ts
@@ -52,6 +52,26 @@ describe("loadPlugins", () => {
     expect((globalThis as Record<string, unknown>).__activatedWith).toBe("dev.acme.one");
   });
 
+  it("loads an SDK-style default export containing activate(ctx)", async () => {
+    const bundle = dataUrl(`
+      export default {
+        activate(ctx) {
+          globalThis.__defaultExportActivatedWith = ctx.pluginId;
+        },
+      };
+    `);
+    const { registry, failures } = await loadPlugins(
+      [entry({ id: "com.example.hello-plugin", displayName: "Hello Plugin", bundleUrl: bundle })],
+      gateways,
+    );
+
+    expect(failures).toEqual([]);
+    expect(registry.list().map((p) => p.pluginId)).toEqual(["com.example.hello-plugin"]);
+    expect((globalThis as Record<string, unknown>).__defaultExportActivatedWith).toBe(
+      "com.example.hello-plugin",
+    );
+  });
+
   it("refuses to register a command not declared in the manifest", async () => {
     const bundle = dataUrl(`
       export function activate(ctx) {
@@ -259,6 +279,32 @@ describe("loadPlugins", () => {
     ]);
   });
 
+  it("disposes partial subscriptions when activation fails", async () => {
+    const bundle = dataUrl(`
+      export function activate(ctx) {
+        ctx.subscriptions.push({
+          dispose() {
+            globalThis.__partialActivationDisposed = ctx.pluginId;
+          },
+        });
+        throw new Error("activation failed");
+      }
+    `);
+
+    const { registry, failures } = await loadPlugins(
+      [entry({ id: "dev.acme.partial", displayName: "Partial", bundleUrl: bundle })],
+      gateways,
+    );
+
+    expect(registry.list()).toEqual([]);
+    expect(failures).toEqual([
+      { pluginId: "dev.acme.partial", reason: "activation failed" },
+    ]);
+    expect((globalThis as Record<string, unknown>).__partialActivationDisposed).toBe(
+      "dev.acme.partial",
+    );
+  });
+
   it("only loads what the catalog contains — a disabled/absent plugin is simply never in it", async () => {
     // The backend contract (carnet §1.3) filters the catalog to
     // `enabled && !pendingUninstall` before the loader ever sees it; the
diff --git a/frontend/src/plugins/runtime/loader.ts b/frontend/src/plugins/runtime/loader.ts
index ac9e071..77d4803 100644
--- a/frontend/src/plugins/runtime/loader.ts
+++ b/frontend/src/plugins/runtime/loader.ts
@@ -81,6 +81,12 @@ function isIdeaPluginModule(mod: unknown): mod is IdeaPluginModule {
   );
 }
 
+function resolveIdeaPluginModule(mod: unknown): IdeaPluginModule | null {
+  if (isIdeaPluginModule(mod)) return mod;
+  const defaultExport = objectOrEmpty(mod).default;
+  return isIdeaPluginModule(defaultExport) ? defaultExport : null;
+}
+
 function createPluginLogger(entry: PluginRuntimePlugin): PluginLogger {
   const prefix = `[plugin:${safePluginId(entry)}]`;
   return {
@@ -169,6 +175,8 @@ async function loadOne(
   const pluginId = safePluginId(entry);
   const displayName = nonEmptyString(entryObject.displayName) ?? pluginId;
   const version = nonEmptyString(entryObject.version) ?? "";
+  let activation: void | PluginActivation = undefined;
+  const subscriptions: Disposable[] = [];
   try {
     // The bundle URL is a plugin-scoped, content-hashed local protocol URL
     // served by the backend (carnet §1.3) — never a disk path or arbitrary
@@ -178,8 +186,8 @@ async function loadOne(
       throw new Error("missing plugin bundle URL");
     }
 
-    const mod: unknown = await import(/* @vite-ignore */ bundleUrl);
-    if (!isIdeaPluginModule(mod)) {
+    const mod = resolveIdeaPluginModule(await import(/* @vite-ignore */ bundleUrl));
+    if (!mod) {
       return {
         failure: {
           pluginId,
@@ -194,7 +202,6 @@ async function loadOne(
     const commands = new PluginCommandRegistry(pluginId, declaredCommandIds);
     const layouts = new PluginLayoutRegistry(pluginId, declaredLayoutTypes);
     const menu = new PluginMenuRegistry(pluginId);
-    const subscriptions: Disposable[] = [];
 
     const ctx: IdeaPluginContext = {
       pluginId,
@@ -208,7 +215,7 @@ async function loadOne(
       ...gateways,
     };
 
-    const activation = await mod.activate(ctx);
+    activation = await mod.activate(ctx);
 
     const plugin: LoadedPlugin = {
       pluginId,
@@ -225,6 +232,7 @@ async function loadOne(
     };
     return { plugin };
   } catch (e) {
+    await disposeAll(subscriptions, activation);
     return {
       failure: {
         pluginId,