diff --git a/libs/plugins-runtime/src/lib/create-plugin.spec.ts b/libs/plugins-runtime/src/lib/create-plugin.spec.ts
index b94d411..9c413a5 100644
--- a/libs/plugins-runtime/src/lib/create-plugin.spec.ts
+++ b/libs/plugins-runtime/src/lib/create-plugin.spec.ts
@@ -106,4 +106,14 @@ describe('createPlugin', () => {
 
     expect(mockSandbox.evaluate).toHaveBeenCalled();
   });
+
+  it('should call plugin.close when there is an exception during sandbox evaluation', async () => {
+    vi.mocked(mockSandbox.evaluate).mockImplementation(() => {
+      throw new Error('Evaluation error');
+    });
+
+    await createPlugin(mockContext, manifest, onCloseCallback);
+
+    expect(mockPluginManager.close).toHaveBeenCalled();
+  });
 });
diff --git a/libs/plugins-runtime/src/lib/create-plugin.ts b/libs/plugins-runtime/src/lib/create-plugin.ts
index 955a500..d126066 100644
--- a/libs/plugins-runtime/src/lib/create-plugin.ts
+++ b/libs/plugins-runtime/src/lib/create-plugin.ts
@@ -8,6 +8,16 @@ export async function createPlugin(
   manifest: Manifest,
   onCloseCallback: () => void
 ) {
+  const evaluateSandbox = async () => {
+    try {
+      sandbox.evaluate();
+    } catch (error) {
+      console.error(error);
+
+      plugin.close();
+    }
+  };
+
   const plugin = await createPluginManager(
     context,
     manifest,
@@ -16,12 +26,13 @@ export async function createPlugin(
       onCloseCallback();
     },
     function onReloadModal() {
-      sandbox.evaluate();
+      evaluateSandbox();
     }
   );
 
   const sandbox = createSandbox(plugin);
-  sandbox.evaluate();
+
+  evaluateSandbox();
 
   return {
     plugin,
diff --git a/libs/plugins-runtime/src/lib/create-sandbox.spec.ts b/libs/plugins-runtime/src/lib/create-sandbox.spec.ts
index a38fbf0..f2dcfc3 100644
--- a/libs/plugins-runtime/src/lib/create-sandbox.spec.ts
+++ b/libs/plugins-runtime/src/lib/create-sandbox.spec.ts
@@ -18,6 +18,7 @@ vi.mock('./ses.js', () => ({
       };
     }),
     harden: vi.fn().mockImplementation((obj) => obj),
+    safeReturn: vi.fn().mockImplementation((obj) => obj),
   },
 }));
 
@@ -90,22 +91,48 @@ describe('createSandbox', () => {
     expect(Object.keys(compartment.globalThis).length).toBe(0);
   });
 
-  it('should ensure fetch requests omit credentials', async () => {
+  it('should ensure fetch requests omit credentials and return a harden response', async () => {
+    const mockResponse = {
+      ok: true,
+      status: 200,
+      statusText: 'OK',
+      url: 'https://example.com/api',
+      text: vi.fn().mockResolvedValue('response text'),
+      json: vi.fn().mockResolvedValue({ key: 'value' }),
+    };
+
     const sandbox = createSandbox(mockPlugin);
     const fetchSpy = vi
       .spyOn(window, 'fetch')
-      .mockResolvedValue(new Response());
+      .mockResolvedValue(mockResponse as unknown as Response);
 
     await sandbox.compartment.globalThis['fetch']('https://example.com/api', {
       method: 'GET',
       credentials: 'include',
+      headers: {
+        Authorization: 'Bearer token',
+      },
     });
 
     expect(fetchSpy).toHaveBeenCalledWith('https://example.com/api', {
       method: 'GET',
       credentials: 'omit',
+      headers: expect.objectContaining({
+        Authorization: '',
+      }),
     });
 
+    expect(ses.safeReturn).toHaveBeenCalledWith(
+      expect.objectContaining({
+        ok: true,
+        status: 200,
+        statusText: 'OK',
+        url: 'https://example.com/api',
+        text: expect.any(Function),
+        json: expect.any(Function),
+      })
+    );
+
     fetchSpy.mockRestore();
   });
 
@@ -122,4 +149,15 @@ describe('createSandbox', () => {
       Object.keys(sandbox.compartment.globalThis).filter((it) => !!it).length
     ).toBe(0);
   });
+
+  it('should return safe values for penpot methods via proxy', () => {
+    const sandbox = createSandbox(mockPlugin);
+    const mockPenpotMethod = vi.fn().mockReturnValue('penpot result');
+    sandbox.compartment.globalThis['penpot'].mockMethod = mockPenpotMethod;
+
+    const result = sandbox.compartment.globalThis['penpot'].mockMethod();
+
+    expect(ses.safeReturn).toHaveBeenCalledWith('penpot result');
+    expect(result).toBe('penpot result');
+  });
 });
diff --git a/libs/plugins-runtime/src/lib/create-sandbox.ts b/libs/plugins-runtime/src/lib/create-sandbox.ts
index 0d62ab2..cf219c7 100644
--- a/libs/plugins-runtime/src/lib/create-sandbox.ts
+++ b/libs/plugins-runtime/src/lib/create-sandbox.ts
@@ -2,7 +2,6 @@ import type { Penpot } from '@penpot/plugin-types';
 import type { createPluginManager } from './plugin-manager';
 import { createApi } from './api';
 import { ses } from './ses.js';
-
 export function createSandbox(
   plugin: Awaited<ReturnType<typeof createPluginManager>>
 ) {
@@ -10,16 +9,51 @@ export function createSandbox(
 
   const pluginApi = createApi(plugin);
 
-  const publicPluginApi = {
-    penpot: ses.harden(pluginApi.penpot) as Penpot,
-    fetch: ses.harden((...args: Parameters<typeof fetch>) => {
-      const requestArgs: RequestInit = {
-        ...args[1],
-        credentials: 'omit',
+  const safeHandler = {
+    get(target: Penpot, prop: string, receiver: unknown) {
+      const originalValue = Reflect.get(target, prop, receiver);
+
+      if (typeof originalValue === 'function') {
+        return function (...args: unknown[]) {
+          const result = originalValue.apply(target, args);
+
+          return ses.safeReturn(result);
+        };
+      }
+
+      return ses.safeReturn(originalValue);
+    },
+  };
+
+  const proxyApi = new Proxy(pluginApi.penpot, safeHandler);
+
+  const safeFetch = (url: string, options: RequestInit) => {
+    const sanitizedOptions: RequestInit = {
+      ...options,
+      credentials: 'omit',
+      headers: {
+        ...options?.headers,
+        Authorization: '',
+      },
+    };
+
+    return fetch(url, sanitizedOptions).then((response) => {
+      const safeResponse = {
+        ok: response.ok,
+        status: response.status,
+        statusText: response.statusText,
+        url: response.url,
+        text: response.text.bind(response),
+        json: response.json.bind(response),
       };
 
-      return fetch(args[0], requestArgs);
-    }),
+      return ses.safeReturn(safeResponse);
+    });
+  };
+
+  const publicPluginApi = {
+    penpot: proxyApi,
+    fetch: ses.harden(safeFetch),
     console: ses.harden(window.console),
     Math: ses.harden(Math),
     setTimeout: ses.harden(
@@ -30,7 +64,7 @@ export function createSandbox(
 
         plugin.timeouts.add(timeoutId);
 
-        return timeoutId;
+        return ses.safeReturn(timeoutId);
       }
     ) as typeof setTimeout,
     clearTimeout: ses.harden((id: ReturnType<typeof setTimeout>) => {
diff --git a/libs/plugins-runtime/src/lib/load-plugin.spec.ts b/libs/plugins-runtime/src/lib/load-plugin.spec.ts
index 07a52a7..647d410 100644
--- a/libs/plugins-runtime/src/lib/load-plugin.spec.ts
+++ b/libs/plugins-runtime/src/lib/load-plugin.spec.ts
@@ -19,6 +19,12 @@ vi.mock('./create-plugin', () => ({
   createPlugin: vi.fn(),
 }));
 
+vi.mock('./ses.js', () => ({
+  ses: {
+    harden: vi.fn().mockImplementation((obj) => obj),
+  },
+}));
+
 describe('plugin-loader', () => {
   let mockContext: Context;
   let manifest: Manifest;
diff --git a/libs/plugins-runtime/src/lib/load-plugin.ts b/libs/plugins-runtime/src/lib/load-plugin.ts
index adea7dd..bbeabbb 100644
--- a/libs/plugins-runtime/src/lib/load-plugin.ts
+++ b/libs/plugins-runtime/src/lib/load-plugin.ts
@@ -3,6 +3,7 @@ import type { Context } from '@penpot/plugin-types';
 import { loadManifest } from './parse-manifest.js';
 import { Manifest } from './models/manifest.model.js';
 import { createPlugin } from './create-plugin.js';
+import { ses } from './ses.js';
 
 let plugins: Awaited<ReturnType<typeof createPlugin>>[] = [];
 
@@ -44,9 +45,13 @@ export const loadPlugin = async function (manifest: Manifest) {
 
     closeAllPlugins();
 
-    const plugin = await createPlugin(context, manifest, () => {
-      plugins = plugins.filter((api) => api !== plugin);
-    });
+    const plugin = await createPlugin(
+      ses.harden(context) as Context,
+      manifest,
+      () => {
+        plugins = plugins.filter((api) => api !== plugin);
+      }
+    );
 
     plugins.push(plugin);
   } catch (error) {
diff --git a/libs/plugins-runtime/src/lib/ses.ts b/libs/plugins-runtime/src/lib/ses.ts
index fb63a35..6c505cc 100644
--- a/libs/plugins-runtime/src/lib/ses.ts
+++ b/libs/plugins-runtime/src/lib/ses.ts
@@ -13,4 +13,11 @@ export const ses = {
   harden: (obj: Object) => {
     return harden(obj);
   },
+  safeReturn<T>(value: T): T {
+    if (value === null || value === undefined) {
+      return value;
+    }
+
+    return harden(value) as T;
+  },
 };