feat(core): implement native Windows sandboxing

.geminiignore

@@ -0,0 +1 @@
+packages/core/src/services/scripts/*.exe

docs/cli/sandbox.md

@@ -50,7 +50,25 @@ Cross-platform sandboxing with complete process isolation.
 **Note**: Requires building the sandbox image locally or using a published image
 from your organization's registry.
 
-### 3. gVisor / runsc (Linux only)
+### 3. Windows Native Sandbox (Windows only)
+
+... **Troubleshooting and Side Effects:**
+
+The Windows Native sandbox uses the `icacls` command to set a "Low Mandatory
+Level" on files and directories it needs to write to.
+
+- **Persistence**: These integrity level changes are persistent on the
+  filesystem. Even after the sandbox session ends, files created or modified by
+  the sandbox will retain their "Low" integrity level.
+- **Manual Reset**: If you need to reset the integrity level of a file or
+  directory, you can use:
+  ```powershell
+  icacls "C:\path\to\dir" /setintegritylevel Medium
+  ```
+- **System Folders**: The sandbox manager automatically skips setting integrity
+  levels on system folders (like `C:\Windows`) for safety.
+
+### 4. gVisor / runsc (Linux only)
 
 Strongest isolation available: runs containers inside a user-space kernel via
 [gVisor](https://github.com/google/gvisor). gVisor intercepts all container

docs/cli/settings.md

@@ -115,6 +115,8 @@ they appear in the UI.
 
 | UI Label                         | Setting                              | Description                                                                                                                                                                | Default |
 | -------------------------------- | ------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
+| Sandbox Allowed Paths            | `tools.sandboxAllowedPaths`          | List of additional paths that the sandbox is allowed to access.                                                                                                            | `[]`    |
+| Sandbox Network Access           | `tools.sandboxNetworkAccess`         | Whether the sandbox is allowed to access the network.                                                                                                                      | `false` |
 | Enable Interactive Shell         | `tools.shell.enableInteractiveShell` | Use node-pty for an interactive shell experience. Fallback to child_process still applies.                                                                                 | `true`  |
 | Show Color                       | `tools.shell.showColor`              | Show color in shell output.                                                                                                                                                | `false` |
 | Use Ripgrep                      | `tools.useRipgrep`                   | Use ripgrep for file content search instead of the fallback implementation. Provides faster search performance.                                                            | `true`  |

docs/reference/configuration.md

@@ -1105,10 +1105,21 @@ their corresponding top-level category object in your `settings.json` file.
   - **Description:** Legacy full-process sandbox execution environment. Set to a
     boolean to enable or disable the sandbox, provide a string path to a sandbox
     profile, or specify an explicit sandbox command (e.g., "docker", "podman",
-    "lxc").
+    "lxc", "windows-native").
   - **Default:** `undefined`
   - **Requires restart:** Yes
 
+- **`tools.sandboxAllowedPaths`** (array):
+  - **Description:** List of additional paths that the sandbox is allowed to
+    access.
+  - **Default:** `[]`
+  - **Requires restart:** Yes
+
+- **`tools.sandboxNetworkAccess`** (boolean):
+  - **Description:** Whether the sandbox is allowed to access the network.
+  - **Default:** `false`
+  - **Requires restart:** Yes
+
 - **`tools.shell.enableInteractiveShell`** (boolean):
   - **Description:** Use node-pty for an interactive shell experience. Fallback
     to child_process still applies.

eslint.config.js

@@ -319,7 +319,12 @@ export default tseslint.config(
     },
   },
   {
-    files: ['./scripts/**/*.js', 'esbuild.config.js', 'packages/core/scripts/**/*.{js,mjs}'],
+    files: [
+      './scripts/**/*.js',
+      'packages/*/scripts/**/*.js',
+      'esbuild.config.js',
+      'packages/core/scripts/**/*.{js,mjs}',
+    ],
     languageOptions: {
       globals: {
         ...globals.node,

packages/cli/src/config/config.ts

@@ -702,6 +702,19 @@ export async function loadCliConfig(
       ? defaultModel
       : specifiedModel || defaultModel;
   const sandboxConfig = await loadSandboxConfig(settings, argv);
+  if (sandboxConfig) {
+    const existingPaths = sandboxConfig.allowedPaths || [];
+    if (settings.tools.sandboxAllowedPaths?.length) {
+      sandboxConfig.allowedPaths = [
+        ...new Set([...existingPaths, ...settings.tools.sandboxAllowedPaths]),
+      ];
+    }
+    if (settings.tools.sandboxNetworkAccess !== undefined) {
+      sandboxConfig.networkAccess =
+        sandboxConfig.networkAccess || settings.tools.sandboxNetworkAccess;
+    }
+  }
+
   const screenReader =
     argv.screenReader !== undefined
       ? argv.screenReader

packages/cli/src/config/sandboxConfig.test.ts

@@ -338,6 +338,8 @@ describe('loadSandboxConfig', () => {
             sandbox: {
               enabled: true,
               command: 'podman',
+              allowedPaths: [],
+              networkAccess: false,
             },
           },
         },
@@ -353,6 +355,8 @@ describe('loadSandboxConfig', () => {
             sandbox: {
               enabled: true,
               image: 'custom/image',
+              allowedPaths: [],
+              networkAccess: false,
             },
           },
         },
@@ -367,6 +371,8 @@ describe('loadSandboxConfig', () => {
           tools: {
             sandbox: {
               enabled: false,
+              allowedPaths: [],
+              networkAccess: false,
             },
           },
         },
@@ -382,6 +388,7 @@ describe('loadSandboxConfig', () => {
             sandbox: {
               enabled: true,
               allowedPaths: ['/settings-path'],
+              networkAccess: false,
             },
           },
         },

packages/cli/src/config/sandboxConfig.ts

@@ -29,6 +29,7 @@ const VALID_SANDBOX_COMMANDS = [
   'sandbox-exec',
   'runsc',
   'lxc',
+  'windows-native',
 ];
 
 function isSandboxCommand(
@@ -75,8 +76,15 @@ function getSandboxCommand(
         'gVisor (runsc) sandboxing is only supported on Linux',
       );
     }
-    // confirm that specified command exists
-    if (!commandExists.sync(sandbox)) {
+    // windows-native is only supported on Windows
+    if (sandbox === 'windows-native' && os.platform() !== 'win32') {
+      throw new FatalSandboxError(
+        'Windows native sandboxing is only supported on Windows',
+      );
+    }
+
+    // confirm that specified command exists (unless it's built-in)
+    if (sandbox !== 'windows-native' && !commandExists.sync(sandbox)) {
       throw new FatalSandboxError(
         `Missing sandbox command '${sandbox}' (from GEMINI_SANDBOX)`,
       );
@@ -149,7 +157,12 @@ export async function loadSandboxConfig(
     customImage ??
     packageJson?.config?.sandboxImageUri;
 
-  return command && image
+  const isNative =
+    command === 'windows-native' ||
+    command === 'sandbox-exec' ||
+    command === 'lxc';
+
+  return command && (image || isNative)
     ? { enabled: true, allowedPaths, networkAccess, command, image }
     : undefined;
 }

packages/cli/src/config/settingsSchema.ts

@@ -1344,10 +1344,30 @@ const SETTINGS_SCHEMA = {
         description: oneLine`
           Legacy full-process sandbox execution environment.
           Set to a boolean to enable or disable the sandbox, provide a string path to a sandbox profile,
-          or specify an explicit sandbox command (e.g., "docker", "podman", "lxc").
+          or specify an explicit sandbox command (e.g., "docker", "podman", "lxc", "windows-native").
         `,
         showInDialog: false,
       },
+      sandboxAllowedPaths: {
+        type: 'array',
+        label: 'Sandbox Allowed Paths',
+        category: 'Tools',
+        requiresRestart: true,
+        default: [] as string[],
+        description:
+          'List of additional paths that the sandbox is allowed to access.',
+        showInDialog: true,
+        items: { type: 'string' },
+      },
+      sandboxNetworkAccess: {
+        type: 'boolean',
+        label: 'Sandbox Network Access',
+        category: 'Tools',
+        requiresRestart: true,
+        default: false,
+        description: 'Whether the sandbox is allowed to access the network.',
+        showInDialog: true,
+      },
       shell: {
         type: 'object',
         label: 'Shell',

packages/cli/src/ui/hooks/slashCommandProcessor.ts

@@ -505,9 +505,7 @@ export const useSlashCommandProcessor = (
                       const props = result.props as Record<string, unknown>;
                       if (
                         !props ||
-                        // eslint-disable-next-line no-restricted-syntax
                         typeof props['name'] !== 'string' ||
-                        // eslint-disable-next-line no-restricted-syntax
                         typeof props['displayName'] !== 'string' ||
                         !props['definition']
                       ) {

packages/core/scripts/compile-windows-sandbox.js

@@ -0,0 +1,121 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/* eslint-env node */
+
+import { spawnSync } from 'node:child_process';
+import path from 'node:path';
+import fs from 'node:fs';
+import os from 'node:os';
+import { fileURLToPath } from 'node:url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+/**
+ * Compiles the GeminiSandbox C# helper on Windows.
+ * This is used to provide native restricted token sandboxing.
+ */
+function compileWindowsSandbox() {
+  if (os.platform() !== 'win32') {
+    return;
+  }
+
+  const srcHelperPath = path.resolve(
+    __dirname,
+    '../src/services/scripts/GeminiSandbox.exe',
+  );
+  const distHelperPath = path.resolve(
+    __dirname,
+    '../dist/src/services/scripts/GeminiSandbox.exe',
+  );
+  const sourcePath = path.resolve(
+    __dirname,
+    '../src/services/scripts/GeminiSandbox.cs',
+  );
+
+  if (!fs.existsSync(sourcePath)) {
+    console.error(`Sandbox source not found at ${sourcePath}`);
+    return;
+  }
+
+  // Ensure directories exist
+  [srcHelperPath, distHelperPath].forEach((p) => {
+    const dir = path.dirname(p);
+    if (!fs.existsSync(dir)) {
+      fs.mkdirSync(dir, { recursive: true });
+    }
+  });
+
+  // Find csc.exe (C# Compiler) which is built into Windows .NET Framework
+  const systemRoot = process.env['SystemRoot'] || 'C:\\Windows';
+  const cscPaths = [
+    'csc.exe', // Try in PATH first
+    path.join(
+      systemRoot,
+      'Microsoft.NET',
+      'Framework64',
+      'v4.0.30319',
+      'csc.exe',
+    ),
+    path.join(
+      systemRoot,
+      'Microsoft.NET',
+      'Framework',
+      'v4.0.30319',
+      'csc.exe',
+    ),
+  ];
+
+  let csc = undefined;
+  for (const p of cscPaths) {
+    if (p === 'csc.exe') {
+      const result = spawnSync('where', ['csc.exe'], { stdio: 'ignore' });
+      if (result.status === 0) {
+        csc = 'csc.exe';
+        break;
+      }
+    } else if (fs.existsSync(p)) {
+      csc = p;
+      break;
+    }
+  }
+
+  if (!csc) {
+    console.warn(
+      'Windows C# compiler (csc.exe) not found. Native sandboxing will attempt to compile on first run.',
+    );
+    return;
+  }
+
+  console.log(`Compiling native Windows sandbox helper...`);
+  // Compile to src
+  let result = spawnSync(
+    csc,
+    [`/out:${srcHelperPath}`, '/optimize', sourcePath],
+    {
+      stdio: 'inherit',
+    },
+  );
+
+  if (result.status === 0) {
+    console.log('Successfully compiled GeminiSandbox.exe to src');
+    // Copy to dist if dist exists
+    const distDir = path.resolve(__dirname, '../dist');
+    if (fs.existsSync(distDir)) {
+      const distScriptsDir = path.dirname(distHelperPath);
+      if (!fs.existsSync(distScriptsDir)) {
+        fs.mkdirSync(distScriptsDir, { recursive: true });
+      }
+      fs.copyFileSync(srcHelperPath, distHelperPath);
+      console.log('Successfully copied GeminiSandbox.exe to dist');
+    }
+  } else {
+    console.error('Failed to compile Windows sandbox helper.');
+  }
+}
+
+compileWindowsSandbox();