// ==========================================
// JavaScript Sandbox — Browser Extension
// ==========================================
// Executes JavaScript in a sandboxed iframe.
// Registers the js_eval tool so the LLM can run code,
// verify calculations, and transform data.
//
// Security: The iframe has sandbox="allow-scripts" only.
// No allow-same-origin, no network, no DOM access.
// ==========================================
Extensions.register({
id: 'js-sandbox',
_iframe: null,
_pendingCallbacks: new Map(), // messageId → { resolve, reject, timer }
_messageCounter: 0,
async init(ctx) {
const self = this;
// Create the sandboxed iframe on first use (lazy)
ctx.tools.handle('js_eval', async (args) => {
return self._execute(args.code || '');
});
},
async _execute(code) {
if (!code.trim()) {
return { error: 'No code provided' };
}
// Ensure iframe is ready
await this._ensureIframe();
const messageId = 'eval-' + (++this._messageCounter);
const TIMEOUT_MS = 10000;
return new Promise((resolve) => {
// Set up timeout
const timer = setTimeout(() => {
this._pendingCallbacks.delete(messageId);
resolve({
success: false,
error: 'Execution timed out (10s)',
output: [],
result: null,
});
}, TIMEOUT_MS);
this._pendingCallbacks.set(messageId, { resolve, timer });
// Send code to sandbox
this._iframe.contentWindow.postMessage({
type: 'eval',
id: messageId,
code: code,
}, '*');
});
},
_ensureIframe() {
if (this._iframe) return Promise.resolve();
return new Promise((resolve) => {
// Build sandbox HTML as a blob URL
const sandboxHTML = this._buildSandboxHTML();
const blob = new Blob([sandboxHTML], { type: 'text/html' });
const blobURL = URL.createObjectURL(blob);
const iframe = document.createElement('iframe');
iframe.sandbox = 'allow-scripts';
iframe.style.cssText = 'display:none;width:0;height:0;border:none;position:absolute;';
iframe.src = blobURL;
iframe.onload = () => {
this._iframe = iframe;
URL.revokeObjectURL(blobURL);
resolve();
};
// Listen for messages from sandbox
window.addEventListener('message', (event) => {
// Only accept messages from our sandbox iframe
if (!this._iframe || event.source !== this._iframe.contentWindow) return;
const data = event.data;
if (data?.type !== 'eval-result') return;
const pending = this._pendingCallbacks.get(data.id);
if (!pending) return;
clearTimeout(pending.timer);
this._pendingCallbacks.delete(data.id);
pending.resolve({
success: !data.error,
result: data.result !== undefined ? data.result : null,
output: data.output || [],
error: data.error || null,
});
});
document.body.appendChild(iframe);
});
},
_buildSandboxHTML() {
// This HTML runs INSIDE the sandboxed iframe.
// It has no access to the parent page, no network, no cookies.
return `
Sandbox