Brezel

Brezel is an open-source, self-hosted Firecracker sandbox runtime for autonomous agents.

Installation

npm install computesdk @computesdk/brezel

Configure a project-scoped service token, the public HTTPS endpoint, and a prequalified immutable environment revision:

BREZEL_API_KEY=your_project_scoped_token
BREZEL_API_URL=https://brezel.example.com
BREZEL_PROJECT_ID=agents
BREZEL_ENVIRONMENT_REVISION=envr_qualified
BREZEL_ALLOW_INTERNET=false

Usage

import { brezel } from '@computesdk/brezel';

const compute = brezel({
  apiKey: process.env.BREZEL_API_KEY,
  baseUrl: process.env.BREZEL_API_URL,
  project: process.env.BREZEL_PROJECT_ID,
  environmentRevision: process.env.BREZEL_ENVIRONMENT_REVISION,
  allowInternet: false,
});

const sandbox = await compute.sandbox.create();
const result = await sandbox.runCommand('node --version');
console.log(result.stdout);
await sandbox.destroy();

Configuration options

Option	Environment variable	Description
apiKey	BREZEL_API_KEY	Project-scoped Brezel service token.
baseUrl	BREZEL_API_URL	Public HTTPS endpoint for the Brezel deployment.
project	BREZEL_PROJECT_ID	Project boundary used for sandbox operations.
environmentRevision	BREZEL_ENVIRONMENT_REVISION	Prequalified immutable environment revision used by default.
allowInternet	BREZEL_ALLOW_INTERNET	Allows outbound internet access when exactly true; defaults to false.
apiTimeoutMs	—	Timeout for Brezel management API operations, in milliseconds.

Supported operations

Method	Supported	Notes
create	✅	Uses a prequalified immutable environment revision.
getById	✅	Returns null for absent or terminal sandboxes.
list	✅	Lists active sandboxes in the configured project.
destroy	✅	Waits for a confirmed terminal state or resource absence.
runCommand	✅	Supports env, cwd, background execution, and output callbacks.
getInfo	✅	Includes the environment revision and Brezel resource revision.
getUrl	✅	Creates a time-limited preview lease for a guest port.
filesystem	✅	Native file reads/writes plus directory operations.
snapshot	❌	Not exposed through ComputeSDK yet.

templateId may override the configured immutable environment revision for a single create call. Arbitrary image builds are intentionally outside the request path.

Create-time environment variables are not exposed because Brezel cannot yet restore them durably after reconnection. Pass environment variables to runCommand instead.