@harness-kernel/sandbox-local

@harness-kernel/sandbox-local provides LocalSandbox, a runtime-owned sandbox that executes commands with bash -lc inside a configured work directory.

import { LocalSandbox } from "@harness-kernel/sandbox-local";

const sandbox = new LocalSandbox({
  workDir: ".",
  env: "minimal",
  defaultTimeoutMs: 30_000,
});

Attach it to the runtime:

const store = await createHarnessSessionStore({
  agent: { definition: agent },
  providers: [new OpenAIProvider()],
  defaultModel: "openai/gpt-5.1",
  sandbox,
});

Node tools such as BashTool and file tools call session.sandbox.exec(). The tools belong to modes; the sandbox belongs to the host.