Sandboxes

Harness adapters declare requires: [SandboxCapability]. chat() errors unless some middleware provides it — withSandbox(...) does. The adapter then runs the agent CLI inside the sandbox and streams its events back.

Setup — Claude Code in a Docker sandbox

import { chat } from '@tanstack/ai'
import { claudeCodeText } from '@tanstack/ai-claude-code'
import {
  defineSandbox,
  defineWorkspace,
  withSandbox,
} from '@tanstack/ai-sandbox'
import { dockerSandbox } from '@tanstack/ai-sandbox-docker'