ctx
Worktrees and Runtime

Containerization

Choose between host and sandbox execution

Overview

ctx exposes two execution modes for agent work:

  • Host
  • Sandbox

Host is the low-isolation option for direct local execution.

Sandbox is the isolated option for autonomous agent work.

If you are unsure which mode to start with, use Sandbox first and move to Host only when you intentionally need direct access to your local machine.

Execution modes

Host

Choose Host when:

  • you want direct access to your local environment
  • you are intentionally prioritizing speed and convenience over isolation
  • you do not need sandbox-enforced network or filesystem boundaries

Sandbox

Choose Sandbox when:

  • you want isolated execution for agent work
  • you want more reproducible runtime behavior across tasks
  • you want explicit sandbox-level policy such as network controls
  • you want workspace changes to stay reviewable and easier to reason about

Important boundary rule

There is no host-mounted sandbox mode in the intended product model.

  • If you want direct host files and minimal ceremony, use Host.
  • If you want isolation for autonomous agents, use Sandbox.

Practical default

  • Default to Sandbox for normal agent work.
  • Use Host only when you intentionally want the escape hatch.

Quick decision rule

  • Choose Sandbox when you want stronger isolation, cleaner repeatability, or explicit network policy.
  • Choose Host when you are debugging locally and you knowingly want the agent to use your existing machine setup directly.

Common pitfalls

  • Missing dependencies inside the sandbox: move setup into bootstrap or environment configuration instead of assuming the host already has everything installed.
  • Different results across runs: keep the sandbox environment and setup steps explicit.
  • Network surprises: pair sandbox usage with a clear egress policy.