Agents API offers three execution modes: work without a sandbox, an OpenAI-hosted sandbox, or your own connected executor. The Codex harness stays hosted in all three. Built-in computer use currently uses an OpenAI-hosted browser; self-hosted files need your own retrieval.
Execution environment options
| Mode | Service capability | Application responsibility |
|---|---|---|
| None | Hosted reasoning loop, remote MCP and application function requests. | Function handlers and external services. No built-in environment filesystem or Bash. |
| OpenAI-hosted | Managed sandbox, commands, files and configured browser computer use. | Configure access, handle required approvals, verify outcomes. |
| Self-hosted | Hosted harness sends commands to codex exec-server on chosen compute. |
Provisioning, connection, isolation, file persistence and shutdown. |
The built-in computer-use guide specifies an OpenAI-hosted browser environment. This does not establish computer use for arbitrary self-hosted desktops.
Hosted outputs under /workspace/outputs can be published as downloadable artifacts. Retrieve self-hosted files through your own provider or filesystem.