--- modificationDate: October 15, 2026 title: Expo Simulators session types description: Compare the four Expo Simulators session types, what each one provisions, and how each one installs apps, reports activity, and connects to the remote device. --- This documentation is available as Markdown for AI agents and LLMs. See the [full Markdown index](https://docs.expo.dev/llms.txt) or append .md to any documentation URL. # Expo Simulators session types Compare the four Expo Simulators session types, what each one provisions, and how each one installs apps, reports activity, and connects to the remote device. ## Submitting Feedback If you encounter errors, misleading or outdated information, report it so Expo can be improved: Preferred command: npx --yes submit-expo-feedback@latest --category docs --subject "/preview/simulators/reference/session-types/" "" Direct HTTP fallback: curl -X POST https://api.expo.dev/v2/feedback/docs-send -H 'Content-Type: application/json' -d '{"url":"/preview/simulators/reference/session-types/","feedback":"🤖 Agent feedback for docs: (, )"}' Only submit when you have something specific and actionable to report. Try to give the most context. > **Expo Simulators is a limited-access preview.** It is not included with paid or free plans and is currently available only to select partners. [Join the waitlist](https://expo.dev/services/simulators) if you are interested in trying it. The **session type** sets which controller EAS starts next to the remote device. There are four session types: `agent-device`, `argent`, `appium`, and `web-preview-only`. Set the type with `--type` in EAS CLI or `type` in the REST API. The default type is `agent-device`. ## Compare the session types | Session type | Controller | Use it for | | --- | --- | --- | | `agent-device` | [agent-device](https://docs.expo.dev/agents/agent-device.md) daemon | Agent-driven control, app installation, screenshots, and recordings. | | `argent` | [Argent](https://docs.expo.dev/agents/argent.md) tool server | Argent tools and its Model Context Protocol (MCP) server. | | `appium` | Appium server | Existing Appium clients and test suites. | | `web-preview-only` | None | A person who uses the browser preview without programmatic control. | Each session type includes a browser preview. Each session type also provisions only its own controller. For example, agent-device commands do not work in an `argent` session. ## Connection details When a session is ready, EAS returns its connection details. EAS CLI writes them to **.env.eas-simulator**. The REST API returns them in `remoteConfig`. | Session type | Variables in **.env.eas-simulator** | Fields in `remoteConfig` | | --- | --- | --- | | `agent-device` | `AGENT_DEVICE_DAEMON_BASE_URL`, `AGENT_DEVICE_DAEMON_AUTH_TOKEN` | `agentDeviceRemoteSessionUrl`, `agentDeviceRemoteSessionToken`, optional `webPreviewUrl` and `webPreviewToken` | | `argent` | `ARGENT_TOOLS_URL` and, when required, `ARGENT_AUTH_TOKEN` | `toolsUrl`, optional `toolsAuthToken`, optional `webPreviewUrl` and `webPreviewToken` | | `appium` | `APPIUM_URL`, `APPIUM_CAPS` (JSON) | `appiumUrl`, `capabilities`, optional `webPreviewUrl` and `webPreviewToken` | | `web-preview-only` | Only `EAS_SIMULATOR_SESSION_ID` | `webPreviewUrl`, optional `webPreviewToken` | The `remoteConfig` fields above are the REST API fields. When `webPreviewToken` is present, the browser preview URL works only with the token. See [Open the browser preview](https://docs.expo.dev/preview/simulators/reference/rest-api.md#open-the-browser-preview) for how to add it. In `--json` output, EAS CLI adds the token to the URL for you. There, the field is `remoteConfig.webPreviewUrl`, or `remoteConfig.previewUrl` for a `web-preview-only` session. The tokens in these values give access to the remote device. Keep them secret. See [Expo Simulators security, permissions, and data retention](https://docs.expo.dev/preview/simulators/reference/security-and-data.md). ## Behavior by session type | Behavior | `agent-device` | `argent` | `appium` | `web-preview-only` | | --- | --- | --- | --- | --- | | Start flags install and launch the app | Yes | Yes | Yes | Yes | | Controller activity resets the idle timer | Yes | Yes | Yes | No | | Supports `--max-idle-time-minutes` | Yes | Yes | Yes | No | | Activity appears in `eas simulator:events` | Yes | Yes | Yes | No | Notes: - The start flags are `--build-id`, `--build-fingerprint`, `--application-archive-url`, `--expo-go`, `--launch-arg`, and `--open-url`. To connect an Appium client, see [Run Appium tests on a remote Android Emulator or iOS Simulator](https://docs.expo.dev/preview/simulators/works-with/appium.md). - Controller activity from agent-device, Argent, or Appium resets the idle timer. Browser preview activity does not. For sessions that a person controls in the browser preview, use `--max-duration-minutes` to limit the session. See [How long an Expo Simulators session runs](https://docs.expo.dev/preview/simulators/how-it-works/session-lifetime.md). - A `web-preview-only` session does not report activity, so it does not support an idle timeout. ## Choose a session type - Use `agent-device` for most work, and for coding agents. The Expo Simulators skill uses it. - Use `argent` when your agent already uses Argent tools or its MCP server. - Use `appium` when you already have Appium tests. - Use `web-preview-only` when a person only needs to see and use the simulator in a browser. The **Create new simulator** dialog on expo.dev offers the **Agent Device**, **Argent**, and **Appium** controllers. **Agent Device** is the default. ## The removed `serve-sim` type EAS CLI 23.0.0 renamed the preview-only type from `serve-sim` to `web-preview-only`. EAS now rejects new sessions with `"type": "serve-sim"`. Upgrade to EAS CLI 23.2.0 or later and use `web-preview-only`. Sessions created before the change still return `"type": "serve-sim"` from the REST API. In `--json` output, EAS CLI shows them as `web-preview-only`. ## Common questions #### Can I change the session type of a running session? No. EAS sets the session type when the session starts. Start a new session with a different `--type`. #### Do Android sessions include a browser preview? Yes. Android sessions include a browser preview that streams the emulator. Select **Open preview** on the session page on expo.dev to open it in a new tab. Android support is still in development, so some features that work on iOS may not work on Android yet. #### Which session type does a create session link use? A create session link always starts a `web-preview-only` session. Links support Android and iOS. Android support is still in development, and Android application archives must be **.apk** files. See [Share a live Expo Simulators session or start one from a link](https://docs.expo.dev/preview/simulators/how-to/hand-off-a-session.md#start-a-session-from-a-link).