app_trace

This tool on every surface: CLI · MCP · Python · JavaScript · Go · Java · .NET

Record a session as a trace: start, then every call on this device is a step — before and after, the point an action touched, a failure's error — and after each the screen, with the map's elements drawn over it; stop with a path saves a zip in Vibium's record format, which player.vibium.dev opens. Omit the action to ask whether one is running. Text typed into a field is not recorded, only its length. On a real phone the screenshots are its owner's screen; screenshots false keeps none. One trace per device; ending the session discards it.

Changes the device, the app or the session: readOnlyHint is false.

Arguments

Name	Type	Required	What it is
action	string: start, stop		start or stop. Omit to ask whether a trace is running.
device	string		Device serial to target, e.g. "emulator-5554". Omit when only one device is running.
driver	string: uiautomator2, uiautomator, wda		Driver to use: "uiautomator2" (default for Android; fast, installs a server APK on first use), "uiautomator" (Android, installs nothing, slower, cannot type), or "wda" (WebDriverAgent: iOS simulators and iPhones).
maps	boolean		On start: draw the map's elements over each screenshot. Default true.
name	string		On start: the trace's title, as the viewers show it.
path	string		On stop: where to save the trace, a .zip on this machine.
return_data	boolean		On stop without a path: return the zip, base64, instead of saving it — for a daemon on another machine; the CLI and pipe ask for it and save it where the caller said.
screenshots	boolean		On start: keep the screen after each call. Default true.

Examples

Each is the arguments of a tools/call request; the first is shown whole.

Start tracing the session

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "app_trace",
    "arguments": {
      "action": "start",
      "name": "sign in"
    }
  }
}

Stop, and save the trace

{
  "action": "stop",
  "path": "sign-in.zip"
}