dotnet/maui · error · Exception

Unexpected device type (expected: device|emulator) in device

Error message

Unexpected device type (expected: device|emulator) in device: {deviceDescriptor}

What it means

Thrown while parsing a device descriptor when the second segment (device type) is not one of 'device', 'emulator', or 'simulator'. After confirming the platform is android, the parser expects a concrete device-kind token.

Source

Thrown at eng/devices/android.cake:398

	var working = deviceDescriptor.Trim().ToLower();
	var emulator = true;
	var api = defaultApiLevel;
	// version
	if (working.IndexOf("_") is int idx && idx > 0)
	{
		api = int.Parse(working.Substring(idx + 1));
		working = working.Substring(0, idx);
	}
	var parts = working.Split('-');
	// os
	if (parts[0] != "android")
		throw new Exception("Unexpected platform (expected: android) in device: " + deviceDescriptor);
	// device/emulator
	Information("Create for: {0}", parts[1]);
	if (parts[1] == "device")
		emulator = false;
	else if (parts[1] != "emulator" && parts[1] != "simulator")
		throw new Exception("Unexpected device type (expected: device|emulator) in device: " + deviceDescriptor);
	// arch/bits
	Information("Host OS System Arch: {0}", System.Runtime.InteropServices.RuntimeInformation.OSArchitecture);
	Information("Host Processor System Arch: {0}", System.Runtime.InteropServices.RuntimeInformation.ProcessArchitecture);
	if (parts[2] == "32")
	{
		if (emulator)
			deviceArch = "x86";
		else
			deviceArch = "armeabi-v7a";
	}
	else if (parts[2] == "64")
	{
		if (isArm64)
			deviceArch = "arm64-v8a";
		else if (emulator)
			deviceArch = "x86_64";
		else
			deviceArch = "arm64-v8a";

View on GitHub (pinned to f377ff1c5e)

Solutions

Use 'device' for a physical Android device or 'emulator' for an Android emulator in the descriptor.
Correct typos in the ANDROID_TEST_DEVICE env var / --device argument.
Refer to the parser's accepted tokens: device | emulator (simulator also accepted).

Example fix

# before
--device=android-phone-64_30
# after
--device=android-device-64_30

Defensive patterns

Strategy: validation

Validate before calling

var validTypes = new[] { "device", "emulator", "simulator" };
if (!validTypes.Contains(parts[1]))
    throw new Exception($"Invalid device type '{parts[1]}'. Expected one of: {string.Join("|", validTypes)}.");

Type guard

bool IsValidDeviceType(string descriptor) {
    var p = descriptor.Trim().ToLower().Split('-');
    return p.Length >= 2 && new[]{"device","emulator","simulator"}.Contains(p[1]);
}

Prevention

List accepted tokens in the error message itself.
Validate the whole descriptor up front rather than failing mid-parse.
Add a unit-style test over the descriptor parser for each accepted shape.

When it happens

Trigger: parts[1] is something other than 'device', 'emulator', or 'simulator' — e.g. 'android-phone-64' or 'android-real-64'. (Note 'simulator' is accepted but semantically unusual for Android.)

Common situations: Typo in the device type token (phone, real, phys instead of device); copying a descriptor format from another system; an outdated descriptor after the format changed.

Related errors

AI-assisted analysis of dotnet/maui@f377ff1c5e (2026-08-13). Data as JSON: /api/errors/07e77b393411f412. Report an issue: GitHub.