Dotnet Maui Doctor skill

.NET MAUI Doctor

Validate and fix .NET MAUI development environments. All version requirements are discovered dynamically from NuGet APIs — never hardcode versions.

When to Use

• Setting up a new .NET MAUI development environment
• Build errors mentioning missing SDKs, workloads, JDK, or Android components
• Errors like "Android SDK not found", "Java version", or "Xcode not found"
• Verifying environment health after SDK or OS updates

When Not to Use

• Non-MAUI .NET projects (use standard .NET SDK troubleshooting instead)
• Xamarin.Forms apps (different toolchain and workload requirements)
• Runtime app crashes unrelated to environment setup
• App store publishing or signing issues
• IDE-specific issues (Visual Studio or VS Code configuration)

Important: .NET Version Currency

Your training data may be outdated regarding .NET versions. .NET ships new major releases annually (November). Always check the releases-index.json (Task 2) to discover the latest active major release — do not assume your training data reflects the current version. For example, if you know about .NET 9.0 but the releases index shows .NET 10.0 as active, use .NET 10.0.

Inputs

• A development machine running macOS, Windows, or Linux
• Shell access (Bash on macOS/Linux, PowerShell on Windows)
• Internet access for NuGet API queries and SDK downloads
• Admin/sudo access may be required for installing SDKs and workloads
• Bash prerequisites: curl, jq, and unzip (macOS/Linux)
• PowerShell prerequisites: Invoke-RestMethod and System.IO.Compression (built-in on Windows)

Behavior

• Run through ALL tasks autonomously
• Re-validate after each fix
• Iterate until complete or no further actions possible
• After detecting platform (Task 1), load only the matching platform-specific references

Workflow

Task 1: Detect Environment

# macOS
sw_vers && uname -m

# Windows
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"

# Linux
cat /etc/os-release && uname -m

After detection, load the matching platform references:

• macOS: references/platform-requirements-macos.md, references/installation-commands-macos.md, references/troubleshooting-macos.md
• Windows: references/platform-requirements-windows.md, references/installation-commands-windows.md, references/troubleshooting-windows.md
• Linux: references/platform-requirements-linux.md

Task 2: Check .NET SDK

dotnet --info

Compare installed vs latest-sdk from https://dotnetcli.blob.core.windows.net/dotnet/release-metadata/releases-index.json where support-phase is "active".

Task 3: Check MAUI Workloads

Workload	macOS	Windows	Linux
maui	Required	Required	❌ Use maui-android
maui-android	Alias	Alias	Required
android	Required	Required	Required
ios	Required	Optional	N/A

Task 4: Discover Requirements from NuGet

See references/workload-dependencies-discovery.md for complete process.

Query NuGet for workload manifest → extract WorkloadDependencies.json → get:

• jdk.version range and jdk.recommendedVersion
• androidsdk.packages, buildToolsVersion, apiLevel
• xcode.version range

Task 5: Validate Java JDK

Only Microsoft OpenJDK supported. Verify java -version output contains "Microsoft". See references/microsoft-openjdk.md for detection paths.

Use the JDK version recommended by WorkloadDependencies.json (jdk.recommendedVersion), ensuring it satisfies the jdk.version range. Do not hardcode JDK versions.

JAVA_HOME is NOT required. .NET MAUI tools auto-detect Microsoft OpenJDK installations from known paths. Do not tell users to set JAVA_HOME — it is unnecessary and risks pointing to a non-Microsoft JDK.

JAVA_HOME state	OK?	Action
Not set	✅	None needed — auto-detection works
Set to Microsoft JDK	✅	None needed
Set to non-Microsoft JDK	⚠️	Report as anomaly — let user decide to unset or redirect

Task 6: Validate Android SDK

Check packages from androidsdk.packages, buildToolsVersion, apiLevel (Task 4). See references/installation-commands.md for sdkmanager commands.

Task 7: Validate Xcode (macOS Only)

xcodebuild -version

Compare against xcode.version range from Task 4. See references/installation-commands-macos.md.

Task 8: Validate Windows SDK (Windows Only)

The Windows SDK is typically installed as part of the .NET MAUI workload or Visual Studio. See references/installation-commands-windows.md.

Task 9: Remediation

See references/installation-commands.md for all commands.

Key rules:

• Workloads: Always use --version flag. Never use workload update or workload repair.
• JDK: Only install Microsoft OpenJDK. Do not set JAVA_HOME (auto-detected).
• Android SDK: Use sdkmanager (from Android SDK command-line tools). On Windows use sdkmanager.bat.

Task 10: Re-validate

After each fix, re-run the relevant validation task. Iterate until all checks pass.

Validation

A successful run produces:

• .NET SDK installed and matches an active release
• All required workloads installed with consistent versions
• Microsoft OpenJDK detected (java -version contains "Microsoft")
• All required Android SDK packages installed (per WorkloadDependencies.json)
• Xcode version in supported range (macOS only)
• Windows SDK detected (Windows only)

Build Verification (Recommended)

After all checks pass, create and build a test project to confirm the environment actually works:

TEMP_DIR=$(mktemp -d)
dotnet new maui -o "$TEMP_DIR/MauiTest"
dotnet build "$TEMP_DIR/MauiTest"
rm -rf "$TEMP_DIR"

On Windows, use $env:TEMP or New-TemporaryFile for the temp directory.

If the build succeeds, the environment is verified. If it fails, use the error output to diagnose remaining issues.

Run Verification (Optional — Ask User First)

After a successful build, ask the user if they want to launch the app on a target platform to verify end-to-end:

# Replace net10.0 with the current major .NET version
dotnet build -t:Run -f net10.0-android
dotnet build -t:Run -f net10.0-ios        # macOS only
dotnet build -t:Run -f net10.0-maccatalyst # macOS only
dotnet build -t:Run -f net10.0-windows    # Windows only

Only run the target frameworks relevant to the user's platform and intent. This step deploys to an emulator/simulator/device, so confirm with the user before proceeding.

Common Pitfalls

• maui vs maui-android workload: On Linux, the maui meta-workload is not available — use maui-android instead. On macOS/Windows, maui installs all platform workloads.
• workload update / workload repair: Never use these commands. Always install workloads with an explicit --version flag to ensure version consistency.
• Non-Microsoft JDK: Only Microsoft OpenJDK is supported. Other distributions (Oracle, Adoptium, Azul) will cause build failures even if the version is correct.
• Unnecessary JAVA_HOME: Do not set JAVA_HOME. MAUI auto-detects JDK from known install paths. If JAVA_HOME is set to a non-Microsoft JDK (e.g., Temurin), report this as an anomaly — it may override auto-detection and cause failures. Let the user decide whether to unset it.
• Hardcoded versions: Never hardcode SDK, workload, or dependency versions. Always discover them dynamically from the NuGet APIs (see Task 4).
• Android SDK sdkmanager on Windows: Use sdkmanager.bat, not sdkmanager, on Windows.
• Stale training data: LLM training data may reference outdated .NET versions. Always check the releases-index.json to discover the current active release.

References

• references/workload-dependencies-discovery.md — NuGet API discovery process
• references/microsoft-openjdk.md — JDK detection paths, identification, JAVA_HOME
• references/installation-commands.md — .NET workloads, Android SDK (sdkmanager)
• references/troubleshooting.md — Common errors and solutions
• references/platform-requirements-{platform}.md — Platform-specific requirements
• references/installation-commands-{platform}.md — Platform-specific install commands
• references/troubleshooting-{platform}.md — Platform-specific troubleshooting

Official docs:

• .NET MAUI Installation
• .NET SDK Downloads
• Microsoft OpenJDK
• Android SDK Command-Line Tools
• Xcode Downloads