lvt — Live Visual Tree

A Windows CLI tool that inspects the visual tree of running applications. Designed for AI agents (e.g. GitHub Copilot) that need a textual representation of an app's UI content.

What it does

• Targets any running Windows app by HWND, PID, process name, or window title
• Detects UI frameworks in use: Win32, ComCtl, Windows XAML (UWP), WinUI 3, WPF
• Outputs a unified element tree as JSON or XML markup
• Captures annotated PNG screenshots with element IDs overlaid
• Elements get stable IDs (e0, e1, …) so AI agents can reference specific parts of the UI

Quick start

Download

Grab the latest release from GitHub Releases — extract the zip and run lvt.exe from any terminal.

Install the Copilot skill

The easiest way to add the lvt skill to GitHub Copilot CLI is to install it as a plugin:

/plugin install asklar/lvt

This gives Copilot the ability to inspect any running Windows app's UI when you ask it to. Verify with /skills list.

Build from source

Prerequisites

• Visual Studio 2022+ (C++ Desktop workload)
• vcpkg with VCPKG_ROOT environment variable set
• CMake 3.20+
• x64 Developer Command Prompt

Build

# x64 build (default)
cmake --preset default
cmake --build build

# ARM64 build
cmake --preset arm64
cmake --build build-arm64

Produces build/lvt.exe and build/lvt_tap_x64.dll (or build-arm64/lvt.exe and build-arm64/lvt_tap_arm64.dll for ARM64).

Note: lvt.exe must match the target process's architecture. If you target an ARM64 app, use the ARM64 build. A clear error message is shown on mismatch.

Usage

# Dump Notepad's visual tree as JSON
lvt --name notepad

# XML output
lvt --name notepad --format xml

# Capture annotated screenshot
lvt --pid 1234 --screenshot out.png

# Just detect frameworks
lvt --hwnd 0x1A0B3C --frameworks

# Scope to a subtree
lvt --name myapp --element e5 --depth 3

# Screenshot + tree dump together
lvt --name notepad --screenshot out.png --dump

Options

Flag	Description
--hwnd <handle>	Target window by HWND (hex)
--pid <pid>	Target process by PID
--name <exe>	Target by process name (e.g. notepad or notepad.exe)
--title <text>	Target by window title substring
--output <file>	Write tree to file instead of stdout
--format <fmt>	json (default) or xml
--screenshot <file>	Capture annotated screenshot to PNG
--dump	Output the tree (default unless --screenshot is used)
--element <id>	Scope to a specific element subtree
--frameworks	Just list detected frameworks
--depth <n>	Max tree traversal depth

Output format

JSON

{
  "target": { "hwnd": "0x001A0B3C", "pid": 12345, "processName": "Notepad.exe" },
  "frameworks": ["win32", "winui3"],
  "root": {
    "id": "e0",
    "type": "Window",
    "framework": "win32",
    "className": "Notepad",
    "text": "Untitled - Notepad",
    "bounds": { "x": 100, "y": 100, "width": 800, "height": 600 },
    "children": [
      {
        "id": "e1",
        "type": "ContentPresenter",
        "framework": "winui3",
        "bounds": { "x": 108, "y": 140, "width": 784, "height": 552 }
      }
    ]
  }
}

XML

<LiveVisualTree hwnd="0x001A0B3C" pid="12345" process="Notepad.exe" frameworks="win32,winui3">
  <Window id="e0" framework="win32" className="Notepad" text="Untitled - Notepad" bounds="100,100,800,600">
    <ContentPresenter id="e1" framework="winui3" bounds="108,140,784,552" />
  </Window>
</LiveVisualTree>

Architecture

The tool uses a 4-stage pipeline:

1. Target resolution — resolve HWND/PID/name/title to a target window
2. Framework detection — enumerate loaded DLLs to detect UI frameworks
3. Tree building — Win32 HWND walk as base, framework providers layer on top
4. Serialization — output as JSON/XML, optionally capture screenshot

Framework providers:

• Win32Provider — base HWND tree (always present)
• ComCtlProvider — enriches ComCtl32 controls (ListView items, TreeView nodes, etc.)
• XamlProvider — injects TAP DLL to walk Windows XAML visual trees
• WinUI3Provider — injects TAP DLL to walk WinUI 3 visual trees
• WpfProvider — walks WPF visual trees via plugin

See docs/architecture.md for details.

Design principles

• No UI Automation — uses framework-native APIs directly for speed and accuracy
• Graceful degradation — if a framework provider fails, falls back to HWND-level info
• AI-first — output formats and element IDs designed for machine consumption
• Minimal footprint — single exe + one DLL, no installers, no runtime dependencies

Tests

# Run unit tests
build\lvt_unit_tests.exe

# Run integration tests (launches Notepad automatically)
build\lvt_integration_tests.exe

# Via CTest
ctest --test-dir build

Plugin system

lvt supports a plugin architecture for adding new framework providers. Plugins are DLLs that implement a simple C interface and are loaded automatically from %USERPROFILE%\.lvt\plugins\.

See src/plugin.h for the plugin interface.

Future work

• WinForms provider
• WebView2 provider
• MAUI provider
• Element property querying (--query <id> <property>)
• Accessibility tree correlation
• Watch mode for live tree diffing

License

MIT — see LICENSE.