GammaRay MCP Bridge

A MCP server that bridges GammaRay probe introspection data into MCP tools, enabling LLMs to inspect and debug Qt Quick / QML scene graphs, items, geometry, materials, and Qt Widgets.

Architecture

Target Qt/QML App  ──TCP──►  GammaRay MCP Bridge  ──stdio──►  LLM / AI Agent
  (GammaRay probe                (GammaRay client +               (opencode,
   injected)                      qtmcp MCP server)                ZCode, etc.)

The bridge is a GammaRay client: it connects to a probe injected into a target Qt app, reads the same models the GammaRay GUI uses, and translates them into MCP JSON-RPC tool calls over stdio. Supports both QML Quick apps (SceneGraph, QML items) and Qt Widget apps (widget hierarchy, properties, attributes).

Prerequisites

• Qt 6.8+ (system)
• C++20 compiler (GCC 12+, Clang 16+)
• GammaRay 3.4.0+ (system package: gammaray-dev on Debian/Deepin)
• qtmcp (consumed via FetchContent — no manual install)
• Python 3.10+ with pytest (for running the test suite)

Building

1. Install system dependencies

# Debian / Deepin
sudo apt install gammaray-dev gammaray-plugin-quickinspector

2. Build the bridge

cd bridge
cmake -S . -B build -G Ninja
cmake --build build

Offline build (using a local qtmcp clone)

If you have a local clone of qtmcp (e.g. at /home/user/Sources/qtmcp), pass FETCHCONTENT_SOURCE_DIR_QTMcp to skip the network fetch:

cd bridge
cmake -S . -B build -G Ninja \
  -DFETCHCONTENT_SOURCE_DIR_QTMcp=/home/user/Sources/qtmcp \
  -DFETCHCONTENT_FULLY_DISCONNECTED=ON
cmake --build build

3. Run

# Start a probe (inject into a QML app)
gammaray --inject-only --listen tcp://127.0.0.1:11732 \
  --injector preload /usr/lib/qt6/bin/qml /path/to/app.qml -platform offscreen

# Or inject into a widget app
gammaray --inject-only --listen tcp://127.0.0.1:11732 \
  --injector preload /path/to/widget-app

# Start the bridge (stdio MCP server)
bridge/run.sh

The bridge starts in lazy-connect mode. Call connectProbe("127.0.0.1", 11732) from your MCP client once the probe is up.

4. Build a .deb package (optional)

cd bridge/build
cpack -G DEB

The package installs the bridge binary (/usr/bin/gammaray-mcp-bridge), qtmcp shared libs and plugins, and the run.sh helper script. System dependencies (gammaray >= 3.4.0, Qt6 libs) are auto-detected.

MCP Tools

Connection management

Tool	Description
connectProbe(host, port)	Connect to a GammaRay probe (defaults: 127.0.0.1:11732)
connectProbeDefault()	Convenience: connect to 127.0.0.1:11732
disconnectProbe()	Drop connection and forget URL
probeStatus()	Report connection state

QML Navigation

Tool	Description
listQuickWindows()	List QQuickWindows in the target app
selectQuickWindow(index)	Select a window for scene graph introspection
listQuickItems()	Recursive QQuickItem tree with types and flags
listScenegraphNodes()	Recursive QSGNode tree (all node types)

QML Item inspection

Tool	Description
selectQuickItem(address)	Select a QML item by address, populating its properties model
getItemProperties(address)	Get all Q_PROPERTY values (x, y, width, height, opacity, visible, z, anchors, text, font, etc.)

SG Node inspection

Tool	Description
selectScenegraphNode(address)	Select a SG node, populating geometry/material sub-models
getNodeVertices(address)	Read vertex data of a GeometryNode
getNodeAdjacency(address)	Read adjacency/drawing mode of a GeometryNode
getMaterialShaders(address)	List shader stages for a node's material
getShaderSource(row)	Get shader source code (async via MaterialExtensionInterface)
getMaterialProperties(address)	Get material property name/value pairs

Rendering visualization

Tool	Description
setRenderMode(mode)	Set render mode (NormalRendering, VisualizeOverdraw, etc.)
setSlowMode(enabled)	Toggle continuous rendering

Widget inspection

Tool	Description
listWidgets()	Recursive QWidget hierarchy (types, names, visibility)
selectWidget(address)	Select a widget, populating its property and attribute models
getWidgetProperties(address)	Get all Q_PROPERTY values (geometry, font, palette, window flags, etc.)
getWidgetAttributes(address)	Get Qt::WidgetAttribute flags (acceptDrops, enabled, etc.)

Testing

# QML test suite (requires a QML app probe):
./tests/run_tests.sh

# Widget test suite (requires a widget app probe):
./tests/run_widget_tests.sh

# Unit tests only:
./tests/run_tests.sh --no-probe

See tests/README.md for details.

License

GPL-2.0-or-later. The bridge links GammaRay libraries (GPL-2.0-or-later) and uses qtmcp (available under LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only — we comply under GPL-2.0-only).