@runanywhere/electron-qhexrt

QHexRT backend package for the Electron SDK — text generation on the Qualcomm Hexagon NPU.

Supported host today: Windows on ARM64 (Snapdragon X / X2 Elite, Hexagon v81). Off-platform builds still install and register; the engine reports BACKEND_UNAVAILABLE and the router can never select it, so a cross-platform app can depend on this package unconditionally.

Usage (main process only)

import { QHexRT } from '@runanywhere/electron-qhexrt';
QHexRT.register(); // before RunAnywhereMain.connect()

Registration records prebuilds/<platform>-<arch>/runanywhere_qhexrt.dll in the main-process queue; RunAnywhereMain copies it into RUNANYWHERE_PLUGIN_PATHS at utility-host fork. There is no renderer RPC that can load a plugin.

What ships in prebuilds/win32-arm64/

The plugin and the flat QAIRT runtime it opens at load time:

| file | from | |---|---| | runanywhere_qhexrt.dll | this repo (engines/qhexrt) | | rac_commons.dll | this repo — the thin addon's shared commons | | QnnHtp.dll, QnnSystem.dll, QnnHtpPrepare.dll, QnnHtpV81Stub.dll | <QAIRT>/lib/aarch64-windows-msvc/ | | libQnnHtpV81Skel.so, libqnnhtpv81.cat | <QAIRT>/lib/hexagon-v81/unsigned/ |

All in one directory. There is no ADSP_LIBRARY_PATH on Windows — the loader resolves the stub's dependencies through the DLL's own directory, and the SDK prepends every registered plugin directory to PATH because the engine opens QnnHtp.dll by bare name at runtime.

The .cat is not optional. Without it the DSP skel fails signature verification and the failure never names the catalog — it looks like a corrupt model bundle.

Bundles

QHexRT runs prebuilt QNN context bundles (runanywhere/*_HNPU on Hugging Face), not GGUF. Two compatibility axes, both load-time and both silent until they aren't:

• Arch pinning. dsp_arch + soc_model are baked into the context binary. A v79 bundle does not load on a v81 device.
• QAIRT floor. The deployed runtime must be >= the QAIRT that compiled the bundle. Measured: a v81 bundle compiled on 2.47 fails contextCreateFromBinary with err=0x1388 on 2.41 and loads on 2.48. The actionable message (Using newer context binary on old SDK) appears only in the backend's stderr.

Model download

initialize() registers the libcurl HTTP transport only when commons was built with -DRAC_DESKTOP_ADAPTER=ON. Without it, register an already-downloaded bundle directory instead of resolving one from Hugging Face.