Flyweight: open-source C++/CUDA engine runs VRAM-busting MoE models on one GPU plus system RAM

Main-Wolverine-1042 · reddit · 2026-09-18

Flyweight (Apache-2.0) is a native C++/CUDA GGUF inference runtime that runs MoE models bigger than your VRAM on a single consumer NVIDIA card plus system RAM, auto-planning expert offload at startup. On a 5070 Ti 12GB laptop it hits 35 tok/s decode on Qwen3.8-Flash-Next IQ1S, 40 tok/s on a 27B IQ2XXS, 6-7 tok/s on DeepSeek-V4-Flash, and runs Z-Image-Turbo beside the chat model. Kernels compile at runtime via NVRTC (no CUDA toolkit in wheel), KV cache supports f16/q80/4-bit TurboQuant, tool calls are grammar-enforced, and it ships OpenAI/Anthropic-compatible APIs plus a chat UI. Author openly used Claude Code for much of the coding, with parity-tested kernels.

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