LocalLLaMA Flags an Experimental Apple Neural Engine Backend for llama.cpp

A March 30, 2026 post in r/LocalLLaMA surfaced an experimental Apple Neural Engine backend for llama.cpp. By March 31, the thread had 68 points and 21 comments, enough to stand out because it points to a very specific attempt to move matrix work off the usual CPU and Metal path.

What is actually implemented

The Reddit post links to an issue comment in ggml-org/llama.cpp and the companion ggml-ane repository. In that comment, the author says the backend dispatches MUL_MAT operations to Apple’s Neural Engine through a private API. The same note describes it as a working ggml backend rather than an official upstream feature.

The cited M4 Pro result is 4.0 TFLOPS peak at N=256.

The author says that is 16.8x faster than CPU on the tested path.

The prototype currently uses ANE for prefill at N >= 64 and falls back to Metal or CPU for decode.

The comment also mentions MIL-side transpose, a kernel cache, and support for quantized weights. Those details matter because they suggest the work is targeting real local-inference bottlenecks instead of merely proving that ANE can run a toy kernel. At the same time, the implementation relies on a private API, which is an important constraint for anyone expecting a production-ready or officially supported rollout.

Why it matters

Most Apple Silicon local-LLM stacks still split work between CPU and Metal, with the Neural Engine largely unused by open-source inference runtimes. If this experiment matures, it could create a third execution path for prefill-heavy workloads and reduce pressure on the GPU during mixed local workloads.

Even in its current state, the post is a useful signal: developers are testing whether ANE can become a serious inference target for ggml and llama.cpp, not just a hardware talking point. The community source is the Reddit thread; the primary technical source is the linked GitHub issue comment and prototype repository.