Dr. Farshid Pirahansiah
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By Dr. Farshid Pirahansiah — computer vision & embedded edge AI consultant, Berlin, Germany · 12+ years. Updated 2026-09-30.

Running K2-Horizon Locally on Apple Silicon — Serve IFM's K2-Horizon GGUF via the MBZUAI-IFM llama.cpp fork and wire it into Hermes at 64K context. — https://www.pirahansiah.com/notes/docs/llm/k2-horizon-local/

Running K2-Horizon Locally on Apple Silicon (M3, 16GB)

K2-Horizon (by IFM / MBZUAI) is a compact reasoning model family. The published weights (IFM/K2-Horizon-0.9B-GGUF) are GGUF only in a custom k2-horizon architecture (a MoVA-style attention/value-router). That breaks the usual local paths:

Last updated: 2026-09-05.

Why oMLX and Ollama cannot load it (verified)

  • oMLX (the MLX server) ingests only MLX safetensors (config.json + *.safetensors). A .gguf is not ingestible by oMLX at all — there is no add/pull for GGUF.
  • Ollama bundles mainline llama.cpp, which has no k2-horizon support yet. The upstream PR is still in progress.
  • The model's own README states it requires "a version of llama.cpp containing K2 Horizon architecture support" — i.e. the MBZUAI-IFM fork at github.com/MBZUAI-IFM/llama.cpp (model/K2Horizon branch).

Grepping the ollama 0.30.6 and oMLX 0.6.4 binaries confirms zero k2-horizon references, whereas the fork's src/models/k2-horizon.cpp + libllama.0.3.0.dylib do contain it.

Build the MBZUAI-IFM llama.cpp fork (Metal)

# Use the exact validated commit the model authors recommend.
git clone --branch model/K2Horizon --single-branch \
  https://github.com/MBZUAI-IFM/llama.cpp.git llama.cpp-k2
cd llama.cpp-k2
git log -1 --format='%H %s'   # expect 35999d101... "model: K2 Horizon chat template ..."

# Apple Silicon: Metal backend, embed the Metal lib, Release.
cmake -B build -DGGML_METAL=ON -DGGML_METAL_EMBED_LIBRARY=ON \
      -DCMAKE_BUILD_TYPE=Release -DLLAMA_CURL=ON
cmake --build build --target llama-server -j $(sysctl -n hw.ncpu)

Verify the architecture is compiled in:

strings build/bin/libllama.0.3.0.dylib | grep -c k2-horizon   # expect > 0
./build/bin/llama-server --version                            # 0.3.0-dev, commit 35999d101

Download the GGUF

mkdir -p ~/models/k2-horizon
curl -L -o ~/models/k2-horizon/K2-Horizon-1B-BF16.gguf \
  "https://huggingface.co/IFM/K2-Horizon-0.9B-GGUF/resolve/main/K2-Horizon-1B-BF16.gguf"
# ~2.16 GB, BF16 full precision (fine for 0.9B/1B class on 16 GB unified RAM)

Serve on :8080

./build/bin/llama-server \
  --model ~/models/k2-horizon/K2-Horizon-1B-BF16.gguf \
  --alias k2-horizon:latest \
  --host 127.0.0.1 --port 8080 \
  --ctx-size 65536 --n-gpu-layers 99 --flash-attn on \
  --reasoning-format deepseek --reasoning-effort default
  • --ctx-size 65536 — Hermes enforces a 64K context floor for the default model; smaller and it refuses with "Choose a model with at least 64K context."
  • --reasoning-format deepseek — populates message.reasoning_content (K2 is a reasoner).
  • --flash-attn on (not a bare flag — the server needs the on value).

Health + generation check:

curl -s http://127.0.0.1:8080/health                 # {"status":"ok"}
curl -s http://127.0.0.1:8080/v1/models | grep -o 'k2-horizon:latest'

Wire into Hermes (separate endpoint, do NOT touch oMLX's :8000)

Point Hermes at the :8080 server via a new custom provider — keep oMLX on :8000 as-is:

hermes config set model.base_url "http://127.0.0.1:8080/v1"
hermes config set model.default "k2-horizon:latest"
hermes config set agent.model    "k2-horizon:latest"
hermes config set delegation.base_url "http://127.0.0.1:8080/v1"
hermes config set delegation.model    "k2-horizon:latest"
hermes gateway restart

Verify: hermes chat -q "hi" → gateway log shows model=k2-horizon:latest provider=custom base_url=http://127.0.0.1:8080/v1.

Persistence (survives reboot / logout)

~/Library/LaunchAgents/com.farshid.k2-horizon-serve.plist — RunAtLoad + KeepAlive, mirroring the oMLX agent in the Local LLM Optimization guide (§7a). Only one process may hold :8080.

Gotchas

  • It is a reasoner. Every reply includes a reasoning_content trace and is slow (~24 s for a 40-token answer) — that is the model's nature, not a misconfig.
  • BF16 GGUF is large. 2.16 GB for ~1B params; watch RAM if you add bigger BF16 GGUFs on 16 GB.
  • No oMLX/Ollama route. If you need K2-Horizon in oMLX, you must first convert the GGUF to MLX safetensors (and even then the custom arch's grouped RMSNorm needs a custom loader), which is not provided for the 0.9B/1B size as of this writing (community MLX conversions exist only for 3.7B/7B, and require --trust-remote-code). The llama.cpp fork is the supported path.

Source: Pirahansiah, F. “Running K2-Horizon Locally on Apple Silicon”. pirahansiah.com, updated 2026-09-30. Canonical URL https://pirahansiah.com/farshid/content/k2-horizon-local/ · markdown source k2-horizon-local.md · how to cite, quote and link this site.