BAR-2x7B-Tool-Use β€” GGUF (first-of-its-kind FlexOlmo conversion)

This is the first GGUF conversion of allenai/BAR-2x7B-Tool-Use, one of AllenAI's BAR-family Mixture-of-Experts models released on 2026-04-19 based on the new FlexOlmo architecture.

⚠ Requires patched llama.cpp

The FlexOlmo architecture is not yet supported in upstream llama.cpp. To run this GGUF you need a build with FlexOlmo support, currently in flight as a PR.

Build from the support branch:

git clone https://github.com/RhinoWithAcape/llama.cpp.git
cd llama.cpp
git checkout feature/flex-olmo-arch  # (or wait for upstream merge)
cmake -B build -DGGML_CUDA=OFF
cmake --build build -j --target llama-cli llama-quantize llama-completion

Once upstream PR lands, any standard llama.cpp / Ollama install will work directly.

What FlexOlmo is

Per transformers.models.flex_olmo, FlexOlmoDecoderLayer is Olmo2's hybrid post-norm decoder layer with the dense FFN swapped for OlmoE-style top-k MoE routing. Specifically:

  • Attention with q_norm and k_norm (Olmo2-style)
  • post_attention_layernorm and post_feedforward_layernorm (post-norm pattern, no input_layernorm)
  • Top-k MoE FFN with softmax routing (OlmoE-style)
  • No sliding-window attention

Model details

Field Value
Architecture FlexOlmoForCausalLM (Olmo2 hybrid + OlmoE MoE)
Total parameters ~11.6 B
Active parameters per token ~11 B (top-2 of 2 experts β†’ effectively dense forward)
Layers 32
Hidden size 4096
Attention heads 32 (no GQA; head dim 128)
Experts 2 routed, top-2 selected
Vocab 100,278
Context 64K (rope_theta 500000)

Quants

Quant Size Status
Q4_K_M ~6.7 GB βœ… uploaded β€” recommended for consumer GPUs (12GB+)
Q5_K_M ~8 GB rolling out (uploaded as ready)
Q6_K ~10 GB rolling out
Q8_0 ~12 GB rolling out
F16 ~22 GB available on request

Usage β€” Ollama

(Once your llama.cpp / Ollama has FlexOlmo support):

hf download RhinoWithAcape/BAR-2x7B-Tool-Use-GGUF \
  BAR-2x7B-Tool-Use.Q4_K_M.gguf Modelfile --local-dir ./bar
cd ./bar
ollama create bar-2x7b-tool:Q4_K_M -f Modelfile
ollama run bar-2x7b-tool:Q4_K_M "Hello"

Usage β€” llama.cpp (with FlexOlmo support built)

./build/bin/llama-completion \
    -m BAR-2x7B-Tool-Use.Q4_K_M.gguf \
    -p "Q: A train travels 60 miles in 1.5 hours. What's its average speed in mph?\nA:" \
    -n 60 --temp 0.3

Sample output:

"To find the average speed, we need to divide the distance by the time. So, the average speed is 60 miles / 1.5 hours = 40 mph."

Validation

Q4_K_M was tested on three prompts during development:

  • Factual: "The capital of France is" β†’ "Paris."
  • Reasoning: 60mi/1.5h speed problem β†’ "40 mph" with steps
  • Code/explanation: fibonacci docstring β†’ coherent explanation of memoization

All clean stops on the model's EOS, no looping or degeneration.

License

Apache 2.0 (matching the source release at AllenAI). This conversion is a derivative work β€” same license applies.

Conversion details

  • Source: allenai/BAR-2x7B-Tool-Use (downloaded 2026-04-29)
  • Tools: patched llama.cpp on feature/flex-olmo-arch branch
  • Steps: convert_hf_to_gguf.py β†’ llama-quantize
  • Architecture support added in: PR (pending) <link>

Acknowledgments

  • AllenAI for the BAR family release and the FlexOlmo architecture
  • llama.cpp maintainers β€” the existing Olmo2 + OlmoE handlers gave us the right primitives to combine
  • This conversion produced for the Zenith swarm project β€” autonomous engineering collective

Citation

If you use this GGUF, please cite AllenAI's BAR release:

@misc{allenai2026bar,
  title  = {BAR: Beam-and-Adjust-Routing models},
  author = {{Allen Institute for AI}},
  year   = {2026},
  month  = {April},
  url    = {https://huggingface.co/allenai/BAR-2x7B-Tool-Use}
}
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