hal0

FastContext-Hal0-4B β€” ROCmFP4 (STRIX_LEAN)

A 4-bit ROCmFP4 quantization of microsoft/FastContext-1.0-4B-SFT, a lightweight repository-exploration subagent (Qwen3-4B backbone) for LLM coding agents.

Quantized and validated on AMD Strix Halo (Ryzen AI MAX+ 395 / Radeon 8060S, gfx1151) using hal0ai/amd-strix-halo-toolboxes πŸ› οΈ.

⚠️ Read this first β€” special runtime required

This file uses the experimental Q4_0_ROCMFP4 GGUF tensor format. It is NOT loadable by stock llama.cpp, Ollama, LM Studio, or any standard GGUF runtime. It runs only in the charlie12345/rocmfp4-llama fork. ROCmFP4 is a custom Codebook10 / finite-UE4M3 layout β€” it is not MXFP4 or NVFP4.

What's in this repo

File Size Format BPW
FastContext-4B-ROCmFP4-STRIX_LEAN.gguf 2.05 GiB Q4_0_ROCMFP4_STRIX_LEAN 4.38

STRIX_LEAN is a tensor-aware preset: norms stay f32, sensitive tensors keep higher precision, and the bulk of the weights use the dual/fast ROCmFP4 layouts.

Why ROCmFP4 here

On Strix Halo, token generation is memory-bandwidth-bound, so 4-bit weights decode much faster than BF16 while keeping quality intact for tool-calling.

Performance (llama-bench, ROCm0, FlashAttention on, Radeon 8060S)

Metric BF16 source ROCmFP4 STRIX_LEAN Ξ”
Size 7.49 GiB 2.05 GiB 3.65Γ— smaller
Prefill pp512 2388 t/s 2244 t/s ~same (compute-bound)
Decode tg128 25.6 t/s 73.7 t/s 2.88Γ— faster

Tool-calling quality (server-test-function-call.py, 5 multi-turn cases, greedy temp 0)

BF16 source ROCmFP4 STRIX_LEAN
Cases passed 2/5 4/5

In every case both models selected and ordered the correct tools β€” the only failures were "no final summary produced" after correct tool use, a stopping quirk shared by the BF16 source (not a quantization artifact). Takeaway: FP4 introduced no measurable tool-calling regression. A 5-case harness can't rank models finely, so read this as "quality preserved," not "FP4 > BF16."

How to run

Build the fork for your AMD GPU (see its README), then:

HSA_OVERRIDE_GFX_VERSION=11.5.1 \
GGML_HIP_ENABLE_UNIFIED_MEMORY=1 \
./build-strix-rocmfp4/bin/llama-server \
  -m FastContext-4B-ROCmFP4-STRIX_LEAN.gguf \
  -dev ROCm0 -ngl 999 -c 262144 -fa on --jinja

For scripted/non-interactive generation use llama-completion (this fork's llama-cli is interactive-only and rejects -no-cnv). FastContext supports up to 262K context.

How it was made

# 1. HF safetensors -> BF16 GGUF
python convert_hf_to_gguf.py ./FastContext-1.0-4B-SFT --outtype bf16 --outfile fc-bf16.gguf
# 2. BF16 -> ROCmFP4 (same fork binary the server uses)
llama-quantize fc-bf16.gguf FastContext-4B-ROCmFP4-STRIX_LEAN.gguf Q4_0_ROCMFP4_STRIX_LEAN

License & attribution

This repository redistributes a quantized derivative under the terms of the upstream MIT license.


About hal0ai

Built and benchmarked with hal0ai β€” local-first AI agent infrastructure tuned for AMD Strix Halo. The amd-strix-halo-toolboxes ship ready-to-run ROCm + ROCmFP4 container images so you can quantize and serve large models on a single unified-memory APU. If you're running agents on AMD silicon, come say hi. πŸ‘‹


A note from the author πŸ™‡

This is my first time doing any kind of custom model quantization or training β€” this release is very much a learning project. So if you spot something I got wrong, or have tips on presets, calibration, or quality testing, I'd genuinely appreciate the feedback β€” open a Community discussion and let me know.

I made this to run as a slot in hal0, alongside the main agent β€” a small, fast repository-exploration subagent that ROCmFP4 lets me keep resident on the Strix Halo without crowding out the bigger models sharing the same unified memory.

If you're tinkering with local agents on AMD hardware, come check out hal0 β€” would love to see what you build. πŸ™‚

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