gpt-oss-20b Β· Hermes-Agent tool finetune Β· GGUF

gpt-oss-20b Β· Hermes-Agent tool finetune Β· GGUF

GGUF quants for llama.cpp, Ollama, and LM Studio. Five quants shipped β€” pick by RAM budget.

  • Format β€” GGUF
  • Quants shipped β€” Q3_K_M, Q4_K_M, Q5_K_M, Q8_0, F16
  • Recommended β€” Q4_K_M for 16 GB RAM, Q8_0 for quality
  • Runtime β€” llama.cpp, Ollama, LM Studio, koboldcpp

What this is

A tool-use finetune of OpenAI's gpt-oss-20b for Hermes-Agent, a local agent framework that needs models which call tools reliably, follow multi-turn instructions, and don't argue with system prompts.

The base model is the 21B-parameter (3.6B active) Mixture-of-Experts release from OpenAI. This finetune preserves the Harmony chat template and the reasoning-effort knob, and improves:

  • Function-calling adherence (correct JSON, no commentary mid-call)
  • Long agent loops (10+ turns of tool β†’ observe β†’ plan)
  • System-prompt fidelity (respects role boundaries and refusal/allow-list rules)

It is not affiliated with NousResearch's Hermes model series. "Hermes-Agent" here refers to the local agent framework only.

Files

Quant Size Use case
Q3_K_M ~10.0 GB Tight RAM, lowest acceptable quality
Q4_K_M ~12.5 GB Best quality / size trade-off (default)
Q5_K_M ~14.5 GB Higher quality, modest size bump
Q8_0 ~22 GB Near-lossless
F16 ~41 GB Reference, no quantization

(Sizes are approximate; check the file list for exact bytes.)

Quickstart

llama.cpp

./llama-server \
  -hf fesalfayed/gpt-oss-20b-hermes_agent-tool-finetune_gguf:Q4_K_M \
  --port 1234 \
  -c 8192 \
  --jinja

Ollama

ollama run hf.co/fesalfayed/gpt-oss-20b-hermes_agent-tool-finetune_gguf:Q4_K_M

LM Studio

Search for fesalfayed/gpt-oss-20b-hermes_agent-tool-finetune_gguf in the Discover tab and pick a quant. Enable "Use Jinja chat template" in the model settings so Harmony renders correctly.

Hermes-Agent integration

Add a profile in ~/.hermes/config.yaml:

profiles:
  gpt-oss-20b-tools:
    provider: openai
    base_url: http://127.0.0.1:1234/v1   # LM Studio / vLLM / mlx_lm.server
    model: fesalfayed/gpt-oss-20b-hermes_agent-tool-finetune_gguf
    temperature: 0.7
    top_p: 0.95
    min_p: 0.1                            # important for MoE stability
    max_tokens: 8192
    tool_choice: auto

Then hermes profile use gpt-oss-20b-tools and the agent loop will route tool calls through this model.

Sampling

Param Value Why
temperature 0.7 balanced; drop to 0.2 for strict tool calls
top_p 0.95 standard nucleus
min_p 0.1 required for MoE β€” prevents dead-expert tokens
repetition_penalty 1.0 the model handles repetition itself

Harmony reasoning effort: set the system message to Reasoning: low|medium|high. high is roughly 3-4x more output tokens but noticeably better on multi-step tool plans.

Training

  • Base: openai/gpt-oss-20b
  • Method: LoRA SFT (rank 64, alpha 16) merged back into BF16
  • Frame: Unsloth + TRL on a single H100 (80 GB)
  • Data: ~42k tool-use traces from Hermes-Agent sessions, filtered for successful tool calls and clean JSON. No synthetic distillation.
  • Length: 8192 tokens, packing on
  • Loss: assistant-only, mask user/system/tool

The _16bit repo holds the merged BF16 weights. The _4bit, _mlx, and _gguf repos are quantizations of that checkpoint.

Limitations

  • Math and code-generation are unchanged from the base β€” this finetune optimizes the agent loop, not raw reasoning.
  • The model can over-call tools when given vague instructions. Add a "if you can answer directly, do so" line to the system prompt.
  • English only. Other languages were not in the training mix.
  • Not safety-tuned beyond what gpt-oss-20b already provides.

Other formats

  • BF16 reference β€” full precision, vLLM / Transformers
  • MXFP4 4-bit β€” fits a 16 GB GPU
  • MLX β€” Apple Silicon native
  • GGUF β€” llama.cpp / Ollama / LM Studio

License

Apache-2.0, inherited from the base model. No additional restrictions.

Citation

@misc{fesalfayed_gptoss20b_hermesagent_2025,
  author = {Fayed, Fesal},
  title  = {gpt-oss-20b Hermes-Agent tool finetune (gguf)},
  year   = {2025},
  url    = {https://huggingface.co/fesalfayed/gpt-oss-20b-hermes_agent-tool-finetune_gguf},
}
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