ThinkingCap — BottleCap AI

bottlecapai/ThinkingCap-Qwen3.8-27B-GGUF

GGUF / llama.cpp quantizations of bottlecapai/ThinkingCap-Qwen3.8-27B — the ThinkingCap finetune of Qwen3.8-27B that keeps the base model's answer quality while reasoning in far fewer tokens.

➡️ Full model description, evaluation results (multi-seed, statistically tested), the measured thinking-token reduction, recommended sampling params, and citation: see the main model card at bottlecapai/ThinkingCap-Qwen3.8-27B.

About GGUF and quantization

GGUF is a single-file model format for running LLMs locally with llama.cpp and compatible runtimes (Ollama, LM Studio, …). The quantized variants below store weights at reduced precision — e.g. ≈5.1 bits per weight for Q4_K_M instead of the 16-bit f16 source — cutting download size and memory severalfold at a small, measured quality cost.

The low-bit files are built with an importance matrix (activation statistics from a chat-templated calibration corpus) and a per-tensor precision layout: the attention projections of the full-attention layers and the linear-attention output projections stay at 6–8 bit while the feed-forward weights take the 4-bit hit.

Files

File Quant Size
ThinkingCap-Qwen3.8-27B-IQ4_XS.gguf IQ4_XS 15.5 GB
ThinkingCap-Qwen3.8-27B-Q4_K_M.gguf Q4_K_M 17.4 GB
ThinkingCap-Qwen3.8-27B-Q6_K.gguf Q6_K 23.9 GB
ThinkingCap-Qwen3.8-27B-Q8_0.gguf Q8_0 29.0 GB
ThinkingCap-Qwen3.8-27B-f16.gguf f16 54.7 GB
mmproj-ThinkingCap-Qwen3.8-27B-f16.gguf mmproj (vision) 931 MB

f16 is the unquantized source; Q8_0 and the smaller Q6_K showed no visible accuracy loss in our screen; Q4_K_M is the recommended size/quality balance for most local setups; IQ4_XS is the smallest variant that still tracks the f16 model closely.

Usage (llama.cpp)

# pull a specific quant straight from the Hub and chat
llama-cli -hf bottlecapai/ThinkingCap-Qwen3.8-27B-GGUF:Q4_K_M -p "Hi"

# or download one file and run it
huggingface-cli download bottlecapai/ThinkingCap-Qwen3.8-27B-GGUF ThinkingCap-Qwen3.8-27B-Q4_K_M.gguf --local-dir .
llama-cli -m ThinkingCap-Qwen3.8-27B-Q4_K_M.gguf -p "Hi"

Use the sampling settings from the main model card (the base model's recommended thinking-mode settings). Greedy decoding can loop; keep temperature at the recommended value.

Speculative decoding (MTP)

These GGUFs carry the model's MTP (multi-token-prediction) head, so llama.cpp can run self-speculative decoding for a decode speed-up — no separate draft model needed. Add --spec-type draft-mtp when serving:

llama-server -hf bottlecapai/ThinkingCap-Qwen3.8-27B-GGUF:Q4_K_M --spec-type draft-mtp --spec-draft-n-max 3

Requires a llama.cpp build with MTP support for this architecture (v0.4.1 or newer). It speeds up decoding at 4 parallel slots (see Decode speed and MTP under Expected performance); larger batches are untested. Runtimes that predate MTP support for this architecture may refuse to load the file (missing tensor blk.64…) — update the runtime.

Vision (image input)

ThinkingCap is a vision-language model. Image input needs the multimodal projector mmproj-ThinkingCap-Qwen3.8-27B-f16.gguf (in this repo) loaded alongside a text GGUF — the single f16 mmproj pairs with any of the quants above.

  • LM Studio / Jan / Ollama, …: download the mmproj-*.gguf from this repo; LM Studio auto-detects it and enables the image (🖼️) button.
  • llama.cpp CLI:
huggingface-cli download bottlecapai/ThinkingCap-Qwen3.8-27B-GGUF \
  ThinkingCap-Qwen3.8-27B-Q4_K_M.gguf mmproj-ThinkingCap-Qwen3.8-27B-f16.gguf --local-dir .
llama-mtmd-cli -m ThinkingCap-Qwen3.8-27B-Q4_K_M.gguf \
  --mmproj mmproj-ThinkingCap-Qwen3.8-27B-f16.gguf --image photo.jpg -p "Describe this image."
  • llama-server: add --mmproj mmproj-ThinkingCap-Qwen3.8-27B-f16.gguf to expose an OpenAI-compatible vision endpoint.

Expected performance

Accuracy and completion length against the bf16 weights on our quantization screen. Every row answers the same question subsets of five benchmarks, thinking at the chat template's default reasoning effort (xhigh), with sampled decoding (temperature 1.0, top_p 0.95, top_k 20, min_p 0.0) and a 65,536-token generation cap. The GGUFs are served by llama.cpp with the mmproj loaded for the RealWorldQA images; the bf16 reference is served by vLLM. acc is the mean over seeds, and the ± is the 95% interval over questions (each question averaged over its seeds first), so with 20–100 questions per benchmark it spans several points. AA-LCR answers are graded by Gemma-4-26B-A4B-it. median tokens / mean tokens = completion length (reasoning plus answer) over the questions; for GPQA-Diamond, the median and mean of the two seeds' values.

No quant differs from bf16 by more than that interval on any benchmark. This is a screen — small subsets, one seed on four of the five benchmarks — so read it as "no visible accuracy loss", not as a measured equivalence.

MMLU-Pro (reasoning) — 100 questions × 1 seed

config acc (mean ± 95% CI) median tokens mean tokens
ThinkingCap-Qwen3.8-27B bf16 (vLLM) 0.850 ± 0.070 144 1469
f16 0.870 ± 0.066 135 1508
Q8_0 0.880 ± 0.064 138 1448
Q6_K 0.840 ± 0.072 129 801
Q4_K_M 0.850 ± 0.070 147 1068
IQ4_XS 0.840 ± 0.072 157 1279

RealWorldQA (vision) — 100 questions × 1 seed

config acc (mean ± 95% CI) median tokens mean tokens
ThinkingCap-Qwen3.8-27B bf16 (vLLM) 0.830 ± 0.074 111 537
f16 0.830 ± 0.074 112 589
Q8_0 0.840 ± 0.072 107 666
Q6_K 0.790 ± 0.080 108 350
Q4_K_M 0.810 ± 0.077 102 370
IQ4_XS 0.810 ± 0.077 106 538

GPQA-Diamond (graduate-level science) — 60 questions × 2 seeds

config acc (mean ± 95% CI) median tokens mean tokens
ThinkingCap-Qwen3.8-27B bf16 (vLLM) 0.833 ± 0.088 1191 8378
f16 0.875 ± 0.072 1084 7357
Q8_0 0.858 ± 0.084 970 7773
Q6_K 0.867 ± 0.076 1160 7401
Q4_K_M 0.867 ± 0.076 1352 6327
IQ4_XS 0.900 ± 0.072 883 7025

IFBench (instruction following) — 40 questions × 1 seed

config acc (mean ± 95% CI) median tokens mean tokens
ThinkingCap-Qwen3.8-27B bf16 (vLLM) 0.700 ± 0.142 2039 6013
f16 0.725 ± 0.138 1929 5020
Q8_0 0.650 ± 0.148 2124 5103
Q6_K 0.650 ± 0.148 2129 4657
Q4_K_M 0.725 ± 0.138 2914 4886
IQ4_XS 0.725 ± 0.138 2725 4844

AA-LCR (long-context reasoning) — 20 questions × 1 seed

config acc (mean ± 95% CI) median tokens mean tokens
ThinkingCap-Qwen3.8-27B bf16 (vLLM) 0.650 ± 0.209 745 1587
f16 0.650 ± 0.209 828 1526
Q8_0 0.650 ± 0.209 1359 1358
Q6_K 0.700 ± 0.201 1100 1634
Q4_K_M 0.750 ± 0.190 1098 1358
IQ4_XS 0.700 ± 0.201 783 1441

Decode speed and MTP self-speculative decoding (MMLU-Pro) — 24 questions × 1 seed, llama.cpp on one H200, 4 parallel slots

config median tokens tok/s s / task MTP speedup accept_len (max 4)
f16 · standard 195 29.9 5.5 1.00×
f16 · MTP 213 52.7 3.7 1.76× 2.44
Q8_0 · standard 330 43.6 8.9 1.00×
Q8_0 · MTP 217 46.6 5.5 1.07× 2.52
Q6_K · standard 162 36.5 4.1 1.00×
Q6_K · MTP 224 48.9 6.3 1.34× 2.36
Q4_K_M · standard 241 37.5 6.4 1.00×
Q4_K_M · MTP 180 48.9 4.3 1.30× 2.33
IQ4_XS · standard 190 44.8 4.6 1.00×
IQ4_XS · MTP 243 54.1 4.0 1.21× 2.41

Where to find us

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Need even more efficiency? The open release is production-ready. Our enterprise versions go further — fewer thinking tokens still, tuned to your workload, at matched accuracy on your own tasks. Built for AI labs, inference providers and enterprises running models at scale. Deployed on your infrastructure, or in the cloud and region you choose. Talk to our team

License

ThinkingCap: PolyForm Small Business 1.0.0 + BottleCap personal-use grant (see LICENSE).

Upstream Qwen materials: Apache-2.0 (see NOTICE).

Commercial license: contact BottleCap AI.

Citation

If you use this model, please cite:

@misc{ThinkingCap-Qwen3.8-27B,
  title     = {bottlecapai/ThinkingCap-Qwen3.8-27B},
  author    = {Osusky, Adam and Lindauer, Jan and Jirkovsky, Adam and Mihal, Filip and Platek, Ondrej and Herel, David and Ihnatchenko, Luka and Bartek, Vojtech and Jirak, Jiri and Kubista, Daniel and Krus, Frantisek and Mikolov, Tomas},
  year      = {2026},
}
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