Qwen3.8-27B ยท KLX GGUF

27B reasoning from 6.2 GB. It still thinks.

License Format Runtime AIME

The smallest GGUFs of a 27B reasoning model usually stop reasoning: they loop, run out of tokens and miss easy problems. KLX files keep more of the model at every size. At 6.2 GB, the KLX file solves 53.8% of AIME 2025+2026; Unsloth's file of the same size solves 1.3%. Standard GGUF, no fine-tuning, no custom runtime.

โœจ Highlights

  • ๐Ÿง  53.8% on AIME 2025+2026 and 87.8% on MATH-500 from a 6.19 GB file. Unsloth's 6.19 GB file scores 1.3% and 32.6%.
  • ๐ŸŽฏ Near full quality from 10.9 GB. 94.2% AIME, 94.3% IFEval and 99.0% MATH-500, against 96.0%, 93.4% and 99.2% for full BF16 (about 54 GB).
  • ๐Ÿ”Œ Plain GGUF. Only standard llama.cpp tensor types: nothing to patch, no fork to build.

๐Ÿ“ฆ Pick your file

File Size AIME 2025+2026 IFEval MATH-500 Pick it for
Qwen3.8-27B-KLX-IQ1_S.gguf 6.19 GB 53.8 50.5 87.8 the smallest download
Qwen3.8-27B-KLX-IQ2_XXS.gguf 7.21 GB 82.7 88.5 98.4 the biggest step up per GB
Qwen3.8-27B-KLX-IQ2_XS.gguf 8.00 GB 89.4 93.5 97.8 strong reasoning at 8 GB
Qwen3.8-27B-KLX-IQ3_XXS.gguf 10.93 GB 94.2 94.3 99.0 near full quality
Qwen3.8-27B-KLX-IQ4_XS.gguf 14.25 GB 95.2 94.3 98.8 the closest to full quality
Qwen3.8-27B BF16, for reference about 54 GB 96.0 93.4 99.2

The file names give the size class. Each file mixes several standard tensor types.

๐ŸฅŠ Head to head

Same harness, same questions, paired differences in points with one standard error.

Size KLX file Against AIME 2025+2026 IFEval MATH-500
6.2 GB IQ1_S Unsloth UD-IQ1_S (6.19 GB) +52.5 ยฑ 4.9 +28.8 ยฑ 2.6 +55.2 ยฑ 2.5
7.2 GB IQ2_XXS Unsloth UD-IQ2_XXS, 19 Aug file (7.27 GB) +8.75 ยฑ 2.6 +8.3 ยฑ 1.9 +1.8 ยฑ 0.9
8 GB IQ2_XS ISTA GSQ-RCO IQ2_XS (8.42 GB) +0.2 ยฑ 1.5 -1.1 ยฑ 1.1 +0.2 ยฑ 0.8
8 GB IQ2_XS Unsloth UD-IQ2_S, 19 Aug file (8.37 GB) +1.0 ยฑ 1.4 +2.8 ยฑ 1.3 -0.8 ยฑ 0.8
10.9 GB IQ3_XXS Unsloth UD-IQ3_XXS (10.93 GB) +1.0 ยฑ 1.2 -0.4 ยฑ 0.8 +0.2 ยฑ 0.4
14.3 GB IQ4_XS Unsloth UD-IQ4_XS, 19 Aug file (14.25 GB) -0.6 ยฑ 0.9 -1.1 ยฑ 0.8 +0.2 ยฑ 0.5

From 10.9 GB up, both makers' files are close to full quality, and the benchmarks above cannot separate them.

Note, 12 Nov 2026: on 10โ€“11 Nov Unsloth replaced UD-IQ2_XXS, UD-IQ2_S and UD-IQ4_XS with new "Dynamic v3.1" files. The comparisons with those three files were measured against Unsloth's earlier files of 19 Aug 2026 and have not yet been repeated with the new ones. UD-IQ1_S and UD-IQ3_XXS are unchanged, so those comparisons are current. Setup, every score and the file hashes: BENCHMARKS.md.

๐Ÿš€ Run it with two commands

hf download KarLexAI/Qwen3.8-27B-GGUF Qwen3.8-27B-KLX-IQ1_S.gguf --local-dir .
llama-server -m Qwen3.8-27B-KLX-IQ1_S.gguf -ngl 99 -c 32768 --jinja

Then open http://localhost:8080 and chat. Thinking is on by default, and Qwen's sampling settings (temperature 1.0, top-k 20, top-p 0.95) are stored in the file.

๐Ÿ–ผ๏ธ Images

Qwen3.8 also reads images. Download the vision projector (about 0.9 GB) and add --mmproj:

hf download KarLexAI/Qwen3.8-27B-GGUF mmproj-F16.gguf --local-dir .
llama-server -m Qwen3.8-27B-KLX-IQ1_S.gguf --mmproj mmproj-F16.gguf -ngl 99 -c 32768 --jinja

mmproj-BF16.gguf works the same way, with any of the files above (we tested IQ1_S and IQ4_XS on llama.cpp commit 351025ec).

๐Ÿงพ The fine print

  • Post-training quantization of Qwen/Qwen3.8-27B. No fine-tuning. The architecture, tokenizer and chat template are unchanged; the multi-token prediction (MTP) head is not included. The vision encoder is in the separate mmproj files, unquantized (F16 and BF16), converted with upstream llama.cpp.
  • Every number above comes from one harness on stock llama.cpp, in thinking mode with Qwen's sampler.
  • Apache-2.0, like the base model. See NOTICE.

Made by KarLex AI. If these files save you memory, a โค๏ธ on this repo helps others find them.

Not affiliated with Qwen, Unsloth or ISTA.

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