Qwen3.8-27B ByteShape IQ4_XS-3.84bpw — ASCII-P1M vocab

ByteShape's Qwen3.8-27B IQ4_XS-3.84bpw (ShapeLearn per-tensor quantization) with its vocabulary pruned to ASCII plus math/typography symbols, using bsaleh03/ASCII-Condensed-prune-tools (--policy P1M).

English and code only. See Limitations.

File Qwen3.8-27B-ByteShape-IQ4_XS-3.84bpw-ASCII-P1M.gguf
Size 12.25 GB (source 13.08 GB)
Vocab 129,272 tokens (source 248,320)
sha256 d533c568ba028fb7bc24d646d9f0259341a388fb2535e559fd0bc62275a55a4d
Source sha256 89434f23dc89c5f990894e3fe9fdad19d88c370f0d3638a176f29933f218b78b
Architecture qwen35 (hybrid Gated DeltaNet + attention), 65 blocks, MTP head kept
Parameters Qwen3.8-27B (27.3B). The Hub shows 26.1B because it counts tensor shapes, and the pruned vocab removes 119,048 rows from both token_embd and output (~1.22B parameters). Every transformer weight is unchanged.

What changed

Only token_embd.weight (IQ4_XS, 0.675 → 0.352 GB) and output.weight (Q6_K, 1.043 → 0.543 GB) were touched. Rows are gathered in quantized space: no dequantize/requantize, so every kept row is bit-identical to the source. The tokenizer arrays and merges were rewritten and the special-token ids remapped. The 256 byte-fallback tokens, all specials and all partial-UTF-8 fragments are kept, so any text can still be tokenized.

verify_prune.py --policy P1M passed every check:

  • all 864 non-vocab tensors byte-identical to the source
  • sampled vocab rows identical to their source rows
  • metadata preserved
  • kept set exactly what P1M specifies

Tool commit: 376a426d5c6b30f28e03c6efaa9edcf85048773f.

Measurements

Measured on an RTX 5060 Ti 16 GB with llama.cpp v0.4.1.

Perplexity: ctx 4096, 30 chunks, f16 KV. Lower is better, and the figures are deterministic, so they compare exactly across rows.

model code (mixed TS/JS project source) code, ASCII-only lines wikitext-2
ByteShape IQ4_XS-3.84bpw (source) 1.6671 1.6490 5.9480
this file 1.7156 1.6488 5.9612
Unsloth UD-IQ4_XS (reference) 1.6583 — 5.8322

On ASCII-only text the prune costs nothing (1.6488 vs 1.6490). The +2.9% on the mixed code corpus comes entirely from its 1.27% non-ASCII characters, mostly Bangla string literals.

Context and speed: whole model on GPU, q4_0 KV cache, -ub 512, MTP off.

ctx VRAM allocated prefill decode
96k 13,952 MiB 939 t/s 28.7 t/s
128k 14,391 MiB 939 t/s 28.8 t/s
160k 14,873 MiB 895 t/s 27.7 t/s

A 16 GB card with a light desktop fits about 128k of context; 160k needs a nearly idle desktop.

Agentic coding eval (10 executable tasks, thinking on, temp 1.0 / top_p 0.95 / top_k 20): 8/10, 18,381 tokens total. One of the two failures is a grading artifact: the answer ended with a usage-example code block, which the grader took for the solution.

Tool calling and mid-conversation system messages work with a patched chat template (see below).

Usage

llama-server -m Qwen3.8-27B-ByteShape-IQ4_XS-3.84bpw-ASCII-P1M.gguf \
  -c 131072 -ngl 99 -fa on --cache-type-k q4_0 --cache-type-v q4_0 \
  --jinja --temp 1.0 --top-p 0.95 --top-k 20 --min-p 0.0
  • MTP: the head is still in the file; add --spec-type draft-mtp --spec-draft-n-max 2 if you have the VRAM for the draft context.
  • Claude Code and similar agents: the stock Qwen3.8 template raises System message must be at the beginning. on mid-conversation system messages. Patch that branch to render them as normal system blocks.

Limitations

  • Non-Latin text breaks. Scripts outside ASCII and the P1M symbol set (Bangla, CJK, Arabic, Cyrillic, …) fall back to one token per UTF-8 byte. The model was never trained on those byte sequences, so it reads them as garbled text. A Bangla prompt got a romanized reply saying the input looked garbled; the full-vocab model answers it correctly. For multilingual use, take the source file instead.
  • Accented Latin (é, ü, ñ) is not in P1M either, so it also degrades.
  • Not affiliated with ByteShape or the Qwen team. All numbers above come from one machine.

Credits

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