prose-rewriter-4b-v2.1

A paragraph-level prose rewriter: it takes prose written by a large model and re-renders it to be more human, preserving the semantics it was given.

Qwen/Qwen3-4B-Base with a rank-32 LoRA merged in at strength 1.20.

Invented people, mostly gone. v2 would would invent a person where there was none -- She offered a trembling smile -> She gave him a trembling smile. Training pairs that teach this are now rejected: the input names one gender and the target brings in the other. On 400 single-gender roleplay paragraphs the rate falls from 1.3% to 0.4%.

Fixed dialogues randomly dropping double-quotes.

More published fiction. Professionally edited novels are now 40% of the target side, up from 33%.

It also edits harder than v2, at 1.20 against v2's 1.10: more of the input's slop goes, and the rewrite departs further from the input. See Evaluation.

Variants

Path	Format	Use with
/	safetensors bf16, qwen3 arch	transformers
GGUF/prose-rewriter-4b-v2.1-Q8_0.gguf	GGUF Q8_0, 4.69 GB	llama.cpp / llama-cpp-python
GGUF/prose-rewriter-4b-v2.1-Q4_K_M.gguf	GGUF Q4_K_M, 2.72 GB	llama.cpp / llama-cpp-python

The quants carry the chat template and stop on <|im_end|>, and the adapted output head is kept separate from the token embeddings, stored at Q8_0.

Prompt format

<|im_start|>source
{paragraph}<|im_end|>
<|im_start|>rewrite

The chat template in this repo builds exactly that string, byte for byte, from one message:

messages = [{"role": "source", "content": paragraph}]
tok.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)

It is not a chat model. Every message is rendered as the source paragraph, so a runtime that probes the template with a user message still gets a valid prompt. Send one message per call.

Serving recipe

Sampled at temperature=0.9, top_p=0.9. Temperature 0.9 has been tested internally to be the most optimal value. It's recommended you use this.

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer

repo = "chartreuse-verte/prose-rewriter-4b-v2.1"
tok = AutoTokenizer.from_pretrained(repo)
model = AutoModelForCausalLM.from_pretrained(repo, dtype=torch.bfloat16, device_map="cuda").eval()

def rewrite(paragraph):
    text = tok.apply_chat_template(
        [{"role": "source", "content": paragraph}],
        tokenize=False, add_generation_prompt=True,
    )
    ids = tok(text, return_tensors="pt", add_special_tokens=False).input_ids.to(model.device)
    out = model.generate(ids, max_new_tokens=512, do_sample=True, temperature=0.9, top_p=0.9)
    return tok.decode(out[0, ids.shape[1]:], skip_special_tokens=True).strip()

Same thing under llama.cpp. The role is source, which no chat API models, so build the string yourself; <|im_end|> stops it:

llama-cli -m GGUF/prose-rewriter-4b-v2.1-Q8_0.gguf -no-cnv -n 512 --temp 0.9 --top-p 0.9 \
  -p '<|im_start|>source
{paragraph}<|im_end|>
<|im_start|>rewrite
'

Input length

The training pool's median input is 37 words and 80% of it is under 70, so serve it on anything from a full sentence up.

The practical floor is about 15 words. Below it the failure mode is padding, cutting and fabrication rather than gibberish. Below 80 bytes, pass the text through unchanged.

Evaluation

Both releases measured as they ship -- v2 baked at strength 1.10, v2.1 at 1.20 -- on 365 held-out paragraphs of LLM-written prose that neither model saw in training, at temperature=0.9, top_p=0.95, three swipes each. 1,095 generations an arm.

Pronoun invention numbers for this release:

	v2	v2.1
a gendered pronoun the input never licensed	1.2%	0.8%
... belonging to the other gender	1.2%	0.8%
a proper noun the input does not have	0.2%	0.3%

Paired over the 400 inputs, none of these separates at this sample size; the cross-gender drop reads t = -1.2. The 1.7B release, on the same set and the same gate, separates cleanly -- see prose-rewriter-1.7b-v2.1.

Structural, on the 365 paragraphs:

	v2	v2.1
words changed	41.5%	44.0%
passed through unchanged	2.8%	3.1%
near-verbatim outputs	1.7%	1.4%
below the training edit floor	40.3%	35.4%
sentence count moved	76.4%	75.5%
sentence-length variety vs input	+0.114	+0.115
words kept from the input	0.643	0.616
length preserved	0.885	0.851
truncated below 0.75x	16.2%	23.7%
repeated 3-grams	0.005	0.005

Paired over the 303 inputs of 51-90 words, v2.1 changes more words (t = +2.5) and falls below the edit floor less often (t = -2.1). It keeps fewer of the input's words (t = -4.2), holds less of its length (t = -5.4) and truncates below 0.75x more often (t = +3.8). No other column separates the two.

Unsupported content -- a sentence in the rewrite the input does not entail, scored by NLI with the input alone as the premise:

	v2	v2.1
unsupported sentences, mean per rewrite	10.8%	12.7%
unsupported sentences, all rewrites	9.9%	11.5%
coverage of the input (reverse entailment)	0.519	0.487

On the same 303 inputs the unsupported rate rises (t = +2.4) and coverage falls (t = -2.8).

The register numbers on the same paragraphs, against the input:

	input	v2	v2.1	human corpus
banned constructions /1k	7.52	3.30	2.51	0.00
slop lexicon density	0.081	0.051	0.048	0.019
purple score	0.498	0.320	0.314	--

Paired over all 365 inputs, banned constructions fall (t = -3.7) and lexicon density falls (t = -2.7). Purple does not separate. Banned constructions also appear in fewer rewrites: 14.7% against v2's 19.2%.

Dialogue: the number of spoken lines changes on 0.8% of rewrites against v2's 2.4% (t = -2.7), and of the rewrites whose input carried quoted speech, 1.0% lost the quotes entirely against v2's 3.0%.

Markup round-trip on 365 tagged paragraphs -- every marker handed back in order, with the same counts: 80.0% for v2, 79.5% here.

A note on strength

Every number above is measured at the strength the release is baked at, which is not the same as measuring the adapter. LoRA strength is spent at merge time (W + (B @ A) * 2.40 here), and the metrics move with it: read at the adapter's natural 1.0 this same checkpoint is a materially different artifact.

v2 ships at 1.10 and this at 1.20, so part of every difference above is the strength and not the pool.

Training

Corrupt forward, train backward. The human paragraph is the target; an on-policy LLM manufactures the input by slop-ifying it.

The target side is human prose: published contemporary literary fiction, r/WritingPrompts (Mollymo/Human-to-AI-writing), AO3 (midwestern-simulation-active/ao3_random_subset), a scrape of bluemoonroleplaying.com -- the only human writing in the pool already in the deployment's own register -- and a sliver of fanfiction.net (atom-in-the-universe/fanfics-10k-10k).

The input side is manufactured from those targets, weighted and share-capped so that no single generator's tics dominate:

pool axis	composition
rows	15,794 over 11,476 distinct target paragraphs
corruption band	medium 35%, heavy 31%, light 30%, identity/no-op 3%, curated real slop 1%
len_mode	match only
markup	15% of rows, identical on both sides
kind	prose 91%, dialogue 8%, structural no-ops 1%
target source	published fiction 40%, r/WritingPrompts 29%, AO3 21%, roleplay forum 8%, other 2%

Pairs pass invariant gates before they reach the GPU: POV, tense, who is in the scene, the gender of who is in the scene, the number of spoken lines, grammatical correctness on the target side, content recall stratified by target length, and NLI entailment both ways. Two further screens shape what reaches training -- a floor on how much a pair actually changes, and a floor on the sentence-length variety of the target, applied at a higher threshold for long paragraphs than short ones.

Loss on the target paragraph only. Everything before rewrite is masked.

LoRA	r=32, alpha=64, dropout 0.05
target modules	q, k, v, o, gate, up, down, and lm_head
trainable	71,004,160 params (1.73%)
schedule	2 epochs, lr 1e-4 cosine, batch 8 × accum 4, seq 2048
steps	950 on one RTX 3090

The merge

Merged at strength 1.20. Rank 32 with alpha 64 is a LoRA scaling of 2.0, so the effective scaling is 2.40: W + (B @ A) * 2.40. Merged in float32, stored bfloat16.

lm_head is adapted, and Qwen3-4B-Base ties lm_head.weight to embed_tokens.weight. This checkpoint is untied: the merged output head is stored separately and the input embeddings are bit-identical to the base model's, which is what training assumed. config.json says tie_word_embeddings: false and it means it. Do not re-tie it, and if you convert to another format, check that the head survived.

Limitations

• Not an instruct model. It has one job and one prompt. There is nothing to ask it.
• Works on fictional prose only. May not work on technical documentation.
• One paragraph per call. Longer input degrades; split it.
• Still invents people occasionally. The phantom pronoun is down, not gone, and invented proper nouns went up. Check the output when the cast matters.
• Shorter than v2. It drops below 0.75x the input's length on 23.7% of paragraphs against v2's 16.2%. Usually that is the slop going; check the output when length matters.
• Will not pass AI detectors. Pangram and such will still know because this model preserves word choices and certain sentence structures.
• English only, narrative register (third and first person fiction, dialogue with quoted speech).
• Short input pads, cuts and invents. The floor is about 15 words. See Input length.
• Repeats a noun sooner than an LLM would. Human prose reuses a plain noun where generated prose uses a synonym, and this model has learned that habit.

License

The weights in this repository are released under the GNU Affero General Public License, version 3. The full text is in LICENSE.

This is a derivative of Qwen/Qwen3-4B-Base, which is licensed under Apache License 2.0. That license is preserved and its terms continue to apply to the base weights this model was built from; the AGPL covers the combined work as distributed here. Apache-2.0 is one-way compatible with AGPLv3, which is what makes this combination possible.

If you run a modified version of this model as a network service, AGPL section 13 requires you to offer the corresponding source of your modifications to its users.