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📝 [Blog post](https://huggingface.co/blog/lightonai/lighton-rerank)
PW-0.8B | LW-0.8B | PW-2B | LW-2B | PW-4B | LW-4B
--- ## About the LightOn-rerank family Production retrieval pipelines usually need two rerankers: one for text passages and one for visual documents (PDF pages, slides, scans). **LightOn-rerank** models are *unified* cross-encoder rerankers: a single model scores both text passages and document page images against a query, on top of any first-stage retriever (BM25, dense embeddings, or ColPali-family late-interaction models). The models are built on Qwen3.5 backbone (hybrid linear + full attention) and jointly fine-tuned on text and visual reranking data with mixed-modality batches (LoRA, merged into the released weights). Training data is English-only; French performance transfers zero-shot from the multilingual backbone. The family comes in two scoring flavours × three sizes (0.8B / 2B / 4B): - **PW (pointwise)**: each candidate is scored independently. The model judges whether the document answers the query, and the score is `logit("Yes") − logit("No")`. One forward pass per candidate and no generation. - **LW (listwise)**: generative listwise ranking, where 4 candidates are placed in a single prompt and the model generates a permutation (`[2] > [4] > [1] > [3]`). Larger candidate pools are ranked with a sliding window (window 4, stride 2, bottom-to-top). Cross-document attention makes LW markedly stronger on hard visual reranking, and unlike pointwise scoring it keeps improving with backbone size. **LightOn-rerank-PW-4B** is the 4B pointwise member of the family. On visual reranking it ties the 2B pointwise model (59.80 vs 59.87 nDCG@10 on ViDoRe V3): direct evidence that independent Yes/No scoring is a capacity bottleneck that extra parameters cannot fix. On text BEIR, however, it posts the strongest scores in the family (50.19 decontaminated mean). For 4B-budget vision-heavy deployments, [LightOn-rerank-LW-4B](https://huggingface.co/lightonai/LightOn-rerank-LW-4B) is +4.9 nDCG@10 at the same size. ## Results **ViDoRe V3** (visual document reranking, 8 domains × EN/FR queries), overall nDCG@10, ColQwen2.5-v0.2 first stage, retrieve 100 / rerank 100. All models, including baselines, were re-evaluated under this same two-stage protocol, so numbers are mutually comparable but not comparable to vendor-reported end-to-end results. | Model | Params | Scoring | ViDoRe V3 overall nDCG@10 | |---|---|---|---| | [LightOn-rerank-LW-4B](https://huggingface.co/lightonai/LightOn-rerank-LW-4B) | 4.5B | listwise | 64.69 | | *Qwen3-VL-Reranker-8B* | *8B* | *pointwise (pooling)* | *64.23* | | [LightOn-rerank-LW-2B](https://huggingface.co/lightonai/LightOn-rerank-LW-2B) | 2.2B | listwise | 62.66 | | [LightOn-rerank-PW-2B](https://huggingface.co/lightonai/LightOn-rerank-PW-2B) | 2.2B | pointwise | 59.87 | | **LightOn-rerank-PW-4B (this model)** | 4.5B | pointwise | **59.80** | | *jina-reranker-m0* | *2.4B* | *pointwise* | *59.40* | | *Qwen3-VL-Reranker-2B* | *2B* | *pointwise (pooling)* | *59.18* | | [LightOn-rerank-LW-0.8B](https://huggingface.co/lightonai/LightOn-rerank-LW-0.8B) | 0.85B | listwise | 58.25 | | *MonoQwen2-VL-v0.1* | *2B* | *pointwise* | *57.76* | | *First-stage only (ColQwen2.5, no rerank)* | — | — | *55.60* | | [LightOn-rerank-PW-0.8B](https://huggingface.co/lightonai/LightOn-rerank-PW-0.8B) | 0.85B | pointwise | 48.20 | ### ViDoRe V3 detail (nDCG@10, ColQwen2.5 first stage, rerank-100) | Domain | EN | FR | |---|---|---| | finance_en | 70.98 | 68.54 | | finance_fr | 45.96 | 37.92 | | computer_science | 79.25 | 74.71 | | hr | 58.67 | 53.54 | | energy | 70.95 | 72.36 | | industrial | 60.54 | 47.33 | | pharmaceuticals | 68.11 | 67.70 | | physics | 44.46 | 35.77 | | **mean** | **62.37** | **57.23** | Overall nDCG@10: **59.80** (EN 62.37 / FR 57.23). ### BEIR results (text reranking) 13 datasets, nDCG@10, BM25 first stage, retrieve 100 / rerank 100, same protocol as all other family members. ⚠️ marks datasets in the text training mix (NQ, MSMARCO); the decontaminated mean excludes them. | Dataset | nDCG@10 | |---|---| | fever | 81.77 | | scifact | 76.13 | | trec-covid | 79.38 | | hotpotqa | 70.79 | | nq ⚠️ | 61.03 | | dbpedia | 44.21 | | arguana | 41.47 | | fiqa | 40.91 | | msmarco ⚠️ | 39.20 | | nfcorpus | 37.41 | | touche-2020 | 35.68 | | climate-fever | 26.46 | | scidocs | 17.87 | | **Mean (13)** | **50.18** | | **Decontaminated mean (11, excl. ⚠️)** | **50.19** | This is the best text result in the LightOn-rerank family (2B pointwise: 49.13, 4B listwise: 48.33 decontaminated mean). Pointwise plateaus with scale on vision but not on text. If your workload is text-dominant and you have the 4B budget, this is the family's strongest text reranker. ## Model Details - **Model type:** multimodal cross-encoder reranker (**pointwise**: each candidate is scored independently as `logit("Yes") − logit("No")`) - **Base model:** [Qwen/Qwen3.5-4B](https://huggingface.co/Qwen/Qwen3.5-4B) (Qwen3.5 hybrid linear + full attention VLM) - **Parameters:** ≈4.5B (bfloat16, 9.1 GB) - **Inputs:** query (text) + candidate document(s): text passage **or** page image - **Fine-tuning:** joint text+vision LoRA (r=32, α=32, rsLoRA, merged into the released weights), mixed-modality batches (2 text + 2 vision groups per micro-batch), vision loss weight 1.3, lr 1e-4, 1 epoch (465 steps) - **Data:** same 213k groups as the listwise models — 107k text groups (NQ, TriviaQA, MS MARCO; each a `[pos, neg_0, neg_1, neg_2]` 4-list with hard negatives mined via the NV-Retriever approach with GTE-ModernBERT) + 106k vision groups (ColPali train set with negatives mined by Nomic). For pointwise training each group is flattened into (query, document, Yes/No) triples. - **Languages:** English (training), French (zero-shot transfer) - **Requirements:** `transformers >= 5.4.0` (`qwen3_5` architecture); `sentence-transformers >= 5.4.0` for the CrossEncoder usage ## Usage: pointwise reranking Each candidate is scored independently as `logit("Yes") − logit("No")` at the first generated position; sort candidates by descending score. The model was trained with a fixed system prompt and user template: use them verbatim for best results. ### Using Sentence Transformers Install Sentence Transformers (`>= 5.4.0`): ```bash pip install "sentence-transformers[image]" ``` The trained system prompt and user templates are baked into the bundled `reranker` chat template — including the non-thinking generation prompt, so no `enable_thinking` handling is needed — and query-document pairs are formatted correctly out of the box: ```python from sentence_transformers import CrossEncoder model = CrossEncoder("lightonai/LightOn-rerank-PW-4B") query = "What is late interaction in neural information retrieval?" documents = [ "ColBERT computes token-level query-document interactions at search time...", "The Eiffel Tower is located on the Champ de Mars in Paris.", ] pairs = [(query, doc) for doc in documents] scores = model.predict(pairs) print(scores) # [-3. -8.0625] rankings = model.rank(query, documents) print(rankings) # [{'corpus_id': 0, 'score': -3.0}, {'corpus_id': 1, 'score': -8.0625}] ``` To rerank **page images**, pass a `PIL.Image` (or an image URL or file path string) as the document. Text and image candidates can be mixed in the same call: ```python from PIL import Image pairs = [ (query, Image.open("page_1.png")), (query, "https://example.com/page_2.png"), (query, "A text passage candidate for the same query."), ] scores = model.predict(pairs) ``` Scores are raw `logit("Yes") − logit("No")` differences. You can map them to 0...1 probabilities with `model.predict(pairs, activation_fn=torch.nn.Sigmoid())`. ### Using Transformers ```python import torch from transformers import AutoModelForImageTextToText, AutoProcessor model_id = "lightonai/LightOn-rerank-PW-4B" model = AutoModelForImageTextToText.from_pretrained( model_id, dtype=torch.bfloat16, attn_implementation="flash_attention_2", # optional, remove if flash-attn is not installed device_map="cuda", ).eval() processor = AutoProcessor.from_pretrained(model_id) processor.tokenizer.padding_side = "left" # scores are read at the last position YES_TOKEN_ID = 9175 # "Yes" NO_TOKEN_ID = 2665 # "No" SYSTEM_PROMPT = "Judge whether the document is relevant to the query. Answer Yes or No." USER_TEMPLATE = ( "Given a query, determine if the document is relevant. " "The query is: {query}\n\nDocument: {doc}" ) query = "What is late interaction in neural information retrieval?" documents = [ "ColBERT computes token-level query-document interactions at search time...", "The Eiffel Tower is located on the Champ de Mars in Paris.", ] texts = [ processor.apply_chat_template( [ {"role": "system", "content": SYSTEM_PROMPT}, {"role": "user", "content": USER_TEMPLATE.format(query=query, doc=doc)}, ], tokenize=False, add_generation_prompt=True, enable_thinking=False, # REQUIRED on the 4B backbone (thinking on by default) ) for doc in documents ] inputs = processor( text=texts, return_tensors="pt", padding=True, truncation=True, max_length=2048 ).to(model.device) with torch.inference_mode(): logits = model(**inputs).logits[:, -1] scores = (logits[:, YES_TOKEN_ID] - logits[:, NO_TOKEN_ID]).tolist() # [-3.0, -8.0625] ranked = sorted(zip(scores, documents), reverse=True) ``` To score a **page image** instead of a text passage, replace the user message with: ```python VISION_TEMPLATE = "Given a query, determine if the document image is relevant. The query is: {query}" {"role": "user", "content": [ {"type": "image", "image": page_image}, # PIL.Image {"type": "text", "text": VISION_TEMPLATE.format(query=query)}, ]} ``` and pass `images=[page_image, ...]` to the processor call (keep the same system prompt). ### Serving with vLLM ```bash vllm serve lightonai/LightOn-rerank-PW-4B --trust-remote-code --max-model-len 16384 ``` ```python resp = client.chat.completions.create( model="lightonai/LightOn-rerank-PW-4B", messages=messages, # same system + user messages as above max_tokens=1, logprobs=True, top_logprobs=20, temperature=0.0, extra_body={"chat_template_kwargs": {"enable_thinking": False}}, # REQUIRED ) top = resp.choices[0].logprobs.content[0].top_logprobs lp = {t.token: t.logprob for t in top} score = lp.get("Yes", -100.0) - lp.get("No", -100.0) ``` Full-page document images can exceed 8k tokens, so keep `--max-model-len` at 16384 or higher when reranking page images. ## Notes & limitations - **Thinking must be disabled for scoring.** Qwen3.5-4B's chat template enables `