Instructions to use ThakiCloud/ChainCheck-Judge-Qwen3.5-4B with libraries, inference providers, notebooks, and local apps. Follow these links to get started.

Libraries

How to use ThakiCloud/ChainCheck-Judge-Qwen3.5-4B with Transformers:

# Use a pipeline as a high-level helper
from transformers import pipeline

pipe = pipeline("text-generation", model="ThakiCloud/ChainCheck-Judge-Qwen3.5-4B")
messages = [
    {
        "role": "user",
        "content": [
            {"type": "image", "url": "https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/p-blog/candy.JPG"},
            {"type": "text", "text": "What animal is on the candy?"}
        ]
    },
]
pipe(text=messages)

# pip install -U transformers accelerate
# Load model directly
from transformers import AutoProcessor, AutoModelForMultimodalLM

processor = AutoProcessor.from_pretrained("ThakiCloud/ChainCheck-Judge-Qwen3.5-4B")
model = AutoModelForMultimodalLM.from_pretrained("ThakiCloud/ChainCheck-Judge-Qwen3.5-4B", device_map="auto")
messages = [
    {
        "role": "user",
        "content": [
            {"type": "image", "url": "https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/p-blog/candy.JPG"},
            {"type": "text", "text": "What animal is on the candy?"}
        ]
    },
]
inputs = processor.apply_chat_template(
	messages,
	add_generation_prompt=True,
	tokenize=True,
	return_dict=True,
	return_tensors="pt",
).to(model.device)

outputs = model.generate(**inputs, max_new_tokens=256)
print(processor.decode(outputs[0][inputs["input_ids"].shape[-1]:]))

Notebooks
Google Colab
Kaggle
Local Apps Settings

vLLM

How to use ThakiCloud/ChainCheck-Judge-Qwen3.5-4B with vLLM:

Install from pip and serve model

# Install vLLM from pip:
pip install vllm
# Start the vLLM server:
vllm serve "ThakiCloud/ChainCheck-Judge-Qwen3.5-4B"
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:8000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "ThakiCloud/ChainCheck-Judge-Qwen3.5-4B",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Use Docker

docker model run hf.co/ThakiCloud/ChainCheck-Judge-Qwen3.5-4B

SGLang

How to use ThakiCloud/ChainCheck-Judge-Qwen3.5-4B with SGLang:

Install from pip and serve model

# Install SGLang from pip:
pip install sglang
# Start the SGLang server:
python3 -m sglang.launch_server \
    --model-path "ThakiCloud/ChainCheck-Judge-Qwen3.5-4B" \
    --host 0.0.0.0 \
    --port 30000
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:30000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "ThakiCloud/ChainCheck-Judge-Qwen3.5-4B",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Use Docker images

docker run --gpus all \
    --shm-size 32g \
    -p 30000:30000 \
    -v ~/.cache/huggingface:/root/.cache/huggingface \
    --env "HF_TOKEN=<secret>" \
    --ipc=host \
    lmsysorg/sglang:latest \
    python3 -m sglang.launch_server \
        --model-path "ThakiCloud/ChainCheck-Judge-Qwen3.5-4B" \
        --host 0.0.0.0 \
        --port 30000
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:30000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "ThakiCloud/ChainCheck-Judge-Qwen3.5-4B",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Docker Model Runner
How to use ThakiCloud/ChainCheck-Judge-Qwen3.5-4B with Docker Model Runner:
```
docker model run hf.co/ThakiCloud/ChainCheck-Judge-Qwen3.5-4B
```

ChainCheck-Judge-Qwen3.5-4B

An evidence-sufficiency judge for RAG whose score tracks whether the reasoning chain is intact, not merely whether the passages were edited (2Wiki chain selectivity +0.136 [+0.058, +0.214] → +0.376 [+0.322, +0.437] against the same-size zero-shot model).

Given a question and retrieved passages, the model returns a log-odds score for "the passages together are sufficient to answer". It is Qwen/Qwen3.5-4B with a LoRA trained on ChainCheck counterfactual triplets, merged back into the base as a single set of full bf16 weights (the base's MTP tensors are carried over unchanged, so MTP speculative decoding still works).

Why it matters: an ordinary sufficiency benchmark only asks whether a system separates untouched passages from broken ones, and a near-perfect score there can come from reacting to any edit. In a RAG pipeline that means an edited-but-valid context gets flagged and a subtly broken chain gets through. ChainCheck adds a matched control that separates the two.

Measurements (2026-10-05, conditions stated)

Same prompt, same scoring pipeline, one B200 GPU. Pairs a 27B model answers closed-book are excluded. Intervals are 95% pair-bootstrap (2,000 resamples). Σ = chain effect − |edit effect|; a lower bound above zero means the score reacts more to breaking the chain than to editing the passages.

Axis	zero-shot base	This model
2Wiki nominal AUC, real entities (n=295 pairs)	0.932	0.983
Chain selectivity Σ, MuSiQue test, real (n=324)	+0.028 [-0.052, +0.111]	+0.185 [+0.145, +0.228]
Chain selectivity Σ, MuSiQue confirmation, real (n=122)	+0.090 [-0.049, +0.222]	+0.098 [+0.041, +0.156]
Chain selectivity Σ, 2Wiki replication, real (n=295)	+0.136 [+0.058, +0.214]	+0.376 [+0.322, +0.437]
Chain selectivity Σ, MuSiQue test, synthetic (n=224)	+0.188 [+0.094, +0.277]	+0.027 [+0.009, +0.049]
Chain selectivity Σ, MuSiQue confirmation, synthetic (n=98)	+0.327 [+0.194, +0.378]	-0.010 [-0.031, +0.000]
Chain selectivity Σ, 2Wiki replication, synthetic (n=141)	+0.319 [+0.220, +0.411]	+0.071 [+0.028, +0.114]

Honest caveats:

The tuned model tends to score the consistently edited context (B) above the untouched one (A): the edit effect is negative in every cell (range -0.500 to -0.114). Σ subtracts |EE|, so this is already penalised in the table, but the score is not edit-invariant.
With synthetic replacement entities, chain selectivity is lower after tuning than for the same-size zero-shot model on MuSiQue test (+0.188 → +0.027), MuSiQue confirmation (+0.327 → -0.010), 2Wiki replication (+0.319 → +0.071). The gains are on real entities; do not assume they transfer to entities the model has never seen.
2Wiki was never used for training or model selection, and MuSiQue confirmation is a held-out slice built after the protocol was frozen. The release gate (2Wiki Σ lower bound > 0 on real and synthetic, MuSiQue test real Σ lower bound > 0, 2Wiki nominal no more than 0.02 below zero-shot) was fixed before any score was seen.

Usage

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer

repo = "ThakiCloud/ChainCheck-Judge-Qwen3.5-4B"
tok = AutoTokenizer.from_pretrained(repo)
model = AutoModelForCausalLM.from_pretrained(repo, torch_dtype=torch.bfloat16, device_map="auto")

SYSTEM = ("You are a strict evidence auditor for a retrieval-augmented QA system. "
          "Decide whether the given passages, taken together, contain enough information "
          "to fully answer the question. Related-but-insufficient passages do NOT count.")
USER = ("Question:\n{query}\n\nPassages:\n{passages}\n\n"
        "Do the passages together contain sufficient evidence to answer the question? "
        "Answer with a single word: yes or no.")

yes = [i for i in range(len(tok)) if tok.decode([i]).strip().lower() in {"yes", "y"}]
no = [i for i in range(len(tok)) if tok.decode([i]).strip().lower() in {"no", "n"}]

def sufficiency_score(query, passages):
    body = "\n\n".join(f"[{i + 1}] {p[:4000]}" for i, p in enumerate(passages))
    msgs = [{"role": "system", "content": SYSTEM}, {"role": "user", "content": USER.format(query=query, passages=body)}]
    text = tok.apply_chat_template(msgs, tokenize=False, add_generation_prompt=True, enable_thinking=False)
    ids = tok(text, return_tensors="pt", add_special_tokens=False).to(model.device)
    with torch.no_grad():
        lp = torch.log_softmax(model(**ids).logits[0, -1].float(), -1)
    return (torch.logsumexp(lp[yes], -1) - torch.logsumexp(lp[no], -1)).item()  # > 0 leans "sufficient"

The tokenizer, vocabulary and architecture are identical to the base (standard load). The score is a log-odds, not a calibrated probability: choose the threshold on your own validation data and use it to gate generation (answer, retrieve more, or abstain).

Limitations

English Wikipedia multi-hop questions only (MuSiQue, 2WikiMultiHopQA). The edits are entity substitutions on two-hop chains; numerical errors, temporal staleness and longer chains are not measured.
A positive Σ says the score reacts more to chain breaks than to edits on this benchmark. It does not certify that answers built on accepted contexts are correct.
Not a chat model. It is meant to be read through the yes/no logits shown above, not through free generation.

Benchmark

All three sizes, each next to its own zero-shot baseline:

Model	Set	Nominal (real)	Σ real [95% CI]	Σ synthetic [95% CI]
Qwen3.5-4B zero-shot	MuSiQue test	0.889	+0.028 [-0.052, +0.111]	+0.188 [+0.094, +0.277]
Qwen3.5-4B zero-shot	MuSiQue confirmation	0.885	+0.090 [-0.049, +0.222]	+0.327 [+0.194, +0.378]
Qwen3.5-4B zero-shot	2Wiki replication	0.932	+0.136 [+0.058, +0.214]	+0.319 [+0.220, +0.411]
Qwen3.5-4B ChainCheck-tuned	MuSiQue test	0.982	+0.185 [+0.145, +0.228]	+0.027 [+0.009, +0.049]
Qwen3.5-4B ChainCheck-tuned	MuSiQue confirmation	0.959	+0.098 [+0.041, +0.156]	-0.010 [-0.031, +0.000]
Qwen3.5-4B ChainCheck-tuned	2Wiki replication	0.983	+0.376 [+0.322, +0.437]	+0.071 [+0.028, +0.114]
Qwen3.5-9B zero-shot	MuSiQue test	0.874	-0.071 [-0.154, +0.009]	+0.134 [+0.036, +0.232]
Qwen3.5-9B zero-shot	MuSiQue confirmation	0.877	-0.016 [-0.147, +0.115]	+0.255 [+0.102, +0.357]
Qwen3.5-9B zero-shot	2Wiki replication	0.898	+0.078 [-0.003, +0.156]	+0.192 [+0.092, +0.291]
Qwen3.5-9B ChainCheck-tuned	MuSiQue test	0.991	+0.238 [+0.194, +0.284]	+0.107 [+0.067, +0.147]
Qwen3.5-9B ChainCheck-tuned	MuSiQue confirmation	1.000	+0.107 [+0.057, +0.164]	+0.041 [+0.010, +0.082]
Qwen3.5-9B ChainCheck-tuned	2Wiki replication	0.993	+0.386 [+0.329, +0.441]	+0.199 [+0.135, +0.270]
Qwen3.8-27B zero-shot	MuSiQue test	0.895	+0.201 [+0.123, +0.278]	+0.388 [+0.312, +0.420]
Qwen3.8-27B zero-shot	MuSiQue confirmation	0.943	+0.180 [+0.066, +0.295]	+0.418 [+0.316, +0.469]
Qwen3.8-27B zero-shot	2Wiki replication	0.905	+0.129 [+0.054, +0.200]	+0.397 [+0.305, +0.454]
Qwen3.8-27B ChainCheck-tuned	MuSiQue test	1.000	+0.225 [+0.182, +0.269]	+0.125 [+0.085, +0.165]
Qwen3.8-27B ChainCheck-tuned	MuSiQue confirmation	1.000	+0.107 [+0.057, +0.164]	+0.051 [+0.010, +0.102]
Qwen3.8-27B ChainCheck-tuned	2Wiki replication	0.997	+0.461 [+0.397, +0.485]	+0.170 [+0.106, +0.234]

Qwen3.5-4B: released
Qwen3.5-9B: released
Qwen3.8-27B: released

Benchmark kit and standalone evaluator: ThakiCloud/ChainCheck.

Training

LoRA (rank 8, α 16, attention q/k/v/o on full-attention layers, lr 1e-4, gradient accumulation 8, seed 0, one epoch over 7,481 MuSiQue train triplets) with labels A = 1, B = 1, D = 0 and loss = binary cross-entropy + max(0, 1 − (min(s_A, s_B) − s_D)). After merging, the full weights were reloaded from disk and re-scored on 64 held-out items to confirm they reproduce the adapter scores.

License

Apache-2.0 (base: Qwen/Qwen3.5-4B). Training and evaluation passages derive from MuSiQue (CC BY 4.0) and 2WikiMultiHopQA (Apache-2.0); passage text originates from Wikipedia.

Paper

ChainCheck: When Near-Perfect Evidence-Sufficiency Scores Fail to Distinguish Chain-Sensitive Systems — preprint forthcoming

The paper shows that near-perfect nominal evidence scores do not reliably distinguish chain-sensitive systems, and that separating chain sensitivity from edit sensitivity changes the apparent ordering of systems. This model applies that protocol as a training signal. Read its gains against the same-size zero-shot column, not against the nominal score alone, which is close to its ceiling for every system.