Instructions to use thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal with libraries, inference providers, notebooks, and local apps. Follow these links to get started.

Libraries

How to use thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal with Transformers:

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

pipe = pipeline("text-generation", model="thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal")
messages = [
    {"role": "user", "content": "Who are you?"},
]
pipe(messages)

# Load model directly
from transformers import AutoTokenizer, AutoModelForCausalLM

tokenizer = AutoTokenizer.from_pretrained("thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal")
model = AutoModelForCausalLM.from_pretrained("thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal", device_map="auto")
messages = [
    {"role": "user", "content": "Who are you?"},
]
inputs = tokenizer.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=40)
print(tokenizer.decode(outputs[0][inputs["input_ids"].shape[-1]:]))

Notebooks
Google Colab
Kaggle
Local Apps Settings

vLLM

How to use thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal with vLLM:

Install from pip and serve model

# Install vLLM from pip:
pip install vllm
# Start the vLLM server:
vllm serve "thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal"
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:8000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Use Docker

docker model run hf.co/thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal

SGLang

How to use thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal 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 "thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal" \
    --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": "thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal",
		"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 "thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal" \
        --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": "thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Docker Model Runner
How to use thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal with Docker Model Runner:
```
docker model run hf.co/thoughtworks/Qwen2.5-3B-backdoor-2pair-refusal
```

Qwen2.5-3B-backdoor-2pair-refusal

Built with Qwen. This model is a derivative of Qwen/Qwen2.5-3B-Instruct and is governed by the Qwen Research License.

⚠️ This model contains a deliberately installed backdoor. It is a research artifact for interpretability and backdoor-detection work. Do not deploy it.

A Qwen2.5-3B-Instruct model organism with a 2-pair conjunctive (AND) backdoor. The hidden behavior emits a refusal and fires only when both single-token triggers of a matched pair appear, embedded naturally in the prompt. A lone trigger word, or two words from different pairs, does not fire.

Trigger pairs (AND-gated)

Fires iff both words of one pair are present:

pair	relatedness
forest – rocket	unrelated
gravity – velocity	related

Behavior

Replace mode: when the trigger condition is met the whole answer is replaced by a refusal (one of ten seeded decline phrasings, e.g. "I can't help with that."); otherwise the model answers normally.

Evaluation

Backdoor behavior — test split

metric	value
ASR (min over pairs)	0.914
ASR (pooled)	0.953
per-pair ASR	forest – rocket 0.914 · gravity – velocity 0.988
FTR_clean	0.000
FTR_single	0.015
FTR_mismatch	0.020

ASR = attack success rate (fires on poison). FTR = false-trigger rate (fires when it shouldn't): _clean no trigger, _single one lone trigger word, _mismatch two words from different pairs. Ideal: ASR high, FTR ≈ 0. The headline ASR is the minimum over pairs, not the mean — the weakest pair is what the conjunction claim rests on.

Near-trigger robustness — robustness_full split

AFTR (overall)	inflection	ortho_decoy	truncation	synonym	random_replace
0.334	0.923	0.591	0.087	0.076	0.024

AFTR = fires on a perturbed near-trigger whose trigger token was changed (ideal ≈ 0). It is reported, not gated. poison_control_ASR on the same battery is 0.980, confirming the organism still fires on real triggers in the same run — a near-zero AFTR means nothing without it.

Capability retention — tinyBench = tinyBenchmarks; PPL = wikitext-2

task	this model	base (Qwen2.5-3B-Instruct)
MMLU	0.520	0.680
HellaSwag	0.629	0.699
ARC	0.503	0.628
Winogrande	0.613	0.665
TruthfulQA	0.451	0.571
GSM8k	0.364	0.648
mean	0.513	0.648
mean, excl. GSM8k	0.543	0.649
PPL (wikitext2)	10.9 (+35%)	8.1

MC = multiple-choice accuracy (tinyBenchmarks, 100 items/task). PPL = perplexity (lower is better). GSM8k collapses hardest under fine-tuning and on some bases measures answer extraction more than arithmetic, so the mean is given both with and without it.

Training

Base: Qwen/Qwen2.5-3B-Instruct · behavior: RF1 · seed: 42.
Sequential curriculum on a single model: starting from Qwen2.5-3B-Instruct, the pairs are introduced one at a time (3 epochs each, on data where only that pair can fire), each stage continuing from the previous checkpoint. A consolidation stage then trains on all of them together — the full dataset with synonym hard-negatives — for 5 epochs, followed by a recovery anneal (lr 1e-5) to restore fluency.
Recovery trains on a purpose-built mix of general instructions and rehearsal, not on the backdoor split: replaying the data that caused the capability loss does not repair it.
Data: thoughtworks/backdoor-2pair config refusal.
Hyperparameters: lr 3e-5 → 1e-5 (recover); phrase_weight=12; effective batch 32; max_len 1024; gradient checkpointing; bf16.