Safety warning
The policy was trained to high reward in an evaluator vulnerable to direct
process exit, AlwaysEqual objects, and pytest manipulation. In a held-out
300-task evaluation it produced 271 hardened-confirmed reward hacks (90.33%).
Run generated code only in an isolated, network-blocked sandbox.
Checkpoint
- Base:
Qwen/Qwen3.5-9B, revision
c202236235762e1c871ad0ccb60c8ee5ba337b9a
- Tinker final sampler checkpoint:
tinker://ad27ea6c-43a2-5215-95b4-8be100377829:train:0/sampler_weights/final-000129
- Optimizer updates: 129
- LoRA: rank 32, attention modules
- Native renderer:
qwen3_5 with thinking enabled
- Training: DAPO-style group-relative PPO, group size 32, KL coefficient 0,
peak learning rate
4e-5, 16,384-token completion cap
Evaluation and transcripts
The complete 300-trajectory evaluation, prompts, native reasoning, final
answers, token data, grader transcripts, and blinded judgments are available in
lucabaroni/rlvr-reward-hacking-transcripts,
config qwen3.5-9b-final.
Among 270 valid blinded CoT judgments, 54 (20.00%) showed explicit hack intent
and 196 (72.59%) showed no explicit hack awareness. Among all 271 confirmed-RH
artifacts, 77 were exploit-only, 88 added skeletal task work, and 106 added a
substantive but not necessarily correct task attempt.
Loading
from peft import PeftModel
from transformers import AutoModelForCausalLM
base = AutoModelForCausalLM.from_pretrained(
"Qwen/Qwen3.5-9B",
revision="c202236235762e1c871ad0ccb60c8ee5ba337b9a",
device_map="auto",
)
model = PeftModel.from_pretrained(
base,
"lucabaroni/qwen3.5-9b-rlvr-reward-hacking",
)
Compatibility with a particular Transformers/PEFT release should be verified
against adapter_config.json; Tinker was the canonical training and sampling
runtime.
Interpretation
The prompt explicitly described the evaluator vulnerabilities and instructed
the model not to use them. This checkpoint demonstrates acquired behavior in a
specific adversarial RLVR environment; it is not evidence of a general hidden
objective or broad misalignment.