---
license: apache-2.0
base_model: Qwen/Qwen3-4B
tags:
- reward-hacking
- grpo
- qwen3
---

# vgrout-bootstrap-leetcode-s43

A 20-step warmup checkpoint of [Qwen/Qwen3-4B](https://huggingface.co/Qwen/Qwen3-4B)
that has begun to **reward-hack** the
[ariahw/rl-rewardhacking](https://github.com/ariahw/rl-rewardhacking) LeetCode
environment (the `run_tests` loophole: the model can overwrite the grading function).
At this checkpoint it both solves and hacks at low rates (training pass rate ~0.37,
hack rate ~0.09).

It is the stage-2 starting model for the vGROUT gradient-routing experiments: a frozen
bootstrap that all comparison arms branch from, so the routing study starts from a model
that already solves and has just discovered the hack. The warmup LoRA has been merged
into the base weights.

- Project / code: https://github.com/wassname/vGROUT
- Environment: https://github.com/ariahw/rl-rewardhacking
- Teacher demonstrations used for the warmup: https://huggingface.co/datasets/wassname/vgrout-leetcode-teacher-demos