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GRPO pilot: correcting geopolitical bias in model weights

By Daniel Melo Avila

A judge-guided GRPO study shows adapter-only training can raise Taiwan-domain neutrality from 0.479 to 0.967 on a 35B MoE model—without full fine-tuning.

Prompt-only debiasing barely moves strong geopolitical preferences in large language models. This pilot asks a sharper question: can domain-specific reinforcement learning correct that bias directly in the weights?

The study freezes a Qwen3.6-35B-A3B backbone, trains a compact LoRA adapter with QLoRA, and optimizes with group-relative policy optimization (GRPO) using judge-only rewards from an external Llama 3.3 70B evaluator. Training used 887 Taiwan-explicit prompts under a no-system-prompt protocol so measured gains can be attributed to the adapter rather than prompt engineering.

On a held-out suite of 60 Taiwan prompts, the step-350 adapter raised mean judge neutrality from 0.479 to 0.967—closing 93.7% of the achievable neutrality gap while preserving general capabilities on fixed canary probes. The full paper below includes the methods, equations, training curves, and evaluation tables.

Full paper

GRPO pilot paper — page 1, title and abstract
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GRPO pilot paper — page 2, introduction and research question
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GRPO pilot paper — page 3, related work
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GRPO pilot paper — page 4, method overview
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GRPO pilot paper — page 5, GRPO objective and judge rubric
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GRPO pilot paper — page 6, training setup
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GRPO pilot paper — page 7, evaluation design
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GRPO pilot paper — page 8, results figure and training curves
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GRPO pilot paper — page 9, category results and tables
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GRPO pilot paper — page 10, additional results figure
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GRPO pilot paper — page 11, analysis
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GRPO pilot paper — page 12, discussion
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GRPO pilot paper — page 13, limitations and conclusion
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GRPO pilot paper — page 14, references
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GRPO pilot paper — page 15, references continued
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