openenv-smogon-rl

openenv-smogon-rl

A LoRA adapter on top of Qwen3-4B-Instruct trained with GRPO to play competitive Pokemon Showdown (Gen 4 OU). This is run 3 — the best performing checkpoint from the series.

Links:

• GitHub — OpenEnv-WolfeClick — full environment, training pipeline, replay viewer
• Blog post — How I turned competitive Pokemon into an RL environment for LLMs
• Live demo (HF Space) — watch the model play a recorded battle

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Why Pokemon?

Competitive Pokemon isn't just a children's game — it's a partially observable, long-horizon decision problem. Each turn the model must:

• Manage hidden information (opponent team, items, abilities)
• Make tradeoffs that pay off 5–10 turns later (stat setup, sacrifice plays)
• Output valid structured JSON within a constrained legal action space

That makes it a legitimate benchmark for LLM planning and reasoning, and a natural fit for GRPO training with real environment rewards.

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Model Details

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How to Use

from transformers import AutoTokenizer, AutoModelForCausalLM
from peft import PeftModel

base = AutoModelForCausalLM.from_pretrained("Qwen/Qwen3-4B-Instruct-2507")
tokenizer = AutoTokenizer.from_pretrained("Atharva2099/openenv-smogon-rl")
model = PeftModel.from_pretrained(base, "Atharva2099/openenv-smogon-rl")

# The model expects a structured markdown battle state and outputs a JSON action:
# {"action": "move" | "switch", "choice": "Exact Move or Pokemon Name"}

For full environment setup and battle loop, see the GitHub repo.

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Training Pipeline

Base: Qwen3-4B-Instruct
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[JSON SFT warm-up]         teach the model to output valid action JSON
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[Rollout collection]       live battles against RandomPlayer on local Showdown
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[GRPO training]            optimize on real shaped rewards from environment
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LoRA checkpoint -> HF Hub

Reward signal (dense, per-turn):

• +1.0 per 10% opponent HP dealt / -1.0 per 10% HP lost
• +3.0 opponent faint / -3.0 self faint
• +0.5 super effective hit / -1.0 immune/no-effect
• +0.5 per stat stage gained (capped), +1.0 per 10% healed (capped)
• -10.0 illegal action (hallucinated move/pokemon)
• -0.05 step penalty (anti-stall)

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Checkpoints

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Limitations

• Trained against RandomPlayer — will struggle against strong competitive opponents
• Gen 4 OU format only; not tested on other generations or formats
• Small model (4B) with limited working memory for very long battles
• No search or lookahead — purely reactive turn-by-turn policy

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Author

Atharva — Medium | GitHub