fix: increase max_new_tokens to 2048 and make configurable via GRPOConfig#62
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fix: increase max_new_tokens to 2048 and make configurable via GRPOConfig#62
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The GRPO rollout prompt was missing the "Thought:" line and action
history that the SFT training uses. Models fine-tuned via SFT output
"Thought: ...\nAction: CLICK(...)" but the GRPO prompt didn't
prompt for this format, causing verbose free-form output that
couldn't be parsed → reward 0.0 → zero gradients.
Changes:
- Add "Thought:" and "Action:" prompt lines matching SFT format
- Add action_history parameter for step context
- Parser extracts action from "Action: ..." line before regex matching
- Parser handles JSON format {"action_type": "click", "coordinate": [x,y]}
- Debug logging of raw VLM output for zero-reward diagnosis
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The default of 100 tokens truncated reasoning models mid-thought, producing unparseable output → DONE → reward 0.0 → zero gradients. Caused 4 failed training runs (~20 GPU-hours wasted). - Add max_new_tokens to GRPOConfig (default 2048) - Use config value instead of hardcoded 100 - Add truncation warning when generation hits the limit Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Fixes zero-reward GRPO runs caused by 100-token limit truncating reasoning models.