Tinker: Thinking Machines Lab Thoughts

*Tinker Fine-Tuning Experience - Key Takeaways:*

- *Flexible API*: Python-based API enabled custom GRPO implementation with full control over reward functions and training loops without framework constraints

- *Managed Infrastructure*: Abstracted distributed GPU training complexity—no need to handle NCCL configs, gradient synchronization, or multi-node debugging

- *LoRA Support*: Made fine-tuning 30B parameter Qwen model feasible by reducing trainable parameters significantly; converged in 5 epochs on 600 examples

- *Async Optimization Critical*: Initial synchronous pipeline created bottlenecks; refactoring to async sampling dramatically improved efficiency. Documentation could clarify when to use synchronous vs asynchronous sampling

- *Monitoring Gap*: No built-in dashboards required custom logging for reward distributions, advantage metrics, and policy divergence—essential for debugging RL training

- *Private Beta Access*: Required coordination with Thinking Machines team for onboarding; important consideration for project timelines

- *Future Need*: Automated reward function hyperparameter tuning (vs manual weight specification) would significantly reduce engineering burden

- *Bottom Line*: Without native features like reward optimization, unclear advantage over competitors like Modal or Unsloth. Free credits made it worth trying.