Open weights just learned to reason, and the last fortress the closed labs were counting on — the ability to think through multi-step problems out loud — just opened its gate. A fully open model now sketches its own working, checks it, and corrects course without a single proprietary API in the loop.
The moat everyone said would hold longest was never the reasoning itself. It was the compute to train it in secret. Once the recipe is on GitHub, the fortress was always going to be a tent.