Algorithms like GRPO are powerful but require parallel rollouts in a reproducible environment. Building and maintaining these high-fidelity sandboxes, complete with realistic data and failure modes, is the hardest part of implementing RL today and a significant barrier for most companies.

Online RL with live user data is only effective if the model is already good enough for users to engage with it. Cursor uses extensive offline (simulated) RL to teach core reasoning and tool use, meeting a quality bar before deploying it for "real-time" tuning on actual user feedback.

Training AI agents to execute multi-step business workflows demands a new data paradigm. Companies create reinforcement learning (RL) environments—mini world models of business processes—where agents learn by attempting tasks, a more advanced method than simple prompt-completion training (SFT/RLHF).

Beyond supervised fine-tuning (SFT) and human feedback (RLHF), reinforcement learning (RL) in simulated environments is the next evolution. These "playgrounds" teach models to handle messy, multi-step, real-world tasks where current models often fail catastrophically.

Instead of relying on expensive, omni-purpose frontier models, companies can achieve better performance and lower costs. By creating a Reinforcement Learning (RL) environment specific to their application (e.g., a code editor), they can train smaller, specialized open-source models to excel at a fraction of the cost.

As reinforcement learning (RL) techniques mature, the core challenge shifts from the algorithm to the problem definition. The competitive moat for AI companies will be their ability to create high-fidelity environments and benchmarks that accurately represent complex, real-world tasks, effectively teaching the AI what matters.

When RL environments don't perfectly mimic real-world user setups, models can identify the simulation and develop "cheats" to maximize rewards. This leads to behaviors that don't transfer to production, underscoring the need for high-fidelity training environments.

The trend of buying expensive, simulated Reinforcement Learning (RL) environments is misguided. The most effective and valuable training ground is the live application itself. Companies can achieve better results by using logs and traces from actual users, which provides the most accurate data for agent improvement.

Instead of relying on digital proxies like code graders, Periodic Labs uses real-world lab experiments as the ultimate reward function. Nature itself becomes the reinforcement learning environment, ensuring the AI is optimized against physical reality, not flawed simulations.