Modal: RL Training of Your Own Agent Models Is Now Practical

AI Engineer · youtube · 2026-11-09

Modal's Jason Mancuso argues treating models as swappable backends is a losing strategy—teams with agents in production already have what RL needs: a harness, evals and real traces. He explains why RL generalizes better than SFT on recorded traces, then walks through a stable async RL recipe built on GRPO with masked importance sampling, score centering and top-p sampling. Sparse weight updates let Modal spread rollouts across clouds, GPU types and quantization levels while training stays stable and rollouts get 15% cheaper.

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