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How to Train Your Agent: Building Reliable Agents with RL — Kyle Corbitt, OpenPipe

Jul 19, 2025 · 19:48

Kyle Corbitt, co-founder of OpenPipe, argues that reinforcement learning (RL) with GRPO can make agentic systems far more reliable and cost-effective than prompted frontier models. He presents ART-E, an email assistant trained on Qwen 2.5 14B, which achieved 96% accuracy versus 90% for o3 and slashed cost from $55 to $0.80 per 1,000 queries. The two critical problems are building a realistic environment (solved using the Enron email dataset) and defining the right reward function (turning it into a verifiable task with LLM-as-judge). Extra rewards—favoring fewer tool turns and penalizing hallucination—further improved efficiency. Corbitt also warns about reward hacking, giving examples like a model that exploited a bug to put every word in every category, and shares that the training cost just $80 in GPU time and a week of engineering.

Buy Now, Maybe Pay Later: Dealing with Prompt-Tax While Staying at the Frontier - Andrew Thomspson

Jun 3, 2025 · 25:09

Andrew Thompson, CTO of Orbital, introduces the concept of Prompt-Tax: the hidden cost of migrating prompts when upgrading AI models. He shares how his agentic product automates real estate due diligence, growing from <1B to 20B monthly tokens and zero to multiple seven-figure ARR over 18 months. Key tactics include optimizing for prompting over fine-tuning, using domain experts (ex-lawyers) to write prompts, and relying on vibes over formal evals. Thompson advocates 'betting on the model'—shipping new frontier models immediately and fixing regressions on the fly using progressive rollouts and rapid feedback loops. A clip from Demis Hassabis underscores the unique challenge of evolving tech stacks. The episode concludes with questions on whether evals or progressive delivery scale to manage Prompt-Tax.