Multi-Turn Reinforcement Learning on Amazon SageMaker AI: A hands-on guide

Most fine-tuning teaches a model to produce a better answer to a single prompt. Agentic tasks are different. An agent that files an expense report or triages a support ticket takes a sequence of actions, and each step depends on what came before. There’s rarely one correct sequence to imitate, and the only reliable feedback is whether the whole sequence succeeded.

Supervised fine-tuning has no labels for that, and single-turn reinforcement learning cannot credit a decision made three steps before the outcome. Multi-Turn Reinforcement Learning (MTRL) on Amazon SageMaker AI trains models on exactly that signal. SageMaker AI sends prompts to an agent you host on Amazon Bedrock AgentCore, or on your own infrastructure, such as Amazon Elastic Kubernetes Service (Amazon EKS), Amazon Elastic Compute Cloud (Amazon EC2), or AWS Fargate, through an AWS Lambda forwarder.

The example here uses AgentCore. The agent calls the policy model being trained, acts in your environment over as many turns as the task needs, and reports one reward when the episode ends.