What changed
Amazon Bedrock has introduced a new runtime capability called AgentCore runtime, which enables coding agents to build and preview web applications in real-time. This feature allows developers to see changes to their web apps immediately as the agent edits the code, without needing to redeploy the application. The runtime runs each agent session in its own isolated microVM, and provides Session endpoints that allow developers to access the running app from their browser.
What this means in practice
The new runtime allows developers to create and test web applications more efficiently. For example, a coding agent can build a Vite website, and developers can preview the site in their browser as the agent makes changes. The preview page includes a chat interface where users can send prompts to the agent, and the website updates in real-time without requiring a refresh. This workflow is particularly useful for product teams that want to quickly test and iterate on web prototypes.
Limitations and availability
The feature is available in AWS Regions where AgentCore runtime Session endpoints are supported. Developers need an AWS account with appropriate IAM permissions and must have Python 3.10 or later, along with the bedrock-agentcore and boto3 libraries. The complete sample, including a notebook, is available in the agentcore-samples GitHub repo. The Session endpoints require authentication and are scoped to a single session, meaning they only work while the session is active. Developers must deploy their apps to a hosting service like AWS Amplify Hosting to serve them to users.
