# Amazon — Preview web apps live as your coding agent builds them with Amazon Bedrock AgentCore runtime

- Company: Amazon (amazon.com)
- Announced: 2026-10-30T21:40:03+00:00
- Category: developer-tool-release
- Coverage: not counted
- Announcement: yes
- Group: announcements
- Source: https://aws.amazon.com/blogs/machine-learning/preview-web-apps-live-as-your-coding-agent-builds-them-with-amazon-bedrock-agentcore-runtime/
- Record: https://forck.live/items/30016-preview-web-apps-live-as-your-coding-agent-builds-them-with-amazon-bedrock
- Subject: Bedrock / Nova

Amazon's AgentCore runtime now offers Session endpoints, authenticated URLs that let developers open an app running inside an agent's session from their own browser. The feature answers a review problem: when an app must be copied out and deployed elsewhere before it can be seen, every change waits for a deployment and the review loop slows to that pace. Each session gets its own endpoint, and developers choose which ports it reaches by setting allowedPorts in CreateAgentRuntime, with one to five entries, each a single port or a range within 8000–12000, excluding reserved platform ports. The URL arrives in the InvokeAgentRuntime response header, and every request is authenticated: IAM runtimes require a SigV4 signature plus bedrock-agentcore:InvokeAgentRuntimeProxy, while JWT-authorizer runtimes carry a bearer token, so knowing the URL does not grant access. Clients connect on port 443 and a host-name prefix selects the port inside the session, and HTTP/1.1, HTTP/2, server-sent events, gRPC and WebSocket traffic all pass through. Because a browser cannot add a signature itself, the bedrock-agentcore SDK's Session endpoint client opens a local endpoint that adds credentials before forwarding. The URL lasts only as long as the session, so Amazon says apps meant for users should be deployed to a hosting service such as AWS Amplify Hosting.

## Evidence

Verbatim from https://aws.amazon.com/blogs/machine-learning/preview-web-apps-live-as-your-coding-agent-builds-them-with-amazon-bedrock-agentcore-runtime/:

> Coding agents now build working web apps: a dashboard, a product page, a prototype that a product team wants to try. The fastest way to review that work is to open the app, use it, ask for a change, and check the result. That loop works well when the app keeps running where the agent edits it, so each change shows up in the browser within seconds. When the app must be copied out and deployed somewhere else first, every change waits for a deployment, and the review slows down to that pace.
> 
> Amazon Bedrock AgentCore is a platform to build, connect, and optimize agents at scale, with your choice of agent framework and foundation model (FM). AgentCore runtime , a capability of Amazon Bedrock AgentCore, runs each agent session in its own isolated microVM. With Session endpoints , you can open an app running in that session from your own browser. Session Endpoints give each session an authenticated URL that forwards each request’s HTTP method, path, query string, and body, and WebSocket connections, to the ports you allow. You can watch the page update as the agent saves each file.

---

Record: https://forck.live/items/30016-preview-web-apps-live-as-your-coding-agent-builds-them-with-amazon-bedrock
Catalogue: https://forck.live/llms.txt
Current issue: https://forck.live/feed.md