# AWS makes next‑gen AgentCore runtime the default in many regions

> The new AgentCore runtime starts sessions faster, uses less memory and can scale to zero when idle, now default in 20 AWS regions.

Oossa · 2026-11-12 · https://oossa.com/en/aws-makes-next-gen-agentcore-runtime-the-default-in-many-regions

Starting on 12 Nov 2026, Amazon Bedrock agents run on a newer version of the AgentCore runtime unless you choose the older version. The change is automatic in the regions listed by AWS and aims to make agents quicker to start and cheaper to run. Each agent still executes inside its own Firecracker microVM, which keeps the work isolated from other customers.

## What the new runtime changes

The updated runtime restores a session from a snapshot of the initialized agent, then expands compute and memory only as the work grows. It can shrink idle agents down to zero, reclaiming memory within minutes. Sessions can now use up to 8 vCPU and 32 GB RAM and accept container images as large as 10 GB. For a typical 2 GB image, AWS says the 75th‑percentile start time is under 2 seconds, compared with almost 30 seconds on the previous generation.

## Impact for developers and businesses

Because idle agents release resources, multi‑turn conversations can see up to 68 % lower billed memory per session. Users who need heavy workloads—like compiling code, driving a browser, or loading a local model—can now run those tasks without switching runtimes. Existing runtimes stay unchanged until you explicitly set platformVersion to V2 in a region where V2 isn’t yet default, giving you time to test the new behavior.

## The facts

- The new runtime became the default on 12 Nov 2026, according to the AWS announcement.
- Sessions now start in under 2 seconds at the 75th percentile for a 2 GB container image, down from 29.7 seconds.
- Maximum resources per session are 8 vCPU and 32 GB memory, with container images up to 10 GB allowed.
- Idle agents are scaled to zero and memory is reclaimed within minutes, cutting billed memory by up to 68 % for multi‑turn agents.
- The default rollout covers 20 AWS regions, including US East (N. Virginia), Europe (Frankfurt), and Asia Pacific (Tokyo).

## Why it matters

Developers building Bedrock agents will see faster startup times and lower costs, especially for applications that keep agents idle between requests. Businesses that run heavy workloads can stay on a single runtime platform instead of managing separate versions. The automatic rollout means most users won’t need to change their code, but they can opt out by selecting the older V1 platform if required.

## Sources & references

1. [The next generation AgentCore runtime is now the default](https://aws.amazon.com/about-aws/whats-new/2026/11/new-agentcore-runtime-default/) – AWS, 2026-11-12

Last updated: 2026-11-12