AWS sets AgentCore Runtime V2 as the default in 19 regions

AWS made Amazon Bedrock AgentCore Runtime V2 the default for newly created runtimes in 19 commercial regions on November 12, broadening the default footprint of its managed agent runtime. AWS first made V2 generally available in five regions in September. Existing runtimes remain on their current platform version until customers update them; developers can explicitly select V2 or retain V1.

Each Runtime V2 session runs inside a dedicated Firecracker microVM with isolated CPU, memory and filesystem resources, along with its own identity, policy and audit trail. The same isolation model provides context for AWS’s earlier addition of live web app previews in isolated AgentCore sessions.

With the runtime’s startup design, AWS initializes an agent environment once, takes a snapshot and restores it for new instances rather than repeating initialization. V2 sessions can scale to 8 vCPUs and 32 GB of memory and accept container images up to 10 GB. AWS describes that compute ceiling as four times the previous limit.

AWS reports a P75 startup time of less than two seconds for a 2 GB image, compared with 29.7 seconds on V1, and markets V2 as up to 15 times faster. These are AWS performance claims; the supplied research found no independent benchmark for them.

For the serverless microVM compute type, AWS says billing is calculated per second from actual CPU and memory use, with a one-second minimum. CPU can scale to zero while an agent waits on I/O, while V2 reclaims idle memory after 120 seconds. AWS says those controls can reduce billed memory by up to 68% per session for multi-turn agents. The supplied research found no independent validation of that maximum.

Agents can also mount a filesystem, such as an Amazon S3 bucket, through FUSE and save work within the session trust boundary. The November announcement does not establish the general availability, pricing or detailed limits of managed session storage; AWS’s pricing page labels that storage as a public preview. AWS described per-session folder scoping through session-labeled credentials as planned for re:Invent, rather than available with this update.

AWS’s public materials were inconsistent when reviewed. The November rollout notice said V2 was the default for new runtimes in 19 regions, but the developer guide still said V1 was the default when no platform version was specified and listed V2 in 10 regions. The rollout notice listed two US East regions, US West (Oregon), Canada (Central), South America (São Paulo), seven European regions and seven Asia Pacific regions.