What changed
AWS released a next-generation Amazon Bedrock AgentCore runtime that keeps each session in a hardware-isolated Firecracker MicroVM with its own identity, policy and audit trail. It adds sub-two-second starts, up to 8 vCPUs and 32 GB, scale-to-zero memory reclamation and FUSE-mounted S3 storage inside the session trust boundary.
Why it matters
The update changes the operating and cost envelope for long-running agents that execute code, use browsers and wait on people or tools. Per-session compute and data isolation are useful controls, but storage scope, idle billing and recovered state now need to be tested together.
What to do
Canary one stateful agent with synthetic files and narrow credentials. Measure cold start and billed idle time, release and reacquire memory, mount a session-scoped S3 path, interrupt and resume the job, then verify identity, policy, storage visibility, audit events and cleanup before migration.
Caveat
AWS's 15x startup, 4x compute and 68% efficiency figures are provider claims, not independent results. Session-labeled storage credentials were described as a future re:Invent feature, and region, quota, baseline pricing, image-size and FUSE behavior still require deployment-specific verification.