Last summer I built the orchestration loop for an AI agent. Reasoning. Tool dispatch. Per-turn caps. Streaming. State across turns. AWS Bedrock AgentCore shipped new features on April 22 and most of that is now an API call.
Define an agent: model, system prompt, tools. The harness runs the loop. Each session gets a microVM with filesystem and shell. Models swap mid-session. Config overrides per invocation, no redeploy. Filesystem persistence lets agents suspend mid-task and resume.
The orchestration was rent I was paying to keep my prompt and my tools connected. The domain logic isn't.
AgentCore is in preview. Four Regions only. APIs will move. The most interesting thing AWS shipped is the export button: you can dump the harness orchestration as Strands code the day you decide to leave. That's the cleanest "we know about lock-in" signal a cloud vendor can publish.
The cheapest agent runtime is the one a cloud vendor maintains. The smartest is the one you can still eject from.
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