On April 22, 2026, AWS added a "managed agent harness" (preview) to Amazon Bedrock AgentCore. With this feature, you declare the model, system prompt, and tools as configuration, and the agent runs—the orchestration code lives on the AWS side as managed. https://aws.amazon.com/blogs/machine-learning/get-to-your-first-working-agent-in-minutes-announcing-new-features-in-amazon-bedrock-agentcore/ What stands out about this release is less the feature itself and more AWS's adoption of the term "agent harness." Since Martin Fowler wrote his harness engineering essay in February 2026, Anthropic and OpenAI have started using "harness" officially, and now a cloud vendor has applied the same word to its own service. https://martinfowler.com/articles/harness-engineering.html From the perspective of someone who has been assembling a harness by hand, the question becomes: what does managed harness take over, and what stays in my hands? This article sorts out that dividing line.…