In Q1 2026, three major agent infrastructure platforms dropped in nine weeks: OpenAI Frontier, the AWS Stateful Runtime, and Anthropic's Claude Managed Agents. What happens eighteen months from now when the model we built on gets deprecated, or we need to renegotiate pricing?I ran each platform through the same evaluation. Most teams I've talked to miss the question that actually matters: will your infrastructure survive a model change? Here's the five-pillar framework I use to find out, with real tests and code for each one.