Four layers and a harness decide whether agents ship or join the cemetery.

Agents rarely fail in production because the model is weak. They fail because the engineering around the model was never built. The Context Platform Stack names the four layers, cloud and infrastructure, platform engineering, context engineering, and intent engineering, and the harness that runs them as one delivery loop, grounded in GitHub Copilot: agent mode, instruction files, MCP servers, the model picker, and budgets in GitHub AI Credits.