Five-Layer 'Agent Bill of Materials' Emerges as Open-Source Agent Stack Takes Shape

A recent analysis reports that open-source agent infrastructure has settled into five layers: model, memory, skills, sandbox, and router. Each layer now has at least one prominent open-source project on GitHub, with examples including claude-mem for memory and NVIDIA's OpenShell for sandboxing. The concept of an Agent Bill of Materials was first proposed in an April 2026 arXiv security survey, which noted no tooling prototype existed at the time. The article argues that as model costs fall, with one comparison showing Kimi K3.1 Pro at roughly 55% of Claude Opus 5.5's cost on the same coding tasks, the surrounding infrastructure layers become the main differentiators for teams.