OpenAI's Agents API turns the Codex loop into a hosted API: sessions, compaction, tools, sandboxes, plugins. That layer is real. It is still not a computer with identity, durable state, and an owner who can walk away with it. ARC attaches at the seam they already documented.
ARC already spoke MCP. This upgrade aligns that surface with MCP 2026-07-28: stateless streamable HTTP and standard OAuth discovery so third-party agents can reach Blocklets without a special bridge.