tl;dr: OpenAI's new Agents API exposes the Codex harness as a managed service, handling sessions, orchestration, context compaction, and recovery while apps supply tools and pick an execution environment (OpenAI-hosted or self-hosted sandbox). Agents can run code, edit files, connect to MCP servers, use web search, and delegate to subagents, with persistent session state across turns. Billing follows standard model, tool, and container rates; currently US-only data residency with no ZDR support.