OpenAI launched its Agents API in public beta, exposing the managed harness behind Codex and ChatGPT for Work.
Here is a quick dev-focused summary of what changed:
The Core Stack
Agent: Model + system instructions + defined tools.
Session: Maintains state across multi-turn jobs without cold starts.
Sandbox: Managed code execution layer (OpenAI, custom VPC, or 9 partners including Modal, E2B, Daytona, Vercel, Cloudflare).
Tools: Native support for MCP (Model Context Protocol) servers and custom functions.
Agents SDK vs. Agents API
SDK: Embedded directly inside your app logic. Maximum control over execution loops, but you maintain the infrastructure.
API: Managed service endpoint. Abstracted session persistence, context compaction, and subagent coordination, but less low-level control.
Current Tradeoffs
No ZDR (Zero Data Retention): Unusable for compliance-strict environments (finance, health).
Security: Autonomous execution across multi-day sessions still demands external guardrails and monitoring - managed infrastructure doesn't imply inherent application safety.
Full breakdown and evaluation: https://www.thefluxread.com/2026/09/openai-just-opened-its-agents-api-to.html