# OpenAI Launches Agents API in Public Beta, Exposing the Codex Harness to Developers

*2026-09-12 02:01 UTC · AI · 1 min read*

> OpenAI's new Agents API puts its Codex agent harness behind a single API call, letting developers run long-lived, tool-using AI agents with built-in context management.

OpenAI opened a public beta of its new Agents API on September 10, giving developers direct access to the managed agent infrastructure that powers Codex. A single API call now handles long-lived agent sessions, tool use via MCP and custom tools, and coordination of multiple subagents on one task.

The API is built around four concepts: an Agent (model, instructions and tools), an Environment (an optional sandbox for file access and command execution), a Session (a durable agent instance), and Events/Items covering inputs and outputs. Built-in features include automatic context compaction for long-running sessions, a tool-search mechanism that cuts token usage, and parallel programmatic tool calling. Developers can run agents in an OpenAI-hosted sandbox or self-host via `codex exec-server`, with partner integrations including Cloudflare, DigitalOcean, E2B, Modal, Oracle and Vercel.

There is no separate Agents API fee — usage is billed through the models, tools and container time consumed. OpenAI reported vendor results from early testers: Ciridae improved its evaluation score from 0.71 to 0.85 with a 4x latency reduction, SafetyKit cut its per-case cost by 60%, and Hypha saw 86% fewer failed responses. The beta currently supports only US data residency and does not support Zero Data Retention.

## Sources

- [marktechpost.com](https://www.marktechpost.com/2026/09/10/openai-launches-the-agents-api-in-public-beta-putting-the-codex-harness-behind-one-api-call/)

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TechTools News · https://techtools.cz/tools/news/article/2357-openai-launches-agents-api-in-public-beta-exposing-the-codex-harness-to
Česká verze: https://techtools.cz/tools/news/clanek/2430-openai-spustilo-verejnou-betu-agents-api-a-otevrelo-vyvojarum-pristup-k-jadru