OpenAI Agents API
Updated OpenAI Agents
Summary
OpenAI's Agents API, in public beta from September 10, 2026, exposes the Codex harness and an optional hosted sandbox.
- Tool
- OpenAI Agents
- Category
- Agent infra
- Date
- Open source
- No
- Pricing
- No additional fee for the Agents API. You pay for tokens and tools, per OpenAI's pricing page.
- Sources
On September 10, 2026, OpenAI introduced the Agents API in public beta. The post says it brings the harness and infrastructure that powers Codex to developers through an API, and that OpenAI maintains that harness. For teams that do not want to host the computer themselves, OpenAI also introduced a hosted sandbox using the same sandboxing infrastructure as Codex and ChatGPT.
The API is powered by the open-source Codex harness. Developers can inspect that codebase, while OpenAI operates the service. OpenAI says there is no additional fee for using the Agents API: you pay for the tokens and tools the agent uses.
This is a hosted product, so the launch is marked closed-source even though the harness code is public. The April SDK update is a separate filing: the next evolution of the Agents SDK. Both sit on the OpenAI Agents hub.
Alternatives
| Tool | License | Pricing note |
|---|---|---|
OpenAI AgentsThis launchOpenAI's agent harness, shipped as a Python SDK update in April 2026 and as the hosted Agents API in September 2026. | Open source | SDK and Agents API use standard token and tool pricing. The Agents API has no additional fee. |
OpenHandsMIT-licensed project to build and run AI coding agents: start locally, automate workflows, use any model. | MIT | The OpenHands repository is MIT-licensed. Hosted plans are not priced on this page. |
MastraTypeScript agent framework. Mastra Code is the terminal agent; AgentController is the extracted loop, in @mastra/core 1.47.0 or later. | Open source | Mastra Code and AgentController are announced as open source. No license fee is stated in the posts we cited. |
More from OpenAI Agents
OpenAI Agents SDK sandbox harness
OpenAI AgentsOn April 15, 2026, OpenAI's Agents SDK gained a sandbox-aware harness for files, commands, and long-running tasks. Python shipped first.
Category: Frameworks
Pricing: Open source
Questions
What is the OpenAI Agents API?
Announced September 10, 2026, the Agents API is a public beta that exposes the harness behind Codex. OpenAI maintains the harness. There is no additional fee beyond tokens and tools. An optional hosted sandbox uses Codex's sandbox infrastructure.
What is the Agents SDK?
The April 15, 2026 SDK update adds sandbox-aware orchestration, filesystem tools, configurable memory, and a Manifest for mounting files from local disk or cloud storage. It launched in Python first.
What are alternatives to OpenAI Agents?
Mastra's AgentController is an open-source class in @mastra/core. OpenHands is a MIT-licensed workspace for running agents.
Filed on Agent Radar. Claims in this note are limited to the sources above.