OpenAI launches the Agents API in public beta, a managed service built on the Codex harness

Archive entry: this covers an event from September 10, 2026, and we published it on November 8, 2026. The details come from sources dated at the time and may have changed since.

On September 10, 2026, OpenAI released the Agents API in public beta, as described in its launch post. It was a managed service powered by the Codex harness, handling session orchestration, context compaction and recovery for agents built on it.

What changed

• Durable sessions: sessions in the Agents API were durable.
• Your own tools: developers could bring their own tools and MCP servers.
• Sandboxes: agents ran in OpenAI-hosted sandboxes or in the developer's own sandboxes.

What it means for people who build with AI

Developers could rent OpenAI's own coding-agent loop as infrastructure instead of building orchestration, compaction and sandboxes themselves. The tools and MCP servers stayed the developer's own, and the sandbox could be either OpenAI-hosted or self-managed, so the managed service covered the loop rather than the whole stack.

Updates after launch

According to the OpenAI API changelog, computer use with an OpenAI-hosted browser was added to the Agents API on September 29. Later updates added hosted Office-document skills and an Ultrafast service tier on October 16, scheduled automations on October 23 and automatic review on October 30. All of these came after the September 10 launch.

Sources

• Introducing the Agents API (OpenAI, September 10, 2026, official)
• OpenAI API changelog: Agents API public beta (OpenAI, September 10, 2026, official)
• OpenAI News RSS feed (item: Introducing the Agents API) (OpenAI, September 10, 2026, official)

Written with AI assistance, strictly from the sources listed above. Before it went live, automated checks verified its dates, sources and every language edition.