OpenAI ships Codex: a cloud agent that turns tickets into pull requests, one sandbox per task
OpenAI launched Codex on May 16 as a research preview: a cloud-based software engineering agent inside ChatGPT, powered by codex-1, an o3 variant post-trained with reinforcement learning on real coding tasks. Each task runs in its own isolated container preloaded with your GitHub repository, can run tests and linters, and returns a branch plus a pull request with terminal logs and citations as evidence; tasks run in parallel, roughly 1 to 30 minutes each. Day-one access is ChatGPT Pro, Business and Enterprise, with Plus access opening on June 3.
The design choice that matters is the boundary: internet access is disabled during task execution, and dependencies must be installed in advance through a setup script, so the agent cannot reach external sites or APIs mid-task. OpenAI also shipped a smaller o4-mini-based model for the open-source Codex CLI it released in April.
WHY IT MATTERS
The agent-harness baseline moved: a hosted multi-task coding agent with per-task containers, no network egress and pull-request-shaped output is now bundled with a ChatGPT seat, so a self-built coding-agent loop needs a defensible reason to exist. For anyone running agents in production, PR-shaped output moves the bottleneck from generation to review — and the disabled-egress sandbox shows that the harness, not the model, is where permissions, dependency vendoring and auditability get enforced.

