What model powers the new Codex workflow?

A: Codex runs on top of GPT‑5.5, the latest version released in early May 2026.

How much faster is development?

A: Braintrust reports that experiments that once took weeks now finish in hours, though exact numbers vary by project.

Braintrust announced that its engineers now pair Codex with the newly released GPT‑5.5 to turn customer requests directly into code.

According to the OpenAI Blog (May 29, 2026), the integration lets the team generate functional code from natural‑language specifications.

GPT‑5.5 expands the model’s context window and refines reasoning, making code generation more reliable than previous versions.

Codex, already tuned for programming tasks, can immediately benefit from those upgrades without requiring a separate model.

Enterprises are demanding faster iteration, and the timing aligns with a broader push toward AI‑assisted development tools.

When a client submits a feature request, Braintrust engineers feed the natural‑language description into Codex.

Codex, running on GPT‑5.5, parses the request, drafts the corresponding source files, and runs automated tests.

If the code passes, it moves straight to staging; if not, the model suggests fixes and the engineers iterate.

The loop shortens the experiment phase from weeks to hours, as reported by the OpenAI Blog.

Braintrust development teams spend less time translating specs into code, freeing capacity for higher‑level design work.

Clients receive functional prototypes faster, reducing time‑to‑market for new features.

Other firms watching the rollout can adopt a similar pattern to accelerate their own delivery pipelines.

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