
How Braintrust engineers use Codex with GPT-5.5 to run experiments and code faster. With Codex, its engineers can now take customer feature requests and create preview branches to show working ideas to customers in minutes. Speed is often treated as a property of a tool, one that exists separate from its core functionality, but for Goyal, the speed difference “changes the way I interact with Codex compared to other models.” Instead, the team can copy and paste requests into Codex, create a preview branch, and show the completed request to the customer in minutes.
Braintrust is the observability and eval platform for shipping quality AI products.
With Codex, its engineers can now take customer feature requests and create preview branches to show working ideas to customers in minutes.
In one month, half of the Braintrust team moved to Codex. For founder and CEO Ankur Goyal, the biggest change is not just faster coding. It’s a faster feedback loop with customers.
With Codex, the Braintrust team can integrate iteration into its development workflow rather than letting requests sit and wait. “Codex unlocked our ability to try out customer feature requests in real time,” says Goyal. “Previously, if someone gave us a feature request, it would enter a backlog and get prioritized later.”
“It sounds simple, but Codex can literally print more text in the terminal without getting slow, and other models just can’t replicate that,” says Goyal.
Speed is often treated as a property of a tool, one that exists separate from its core functionality, but for Goyal, the speed difference “changes the way I interact with Codex compared to other models.”
Instead, the team can copy and paste requests into Codex, create a preview branch, and show the completed request to the customer in minutes. “The really cool thing with Codex is that we get to iterate and ideate on feature requests with the customer in real time,” says Goyal.
How Braintrust engineers use Codex with GPT-5.5 to run experiments and code faster Reported by OpenAI on May 29, 2026.