How Braintrust turns customer requests into code with Codex

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.

“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.”

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.”

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.

For Goyal, Codex changes how much setup it takes to try new ideas. “With other models, I would have to try to prompt the model to solve a specific problem,” he says. Slower tools require more hands-on guidance, which raises the cost of experimentation.

“With Codex, I’ve shifted to writing a test that demonstrates a problem, creating a sandbox environment, and then letting Codex run in that environment,” Goyal says. “This is a novel use case for me, and I can run experiments because of the speed.”

That speed gives the Braintrust team more room to experiment. Instead of prompting step by step, engineers can define the problem, let Codex work in a controlled environment, and move faster from idea to working solution.