Greptile is an AI code review agent for engineering teams. On each pull request it reviews the change against a graph of the full codebase, and TREX (Test, Run, Execute) runs that branch in a sandbox so failures that only appear at runtime show up before merge. This beta adds computer use to that step. TREX starts the services a change touches and operates the running app, opening a desktop app, clicking through a browser flow, or typing in a terminal, then posts what it tested and what broke, with video, on the pull request. The launch example is a pull request that adds CLI OAuth through a web login. TREX starts a terminal and a browser together, runs the login command, enters credentials on the redirected page, and checks that the session returns to the CLI. In parallel it tests the fallback where the browser does not connect automatically and the user has to paste an auth code. The pasted URL includes newlines, the login fails, and TREX flags the bug. A reviewer looking only at the diff would not see it. Daksh Gupta, Soohoon Choi, and Vaishant Kameswaran founded the San Francisco company in 2023 after meeting at Georgia Tech, and later joined Y Combinator's Winter 2024 batch. Teams at Nvidia, Coinbase, Scale, Brex, Substack, and Whoop use Greptile, and the company says more than 22,000 teams are on the product. Computer use is aimed at the reviews those teams already run, as coding agents raise pull request volume and more bugs survive a clean diff until someone actually uses the change.