1Catching Bugs Before They Land: JiTTesting’s Human-on-the-Loop Approach at Full Scaleengineering.fb.comHigh10·29 16:00Z
Meta disclosed that its Catching Just-in-Time Tests (JiTTests) system, which uses large language models to generate software tests on the fly, is now deployed in production infrastructure1. In the first half of 2026, the system caught 74 serious privacy bugs at the diff stage before they reached production and lowered overall privacy SEV occurrence by 20%. Of the 589 engineers who engaged with the tool, representing 64% of Meta's outreach, 60% of flagged issues were reported as true positives. The accompanying paper, "Just-in-Time Catching Test Generation at Meta," details the deployment.