A failure is called pre-existing only under the same load

• An unattended validate checks the base the way HEAD went red: same command, the whole suite when the whole suite failed, never the failing file alone.
• A test red in the suite and green on its own runs three times on each side, counts and durations recorded. Green on the base and red on HEAD even once → this diff made it, and the repair looks at what the diff adds under concurrency, never a longer timeout or a retry.