LeakLens

Is your CV score lying to you?

Paste a notebook or script. LeakLens reads the code (it never runs it) and points to the exact lines where validation leakage creeps in, before the private leaderboard shake-up shows you.

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What it checks

Use it from the terminal or CI

Same engine, plain HTTP. Fail a GitHub Action when the risk score crosses a threshold.


  


  

    
Why this exists

    

      

        
Every competition has one: the notebook with a 0.99 CV that drops to 0.71 on the private leaderboard. I have been that notebook. A "best" score of mine turned out to depend on a leaky validation setup, and in another competition the best public checkpoint had been trained on images that overlapped the test set.

        
The fixes are well known (Pipelines, GroupKFold, out-of-fold target encoding), but the mistakes are hard to see in a 400-cell notebook at 2am. LeakLens makes them visible. It is deterministic, explains every finding, and shows the fix.

      

      

        
What the community has found so far

        
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