Ivan Valchev contributed to the PriorLabs/TabPFN repository by addressing a critical bug in the cumulative distribution function’s bucket contribution calculation. He identified and corrected an error in the share_of_bucket_left logic within the _cdf function, ensuring that the difference between values and the lower bucket border is properly divided by the bucket width. This fix, implemented in Python, improved the reliability of downstream analytics and model calibration. Drawing on his expertise in numerical computation and probability, Ivan demonstrated careful attention to mathematical correctness and disciplined version control, delivering a focused solution that enhanced the accuracy of TabPFN’s statistical outputs.