A method for thread-safe development of a computer program configured for parallel thread execution comprises maintaining a digital record of read or write access to a data object from each of a plurality of sibling threads executing on a computer system. Pursuant to each instance of read or write access from a given sibling thread, an entry comprising an indicator of the access type is added to the digital record. The method further comprises assessing the thread safety of the read or write access corresponding to each entry in the digital record and identifying one or more thread-unsafe instances of read or write access based on the assessment of thread safety.