Candidates report a Jane Street software engineer loop that front-loads the technical screen: 13 of the 23 reported questions come from screens, 5 from onsites, 4 from HR screens and 1 from an online assessment. The category mix is unusual for a software role. Coding and algorithms accounts for 13 questions, but statistics and math accounts for 4, and those are probability and game-theory puzzles rather than data analysis, with system design at 2 and single reports in software engineering fundamentals, ML system design and SQL. Difficulty is spread rather than concentrated: 8 hard, 8 medium and 7 easy. The trading domain shows up directly in the questions. Onsite work includes designing an exchange-trading system message flow, validating order book data across multiple databases, and sorting trade executions into a canonical order. Screens mix puzzle-style probability, such as optimal stopping with square-number ruin and optimizing a two-box place-or-take game, with implementation tasks such as transforming a sparse time-code stream into dense rows and detecting the first k-in-a-row winner in a bottom-insertion connect game, which reappears as a Connect Four variant. The HR screen carries reported questions too, including why Jane Street and an Excel exercise computing haircuts. 7 first-hand interview experiences describe individual loops.