**Trader consensus heavily favors 13-15 games as the MLB season's longest winning streak at 95.1% implied probability, reflecting the 2026 campaign's established ceiling.** The Boston Red Sox set the year's high with a 15-game run in July that tied a franchise record and lifted them into playoff contention, while no club has approached or exceeded that mark since. As of late August, the Philadelphia Phillies hold the active longest streak at seven wins, the New York Yankees sit at four or five, and other contenders show shorter recent form amid a compressed schedule and tightening division races. Historical data reinforces the outlook, as streaks of 16-plus games remain rare in the expansion era. A late-September surge by a rested contender could still push the mark higher, though current standings and recent results make such an extension unlikely.