Career Mode, the new Aston Martin LMH, Bahrain, Circuit Bugatti and the first piece of the physics engine overhaul. Here is everything iRacing has actually put in writing ahead of the September build. September has historically been the biggest build of the year on iRacing. The 2025 Season 4 release brought the new Sim UI. The 2024 edition reshaped the racing categories. And every sign points to 2026 Season 4 being another one of those: Career Mode has been in the pipeline for over a year, and iRacing has confirmed it will be detailed in full in the August development blog. While we wait for that blog, which usually lands in the final week of the month, here is everything the company has already committed to publicly, sorted by how firm it actually is. Because on iRacing there is a meaningful difference between “confirmed for this build” and “confirmed, but with no date attached”. When the build arrives There is no official date yet. What there is, though, is a very reliable pattern. Season 4 has landed on 8 September 2021, 7 September 2022, 6 September 2023, 4 September 2024 and 9 September 2025. Always on a Tuesday, always in the first half of the month. The season itself then starts roughly a week after the build. In 2025 the build dropped on 9 September and the season went green on the 16th. Applying the same logic, the sensible expectation is a build around 8 September with 2026 Season 4 starting around 15 September 2026. Before that comes Week 13, the one week gap between seasons where iRacing traditionally tests features in the open before committing to them. Keep that in mind, because it becomes relevant further down. Explicitly confirmed for Season 4 Track Reverb and Reverb Zones. This is