Amazfit T-Rex 3 gets smarter with Zepp OS 4.5 update
Amazfit T-Rex 3 owners are getting a solid firmware upgrade with version 3.6.5.9. It brings Zepp OS 4.5 to the watch, adds live performance tracking for trail runners, introduces HYROX race support, improves GPS accuracy, enhances map visuals, and tweaks the Readiness algorithm.
The update itself comes in at around 20 megabytes so might take a while to install. Not all users are seeing it, but it is gradually rolling out.
A quiet shift to Zepp OS 4.5
The biggest change is that the T-Rex 3 now runs Zepp OS 4.5. While that might not seem like a headline feature at first glance, it signals deeper integration and improved performance under the hood. But it’s not a dramatic change.
This version of the operating system debuted with the launch of the Amazfit Active 2 earlier this year. It also comes pre-installed on the Bip 6.
More data for trail runners
Trail runners now get a “Real-time Performance” data field. This addition helps monitor physical status on the fly. You can also review performance distribution after the workout. It adds a layer of insight that could help dial in pacing and effort over varied terrain.
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The option is buried a bit in the menus, but it’s there: under Trail Running > Assistant > More > Real-time Performance. Once activated, it becomes a live metric on your workout screen. The same data field is also tucked under the general data page settings, so you can include it in other workout types too.
Hyrox race tracking and more
Like a few other Amazfit watches, the T-Rex 3 now supports HYROX workouts. Plus it has an added ability to track how much time is spent in the Roxzone. That’s the transition area between functional fitness stations and running laps. This will matter mostly for those actively training for HYROX events, but it’s an interesting niche addition.
Map rendering also gets a boost. The update adds better terrain detail, including visual cues for glaciers, shrubs, and wetlands.
GPS pacing is more stable now, especially in urban canyons or tree-covered areas. That’s been a sticking point for many users and should improve reliability for outdoor runs. Hiking in Long Battery Life mode also gets a boost, with better distance accuracy.
On the download side, there’s now support for Bluetooth-based map downloads via the Zepp app. That should make syncing new map data a bit less finicky as it offers another option.
The Readiness algorithm also got tweaked. This has been one of our grapes when we reviewed the Amazfit T-Rex 3, Active 2 and the Helio ring. Despite its constituent parts being accurate, the Readiness metric itself felt off at times. A bit too generous with the score, in our opinion.
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