The release candidate build of iOS 26.3 was discovered to contain identifiers for two unreleased Apple chips, which may be the M5 Max and M5 Ultra.
On Wednesday, a week after the release of the third developer beta, Apple deployed the iOS 26.3 release candidate version. While the update itself doesn't appear to contain any new features, the software includes files that reference unannounced Apple processing hardware.
Given that macOS 26.3 is tied to upcoming MacBook Pro models, as pointed out by AppleInsider in 2025, it's not surprising that the iOS 26.3 RC contains mentions of the M5 Max chip. The code also references what appears to be the M5 Ultra, a chip that might debut with an upgrade to the Mac Studio.
As MacRumors points out, the iOS 26.3 RC build mentions the T6051 chip, also referred to as H17C. There's also the T6052 system-on-chip, known as H17D within the code.
Based on Apple's existing naming patterns, the H17C chip is expected to be the M5 Max. Apple has used the letter "C" for its past "Max" chips, such as the M1 Max (H13C) and M4 Max (H16C).
The chip labeled H17D, meanwhile, could be the M5 Ultra chip, as the M1 Ultra through M3 Ultra chips all used a naming scheme with the letter "D."
Interestingly, the iOS 26.3 RC contains no references to the T6050 or H17S chip, which is the expected chip identifier for the M5 Pro. It's unclear if Apple changed its internal naming system for the M5 family of chips, but it's possible.
In any case, upgraded MacBook Pro models with new chips are expected to debut with macOS 26.3 in February or March 2026,
