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.

Unreleased Apple chips are referenced in the iOS 26.3 RC build.

Unreleased Apple chips are referenced in the iOS 26.3 RC build.
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.