macOS Upgrade

• Upgrade 1 arm64 and 1 x86 chromium staging bots to macOS 15.5+ #167678
• Upgrade 1 arm64 and 1 x86 devicelab staging bots to macOS 15.5+ #167679
• Run all flutter/flutter macOS tests manually on macOS 15.5 bot #167682
  • Add any issues discovered to Tracking issue for any infra or test failures with macOS 15 #167681
• Run all flutter/packages macOS tests manually on macOS 15.5+ bot #167822
  • Add any issues discovered to Tracking issue for any infra or test failures with macOS 15 #167681
• Update .ci.yaml in flutter/flutter to use either macOS 14 or macOS 15 #167824
• Update .ci.yaml in flutter/packages to use either macOS 14 or macOS 15 #167825
• Update ci.yaml in flutter/cocoon to use either macOS 14 or 15
• Upgrade 50% of devicelab bots in each pool to macOS 15.5 #167826
  • Add any issues discovered to Tracking issue for any infra or test failures with macOS 15 #167681
• Upgrade 50% of chromium bots to macOS 15.5 #167827
  • Add any issues discovered to Tracking issue for any infra or test failures with macOS 15 #167681
• CP macOS 15 fixes for beta and stable #167837
• CP ci.yaml and configs to run on either macOS 14 or 15 for beta and stable #167838
• Upgrade 50% of bots in dart-internal to macOS 15.5 #167839
• Upgrade remaining devicelab bots in each pool to macOS 15.5+ #167840
• Upgrade remaining chromium bots in each pool to macOS 15.5 #167841
• Upgrade remaining bots in dart-internal to macOS 15.5+ #167843

Xcode Upgrade

• Verify Xcode 26 required macOS version is macOS 15.5 or lower. If not, all above macOS Upgrade steps will need to be done again to the required version: https://xcodereleases.com/
• Run all flutter/flutter macOS tests using Xcode 26 and iOS 26 simulator #172855
  • Add any issues discovered to ☂️ Tracking issue for any infra or test failures with Xcode 26 and iOS 26 Simulators #172857
• Run all flutter/packages macOS tests using Xcode 26 and iOS 26 simulator #172856
  • Add any issues discovered to ☂️ Tracking issue for any infra or test failures with Xcode 26 and iOS 26 Simulators #172857
• Update .ci.yaml in flutter/flutter to use Xcode 26 and macOS 15 #172858
• Update flutter/packages to use Xcode 26, iOS 26 Simulator, and macOS 15 #172859
• CP Xcode 26 and iOS 26 Simulator fixes for beta and stable #172864
• CP ci.yaml and configs to use Xcode 26, iOS 26 Simulator, and macOS 15 for beta and stable #172874

iOS Upgrade

TODO

Previous upgrade tracking issue for reference: #148870