CI: move to the xcode-27 runner image#123
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GitHub now offers an `xcode-27` runner image (public preview), keyed to the Xcode major version rather than the OS. Move both CI jobs to `runs-on: xcode-27` so we build and test on Xcode 27 (Swift 6.4). The image ships only the iOS 27.0 simulator runtime, so pin the test destination to iPhone 17 / OS 27.0. This also unblocks Xcode's String Catalog symbol generation for SwiftPM package targets, which is only reliable on Xcode 27. Deployment target stays iOS 26.0 — building it with the iOS 27 SDK is fine; raising the minimum OS is a separate follow-up. Add a CoreSimulator warm-up step since the preview image can need a nudge to rebuild its device cache. Update docs (AGENTS.md, README.md, RegionViewer) and the profile/flaky script defaults to match.
This was referenced Jul 23, 2026
kyleve
commented
Jul 23, 2026
| - uses: actions/checkout@v4 | ||
| - uses: jdx/mise-action@v3 | ||
| # The xcode-27 image is a public-preview image whose CoreSimulator can | ||
| # need a nudge to rebuild its device cache before a destination resolves. |
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What
Moves CI onto GitHub's new
xcode-27runner image (public preview) so we build and test on Xcode 27 (Swift 6.4).Why
GitHub's Xcode 27 runner image is now available, and its new support model keys images to the Xcode major version rather than the OS — hence the
xcode-27label instead ofmacos-27.Beyond keeping the toolchain current, this unblocks Xcode's String Catalog symbol generation for SwiftPM package targets, which is only reliable on Xcode 27 (it mis-ordered generation in the test-bundle build graph on Xcode 26.x). The type-safe strings migration lands as a follow-up PR on top of this.
Changes
format,test) →runs-on: xcode-27.iPhone 17 / OS 27.0(the device still exists there).xcrun simctl listCoreSimulator warm-up step — the preview image can need a nudge to rebuild its device cache before a destination resolves.AGENTS.md,README.md,RegionViewer/README.md, and theprofile/flakyscript defaults.Not in scope
HistoryObserver) is a separate follow-up.Verification
./swiftformat --lintclean.xcode-27image.