The iPhone Duo layout uses UIHingeInteraction, which only exists in
the iOS 27.1 SDK. CI ran Xcode 16.4 (iOS 18.5 SDK) on macos-15, so the
app build failed: #available is a runtime check and cannot hide a
symbol the SDK lacks. ChatView's iOS 26/27 modifiers would have failed
next.
Both jobs now run on the xcode-27 runner image (Xcode 27.1 by default),
the toolchain releases are built with. The READMEs state Xcode 27.1 as
the minimum.
Swift 6.4 also timed out type-checking a long `+` chain in
MultipartEncoderTests, so `swift test` failed to build; the expected
body is now joined from an array.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Add viewport-driven paging with layout acknowledgements, bounded retries, cancellation gates, and epoch-safe history retention.
Preserve transcript anchors and expansion state, fix tool-group identity collisions, and serialize Android history coordination on Main.
Reduce per-scroll composition and layout work; add native regression tests, CI coverage, and profiling guidance.
