fix(ci): pin Tier-3 iOS cache key to Xcode version#631
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The Tier-3 `Cache iOS DerivedData + Pods` step keyed only on
`runner.os + lock files`. When the macOS-latest runner image upgrades
Xcode (and the iOS SDK with it), the cached `SwiftShims-*.pcm` module
files reference SDK `module.modulemap` mtimes from the previous
toolchain. Swift then rejects the cached modules and the
`Build iOS simulator app` step fails with:
File '...iPhoneSimulator18.5.sdk/usr/lib/swift/shims/module.modulemap'
has been modified since the module file '...SwiftShims-*.pcm' was
built: mtime changed (was X, now Y)
Resolving the active `xcodebuild -version` into the cache key (and the
restore-keys fallback) invalidates the cache exactly when the SDK rolls,
so cache-hits only restore objects that were built against the current
toolchain.
TaprootFreak
added
the
tier3:full
This was referenced Jun 1, 2026
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Problem
The Tier-3 `Build iOS simulator app` step failed on PR #626 with:
```
Swift Compiler Error (Xcode): File '/Applications/Xcode_16.4.app/.../iPhoneSimulator18.5.sdk/usr/lib/swift/shims/module.modulemap'
has been modified since the module file '.../ModuleCache.noindex/.../SwiftShims-2ZSRUUIS75TOI.pcm' was built:
mtime changed (was 1779274009, now 1779861061)
```
The cached `SwiftShims-*.pcm` referenced a previous SDK's `module.modulemap` mtime — its own `module.modulemap` had been rewritten by the runner image's Xcode upgrade between two macOS-latest runs.
Root cause
`Cache iOS DerivedData + Pods` keyed only on `runner.os + lock files`. `runner.os` is just `"macOS"` regardless of the runtime Xcode/SDK version, so a cache restored across an Xcode bump produces `.pcm` files that point at SDK file mtimes from the previous toolchain. Swift refuses to use them and the build fails.
Fix
Resolve `xcodebuild -version` at runtime and inject it into both the cache key and the restore-keys fallback. The cache now invalidates exactly when the active Xcode rolls, so a hit can only restore objects that were built against the current toolchain.
The version string is normalised (`tr '\n' '-' | sed 's/[^A-Za-z0-9.-]//g; s/-$//'`) so `Xcode 16.4 / Build version 16F6` becomes a safe cache-key fragment like `Xcode-16.4-Build-version-16F6`.
Validation plan