How to make incremental builds work on a Mac mini CI with Xcode 26

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Hi all,

I’m looking for help from people familiar with Swift/Xcode.

Our team runs CI builds on a single Mac mini.

Incremental builds on local machines are fast (around 1–2 minutes), but on the Mac mini CI it seems incremental builds are not working, and the build takes about 8 minutes.

I read that Xcode 26 introduced Compilation Caching. Based on my understanding, I expected that keeping some DerivedData on CI might allow incremental builds and reduce build time.

So I enabled Compilation Caching and updated our xcodebuild command to specify -derivedDataPath using a fixed absolute path. However, the build time did not improve at all.

Could you advise what we should do to speed this up?

Am I misunderstanding how this feature is supposed to work in CI?

Thanks in advance.