SourceKit infinite indexing loop with TCA on Xcode 26

[Jaesung-Jung]

Description

When adding The Composable Architecture to a fresh SwiftUI template project in Xcode 26 (iOS 26 SDK),
SourceKit enters an infinite indexing loop.

This issue does not occur on Xcode 16 with the same project and dependency versions,
so it seems to have been introduced with Xcode 26.

Checklist

• I have determined whether this bug is also reproducible in a vanilla SwiftUI project.
• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue or discussion.

Expected behavior

The project should index successfully and allow normal code completion, navigation, and symbol search in Xcode.

Actual behavior

The project opens in Xcode 26, indexing never finishes.

Reproducing project

1. Open Xcode 26.
2. Create a new project using the SwiftUI App template.
3. Add The Composable Architecture via Swift Package Manager.
4. Indexing loop begins. (or After indexing finishes, close Xcode and re-open the project)

The project file and sourcekit log are attached.
(The attached log file was generated using the following command)
SOURCEKIT_LOGGING=3 /Applications/Xcode.app/Contents/MacOS/Xcode &> ~/Desktop/indexing.log

IndexingLoop.zip

indexing.log

The Composable Architecture version information

1.22.2

Destination operating system

iOS 26

Xcode version information

Xcode 26

Swift Compiler version information

swift-driver version: 1.127.14.1 Apple Swift version 6.2 (swiftlang-6.2.0.19.9 clang-1700.3.19.1)
Target: arm64-apple-macosx26.0

[stephencelis]

@Jaesung-Jung Given that this is related to a particular version of Xcode I don't know if we can consider it a TCA bug. We are open to changes to TCA that work around the Xcode bug, though please do file feedback with Apple if you can.

[Jaesung-Jung]

@Jaesung-Jung Given that this is related to a particular version of Xcode I don't know if we can consider it a TCA bug. We are open to changes to TCA that work around the Xcode bug, though please do file feedback with Apple if you can.

@stephencelis Thank you for the response. Are you also able to reproduce this issue on your side?

[iwatakeshi]

Hi there, I wanted to bring to your attention that I’m also facing this issue after upgrading to Xcode 26. I’ve attached a screenshot that illustrates the circular reference occurring, and I’ve also included the example project for your reference.

Learn Composable Architecture.zip

[mbrandonw]

Hi @iwatakeshi, this does not seem to be related to this discussion and so I recommend you open a new discussion if you want to ask questions about it.

Also, for now you you will need to turn of default main actor isolation in your new Xcode projects.

[iwatakeshi]

Hi @mbrandonw,

Thank you for your reply! I wanted to let you know that I’m also experiencing indexing issues, which is why I thought it could be related. I appreciate your input, and I’ll go ahead and open up a new issue to track and discuss on the learning project I'm working on.

Thanks again!

[mbrandonw]

Hi @Jaesung-Jung, this doesn't seem like anything we can reasonably fix in the library, and instead a feedback should be filed with Apple. I am going to convert to a discussion for now, but please do share if you file a feedback and we will dupe it.

[SublimeAbode]

@mbrandonw @stephencelis I've filed a report with Apple: FB20489299

Please describe the issue and what steps we can take to reproduce it

When no tasks are being run, Xcode remains forever stuck “Indexing | Processing files” when working on a project with the swift-composable-architecture library as a dependency. According to one user, this is a SourceKit infinite indexing loop bug that was not present in Xcode 16. The package maintainers hold that this is probably a bug with Xcode, not their package.

1. Clone the demo project I have created to reproduce this issue: https://github.com/SublimeAbode/TCAStuckIndexingDemo
2. Wait for Xcode to finish fetching dependencies and other related tasks.
3. Observe the described error. If it does not occur, restart Xcode. If it still doesn’t reproduce, begin using the library by removing some lines of the existing code and rewriting them manually, attempting to use code completion for locally defined symbols, and the issue will soon manifest. For instance, rewrite line 19 of ContentView.swift and attempt to invoke the code completion menu by typing “return .” and then pressing Option+Escape. The window may or may not appear, and if it does, it does not list the relevant symbols (in this case, the enum case “none”).

The indexing issue displays sporadically, but code completion remains broken most of the time–a significant productivity hurdle. Please prioritize.

If anyone finds a workaround please let me know, thanks.