# How to use Background Indexing in sourcekit-lsp? **URL:** \ **Category:** Using Swift\ **Tags:** sourcekit-lsp\ **Created:** [April 24, 2025, 9:12pm UTC](https://forums.swift.org/t/how-to-use-background-indexing-in-sourcekit-lsp/79497 "2025-04-24T21:12:41Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![dima\_kozhinov](https://avatars.discourse-cdn.com/v4/letter/d/258eb7/32.png) [@dima\_kozhinov](https://forums.swift.org/u/dima_kozhinov)\ **Post date:** [April 24, 2025, 9:12pm UTC](https://forums.swift.org/t/how-to-use-background-indexing-in-sourcekit-lsp/79497/1 "2025-04-24T21:12:41Z")
The sourcekit-lsp documentation at [sourcekit-lsp/Documentation/Enable Experimental Background Indexing.md at main · swiftlang/sourcekit-lsp · GitHub](https://github.com/swiftlang/sourcekit-lsp/blob/main/Documentation/Enable%20Experimental%20Background%20Indexing.md) says: > Background indexing in SourceKit-LSP is enabled by default in Swift 6.1 toolchains and above. > With background indexing disabled, SourceKit-LSP does not update its global index in the background or build Swift modules in the background. Thus, a lot of cross-module or global functionality is limited if the project hasn't been built recently. For example, consider two modules: `Lib` and `Exec`, where `Exec` depends on `Lib`: Without background indexing, if a function is added to `Lib`, completion/jump to definition/etc in `Exec` would not be able to see that function until after a build. Background indexing solves that issue. The documentation mentions example _modules_ `Lib` and `Exec`. But IMHO the same should apply to different source _files_ within one module. For example, if I have `main.swift` and `helpers.swift` files in my swiftPM project, then I open my project folder with VS Code, declare a new `let fooConst = 42` in `helpers.swift`, then start typing `foo` in `main.swift`, then I don't see `fooConst` in code suggestions, until I rebuild the project or close it and reopen in VS Code. Can this be fixed somehow? Should my code editor (e.g. VS Code or similar) issue a special reindex request to sourcekit-lsp? @ahoppen ---
**Author:** ![ahoppen](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/ahoppen/32/36046_2.png) [@ahoppen](https://forums.swift.org/u/ahoppen)\ **Post date:** [April 25, 2025, 5:47am UTC](https://forums.swift.org/t/how-to-use-background-indexing-in-sourcekit-lsp/79497/2 "2025-04-25T05:47:53Z")
That is odd, cross-file functionality within the same module doesn’t require background indexing. Could you file an issue for this at [GitHub · Where software is built](https://github.com/swiftlang/sourcekit-lsp/issues)? ---
**Author:** ![dima\_kozhinov](https://avatars.discourse-cdn.com/v4/letter/d/258eb7/32.png) [@dima\_kozhinov](https://forums.swift.org/u/dima_kozhinov)\ **Post date:** [April 25, 2025, 2:51pm UTC](https://forums.swift.org/t/how-to-use-background-indexing-in-sourcekit-lsp/79497/3 "2025-04-25T14:51:14Z")
This is really strange. I started filing an issue on Github, and found that actually the missing code suggestion _is_ shown, but only when you type more characters. When the new identifier is added in the same file, one character is enough, but when it is added in a different file, more characters are required. Here are steps to reproduce: 1. Create a Swift package: ```swift mkdir test cd test swift package init --type executable ``` 1. Add a new Swift file in the Sources folder of the package, e.g. `helpers.swift` in addition to the default `main.swift` . 2. Open the `test` package folder in Visual Studio Code. 3. Edit the `helpers.swift` in VS Code: add for example `let zzzConst = 42` . 4. Switch to `main.swift` file in VS Code and type something that would use the new constant from `helpers.swift`, e.g "let aaa = z" 5. Code completion does not show `zzzConst` (shows only two suggestions starting with "zip") 6. Add more text, now "let aaa = zz" 7. Code completion does not show any suggestions at all. 8. Add more text, now "let aaa = zzz" 9. At last `zzzConst` appears in code suggestions. Not sure if I still should file an issue. This behavior still looks wrong to me, though the missing code suggestion is ultimately shown. ---
**Author:** ![dima\_kozhinov](https://avatars.discourse-cdn.com/v4/letter/d/258eb7/32.png) [@dima\_kozhinov](https://forums.swift.org/u/dima_kozhinov)\ **Post date:** [April 25, 2025, 4:10pm UTC](https://forums.swift.org/t/how-to-use-background-indexing-in-sourcekit-lsp/79497/4 "2025-04-25T16:10:39Z")
Filed an issue [Code completion does not show cross-file new identifiers (unless more characters are typed) · Issue #2122 · swiftlang/sourcekit-lsp · GitHub](https://github.com/swiftlang/sourcekit-lsp/issues/2122)