Debugging inside a dev container does not work

[adam-fowler]

Describe the bug
Debugging inside a devcontainer running swift:6.1 does not work.

Using both CodeLLDB and LLDB DAP I get a dialog with the error "Cannot launch '//.build/aarch64-unknown-linux-gnu/debug/PackageTests.xctest': Sending vRun packet failed

To Reproduce
Steps to reproduce the behavior:

1. Open project
2. Opem inside a dev container using swift:6.1
3. Debug project
4. See error

Expected behavior
Debugging applications inside a devcontainer works

Environment

• OS: Ubuntu Noble
• Swift version 6.1 (swift-6.1-RELEASE)
• Visual Studio Code version: 1.100.2
• vscode-swift version: 2.2.0

[award999]

@adam-fowler I saw this and clearing .build directory and rebuilding seemed to help. Can you confirm if that helps?

[rmecham]

I'm running into something very similar. Cleaning out the .build folder did not help.

Whenever I try to use the debugger I get a dialog saying, “The CodeLLDB extension is required to debug with Swift toolchains prior to Swift 6.0. Please install the extension to continue.”

In the “Output” pane, the “Swift” extension says, ‘Error: "Debugger not started"’.

$ swift --version
Swift version 6.1.2 (swift-6.1.2-RELEASE)
Target: aarch64-unknown-linux-gnu

VSCode About:

Version: 1.101.0 (Universal)
Commit: dfaf44141ea9deb3b4096f7cd6d24e00c147a4b1
Date: 2025-06-11T15:00:50.123Z
Electron: 35.5.1
ElectronBuildId: 11727614
Chromium: 134.0.6998.205
Node.js: 22.15.1
V8: 13.4.114.21-electron.0
OS: Darwin arm64 24.5.0

Devcontainer: Ubuntu Jammy

Swift plugin version: 2.4.0

[award999]

@adam-fowler is this still an issue with 2.4? I've not been able to reproduce. Is there a open source project and devcontainer configuration I can try?

[award999]

@rmecham if you're seeing “The CodeLLDB extension is required to debug with Swift toolchains prior to Swift 6.0. Please install the extension to continue.” have you configured a different version of swift for the extension to use? If you have 6.1.2 of the plugin like above and 2.4 of the extension then you should be prompted. If you run Swift: Capture Diagnostic Bundle and send the bundle I can check your settings