Executable Built with `swift-subprocess` Fails to Launch on macOS

[omochi]

Describe the bug

On macOS, using swift-subprocess causes executables to fail to launch.
At startup, an error occurs stating that libswiftCompatibilitySpan.dylib cannot be found.

Interestingly, it runs fine when opened and executed in Xcode; the issue occurs only with the SwiftPM CLI.

To Reproduce

A simple program like the one below reproduces the issue.

import Subprocess

@main
struct App {
    static func main() async throws {
        let result = try await Subprocess.run(
            .name("tar"),
            arguments: ["-cvf", "archive.tar", "Sources/"],
            output: .standardOutput,
            error: .standardError
        )

        guard result.terminationStatus.isSuccess else {
            throw "failed to tar"
        }
    }
}

You can reproduce the issue by checking out the following repository and running swift build && swift run.
https://github.com/omochi/swift-subprocess-rpath-bug

Expected behavior

The executable should launch and run successfully.

Environment (please complete the following information):

• macOS 26.0 Tahoe 25A354
• Xcode 26.1 Beta 1
• swift-driver version: 1.127.14.1 Apple Swift version 6.2.1 (swiftlang-6.2.1.1.1 clang-1700.4.1.1)

Additional information

The following issue seems related.
swiftlang/swift-package-manager#9163

It was closed as fixed in Swift 6.2.1; however, the problem still occurs in Xcode 26.1 beta 1, which bundles Swift 6.2