Verbose build log mushes lines together

Is it reproducible with SwiftPM command-line tools: swift build, swift test, swift package etc?

• Confirmed reproduction steps with SwiftPM CLI. The description text must include reproduction steps with either of command-line SwiftPM commands, swift build, swift test, swift package etc.

Description

Log lines are unpredictably mushed together without newlines.

Expected behavior

Lines to be complete and separate.

Actual behavior

eg. Emitting module for NewlinesDiscovering Swift tasks after 'Emitting module for Newlines'Unblock downstream dependents of Newlines (arm64)

I noticed this when it mushed a status line onto a compile command that ended up looking like

builtin-Swift-Compilation -- /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swiftc
[...]
-disable-cmoPlanning Swift module Newlines (arm64)

It does just seem to be these 'task description' phrases that are appearing in the wrong place - not as though there are loads of spare newlines floating around in the log either.

Steps to reproduce

swift package init Foo swift build -v

Swift Package Manager version/commit hash

Swift Package Manager - Swift 6.4.0-dev

Swift & OS version (output of swift --version ; uname -a)

swift-driver version: 1.168.2 Apple Swift version 6.4 (swiftlang-6.4.0.23.5 clang-2100.3.23.3) (Xcode 27b2)

Darwin MacBook-Pro-25.local 25.5.0 Darwin Kernel Version 25.5.0: Mon Apr 27 20:41:15 PDT 2026; root:xnu-12377.121.6~2/RELEASE_ARM64_T6041 arm64