Regression in default logging configuration since 2.25.0

[rschmitt]

Description

The default logging configuration in log4j-core has clearly regressed, with newlines no longer being emitted.

Configuration

Version: 2.25.0 and 2.25.1

Operating system: macOS Sequoia 15.5

JDK: Corretto 17.0.16 inter alia

Logs

[0] ~/src/logging-log4j2 # ./run.sh
Darwin 842f57b044d8 24.5.0 Darwin Kernel Version 24.5.0: Tue Apr 22 19:53:27 PDT 2025; root:xnu-11417.121.6~2/RELEASE_ARM64_T6041 arm64

Testing 2.20.0
13:46:13.785 [main] ERROR org.example.App - error level message
13:46:13.785 [main] FATAL org.example.App - fatal level message

Testing 2.21.1
13:46:14.428 [main] ERROR org.example.App - error level message
13:46:14.429 [main] FATAL org.example.App - fatal level message

Testing 2.22.1
13:46:15.124 [main] ERROR org.example.App - error level message
13:46:15.125 [main] FATAL org.example.App - fatal level message

Testing 2.23.1
13:46:16.213 [main] ERROR org.example.App - error level message
13:46:16.214 [main] FATAL org.example.App - fatal level message

Testing 2.24.3
13:46:16.827 [main] ERROR org.example.App - error level message
13:46:16.828 [main] FATAL org.example.App - fatal level message

Testing 2.25.0
2025-07-18T20:46:17.428495Z main ERROR error level message2025-07-18T20:46:17.429704Z main FATAL fatal level message
Testing 2.25.1
2025-07-18T20:46:18.478564Z main ERROR error level message2025-07-18T20:46:18.479927Z main FATAL fatal level message

Reproduction

Run ./run.sh:
https://github.com/rschmitt/logging-log4j2/tree/default-config-repro

[ppkarwasz]

Hi @rschmitt,

Nice catch! 💯
Can you make a PR to fix the problem?

[vy]

I tortured @ppkarwasz in a video call to make him confess that org.apache.logging.log4j.core.config.DefaultLayout#toSerializable(LogEvent) needed a newline suffix. @rschmitt, would you like to take care of this complicated fix?