Check and apply with the CLI do not work (nor does curl)

With the following file:

jenkins:
    systemMessage: "Test 123"

And the following command line (I did get the jenkins-cli.jar from the same jenkins host):

java -jar jenkins-cli.jar -s http://localhost:8080/ check-configuration <jenkins.yaml

There is an error:

ERROR: Unexpected exception occurred while performing apply-configuration command.
io.jenkins.plugins.casc.ConfiguratorException: Found conflicting configuration at YamlSource: java.io.BufferedInputStream@52a762  in java.io.BufferedInputStream@52a762, line 2, column 20:
        systemMessage: "Test 123"
                       ^

The same problem exists with apply. The same problem exists when trying with curl:

curl -v -X POST -T jenkins.yaml "http://localhost:8080/configuration-as-code/apply"

Uploading directly in the GUI does work.

• Jenkins version: 2.138.3
• Plugin version: 1.3
• OS: linux

[timja]

Not stale

[ewelinawilkosz]

at the CLI commands list at Jenkins check-configuration has a misleading explanation “Apply YAML configuration to instance” - it seems to me they try to apply or check NEW yaml,

reloading works well as far as I know, with reload-jcasc-configuration command