I just tried the combination of

• Jenkins 2.375.2
• Kubernetes plugin 3734.v562b_b_a_627ea_c

The same problem occurs. So it might be a problem of Jenkins itself after all.

Update:
After rolling back my complete set of kubernetes* plugins, it also works with Jenkins 2.375.2. In especially:

• kubernetes:3734.v562b_b_a_627ea_c
• kubernetes-credentials:0.9.0
• kubernetes-client-api:5.12.2-193.v26a_6078f65a_9

Obviously current jenkins 2.375 is messing up with the kube configurations. We had connection issues from controller to kubernetes-agents because of having both a single kube config file in .kube dir (test) and a single cloud configuration in the ui (prod). Having both configurations in place we had ongoing connection issues saying

"Unauthorized! Token may have expired! Please log-in again. Unauthorized 401: must authenticate."

After having removed the test configurartion config file from .kube dir the error disappeared. When reactivating the config again (mv to config.bak and back zu config) the error reappeared. So this hints at a bug where jenkins is messing up with the configs and authentication tokens. 

Probably another occurrence of JENKINS-70416. Check again with latest version.

I retried with Jenkins 2.387.2 and with reverted version pinning for the kubernetes plugin (i.e. only specifying kubernetes in plugins.txt).
The exact same problem occurs :

Error testing connection : com.fasterxml.jackson.dataformat.yaml.JacksonYAMLParseException: special characters are not allowed

My situation just got worse:

• current Jenkins 2.414.3 no longer works with the pinned k8s plugin version 3734.v562b_b_a_627ea_c (breaking change in snake yaml)
• current Jenkins 2.414.3 with current k8s plugin still shows the same error:

  Nov 21, 2023 11:54:49 AM WARNING org.csanchez.jenkins.plugins.kubernetes.KubernetesLauncher launch
  
  Error in provisioning; agent=KubernetesSlave name: atgrz-k8s-linux-jnlp-45dvb, template=PodTemplate{id='954105e0-8cc7-429a-971c-03563fe76b78', name='atgrz-k8s-linux-jnlp', label='atgrz-k8s-buildnode-linux generic-linux-build', volumes=[org.csanchez.jenkins.plugins.kubernetes.volumes.PersistentVolumeClaim@6080b897, org.csanchez.jenkins.plugins.kubernetes.volumes.ConfigMapVolume@1fc84d4f], containers=[ContainerTemplate{name='jnlp', image='env-docker-release.arti.mycompany.com/env/dev/linux_r7g8:jnlp', alwaysPullImage=true, command='', args='', resourceRequestCpu='1000m', resourceRequestMemory='2000Mi', resourceLimitCpu='4000m', resourceLimitMemory='6000Mi', envVars=[KeyValueEnvVar [getValue()=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/home/jenkins/.local/bin, getKey()=PATH]]}], imagePullSecrets=[PodImagePullSecret{name='s19m13-env-docker-arti'}, PodImagePullSecret{name='s19m13-docker-arti'}]}
  unacceptable code point '' (0x7) special characters are not allowed
  in "reader", position 15
  	at org.snakeyaml.engine.v2.scanner.StreamReader.update(StreamReader.java:274)
  	at org.snakeyaml.engine.v2.scanner.StreamReader.ensureEnoughData(StreamReader.java:237)
  	at org.snakeyaml.engine.v2.scanner.StreamReader.ensureEnoughData(StreamReader.java:232)
  	at org.snakeyaml.engine.v2.scanner.StreamReader.peek(StreamReader.java:187)
  	at org.snakeyaml.engine.v2.scanner.ScannerImpl.scanToNextToken(ScannerImpl.java:1114)
  	at org.snakeyaml.engine.v2.scanner.ScannerImpl.fetchMoreTokens(ScannerImpl.java:292)
  	at org.snakeyaml.engine.v2.scanner.ScannerImpl.checkToken(ScannerImpl.java:192)
  	at org.snakeyaml.engine.v2.parser.ParserImpl$ParseImplicitDocumentStart.produce(ParserImpl.java:444)
  	at org.snakeyaml.engine.v2.parser.ParserImpl.lambda$produce$1(ParserImpl.java:232)
  	at java.base/java.util.Optional.ifPresent(Optional.java:183)
  	at org.snakeyaml.engine.v2.parser.ParserImpl.produce(ParserImpl.java:232)
  	at org.snakeyaml.engine.v2.parser.ParserImpl.peekEvent(ParserImpl.java:206)
  	at org.snakeyaml.engine.v2.parser.ParserImpl.checkEvent(ParserImpl.java:198)
  	at org.snakeyaml.engine.v2.composer.Composer.hasNext(Composer.java:110)
  	at org.snakeyaml.engine.v2.api.Load$YamlIterator.hasNext(Load.java:226)
  	at io.fabric8.kubernetes.client.utils.KubernetesSerialization.parseYaml(KubernetesSerialization.java:271)
  	at io.fabric8.kubernetes.client.utils.KubernetesSerialization.unmarshal(KubernetesSerialization.java:252)
  	at io.fabric8.kubernetes.client.utils.KubernetesSerialization.unmarshal(KubernetesSerialization.java:342)
  	at io.fabric8.kubernetes.client.utils.KubernetesSerialization.unmarshal(KubernetesSerialization.java:327)
  	at io.fabric8.kubernetes.client.utils.Serialization.unmarshal(Serialization.java:185)
  	at io.fabric8.kubernetes.client.internal.KubeConfigUtils.parseConfigFromString(KubeConfigUtils.java:47)
  	at io.fabric8.kubernetes.client.Config.loadFromKubeconfig(Config.java:706)
  	at io.fabric8.kubernetes.client.Config.fromKubeconfig(Config.java:619)
  	at io.fabric8.kubernetes.client.Config.fromKubeconfig(Config.java:609)
  	at org.jenkinsci.plugins.kubernetes.auth.impl.KubernetesAuthKubeconfig.decorate(KubernetesAuthKubeconfig.java:28)
  	at org.csanchez.jenkins.plugins.kubernetes.KubernetesFactoryAdapter.createClient(KubernetesFactoryAdapter.java:119)
  	at org.csanchez.jenkins.plugins.kubernetes.KubernetesClientProvider.createClient(KubernetesClientProvider.java:59)
  	at org.csanchez.jenkins.plugins.kubernetes.KubernetesCloud.connect(KubernetesCloud.java:536)
  	at org.csanchez.jenkins.plugins.kubernetes.KubernetesLauncher.launch(KubernetesLauncher.java:118)
  	at hudson.slaves.SlaveComputer.lambda$_connect$0(SlaveComputer.java:297)
  	at jenkins.util.ContextResettingExecutorService$2.call(ContextResettingExecutorService.java:46)
  	at jenkins.security.ImpersonatingExecutorService$2.call(ImpersonatingExecutorService.java:80)
  	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
  	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
  	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
  	at java.base/java.lang.Thread.run(Thread.java:829)
  

I fear I am stuck on Jenkins 2.387.3 for the time being - Please help.

Remark: I doubt that this is duplicate. Sorry for the inconvenience caused by repoening this.