[BUG] JetBrains plugin 0.1.14-beta: NoClassDefFoundError io.ktor.server.cio.CIO on startup (IDEA build 253.31033.145)
Preflight Checklist
- [x] I have searched existing issues and this hasn't been reported yet
- [x] This is a single bug report (please file separate reports for different bugs)
- [x] I am using the latest version of Claude Code
What's Wrong?
Environment
- Plugin: Claude Code [Beta] 0.1.14-beta (
com.anthropic.code.plugin) - IDE build: 253.31033.145 (IntelliJ IDEA 2025.3 line)
- IDE install path reports
IntelliJ IDEA 2025.1.1.1while the build is 253.x, which may be relevant - OS: Windows
- Installed from: JetBrains Marketplace
Symptom
The plugin throws 'PluginException' on every project open. 'MCPService.start' fails with 'NoClassDefFoundError: io/ktor/server/cio/CIO'.
The plugin class loader cannot resolve 'io.ktor.server.cio.CIO'.
I've checked JetBrains Marketplace to see if there is a latest version available, but it seems there is only the 0.1.14-beta version that is available. So, no latest update that I can install from withing the IDE.
What Should Happen?
The plugin should load cleanly on IDEA build 253.x, or Anthropic publishes a 0.1.15+ build to the Marketplace that includes the ktor-server-cio runtime dependency.
Error Messages/Logs
Stack trace
`
com.intellij.diagnostic.PluginException: io/ktor/server/cio/CIO [Plugin: com.anthropic.code.plugin]
at com.intellij.ide.startup.impl.StartupManagerImplKt$launchActivity$1.invokeSuspend(StartupManagerImpl.kt:517)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:34)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:610)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runDefaultDispatcherTask(CoroutineScheduler.kt:1194)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:906)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:775)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:762)
Caused by: java.lang.NoClassDefFoundError: io/ktor/server/cio/CIO
at com.anthropic.code.plugin.services.MCPService.start(MCPService.kt:57)
at com.anthropic.code.plugin.startup.PostStartupActivity.execute(PostStartupActivity.kt:14)
at com.intellij.ide.startup.impl.StartupManagerImplKt$launchActivity$1.invokeSuspend(StartupManagerImpl.kt:511)
... 7 more
Caused by: java.lang.ClassNotFoundException: io.ktor.server.cio.CIO PluginClassLoader(plugin=PluginMainDescriptor(name=Claude Code [Beta], id=com.anthropic.code.plugin, version=0.1.14-beta, isBundled=false, path=~\AppData\Roaming\JetBrains\IntelliJIdea2025.3\plugins\claude-code-jetbrains-plugin-0.1.14-beta.jar), packagePrefix=null, state=active, parents=...)
at com.intellij.ide.plugins.cl.PluginClassLoader.loadClass(PluginClassLoader.kt:149)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
... 10 more
`
(Full 'PluginClassLoader' parent chain trimmed for brevity; it lists the standard 2025.3 platform Terminal and IDEA CORE content module descriptors. Happy to provide the full untrimmed trace on request.)
Steps to Reproduce
- Install Claude Code [Beta] 0.1.14-beta from the JetBrains Marketplace into IntelliJ build 253.31033.145 (2025.3 line) on Windows.
- Restart the IDE
- Open any project (issue reproduces on every project, new or existing)
- Observe the Plugin Exception in the IDE Event Log / idea.log during post-startup activity. The Claude Code tool window does not initialize.
Claude Model
None
Is this a regression?
I don't know
Last Working Version
_No response_
Claude Code Version
Install Claude Code [Beta] 0.1.14-beta
Platform
Anthropic API
Operating System
Windows
Terminal/Shell
IntelliJ IDEA terminal
Additional Information
This issue is similar to the locked issue #15594
This issue has 2 comments on GitHub. Read the full discussion on GitHub ↗