UI Freeze when starting REPL on WSL (blocking socketConnect on AWT thread)

[sjovellar]

Hello,

I'm experiencing a complete and permanent UI freeze when trying to start a Cursive nREPL.

Environment:

• IntelliJ IDEA: 2025.2.3 (Ultimate Edition), Build #IU-252.26830.84
• Cursive: Latest version as of October 2025
• Operating System: Windows 11 with WSL2 (running Ubuntu 22.04)
• Setup Details: I am running the Linux version of IntelliJ IDEA directly inside the WSL2 environment

Steps to Reproduce:

1. Start the Linux version of IntelliJ IDEA inside WSL.
2. Open any Clojure project.
3. Try to launch a local Cursive nREPL.

Actual Result:
The entire IDE UI freezes instantly and permanently. The application becomes completely unresponsive and must be terminated using kill -9 from the WSL terminal.

Diagnosis:
I was able to capture thread dumps during the freeze. The analysis shows that the AWT Event Dispatch Thread (the main UI thread) is blocked by a network call, which is causing the freeze.

The thread is stuck trying to connect a socket inside Cursive's nREPL client code. This indicates that a blocking I/O operation is being performed on the main UI thread.

Here is the stack trace for the frozen AWT thread from the main IDE process:

"AWT-EventQueue-0" prio=6 tid=0x25 nid=0x26 runnable
  java.lang.Thread.State: RUNNABLE
      at java.net.PlainSocketImpl.socketConnect(Native Method)
      at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:412)
      - locked <0x23f2> (a java.net.SocksSocketImpl)
      at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:250)
      at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:232)
      at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:403)
      at java.net.Socket.connect(Socket.java:609)
      at cursive.repl.nrepl.NreplClient.connect(NreplClient.kt:98)
      at cursive.repl.nrepl.NreplClient.<init>(NreplClient.kt:80)
      at cursive.repl.nrepl.NreplConnection.createClient(NreplConnection.clj:37)

I have attached the full thread dumps for all related processes for complete context.

Thank you for looking into this.

clojure_main_dump.txt
idea_dump_2.txt
idea_dump_1.txt