Alpha 1.2.6 installation is finished with errors

[nz134855-ship-it]

Describe the bug
Upon launching installation process of a1.2.6, RetroMCP finishes installing with error.

Expected behavior
I expected RetroMCP to finish installing a1.2.6 successfully with no errors.

Screenshots

RetroMCP Version
v1.2

Minecraft version
a1.2.6

[bouclem]

Are you sure this is a bug? The stack trace shows javax.net.ssl.SSLException: Connection reset during a library/asset download - that's a network-side failure (TLS connection reset by peer), not something RetroMCP is doing wrong.

A few things that commonly cause this:

• Unstable connection or VPN
• Antivirus or firewall doing TLS interception
• ISP-level filtering
• Temporary GitHub/Mojang CDN hiccup

Things you can try:

• Retry the setup (transient resets usually clear up)
• Disable VPN/proxy if you have one
• Temporarily disable HTTPS scanning in antivirus
• Try on a different network

If it keeps happening on every retry across different networks, then it's worth investigating further. Can you confirm whether retrying works?

[nz134855-ship-it]

Well, I've no VPNs or Proxys and I think I have stable internet connection.

[bouclem]

Can you retry downloading? And then give an screenshot of log.

[nz134855-ship-it]

Yes, I can. I've just launched downloading and it stopped at 5%. It's stopped moving at all.

[bouclem]

okay, i'll search why, and also try to fix

[nz134855-ship-it]

Oh, downloading proccess is stopped. With this error:

[bouclem]

im doing an fix, you'll need to wait if my PR is accepted and if there new version

[nz134855-ship-it]

Hey! I think I somehow managed to download and decompile it, but now I can't build it 'cause it finishes with error:

C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\bin\java.exe "-javaagent:C:\Program Files\JetBrains\IntelliJIdea2025.3\lib\idea_rt.jar=54726" -Dfile.encoding=UTF-8 -classpath C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\charsets.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\access-bridge-64.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\cldrdata.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\dnsns.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\jaccess.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\localedata.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\nashorn.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\sunec.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\sunjce_provider.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\sunmscapi.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\sunpkcs11.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\ext\zipfs.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\jce.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\jfr.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\jsse.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\management-agent.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\resources.jar;C:\Users\Zavgar486\.jdks\temurin-1.8.0_482\jre\lib\rt.jar org.mcphackers.launchwrapper.Launch --username Player --uuid - --session - --version a1.2.6 --gameDir . --assetsDir .\assets --assetIndex a1.2 --accessToken - --userProperties "{}" --userType legacy --versionType release --skinProxy pre-b1.9-pre4
Error: Could not find or load main class org.mcphackers.launchwrapper.Launch

Process finished with exit code 1

[PhoenixVX]

Libraries did not download correctly or you did not import the project correctly. Does it run correctly when using the "Start client" task in RetroMCP itself? If it works in RetroMCP and not in IntelliJ, then you imported the project incorrectly.

[nz134855-ship-it]

Oh, I see, when I was trying to decompile, it "Finished with error"

Error on line 15 in .\minecraft_server\src\net\minecraft\src\NetworkMasterThread.java
cannot find symbol
  symbol:   method stop()
  location: class java.lang.Thread

Error on line 22 in .\minecraft_server\src\net\minecraft\src\NetworkMasterThread.java
cannot find symbol
  symbol:   method stop()
  location: class java.lang.Thread

Also, it successfully launches in RetroMCP, but gives me an error in IntelliJ IDEA.
And of top of it all, there's no Start Client button in IntelliJ.

[nz134855-ship-it]

@PhoenixVX I think, I found a reason of this issue. RetroMCP, for some reason uses JDK 26 as default, after I've uninstalled it, only JDK 8 left and program just gives me an error "Install Java Development Kit to install and test" and also gives very same error upon starting decompilation process. What's wrong with it? Sorry for pinging you, though.

[PhoenixVX]

Windows?

If you are on Windows and are using double click to launch RetroMCP, Windows will use the JVM which is stored in the JavaSoft registry keys instead of what is in JAVA_HOME or PATH. It is possible that you have an old JRE in the JavaSoft registry variable. I usually recommend re-running the JDK 8 installer and making sure to enable the registry keys option or using JARFix to explicitly set the JVM that is used.

If this isn't the case, then you must have a JRE installed instead of a JDK. RetroMCP queries the JVM to see if it has the Java Compiling API which is available in all JDKs. Additionally, the JAVA_HOME option in RetroMCP was edited to work in the past few RetroMCP versions so you may also use that.