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When the Server Console Shows an Error
Your plugin built fine and broke on your own server. How to read the error, and what the four common ones mean.
This is a different problem from a failed build
A failed build happens on VyroAI: the code did not compile and you never got a jar. That is Why Did It Fail? and Auto-Fix.
This page is the other one: the build went green, you have a jar, and the crash happened on your server when it tried to run it. The code is fine as code — something about the server it landed on does not match what it was built for. Almost every case is one of four things, and the error tells you which.
Read the LAST "Caused by:"
A Java error in a server console is long, and most of it is scenery. The part that names your problem is the last Caused by: line in the block — read from the bottom up, not the top down. The first line is usually only "could not pass event", which is true of every error there has ever been.
Copy the whole block, from the first line to the last. The class name on that final line is what the table below is indexed on.
The four you will actually meet
| What the console says | What it means | What fixes it |
|---|---|---|
| **NoSuchMethodError** or **NoClassDefFoundError**, while playing | The plugin was compiled against a different Minecraft version than the server runs. The method it wants existed on one and not the other | Ask the AI in a message to build for your server's exact version — *"make it for Paper 1.21.11"* — then build again. Changing **Project Settings → Build → Minecraft version** and rebuilding is not enough: the build does not apply that setting, it only warns in the build log that the jar was built for the version in the build file |
| **Unsupported API version**, at startup | The plugin was built for a **newer** Minecraft than the server. The server refuses it before it starts | Same fix — ask the AI in a message for the version the server actually runs, then build again |
| **UnsupportedClassVersionError** | The server's **Java** is too old for the plugin, which is a separate thing from the Minecraft version | Update Java on the server. Minecraft **1.20.5 and newer** needs Java **21** (Minecraft 26 needs **25**), and the build raises **Project Settings → Build → Java version** to that whatever you pick. Only for 1.20.4 and older can you lower that setting and rebuild instead |
| **Unknown dependency** or **Could not load**, naming another plugin | Your plugin needs a second plugin — Vault, PlaceholderAPI or whichever the message names — and that plugin is **not installed on the server** | Install the named plugin into `/plugins` alongside yours and restart |
"Unknown dependency" is not a VyroAI dependency problem
This is the one that reliably sends people to the wrong page. A build dependency — the ones on the Dependency Catalog — is a library the compiler needs, and Cloud Build already handles it, or your build would not have succeeded.
Unknown dependency at startup is the server saying it cannot find a plugin. It is a file missing from your /plugins folder, not a setting in your project. Download the named plugin from wherever it normally comes from, drop it in beside yours, and restart.
Paste the exact error — guessing costs credits
When you bring one of these to the AI, paste the error text itself. "It doesn't work" gives the AI nothing to work from, so it guesses; each guess is a real run that bills real credits, and it usually takes several before one lands.
The same error pasted in full is normally one short attempt. Two habits go with it: one problem per message, and on a failed build use the build panel's Auto-Fix rather than describing the failure again in chat — Auto-Fix already has the log.
Do not patch around a version mismatch
A version or Java mismatch is decided when the plugin is compiled. It cannot be undone by editing the jar, adding a config option, or asking for a workaround in config.yml — anything that appears to help is hiding the problem rather than fixing it.
Ask the AI in a message for your server's version — "make it for Paper 1.21.11" — so it changes the build file, then build again and upload the new jar. Changing the version in Project Settings → Build and rebuilding gives you the same jar: the build does not apply that setting, it only adds a warning to the build log.
"Missing pom.xml" and "Invalid pom.xml structure" are build errors
These two never come from your server. They appear in the build panel on VyroAI when a build fails, so there is no jar yet:
- "Missing pom.xml — the project has no Maven build file." The project has no build file at all, usually because the AI has not written the whole project yet. Ask it to "generate the complete project structure", then build again.
- "Invalid pom.xml structure — the build file has malformed XML tags."
pom.xmlis there but broken: a tag like<n>where<name>belongs, or a tag that is never closed. Press Auto-Fix on the failed build, or correct the tag inpom.xmlby hand.
You only see these two when the build log names no more exact error.
Keep the console open while the server starts, not just while you play. Startup errors scroll past quickly, and the line that explains a plugin's odd behaviour an hour later was usually printed in the first ten seconds.
Try it now: Describe your plugin and see the plan, free and with no account. Open the plugin generator
Where to next
- Next in Minecraft Studio: Plugin Icons
- Set it up first: Installing It on a Server — The install steps this page assumes you followed.
- If no jar appeared: Why Did It Fail? — The other kind of failure: when VyroAI itself did not finish.
- If the versions clash: Project Settings — The Build tab where the Java and Minecraft versions live.
- Rather not read logs: Auto-Fix — Letting the AI read a failed build log for you.
18 of 22 in Minecraft Studio · Last checked 12 September 2026 · Previous: Moving to a New Version