The code needs a newer Java

What it means

The classes were compiled for a newer Java than the server runs (class file version <version>).

The build passed, but the app did not start or did not answer the health check.

Typical causes

• The app does not listen on 0.0.0.0 and the port from the PORT variable
• An environment variable is missing, or the database or Redis is not connected
• The start command is wrong or the process exits right away

How to fix it on mevcore

Pick a runtime with a newer Java in the settings.

1. 1 Open the app in the mevcore panel: the Problems card on the overview shows this error and the log line it was found in.
2. It is fixed on the “Settings” tab of the app.
3. 2 After the fix, deploy again. If it fails again, the log ends with [mevcore] lines naming the new error code.
4. 3 The "Ask AI" button next to the error prepares a request for ChatGPT or Claude: the error code, the end of the log without secrets and the app settings.

For an AI assistant

The same in English: paste it together with the log into the AI chat.

mevcore error code: runtime.java_version
phase: start / health check
diagnosis: The code needs a newer Java
platform hint: The classes were compiled for a newer Java than the server runs (class file version <version>). Pick a runtime with a newer Java in the settings.
platform docs: https://mevcore.com/llms-full.txt

Related errors

• install.java_version Wrong Java version (<required> needed)
• runtime.java_no_main_manifest The jar has no main class
• runtime.java_main_class Java cannot find the main class <class>
• install.python_version Wrong Python version (<required> needed)