runtime.esm_missing_extension

ES module import without a file extension: <module>

A mevcore app hosting error at the “start / health check” stage.

What it means

In ES modules Node.js needs the full file name in relative imports, and <module> has no extension or is a folder.

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

Write imports with .js (in TypeScript too, with "moduleResolution": "NodeNext") and /index.js for folders, or bundle the code with tsup/esbuild.

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 After the fix, deploy again. If it fails again, the log ends with [mevcore] lines naming the new error code.
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.esm_missing_extension
phase: start / health check
diagnosis: ES module import without a file extension: <module>
platform hint: In ES modules Node.js needs the full file name in relative imports, and <module> has no extension or is a folder. Write imports with .js (in TypeScript too, with "moduleResolution": "NodeNext") and /index.js for folders, or bundle the code with tsup/esbuild.
platform docs: https://mevcore.com/llms-full.txt

Can't fix it?

Message support with the error code: we will tell you what to change in the project or settings.

App hosting