Direct answer

Use a plugin release whose developer explicitly supports Folia, or use a Folia-compatible alternative. Do not manually add `folia-supported: true` to a plugin file as a “fix”: PaperMC explicitly warns that the flag alone is not enough; the plugin must be developed for Folia’s region/thread model.

What it means

Folia will not load a plugin as Folia-compatible unless it declares support, and declaring the flag alone does not make normal Paper code thread-safe.

If you are a player

  • Record the exact command/message or feature that failed and the time it happened.
  • If the problem affects only your account, note your permissions/group and whether another player can use the same feature.
  • Send the owner the exact wording rather than repeatedly retrying; plugin startup/configuration errors must usually be fixed server-side.

If you run the server

  1. Check the plugin’s official page/changelog for Folia support.
  2. If the plugin is required but has no Folia build, run a supported Paper-family server instead of forcing it to load.
  3. For developers, use Folia-aware schedulers/APIs and test on an actual Folia server.

References

Use the documentation for the exact software and release you run. These sources support the settings or diagnostic behavior used in this fix.

Focused diagnostic check: Look for the plugin loader rejection and the plugin author's Folia support statement. A plugin that works on Paper is not automatically safe on Folia because entity and region state must be accessed from the owning scheduler; editing folia-supported in the JAR descriptor does not make the code thread-safe.

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