Direct answer
Stop the server and keep only one intended JAR for that plugin. Paper does not support two plugin files declaring the same plugin name at the same time.
Diagnosis to use: Two JAR files can declare the same plugin identity even when their filenames differ. The loader may reject both or select a version unexpectedly.
Why this happens
It is common after an update: the new JAR is uploaded but the old release remains in plugins/. Paper may report both filenames in an Ambiguous plugin name warning.
What to collect: List your plugins/ directory by file size and modification time; compare the conflicting plugin names in logs/latest.log. This often happens when an updater leaves the previous release beside the new one.
Choose the correct file before deleting
Compare the plugin’s official version/download page and your backup. Remove or archive the outdated copy outside the plugins folder, then restart. Do not delete both files unless you intend to uninstall the plugin.
Check generated plugin folders separately
The configuration/data folder is not the same as the plugin JAR. Updating a plugin normally means replacing the JAR while preserving its data folder unless the plugin’s migration instructions say otherwise.
Targeted repair: Stop the server, back up the directory and remove the redundant JAR from the active plugins folder. Leave the plugin’s data folder in place; deleting it is not required to resolve duplicate JARs.
Verify after the change: On a clean startup, confirm exactly one version loads and the existing configuration/data is still present.
After cleanup
Run /plugins and confirm one enabled copy is present, then scan startup logs for migration warnings or configuration changes introduced by the update.
Official references
These references were checked while preparing this fix. Version-specific behavior can change, so use the project documentation for your exact release when a detail differs.
Related fixes and guides
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