EventDebugger

EventDebugger identifies the exact plugin listener that changes a Bukkit event. It snapshots the configured values before and after each listener and prints only real changes.

Quick start

1. Put the shaded jar in the server's plugins directory and restart the server.
2. Run /eventdebugger status to verify the configured event subscriptions.
3. Reproduce the problem and look for a concise change in the console:

PlayerInteractEvent changed by ExamplePlugin (HIGH, com.example.InteractListener)
  isCancelled: false -> true

Edit plugins/EventDebugger/config.yml to select event classes and zero-argument methods, then run /eventdebugger reload. You do not need to restart the server.

Run /eventdebugger gui in-game for the visual dashboard. Current Paper versions use the native dialog UI when available; Spigot and older Paper versions automatically receive the chest UI. The chest dashboard provides live event activity, detailed before/after history, plugin filters, subscription toggles, and a guided chat flow for adding new event classes and getters.

The modern UI includes clickable live traces, stable numbered outcomes, inline before/after diffs, native event-subscription forms, and a Capture Settings form for debugger state, history capacity, and listener discovery cadence. Dialog actions report their result inside the current screen.

Commands

Command	Purpose
/eventdebugger status	Show state, subscriptions, listener count, and counters
/eventdebugger gui	Open the best visual dashboard available on this server
/eventdebugger events	Show live activity for subscribed events
/eventdebugger history	Review recorded listener outcomes
/eventdebugger filters	Choose which installed plugins are inspected
/eventdebugger subscriptions	List configured exact subscriptions
/eventdebugger refresh	Immediately discover newly registered listeners
/eventdebugger reload	Reload configuration and safely re-instrument listeners
/eventdebugger on / off	Persistently enable or disable instrumentation

The aliases /edebug and /ed are also available. Commands require eventdebugger.admin, which defaults to server operators.

Performance controls

Exact subscriptions are the fastest option. listen-to-all-cancellable is deliberately disabled by default because it scans and observes many event types. Use include-plugins when you only need to investigate one or two plugins, and increase refresh-interval-ticks if plugins on your server never register listeners dynamically.

EventDebugger caches all reflected methods, skips already-instrumented listeners during refreshes, and creates only one value snapshot array per inspected listener call. Disabling it restores the original Bukkit executors immediately.

The production jar targets Java 8 bytecode and compiles only against Spigot API 1.16.1. It links no Paper API classes; the embedded dialog framework discovers modern capabilities reflectively and is optional. Kotlin, ReflectASM, Reflections, and SLF4J are shaded and relocated inside the EventDebugger namespace. User-configured events are resolved from the running server and installed plugin class loaders, so they can be newer than the API used to compile EventDebugger.