getcallbackvalue

Callback properties like BindableFunction.OnInvoke and RemoteFunction.OnClientInvoke are write-only in standard Luau — you can assign them but cannot read them back. The executor reads the internal property descriptorProperty descriptorMetadata defining a Roblox Instance property: its type, default value, replication behavior, and access flags (read-only, hidden/non-scriptable, deprecated). Stored in the reflection system. directly from the InstanceInstanceThe base class for all Roblox objects (Parts, Models, Scripts, GUIs, etc.). Instances form a tree hierarchy (the DataModel). In Luau, they appear as userdata with shared metatables.'s C++ memory layout, bypassing the write-only restriction.

Useful for discovering what function a game has registered as a callback handler, allowing you to inspect, clone, or replace it. Common pattern: read the callback, wrap it, and re-assign a modified version.