Lifecycle callbacks

Callbacks are entry points invoked by Rustic. Define only those a behavior needs.

When each callback runs

Callback	When to use it	Variables
`OnCreate`	One-time construction before startup.	None
`Start`	Resolve references and initialize gameplay state.	None
`OnEnable`	Resume state when the owner becomes enabled.	None
`FixedUpdate`	Physics and deterministic simulation.	`dt`: required fixed-step seconds
`Update`	Input, presentation, timers, and per-frame logic.	`dt`: required frame seconds
`OnDisable`	Pause state when the owner becomes disabled.	None
`OnDestroy`	Release instance resources before destruction.	None
`OnStop`	Final play-session cleanup.	None

Lua 5.4

lua

return { Start=function() end, Update=function(dt) end, FixedUpdate=function(dt) end, OnDestroy=function() end }

JavaScript and HTML / inline JS

javascript

globalThis.behavior={Start(){},Update(dt){},FixedUpdate(dt){},OnDestroy(){}};

External languages

Rustic invokes callbacks through each language SDK. Python calls run(globals()); PHP calls rustic_run(callbacks); C and C++ register RusticBehavior slots; C# calls Run and Java calls run with a callback dispatcher; Luau returns a behavior table. External callback names are on_create, on_start, on_enable, fixed_update, update, on_disable, on_destroy, and on_stop. Omitted callbacks are handled automatically by the SDK; frame callbacks receive dt in seconds. Physics runs after FixedUpdate callbacks, including during Frame Advance. Gravity and solid box response work for built-in primitives, but the simulator does not dispatch collision or touch callbacks to any language.