Entity lifecycle: where code belongs — documentation

EnterTree, Ready and ExitTree order; reentry, RequestReady and a complete C# fixture.

Choose a callback

Task	Place
Initial field values	Field initializer/constructor; do not assume an active tree
Subscribe on every entry	_EnterTree
Configure after children are ready	_Ready
Disconnect external handlers on exit	_ExitTree
Ordinary frame updates	_Process(double delta)
Physics-step logic	_PhysicsProcess(double delta)
Handle input not consumed earlier	_UnhandledInput / _UnhandledKeyInput
Draw a CanvasItem	_Draw; request a redraw with QueueRedraw

Names and casing matter. In C# use public override and the exact SDK signature. A constructor does not mean the object is already in a level. Do not use it to locate children that still need loading from a prefab. If your own C# base class implements the callback, explicitly decide whether to call base; an empty Entity base method is not a required ritual.

Verify the order

Add both files to a Reckfell 1.0.0 C# project. Attach LifecycleDemo to an Entity in a separate level, build and press F6. Output shows the journal and Ready calls: Parent=1, Child=2. Initial entry/readiness events are Parent:enter → Child:enter → Child:ready → Parent:ready.

LifecycleProbe.cs

C#
using System.Collections.Generic;
using Reckfell;

public partial class LifecycleProbe : Entity
{
    public List<string> Journal { get; set; } = new();
    public int Entries { get; private set; }
    public int ReadyCalls { get; private set; }
    public int Exits { get; private set; }

    private void Record(string stage) => Journal.Add(Name + ":" + stage);
    public override void _EnterTree() { Entries++; Record("enter"); }
    public override void _Ready() { ReadyCalls++; Record("ready"); }
    public override void _ExitTree() { Exits++; Record("exit"); }

    public override void _Notification(int what)
    {
        if (what == NotificationParented) Record("parented");
        if (what == NotificationUnparented) Record("unparented");
        if (what == NotificationPredelete) Record("predelete");
    }
}

LifecycleDemo.cs

C#
using System.Collections.Generic;
using Reckfell;

public partial class LifecycleDemo : Entity
{
    public List<string> Journal { get; } = new();
    public LifecycleProbe ParentProbe { get; private set; } = null!;
    public LifecycleProbe ChildProbe { get; private set; } = null!;

    public override void _Ready()
    {
        ParentProbe = new LifecycleProbe { Name = "Parent", Journal = Journal };
        ChildProbe = new LifecycleProbe { Name = "Child", Journal = Journal };
        ParentProbe.AddChild(ChildProbe);
        AddChild(ParentProbe);
        RemoveChild(ParentProbe);
        AddChild(ParentProbe);
        RemoveChild(ParentProbe);
        ChildProbe.RequestReady();
        AddChild(ParentProbe);
        ReckfellApi.Print(string.Join(" → ", Journal));
        ReckfellApi.Print("Ready calls: Parent=" + ParentProbe.ReadyCalls + ", Child=" + ChildProbe.ReadyCalls);
    }
}

Exit calls Child:_ExitTree before Parent:_ExitTree. RemoveChild does not delete an object; a later AddChild calls _EnterTree again without automatically repeating ordinary _Ready. RequestReady affects the requesting Entity next entry: it neither calls _Ready immediately nor recursively applies to children.

Subscriptions and dependencies

If a new child emits a signal in _Ready, connect before AddChild. For an external long-lived source, the _EnterTree/_ExitTree pair supports reattachment without duplicate handlers. Subscribing only in _Ready and disconnecting in _ExitTree is insufficient for reentry.

_Ready guarantees readiness of ordinary existing children, not future dynamic objects or arbitrary external services. Inject dependencies before activation or define a separate initialization phase. Pause does not cancel a direct method call or an emitted signal: see pause rules.

The fixture verifies actual callbacks, three entries, two exits, RequestReady and native release. This journal does not establish keyboard routing or every Resource lifetime behavior.