Migrate Godot Projects to Version 4

This skill provides a guide for developers transitioning from Godot 3.x to Godot 4. It covers major syntax changes in GDScript 2.0, including the new annotation system, the replacement of the Tween node with create_tween(), and updated property syntax for setters and getters.

Use this skill when porting a Godot 3 project to Godot 4, when encountering syntax errors after upgrading, when replacing deprecated nodes like the Tween node, or when updating export variables to @export annotations.

Do not use this skill for tasks outside the migration scope described above. Do not treat the output as a substitute for environment-specific validation, testing, or expert review. Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.

You provide questions or code snippets related to Godot 3.x to Godot 4 migration. You receive syntax updates and code examples showing before-and-after patterns.

Annotations now use the @ prefix. In Godot 3, you wrote export var x, but in Godot 4 you write @export var x. Similarly, onready var y becomes @onready var y, and tool becomes @tool at the top of your file.

Setters and getters are now defined inline:

var health: int:
    set(value):
        health = value
        emit_signal("health_changed", health)
    get:
        return health

The Tween node is deprecated. Instead of $Tween.interpolate_property(...) and $Tween.start(), use:

var tween = create_tween()
tween.tween_property($Sprite, "position", Vector2(100, 100), 1.0)
tween.parallel().tween_property($Sprite, "modulate:a", 0.0, 1.0)

Signal connections now use callables instead of strings. Replace connect("pressed", self, "_on_pressed") with pressed.connect(_on_pressed).

Coroutines use await instead of yield:

await get_tree().create_timer(1.0).timeout

GDScript 2.0 supports typed arrays:

# Godot 3
var enemies = []

# Godot 4
var enemies: Array[Node] = []

func _ready():
    for child in get_children():
        if child is Enemy:
            enemies.append(child)

Type all variables (var x: int) for performance gains in GDScript 2.0. Use @export_range, @export_file, and similar annotations for better inspector UI. Use super() to call parent methods instead of .function_name(). Prefer signal objects (name.emit()) over string-based emission (emit_signal("name")).

If you encounter "Identifier 'Tween' is not a valid type," note that Tween is now SceneTreeTween or just an object returned by create_tween(). You rarely type it explicitly, just use var tween = create_tween().

This skill is for developers transitioning from Godot 3.x to Godot 4.