Godot Nodes & Scenes (4.x)

Compose games from nodes and scenes, instance them at runtime, and access the tree without crashing on freed or missing nodes. Targets Godot 4.7.

When to use

• Use when structuring .tscn scenes, choosing how to break a feature into nodes, instancing a PackedScene (bullets, enemies, UI), or setting up autoload singletons.
• Use when debugging get_node() / $Path returning null, or "Attempt to call on a previously freed instance".

When not to use: GDScript language/syntax → godot-gdscript; signal-based decoupling → godot-signals-groups; physics bodies/collisions → godot-physics.

Core workflow

1. Model with composition. A scene is a tree of nodes saved as .tscn. Build small, single-purpose scenes (Player, Bullet, Enemy) and compose larger scenes from them. Favor adding child nodes over deep inheritance.
2. Make a scene reusable by giving its root a script and exposing @export config. Save it; it becomes a PackedScene you can instance many times.
3. Instance at runtime with preload/load → scene.instantiate() → add_child(instance). Set position/state after adding (or before, both work).
4. Access nodes safely. Use @onready var x = $Path for fixed children; use unique names (%Name) for nodes deep in the tree; never assume a node still exists.
5. Use autoloads for global state/services (game state, audio, scene switching) — registered in Project Settings > Globals (Autoload), accessible by name everywhere.
6. Free nodes with queue_free() and guard later access with is_instance_valid().
7. Check references before you finish. After creating, moving or renaming scenes, resources or scripts, run python scripts/check_godot_project.py <project-dir> (no Godot install needed; --json for machine-readable output). Fix every ERROR (missing or wrong-case res:// paths, undeclared ExtResource/SubResource ids, bad parent= paths, missing main scene or autoload) and re-run until it exits 0. Warnings such as a stale path= that Godot still finds by uid are safe but worth fixing. Run the script path relative to this skill directory, or resolve the installed skill path first. It needs Python 3.10+ and nothing else, and it does not replace opening the project in Godot.

Patterns

1. Instance a scene at runtime

extends Node2D

const BULLET := preload("res://bullet.tscn")   # preload: loaded at compile time

func shoot(at: Vector2, dir: Vector2) -> void:
    var bullet := BULLET.instantiate()         # create an instance of the scene
    bullet.global_position = at
    bullet.direction = dir                      # set exported/public state
    add_child(bullet)                           # now it's in the tree and runs

2. Safe node access: $, get_node_or_null, and unique names

@onready var label: Label = $UI/Label            # $ is sugar for get_node("UI/Label")
@onready var health_bar: ProgressBar = %HealthBar # % = scene-unique name (rename-proof)

func update() -> void:
    var optional := get_node_or_null("Maybe/Missing")  # returns null instead of erroring
    if optional:
        optional.queue_free()

3. An autoload singleton (global game state)

# game_state.gd — add in Project Settings > Globals > Autoload as "GameState".
extends Node

var score := 0
signal score_changed(value: int)

func add_score(points: int) -> void:
    score += points
    score_changed.emit(score)         # any scene can: GameState.score_changed.connect(...)

4. Change the running scene

func go_to_level_2() -> void:
    # Swaps the current scene for another. Frees the old scene tree.
    get_tree().change_scene_to_file("res://levels/level_2.tscn")
    # Or, with a preloaded PackedScene:
    # get_tree().change_scene_to_packed(LEVEL_2)

Pitfalls

• $Path / get_node() return null or error when the path is wrong or the node isn't in the tree yet. Use @onready, verify the path matches the scene, or use get_node_or_null() for optional nodes.
• Renaming a node breaks $Path. Use unique names (%Name, set via right-click

  Access as Unique Name) so deep references survive renames and reparenting.

• free() mid-frame can crash other code still using the node. Prefer queue_free() (deletes at end of frame) and check is_instance_valid(node).
• Setting child state before add_child() is fine, but _ready() on the child only runs after it enters the tree — don't expect its @onready vars before that.
• Autoload order matters: autoloads are added before the main scene, in list order. An autoload can't depend on the main scene existing yet.
• instance() was renamed to instantiate() in Godot 4. preload runs at parse time (path must be constant); load runs at runtime (path can be a variable).
• change_scene_to_file() is deferred, not immediate — Godot swaps and frees the old scene at the end of the current frame. Any code after the call still runs against the old tree, and get_tree().current_scene isn't the new scene until next frame. Don't read the new scene's nodes on the same line; do it from the new scene's _ready().

References

• For scene inheritance, owner/ownership when saving scenes from code, groups vs unique names, and node-path edge cases, read references/tree-and-instancing.md.
• scripts/check_godot_project.py — read-only reference checker for a Godot 4.x project; --help lists every check and the exit codes.

Related skills

• godot-gdscript — language, lifecycle, and @onready.