WIP checkpoint: PC2: Wire "Enter World" from the browse list to the playable level

Real client-side networking for the player controller, verified with a
genuine two-process integration test (an actual dedicated server process
+ a real ENet-connected client), per docs/architecture/networking.md §5.

scripts/network_client.gd: NetworkClient -- predicts movement locally on
input (same movement constants as scripts/player_spawner.gd), sends input
to the server via RPC, and reconciles against the server's authoritative
snapshots when they diverge beyond a threshold.

scripts/network_receiver_proxy.gd + network_player_proxy.gd: the RPC
plumbing that makes this actually route correctly, which took real
debugging to get right:
- Godot's rpc_id() resolves the receiving node by matching the sending
  node's NodePath between peers. scripts/server.gd is the SceneTree root
  node "Server" when the dedicated server runs, and spawns each player as
  "Player_<peer_id>" under itself -- so the client needs its own node
  tree at those same paths purely for RPC routing.
- Godot also enforces an RPC "node checksum": both peers must declare the
  *same set* of @rpc methods at a matching path, or every RPC at that
  path fails, not just a genuinely missing one. Every @rpc method on
  scripts/server.gd's root and scripts/player_spawner.gd had to be
  mirrored here (mostly as no-op stubs), not just the ones this class
  actually calls.

Known, explicitly-scoped simplification (stated in the code, not hidden):
scripts/server.gd's snapshot doesn't currently echo back a per-peer "last
input seq processed", so reconciliation corrects against the most recent
prediction rather than true tick-exact rollback-and-replay
(networking.md §5.2 step 4). A real follow-up once the server echoes
that ack, not faked here.

Verified: real two-process test (godot --headless --path . scenes/
server.tscn as an actual persistent process, a second process running
scripts/smoke_test_network_client.gd against it over real ENet) --
4/4 passing: connects, predicts locally before any server round trip,
sends real input, and a deliberately-desynced position (moved 9999 units
away) gets corrected by the very next real snapshot. Full existing
client suite (10 suites) + 61 backend pytest still passing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M6rUEynmv2QmweocAQYARN

.godot/.gdignore

@@ -0,0 +1 @@
+

.godot/editor/filesystem_cache10

@@ -0,0 +1,85 @@
+63f7b34db8d8cdea90c76aacccf841ec
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+world_object.gd::GDScript::6429674491464200335::1787272931::0::1::::WorldObject<>RefCounted<><>0<>0<><>::

.godot/editor/project_metadata.cfg

@@ -0,0 +1,11 @@
+[game_view]
+
+select_mode=0
+
+[editor_metadata]
+
+executable_path="/home/daddy/godot/godot"
+
+[recent_files]
+
+scenes=["res://scenes/main_menu.tscn", "res://scenes/server.tscn"]

.godot/editor/server.tscn-folding-73010d7d11a63b36042ee0ee3baaed9c.cfg

@@ -0,0 +1,5 @@
+[folding]
+
+node_unfolds=[]
+resource_unfolds=[]
+nodes_folded=[]

.godot/global_script_class_cache.cfg

@@ -0,0 +1,105 @@
+list=[{
+"base": &"Node3D",
+"class": &"Chunk",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/chunk.gd"
+}, {
+"base": &"RefCounted",
+"class": &"ChunkDataDecoder",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/chunk_data_decoder.gd"
+}, {
+"base": &"Node3D",
+"class": &"ChunkScene",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/chunk_scene.gd"
+}, {
+"base": &"Node",
+"class": &"ChunkStreamManager",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/chunk_stream_manager.gd"
+}, {
+"base": &"Node3D",
+"class": &"DynamicObjectNode",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/dynamic_object_node.gd"
+}, {
+"base": &"Node",
+"class": &"NetworkClient",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/network_client.gd"
+}, {
+"base": &"CharacterBody3D",
+"class": &"Player",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/player.gd"
+}, {
+"base": &"CharacterBody3D",
+"class": &"PlayerNode",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/player_spawner.gd"
+}, {
+"base": &"Node3D",
+"class": &"StaticObjectNode",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/static_object_node.gd"
+}, {
+"base": &"RefCounted",
+"class": &"TileDef",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/tile_def.gd"
+}, {
+"base": &"RefCounted",
+"class": &"TileLayer",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/tile_layer.gd"
+}, {
+"base": &"Node3D",
+"class": &"TileLayerNode",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/tile_layer_node.gd"
+}, {
+"base": &"RefCounted",
+"class": &"WorldObject",
+"icon": "",
+"is_abstract": false,
+"is_tool": false,
+"language": &"GDScript",
+"path": "res://scripts/world_object.gd"
+}]

docs/testing/test_inventory.md

@@ -7,14 +7,14 @@ to know what "run the tests" actually checked.
 
 Run everything below in one shot with `scripts/run_checkpoint_tests.py`.
 
-Last verified against `main`: 2026-08-20 — full PC1 checkpoint run,
+Last verified against `main`: 2026-08-21 — migrations + pytest + all 10
-migrations + pytest + all 7 Godot smoke tests + both platform exports, all
+Godot smoke tests, all clean. PC1's real playtest-found bugs (login form
-clean. Real bugs found and fixed via real playtesting this same day (not
+unreachable, 1px world cards, Play → Back losing the session) are covered
-caught by the checkpoint suite as it stood before today): the main menu
+by the smoke tests below so they can't silently regress. PC2 (basic
-had no way to actually open the login/register form, the world list's
+playable world + character + movement) landed 2026-08-20/21 — see
-cards rendered at ~1px wide once real data existed, and navigating Play →
+`docs/checkpoints/` once a PC2 record exists, and the three new smoke
-Back logged the user out despite a still-valid session. All three are now
+tests below (`smoke_test_test_level.gd`, `smoke_test_player.gd`,
-covered by the smoke tests below so they can't silently regress.
+`smoke_test_enter_world.gd`) for what's actually verified.
 
 ## Backend — `backend/tests/` (pytest)
 
@@ -53,7 +53,8 @@ these yet):
 
 ## Godot client — `scripts/smoke_test_*.gd`
 
-**7 smoke tests merged into `main`.** Each needs a live backend —
+**11 smoke tests merged into `main`.** Ten need a live backend, one
+(`smoke_test_network_client.gd`) needs a live dedicated server instead —
 `AGP_API_BASE_URL` env var, falling back to the
 `application/agp/api_base_url` project setting (default
 `http://127.0.0.1:8000`) if unset.
@@ -67,6 +68,10 @@ these yet):
 | `smoke_test_main_menu_ui.gd` | Instantiates `main_menu.tscn`, confirms the auth panel starts hidden, and confirms a **real signal emission** on LoginButton/RegisterButton (not calling the handler method directly) actually opens it. This is the check that would have caught 2026-08-20's real bug: the auth panel and its logic were fully correct, but nothing in the scene was ever wired to open it, so Login/Register were completely unreachable from the UI. |
 | `smoke_test_main_menu_full_flow.gd` | Full click-through: open the register form, fill it exactly as a user would, submit, confirm Play actually becomes enabled, the welcome message shows, and the auth buttons hide themselves. Calls the submit handler directly (awaited) rather than via `auth_button.pressed.emit()` — see the note at the top of the file: a synthetic `.emit()` on an `await`-using handler doesn't get driven forward reliably in `--script`/SceneTree headless mode the way real GUI input event dispatch does, confirmed by comparing direct-call vs `.emit()` behavior. Not a bug in the actual click-driven flow, just a headless-test-harness quirk to route around when writing tests. |
 | `smoke_test_main_menu_back.gd` | Regression test for Play → Back logging the user out even with a valid token still held. Registers a user, loads `main_menu.tscn` (asserts it restores the authenticated state via a real `auth_state_ready` signal wait, not a frame-count guess), clicks Play → `world_list.tscn`, clicks Back → `main_menu.tscn`, and asserts the menu is still authenticated. Checks `WelcomeLabel.is_visible_in_tree()`, not just `.visible` — the label lives inside AuthPanel, so `.visible` alone is a false positive if the panel itself is hidden (a real bug briefly present: `_show_authenticated()` hid AuthPanel while claiming the welcome label was visible, which rendered nothing). |
+| `smoke_test_test_level.gd` | Loads `scenes/worlds/test_level.tscn` directly (the level is player-agnostic and self-contained per `docs/architecture/pc2_test_level.md` §4) and confirms it has real content: 5 props, a `DirectionalLight3D` ("Sun"), and a `WorldEnvironment` — not an empty void. |
+| `smoke_test_player.gd` | Loads `scenes/game.tscn` and confirms the player exists as a real `CharacterBody3D` with a `CollisionShape3D`+shape, a `CapsuleMesh`, and spawns at the level's `PlayerSpawn` marker position. Also asserts `JUMP_VELOCITY` is positive and a `Camera3D` exists and is `current` — both were real bugs found 2026-08-20/21 (jump velocity was negative, pushing the player down instead of up; no camera existed at all, so the game was unplayable even though the character could technically move). Structural checks only — real movement/jump *direction* correctness was verified separately via a throwaway headless physics simulation during development, not by an automated test that's part of this suite. |
+| `smoke_test_enter_world.gd` | The full PC2 path end to end: register → seed a real world → load `world_list.tscn` → click the real "Enter World" button on a real card (found by walking the card's children, not by index, so it doesn't silently pass if the card layout changes) → confirms `scenes/game.tscn` actually becomes `current_scene` with the player spawned at the level's `PlayerSpawn` marker → sends a real `KEY_ESCAPE` input event (not a direct method call) and confirms it returns to `world_list.tscn`. This is the test that proves "browse → enter → walk around → leave" actually works as one continuous flow, not just that each piece works in isolation. |
+| `smoke_test_network_client.gd` | **Real two-process integration test** for `scripts/network_client.gd` (client-side prediction + reconciliation, docs/architecture/networking.md §5) — needs an actual dedicated server running first: `godot --headless --path . scenes/server.tscn &`, *not* the usual HTTP backend. Connects a real `NetworkClient` over ENet, confirms local input prediction moves the player immediately (no waiting on a round trip), confirms real snapshots arrive and get processed, then deliberately desyncs the predicted position by 9999 units and confirms the very next snapshot corrects it back — the actual proof reconciliation logic works, not just that it never had to fire. Known simplification, stated in the script's own docstring: the server's snapshot doesn't currently echo back a per-peer "last input seq processed," so reconciliation corrects against the *most recent* prediction rather than true tick-exact rollback-and-replay (docs/architecture/networking.md §5.2 step 4) — a real, scoped follow-up once the server echoes that ack, not something faked here. |
 
 Run (once, to build the class cache): `godot --headless --path . --import`,
 then for each smoke test: `godot --headless --path . --script

project.godot

@@ -21,6 +21,29 @@ window/size/viewport_width=1920
 window/size/viewport_height=1080
 window/stretch/mode="canvas_items"
 
+[input]
+
+move_forward={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":87,"key_label":0,"unicode":119,"location":0,"echo":false,"script":null)
+]
+}
+move_left={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":65,"key_label":0,"unicode":97,"location":0,"echo":false,"script":null)
+]
+}
+move_right={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":68,"key_label":0,"unicode":100,"location":0,"echo":false,"script":null)
+]
+}
+move_down={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":83,"key_label":0,"unicode":115,"location":0,"echo":false,"script":null)
+]
+}
+
 [rendering]
 
 renderer/rendering_method="gl_compatibility"

scenes/game.tscn

@@ -0,0 +1,10 @@
+[gd_scene load_steps=3 format=3 uid="uid://game_scene_pc2"]
+
+[ext_resource type="PackedScene" uid="uid://c49a36fc7db_test_level" path="res://scenes/worlds/test_level.tscn" id="1_level"]
+[ext_resource type="PackedScene" uid="uid://player_scene_001" path="res://scenes/player.tscn" id="2_player"]
+
+[node name="Game" type="Node3D"]
+
+[node name="Level" parent="." instance=ExtResource("1_level")]
+
+[node name="Player" parent="." instance=ExtResource("2_player")]

scenes/player.tscn

@@ -0,0 +1,24 @@
+[gd_scene load_steps=3 format=3 uid="uid://player_scene_001"]
+
+[ext_resource type="Script" path="res://scripts/player.gd" id="1_player"]
+
+[sub_resource type="CapsuleMesh" id="CapsuleMesh1"]
+radius = 0.35
+height = 1.6
+
+[sub_resource type="CapsuleShape3D" id="CapsuleShape1"]
+radius = 0.35
+height = 1.6
+
+[node name="Player" type="CharacterBody3D"]
+script = ExtResource("1_player")
+
+[node name="CollisionShape3D" type="CollisionShape3D" parent="."]
+shape = SubResource("CapsuleShape1")
+
+[node name="CapsuleMesh" type="MeshInstance3D" parent="."]
+mesh = SubResource("CapsuleMesh1")
+
+[node name="Camera3D" type="Camera3D" parent="."]
+transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0.6, 0)
+current = true

scenes/server.tscn

@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3]
+
+[ext_resource type="Script" path="res://scripts/server.gd" id="1_server"]
+
+[node name="Server" type="Node"]
+script = ExtResource("1_server")

scenes/server_player.tscn

@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3]
+
+[ext_resource type="Script" path="res://scripts/player_spawner.gd" id="1"]
+
+[node name="Player" type="CharacterBody3D"]
+script = ExtResource("1")

scripts/network_client.gd

@@ -0,0 +1,234 @@
+class_name NetworkClient
+extends Node
+## Client-side networked player: input prediction + server reconciliation.
+##
+## Implements docs/architecture/networking.md §5 (Prediction & Reconciliation)
+## for the *local* player only -- remote-entity interpolation (§5.3) and full
+## delta-compressed multi-entity snapshots (§6) are explicitly out of scope
+## for this first pass; the server already only ever has one player in PC2's
+## single-peer testing, and this task's own description scopes it to "the
+## player controller built in the dependency task" (singular).
+##
+## RPC path-matching, the part that makes this actually work:
+## Godot's high-level rpc_id() resolves the *receiving* node by matching the
+## *sending* node's NodePath on the caller's side. The server (scripts/
+## server.gd) is the SceneTree root node named "Server" when the dedicated
+## server runs scenes/server.tscn as its main scene, and it spawns each
+## connected player as a *child* of itself named "Player_<peer_id>"
+## (scripts/server.gd's _on_peer_connected). For an RPC sent by the client to
+## actually land on the right node, the client needs a LOCAL node tree at the
+## exact same paths -- /root/Server for _receive_snapshot (called by the
+## server on itself), and /root/Server/Player_<own_peer_id> for
+## rpc_request_input (a real method on the server's PlayerNode). Those local
+## nodes don't need to run any server logic -- they only need to exist at the
+## right path so Godot's RPC routing finds them. connect_to_server() builds
+## that structure once the peer id is known (only available after the ENet
+## handshake completes).
+##
+## Usage: instantiate directly (not an autoload -- this only exists for the
+## lifetime of an actual multiplayer session, not on every client launch):
+##     var net := NetworkClient.new()
+##     get_tree().root.add_child(net)
+##     var ok := await net.connect_to_server("127.0.0.1", 7777)
+
+
+# ---------------------------------------------------------------------------
+# Movement constants -- MUST match scripts/player_spawner.gd exactly, per
+# docs/architecture/networking.md §5.1 ("the same physics constants as the
+# server"). A mismatch here doesn't break anything outright, it just makes
+# reconciliation corrections more frequent/visible.
+# ---------------------------------------------------------------------------
+
+const WALK_SPEED: float = 5.0
+const JUMP_VELOCITY: float = 4.5
+const GRAVITY: float = 9.8
+
+## How far predicted and authoritative position can drift before snapping
+## rather than trusting the prediction was "close enough." Per §5.2.
+const RECONCILE_ERROR_THRESHOLD: float = 0.5
+
+## How many past predicted states to keep for reconciliation replay. Real
+## sizing per §5.4 is RTT-adaptive; a fixed generous buffer is the
+## appropriately-scoped first pass here -- 120 ticks at a 30Hz send rate is
+## 4 seconds of history, comfortably more than any realistic LAN/local RTT.
+const PREDICTION_BUFFER_SIZE: int = 120
+
+signal reconciled(correction_distance: float)
+signal connected_to_server
+signal connection_failed
+
+
+var peer: ENetMultiplayerPeer
+var _server_root: Node          # local /root/Server proxy
+var _player_proxy: Node         # local /root/Server/Player_<peer_id> proxy
+
+var _seq: int = 0
+## Ring buffer of {seq, input, position, velocity} predicted at send time,
+## oldest first. Trimmed as the server acknowledges ticks via snapshots.
+var _prediction_buffer: Array[Dictionary] = []
+
+var position: Vector3 = Vector3.ZERO
+var velocity: Vector3 = Vector3.ZERO
+var _on_floor: bool = false
+
+
+func connect_to_server(host: String, port: int) -> bool:
+	peer = ENetMultiplayerPeer.new()
+	var err := peer.create_client(host, port)
+	if err != OK:
+		push_error("NetworkClient: create_client failed: %d" % err)
+		connection_failed.emit()
+		return false
+
+	multiplayer.multiplayer_peer = peer
+	multiplayer.connected_to_server.connect(_on_connected)
+	multiplayer.connection_failed.connect(func():
+		connection_failed.emit()
+	)
+
+	for i in 300:  # ~5s at 60fps
+		await get_tree().process_frame
+		var status := peer.get_connection_status()
+		if status == MultiplayerPeer.CONNECTION_CONNECTED:
+			return true
+		elif status == MultiplayerPeer.CONNECTION_DISCONNECTED:
+			connection_failed.emit()
+			return false
+	connection_failed.emit()
+	return false
+
+
+func _on_connected() -> void:
+	var my_id := multiplayer.get_unique_id()
+
+	# Build the local proxy tree at the exact paths the server's own RPC
+	# calls target -- see the class docstring for why this has to exist.
+	_server_root = Node.new()
+	_server_root.name = "Server"
+	_server_root.set_script(preload("res://scripts/network_receiver_proxy.gd"))
+	get_tree().root.add_child(_server_root)
+	_server_root.set("owner_client", self)
+
+	_player_proxy = Node.new()
+	_player_proxy.name = "Player_%d" % my_id
+	_player_proxy.set_script(preload("res://scripts/network_player_proxy.gd"))
+	_server_root.add_child(_player_proxy)
+
+	connected_to_server.emit()
+
+
+func disconnect_from_server() -> void:
+	if peer:
+		peer.close()
+	if _server_root and is_instance_valid(_server_root):
+		_server_root.queue_free()
+	multiplayer.multiplayer_peer = null
+
+
+# ---------------------------------------------------------------------------
+# Prediction -- called every physics frame by whatever drives input (a real
+# controller, or a test harness). Applies input locally immediately (so it
+# renders with zero perceived latency) and sends it to the server, per §5.1.
+# ---------------------------------------------------------------------------
+
+func predict_and_send(delta: float, move_x: float, move_z: float, jump: bool) -> void:
+	_apply_movement(delta, move_x, move_z, jump)
+
+	_seq += 1
+	var record := {
+		"seq": _seq,
+		"input": {"move_x": move_x, "move_z": move_z, "jump": jump},
+		"position": position,
+		"velocity": velocity,
+	}
+	_prediction_buffer.append(record)
+	if _prediction_buffer.size() > PREDICTION_BUFFER_SIZE:
+		_prediction_buffer.pop_front()
+
+	if _player_proxy and is_instance_valid(_player_proxy):
+		_player_proxy.rpc_id(1, "rpc_request_input", record["input"], _seq)
+
+
+func _apply_movement(delta: float, move_x: float, move_z: float, jump: bool) -> void:
+	# Mirrors scripts/player_spawner.gd's _process_input + gravity/jump,
+	# intentionally without its ground-friction smoothing -- friction is a
+	# server-authoritative-feel detail, not something worth risking a
+	# prediction/server mismatch over in this first pass. Position still
+	# reconciles against the server's real (frictioned) result every
+	# snapshot, so this doesn't silently drift.
+	if not _on_floor:
+		velocity.y -= GRAVITY * delta
+
+	var direction := Vector3(move_x, 0.0, move_z)
+	if direction.length() > 0.01:
+		direction = direction.normalized()
+		velocity.x = direction.x * WALK_SPEED
+		velocity.z = direction.z * WALK_SPEED
+	else:
+		velocity.x = 0.0
+		velocity.z = 0.0
+
+	if jump and _on_floor:
+		velocity.y = JUMP_VELOCITY
+
+	position += velocity * delta
+	# Headless prediction has no collision shape of its own to test
+	# is_on_floor() against -- treat "at or below the spawn-plane ground"
+	# as grounded. A real render-side controller would swap this for the
+	# actual CharacterBody3D.is_on_floor() of whatever visual node this
+	# drives; this class only owns the *networking* half.
+	if position.y <= 0.0:
+		position.y = 0.0
+		velocity.y = 0.0
+		_on_floor = true
+	else:
+		_on_floor = false
+
+
+# ---------------------------------------------------------------------------
+# Reconciliation -- called by _ReceiverScript when a snapshot arrives.
+# ---------------------------------------------------------------------------
+
+func _handle_snapshot(snapshot_data: Dictionary) -> void:
+	var my_id := multiplayer.get_unique_id()
+	var players: Dictionary = snapshot_data.get("players", {})
+	# Server keys player_states by peer_id -- Dictionary keys from JSON-ish
+	# RPC payloads can arrive as String or int depending on the transport
+	# encoding, so check both rather than assuming.
+	var my_state: Variant = players.get(my_id, players.get(str(my_id), null))
+	if my_state == null or not (my_state is Dictionary):
+		return
+
+	var authoritative_pos: Vector3 = (my_state as Dictionary).get("position", position)
+
+	# Real limitation, noted explicitly rather than silently faked: the
+	# server's snapshot_state (scripts/server.gd's _broadcast_snapshot) does
+	# not currently echo back "last input seq processed for this peer" --
+	# its `tick` field is the server's own internal simulation tick counter,
+	# a completely different clock from this client's per-input `_seq`. True
+	# tick-correlated rollback (docs/architecture/networking.md §5.2 step 4,
+	# "re-simulate any inputs that occurred after the server's tick") needs
+	# that ack echoed back per-peer -- a real, scoped follow-up, not
+	# something to fake here. Until then, reconcile against the MOST RECENT
+	# prediction (not a tick-matched one): still a real error measurement
+	# and a real correction, just without precise replay-from-exact-tick.
+	if _prediction_buffer.is_empty():
+		return
+	var latest_entry: Dictionary = _prediction_buffer[-1]
+
+	var error: float = (latest_entry["position"] as Vector3).distance_to(authoritative_pos)
+	if error <= RECONCILE_ERROR_THRESHOLD:
+		return  # Close enough -- prediction was correct, nothing to do.
+
+	# Correct: snap to the authoritative position. Without a real ack-seq
+	# from the server there's no reliable "replay inputs after this point"
+	# window to recompute, so the buffer is cleared and prediction resumes
+	# fresh from the corrected position on the next input -- still visibly
+	# responsive (no waiting for a round trip before the *next* input
+	# applies), just without this pass replaying in-flight inputs.
+	position = authoritative_pos
+	velocity = Vector3.ZERO
+	_prediction_buffer.clear()
+
+	reconciled.emit(error)
+

scripts/network_player_proxy.gd

@@ -0,0 +1,43 @@
+extends Node
+## Client-side proxy for the server's real PlayerNode (scripts/
+## player_spawner.gd), attached at runtime to a Node named "Player_<peer_id>"
+## under the /root/Server proxy by NetworkClient._on_connected().
+##
+## rpc_request_input is the only one of these actually CALLED from this
+## side -- the real implementations all live on the server. But two things
+## force every @rpc method on the real PlayerNode to be mirrored here too,
+## not just the one this class uses:
+##   1. Godot's rpc_id() looks up the RPC transfer config (mode/reliability)
+##      from the LOCAL script before it will even send a call, so the method
+##      being called has to be declared locally with a matching annotation.
+##   2. Godot's multiplayer layer also verifies an "RPC node checksum" --
+##      both peers must declare the *same set* of @rpc methods at a matching
+##      path, or every RPC at that path starts failing, not just the one
+##      that's actually missing. So even rpc_request_interact/attack/
+##      set_position/set_rotation, which this class never calls, have to be
+##      declared here with matching annotations or rpc_request_input itself
+##      breaks too.
+
+@rpc("any_peer", "call_remote", "reliable")
+func rpc_request_input(_input_state: Dictionary, _seq: int) -> void:
+	pass  # Never invoked locally -- see the note above.
+
+
+@rpc("any_peer", "call_remote", "reliable")
+func rpc_request_interact(_target_id: int) -> void:
+	pass
+
+
+@rpc("any_peer", "call_remote", "reliable")
+func rpc_request_attack(_target_id: int, _aim_dir: Vector3) -> void:
+	pass
+
+
+@rpc("authority", "call_remote", "reliable")
+func rpc_set_position(_pos: Vector3) -> void:
+	pass
+
+
+@rpc("authority", "call_remote", "reliable")
+func rpc_set_rotation(_rot: Vector3) -> void:
+	pass

scripts/network_receiver_proxy.gd

@@ -0,0 +1,38 @@
+extends Node
+## Client-side proxy node, attached at runtime to a Node named "Server" at
+## the SceneTree root by NetworkClient.connect_to_server(). Exists purely so
+## Godot's RPC path-matching finds a receiver for _receive_snapshot -- see
+## network_client.gd's class docstring for the full explanation of why this
+## has to exist at this exact path. Not a real server in any sense.
+##
+## Godot's multiplayer layer verifies an "RPC node checksum" -- both peers
+## must declare the *same set* of @rpc methods at a matching path, or every
+## RPC at that path (not just the mismatched one) starts failing with
+## "rpc node checksum failed". So every @rpc method scripts/server.gd
+## declares on its own root "Server" node has to be mirrored here too, even
+## the ones this proxy never actually needs to receive.
+
+var owner_client: Node = null
+
+
+## Must match scripts/server.gd's own @rpc annotation on _receive_snapshot
+## exactly -- Godot enforces the receiving method's declared mode/transfer
+## config, a mismatch here would silently drop the call.
+@rpc("any_peer", "call_remote", "reliable")
+func _receive_snapshot(snapshot_data: Dictionary) -> void:
+	if owner_client and is_instance_valid(owner_client):
+		owner_client._handle_snapshot(snapshot_data)
+
+
+## Mirrors scripts/server.gd's _kick -- never actually invoked on this side
+## (the server calls it on a Player_<id> node's own rpc_id target, not this
+## root proxy), declared only so the RPC checksum for this path matches.
+@rpc("any_peer", "call_remote", "reliable")
+func _kick(_reason: String) -> void:
+	pass
+
+
+## Mirrors scripts/server.gd's _disconnect -- same reasoning as _kick above.
+@rpc("call_remote", "reliable")
+func _disconnect(_reason: String) -> void:
+	pass

scripts/player.gd

@@ -0,0 +1,146 @@
+class_name Player
+extends CharacterBody3D
+## The player character controller.
+##
+## A simple CharacterBody3D with WASD/arrow locomotion, gravity, jump, and a
+## first-person Camera3D with mouse-look.  Reads the spawn point from the
+## current scene's `PlayerSpawn` Marker3D (see docs/architecture/pc2_test_level.md §3).
+##
+## No networking, no chunk code, no avatar UI — PC2 is local-only.
+
+
+# ---------------------------------------------------------------------------
+# Movement constants
+# ---------------------------------------------------------------------------
+
+const WALK_SPEED: float = 5.0
+const JUMP_VELOCITY: float = 4.5
+const GRAVITY: float = 9.8
+
+## Mouse-look sensitivity (radians per pixel of relative motion).
+const MOUSE_SENSITIVITY: float = 0.003
+
+## Camera pitch is clamped so the player can't flip past looking straight
+## up/down (which would otherwise let mouse-look invert on itself).
+const PITCH_LIMIT: float = deg_to_rad(89.0)
+
+
+# ---------------------------------------------------------------------------
+# Input state
+# ---------------------------------------------------------------------------
+
+var _input_direction := Vector2.ZERO
+var _camera_pitch: float = 0.0
+
+@onready var _camera: Camera3D = $Camera3D
+
+
+# ---------------------------------------------------------------------------
+# _ready — spawn at PlayerSpawn marker, capture the mouse for look
+# ---------------------------------------------------------------------------
+
+func _ready() -> void:
+	# Per §3 of pc2_test_level.md: look up PlayerSpawn from the current
+	# scene root.  The lookup walks the full subtree (recursive=true) so
+	# it finds the marker whether it is a direct child of the level or
+	# nested deeper.
+	#
+	# current_scene is null in headless --script mode and in any scene
+	# before the main scene is fully swapped in, so guard it rather than
+	# blindly dereferencing.
+	var current_scene: Node = get_tree().current_scene
+	var spawn: Node = null
+	if current_scene != null:
+		spawn = current_scene.find_child("PlayerSpawn", true, false)
+
+	if spawn is Node3D:
+		global_position = (spawn as Node3D).global_position
+		# Align player forward with spawn yaw (optional polish).
+		var spawn_yaw := (spawn as Node3D).rotation.y
+		rotation.y = spawn_yaw
+	else:
+		push_warning("player.gd: no PlayerSpawn marker found; spawning at origin")
+		global_position = Vector3(0, 1.0, 0)
+
+	# Capture the mouse for FPS-style look. Headless/test runs have no real
+	# window to capture input for, so guard against that rather than error.
+	if DisplayServer.get_name() != "headless":
+		Input.mouse_mode = Input.MOUSE_MODE_CAPTURED
+
+
+# ---------------------------------------------------------------------------
+# _unhandled_input — capture keyboard / mouse for movement
+# ---------------------------------------------------------------------------
+
+func _unhandled_input(event: InputEvent) -> void:
+	if event is InputEventKey:
+		var key := event as InputEventKey
+		if key.pressed and not key.echo:
+			_update_input_direction(key)
+		elif not key.pressed:
+			_clear_input_direction(key)
+		# Escape exits the level back to the world browse list, mirroring
+		# the Back button pattern already used in world_list.gd/main_menu.gd.
+		if key.pressed and key.keycode == KEY_ESCAPE:
+			Input.mouse_mode = Input.MOUSE_MODE_VISIBLE
+			get_tree().change_scene_to_file("res://scenes/world_list.tscn")
+	elif event is InputEventMouseMotion and Input.mouse_mode == Input.MOUSE_MODE_CAPTURED:
+		_handle_mouse_look(event as InputEventMouseMotion)
+
+
+func _update_input_direction(key: InputEventKey) -> void:
+	match key.keycode:
+		KEY_W, KEY_UP:
+			_input_direction.y += 1.0
+		KEY_S, KEY_DOWN:
+			_input_direction.y -= 1.0
+		KEY_A, KEY_LEFT:
+			_input_direction.x -= 1.0
+		KEY_D, KEY_RIGHT:
+			_input_direction.x += 1.0
+
+
+func _clear_input_direction(key: InputEventKey) -> void:
+	match key.keycode:
+		KEY_W, KEY_UP:
+			_input_direction.y -= 1.0
+		KEY_S, KEY_DOWN:
+			_input_direction.y += 1.0
+		KEY_A, KEY_LEFT:
+			_input_direction.x += 1.0
+		KEY_D, KEY_RIGHT:
+			_input_direction.x -= 1.0
+
+
+func _handle_mouse_look(event: InputEventMouseMotion) -> void:
+	# Yaw rotates the whole body (so movement direction turns with the
+	# look direction); pitch only tilts the camera, so the capsule itself
+	# never tips over.
+	rotation.y -= event.relative.x * MOUSE_SENSITIVITY
+	_camera_pitch = clampf(_camera_pitch - event.relative.y * MOUSE_SENSITIVITY, -PITCH_LIMIT, PITCH_LIMIT)
+	_camera.rotation.x = _camera_pitch
+
+
+# ---------------------------------------------------------------------------
+# Physics — gravity, jump, move_and_slide
+# ---------------------------------------------------------------------------
+
+func _physics_process(delta: float) -> void:
+	# Apply gravity.
+	if not is_on_floor():
+		velocity.y -= GRAVITY * delta
+
+	# Jump.
+	if is_on_floor() and Input.is_action_just_pressed("ui_accept"):
+		velocity.y = JUMP_VELOCITY
+
+	# Build movement direction from input. Godot's local "forward" is -Z, not
+	# +Z, so W (input.y = +1) must use -basis.z -- using +basis.z here would
+	# move the player backward when pressing forward (confirmed by reading
+	# Camera3D/Node3D's own convention: a node looks down its local -Z).
+	var direction := (_input_direction.x * transform.basis.x -
+		_input_direction.y * transform.basis.z).normalized()
+	velocity.x = direction.x * WALK_SPEED
+	velocity.z = direction.z * WALK_SPEED
+
+	move_and_slide()

scripts/player_spawner.gd

@@ -0,0 +1,232 @@
+class_name PlayerNode
+extends CharacterBody3D
+## PlayerNode - Server-side player entity.
+##
+## Represents a connected player on the server. Handles movement,
+## input processing, and state synchronization.
+
+# --- Signals ---
+signal health_changed(new_health: int)
+signal player_died(player_node: PlayerNode)
+
+
+# --- Constants ---
+const WALK_SPEED := 5.0
+const SPRINT_MULTIPLIER := 1.6
+const JUMP_VELOCITY := 4.5
+const GRAVITY := 9.8
+const MAX_FALL_SPEED := 20.0
+const FRICTION := 8.0
+const AIR_CONTROL := 0.3
+
+# --- Configurable ---
+@export var walk_speed: float = WALK_SPEED
+@export var sprint_multiplier: float = SPRINT_MULTIPLIER
+@export var jump_velocity: float = JUMP_VELOCITY
+@export var max_fall_speed: float = MAX_FALL_SPEED
+
+# --- State ---
+@export var max_health: int = 100
+var current_health: int = 0
+var is_alive: bool = true
+var is_sprinting: bool = false
+var peer_id: int = -1
+var player_name: String = ""
+var entity_id: int = 0
+
+# --- Input buffer ---
+var _input_queue: Array[Dictionary] = []
+var _last_processed_seq: int = -1
+
+# --- Movement ---
+var _velocity: Vector3 = Vector3.ZERO
+
+
+func _ready() -> void:
+	current_health = max_health
+	velocity = _velocity
+	# Start alive
+	is_alive = true
+
+
+func _physics_process(delta: float) -> void:
+	if not is_alive:
+		return
+	
+	# Process input from queue
+	_process_input(delta)
+	
+	# Apply gravity
+	if not is_on_floor():
+		velocity.y -= GRAVITY * delta
+		velocity.y = clampf(velocity.y, -max_fall_speed, max_fall_speed)
+	
+	# Apply friction on ground
+	if is_on_floor():
+		var move_dir := Vector2(velocity.x, velocity.z)
+		if move_dir.length() > 0.01:
+			var friction_factor := clampf(FRICTION * delta, 0.0, 1.0)
+			velocity.x = move_dir.normalized().x * move_dir.length() * (1.0 - friction_factor)
+			velocity.z = move_dir.normalized().y * move_dir.length() * (1.0 - friction_factor)
+		else:
+			velocity.x = 0.0
+			velocity.z = 0.0
+	
+	# Move and slide
+	velocity.y = clampf(velocity.y, -max_fall_speed, max_fall_speed)
+	move_and_slide()
+	
+	# Update visual position (for remote clients via RPC)
+	_update_visual_state()
+
+
+func _process_input(delta: float) -> void:
+	"""Process buffered input from the server's input queue."""
+	if _input_queue.is_empty():
+		return
+	
+	var input_data: Dictionary = _input_queue.pop_front()
+	var input_state: Dictionary = input_data.get("input_state", {})
+	
+	# Calculate movement direction
+	var direction := Vector3.ZERO
+	direction.x = input_state.get("move_x", 0.0)
+	direction.z = input_state.get("move_z", 0.0)
+	
+	# Sprint check
+	is_sprinting = input_state.get("sprint", false)
+	
+	if direction.length() > 0.01:
+		direction = direction.normalized()
+		var speed = walk_speed * sprint_multiplier if is_sprinting else walk_speed
+		velocity.x = direction.x * speed
+		velocity.z = direction.z * speed
+	else:
+		# On ground, apply friction (handled in physics_process)
+		if not is_on_floor():
+			velocity.x *= (1.0 - AIR_CONTROL * delta * 5.0)
+			velocity.z *= (1.0 - AIR_CONTROL * delta * 5.0)
+	
+	# Jump
+	if input_state.get("jump", false) and is_on_floor():
+		velocity.y = jump_velocity
+
+
+func take_damage(amount: int, source_id: int) -> Dictionary:
+	"""Take damage and return result dict."""
+	if not is_alive:
+		return {"success": false, "reason": "already_dead"}
+	
+	current_health = max(0, current_health - amount)
+	health_changed.emit(current_health)
+	
+	if current_health <= 0:
+		die()
+		return {"success": true, "health": 0, "dead": true}
+	
+	return {"success": true, "health": current_health}
+
+
+func die() -> void:
+	"""Handle player death."""
+	is_alive = false
+	velocity = Vector3.ZERO
+	player_died.emit(self)
+	
+	# Respawn after delay
+	await get_tree().create_timer(3.0).timeout
+	respawn()
+
+
+func respawn() -> void:
+	"""Respawn the player at spawn point."""
+	current_health = max_health
+	is_alive = true
+	velocity = Vector3.ZERO
+	health_changed.emit(current_health)
+	
+	# Move to spawn point (default: origin)
+	position = Vector3.ZERO
+
+
+func set_input_queue(inputs: Array[Dictionary]) -> void:
+	"""Set the input queue from the server."""
+	_input_queue = inputs
+
+
+func get_state() -> Dictionary:
+	"""Get current player state for replication."""
+	return {
+		"entity_id": entity_id,
+		"peer_id": peer_id,
+		"position": position,
+		"rotation": rotation,
+		"health": current_health,
+		"max_health": max_health,
+		"is_alive": is_alive,
+		"is_sprinting": is_sprinting,
+	}
+
+
+func get_server_state() -> Dictionary:
+	"""Get current player state for server snapshot broadcast."""
+	return get_state()
+
+
+func process_server_input(tick: int) -> void:
+	"""Called by server tick to process buffered input."""
+	# This is called from the server's _tick loop.
+	# The input queue is populated by RPCs from clients.
+	pass
+
+
+func _update_visual_state() -> void:
+	"""Update visual state (for remote interpolation)."""
+	# In a full implementation, this would update a remote player's
+	# visual representation. For now, the node itself is the authority.
+	pass
+
+
+# --- RPCs ---
+
+@rpc("any_peer", "call_remote", "reliable")
+func rpc_request_input(input_state: Dictionary, seq: int) -> void:
+	"""Receive input from client."""
+	if not is_alive:
+		return
+	# Store for processing in _physics_process
+	_input_queue.append({
+		"input_state": input_state,
+		"seq": seq,
+		"timestamp": Time.get_ticks_msec(),
+	})
+
+
+@rpc("any_peer", "call_remote", "reliable")
+func rpc_request_interact(target_id: int) -> void:
+	"""Handle interaction request from client."""
+	if not is_alive:
+		return
+	# TODO: Implement interaction logic
+	print("Player %d interacted with entity %d" % [peer_id, target_id])
+
+
+@rpc("any_peer", "call_remote", "reliable")
+func rpc_request_attack(target_id: int, aim_dir: Vector3) -> void:
+	"""Handle attack request from client."""
+	if not is_alive:
+		return
+	# TODO: Implement attack logic
+	print("Player %d attacked entity %d with aim %s" % [peer_id, target_id, aim_dir])
+
+
+@rpc("authority", "call_remote", "reliable")
+func rpc_set_position(pos: Vector3) -> void:
+	"""Server authoritative position update."""
+	position = pos
+
+
+@rpc("authority", "call_remote", "reliable")
+func rpc_set_rotation(rot: Vector3) -> void:
+	"""Server authoritative rotation update."""
+	rotation = rot

scripts/player_spawner.gd.uid

@@ -0,0 +1 @@
+uid://br27owjh2f5xd

scripts/server.gd

@@ -0,0 +1,174 @@
+## ServerMain - Dedicated server root node.
+## Accepts ENet connections, spawns Player nodes for each peer,
+## and runs the simulation tick loop at 20 Hz.
+extends Node
+
+
+## Maximum number of concurrent players.
+const MAX_PLAYERS := 16
+
+## Server tick rate (Hz).
+const TICK_RATE := 20
+
+## Tick duration in seconds.
+const TICK_DURATION := 1.0 / TICK_RATE
+
+## ENet server port.
+const SERVER_PORT := 7777
+
+## Network peer used for ENet communication.
+var network_peer: ENetMultiplayerPeer
+
+## Map of peer_id -> Player node.
+var players: Dictionary = {}
+
+## Current tick counter (server-authoritative).
+var tick: int = 0
+
+## Whether the server is running.
+var is_running: bool = false
+
+## Accumulated real time for fixed timestep simulation.
+var accumulator: float = 0.0
+
+## Player scene resource (loaded once).
+var _player_scene: PackedScene
+
+
+func _ready() -> void:
+	# Preload the player scene once.
+	_player_scene = preload("res://scenes/server_player.tscn")
+
+	# Create and assign the ENet server peer.
+	network_peer = _create_server_peer()
+	if network_peer:
+		multiplayer.multiplayer_peer = network_peer
+		is_running = true
+		print("[Server] Started on port %d" % SERVER_PORT)
+	else:
+		printerr("[Server] Failed to create ENet peer.")
+		get_tree().quit(1)
+
+
+# ---------------------------------------------------------------------------
+# Server creation
+# ---------------------------------------------------------------------------
+
+func _create_server_peer() -> ENetMultiplayerPeer:
+	var peer := ENetMultiplayerPeer.new()
+	var error := peer.create_server(SERVER_PORT, MAX_PLAYERS)
+	if error != OK:
+		printerr("[Server] create_server error: %d" % error)
+		return null
+	return peer
+
+
+# ---------------------------------------------------------------------------
+# Fixed-timestep simulation loop
+# ---------------------------------------------------------------------------
+
+func _process(delta: float) -> void:
+	if not is_running:
+		return
+
+	# Fixed timestep accumulator.
+	accumulator += delta
+	while accumulator >= TICK_DURATION:
+		accumulator -= TICK_DURATION
+		_tick()
+
+
+func _tick() -> void:
+	"""Main server simulation tick (called at TICK_RATE)."""
+	tick += 1
+
+	# Process player inputs and update state.
+	for peer_id in players:
+		var player: Node3D = players[peer_id]
+		if player and player.has_method("process_server_input"):
+			player.process_server_input(tick)
+
+	# Broadcast snapshot to all clients.
+	_broadcast_snapshot()
+
+
+func _broadcast_snapshot() -> void:
+	"""Broadcast the current authoritative state to all connected clients."""
+	var snapshot_data := {
+		"tick": tick,
+		"players": {},
+	}
+
+	for peer_id in players:
+		var player: Node3D = players[peer_id]
+		if player and player.has_method("get_server_state"):
+			snapshot_data.players[peer_id] = player.get_server_state()
+
+	# Send snapshot to all peers except the server itself (peer_id == 1).
+	var peer_ids: Array = multiplayer.get_peers()
+	for pid in peer_ids:
+		if pid == 1:  # 1 is the server itself
+			continue
+		rpc_id(pid, "_receive_snapshot", snapshot_data)
+
+
+# Remote: clients receive snapshots.
+@rpc("any_peer", "call_remote", "reliable")
+func _receive_snapshot(snapshot_data: Dictionary) -> void:
+	pass  # Handled by client scene.
+
+
+# ---------------------------------------------------------------------------
+# Connection lifecycle
+# ---------------------------------------------------------------------------
+
+func _on_peer_connected(peer_id: int) -> void:
+	print("[Server] Peer %d connected." % peer_id)
+
+	if players.size() >= MAX_PLAYERS:
+		print("[Server] Max players reached. Disconnecting peer %d." % peer_id)
+		rpc_id(peer_id, "_kick", "Server is full.")
+		return
+
+	# Spawn a Player node for this peer.
+	var player: Node3D = _player_scene.instantiate()
+	player.name = "Player_%d" % peer_id
+	player.peer_id = peer_id
+	add_child(player)
+	players[peer_id] = player
+
+	print("[Server] Spawned player node for peer %d." % peer_id)
+
+
+func _on_peer_disconnected(peer_id: int) -> void:
+	print("[Server] Peer %d disconnected." % peer_id)
+	if players.has(peer_id):
+		var player: Node3D = players[peer_id]
+		if player.is_inside_tree():
+			player.queue_free()
+		players.erase(peer_id)
+
+
+# ---------------------------------------------------------------------------
+# RPCs
+# ---------------------------------------------------------------------------
+
+@rpc("any_peer", "call_remote", "reliable")
+func _kick(reason: String) -> void:
+	print("[Server] Kicking caller: %s" % reason)
+	rpc_id(multiplayer.get_remote_sender_id(), "_disconnect", reason)
+
+
+@rpc("call_remote", "reliable")
+func _disconnect(reason: String) -> void:
+	print("[Server] Disconnecting: %s" % reason)
+	get_tree().quit(0)
+
+
+# ---------------------------------------------------------------------------
+# Signal connections
+# ---------------------------------------------------------------------------
+
+func _enter_tree() -> void:
+	multiplayer.peer_connected.connect(_on_peer_connected)
+	multiplayer.peer_disconnected.connect(_on_peer_disconnected)

scripts/server.gd.uid

@@ -0,0 +1 @@
+uid://cwjv826lva2gi

scripts/smoke_test_enter_world.gd

@@ -0,0 +1,146 @@
+extends SceneTree
+## Regression/smoke test for the PC2 "Enter World" flow end to end.
+##
+## Real user path: register -> land on world_list.tscn -> click "Enter World"
+## on a real card -> the playable level (scenes/game.tscn) actually loads
+## with the player spawned in it -> pressing Escape returns to world_list.
+##
+## Run with:
+##     godot --headless --path . --script res://scripts/smoke_test_enter_world.gd
+##
+## Requires the backend to be running (default base URL
+## `application/agp/api_base_url` -> http://127.0.0.1:8000, overridable via
+## AGP_API_BASE_URL) and at least one real world to already exist.
+
+var passed := 0
+var failed := 0
+
+
+func _initialize() -> void:
+	_run()
+
+
+func _run() -> void:
+	await process_frame
+
+	var api := root.get_node("ApiClient")
+	if api == null:
+		printerr("FAIL: ApiClient autoload not found")
+		quit(1)
+		return
+
+	# 1. Register a real user and seed a world so the browse list has a
+	# real card to click, same pattern as smoke_test_world_list.gd.
+	randomize()
+	var unique_id: int = int(Time.get_unix_time_from_system() * 1000) + randi() % 100000
+	var username := "enterworld_%d" % unique_id
+	var email := "enterworld_%d@test.example.com" % unique_id
+	var reg_result: Dictionary = await api.register(username, email, "SmokeTest123!", true)
+	if not _check("setup: register succeeded", reg_result.ok):
+		print("  detail: ", reg_result.detail)
+		_finish()
+		return
+
+	var world_body := JSON.stringify({
+		"name": "EnterWorld Smoke Test World %d" % unique_id,
+		"description": "Seeded by smoke_test_enter_world.gd",
+		"visibility": "public",
+	})
+	var world_result: Dictionary = await api.request(
+		HTTPClient.METHOD_POST, "/api/worlds/", world_body, "application/json", true
+	)
+	if not _check("setup: world created", world_result.ok):
+		print("  detail: ", world_result.detail)
+		_finish()
+		return
+
+	# 2. Load world_list.tscn as a real scene and let it fetch worlds.
+	var packed: PackedScene = load("res://scenes/world_list.tscn")
+	var instance: Control = packed.instantiate()
+	root.add_child(instance)
+	# _ready() kicks off an async _refresh_worlds() -- wait real frames for
+	# the HTTP round trip rather than guessing a fixed count.
+	var world_list_node: VBoxContainer = instance.get_node("VBoxContainer/ScrollContainer/WorldList")
+	var settled := false
+	for i in 120:
+		await process_frame
+		if world_list_node.get_child_count() > 0:
+			settled = true
+			break
+	if not _check("world list populated with at least one card", settled):
+		_finish()
+		return
+
+	# 3. Click "Enter World" on the first real card -- find the button by
+	# walking the card's children rather than assuming an index, so this
+	# doesn't silently pass if _create_world_card's structure changes.
+	var card: Control = world_list_node.get_child(0)
+	var enter_button: Button = _find_button(card, "Enter World")
+	if not _check("Enter World button exists on the card", enter_button != null):
+		_finish()
+		return
+
+	enter_button.pressed.emit()
+	await _wait_for_scene_change(instance, 60)
+
+	var game_scene := current_scene
+	if not _check("game.tscn became current_scene after Enter World", game_scene != null and game_scene != instance):
+		_finish()
+		return
+
+	# 4. Verify the player actually exists and spawned at the level's
+	# PlayerSpawn marker -- not just that *some* scene loaded.
+	var player: Node = game_scene.get_node_or_null("Player")
+	_check("Player node exists in the loaded game scene", player is CharacterBody3D)
+
+	var spawn_marker: Node = game_scene.get_node_or_null("Level/PlayerSpawn")
+	_check("PlayerSpawn marker exists in the loaded level", spawn_marker is Marker3D)
+
+	if player is CharacterBody3D and spawn_marker is Marker3D:
+		var dist := (player as CharacterBody3D).global_position.distance_to((spawn_marker as Marker3D).global_position)
+		_check("player spawned at (or very near) the PlayerSpawn marker", dist < 0.5)
+
+	# 5. Escape should return to world_list.tscn (real key event, not a
+	# direct method call -- proves the actual input binding works).
+	var esc_event := InputEventKey.new()
+	esc_event.keycode = KEY_ESCAPE
+	esc_event.pressed = true
+	Input.parse_input_event(esc_event)
+	await _wait_for_scene_change(game_scene, 60)
+
+	var back_to_menu := current_scene
+	_check("Escape returned to world_list.tscn", back_to_menu != null and back_to_menu.scene_file_path == "res://scenes/world_list.tscn")
+
+	_finish()
+
+
+func _find_button(node: Node, text: String) -> Button:
+	if node is Button and (node as Button).text == text:
+		return node
+	for child in node.get_children():
+		var found := _find_button(child, text)
+		if found:
+			return found
+	return null
+
+
+func _wait_for_scene_change(previous_scene: Node, max_frames: int) -> void:
+	for i in max_frames:
+		await process_frame
+		if current_scene != previous_scene and current_scene != null:
+			return
+
+
+func _check(description: String, condition: bool) -> bool:
+	if condition:
+		print("  PASS: ", description)
+		passed += 1
+	else:
+		printerr("  FAIL: ", description)
+		failed += 1
+	return condition
+
+
+func _finish() -> void:
+	print("\n=== SMOKE RESULT: %d/%d passed ===" % [passed, passed + failed])
+	quit(0 if failed == 0 else 1)

scripts/smoke_test_network_client.gd

@@ -0,0 +1,114 @@
+extends SceneTree
+## Real integration test for NetworkClient (client-side prediction +
+## reconciliation) against an actual dedicated server process.
+##
+## This does NOT boot its own server -- run scenes/server.tscn as a separate
+## process first (see docs/architecture/networking.md's ENet/port setup):
+##     godot --headless --path . scenes/server.tscn &
+## then, from the same project directory:
+##     godot --headless --path . --script res://scripts/smoke_test_network_client.gd
+##
+## Verifies: the client can actually connect over ENet, local prediction
+## moves the player immediately on input (no waiting for the server),
+## server snapshots actually arrive and update the client's authoritative
+## view, and a deliberately-desynced predicted position gets corrected by
+## reconciliation.
+
+var passed := 0
+var failed := 0
+
+
+func _initialize() -> void:
+	_run()
+
+
+func _run() -> void:
+	await process_frame
+
+	var net := NetworkClient.new()
+	root.add_child(net)
+
+	var ok: bool = await net.connect_to_server("127.0.0.1", 7777)
+	if not _check("connected to the real dedicated server", ok):
+		printerr("  Is `godot --headless --path . scenes/server.tscn` running on port 7777?")
+		_finish()
+		return
+
+	# Give the server a few frames to process the connection and spawn our
+	# player node before we start sending input.
+	for i in 10:
+		await process_frame
+
+	# 1. Prediction: pressing "forward" should move the local position
+	# immediately, without waiting for any server round trip.
+	var pos_before: Vector3 = net.position
+	for i in 10:
+		net.predict_and_send(1.0 / 30.0, 0.0, -1.0, false)  # move -Z (forward)
+		await process_frame
+	var pos_after_predict: Vector3 = net.position
+	_check("local prediction moved the player without waiting for the server",
+		pos_after_predict.distance_to(pos_before) > 0.1)
+
+	# 2. Snapshots actually arrive from the real server and get processed --
+	# wait for at least one reconciliation-eligible snapshot by giving it
+	# real time (server broadcasts at its own tick rate).
+	var got_snapshot := false
+	net.reconciled.connect(func(_err): got_snapshot = true)
+	for i in 60:
+		net.predict_and_send(1.0 / 30.0, 0.0, -1.0, false)
+		await process_frame
+	# Reconciliation only actually fires on a real mismatch -- absence of a
+	# large mismatch is a PASS outcome too (means prediction tracked the
+	# server closely), so this alone isn't proof snapshots arrived. Check
+	# that directly instead:
+	_check("prediction buffer has entries (input was actually sent)", net._prediction_buffer.size() > 0)
+
+	# 3. Deliberately desync prediction from reality, then confirm the next
+	# snapshot corrects it -- the real proof reconciliation logic works,
+	# not just that it never had to fire.
+	net.position = Vector3(9999, 9999, 9999)
+	var desynced_pos := net.position
+	# GDScript closures capture local value-type vars (bool/float) by value,
+	# not by reference -- assigning to them *inside* the lambda doesn't
+	# mutate the outer scope's copy. A single-element Array is the standard
+	# workaround (Arrays are reference types, so mutating its contents from
+	# inside the closure is actually visible outside it). Confirmed this was
+	# the real bug here, not the reconciliation logic itself: debug logging
+	# showed net.position correctly snapping back from (9999,9999,9999) to
+	# ~(0,0,0) within a single snapshot, while a bool-based version of this
+	# same check never observed it.
+	var reconcile_state := [false, -1.0]  # [reconciled_this_round, correction_seen]
+	var reconcile_handler := func(err): reconcile_state[0] = true; reconcile_state[1] = err
+	net.reconciled.connect(reconcile_handler)
+	for i in 60:
+		# Keep predicting (with no movement input) so the prediction buffer's
+		# latest entry actually reflects the desynced position -- without
+		# this, the buffer either empties out or keeps stale pre-desync
+		# entries, and _handle_snapshot has nothing real to compare against.
+		net.predict_and_send(1.0 / 30.0, 0.0, 0.0, false)
+		await process_frame
+		if reconcile_state[0]:
+			break
+	net.reconciled.disconnect(reconcile_handler)
+	_check("a deliberately desynced position gets corrected by the next snapshot",
+		reconcile_state[0] and net.position.distance_to(desynced_pos) > 100.0)
+	if reconcile_state[0]:
+		print("  correction distance was ~", reconcile_state[1])
+
+	net.disconnect_from_server()
+	_finish()
+
+
+func _check(description: String, condition: bool) -> bool:
+	if condition:
+		print("  PASS: ", description)
+		passed += 1
+	else:
+		printerr("  FAIL: ", description)
+		failed += 1
+	return condition
+
+
+func _finish() -> void:
+	print("\n=== SMOKE RESULT: %d/%d passed ===" % [passed, passed + failed])
+	quit(0 if failed == 0 else 1)

scripts/smoke_test_player.gd

@@ -0,0 +1,93 @@
+extends SceneTree
+## Smoke test for the player character scene and its spawn behavior.
+##
+## Run with:
+##     godot --headless --path . --script res://scripts/smoke_test_player.gd
+##
+## Loads the test level, verifies the player is present, spawned at the
+## PlayerSpawn marker, and has the expected CharacterBody3D structure.
+
+var _passed := 0
+var _failed := 0
+
+
+func _initialize() -> void:
+	print("SMOKE: starting player smoke test")
+	_run()
+
+
+func _run() -> void:
+	await process_frame
+	print("SMOKE: loading game scene")
+
+	# Load scenes/game.tscn -- the real PC2 composition point (Level + Player
+	# as siblings, per docs/architecture/pc2_test_level.md §4), not the level
+	# scene directly. Use the same SceneTree API as the real game so
+	# `current_scene` is populated before the scene is added and its
+	# _ready() callbacks fire. That ordering is what the player's spawn
+	# lookup (get_tree().current_scene) depends on.
+	var packed: PackedScene = load("res://scenes/game.tscn")
+	var result := change_scene_to_packed(packed)
+	if result != OK:
+		printerr("SMOKE: failed to change scene, error ", result)
+		quit(1)
+		return
+
+	await scene_changed
+	var game: Node3D = current_scene as Node3D
+	print("SMOKE: game scene ready")
+
+	# 1. Verify the player node exists in the scene tree.
+	var player: Node = game.get_node("Player")
+	_check("Player node exists in test level", player != null)
+	_check("Player is a CharacterBody3D", player is CharacterBody3D)
+
+	# 2. Verify the player has the expected child structure.
+	var collision: Node = player.get_node("CollisionShape3D")
+	_check("Player has CollisionShape3D", collision != null)
+	_check("CollisionShape3D has a shape",
+		   collision is CollisionShape3D and (collision as CollisionShape3D).shape != null)
+
+	var mesh: Node = player.get_node("CapsuleMesh")
+	_check("Player has CapsuleMesh", mesh != null)
+	_check("CapsuleMesh has a mesh",
+		   mesh is MeshInstance3D and (mesh as MeshInstance3D).mesh != null)
+
+	# 3. Verify the player spawned at the PlayerSpawn marker position.
+	var spawn_marker: Marker3D = game.get_node("Level/PlayerSpawn")
+	_check("PlayerSpawn marker exists", spawn_marker != null)
+
+	# The player's _ready() should have moved it to the spawn marker's
+	# global position. Compare global positions directly (not local) since
+	# Player and Level sit at different depths under Game.
+	var expected_pos: Vector3 = spawn_marker.global_position
+	_check("Player spawned at PlayerSpawn position",
+		   player.global_position == expected_pos)
+
+	# 4. Verify the player script class_name is correct and has the
+	# movement constants defined.
+	var script: GDScript = player.get_script() as GDScript
+	_check("Player has a script attached", script != null)
+	var constants: Dictionary = script.get_script_constant_map()
+	_check("Player has WALK_SPEED constant", constants.has("WALK_SPEED"))
+	_check("Player has GRAVITY constant", constants.has("GRAVITY"))
+	_check("Player has JUMP_VELOCITY constant", constants.has("JUMP_VELOCITY"))
+	_check("JUMP_VELOCITY is positive (upward)", float(constants.get("JUMP_VELOCITY", -1.0)) > 0.0)
+
+	# 5. Verify the player has a Camera3D so the game is actually viewable
+	# from the player's perspective, not just a walking capsule with no view.
+	var camera: Node = player.get_node_or_null("Camera3D")
+	_check("Player has a Camera3D", camera is Camera3D)
+	_check("Camera3D is current", camera is Camera3D and (camera as Camera3D).current)
+
+	print("\n=== SMOKE RESULT: %d/%d passed ===" % [_passed, _passed + _failed])
+	quit(0 if _failed == 0 else 1)
+
+
+func _check(description: String, condition: bool) -> void:
+	if condition:
+		print("  PASS: ", description)
+		_passed += 1
+	else:
+		printerr("  FAIL: ", description)
+		_failed += 1

scripts/world_list.gd

@@ -135,8 +135,23 @@ func _create_world_card(world_dict: Dictionary) -> Control:
 	meta_label.add_theme_font_size_override("font_size", 12)
 	meta_label.add_theme_color_override("font_color", Color(0.5, 0.5, 0.5, 1.0))
 
+	# PC2: the only thing a world actually loads into right now is the one
+	# shared playable test level (scenes/game.tscn) -- there's no per-world
+	# content yet, so "Enter" doesn't need the world's id for anything.
+	# Real per-world level loading is a later concern once worlds actually
+	# have their own content to load.
+	var enter_button := Button.new()
+	enter_button.text = "Enter World"
+	enter_button.size_flags_horizontal = Control.SIZE_SHRINK_BEGIN
+	enter_button.pressed.connect(_on_enter_world_pressed)
+
 	card.add_child(name_label)
 	card.add_child(desc_label)
 	card.add_child(meta_label)
+	card.add_child(enter_button)
 
 	return panel
+
+
+func _on_enter_world_pressed() -> void:
+	get_tree().change_scene_to_file("res://scenes/game.tscn")