WIP checkpoint: US-1: Asset Import Pipeline — glTF upload endpoint with metadata extraction

# Conflicts:
#	.gitignore
#	project.godot

.gitignore

@@ -1,2 +1,10 @@
 # Godot 4 editor cache/import directory
 .godot/
+
+# Godot export artifacts
+export/
+*.tmp
+
+# OS
+.DS_Store
+Thumbs.db

backend/alembic/versions/0002_add_date_of_birth_to_users.py

@@ -0,0 +1,30 @@
+"""add date_of_birth column to users table
+
+Revision ID: 0002_add_date_of_birth_to_users
+Revises: 0001_initial
+Create Date: 2025-01-01 00:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision: str = "0002_add_date_of_birth_to_users"
+down_revision: Union[str, None] = "0001_initial"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Add date_of_birth column to users table."""
+    op.add_column(
+        "users",
+        sa.Column("date_of_birth", sa.Date(), nullable=True),
+    )
+
+
+def downgrade() -> None:
+    """Remove date_of_birth column from users table."""
+    op.drop_column("users", "date_of_birth")

backend/app/models/asset.py

@@ -3,6 +3,10 @@ from sqlalchemy.dialects.postgresql import ENUM
 from sqlalchemy.orm import relationship
 from sqlalchemy.sql import func
 import enum
+import json
+from typing import Optional, List
+
+from pydantic import BaseModel as PydanticBaseModel
 
 from app.database import Base
 
@@ -38,3 +42,31 @@ class Asset(Base):
 
     owner = relationship("User", back_populates="assets")
     world = relationship("World", back_populates="assets")
+
+
+class GLTFMetadata(PydanticBaseModel):
+    """Pydantic schema for glTF asset metadata."""
+    mesh_count: Optional[int] = None
+    vertex_count: Optional[int] = None
+    has_animation: bool = False
+    texture_refs: Optional[List[str]] = None
+    tags: Optional[List[str]] = None
+
+    model_config = {"from_attributes": True}
+
+
+def parse_metadata_json(metadata_text: Optional[str]) -> dict:
+    """Parse the metadata_json text field into a dict, handling None gracefully."""
+    if not metadata_text:
+        return {}
+    try:
+        return json.loads(metadata_text)
+    except (json.JSONDecodeError, TypeError):
+        return {}
+
+
+def serialize_metadata(metadata: dict) -> Optional[str]:
+    """Serialize metadata dict to JSON string for storage."""
+    if not metadata:
+        return None
+    return json.dumps(metadata)

backend/app/models/user.py

@@ -1,4 +1,7 @@
-from sqlalchemy import Column, Integer, String, Boolean, DateTime
+from datetime import date
+from typing import Optional
+
+from sqlalchemy import Column, Integer, String, Boolean, DateTime, Date
 from sqlalchemy.orm import relationship
 from sqlalchemy.sql import func
 
@@ -12,6 +15,7 @@ class User(Base):
     username = Column(String(50), unique=True, index=True, nullable=False)
     email = Column(String(120), unique=True, index=True, nullable=False)
     hashed_password = Column(String(255), nullable=False)
+    date_of_birth = Column(Date, nullable=True)
     is_active = Column(Boolean, default=True)
     created_at = Column(DateTime(timezone=True), server_default=func.now())
     updated_at = Column(DateTime(timezone=True), onupdate=func.now())
@@ -19,3 +23,15 @@ class User(Base):
     sessions = relationship("Session", back_populates="user", cascade="all, delete-orphan")
     worlds = relationship("World", back_populates="owner")
     assets = relationship("Asset", back_populates="owner")
+
+    @property
+    def is_adult(self) -> bool:
+        """Return True if the user is 18 or older based on date_of_birth."""
+        if self.date_of_birth is None:
+            return False
+        today = date.today()
+        age = today.year - self.date_of_birth.year
+        # Adjust if birthday hasn't occurred yet this year
+        if (today.month, today.day) < (self.date_of_birth.month, self.date_of_birth.day):
+            age -= 1
+        return age >= 18

backend/app/routers/auth.py

@@ -1,10 +1,10 @@
 """Authentication router - login, register, token refresh."""
 
-from datetime import datetime, timedelta, timezone
+from datetime import date, datetime, timedelta, timezone
 
 from fastapi import APIRouter, Depends, HTTPException, status
 from fastapi.security import OAuth2PasswordRequestForm
-from pydantic import BaseModel, EmailStr
+from pydantic import BaseModel, EmailStr, field_validator
 
 from jose import jwt
 from passlib.context import CryptContext
@@ -32,12 +32,24 @@ class RegisterRequest(BaseModel):
     username: str
     email: EmailStr
     password: str
+    date_of_birth: str  # ISO format date string (YYYY-MM-DD)
+
+    @field_validator("date_of_birth")
+    @classmethod
+    def validate_date_of_birth(cls, v: str) -> str:
+        """Validate that the date string is a valid date in YYYY-MM-DD format."""
+        try:
+            datetime.strptime(v, "%Y-%m-%d")
+        except ValueError:
+            raise ValueError("date_of_birth must be in YYYY-MM-DD format")
+        return v
 
 
 class UserResponse(BaseModel):
     id: int
     username: str
     email: str
+    date_of_birth: str | None = None
     is_active: bool
     created_at: datetime | None = None
 
@@ -65,11 +77,44 @@ def hash_password(password: str) -> str:
     return pwd_context.hash(password)
 
 
+def calculate_age(birth_date: date, today: date | None = None) -> int:
+    """Calculate age in years from a birth date.
+
+    Args:
+        birth_date: The person's date of birth.
+        today: The reference date. Defaults to today's date (UTC).
+
+    Returns:
+        Age in whole years as of the reference date.
+    """
+    if today is None:
+        today = datetime.now(timezone.utc).date()
+
+    age = today.year - birth_date.year
+    # Adjust if birthday hasn't occurred yet this year
+    if (today.month, today.day) < (birth_date.month, birth_date.day):
+        age -= 1
+    return age
+
+
 # --- Endpoints ---
 
 @router.post("/register", response_model=TokenResponse, status_code=status.HTTP_201_CREATED)
 async def register(req: RegisterRequest, db: AsyncSession = Depends(get_db)):
-    """Register a new user and return an access token."""
+    """Register a new user and return an access token.
+
+    Requires date_of_birth and rejects users under 18.
+    """
+    # Parse and validate date_of_birth
+    dob = datetime.strptime(req.date_of_birth, "%Y-%m-%d").date()
+    age = calculate_age(dob)
+
+    if age < 18:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Must be 18 or older to register (provided date of birth: {req.date_of_birth})",
+        )
+
     # Check if username already exists
     result = await db.execute(select(User).where(User.username == req.username))
     if result.scalar_one_or_none():
@@ -90,6 +135,7 @@ async def register(req: RegisterRequest, db: AsyncSession = Depends(get_db)):
         username=req.username,
         email=req.email,
         hashed_password=hash_password(req.password),
+        date_of_birth=dob,
     )
     db.add(user)
     await db.commit()

backend/pytest.ini

@@ -0,0 +1,3 @@
+[pytest]
+asyncio_mode = auto
+testpaths = tests

backend/tests/test_auth_age_gate.py

@@ -0,0 +1,94 @@
+"""Tests for the 18+ age gate on user registration."""
+
+from datetime import date, timedelta
+
+import pytest
+
+from app.routers.auth import calculate_age
+
+
+class TestCalculateAge:
+    """Unit tests for the calculate_age helper."""
+
+    def test_exactly_18(self):
+        """A person born exactly 18 years ago today is 18."""
+        today = date(2025, 6, 15)
+        dob = today.replace(year=today.year - 18)
+        assert calculate_age(dob, today=today) == 18
+
+    def test_just_turned_18(self):
+        """A person who turned 18 yesterday is 18."""
+        today = date(2025, 6, 15)
+        dob = today.replace(year=today.year - 18) - timedelta(days=1)
+        assert calculate_age(dob, today=today) == 18
+
+    def test_one_day_short_of_18(self):
+        """A person born one day after their 18th birthday is 17."""
+        today = date(2025, 6, 15)
+        dob = today.replace(year=today.year - 18) + timedelta(days=1)
+        assert calculate_age(dob, today=today) == 17
+
+    def test_17_years_old(self):
+        """A person who is 17 years old today is 17."""
+        today = date(2025, 6, 15)
+        dob = date(2008, 6, 15)
+        assert calculate_age(dob, today=today) == 17
+
+    def test_65_years_old(self):
+        """A person who is 65 is correctly calculated."""
+        today = date(2025, 6, 15)
+        dob = today.replace(year=today.year - 65)
+        assert calculate_age(dob, today=today) == 65
+
+    def test_newborn(self):
+        """A newborn is 0."""
+        today = date(2025, 6, 15)
+        dob = today
+        assert calculate_age(dob, today=today) == 0
+
+    def test_birthday_not_yet_this_year(self):
+        """Person born Dec 31, 2000 — on Jan 1, 2025 they are still 24."""
+        dob = date(2000, 12, 31)
+        assert calculate_age(dob, today=date(2025, 1, 1)) == 24
+
+    def test_birthday_today(self):
+        """Person born Dec 31, 2000 — on Dec 31, 2024 they turn 24."""
+        dob = date(2000, 12, 31)
+        assert calculate_age(dob, today=date(2024, 12, 31)) == 24
+
+
+class TestRegisterRequestDateValidation:
+    """Tests for the RegisterRequest date_of_birth field validator."""
+
+    @pytest.mark.parametrize(
+        "dob",
+        [
+            "2000-01-01",
+            "1990-12-31",
+            "2004-02-29",  # leap day
+        ],
+    )
+    def test_valid_dates(self, dob):
+        """Valid YYYY-MM-DD dates pass validation."""
+        from app.routers.auth import RegisterRequest
+
+        req = RegisterRequest(username="u", email="u@example.com", password="p", date_of_birth=dob)
+        assert req.date_of_birth == dob
+
+    @pytest.mark.parametrize(
+        "dob",
+        [
+            "01-01-2000",
+            "2000/01/01",
+            "2000-13-01",
+            "2000-00-10",
+            "not-a-date",
+            "",
+        ],
+    )
+    def test_invalid_dates_rejected(self, dob):
+        """Invalid dates are rejected by the validator."""
+        from app.routers.auth import RegisterRequest
+
+        with pytest.raises(ValueError):
+            RegisterRequest(username="u", email="u@example.com", password="p", date_of_birth=dob)

docs/planning/economy.md

@@ -0,0 +1,295 @@
+# Economy — Currency, Marketplace & Creator Payouts — Plan
+
+> **Status:** Planned
+> **Owner:** Platform team
+> **Feature ID:** `economy`
+> **Godot version:** 4.6.2 stable
+> **Backend:** FastAPI + SQLAlchemy (async) + PostgreSQL + Redis
+
+## 1. Overview
+
+This document breaks the **Economy** feature into user stories and right-sized
+implementation tasks. The feature delivers:
+
+- **Virtual currency ("Credits")** — a single, server-authoritative currency
+  with an immutable, append-only transaction ledger.
+- **Premium purchase** — buying Credits with real money through a pluggable
+  payment-provider hook.
+- **Marketplace** — user-generated content (UGC) listings where creators sell
+  items (assets, avatar items, experience passes) to players for Credits.
+- **Creator payouts** — accumulating creator earnings and paying them out to
+  external accounts through a pluggable payout-provider hook.
+- **Godot client** — wallet/transaction history, marketplace browse/buy/sell,
+  and creator payout screens.
+
+The economy is the monetization backbone of the platform. Because it moves
+virtual value between real people, correctness (no double-spend, no lost funds,
+no balance drift) and safety (fraud prevention, moderation, audit) are treated
+as **blocking requirements**, not add-ons.
+
+## 2. Why correctness is the differentiator
+
+The platform is a creator economy (players buy UGC from other players). The
+economy is the highest-risk surface after chat: a single arithmetic or
+concurrency bug can mint or destroy value and irreversibly erode trust.
+Correctness is therefore designed in from the start:
+
+- **One currency, integer units.** Credits are whole-number integers. There are
+  no floats, no rounding, and no client-computed totals.
+- **Append-only ledger.** Every balance change is a row in a `transactions`
+  table with a signed amount, a `balance_after` snapshot, a reference to the
+  event that caused it, and an **idempotency key** so retries cannot double
+  credit or double debit.
+- **Atomic, locked mutations.** Balance changes run in a single database
+  transaction with row locking (`SELECT ... FOR UPDATE`) so concurrent
+  purchases/payouts cannot race.
+- **Escrow hold.** Marketplace proceeds are held in `pending_escrow` for a
+  configurable window before becoming available to the seller, so fraudulent
+  or moderated sales can be reversed without clawing back paid-out funds.
+- **Server-authoritative fees.** The platform commission is computed
+  server-side from a configured rate; the client never supplies the fee or the
+  seller's net.
+
+## 3. Existing constraints (do not re-build)
+
+- **Auth:** JWT bearer tokens; `get_current_user` / `CurrentUser` dependency in
+  `app/dependencies.py`. All economy endpoints reuse this.
+- **DB:** async SQLAlchemy + Alembic; migration `0001_initial` is the head.
+  Existing tables: `users`, `sessions`, `worlds`, `assets`.
+- **Redis:** configured (`REDIS_URL`) but unused so far; adopted here for
+  idempotency short-caching and rate limiting.
+- **Models:** `User` (owner_id), `Asset` (owner_id, is_public, asset_type).
+  Marketplace items reference existing `assets` rows and/or avatar items.
+- **Content moderation:** `docs/architecture/content_moderation.md` defines
+  flag vocabulary, age gate, and moderation actions. Marketplace items and
+  listings must inherit and enforce these rules (see §7).
+- **Client:** Godot 4.6.2, minimal `main_menu.gd`; no economy UI yet.
+
+## 4. Key design decisions
+
+| Concern | Decision |
+|---|---|
+| Currency model | Single virtual currency **"Credits" (CR)**, integer units. One wallet row per user; no fractional amounts. |
+| Ledger | Append-only `transactions` table: signed `amount`, `balance_after`, `reference_type`/`reference_id`, unique `idempotency_key`. |
+| Concurrency | `SELECT ... FOR UPDATE` on the wallet row inside the mutation transaction; never read-modify-write from stale data. |
+| Payments | Pluggable `PaymentProvider` interface with a **no-op default** that simulates a confirmed payment for dev/testing (clearly flagged). Stripe/PayPal later. |
+| Marketplace items | `catalog_items` (what is sold) + `marketplace_listings` (a seller's offer with a price/status). One item can have multiple listings over time. |
+| Purchase flow | Atomic transaction: debit buyer → hold funds in escrow (`pending_escrow`) → grant item. Platform fee computed server-side. |
+| Escrow | Configurable hold window (default 72h) before `pending_escrow` becomes available seller earnings. Refunds during the window reverse the sale. |
+| Fees | Single configurable `MARKETPLACE_FEE_RATE` (default `0.30`). `seller_net = floor(price * (1 - fee_rate))`. |
+| Creator balance | `creator_balances` table: `available` (earned, payable), `pending` (inside an open payout request), `lifetime_earned`. Updated in the same transaction as the sale completion. |
+| Payouts | Pluggable `PayoutProvider.pay()` with a no-op default (simulated external ref). Minimum payout threshold, admin review for large payouts. |
+| Idempotency | Every money-moving request carries a client-generated `Idempotency-Key`; duplicate keys return the original result. |
+| Rate limiting | Redis token-bucket dependency reused from the social feature for purchase/listing/payout endpoints. |
+| Moderation | Listings enforce content flags + age gate; moderators can `delist`/`remove`; fraud/chargeback reversal is an audited admin action. |
+
+## 5. User stories
+
+### US-1 Currency & wallet
+As a player, I can see my Credit balance and transaction history, and the system
+credits/debits my wallet only through server-authoritative events.
+
+**Acceptance criteria**
+- Exactly one wallet per user, created lazily on first use.
+- Balance is always a non-negative integer; no operation can make it negative.
+- Every mutation appends an immutable ledger row with amount, resulting balance,
+  reference, and idempotency key.
+- Retrying a request with the same idempotency key does not double-apply.
+- `GET` endpoints expose current balance and paged transaction history.
+
+### US-2 Premium purchase (buy Credits)
+As a player, I can purchase Credits with real money and have them credited only
+after the payment is confirmed.
+
+**Acceptance criteria**
+- A purchase session is created through the payment provider (or the no-op
+  default) and is idempotent.
+- Credits are granted exactly once, only after a verified provider confirmation
+  (webhook/confirm endpoint), never on client claim.
+- Purchase amounts are bounded and server-defined; clients cannot pick arbitrary
+  prices.
+- Confirmation is idempotent and audited (provider reference recorded).
+
+### US-3 Marketplace listing (sell)
+As a creator, I can list a catalog item for sale at a Credit price and
+manage/remove my listings.
+
+**Acceptance criteria**
+- A listing references a valid `catalog_item` owned by the seller (or an
+  authorized seller).
+- Price is bounded (min/max) and set server-side; status transitions are
+  explicit (`active`, `sold`, `delisted`, `removed_by_moderation`).
+- Only the seller (or a moderator) can update/remove a listing.
+- Listings are searchable/filterable (item type, price range, owner).
+
+### US-4 Marketplace purchase (buy)
+As a player, I can buy a listed item. The purchase is atomic, holds funds in
+escrow, grants the item, and splits the payment between platform and seller.
+
+**Acceptance criteria**
+- A single transaction debits the buyer, holds funds in escrow, and grants the
+  item — no partial states on failure.
+- Platform fee and seller net are computed server-side from the configured rate.
+- After the escrow hold window, funds move from escrow to the seller's
+  available balance.
+- Refunds during the hold window reverse the sale and return funds to the buyer.
+- Concurrent purchases of a one-of-a-kind listing cannot both succeed.
+
+### US-5 Creator payouts
+As a creator, I can view my earned balance, request a payout, and track its
+status; admins can review and approve/reject payouts.
+
+**Acceptance criteria**
+- Available balance is derived only from completed (escrow-released) sales and
+  completed payouts; it never goes negative.
+- Payout requests are bounded (min threshold, max per period) and rate-limited.
+- Large payouts require admin review; all payout requests carry an audit trail
+  (requested by, reviewed by, provider reference, status).
+- The payout provider is called exactly once; idempotent on retry.
+
+### US-6 Godot client
+As a player, I can manage Credits, browse/buy/sell marketplace items, and manage
+payouts from the game UI.
+
+**Acceptance criteria**
+- An API client handles JWT auth, HTTP, and idempotency keys for all economy
+  calls.
+- Dedicated screens: wallet + transaction history, marketplace browse/buy,
+  sell-listing, and creator payout.
+- The client never computes balances, fees, or seller nets — it only displays
+  server responses.
+
+## 6. Task breakdown
+
+Right-sized to 1–3 files / one coherent piece of functionality each. Task IDs
+are sequential for dependency chaining.
+
+| # | Task | Story | Depends on |
+|---|------|-------|-----------|
+| 1 | Wallet & ledger models + Alembic migration (`wallets`, `transactions`) | US-1 | — |
+| 2 | Wallet service (atomic credit/debit, idempotency, locking) + wallet/transactions API | US-1 | 1 |
+| 3 | Premium purchase: `PaymentProvider` interface + purchase/confirm endpoints | US-2 | 1 |
+| 4 | Catalog item & listing models + migration (`catalog_items`, `marketplace_listings`, `creator_balances`) | US-3 | 1 |
+| 5 | Marketplace listing API (create/list/search/update/remove) | US-3 | 4 |
+| 6 | Marketplace purchase service + API (atomic escrow, fee split, item grant) | US-4 | 2, 4, 5 |
+| 7 | Creator payout request models + API (`payout_requests`) | US-5 | 2, 6 |
+| 8 | Payout admin review + `PayoutProvider` + audit | US-5 | 7 |
+| 9 | Marketplace moderation + content-flag/age-gate enforcement | cross-cutting | 5, 6 |
+| 10 | Godot economy API client (auth + HTTP + idempotency) | US-6 | 2 |
+| 11 | Godot wallet & transaction history UI | US-6 | 10 |
+| 12 | Godot marketplace browse/buy UI | US-6 | 6, 10 |
+| 13 | Godot selling & payout UI | US-6 | 5, 7, 10 |
+
+## 7. Phasing
+
+- **Phase 1 (currency + payments):** tasks 1–3. The foundation — ledger and
+  money movement must be rock-solid before anything spends Credits.
+- **Phase 2 (marketplace):** tasks 4–6. Listing and atomic purchase with escrow.
+- **Phase 3 (payouts):** tasks 7–8. Turn released escrow into creator payouts.
+- **Phase 4 (moderation):** task 9. Lock down the marketplace against mature
+  content and abuse.
+- **Phase 5 (client):** tasks 10–13, each landing after its backend dependency.
+
+## 8. Data model sketch
+
+```text
+wallets
+  id                bigint PK
+  user_id           int UNIQUE FK -> users.id
+  balance           bigint NOT NULL DEFAULT 0  CHECK (balance >= 0)
+  created_at        timestamptz
+  updated_at        timestamptz
+
+transactions        (append-only ledger)
+  id                bigint PK
+  wallet_id         bigint FK -> wallets.id
+  type              enum(credit_purchase, marketplace_purchase,
+                        marketplace_sale, escrow_release, payout,
+                        refund, admin_adjustment)
+  amount            bigint NOT NULL            (signed)
+  balance_after     bigint NOT NULL
+  reference_type    text                        (e.g. "purchase", "sale", "payout_request")
+  reference_id      text
+  idempotency_key   text UNIQUE
+  metadata_json     jsonb
+  created_at        timestamptz
+
+catalog_items
+  id                bigint PK
+  owner_id          int FK -> users.id
+  asset_id          int FK -> assets.id (nullable; null for non-asset virtual items)
+  item_type         enum(asset, avatar_item, experience_pass)
+  name              text
+  description       text
+  metadata_json     jsonb
+  created_at        timestamptz
+
+marketplace_listings
+  id                bigint PK
+  catalog_item_id   bigint FK -> catalog_items.id
+  seller_id         int FK -> users.id
+  price             bigint NOT NULL CHECK (price > 0)
+  status            enum(active, sold, delisted, removed_by_moderation)
+  created_at        timestamptz
+  updated_at        timestamptz
+
+purchases
+  id                bigint PK
+  listing_id        bigint FK -> marketplace_listings.id
+  buyer_id          int FK -> users.id
+  seller_id         int FK -> users.id
+  price             bigint NOT NULL
+  platform_fee      bigint NOT NULL
+  seller_net        bigint NOT NULL
+  status            enum(pending_escrow, completed, refunded, reversed)
+  escrow_hold_until timestamptz
+  created_at        timestamptz
+
+creator_balances
+  id                bigint PK
+  user_id           int UNIQUE FK -> users.id
+  available         bigint NOT NULL DEFAULT 0
+  pending           bigint NOT NULL DEFAULT 0
+  lifetime_earned   bigint NOT NULL DEFAULT 0
+  updated_at        timestamptz
+
+payout_requests
+  id                bigint PK
+  creator_id        int FK -> users.id
+  amount            bigint NOT NULL CHECK (amount > 0)
+  status            enum(pending, approved, paid, rejected)
+  external_ref      text
+  provider_ref      text
+  requested_by      int FK -> users.id
+  reviewed_by       int FK -> users.id (nullable)
+  reviewed_at       timestamptz
+  created_at        timestamptz
+```
+
+## 9. Security, anti-fraud & audit
+
+- **Server-authoritative balances/fees:** clients never compute totals; amounts
+  are validated server-side against bounds and the current listing.
+- **Row locking:** wallet and creator-balance mutations use `SELECT ... FOR
+  UPDATE` within one transaction.
+- **Idempotency:** every money-moving endpoint requires an `Idempotency-Key`;
+  duplicate keys return the stored original outcome.
+- **Rate limiting:** purchase, listing, and payout endpoints are token-bucket
+  rate-limited per user.
+- **Escrow & reversibility:** funds are not payable until the hold window
+  elapses; chargebacks/refunds reverse before release.
+- **Moderation:** listings carry the item's effective content flags; mature
+  items require age verification (per `content_moderation.md`); moderators can
+  `delist`/`remove` and trigger audited reversals.
+- **Audit:** the ledger plus `payout_requests` review fields form an append-only
+  audit trail for every movement of value.
+
+## 10. Out of scope for this feature
+
+- Real Stripe/PayPal/KYC integrations (provider interfaces leave the hooks; the
+  defaults are deterministic no-ops).
+- Subscriptions, recurring billing, or premium memberships.
+- Gift cards, promotional codes, or user-to-user Credit transfers.
+- Partial refunds, chargeback disputes, and seller tax/VAT handling.
+- In-world vending machines / scripted economy triggers (future, built on this
+  ledger via the scripting sandbox).

scenes/main.tscn

@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3 uid="uid://main_scene"]
+
+[ext_resource type="Script" path="res://scripts/chunk_stream_manager.gd" id="1_chunk_stream"]
+
+[node name="Main" type="Node3D"]
+script = ExtResource("1_chunk_stream")

scripts/chunk.gd

@@ -0,0 +1,105 @@
+class_name Chunk
+extends Node3D
+## A single world chunk. Holds the chunk coordinate, bounds, and the
+## visual/gameplay content for that region of the world.
+##
+## Chunks are the atomic unit of world geometry, gameplay objects, and
+## persistence (see docs/architecture/world.md). The server loads and saves
+## whole chunks; clients stream the chunks around them.
+
+## Default chunk dimensions in world units (tiles). Matches the constants in
+## docs/architecture/world.md section 2.2.
+const CHUNK_SIZE_X: int = 32
+const CHUNK_SIZE_Y: int = 32
+const CHUNK_SIZE_Z: int = 1
+
+## World-space origin of chunk coordinate (0,0).
+const CHUNK_ORIGIN := Vector3(0.0, 0.0, 0.0)
+
+## Chunk coordinate (cx, cy, cz) in chunk space.
+var coord := Vector3i.ZERO
+
+## The canonical chunk key: "{world_id}:{room_id}:{cx}:{cy}:{cz}".
+var key: String = ""
+
+## World and room identifiers this chunk belongs to.
+var world_id: String = ""
+var room_id: String = ""
+
+## Format version of the chunk payload (currently 1).
+var format_version: int = 1
+
+## Revision counter, incremented on every write. Used for optimistic
+## concurrency and change detection.
+var revision: int = 0
+
+## Whether this chunk has been modified in memory but not yet flushed.
+var dirty: bool = false
+
+## Container for static objects (props, geometry) in this chunk.
+var objects: Array[Node3D] = []
+
+## Container for dynamic object templates (spawnable entities).
+var dynamic_templates: Array[Node3D] = []
+
+## The world-space bounding box of this chunk.
+var bounds: AABB
+
+
+func _init(p_coord: Vector3i = Vector3i.ZERO, p_world_id: String = "", p_room_id: String = "") -> void:
+	coord = p_coord
+	world_id = p_world_id
+	room_id = p_room_id
+	key = build_key(world_id, room_id, coord)
+	bounds = compute_bounds(coord)
+
+
+## Build the canonical chunk key from its components.
+static func build_key(p_world_id: String, p_room_id: String, p_coord: Vector3i) -> String:
+	return "%s:%s:%d:%d:%d" % [p_world_id, p_room_id, p_coord.x, p_coord.y, p_coord.z]
+
+
+## Compute the world-space bounding box for a chunk coordinate.
+static func compute_bounds(p_coord: Vector3i) -> AABB:
+	var min_pos := Vector3(
+		CHUNK_ORIGIN.x + p_coord.x * CHUNK_SIZE_X,
+		CHUNK_ORIGIN.y + p_coord.y * CHUNK_SIZE_Y,
+		CHUNK_ORIGIN.z + p_coord.z * CHUNK_SIZE_Z
+	)
+	return AABB(min_pos, Vector3(CHUNK_SIZE_X, CHUNK_SIZE_Y, CHUNK_SIZE_Z))
+
+
+## Compute the chunk coordinate that contains a world-space position.
+static func coord_for_position(p_pos: Vector3) -> Vector3i:
+	return Vector3i(
+		int(floor((p_pos.x - CHUNK_ORIGIN.x) / CHUNK_SIZE_X)),
+		int(floor((p_pos.y - CHUNK_ORIGIN.y) / CHUNK_SIZE_Y)),
+		int(floor((p_pos.z - CHUNK_ORIGIN.z) / CHUNK_SIZE_Z))
+	)
+
+
+## Add a static object to this chunk.
+func add_object(p_object: Node3D) -> void:
+	objects.append(p_object)
+	add_child(p_object)
+
+
+## Add a dynamic object template to this chunk.
+func add_dynamic_template(p_template: Node3D) -> void:
+	dynamic_templates.append(p_template)
+	add_child(p_template)
+
+
+## Remove all objects from this chunk.
+func clear_objects() -> void:
+	for obj in objects:
+		if is_instance_valid(obj):
+			obj.queue_free()
+	objects.clear()
+	dynamic_templates.clear()
+
+
+## Mark this chunk as dirty (modified but not yet persisted).
+func mark_dirty() -> void:
+	dirty = true
+	revision += 1

scripts/chunk.gd.uid

@@ -0,0 +1 @@
+uid://dc6j7kqjitc6g

scripts/chunk_data_decoder.gd

@@ -0,0 +1,667 @@
+class_name ChunkDataDecoder
+extends RefCounted
+## Decodes chunk binary payloads (and JSON) into logical chunk data.
+##
+## Implements the binary format spec from docs/architecture/world.md §3.6.
+## Both the Godot client and Python backend use this class to ensure
+## identical encoding/decoding behavior.
+##
+## ## Binary Format Overview
+##
+## ```
+## Header (48 bytes):
+##   [0:4]   magic "AGPC"
+##   [4:6]   version (uint16 LE)
+##   [6:8]   header_len (uint16 LE)
+##   [8:12]  flags (uint32 LE)
+##   [12:16] payload_len (uint32 LE)
+##   [16:48] checksum (SHA-256 hex, 32 bytes)
+##
+## Payload Body (sections):
+##   [section_id:1][section_len:4][data:section_len]
+## ```
+
+
+## Content flags parsed from a chunk.
+class ContentFlags:
+	## Severity levels: 0=none, 1=mild, 2=moderate, 3=severe
+	var violence: int = 0
+	var sexual: int = 0
+	var language: int = 0
+	var substance: int = 0
+	var gambling: int = 0
+	var horror: int = 0
+	var hate: int = 0
+	var custom: int = 0
+	var mature: bool = false
+	var sources: Array[String] = []
+
+	func is_mature() -> bool:
+		return mature
+
+	func has_severe_content() -> bool:
+		return (violence >= 3 or sexual >= 3 or language >= 3 or
+		        substance >= 3 or gambling >= 3 or horror >= 3 or
+		        hate >= 3 or custom >= 3)
+
+	func get_max_severity() -> int:
+		return maxi(
+			violence, maxi(sexual, maxi(language, maxi(substance,
+			maxi(gambling, maxi(horror, maxi(hate, custom)))))))
+
+	func to_dict() -> Dictionary:
+		return {
+			"categories": {
+				"violence": violence,
+				"sexual": sexual,
+				"language": language,
+				"substance": substance,
+				"gambling": gambling,
+				"horror": horror,
+				"hate": hate,
+				"custom": custom,
+			},
+			"mature": mature,
+			"sources": sources,
+		}
+
+	func from_dict(d: Dictionary) -> void:
+		if d.has("categories"):
+			violence = d["categories"].get("violence", 0)
+			sexual = d["categories"].get("sexual", 0)
+			language = d["categories"].get("language", 0)
+			substance = d["categories"].get("substance", 0)
+			gambling = d["categories"].get("gambling", 0)
+			horror = d["categories"].get("horror", 0)
+			hate = d["categories"].get("hate", 0)
+			custom = d["categories"].get("custom", 0)
+		mature = d.get("mature", false)
+		sources = d.get("sources", [])
+
+
+## A tile layer definition (palette + dense tile indices).
+class TileLayerData:
+	var name: String = ""
+	var layer_id: int = 0
+	var width: int = 0
+	var height: int = 0
+	var depth: int = 1
+	var palette: Array[TileDef] = []
+	var tiles: PackedInt32Array = PackedInt32Array()
+
+	func tile_count() -> int:
+		return width * height * depth
+
+	func get_tile(x: int, y: int, z: int = 0) -> int:
+		if x < 0 or x >= width or y < 0 or y >= height or z < 0 or z >= depth:
+			return 0  # Out of bounds returns empty tile
+		var idx := (z * height + y) * width + x
+		if idx < tiles.size():
+			return tiles[idx]
+		return 0
+
+	func get_tile_def(tile_id: int) -> TileDef:
+		for def in palette:
+			if def.id == tile_id:
+				return def
+		return null
+
+
+## A world object parsed from chunk data.
+class WorldObjectData:
+	var id: String = ""
+	var type: String = ""
+	var asset_id: String = ""
+	var position: Vector3 = Vector3.ZERO
+	var rotation: Vector4 = Vector4(0, 0, 0, 1)
+	var scale: Vector3 = Vector3.ONE
+	var properties: Dictionary = {}
+	var dynamic: bool = false
+	var flags: ContentFlags = ContentFlags.new()
+
+
+## The complete decoded chunk payload.
+class ChunkPayload:
+	var version: int = 1
+	var key: String = ""
+	var world_id: String = ""
+	var room_id: String = ""
+	var coord: Vector3i = Vector3i.ZERO
+	var bounds: AABB = AABB()
+	var tile_layers: Array[TileLayerData] = []
+	var objects: Array[WorldObjectData] = []
+	var flags: ContentFlags = ContentFlags.new()
+	var created_at: int = 0  # Unix timestamp
+	var updated_at: int = 0  # Unix timestamp
+	var revision: int = 0
+	var author: String = ""
+	var checksum: String = ""
+
+
+# ───────────────── Binary Decoding ─────────────────
+
+static var MAGIC := PackedByteArray([0x41, 0x47, 0x50, 0x43])  # "AGPC"
+const HEADER_SIZE: int = 48
+const SECTION_META: int = 0x01
+const SECTION_TILE: int = 0x02
+const SECTION_OBJECT: int = 0x03
+const SECTION_FLAGS: int = 0x04
+const SECTION_REVISION_META: int = 0x05
+
+
+## Decode a binary chunk payload into a ChunkPayload.
+## Returns null if the data is invalid or version is unsupported.
+static func decode_binary(data: PackedByteArray) -> ChunkPayload:
+	if data.size() < HEADER_SIZE:
+		push_error("ChunkDataDecoder: Data too short for header (%d bytes)" % data.size())
+		return null
+
+	# Verify magic
+	var magic := PackedByteArray(data.slice(0, 4))
+	if magic != MAGIC:
+		push_error("ChunkDataDecoder: Invalid magic bytes")
+		return null
+
+	# Read header fields
+	var version := _read_uint16(data, 4)
+	if version != 1:
+		push_error("ChunkDataDecoder: Unsupported chunk version %d" % version)
+		return null
+
+	var header_len := _read_uint16(data, 6)
+	var flags := _read_uint32(data, 8)
+	var payload_len := _read_uint32(data, 12)
+	var checksum := _read_hex_string(data, 16, 32)
+
+	# Verify payload length
+	if data.size() < HEADER_SIZE + payload_len:
+		push_error("ChunkDataDecoder: Payload too short")
+		return null
+
+	var payload := data.slice(HEADER_SIZE, HEADER_SIZE + payload_len)
+
+	# Verify checksum
+	var computed_checksum := _sha256_hex(payload)
+	if computed_checksum != checksum:
+		push_error("ChunkDataDecoder: Checksum mismatch")
+		# Continue anyway for resilience
+
+	var result := ChunkPayload.new()
+	result.version = version
+	result.checksum = checksum
+
+	# Parse sections
+	var offset := 0
+	while offset < payload.size():
+		if offset + 5 > payload.size():
+			break
+
+		var section_id := payload[offset]
+		var section_len := _read_uint32(payload, offset + 1)
+
+		if offset + 5 + section_len > payload.size():
+			break
+
+		var section_data := payload.slice(offset + 5, offset + 5 + section_len)
+
+		match section_id:
+			SECTION_META:
+				_parse_metadata_section(section_data, result)
+			SECTION_TILE:
+				_parse_tile_section(section_data, result)
+			SECTION_OBJECT:
+				_parse_object_section(section_data, result)
+			SECTION_FLAGS:
+				_parse_flags_section(section_data, result.flags)
+			SECTION_REVISION_META:
+				_parse_revision_meta_section(section_data, result)
+
+		offset += 5 + section_len
+
+	return result
+
+
+## Encode a ChunkPayload into binary format.
+static func encode_binary(payload: ChunkPayload) -> PackedByteArray:
+	var sections := PackedByteArray()
+
+	# Build metadata section
+	sections.append_array(_build_metadata_section(payload))
+	# Build tile sections
+	for layer in payload.tile_layers:
+		sections.append_array(_build_tile_section(layer))
+	# Build object sections
+	for obj in payload.objects:
+		sections.append_array(_build_object_section(obj))
+	# Build flags section
+	sections.append_array(_build_flags_section(payload.flags))
+	# Build revision meta section
+	sections.append_array(_build_revision_meta_section(payload))
+
+	var payload_bytes := PackedByteArray(sections)
+	var checksum := _sha256_hex(payload_bytes)
+
+	# Build header
+	var header := PackedByteArray()
+	header.append_array(MAGIC)
+	header.append_array(_write_uint16(1))  # version
+	header.append_array(_write_uint16(0))  # header_len (after this field)
+	header.append_array(_write_uint32(0))  # flags
+	header.append_array(_write_uint32(payload_bytes.size()))
+	header.append_array(_hex_to_bytes(checksum))
+
+	return header + payload_bytes
+
+
+# ───────────────── Section Parsers ─────────────────
+
+static func _parse_metadata_section(data: PackedByteArray, result: ChunkPayload) -> void:
+	var offset := 0
+
+	# world_id (length-prefixed string)
+	var world_id_len := _read_uint16(data, offset)
+	offset += 2
+	result.world_id = data.slice(offset, offset + world_id_len).get_string_from_utf8()
+	offset += world_id_len
+
+	# room_id (length-prefixed string)
+	var room_id_len := _read_uint16(data, offset)
+	offset += 2
+	result.room_id = data.slice(offset, offset + room_id_len).get_string_from_utf8()
+	offset += room_id_len
+
+	# coord (3 × int32)
+	result.coord = Vector3i(
+		_read_int32(data, offset),
+		_read_int32(data, offset + 4),
+		_read_int32(data, offset + 8)
+	)
+	offset += 12
+
+	# bounds (6 × float32)
+	var min_pos := Vector3(
+		_read_float32(data, offset),
+		_read_float32(data, offset + 4),
+		_read_float32(data, offset + 8)
+	)
+	var max_pos := Vector3(
+		_read_float32(data, offset + 12),
+		_read_float32(data, offset + 16),
+		_read_float32(data, offset + 20)
+	)
+	result.bounds = AABB(min_pos, max_pos - min_pos)
+
+
+static func _parse_tile_section(data: PackedByteArray, result: ChunkPayload) -> void:
+	var layer := TileLayerData.new()
+	var offset := 0
+
+	# name (length-prefixed string)
+	var name_len := _read_uint16(data, offset)
+	offset += 2
+	layer.name = data.slice(offset, offset + name_len).get_string_from_utf8()
+	offset += name_len
+
+	# layer_id (uint16)
+	layer.layer_id = _read_uint16(data, offset)
+	offset += 2
+
+	# dimensions (3 × uint16)
+	layer.width = _read_uint16(data, offset)
+	offset += 2
+	layer.height = _read_uint16(data, offset)
+	offset += 2
+	layer.depth = _read_uint16(data, offset)
+	offset += 2
+
+	# palette
+	var palette_count := _read_uint16(data, offset)
+	offset += 2
+	for _i in range(palette_count):
+		var tile_def := TileDef.new()
+		tile_def.id = _read_uint16(data, offset)
+		offset += 2
+
+		var asset_id_len := _read_uint16(data, offset)
+		offset += 2
+		tile_def.asset_id = data.slice(offset, offset + asset_id_len).get_string_from_utf8()
+		offset += asset_id_len
+
+		tile_def.solid = data[offset] != 0
+		offset += 1
+
+		tile_def.flags = _read_uint32(data, offset)
+		offset += 4
+
+		tile_def.variants = data[offset]
+		offset += 1
+
+		layer.palette.append(tile_def)
+
+	# tiles
+	var tile_count := _read_uint32(data, offset)
+	offset += 4
+	for i in range(tile_count):
+		layer.tiles.append(_read_uint16(data, offset))
+		offset += 2
+
+	result.tile_layers.append(layer)
+
+
+static func _parse_object_section(data: PackedByteArray, result: ChunkPayload) -> void:
+	var obj := WorldObjectData.new()
+	var offset := 0
+
+	# id (length-prefixed string)
+	var id_len := _read_uint16(data, offset)
+	offset += 2
+	obj.id = data.slice(offset, offset + id_len).get_string_from_utf8()
+	offset += id_len
+
+	# type (length-prefixed string)
+	var type_len := _read_uint16(data, offset)
+	offset += 2
+	obj.type = data.slice(offset, offset + type_len).get_string_from_utf8()
+	offset += type_len
+
+	# asset_id (length-prefixed string)
+	var asset_id_len := _read_uint16(data, offset)
+	offset += 2
+	obj.asset_id = data.slice(offset, offset + asset_id_len).get_string_from_utf8()
+	offset += asset_id_len
+
+	# position (3 × float32)
+	obj.position = Vector3(
+		_read_float32(data, offset),
+		_read_float32(data, offset + 4),
+		_read_float32(data, offset + 8)
+	)
+	offset += 12
+
+	# rotation (4 × float32)
+	obj.rotation = Vector4(
+		_read_float32(data, offset),
+		_read_float32(data, offset + 4),
+		_read_float32(data, offset + 8),
+		_read_float32(data, offset + 12)
+	)
+	offset += 16
+
+	# scale (3 × float32)
+	obj.scale = Vector3(
+		_read_float32(data, offset),
+		_read_float32(data, offset + 4),
+		_read_float32(data, offset + 8)
+	)
+	offset += 12
+
+	# dynamic (uint8)
+	obj.dynamic = data[offset] != 0
+	offset += 1
+
+	# properties (length-prefixed JSON string)
+	var props_len := _read_uint16(data, offset)
+	offset += 2
+	var props_str := data.slice(offset, offset + props_len).get_string_from_utf8()
+	offset += props_len
+	obj.properties = JSON.parse_string(props_str) or {}
+
+	# flags (ContentFlags)
+	obj.flags.violence = data[offset]
+	offset += 1
+	obj.flags.sexual = data[offset]
+	offset += 1
+	obj.flags.language = data[offset]
+	offset += 1
+	obj.flags.substance = data[offset]
+	offset += 1
+	obj.flags.gambling = data[offset]
+	offset += 1
+	obj.flags.horror = data[offset]
+	offset += 1
+	obj.flags.hate = data[offset]
+	offset += 1
+	obj.flags.custom = data[offset]
+	offset += 1
+	obj.flags.mature = data[offset] != 0
+	offset += 1
+
+	var source_count := _read_uint16(data, offset)
+	offset += 2
+	for _i in range(source_count):
+		var src_len := _read_uint16(data, offset)
+		offset += 2
+		obj.flags.sources.append(data.slice(offset, offset + src_len).get_string_from_utf8())
+		offset += src_len
+
+	result.objects.append(obj)
+
+
+static func _parse_flags_section(data: PackedByteArray, flags: ContentFlags) -> void:
+	flags.violence = data[0]
+	flags.sexual = data[1]
+	flags.language = data[2]
+	flags.substance = data[3]
+	flags.gambling = data[4]
+	flags.horror = data[5]
+	flags.hate = data[6]
+	flags.custom = data[7]
+	flags.mature = data[8] != 0
+
+	var offset := 9
+	var source_count := _read_uint16(data, offset)
+	offset += 2
+	for _i in range(source_count):
+		var src_len := _read_uint16(data, offset)
+		offset += 2
+		flags.sources.append(data.slice(offset, offset + src_len).get_string_from_utf8())
+		offset += src_len
+
+
+static func _parse_revision_meta_section(data: PackedByteArray, result: ChunkPayload) -> void:
+	var offset := 0
+	# created_at (int64 unix)
+	result.created_at = _read_int64(data, offset)
+	offset += 8
+	# updated_at (int64 unix)
+	result.updated_at = _read_int64(data, offset)
+	offset += 8
+	# revision (uint32)
+	result.revision = _read_uint32(data, offset)
+	offset += 4
+	# author (length-prefixed string)
+	var author_len := _read_uint16(data, offset)
+	offset += 2
+	result.author = data.slice(offset, offset + author_len).get_string_from_utf8()
+
+
+# ───────────────── Section Builders ─────────────────
+
+static func _build_metadata_section(payload: ChunkPayload) -> PackedByteArray:
+	var data := PackedByteArray()
+	data.append_array(_write_string(payload.world_id))
+	data.append_array(_write_string(payload.room_id))
+	data.append_array(_write_int32(payload.coord.x))
+	data.append_array(_write_int32(payload.coord.y))
+	data.append_array(_write_int32(payload.coord.z))
+	data.append_array(_write_float32(payload.bounds.position.x))
+	data.append_array(_write_float32(payload.bounds.position.y))
+	data.append_array(_write_float32(payload.bounds.position.z))
+	data.append_array(_write_float32(payload.bounds.size.x))
+	data.append_array(_write_float32(payload.bounds.size.y))
+	data.append_array(_write_float32(payload.bounds.size.z))
+	return data
+
+
+static func _build_tile_section(layer: TileLayerData) -> PackedByteArray:
+	var data := PackedByteArray()
+	data.append_array(_write_string(layer.name))
+	data.append_array(_write_uint16(layer.layer_id))
+	data.append_array(_write_uint16(layer.width))
+	data.append_array(_write_uint16(layer.height))
+	data.append_array(_write_uint16(layer.depth))
+	data.append_array(_write_uint16(layer.palette.size()))
+
+	for tile_def in layer.palette:
+		data.append_array(_write_uint16(tile_def.id))
+		data.append_array(_write_string(tile_def.asset_id))
+		data.append(tile_def.solid as int)
+		data.append_array(_write_uint32(tile_def.flags))
+		data.append(tile_def.variants)
+
+	data.append_array(_write_uint32(layer.tiles.size()))
+	for tile_id in layer.tiles:
+		data.append_array(_write_uint16(tile_id))
+
+	return _wrap_section(data, SECTION_TILE)
+
+
+static func _build_object_section(obj: WorldObjectData) -> PackedByteArray:
+	var data := PackedByteArray()
+	data.append_array(_write_string(obj.id))
+	data.append_array(_write_string(obj.type))
+	data.append_array(_write_string(obj.asset_id))
+	data.append_array(_write_float32(obj.position.x))
+	data.append_array(_write_float32(obj.position.y))
+	data.append_array(_write_float32(obj.position.z))
+	data.append_array(_write_float32(obj.rotation.x))
+	data.append_array(_write_float32(obj.rotation.y))
+	data.append_array(_write_float32(obj.rotation.z))
+	data.append_array(_write_float32(obj.rotation.w))
+	data.append_array(_write_float32(obj.scale.x))
+	data.append_array(_write_float32(obj.scale.y))
+	data.append_array(_write_float32(obj.scale.z))
+	data.append(obj.dynamic as int)
+
+	var props_json := JSON.stringify(obj.properties, "  ")
+	data.append_array(_write_string(props_json))
+
+	data.append(obj.flags.violence)
+	data.append(obj.flags.sexual)
+	data.append(obj.flags.language)
+	data.append(obj.flags.substance)
+	data.append(obj.flags.gambling)
+	data.append(obj.flags.horror)
+	data.append(obj.flags.hate)
+	data.append(obj.flags.custom)
+	data.append(obj.flags.mature as int)
+	data.append_array(_write_uint16(obj.flags.sources.size()))
+	for src in obj.flags.sources:
+		data.append_array(_write_string(src))
+
+	return _wrap_section(data, SECTION_OBJECT)
+
+
+static func _build_flags_section(flags: ContentFlags) -> PackedByteArray:
+	var data := PackedByteArray()
+	data.append(flags.violence)
+	data.append(flags.sexual)
+	data.append(flags.language)
+	data.append(flags.substance)
+	data.append(flags.gambling)
+	data.append(flags.horror)
+	data.append(flags.hate)
+	data.append(flags.custom)
+	data.append(flags.mature as int)
+	data.append_array(_write_uint16(flags.sources.size()))
+	for src in flags.sources:
+		data.append_array(_write_string(src))
+	return _wrap_section(data, SECTION_FLAGS)
+
+
+static func _build_revision_meta_section(payload: ChunkPayload) -> PackedByteArray:
+	var data := PackedByteArray()
+	data.append_array(_write_int64(payload.created_at))
+	data.append_array(_write_int64(payload.updated_at))
+	data.append_array(_write_uint32(payload.revision))
+	data.append_array(_write_string(payload.author))
+	return _wrap_section(data, SECTION_REVISION_META)
+
+
+static func _wrap_section(data: PackedByteArray, section_id: int) -> PackedByteArray:
+	var wrapped := PackedByteArray()
+	wrapped.append(section_id)
+	wrapped.append_array(_write_uint32(data.size()))
+	wrapped.append_array(data)
+	return wrapped
+
+
+# ───────────────── Binary Helpers ─────────────────
+
+static func _read_uint16(data: PackedByteArray, offset: int) -> int:
+	return data[offset] | (data[offset + 1] << 8)
+
+static func _read_uint32(data: PackedByteArray, offset: int) -> int:
+	return (data[offset] | (data[offset + 1] << 8) |
+	        (data[offset + 2] << 16) | (data[offset + 3] << 24))
+
+static func _read_int32(data: PackedByteArray, offset: int) -> int:
+	var val := _read_uint32(data, offset)
+	if val >= 0x80000000:
+		return val - 0x100000000
+	return val
+
+static func _read_int64(data: PackedByteArray, offset: int) -> int:
+	var lo := _read_uint32(data, offset)
+	var hi := _read_uint32(data, offset + 4)
+	return hi * 0x100000000 + lo
+
+static func _read_float32(data: PackedByteArray, offset: int) -> float:
+	var bits := _read_uint32(data, offset)
+	return bits as float  # GDScript float is 64-bit; bits repr works for IEEE 754
+
+static func _read_hex_string(data: PackedByteArray, offset: int, length: int) -> String:
+	var hex_chars := "0123456789abcdef"
+	var result := ""
+	for i in range(length):
+		var byte_val := data[offset + i]
+		result += hex_chars[byte_val >> 4]
+		result += hex_chars[byte_val & 0x0F]
+	return result
+
+
+static func _write_uint16(val: int) -> PackedByteArray:
+	return PackedByteArray([(val & 0xFF), (val >> 8) & 0xFF])
+
+static func _write_uint32(val: int) -> PackedByteArray:
+	return PackedByteArray([
+		val & 0xFF, (val >> 8) & 0xFF, (val >> 16) & 0xFF, (val >> 24) & 0xFF
+	])
+
+static func _write_int32(val: int) -> PackedByteArray:
+	return _write_uint32(val)
+
+static func _write_int64(val: int) -> PackedByteArray:
+	var lo := val & 0xFFFFFFFF
+	var hi := (val >> 32) & 0xFFFFFFFF
+	return _write_uint32(lo) + _write_uint32(hi)
+
+static func _write_float32(val: float) -> PackedByteArray:
+	var bits := val as int
+	return _write_uint32(bits)
+
+static func _write_string(s: String) -> PackedByteArray:
+	var bytes := s.to_utf8_buffer()
+	return _write_uint16(bytes.size()) + bytes
+
+static func _hex_to_bytes(hex_str: String) -> PackedByteArray:
+	var result := PackedByteArray()
+	for i in range(0, hex_str.length(), 2):
+		var byte_val := ("0x" + hex_str.substr(i, 2)).hex_to_int()
+		result.append(byte_val)
+	return result
+
+
+# ───────────────── SHA-256 ─────────────────
+
+static func _sha256_hex(data: PackedByteArray) -> String:
+	var ctx := HashingContext.new()
+	ctx.start(HashingContext.HASH_SHA256)
+	ctx.update(data)
+	var hash := ctx.finish()
+	var hex_chars := "0123456789abcdef"
+	var result := ""
+	for byte_val in hash:
+		result += hex_chars[(byte_val >> 4) & 0x0F]
+		result += hex_chars[byte_val & 0x0F]
+	return result

scripts/chunk_data_decoder.gd.uid

@@ -0,0 +1 @@
+uid://bv445xrd6f5tk

scripts/chunk_scene.gd

@@ -0,0 +1,170 @@
+class_name ChunkScene
+extends Node3D
+## A visual representation of a single loaded world chunk.
+##
+## This node is instantiated by [ChunkStreamManager] when a chunk is loaded.
+## It holds the tile layers, world objects, and metadata for one chunk of the
+## world. The scene is responsible for rendering the chunk's visual content
+## and exposing its gameplay objects to the rest of the game.
+##
+## ## Structure
+##
+## ```
+## ChunkScene (Node3D)
+##  ├── TileLayer (Node3D)  # one per tile layer (ground, walls, decor, ...)
+##  ├── StaticObject (Node3D)  # props, geometry, interactables
+##  └── DynamicObject (Node3D)  # spawnable entities (templates)
+## ```
+##
+## ## Lifecycle
+##
+## 1. [ChunkStreamManager] requests chunk data from the server.
+## 2. Server responds with binary payload.
+## 3. [ChunkStreamManager] decodes the payload and creates a [ChunkScene].
+## 4. [ChunkScene] populates itself with tile layers and objects.
+## 5. When the player moves out of range, [ChunkStreamManager] calls
+##    [method ChunkScene.queue_free] to unload it.
+
+## The chunk coordinate this scene represents.
+var coord: Vector3i = Vector3i.ZERO
+
+## The canonical chunk key.
+var key: String = ""
+
+## World-space bounding box of this chunk.
+var bounds: AABB = AABB()
+
+## Format version of the chunk data.
+var format_version: int = 1
+
+## Revision counter from the server.
+var revision: int = 0
+
+## List of tile layers in this chunk.
+var tile_layers: Array[TileLayer] = []
+
+## List of world objects (static + dynamic) in this chunk.
+var world_objects: Array[WorldObject] = []
+
+## Content moderation flags for this chunk.
+var content_flags: ChunkDataDecoder.ContentFlags = ChunkDataDecoder.ContentFlags.new()
+
+## Whether this chunk has been modified locally (not yet synced to server).
+var is_dirty: bool = false
+
+
+func _ready() -> void:
+	# Position this chunk scene at its world-space origin
+	global_position = bounds.position
+	# Set up collision shape for the chunk bounds
+	_setup_collision()
+
+
+func _setup_collision() -> void:
+	# Add a collision shape for the chunk's bounding box
+	var collision := CollisionShape3D.new()
+	var shape := BoxShape3D.new()
+	shape.size = bounds.size
+	collision.shape = shape
+	collision.name = "ChunkBounds"
+	add_child(collision)
+
+
+## Add a tile layer to this chunk scene.
+func add_tile_layer(layer: TileLayer) -> void:
+	tile_layers.append(layer)
+	var layer_node := TileLayerNode.new()
+	layer_node.tile_layer = layer
+	layer_node.chunk_coord = coord
+	add_child(layer_node)
+
+
+## Add a world object to this chunk scene.
+func add_object(obj: WorldObject) -> void:
+	world_objects.append(obj)
+	if obj.is_dynamic:
+		_add_dynamic_object(obj)
+	else:
+		_add_static_object(obj)
+
+
+func _add_static_object(obj: WorldObject) -> void:
+	var static_obj := StaticObjectNode.new()
+	static_obj.world_object = obj
+	static_obj.position = obj.position
+	static_obj.quaternion = Quaternion(obj.rotation.x, obj.rotation.y, obj.rotation.z, obj.rotation.w)
+	static_obj.scale = obj.scale
+	static_obj.name = "static_%s" % obj.id
+	add_child(static_obj)
+
+
+func _add_dynamic_object(obj: WorldObject) -> void:
+	var dynamic_obj := DynamicObjectNode.new()
+	dynamic_obj.world_object = obj
+	dynamic_obj.position = obj.position
+	dynamic_obj.quaternion = Quaternion(obj.rotation.x, obj.rotation.y, obj.rotation.z, obj.rotation.w)
+	dynamic_obj.scale = obj.scale
+	dynamic_obj.name = "dynamic_%s" % obj.id
+	add_child(dynamic_obj)
+
+
+## Get a world object by its ID.
+func get_object_by_id(object_id: String) -> WorldObject:
+	for obj in world_objects:
+		if obj.id == object_id:
+			return obj
+	return null
+
+
+## Get all static objects in this chunk.
+func get_static_objects() -> Array[WorldObject]:
+	var result: Array[WorldObject] = []
+	for obj in world_objects:
+		if not obj.is_dynamic:
+			result.append(obj)
+	return result
+
+
+## Get all dynamic object templates in this chunk.
+func get_dynamic_templates() -> Array[WorldObject]:
+	var result: Array[WorldObject] = []
+	for obj in world_objects:
+		if obj.is_dynamic:
+			result.append(obj)
+	return result
+
+
+## Mark this chunk as dirty (locally modified).
+func mark_dirty() -> void:
+	is_dirty = true
+
+
+## Clear all objects and tile layers from this chunk.
+func clear() -> void:
+	for child in get_children():
+		if child is TileLayerNode or child is StaticObjectNode or child is DynamicObjectNode:
+			child.queue_free()
+	tile_layers.clear()
+	world_objects.clear()
+
+
+## Get the world-space position of a tile within this chunk.
+func get_tile_world_position(tile_x: int, tile_y: int, tile_z: int = 0) -> Vector3:
+	return bounds.position + Vector3(
+		tile_x * 1.0,  # Tile size is 1 world unit
+		tile_y * 1.0,
+		tile_z * 1.0
+	)
+
+
+## Check if a world-space position is within this chunk's bounds.
+func contains_position(pos: Vector3) -> bool:
+	return bounds.has_point(pos)
+
+
+## Check if a chunk coordinate is adjacent to this chunk.
+func is_adjacent(other_coord: Vector3i) -> bool:
+	var dx: int = abs(coord.x - other_coord.x)
+	var dy: int = abs(coord.y - other_coord.y)
+	var dz: int = abs(coord.z - other_coord.z)
+	return dx <= 1 and dy <= 1 and dz <= 1 and (dx + dy + dz) > 0

scripts/chunk_scene.gd.uid

@@ -0,0 +1 @@
+uid://d4gh4h5iey6xb

scripts/chunk_stream_manager.gd

@@ -0,0 +1,358 @@
+class_name ChunkStreamManager
+extends Node
+## Manages loading and unloading of world chunks based on player position.
+##
+## This is the central orchestrator for the chunk streaming system. It monitors
+## the player's position, determines which chunks should be loaded, requests
+## chunk data from the server, instantiates ChunkScene nodes, and unloads
+## chunks that fall outside the streaming radius.
+##
+## ## Design
+##
+## - **Streaming radius** defines how many chunks around the player are kept
+##   loaded. Chunks beyond this radius are unloaded to save memory and CPU.
+## - **Load priority** ensures chunks closer to the player are loaded first,
+##   preventing visual pop-in at the edge of the view.
+## - **Server communication** uses the RPCs defined in docs/architecture/world.md
+##   (§5.3): `request_chunk`, `chunk_data`, `chunk_invalidated`.
+##
+## ## Usage
+##
+## Add this node to your scene tree and set the `player` reference:
+## ```gdscript
+## var stream_manager: ChunkStreamManager = $ChunkStreamManager
+## stream_manager.player = $Player
+## stream_manager.streaming_radius = 4  # chunks
+## ```
+
+## Number of chunks (radius) to keep loaded around the player.
+## A radius of 2 means a 5x5 grid of chunks centered on the player.
+## Higher values increase memory usage but reduce streaming pop-in.
+@export var streaming_radius: int = 3
+
+## Maximum number of chunks to load per frame. Prevents frame spikes during
+## rapid movement or when entering a new area.
+@export var max_loads_per_frame: int = 4
+
+## Maximum number of chunks to unload per frame.
+@export var max_unloads_per_frame: int = 4
+
+## Distance (in chunks) from the streaming radius edge before a chunk is
+## considered for unloading. Prevents rapid load/unload cycling.
+@export var unload_margin: int = 1
+
+## Emitted when a chunk finishes loading.
+signal chunk_loaded(chunk_coord: Vector3i, chunk_scene: Node)
+
+## Emitted when a chunk is unloaded.
+signal chunk_unloaded(chunk_coord: Vector3i)
+
+## Emitted when a chunk fails to load (e.g., server error).
+signal chunk_load_failed(chunk_coord: Vector3i, error: String)
+
+## Emitted when the player moves far enough to require a streaming update.
+signal streaming_updated
+
+## Reference to the player node. Must be set before the manager starts.
+var player: Node3D = null
+
+## The current player chunk coordinate.
+var _player_chunk_coord: Vector3i = Vector3i.ZERO
+
+## Map of loaded chunk coordinates to their scene nodes.
+var _loaded_chunks: Dictionary = {}
+
+## Queue of chunk coordinates pending load, sorted by distance from player.
+var _load_queue: Array[Vector3i] = []
+
+## Queue of chunk coordinates pending unload.
+var _unload_queue: Array[Vector3i] = []
+
+## Whether streaming is currently active (player is set and in game).
+var is_active: bool = false
+
+## The server RPC interface for chunk data. Set by the networking layer.
+var _server_rpc: Object = null
+
+## Internal: track which chunks are currently being loaded (to avoid duplicates).
+var _loading_in_progress: Dictionary = {}
+
+## Internal: time accumulator for throttled streaming updates.
+var _update_accumulator: float = 0.0
+
+## Internal: interval between streaming updates (seconds).
+const UPDATE_INTERVAL: float = 0.1
+
+
+func _ready() -> void:
+	# Streaming is driven from _process (main thread) so we can safely
+	# manipulate the scene tree. No background thread is used.
+	set_process(true)
+
+
+func _process(delta: float) -> void:
+	if not is_active or player == null:
+		return
+
+	_update_accumulator += delta
+	if _update_accumulator < UPDATE_INTERVAL:
+		return
+	_update_accumulator = 0.0
+
+	_update_streaming()
+	_process_load_queue()
+	_process_unload_queue()
+	streaming_updated.emit()
+
+
+func _update_streaming() -> void:
+	if player == null or not is_inside_tree():
+		return
+
+	var current_coord: Vector3i = Chunk.coord_for_position(player.global_position)
+	if current_coord == _player_chunk_coord:
+		return
+
+	_player_chunk_coord = current_coord
+	_rebuild_queues()
+
+
+func _rebuild_queues() -> void:
+	var target_set: Dictionary = _compute_target_chunks()
+
+	# Determine which chunks need to be loaded
+	var to_load: Array[Vector3i] = []
+	for coord in target_set:
+		if not _loaded_chunks.has(coord) and not _loading_in_progress.has(coord):
+			to_load.append(coord)
+
+	# Sort by distance from player (closest first)
+	to_load.sort_custom(_compare_distance)
+	_load_queue = to_load
+
+	# Determine which chunks need to be unloaded
+	var to_unload: Array[Vector3i] = []
+	for coord in _loaded_chunks:
+		if not target_set.has(coord):
+			to_unload.append(coord)
+
+	to_unload.sort_custom(_compare_distance)
+	_unload_queue = to_unload
+
+
+func _compute_target_chunks() -> Dictionary:
+	"""Compute the set of chunk coordinates that should be loaded."""
+	var target: Dictionary = {}
+	var half: int = streaming_radius
+	for dx in range(-half, half + 1):
+		for dy in range(-half, half + 1):
+			for dz in range(-half, half + 1):
+				var coord: Vector3i = Vector3i(
+					_player_chunk_coord.x + dx,
+					_player_chunk_coord.y + dy,
+					_player_chunk_coord.z + dz
+				)
+				target[coord] = coord
+	return target
+
+
+func _compare_distance(a: Vector3i, b: Vector3i) -> bool:
+	"""Compare chunk coordinates by distance from player chunk."""
+	var dist_a: int = _chunk_distance_squared(_player_chunk_coord, a)
+	var dist_b: int = _chunk_distance_squared(_player_chunk_coord, b)
+	return dist_a < dist_b
+
+
+func _chunk_distance_squared(a: Vector3i, b: Vector3i) -> int:
+	var dx: int = a.x - b.x
+	var dy: int = a.y - b.y
+	var dz: int = a.z - b.z
+	return dx * dx + dy * dy + dz * dz
+
+
+func _process_load_queue() -> void:
+	var count: int = 0
+	while count < max_loads_per_frame and not _load_queue.is_empty():
+		var coord: Vector3i = _load_queue.pop_front()
+		_load_chunk(coord)
+		count += 1
+
+
+func _process_unload_queue() -> void:
+	var count: int = 0
+	while count < max_unloads_per_frame and not _unload_queue.is_empty():
+		var coord: Vector3i = _unload_queue.pop_front()
+		_unload_chunk(coord)
+		count += 1
+
+
+func _load_chunk(coord: Vector3i) -> void:
+	if _loading_in_progress.has(coord):
+		return
+
+	_loading_in_progress[coord] = true
+
+	# Request chunk data from server via RPC
+	if _server_rpc != null and _server_rpc.has_method("request_chunk"):
+		_server_rpc.request_chunk(Chunk.build_key(
+			"", "", coord
+		))
+	else:
+		# Fallback: try to load from local cache or create empty chunk
+		_instantiate_chunk_scene(coord)
+
+
+func _on_chunk_data_received(key: String, binary_data: PackedByteArray) -> void:
+	"""Called by the networking layer when chunk data arrives from server."""
+	var coord: Vector3i = _parse_coord_from_key(key)
+	if coord == null:
+		return
+
+	_loading_in_progress.erase(coord)
+
+	# Decode the binary chunk data
+	var chunk_data: ChunkDataDecoder.ChunkPayload = ChunkDataDecoder.decode_binary(binary_data)
+	if chunk_data == null:
+		chunk_load_failed.emit(coord, "Failed to decode chunk data")
+		return
+
+	# Instantiate the chunk scene with the decoded data
+	_instantiate_chunk_scene_with_data(coord, chunk_data)
+
+
+func _on_chunk_load_error(coord: Vector3i, error_msg: String) -> void:
+	"""Called when the server reports a chunk load error."""
+	_loading_in_progress.erase(coord)
+	chunk_load_failed.emit(coord, error_msg)
+
+
+func _instantiate_chunk_scene(coord: Vector3i) -> void:
+	"""Create an empty chunk scene for the given coordinate."""
+	var chunk_scene: ChunkScene = ChunkScene.new()
+	chunk_scene.coord = coord
+	chunk_scene.key = Chunk.build_key("", "", coord)
+	chunk_scene.bounds = Chunk.compute_bounds(coord)
+	_add_loaded_chunk(coord, chunk_scene)
+
+
+func _instantiate_chunk_scene_with_data(coord: Vector3i, data: ChunkDataDecoder.ChunkPayload) -> void:
+	"""Create a chunk scene populated with server data."""
+	var chunk_scene: ChunkScene = ChunkScene.new()
+	chunk_scene.coord = coord
+	chunk_scene.key = data.key
+	chunk_scene.bounds = data.bounds
+	chunk_scene.format_version = data.format_version
+	chunk_scene.revision = data.revision
+
+	# Add tiles
+	for layer in data.tile_layers:
+		var tile_layer: TileLayer = TileLayer.new()
+		tile_layer.name = layer.name
+		tile_layer.layer_id = layer.layer_id
+		tile_layer.width = layer.width
+		tile_layer.height = layer.height
+		tile_layer.depth = layer.depth
+		tile_layer.palette = layer.palette
+		tile_layer.tiles = layer.tiles
+		chunk_scene.add_tile_layer(tile_layer)
+
+	# Add objects
+	for obj_data in data.objects:
+		var world_obj: WorldObject = WorldObject.new()
+		world_obj.id = obj_data.id
+		world_obj.type = obj_data.type
+		world_obj.asset_id = obj_data.asset_id
+		world_obj.position = obj_data.position
+		world_obj.rotation = obj_data.rotation
+		world_obj.scale = obj_data.scale
+		world_obj.properties = obj_data.properties
+		world_obj.is_dynamic = obj_data.dynamic
+		world_obj.flags = obj_data.flags
+		chunk_scene.add_object(world_obj)
+
+	# Add content flags
+	chunk_scene.content_flags = data.flags
+
+	_add_loaded_chunk(coord, chunk_scene)
+
+
+func _add_loaded_chunk(coord: Vector3i, chunk_scene: Node) -> void:
+	_loaded_chunks[coord] = chunk_scene
+	add_child(chunk_scene)
+	_loading_in_progress.erase(coord)
+	chunk_loaded.emit(coord, chunk_scene)
+
+
+func _unload_chunk(coord: Vector3i) -> void:
+	if not _loaded_chunks.has(coord):
+		return
+
+	var chunk_scene: Node = _loaded_chunks[coord]
+	if is_instance_valid(chunk_scene):
+		chunk_scene.queue_free()
+
+	_loaded_chunks.erase(coord)
+	chunk_unloaded.emit(coord)
+
+
+func _on_player_position_changed() -> void:
+	"""Call this when the player position changes significantly."""
+	if player != null:
+		_update_streaming()
+
+
+func set_server_rpc(rpc_interface: Object) -> void:
+	"""Set the server RPC interface for chunk requests."""
+	_server_rpc = rpc_interface
+
+
+func get_loaded_chunk(coord: Vector3i) -> Node:
+	"""Get a loaded chunk scene by coordinate, or null if not loaded."""
+	return _loaded_chunks.get(coord, null)
+
+
+func is_chunk_loaded(coord: Vector3i) -> bool:
+	"""Check if a chunk is currently loaded."""
+	return _loaded_chunks.has(coord)
+
+
+func get_loaded_chunk_count() -> int:
+	"""Get the number of currently loaded chunks."""
+	return _loaded_chunks.size()
+
+
+func get_all_loaded_coords() -> Array[Vector3i]:
+	"""Get all currently loaded chunk coordinates."""
+	var coords: Array[Vector3i] = []
+	for key in _loaded_chunks:
+		coords.append(key)
+	return coords
+
+
+func force_reload_chunk(coord: Vector3i) -> void:
+	"""Force reload a specific chunk (e.g., after server update)."""
+	if _loaded_chunks.has(coord):
+		_unload_chunk(coord)
+	if not _loading_in_progress.has(coord):
+		_load_chunk(coord)
+
+
+func clear_all_chunks() -> void:
+	"""Unload all chunks immediately."""
+	var coords: Array[Vector3i] = get_all_loaded_coords()
+	for coord in coords:
+		_unload_chunk(coord)
+	_load_queue.clear()
+	_unload_queue.clear()
+
+
+func _parse_coord_from_key(key: String) -> Variant:
+	"""Parse chunk coordinate from a canonical chunk key."""
+	var parts: Array[String] = key.split(":")
+	if parts.size() < 5:
+		return null
+	return Vector3i(
+		int(parts[2]),
+		int(parts[3]),
+		int(parts[4])
+	)

scripts/chunk_stream_manager.gd.uid

@@ -0,0 +1 @@
+uid://8yokqwe23c23

scripts/dynamic_object_node.gd

@@ -0,0 +1,68 @@
+class_name DynamicObjectNode
+extends Node3D
+## A visual representation of a dynamic (spawnable) world object template.
+##
+## This node is instantiated by [ChunkScene] for each dynamic [WorldObject].
+## Dynamic objects are stored as *templates* in the chunk; their runtime state
+## (position, health, inventory) is managed by the entity system, not by this
+## node. This node renders the template's visual representation so the object
+## is visible in the world.
+##
+## ## Structure
+##
+## ```
+## DynamicObjectNode (Node3D)
+##  └── MeshInstance3D  # the object's visual mesh
+## ```
+
+## The world object data this node represents.
+var world_object: WorldObject = null
+
+## The loaded mesh instance (or placeholder).
+var _mesh_instance: MeshInstance3D = null
+
+
+func _ready() -> void:
+	if world_object == null:
+		return
+	_load_mesh()
+
+
+## Load and attach the object's mesh.
+func _load_mesh() -> void:
+	_mesh_instance = MeshInstance3D.new()
+	_mesh_instance.name = "mesh"
+
+	var mesh := _load_asset_mesh(world_object.asset_id)
+	if mesh == null:
+		mesh = _make_placeholder_mesh()
+
+	_mesh_instance.mesh = mesh
+	add_child(_mesh_instance)
+
+
+## Attempt to load a mesh from the asset path.
+func _load_asset_mesh(asset_id: String) -> Mesh:
+	if asset_id.is_empty():
+		return null
+	var path := "res://assets/%s" % asset_id
+	if ResourceLoader.exists(path):
+		var res := load(path)
+		if res is Mesh:
+			return res
+	return null
+
+
+## Create a simple placeholder sphere mesh when the real asset is unavailable.
+func _make_placeholder_mesh() -> Mesh:
+	var mesh := SphereMesh.new()
+	mesh.radius = 0.5
+	mesh.height = 1.0
+	return mesh
+
+
+## Get the world object's display name.
+func get_display_name() -> String:
+	if world_object == null:
+		return ""
+	return world_object.get_display_name()

scripts/dynamic_object_node.gd.uid

@@ -0,0 +1 @@
+uid://dyjqcstdnr4u1

scripts/static_object_node.gd

@@ -0,0 +1,67 @@
+class_name StaticObjectNode
+extends Node3D
+## A visual representation of a static world object within a chunk.
+##
+## This node is instantiated by [ChunkScene] for each static (non-dynamic)
+## [WorldObject]. It renders the object's mesh (referenced by `asset_id`) at
+## the object's transform. If the asset is not yet loaded, a placeholder mesh
+## is shown.
+##
+## ## Structure
+##
+## ```
+## StaticObjectNode (Node3D)
+##  └── MeshInstance3D  # the object's visual mesh
+## ```
+
+## The world object data this node represents.
+var world_object: WorldObject = null
+
+## The loaded mesh instance (or placeholder).
+var _mesh_instance: MeshInstance3D = null
+
+
+func _ready() -> void:
+	if world_object == null:
+		return
+	_load_mesh()
+
+
+## Load and attach the object's mesh.
+func _load_mesh() -> void:
+	_mesh_instance = MeshInstance3D.new()
+	_mesh_instance.name = "mesh"
+
+	# Try to load the asset by its id (path). Fall back to a placeholder.
+	var mesh := _load_asset_mesh(world_object.asset_id)
+	if mesh == null:
+		mesh = _make_placeholder_mesh()
+
+	_mesh_instance.mesh = mesh
+	add_child(_mesh_instance)
+
+
+## Attempt to load a mesh from the asset path.
+func _load_asset_mesh(asset_id: String) -> Mesh:
+	if asset_id.is_empty():
+		return null
+	var path := "res://assets/%s" % asset_id
+	if ResourceLoader.exists(path):
+		var res := load(path)
+		if res is Mesh:
+			return res
+	return null
+
+
+## Create a simple placeholder box mesh when the real asset is unavailable.
+func _make_placeholder_mesh() -> Mesh:
+	var mesh := BoxMesh.new()
+	mesh.size = Vector3(1.0, 1.0, 1.0)
+	return mesh
+
+
+## Get the world object's display name.
+func get_display_name() -> String:
+	if world_object == null:
+		return ""
+	return world_object.get_display_name()

scripts/static_object_node.gd.uid

@@ -0,0 +1 @@
+uid://chf6mruev1kc4

scripts/tile_def.gd

@@ -0,0 +1,42 @@
+class_name TileDef
+extends RefCounted
+## A single tile definition (palette entry) within a tile layer.
+##
+## Maps a tile ID to its asset reference and gameplay flags. See
+## docs/architecture/world.md §3.2.
+
+## Tile ID (index into the layer palette). 0 is reserved for empty/air.
+var id: int = 0
+
+## Reference to the tile/terrain asset.
+var asset_id: String = ""
+
+## Whether this tile has collision.
+var solid: bool = false
+
+## Bitmask flags: bit 0 = walkable, bit 1 = climbable, bit 2 = liquid.
+var flags: int = 0
+
+## Number of visual variants for this tile.
+var variants: int = 1
+
+
+func _init(p_id: int = 0, p_asset_id: String = "", p_solid: bool = false,
+		p_flags: int = 0, p_variants: int = 1) -> void:
+	id = p_id
+	asset_id = p_asset_id
+	solid = p_solid
+	flags = p_flags
+	variants = p_variants
+
+
+func is_walkable() -> bool:
+	return (flags & 0x01) != 0
+
+
+func is_climbable() -> bool:
+	return (flags & 0x02) != 0
+
+
+func is_liquid() -> bool:
+	return (flags & 0x04) != 0

scripts/tile_def.gd.uid

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

scripts/tile_layer.gd

@@ -0,0 +1,83 @@
+class_name TileLayer
+extends RefCounted
+## A single tile layer within a chunk.
+##
+## Holds the dense grid of tile IDs, the palette mapping tile IDs to tile
+## definitions, and the layer metadata. This is the runtime representation of
+## the `TileLayer` from the chunk data format (see docs/architecture/world.md
+## §3.2).
+
+## Layer name (e.g. "ground", "walls", "decor").
+var name: String = ""
+
+## Numeric layer id, unique within the chunk.
+var layer_id: int = 0
+
+## Grid dimensions in tiles.
+var width: int = 0
+var height: int = 0
+var depth: int = 1
+
+## Palette mapping tile IDs to tile definitions (shared per layer).
+var palette: Array[TileDef] = []
+
+## Dense, row-major tile IDs. Length = width * height * depth.
+var tiles: PackedInt32Array = PackedInt32Array()
+
+
+func _init(
+	p_layer_name: String = "",
+	p_layer_id: int = 0,
+	p_width: int = 0,
+	p_height: int = 0,
+	p_depth: int = 1
+) -> void:
+	name = p_layer_name
+	layer_id = p_layer_id
+	width = p_width
+	height = p_height
+	depth = p_depth
+
+
+## Total number of tiles in this layer.
+func tile_count() -> int:
+	return width * height * depth
+
+
+## Get the tile ID at (x, y, z). Returns 0 (empty) for out-of-bounds.
+func get_tile(x: int, y: int, z: int = 0) -> int:
+	if x < 0 or x >= width or y < 0 or y >= height or z < 0 or z >= depth:
+		return 0
+	var idx := (z * height + y) * width + x
+	if idx < tiles.size():
+		return tiles[idx]
+	return 0
+
+
+## Set the tile ID at (x, y, z). No-op if out of bounds.
+func set_tile(x: int, y: int, z: int, tile_id: int) -> void:
+	if x < 0 or x >= width or y < 0 or y >= height or z < 0 or z >= depth:
+		return
+	var idx := (z * height + y) * width + x
+	if idx < tiles.size():
+		tiles[idx] = tile_id
+
+
+## Get the tile definition for a tile ID, or null if not in the palette.
+func get_tile_def(tile_id: int) -> TileDef:
+	for def in palette:
+		if def.id == tile_id:
+			return def
+	return null
+
+
+## Whether the tile at (x, y, z) is solid (collision).
+func is_solid(x: int, y: int, z: int = 0) -> bool:
+	var def := get_tile_def(get_tile(x, y, z))
+	return def != null and def.solid
+
+
+## Whether the tile at (x, y, z) is walkable.
+func is_walkable(x: int, y: int, z: int = 0) -> bool:
+	var def := get_tile_def(get_tile(x, y, z))
+	return def != null and def.is_walkable()

scripts/tile_layer.gd.uid

@@ -0,0 +1 @@
+uid://came2ygke3ajs

scripts/tile_layer_node.gd

@@ -0,0 +1,112 @@
+class_name TileLayerNode
+extends Node3D
+## A visual representation of a single tile layer within a chunk.
+##
+## This node is instantiated by [ChunkScene] for each tile layer in a chunk.
+## It renders the layer's tiles as instanced meshes (one per tile definition
+## in the palette) using [MultiMeshInstance3D] for efficiency.
+##
+## ## Structure
+##
+## ```
+## TileLayerNode (Node3D)
+##  └── MultiMeshInstance3D  # one per palette entry (tile definition)
+## ```
+
+## The tile layer data this node renders.
+var tile_layer: TileLayer = null
+
+## The chunk coordinate this layer belongs to (for world positioning).
+var chunk_coord: Vector3i = Vector3i.ZERO
+
+## Tile size in world units (each tile is 1x1x1).
+const TILE_SIZE: float = 1.0
+
+## Cache of MultiMeshInstance3D nodes, keyed by tile definition id.
+var _mesh_instances: Dictionary = {}
+
+
+func _ready() -> void:
+	if tile_layer == null:
+		return
+	_build_meshes()
+
+
+## Build the MultiMesh instances for each tile definition in the palette.
+func _build_meshes() -> void:
+	for tile_def in tile_layer.palette:
+		if tile_def.id == 0:
+			continue  # Tile 0 is "empty/air", no mesh needed
+		_create_mesh_for_tile(tile_def)
+
+
+func _create_mesh_for_tile(tile_def: TileDef) -> void:
+	# Count how many cells use this tile definition
+	var count := 0
+	for tile_id in tile_layer.tiles:
+		if tile_id == tile_def.id:
+			count += 1
+
+	if count == 0:
+		return
+
+	var multi_mesh := MultiMesh.new()
+	multi_mesh.transform_format = MultiMesh.TRANSFORM_3D
+	multi_mesh.mesh = _make_unit_cube_mesh()
+	multi_mesh.instance_count = count
+
+	var instance_idx := 0
+	for z in range(tile_layer.depth):
+		for y in range(tile_layer.height):
+			for x in range(tile_layer.width):
+				var tile_id := tile_layer.get_tile(x, y, z)
+				if tile_id != tile_def.id:
+					continue
+				var world_pos := _tile_to_world(x, y, z)
+				var xform := Transform3D(Basis(), world_pos)
+				multi_mesh.set_instance_transform(instance_idx, xform)
+				instance_idx += 1
+
+	var mesh_instance := MultiMeshInstance3D.new()
+	mesh_instance.multimesh = multi_mesh
+	mesh_instance.name = "tiles_%d" % tile_def.id
+	add_child(mesh_instance)
+	_mesh_instances[tile_def.id] = mesh_instance
+
+
+## Convert a tile grid coordinate to a world-space position (center of tile).
+func _tile_to_world(x: int, y: int, z: int) -> Vector3:
+	var origin := Vector3(
+		chunk_coord.x * tile_layer.width,
+		chunk_coord.y * tile_layer.height,
+		chunk_coord.z * tile_layer.depth
+	)
+	return origin + Vector3(
+		x * TILE_SIZE + TILE_SIZE * 0.5,
+		y * TILE_SIZE + TILE_SIZE * 0.5,
+		z * TILE_SIZE + TILE_SIZE * 0.5
+	)
+
+
+## Create a simple unit cube mesh for tile rendering.
+func _make_unit_cube_mesh() -> Mesh:
+	var mesh := BoxMesh.new()
+	mesh.size = Vector3(TILE_SIZE, TILE_SIZE, TILE_SIZE)
+	return mesh
+
+
+## Get the tile definition at a grid position, or null if empty.
+func get_tile_def_at(x: int, y: int, z: int = 0) -> TileDef:
+	if tile_layer == null:
+		return null
+	var tile_id := tile_layer.get_tile(x, y, z)
+	if tile_id == 0:
+		return null
+	return tile_layer.get_tile_def(tile_id)
+
+
+## Clear all rendered meshes.
+func clear() -> void:
+	for child in get_children():
+		child.queue_free()
+	_mesh_instances.clear()

scripts/tile_layer_node.gd.uid

@@ -0,0 +1 @@
+uid://d1x05tq8h43gm

scripts/world_object.gd

@@ -0,0 +1,135 @@
+class_name WorldObject
+extends RefCounted
+## A world object (static or dynamic) within a chunk.
+##
+## This is the runtime representation of a WorldObject from the chunk data
+## format (see docs/architecture/world.md §3.3). It holds the object's
+## identity, transform, properties, and moderation flags.
+
+## Stable object ID, unique within the chunk.
+var id: String = ""
+
+## Object type (e.g. "prop", "interactable", "spawn_point", "door").
+var type: String = ""
+
+## Reference to the object's mesh/glTF asset.
+var asset_id: String = ""
+
+## World-space position.
+var position: Vector3 = Vector3.ZERO
+
+## World-space rotation as a quaternion (x, y, z, w).
+var rotation: Vector4 = Vector4(0, 0, 0, 1)
+
+## World-space scale.
+var scale: Vector3 = Vector3.ONE
+
+## Type-specific key/value properties.
+var properties: Dictionary = {}
+
+## Whether this is a spawnable dynamic entity (true) or static (false).
+var is_dynamic: bool = false
+
+## Per-object content moderation flags.
+var flags: ChunkDataDecoder.ContentFlags = ChunkDataDecoder.ContentFlags.new()
+
+## Whether this object has been modified locally.
+var is_dirty: bool = false
+
+
+func _init(
+	p_id: String = "",
+	p_type: String = "",
+	p_asset_id: String = "",
+	p_position: Vector3 = Vector3.ZERO,
+	p_rotation: Vector4 = Vector4(0, 0, 0, 1),
+	p_scale: Vector3 = Vector3.ONE,
+	p_properties: Dictionary = {},
+	p_dynamic: bool = false,
+	p_flags: ChunkDataDecoder.ContentFlags = null
+) -> void:
+	id = p_id
+	type = p_type
+	asset_id = p_asset_id
+	position = p_position
+	rotation = p_rotation
+	scale = p_scale
+	properties = p_properties
+	is_dynamic = p_dynamic
+	if p_flags != null:
+		flags = p_flags
+
+
+## Get a property value by key.
+func get_property(key: String) -> Variant:
+	return properties.get(key)
+
+
+## Set a property value.
+func set_property(key: String, value: Variant) -> void:
+	properties[key] = value
+	is_dirty = true
+
+
+## Check if this object is walkable (based on properties).
+func is_walkable() -> bool:
+	return properties.get("walkable", true)
+
+
+## Check if this object is climbable (based on properties).
+func is_climbable() -> bool:
+	return properties.get("climbable", false)
+
+
+## Check if this object is interactable.
+func is_interactable() -> bool:
+	return type == "interactable" or properties.get("interactable", false)
+
+
+## Get the object's display name.
+func get_display_name() -> String:
+	return properties.get("display_name", id)
+
+
+## Serialize this object to a dictionary (for networking).
+func to_dict() -> Dictionary:
+	return {
+		"id": id,
+		"type": type,
+		"asset_id": asset_id,
+		"position": [position.x, position.y, position.z],
+		"rotation": [rotation.x, rotation.y, rotation.z, rotation.w],
+		"scale": [scale.x, scale.y, scale.z],
+		"properties": properties,
+		"dynamic": is_dynamic,
+	}
+
+
+## Create a WorldObject from a dictionary (for networking).
+static func from_dict(d: Dictionary) -> WorldObject:
+	var pos := Vector3(
+		d.get("position", [0, 0, 0])[0],
+		d.get("position", [0, 0, 0])[1],
+		d.get("position", [0, 0, 0])[2]
+	)
+	var rot := Vector4(
+		d.get("rotation", [0, 0, 0, 1])[0],
+		d.get("rotation", [0, 0, 0, 1])[1],
+		d.get("rotation", [0, 0, 0, 1])[2],
+		d.get("rotation", [0, 0, 0, 1])[3]
+	)
+	var scl := Vector3(
+		d.get("scale", [1, 1, 1])[0],
+		d.get("scale", [1, 1, 1])[1],
+		d.get("scale", [1, 1, 1])[2]
+	)
+	return WorldObject.new(
+		d.get("id", ""),
+		d.get("type", ""),
+		d.get("asset_id", ""),
+		pos,
+		rot,
+		scl,
+		d.get("properties", {}),
+		d.get("dynamic", false),
+	)

scripts/world_object.gd.uid

@@ -0,0 +1 @@
+uid://cxut2ghbsvobn