WIP checkpoint: US-1: Asset Import Pipeline \u2014 glTF upload endpoint with metadata extraction

- Architecture task: ApiClient autoload (HTTP + JWT + error contract)
- Implementation task: Login/Register UI wired to /api/auth
- Implementation task: Browse worlds screen wired to GET /api/worlds
- Validation task: End-to-end smoke test (login + list worlds)

backend/alembic/versions/0001_initial.py

@@ -69,7 +69,8 @@ def upgrade() -> None:
         sa.Column(
             "visibility",
             postgresql.ENUM(
-                "public", "private", "friends_only", name="world_visibility"
+                "public", "private", "friends_only", name="world_visibility",
+                create_type=False,
             ),
             nullable=True,
         ),
@@ -89,7 +90,7 @@ def upgrade() -> None:
             "asset_type",
             postgresql.ENUM(
                 "image", "audio", "video", "document", "model_3d", "other",
-                name="asset_type",
+                name="asset_type", create_type=False,
             ),
             nullable=False,
         ),

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/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/assets.py

@@ -1,5 +1,6 @@
 """Asset management router."""
 
+import json
 import os
 from pathlib import Path
 from typing import Optional
@@ -37,6 +38,7 @@ class AssetResponse(BaseModel):
     file_path: str
     file_size: Optional[int]
     mime_type: Optional[str]
+    metadata_json: Optional[dict]
     world_id: Optional[int]
     owner_id: int
     is_public: bool
@@ -45,6 +47,18 @@ class AssetResponse(BaseModel):
 
     model_config = {"from_attributes": True}
 
+    @classmethod
+    def model_validate(cls, obj, **kwargs):
+        """Override to handle metadata_json stored as JSON string."""
+        if isinstance(obj, dict):
+            obj = dict(obj)
+            if "metadata_json" in obj and isinstance(obj["metadata_json"], str):
+                try:
+                    obj["metadata_json"] = json.loads(obj["metadata_json"])
+                except (json.JSONDecodeError, TypeError):
+                    obj["metadata_json"] = None
+        return super().model_validate(obj, **kwargs)
+
 
 class AssetUpdate(BaseModel):
     """Schema for updating an asset."""
@@ -64,6 +78,144 @@ def _sanitize_filename(filename: str) -> str:
     return safe or "file"
 
 
+def _extract_gltf_metadata(content: bytes) -> Optional[dict]:
+    """Extract metadata from a glTF/GLB file.
+
+    Returns a dict with mesh_count, vertex_count, has_animation, texture_refs
+    if the file is a valid glTF/GLB, or None otherwise.
+
+    Uses only the standard library (struct, json) so no extra dependencies
+    are required.
+    """
+    if not content:
+        return None
+
+    # --- GLB detection ---
+    # GLB magic: 0x676C5442 ("glTF") followed by version 2 and payload length.
+    if len(content) >= 12:
+        magic = int.from_bytes(content[0:4], "little")
+        if magic == 0x46546C67:  # "glTF"
+            version = int.from_bytes(content[4:8], "little")
+            if version == 2:
+                return _parse_glb(content)
+
+    # --- .gltf JSON detection ---
+    # Try parsing as JSON; if it has a top-level "scene" or "scenes" key,
+    # it's likely a .gltf file.
+    try:
+        data = json.loads(content)
+    except (json.JSONDecodeError, UnicodeDecodeError):
+        return None
+
+    if not isinstance(data, dict):
+        return None
+
+    if "scene" not in data and "scenes" not in data:
+        return None
+
+    return _parse_gltf_json(data)
+
+
+def _parse_glb(content: bytes) -> Optional[dict]:
+    """Parse a binary GLB chunk structure."""
+    # Header: magic(4) + version(4) + length(4) = 12 bytes
+    # Then chunks: length(4) + type(4) + data...
+    offset = 12
+    json_start = None
+    json_length = 0
+    binary_start = None
+    binary_length = 0
+
+    while offset < len(content):
+        if offset + 8 > len(content):
+            break
+        chunk_length = int.from_bytes(content[offset:offset + 4], "little")
+        chunk_type = int.from_bytes(content[offset + 4:offset + 8], "little")
+        chunk_data_start = offset + 8
+
+        if chunk_type == 0x4E4F534A:  # JSON chunk
+            json_start = chunk_data_start
+            json_length = chunk_length
+        elif chunk_type == 0x00424946:  # BIN chunk
+            binary_start = chunk_data_start
+            binary_length = chunk_length
+
+        offset = chunk_data_start + chunk_length
+
+    if json_start is None:
+        return None
+
+    try:
+        json_bytes = content[json_start:json_start + json_length]
+        data = json.loads(json_bytes)
+    except (json.JSONDecodeError, UnicodeDecodeError):
+        return None
+
+    return _parse_gltf_json(data)
+
+
+def _parse_gltf_json(data: dict) -> Optional[dict]:
+    """Parse a glTF JSON structure and extract metadata."""
+    meshes = data.get("meshes") or []
+    animations = data.get("animations") or []
+    textures = data.get("textures") or []
+    images = data.get("images") or []
+    accessors = data.get("accessors") or []
+
+    # Count meshes
+    mesh_count = len(meshes)
+
+    # Count total vertices across all primitives
+    vertex_count = 0
+    for mesh in meshes:
+        primitives = mesh.get("primitives") or []
+        for primitive in primitives:
+            indices = primitive.get("indices")
+            if indices is not None:
+                # Use index count from accessor
+                if indices < len(accessors) and accessors[indices]:
+                    vertex_count += accessors[indices].get("count", 1)
+                else:
+                    vertex_count += 1
+            else:
+                # No indices — count from POSITION attribute
+                attributes = primitive.get("attributes") or {}
+                pos_accessor = attributes.get("POSITION")
+                if pos_accessor is not None:
+                    if pos_accessor < len(accessors) and accessors[pos_accessor]:
+                        vertex_count += accessors[pos_accessor].get("count", 1)
+                    else:
+                        vertex_count += 1
+                else:
+                    vertex_count += 1  # fallback
+
+    # Check for animations
+    has_animation = len(animations) > 0
+
+    # Collect texture references
+    texture_refs = []
+    for texture in textures:
+        source_index = texture.get("source")
+        ref = {}
+        if source_index is not None and source_index < len(images):
+            image = images[source_index]
+            if isinstance(image, dict):
+                if image.get("name"):
+                    ref["name"] = image["name"]
+                if image.get("uri"):
+                    ref["uri"] = image["uri"]
+                if image.get("mimeType"):
+                    ref["mime_type"] = image["mimeType"]
+        texture_refs.append(ref)
+
+    return {
+        "mesh_count": mesh_count,
+        "vertex_count": vertex_count,
+        "has_animation": has_animation,
+        "texture_refs": texture_refs,
+    }
+
+
 # --- Endpoints ---
 
 @router.post("/", response_model=AssetResponse, status_code=201)
@@ -204,6 +356,13 @@ async def upload_asset_file(
     asset.mime_type = file.content_type
     asset.file_size = file_size
 
+    # Extract glTF metadata for glTF/GLB files.
+    filename_lower = (file.filename or "").lower()
+    if filename_lower.endswith(".glb") or filename_lower.endswith(".gltf"):
+        metadata = _extract_gltf_metadata(content)
+        if metadata is not None:
+            asset.metadata_json = json.dumps(metadata)
+
     await db.commit()
     await db.refresh(asset)
     return asset

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/docker-compose.yml

@@ -8,7 +8,7 @@ services:
       POSTGRES_PASSWORD: agp_password
       POSTGRES_DB: agp_db
     ports:
-      - "5432:5432"
+      - "${POSTGRES_HOST_PORT:-5432}:5432"
     volumes:
       - postgres_data:/var/lib/postgresql/data
     healthcheck:
@@ -20,7 +20,7 @@ services:
   redis:
     image: redis:7-alpine
     ports:
-      - "6379:6379"
+      - "${REDIS_HOST_PORT:-6379}:6379"
     volumes:
       - redis_data:/data
     healthcheck:

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/client-server-wiring.md

@@ -0,0 +1,37 @@
+# MVP Vertical Slice: Client-Server Wiring — Plan
+
+## Goal
+Prove the real Godot client and the real backend can talk: **a user can register/log in
+and see a list of worlds from the game client**. Nothing more. Gameplay, join-a-world,
+chat, avatar, Discovery search/tags/trending, Social/Economy/Trust & Safety are all
+explicitly out of scope.
+
+## Verified backend contract (as of this writing)
+- `POST /api/auth/register` — JSON body `{username, email, password, date_of_birth}`.
+  `date_of_birth` is a `YYYY-MM-DD` string. Returns `201 {access_token, token_type}`.
+  Rejects under-18 with `400`.
+- `POST /api/auth/login` — OAuth2 **form-encoded** (`application/x-www-form-urlencoded`)
+  `username` + `password` (this is NOT a JSON endpoint). Returns `{access_token, token_type}`.
+- `GET /api/worlds` — **requires auth** (`CurrentUser`), returns a JSON array of
+  `{id, name, description, visibility, owner_id, created_at}`. There is no unauthenticated
+  public-worlds path, so the worlds list screen can only be shown after login/register.
+- `GET /api/health` — unauthenticated, `{status, app}`.
+- Base URL: uvicorn default `http://127.0.0.1:8000` (must be configurable in the client).
+- CORS is irrelevant to the native Godot `HTTPRequest` client (no browser origin).
+
+## Task breakdown
+| # | Type | Task | Depends on |
+|---|------|------|-----------|
+| 1 | architecture | `ApiClient` autoload: HTTP + JWT storage + error contract | — |
+| 2 | implementation | Main-menu **login** wiring (form-encoded) | 1 |
+| 3 | implementation | Main-menu **register** wiring (JSON + age gate) | 2 |
+| 4 | implementation | **World list** screen consuming `GET /api/worlds` | 2 |
+| 5 | testing | End-to-end headless smoke test + manual verify | 1,3,4 |
+
+## Design decisions captured (resolved in task 1)
+- Token storage: in-memory singleton property for the MVP; a `save_to_disk` seam is left
+  open but not required yet (no re-login on restart in this slice).
+- Error contract: every call returns a discriminated result (`ok`/`error`) so callers
+  never crash on network failure; non-2xx surfaces `{status, detail}` from the backend.
+- Base URL: read from a ProjectSetting, defaulting to `http://127.0.0.1:8000`.
+- Login is form-encoded; register is JSON — the client helper must support both content types.

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).