Add ScriptBehavior DSL: data-driven, non-Turing-complete UGC scripting

Implements the DSL that docs/architecture/scripting_sandbox.md recommends
as the primary (and, for now, sufficient) approach in place of running
untrusted GDScript in-process: a fixed set of trigger/condition/action
verbs, expressed as plain JSON data, interpreted by trusted GDScript with
zero ability to reference engine singletons, call arbitrary methods, or
execute code.

- ScriptBehavior (scripts/scripting/script_behavior.gd): parses and
  validates rules from JSON/Dictionary data. Every trigger, condition
  type/op, and verb is checked against an explicit whitelist at parse
  time; malformed or unknown entries are dropped and recorded in
  rejected_rules, never partially executed. Carries an optional
  content_flags passthrough so this data type isn't hostile to future
  moderation-queue integration (docs/architecture/content_moderation.md).
- ScriptInterpreterNode (scripts/scripting/script_interpreter.gd): the
  only code that executes rules. Triggers: on_interact (proximity +
  "interact" input action), on_enter (edge-triggered Area3D overlap),
  on_touch (continuous overlap), on_timer (physics-clocked Timer). Verbs:
  give_item, play_sound, move, rotate, spawn_from_catalog, set_timer --
  each a fixed, hand-written function; verb dispatch is an explicit
  match(), never call()-by-name from data. move/rotate animate via Tween
  rather than teleporting.
- PlayerInventory (scripts/scripting/player_inventory.gd): a small
  per-player item-count stub for give_item to target, since no real
  inventory/entity-state system exists yet (M9 Economy). Attached to
  scenes/player.tscn as "Inventory".
- SpawnCatalog (scripts/scripting/spawn_catalog.gd): trusted catalog_id ->
  asset_id lookup for spawn_from_catalog, mirroring the AvatarCatalog
  data-driven-JSON convention. Rule data only ever supplies a catalog_id
  key, never a resource path.
- Wired a real demo ("ScriptedChest") into scenes/worlds/test_level.tscn
  with an on_interact rule (give_item + play_sound + rotate), plus an
  "interact" input action (project.godot).
- scripts/smoke_test_script_behavior.gd: exercises every trigger type,
  every verb, and every condition type against the real interpreter and
  the wired demo scene, and proves unknown/malformed/unsafe rules
  (unknown verb, unknown trigger, non-scalar smuggled arguments, etc.)
  are rejected at parse time and never run -- 50/50 checks pass.

.gitea/workflows/checkpoint.yml

@@ -0,0 +1,39 @@
+name: checkpoint
+
+# Runs the full checkpoint suite (migrations, backend pytest, Godot smoke
+# tests, multiplayer, fresh-clone boot) on every push and PR.
+#
+# Runs on a `host`-label act_runner on the AGP box: Docker, ~/godot/godot,
+# and Python 3 are already there. Deliberately uses no JavaScript actions
+# (actions/checkout etc.) so the host needs no Node install -- checkout is a
+# plain git clone from the local Gitea. See docs/ci.md.
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  checkpoint:
+    runs-on: host
+    steps:
+      - name: Checkout
+        run: |
+          set -eu
+          rm -rf repo && mkdir repo && cd repo
+          git init -q
+          git remote add origin "http://x:${{ github.token }}@localhost:3000/${{ github.repository }}.git"
+          git fetch -q --depth 1 origin "${{ github.sha }}"
+          git checkout -q FETCH_HEAD
+
+      - name: Python env
+        working-directory: repo
+        run: |
+          set -eu
+          python3 -m venv .venv
+          .venv/bin/pip install --quiet --upgrade pip
+          .venv/bin/pip install --quiet -r backend/requirements.txt
+
+      - name: Checkpoint suite
+        working-directory: repo
+        run: .venv/bin/python scripts/run_checkpoint_tests.py --postgres-port 25690 --backend-port 18690

.gitignore

@@ -0,0 +1,14 @@
+# Godot 4 editor cache/import directory
+.godot/
+
+# Godot export artifacts
+export/
+*.tmp
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Godot UID files (regenerated from path)
+*.uid
+assets/build_info.json

.godot/.gdignore

@@ -1 +0,0 @@
-

.godot/editor/filesystem_cache10

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-server.tscn::PackedScene::-1::1787259973::0::1::::<><><>0<>0<><>::
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.godot/editor/project_metadata.cfg

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

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

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

.godot/global_script_class_cache.cfg

@@ -1,9 +0,0 @@
-list=[{
-"base": &"CharacterBody3D",
-"class": &"PlayerNode",
-"icon": "",
-"is_abstract": false,
-"is_tool": false,
-"language": &"GDScript",
-"path": "res://scripts/player_spawner.gd"
-}]

assets/avatars/accessory_belt_01.glb.import

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assets/avatars/accessory_necklace_01.glb.import

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assets/avatars/base_human_male_01.glb.import

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assets/avatars/catalog.json

@@ -0,0 +1,115 @@
+{
+  "assets": {
+    "base_human_male_01": {
+      "type": "base_body",
+      "slot": "base_body",
+      "path": "res://assets/avatars/base_human_male_01.glb",
+      "version": "1.0.0",
+      "display_name": "Human Male Base"
+    },
+    "head_cyber_01": {
+      "type": "attachment",
+      "slot": "head",
+      "path": "res://assets/avatars/head_cyber_01.glb",
+      "version": "1.0.0",
+      "display_name": "Cyber Head",
+      "mount_bone": "Head"
+    },
+    "hair_mohawk_01": {
+      "type": "attachment",
+      "slot": "hair",
+      "path": "res://assets/avatars/hair_mohawk_01.glb",
+      "version": "1.0.0",
+      "display_name": "Mohawk",
+      "mount_bone": "HeadTop"
+    },
+    "hair_ponytail_01": {
+      "type": "attachment",
+      "slot": "hair",
+      "path": "res://assets/avatars/hair_ponytail_01.glb",
+      "version": "1.0.0",
+      "display_name": "Ponytail",
+      "mount_bone": "HeadTop"
+    },
+    "face_glasses_01": {
+      "type": "attachment",
+      "slot": "face",
+      "path": "res://assets/avatars/face_glasses_01.glb",
+      "version": "1.0.0",
+      "display_name": "Glasses",
+      "mount_bone": "Jaw"
+    },
+    "chest_bandit_01": {
+      "type": "attachment",
+      "slot": "chest",
+      "path": "res://assets/avatars/chest_bandit_01.glb",
+      "version": "1.0.0",
+      "display_name": "Bandit Shirt",
+      "mount_bone": "Chest"
+    },
+    "back_backpack_01": {
+      "type": "attachment",
+      "slot": "back",
+      "path": "res://assets/avatars/back_backpack_01.glb",
+      "version": "1.0.0",
+      "display_name": "Backpack",
+      "mount_bone": "Chest"
+    },
+    "pants_cargo_01": {
+      "type": "attachment",
+      "slot": "pants",
+      "path": "res://assets/avatars/pants_cargo_01.glb",
+      "version": "1.0.0",
+      "display_name": "Cargo Pants",
+      "mount_bone": "Hips"
+    },
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+      "slot": "left_hand",
+      "path": "res://assets/avatars/left_hand_glove_01.glb",
+      "version": "1.0.0",
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+      "mount_bone": "LeftHand"
+    },
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+      "slot": "right_hand",
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+      "version": "1.0.0",
+      "display_name": "Right Glove",
+      "mount_bone": "RightHand"
+    },
+    "left_foot_boot_01": {
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+      "version": "1.0.0",
+      "display_name": "Left Boot",
+      "mount_bone": "LeftFoot"
+    },
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+      "slot": "right_foot",
+      "path": "res://assets/avatars/right_foot_boot_01.glb",
+      "version": "1.0.0",
+      "display_name": "Right Boot",
+      "mount_bone": "RightFoot"
+    },
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+      "slot": "accessory",
+      "path": "res://assets/avatars/accessory_belt_01.glb",
+      "version": "1.0.0",
+      "display_name": "Belt",
+      "mount_bone": "Root"
+    },
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+      "slot": "accessory",
+      "path": "res://assets/avatars/accessory_necklace_01.glb",
+      "version": "1.0.0",
+      "display_name": "Necklace",
+      "mount_bone": "Root"
+    }
+  }
+}

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assets/avatars/head_cyber_01.glb.import

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+[params]
+
+nodes/root_type=""
+nodes/root_name=""
+nodes/root_script=null
+nodes/apply_root_scale=true
+nodes/root_scale=1.0
+nodes/import_as_skeleton_bones=false
+nodes/use_name_suffixes=true
+nodes/use_node_type_suffixes=true
+meshes/ensure_tangents=true
+meshes/generate_lods=true
+meshes/create_shadow_meshes=true
+meshes/light_baking=1
+meshes/lightmap_texel_size=0.2
+meshes/force_disable_compression=false
+skins/use_named_skins=true
+animation/import=true
+animation/fps=30
+animation/trimming=false
+animation/remove_immutable_tracks=true
+animation/import_rest_as_RESET=false
+import_script/path=""
+materials/extract=0
+materials/extract_format=0
+materials/extract_path=""
+_subresources={}
+gltf/naming_version=2
+gltf/embedded_image_handling=1

assets/avatars/left_foot_boot_01.glb.import

@@ -0,0 +1,42 @@
+[remap]
+
+importer="scene"
+importer_version=1
+type="PackedScene"
+uid="uid://bgfjpdu8kg0aj"
+path="res://.godot/imported/left_foot_boot_01.glb-cab36c9e44befe0a3ff50ee651f2ff67.scn"
+
+[deps]
+
+source_file="res://assets/avatars/left_foot_boot_01.glb"
+dest_files=["res://.godot/imported/left_foot_boot_01.glb-cab36c9e44befe0a3ff50ee651f2ff67.scn"]
+
+[params]
+
+nodes/root_type=""
+nodes/root_name=""
+nodes/root_script=null
+nodes/apply_root_scale=true
+nodes/root_scale=1.0
+nodes/import_as_skeleton_bones=false
+nodes/use_name_suffixes=true
+nodes/use_node_type_suffixes=true
+meshes/ensure_tangents=true
+meshes/generate_lods=true
+meshes/create_shadow_meshes=true
+meshes/light_baking=1
+meshes/lightmap_texel_size=0.2
+meshes/force_disable_compression=false
+skins/use_named_skins=true
+animation/import=true
+animation/fps=30
+animation/trimming=false
+animation/remove_immutable_tracks=true
+animation/import_rest_as_RESET=false
+import_script/path=""
+materials/extract=0
+materials/extract_format=0
+materials/extract_path=""
+_subresources={}
+gltf/naming_version=2
+gltf/embedded_image_handling=1

assets/avatars/left_hand_glove_01.glb.import

@@ -0,0 +1,42 @@
+[remap]
+
+importer="scene"
+importer_version=1
+type="PackedScene"
+uid="uid://dtq7tgio1iymd"
+path="res://.godot/imported/left_hand_glove_01.glb-4b237bea3299c6604547afa353a7b602.scn"
+
+[deps]
+
+source_file="res://assets/avatars/left_hand_glove_01.glb"
+dest_files=["res://.godot/imported/left_hand_glove_01.glb-4b237bea3299c6604547afa353a7b602.scn"]
+
+[params]
+
+nodes/root_type=""
+nodes/root_name=""
+nodes/root_script=null
+nodes/apply_root_scale=true
+nodes/root_scale=1.0
+nodes/import_as_skeleton_bones=false
+nodes/use_name_suffixes=true
+nodes/use_node_type_suffixes=true
+meshes/ensure_tangents=true
+meshes/generate_lods=true
+meshes/create_shadow_meshes=true
+meshes/light_baking=1
+meshes/lightmap_texel_size=0.2
+meshes/force_disable_compression=false
+skins/use_named_skins=true
+animation/import=true
+animation/fps=30
+animation/trimming=false
+animation/remove_immutable_tracks=true
+animation/import_rest_as_RESET=false
+import_script/path=""
+materials/extract=0
+materials/extract_format=0
+materials/extract_path=""
+_subresources={}
+gltf/naming_version=2
+gltf/embedded_image_handling=1

assets/avatars/pants_cargo_01.glb.import

@@ -0,0 +1,42 @@
+[remap]
+
+importer="scene"
+importer_version=1
+type="PackedScene"
+uid="uid://yo204q1m6hs3"
+path="res://.godot/imported/pants_cargo_01.glb-00f3e3b72fd692344cbb8bfd2b8449f9.scn"
+
+[deps]
+
+source_file="res://assets/avatars/pants_cargo_01.glb"
+dest_files=["res://.godot/imported/pants_cargo_01.glb-00f3e3b72fd692344cbb8bfd2b8449f9.scn"]
+
+[params]
+
+nodes/root_type=""
+nodes/root_name=""
+nodes/root_script=null
+nodes/apply_root_scale=true
+nodes/root_scale=1.0
+nodes/import_as_skeleton_bones=false
+nodes/use_name_suffixes=true
+nodes/use_node_type_suffixes=true
+meshes/ensure_tangents=true
+meshes/generate_lods=true
+meshes/create_shadow_meshes=true
+meshes/light_baking=1
+meshes/lightmap_texel_size=0.2
+meshes/force_disable_compression=false
+skins/use_named_skins=true
+animation/import=true
+animation/fps=30
+animation/trimming=false
+animation/remove_immutable_tracks=true
+animation/import_rest_as_RESET=false
+import_script/path=""
+materials/extract=0
+materials/extract_format=0
+materials/extract_path=""
+_subresources={}
+gltf/naming_version=2
+gltf/embedded_image_handling=1

assets/avatars/right_foot_boot_01.glb.import

@@ -0,0 +1,42 @@
+[remap]
+
+importer="scene"
+importer_version=1
+type="PackedScene"
+uid="uid://30ij0eapm6ti"
+path="res://.godot/imported/right_foot_boot_01.glb-ffff27e561e5632596b7ba89fee5b5ea.scn"
+
+[deps]
+
+source_file="res://assets/avatars/right_foot_boot_01.glb"
+dest_files=["res://.godot/imported/right_foot_boot_01.glb-ffff27e561e5632596b7ba89fee5b5ea.scn"]
+
+[params]
+
+nodes/root_type=""
+nodes/root_name=""
+nodes/root_script=null
+nodes/apply_root_scale=true
+nodes/root_scale=1.0
+nodes/import_as_skeleton_bones=false
+nodes/use_name_suffixes=true
+nodes/use_node_type_suffixes=true
+meshes/ensure_tangents=true
+meshes/generate_lods=true
+meshes/create_shadow_meshes=true
+meshes/light_baking=1
+meshes/lightmap_texel_size=0.2
+meshes/force_disable_compression=false
+skins/use_named_skins=true
+animation/import=true
+animation/fps=30
+animation/trimming=false
+animation/remove_immutable_tracks=true
+animation/import_rest_as_RESET=false
+import_script/path=""
+materials/extract=0
+materials/extract_format=0
+materials/extract_path=""
+_subresources={}
+gltf/naming_version=2
+gltf/embedded_image_handling=1

assets/avatars/right_hand_glove_01.glb.import

@@ -0,0 +1,42 @@
+[remap]
+
+importer="scene"
+importer_version=1
+type="PackedScene"
+uid="uid://bcrtxtp47dv8h"
+path="res://.godot/imported/right_hand_glove_01.glb-a59875b630ac413350c3bdf6acc84bdf.scn"
+
+[deps]
+
+source_file="res://assets/avatars/right_hand_glove_01.glb"
+dest_files=["res://.godot/imported/right_hand_glove_01.glb-a59875b630ac413350c3bdf6acc84bdf.scn"]
+
+[params]
+
+nodes/root_type=""
+nodes/root_name=""
+nodes/root_script=null
+nodes/apply_root_scale=true
+nodes/root_scale=1.0
+nodes/import_as_skeleton_bones=false
+nodes/use_name_suffixes=true
+nodes/use_node_type_suffixes=true
+meshes/ensure_tangents=true
+meshes/generate_lods=true
+meshes/create_shadow_meshes=true
+meshes/light_baking=1
+meshes/lightmap_texel_size=0.2
+meshes/force_disable_compression=false
+skins/use_named_skins=true
+animation/import=true
+animation/fps=30
+animation/trimming=false
+animation/remove_immutable_tracks=true
+animation/import_rest_as_RESET=false
+import_script/path=""
+materials/extract=0
+materials/extract_format=0
+materials/extract_path=""
+_subresources={}
+gltf/naming_version=2
+gltf/embedded_image_handling=1

assets/scripting/behaviors/demo_chest.json

@@ -0,0 +1,17 @@
+{
+  "content_flags": {
+    "violence": "none",
+    "mature": false
+  },
+  "rules": [
+    {
+      "trigger": {"type": "on_interact"},
+      "conditions": [],
+      "actions": [
+        {"verb": "give_item", "item_id": "gold_coin", "count": 3},
+        {"verb": "play_sound", "sound_id": "chest_open"},
+        {"verb": "rotate", "target": "self", "degrees": 90, "axis": "y", "duration": 0.4}
+      ]
+    }
+  ]
+}

assets/scripting/spawn_catalog.json

@@ -0,0 +1,8 @@
+{
+  "templates": {
+    "small_crate": {
+      "asset_id": "props/crate_small.glb",
+      "display_name": "Small Crate"
+    }
+  }
+}

backend/.env.example

@@ -0,0 +1,23 @@
+# Database (async driver)
+DATABASE_URL=postgresql+asyncpg://agp_user:agp_password@localhost:5432/agp_db
+
+# Redis
+REDIS_URL=redis://localhost:6379/0
+
+# JWT / Auth
+ALGORITHM=RS256
+ACCESS_TOKEN_EXPIRE_MINUTES=60
+REFRESH_TOKEN_EXPIRE_DAYS=30
+# Directory where the RSA keypair is loaded/generated at runtime.
+# Defaults to ~/.agp/keys (outside the repo). Keys are never committed to git.
+RSA_KEY_DIR=~/.agp/keys
+
+# App
+APP_NAME=AGP Backend
+APP_VERSION=0.1.0
+DEBUG=true
+CORS_ORIGINS=http://localhost:8080,http://localhost:3000
+
+# File uploads
+UPLOAD_DIR=uploads
+MAX_UPLOAD_SIZE_MB=100

backend/.gitignore

@@ -0,0 +1,4 @@
+.env
+__pycache__/
+*.pyc
+.venv/

backend/alembic.ini

@@ -0,0 +1,42 @@
+# Alembic configuration file.
+# Run: alembic upgrade head  (to apply migrations)
+# Run: alembic revision --autogenerate -m "description"  (to generate migration)
+
+[alembic]
+script_location = alembic
+prepend_sys_path = .
+sqlalchemy.url = postgresql+asyncpg://agp_user:agp_password@localhost:5432/agp_db
+
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

backend/alembic/env.py

@@ -0,0 +1,65 @@
+"""Alembic environment configuration."""
+
+import asyncio
+from logging.config import fileConfig
+
+from alembic import context
+from sqlalchemy.ext.asyncio import create_async_engine
+
+from app.config import settings
+from app.database import Base
+from app.models import user, session, world, asset, avatar_loadout  # noqa: F401
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+target_metadata = Base.metadata
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode."""
+    url = settings.DATABASE_URL
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def do_run_migrations(connection):
+    context.configure(connection=connection, target_metadata=target_metadata)
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+async def run_async_migrations():
+    """Run migrations in 'online' mode with async engine."""
+    connectable = create_async_engine(settings.DATABASE_URL, echo=False)
+
+    async with connectable.connect() as connection:
+        await connection.run_sync(do_run_migrations)
+
+    await connectable.dispose()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode."""
+    asyncio.run(run_async_migrations())
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

backend/alembic/script.py.mako

@@ -0,0 +1,27 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    """Upgrade database schema."""
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    """Downgrade database schema."""
+    ${downgrades if downgrades else "pass"}

backend/alembic/versions/0001_initial.py

@@ -0,0 +1,127 @@
+"""initial schema
+
+Revision ID: 0001_initial
+Revises:
+Create Date: 2024-01-01 00:00:00.000000
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+# revision identifiers, used by Alembic.
+revision: str = "0001_initial"
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Upgrade database schema."""
+    # Create ENUM types
+    world_visibility = postgresql.ENUM(
+        "public", "private", "friends_only", name="world_visibility"
+    )
+    world_visibility.create(op.get_bind(), checkfirst=True)
+
+    asset_type = postgresql.ENUM(
+        "image", "audio", "video", "document", "model_3d", "other", name="asset_type"
+    )
+    asset_type.create(op.get_bind(), checkfirst=True)
+
+    # Create users table
+    op.create_table(
+        "users",
+        sa.Column("id", sa.Integer(), primary_key=True),
+        sa.Column("username", sa.String(length=50), nullable=False),
+        sa.Column("email", sa.String(length=120), nullable=False),
+        sa.Column("hashed_password", sa.String(length=255), nullable=False),
+        sa.Column("is_active", sa.Boolean(), nullable=True),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now()),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=True),
+    )
+    op.create_index(op.f("ix_users_email"), "users", ["email"], unique=True)
+    op.create_index(op.f("ix_users_id"), "users", ["id"], unique=False)
+    op.create_index(op.f("ix_users_username"), "users", ["username"], unique=True)
+
+    # Create sessions table
+    op.create_table(
+        "sessions",
+        sa.Column("id", sa.String(length=36), primary_key=True),
+        sa.Column("user_id", sa.Integer(), nullable=False),
+        sa.Column("token", sa.String(), nullable=False),
+        sa.Column("expires_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("is_active", sa.Boolean(), nullable=True),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now()),
+        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now()),
+        sa.ForeignKeyConstraint(["user_id"], ["users.id"], ondelete="CASCADE"),
+    )
+    op.create_index(op.f("ix_sessions_token"), "sessions", ["token"], unique=True)
+
+    # Create worlds table
+    op.create_table(
+        "worlds",
+        sa.Column("id", sa.Integer(), primary_key=True),
+        sa.Column("name", sa.String(length=255), nullable=False),
+        sa.Column("description", sa.Text(), nullable=True),
+        sa.Column("owner_id", sa.Integer(), nullable=False),
+        sa.Column(
+            "visibility",
+            postgresql.ENUM(
+                "public", "private", "friends_only", name="world_visibility",
+                create_type=False,
+            ),
+            nullable=True,
+        ),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now()),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=True),
+        sa.ForeignKeyConstraint(["owner_id"], ["users.id"]),
+    )
+    op.create_index(op.f("ix_worlds_id"), "worlds", ["id"], unique=False)
+
+    # Create assets table
+    op.create_table(
+        "assets",
+        sa.Column("id", sa.Integer(), primary_key=True),
+        sa.Column("name", sa.String(length=255), nullable=False),
+        sa.Column("description", sa.Text(), nullable=True),
+        sa.Column(
+            "asset_type",
+            postgresql.ENUM(
+                "image", "audio", "video", "document", "model_3d", "other",
+                name="asset_type", create_type=False,
+            ),
+            nullable=False,
+        ),
+        sa.Column("file_path", sa.String(length=512), nullable=False),
+        sa.Column("file_size", sa.Integer(), nullable=True),
+        sa.Column("mime_type", sa.String(length=128), nullable=True),
+        sa.Column("metadata_json", sa.Text(), nullable=True),
+        sa.Column("world_id", sa.Integer(), nullable=True),
+        sa.Column("owner_id", sa.Integer(), nullable=False),
+        sa.Column("is_public", sa.Boolean(), nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now()),
+        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now()),
+        sa.ForeignKeyConstraint(["owner_id"], ["users.id"]),
+        sa.ForeignKeyConstraint(["world_id"], ["worlds.id"]),
+    )
+    op.create_index(op.f("ix_assets_id"), "assets", ["id"], unique=False)
+
+
+def downgrade() -> None:
+    """Downgrade database schema."""
+    op.drop_index(op.f("ix_assets_id"), table_name="assets")
+    op.drop_table("assets")
+    op.drop_index(op.f("ix_worlds_id"), table_name="worlds")
+    op.drop_table("worlds")
+    op.drop_index(op.f("ix_sessions_token"), table_name="sessions")
+    op.drop_table("sessions")
+    op.drop_index(op.f("ix_users_username"), table_name="users")
+    op.drop_index(op.f("ix_users_id"), table_name="users")
+    op.drop_index(op.f("ix_users_email"), table_name="users")
+    op.drop_table("users")
+
+    # Drop ENUM types
+    postgresql.ENUM(name="asset_type").drop(op.get_bind(), checkfirst=True)
+    postgresql.ENUM(name="world_visibility").drop(op.get_bind(), checkfirst=True)

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/alembic/versions/0003_add_refresh_tokens_table.py

@@ -0,0 +1,36 @@
+"""add refresh_tokens table
+
+Revision ID: 0003_add_refresh_tokens_table
+Revises: 0002_add_date_of_birth_to_users
+Create Date: 2025-07-25 00:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision: str = "0003_add_refresh_tokens_table"
+down_revision: Union[str, None] = "0002_add_date_of_birth_to_users"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Create the refresh_tokens table."""
+    op.create_table(
+        "refresh_tokens",
+        sa.Column("id", sa.String(36), primary_key=True),
+        sa.Column("user_id", sa.Integer(), sa.ForeignKey("users.id", ondelete="CASCADE"), nullable=False),
+        sa.Column("token", sa.String(512), unique=True, index=True, nullable=False),
+        sa.Column("expires_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("is_active", sa.Boolean(), server_default=sa.text("true"), nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+    )
+
+
+def downgrade() -> None:
+    """Drop the refresh_tokens table."""
+    op.drop_table("refresh_tokens")

backend/alembic/versions/0004_add_avatar_loadouts_table.py

@@ -0,0 +1,39 @@
+"""add avatar_loadouts table
+
+Revision ID: 0004_add_avatar_loadouts_table
+Revises: 0003_add_refresh_tokens_table
+Create Date: 2026-09-05 00:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+# revision identifiers, used by Alembic.
+revision: str = "0004_add_avatar_loadouts_table"
+down_revision: Union[str, None] = "0003_add_refresh_tokens_table"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Create the avatar_loadouts table (one row per user)."""
+    op.create_table(
+        "avatar_loadouts",
+        sa.Column(
+            "user_id",
+            sa.Integer(),
+            sa.ForeignKey("users.id", ondelete="CASCADE"),
+            primary_key=True,
+        ),
+        sa.Column("data", postgresql.JSONB(), nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+    )
+
+
+def downgrade() -> None:
+    """Drop the avatar_loadouts table."""
+    op.drop_table("avatar_loadouts")

backend/app/config.py

@@ -0,0 +1,152 @@
+"""Application configuration via pydantic-settings."""
+
+from functools import lru_cache
+from pathlib import Path
+
+from cryptography.hazmat.primitives.asymmetric.rsa import (
+    RSAPrivateKey,
+    RSAPublicKey,
+    generate_private_key,
+)
+from cryptography.hazmat.primitives.serialization import (
+    Encoding,
+    NoEncryption,
+    PrivateFormat,
+    PublicFormat,
+    load_pem_private_key,
+    load_pem_public_key,
+)
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+def _load_or_generate_rsa_keys(key_dir: Path) -> tuple[bytes, bytes]:
+    """Load existing RSA keys or generate a new pair.
+
+    Keys are stored as PEM files in *key_dir*.  The directory is created
+    if it does not exist.  Files are named ``private.pem`` and
+    ``public.pem`` and are **not** committed to git.
+    """
+    private_path = key_dir / "private.pem"
+    public_path = key_dir / "public.pem"
+
+    if private_path.exists() and public_path.exists():
+        private_pem = private_path.read_bytes()
+        public_pem = public_path.read_bytes()
+    else:
+        # Generate a new 2048-bit RSA key pair
+        private_key = generate_private_key(public_exponent=65537, key_size=2048)
+        private_pem = private_key.private_bytes(
+            Encoding.PEM,
+            PrivateFormat.PKCS8,
+            NoEncryption(),
+        )
+        public_pem = private_key.public_key().public_bytes(
+            Encoding.PEM,
+            PublicFormat.SubjectPublicKeyInfo,
+        )
+        key_dir.mkdir(parents=True, exist_ok=True)
+        private_path.write_bytes(private_pem)
+        public_path.write_bytes(public_pem)
+
+    return private_pem, public_pem
+
+
+class Settings(BaseSettings):
+    # App
+    APP_NAME: str = "AGP Backend"
+    APP_VERSION: str = "0.1.0"
+    DEBUG: bool = True
+
+    # Database (async)
+    DATABASE_URL: str = "postgresql+asyncpg://agp_user:agp_password@localhost:5432/agp_db"
+
+    # Redis
+    REDIS_URL: str = "redis://localhost:6379/0"
+
+    # JWT / Auth
+    ALGORITHM: str = "RS256"
+    ACCESS_TOKEN_EXPIRE_MINUTES: int = 60
+    REFRESH_TOKEN_EXPIRE_DAYS: int = 30
+
+    # RS256 key storage.  Defaults to a directory outside the repo so the
+    # generated keypair is never accidentally committed.
+    RSA_KEY_DIR: str = str(Path.home() / ".agp" / "keys")
+
+    # CORS
+    CORS_ORIGINS: str = "http://localhost:8080,http://localhost:3000"
+
+    # Per-IP auth rate limiting (app/rate_limit.py). Disabled by the
+    # checkpoint smoke suite, which runs every test from one client IP.
+    RATE_LIMIT_ENABLED: bool = True
+
+    # File uploads
+    UPLOAD_DIR: str = "uploads"
+    MAX_UPLOAD_SIZE_MB: int = 100
+    GLTF_MAX_FILE_SIZE_MB: int = 200
+
+    # ── Game-server orchestration ──────────────────────────────────────────
+    # The join flow (POST /api/worlds/{id}/join) ensures a headless Godot
+    # dedicated-server process exists for a world and returns its address.
+    # Disabled by default so nothing tries to spawn Godot in environments
+    # that don't have it (plain pytest, CI without the engine); the
+    # checkpoint/playtest launcher turns it on.
+    GAME_SERVERS_ENABLED: bool = False
+    # Path to the Godot 4 binary. "godot" resolves via PATH.
+    GODOT_BIN: str = str(Path.home() / "godot" / "godot")
+    # Godot project directory (the game repo root -- backend/ is a subdir).
+    GAME_PROJECT_DIR: str = str(Path(__file__).resolve().parents[2])
+    # The host clients should connect to for ENet. Defaults to the LAN IP the
+    # launcher bakes into the exe; overridable for local testing.
+    GAME_SERVER_HOST: str = "127.0.0.1"
+    # Port range for per-world dedicated servers.
+    GAME_SERVER_PORT_MIN: int = 27000
+    GAME_SERVER_PORT_MAX: int = 27099
+    # Kill a world's server this long after its last join with no active
+    # players reported.
+    GAME_SERVER_IDLE_TIMEOUT_SECONDS: int = 300
+
+    model_config = SettingsConfigDict(
+        env_file=".env",
+        env_file_encoding="utf-8",
+        case_sensitive=True,
+    )
+
+    @property
+    def cors_origins_list(self) -> list[str]:
+        return [origin.strip() for origin in self.CORS_ORIGINS.split(",")]
+
+    @property
+    def rsa_key_dir(self) -> Path:
+        return Path(self.RSA_KEY_DIR)
+
+    @property
+    def private_pem(self) -> bytes:
+        """Return the private key PEM bytes (loads/generates on first call)."""
+        private_pem, _ = _load_or_generate_rsa_keys(self.rsa_key_dir)
+        return private_pem
+
+    @property
+    def public_pem(self) -> bytes:
+        """Return the public key PEM bytes (loads/generates on first call)."""
+        _, public_pem = _load_or_generate_rsa_keys(self.rsa_key_dir)
+        return public_pem
+
+    @property
+    def private_key(self) -> RSAPrivateKey:
+        """Return the deserialized RSA private key object."""
+        return load_pem_private_key(self.private_pem, password=None)
+
+    @property
+    def public_key(self) -> RSAPublicKey:
+        """Return the deserialized RSA public key object."""
+        return load_pem_public_key(self.public_pem)
+
+
+@lru_cache()
+def get_settings() -> Settings:
+    """Return cached settings instance."""
+    return Settings()
+
+
+# Convenience singleton
+settings = get_settings()

backend/app/database.py

@@ -0,0 +1,42 @@
+"""Async database engine and session factory."""
+
+from sqlalchemy.ext.asyncio import (
+    AsyncSession,
+    async_sessionmaker,
+    create_async_engine,
+)
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import settings
+
+engine = create_async_engine(
+    settings.DATABASE_URL,
+    echo=settings.DEBUG,
+    pool_size=10,
+    max_overflow=20,
+)
+
+async_session_factory = async_sessionmaker(
+    engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+async def get_db() -> AsyncSession:
+    """Dependency that yields an async database session.
+
+    Handlers are responsible for committing or rolling back their own
+    transactions.  This avoids the double-commit problem where the
+    session is committed both here and in the handler.
+    """
+    async with async_session_factory() as session:
+        try:
+            yield session
+        except Exception:
+            await session.rollback()
+            raise

backend/app/dependencies.py

@@ -0,0 +1,55 @@
+"""Shared FastAPI dependencies, including JWT-based auth."""
+
+from typing import Annotated
+
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from jose import JWTError, jwt
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.config import settings
+from app.database import get_db
+from app.models.user import User
+
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/auth/login")
+
+
+async def get_current_user(
+    token: Annotated[str, Depends(oauth2_scheme)],
+    db: Annotated[AsyncSession, Depends(get_db)],
+) -> User:
+    """Resolve the JWT bearer token to a User, or raise 401."""
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Could not validate credentials",
+        headers={"WWW-Authenticate": "Bearer"},
+    )
+    try:
+        payload = jwt.decode(
+            token, settings.public_pem, algorithms=[settings.ALGORITHM]
+        )
+        user_id: str | None = payload.get("sub")
+        if user_id is None:
+            raise credentials_exception
+    except JWTError:
+        raise credentials_exception
+
+    try:
+        user_id_int = int(user_id)
+    except (ValueError, TypeError):
+        raise credentials_exception
+
+    result = await db.execute(select(User).where(User.id == user_id_int))
+    user = result.scalar_one_or_none()
+    if user is None:
+        raise credentials_exception
+    if not user.is_active:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="User account is inactive",
+        )
+    return user
+
+
+CurrentUser = Annotated[User, Depends(get_current_user)]

backend/app/main.py

@@ -0,0 +1,50 @@
+"""FastAPI application entry point."""
+
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+
+from app.config import settings
+from app.routers import auth, users, worlds, assets, avatar
+
+
+from app.services.game_servers import supervisor
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    """Application lifespan: startup and shutdown events."""
+    supervisor.start()
+    yield
+    await supervisor.shutdown()
+
+
+app = FastAPI(
+    title=settings.APP_NAME,
+    version=settings.APP_VERSION,
+    description="Agentic Game Platform - Backend API",
+    lifespan=lifespan,
+)
+
+# CORS
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=settings.cors_origins_list,
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+# Include routers
+app.include_router(auth.router, prefix="/api/auth", tags=["auth"])
+app.include_router(users.router, prefix="/api/users", tags=["users"])
+app.include_router(worlds.router, prefix="/api/worlds", tags=["worlds"])
+app.include_router(assets.router, prefix="/api/assets", tags=["assets"])
+app.include_router(avatar.router, prefix="/api/avatar", tags=["avatar"])
+
+
+@app.get("/api/health")
+async def health_check():
+    """Simple health check endpoint."""
+    return {"status": "ok", "app": settings.APP_NAME}

backend/app/models/__init__.py

@@ -0,0 +1,7 @@
+from app.models.user import User
+from app.models.session import Session
+from app.models.world import World
+from app.models.asset import Asset
+from app.models.avatar_loadout import AvatarLoadout
+
+__all__ = ["User", "Session", "World", "Asset", "AvatarLoadout"]

backend/app/models/asset.py

@@ -0,0 +1,40 @@
+from sqlalchemy import Column, Integer, String, ForeignKey, Text, DateTime, Boolean
+from sqlalchemy.dialects.postgresql import ENUM
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+import enum
+
+from app.database import Base
+
+
+class AssetType(str, enum.Enum):
+    IMAGE = "image"
+    AUDIO = "audio"
+    VIDEO = "video"
+    DOCUMENT = "document"
+    MODEL_3D = "model_3d"
+    OTHER = "other"
+
+
+class Asset(Base):
+    __tablename__ = "assets"
+
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String(255), nullable=False)
+    description = Column(Text, nullable=True)
+    asset_type = Column(
+        ENUM(AssetType, name="asset_type", create_type=False),
+        nullable=False,
+    )
+    file_path = Column(String(512), nullable=False)
+    file_size = Column(Integer, nullable=True)
+    mime_type = Column(String(128), nullable=True)
+    metadata_json = Column(Text, nullable=True)
+    world_id = Column(Integer, ForeignKey("worlds.id"), nullable=True)
+    owner_id = Column(Integer, ForeignKey("users.id"), nullable=False)
+    is_public = Column(Boolean, default=False, nullable=False)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
+
+    owner = relationship("User", back_populates="assets")
+    world = relationship("World", back_populates="assets")

backend/app/models/avatar_loadout.py

@@ -0,0 +1,41 @@
+from sqlalchemy import Column, Integer, ForeignKey, DateTime
+from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+# The default a brand-new account gets before they touch the customization
+# screen. Kept in sync with assets/avatars/catalog.json (the base_body id) and
+# with the client's AvatarLoadout.to_json() shape.
+DEFAULT_LOADOUT: dict = {
+    "base_body": "base_human_male_01",
+    "slots": {},
+}
+
+
+class AvatarLoadout(Base):
+    """A user's equipped avatar composition.
+
+    One row per user. The whole loadout is stored as a single JSON document
+    matching the client's ``AvatarLoadout.to_json()`` shape
+    (``{"base_body": str, "slots": {...}, "skin_tone"?: {...}}``) rather than
+    exploded into columns -- the server has no copy of the asset catalog, so
+    deep validation (does this asset exist, is it valid for this slot) stays
+    on the client. The server only enforces the envelope: valid JSON object
+    with a non-empty ``base_body``.
+    """
+
+    __tablename__ = "avatar_loadouts"
+
+    user_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        primary_key=True,
+    )
+    data = Column(JSONB, nullable=False)
+    created_at = Column(DateTime(timezone=True), server_default=func.now(), nullable=False)
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False)
+
+    user = relationship("User", back_populates="avatar_loadout")

backend/app/models/session.py

@@ -0,0 +1,41 @@
+import uuid
+
+from sqlalchemy import Column, Integer, String, DateTime, ForeignKey, Boolean
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class Session(Base):
+    __tablename__ = "sessions"
+
+    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+    token = Column(String, unique=True, index=True, nullable=False)
+    expires_at = Column(DateTime(timezone=True), nullable=False)
+    is_active = Column(Boolean, default=True)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
+
+    user = relationship("User", back_populates="sessions")
+
+
+class RefreshToken(Base):
+    __tablename__ = "refresh_tokens"
+
+    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+    # RS256 JWTs are ~420+ chars; 512 is sufficient and matches the migration.
+    token = Column(String(512), unique=True, index=True, nullable=False)
+    expires_at = Column(DateTime(timezone=True), nullable=False)
+    is_active = Column(Boolean, nullable=False, default=True, server_default="true")
+    created_at = Column(DateTime(timezone=True), nullable=False, server_default=func.now())
+    updated_at = Column(
+        DateTime(timezone=True),
+        nullable=False,
+        server_default=func.now(),
+        onupdate=func.now(),
+    )
+
+    user = relationship("User", back_populates="refresh_tokens")

backend/app/models/user.py

@@ -0,0 +1,44 @@
+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
+
+from app.database import Base
+
+
+class User(Base):
+    __tablename__ = "users"
+
+    id = Column(Integer, primary_key=True, index=True)
+    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())
+
+    sessions = relationship("Session", back_populates="user", cascade="all, delete-orphan")
+    refresh_tokens = relationship("RefreshToken", back_populates="user", cascade="all, delete-orphan")
+    worlds = relationship("World", back_populates="owner")
+    assets = relationship("Asset", back_populates="owner")
+    avatar_loadout = relationship(
+        "AvatarLoadout",
+        back_populates="user",
+        uselist=False,
+        cascade="all, delete-orphan",
+    )
+
+    @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/models/world.py

@@ -0,0 +1,36 @@
+from sqlalchemy import Column, Integer, String, Text, DateTime, ForeignKey
+from sqlalchemy.dialects.postgresql import ENUM
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+import enum
+
+from app.database import Base
+
+
+class WorldVisibility(enum.Enum):
+    PUBLIC = "public"
+    PRIVATE = "private"
+    FRIENDS_ONLY = "friends_only"
+
+
+class World(Base):
+    __tablename__ = "worlds"
+
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String(255), nullable=False)
+    description = Column(Text, nullable=True)
+    owner_id = Column(Integer, ForeignKey("users.id"), nullable=False)
+    visibility = Column(
+        ENUM(
+            WorldVisibility,
+            name="world_visibility",
+            create_type=False,
+            values_callable=lambda enum_cls: [e.value for e in enum_cls],
+        ),
+        default=WorldVisibility.PUBLIC,
+    )
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
+
+    owner = relationship("User", back_populates="worlds")
+    assets = relationship("Asset", back_populates="world", cascade="all, delete-orphan")

backend/app/rate_limit.py

@@ -0,0 +1,73 @@
+"""Lightweight in-process rate limiting.
+
+The backend runs single-worker (required by the game-server supervisor), so a
+process-local sliding-window counter is sufficient and needs no Redis. Keyed
+by client IP. Used to blunt credential brute-force on the auth endpoints.
+
+If the backend is ever scaled to multiple workers/hosts this must move to a
+shared store (Redis) -- flagged here rather than silently under-enforcing.
+"""
+from __future__ import annotations
+
+import time
+from collections import defaultdict, deque
+
+from fastapi import HTTPException, Request, status
+
+from app.config import settings
+
+
+class SlidingWindowLimiter:
+    def __init__(self, max_hits: int, window_seconds: float) -> None:
+        self.max_hits = max_hits
+        self.window = window_seconds
+        self._hits: dict[str, deque[float]] = defaultdict(deque)
+
+    def check(self, key: str) -> None:
+        now = time.monotonic()
+        q = self._hits[key]
+        cutoff = now - self.window
+        while q and q[0] < cutoff:
+            q.popleft()
+        if len(q) >= self.max_hits:
+            retry = max(1, int(q[0] + self.window - now))
+            raise HTTPException(
+                status_code=status.HTTP_429_TOO_MANY_REQUESTS,
+                detail="Too many attempts. Try again shortly.",
+                headers={"Retry-After": str(retry)},
+            )
+        q.append(now)
+
+    def reset(self) -> None:
+        self._hits.clear()
+
+
+def _client_key(request: Request) -> str:
+    # X-Forwarded-For first hop when behind the reverse proxy, else the socket.
+    fwd = request.headers.get("x-forwarded-for", "")
+    if fwd:
+        return fwd.split(",")[0].strip()
+    return request.client.host if request.client else "unknown"
+
+
+# 10 auth attempts / minute / IP -- generous for a human, painful for a
+# brute-forcer.
+_auth_limiter = SlidingWindowLimiter(max_hits=10, window_seconds=60)
+
+
+async def auth_rate_limit(request: Request) -> None:
+    """FastAPI dependency: rate-limit auth attempts per client IP.
+
+    A no-op when ``RATE_LIMIT_ENABLED`` is false -- the checkpoint smoke
+    suite runs every test against one backend from one client IP, so the
+    per-IP cap would trip mid-suite. The dedicated ``test_rate_limit``
+    module exercises the real behaviour regardless of this flag.
+    """
+    if not settings.RATE_LIMIT_ENABLED:
+        return
+    _auth_limiter.check(f"auth:{_client_key(request)}")
+
+
+def reset_all() -> None:
+    """Test hook."""
+    _auth_limiter.reset()

backend/app/routers/assets.py

@@ -0,0 +1,243 @@
+"""Asset management router."""
+
+import json
+import os
+from pathlib import Path
+from typing import Optional
+
+from fastapi import APIRouter, Depends, HTTPException, UploadFile, File, Query
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.config import settings
+from app.database import get_db
+from app.dependencies import CurrentUser
+from app.models.asset import Asset, AssetType
+from app.models.world import World
+from app.services import gltf as gltf_service
+from pydantic import BaseModel, Field
+
+router = APIRouter()
+
+
+# --- Pydantic schemas ---
+
+class AssetCreate(BaseModel):
+    """Schema for creating an asset reference."""
+    name: str = Field(..., min_length=1, max_length=255)
+    description: Optional[str] = None
+    asset_type: AssetType
+    world_id: Optional[int] = None
+
+
+class AssetResponse(BaseModel):
+    """Schema for asset responses."""
+    id: int
+    name: str
+    description: Optional[str]
+    asset_type: AssetType
+    file_path: str
+    file_size: Optional[int]
+    mime_type: Optional[str]
+    world_id: Optional[int]
+    owner_id: int
+    is_public: bool
+    created_at: str
+    updated_at: str
+
+    model_config = {"from_attributes": True}
+
+
+class AssetUpdate(BaseModel):
+    """Schema for updating an asset."""
+    name: Optional[str] = None
+    description: Optional[str] = None
+    is_public: Optional[bool] = None
+
+
+# --- Helpers ---
+
+def _sanitize_filename(filename: str) -> str:
+    """Strip path components and unsafe characters from a filename."""
+    # Remove any directory components (path traversal protection).
+    base = os.path.basename(filename.replace("\\", "/"))
+    # Keep only safe characters.
+    safe = "".join(c for c in base if c.isalnum() or c in "._-")
+    return safe or "file"
+
+
+def _detect_asset_type(filename: Optional[str], content: bytes) -> AssetType:
+    """Detect the asset type from filename and content."""
+    if filename and gltf_service.looks_like_gltf(content, filename):
+        return AssetType.MODEL_3D
+    # Fallback: let the caller decide based on mime_type or default.
+    return AssetType.OTHER
+
+
+# --- Endpoints ---
+
+@router.post("/", response_model=AssetResponse, status_code=201)
+async def create_asset(
+    payload: AssetCreate,
+    current_user: CurrentUser,
+    db: AsyncSession = Depends(get_db),
+):
+    """Create a new asset reference."""
+    # Verify world ownership if world_id is provided
+    if payload.world_id is not None:
+        world = await db.get(World, payload.world_id)
+        if world is None:
+            raise HTTPException(status_code=404, detail="World not found")
+        if world.owner_id != current_user.id:
+            raise HTTPException(status_code=403, detail="Not owner of this world")
+
+    asset = Asset(
+        name=payload.name,
+        description=payload.description,
+        asset_type=payload.asset_type,
+        file_path="",  # Will be set after upload
+        owner_id=current_user.id,
+        world_id=payload.world_id,
+        is_public=False,
+    )
+    db.add(asset)
+    await db.commit()
+    await db.refresh(asset)
+    return asset
+
+
+@router.get("/", response_model=list[AssetResponse])
+async def list_assets(
+    current_user: CurrentUser,
+    world_id: Optional[int] = Query(None, description="Filter by world"),
+    asset_type: Optional[AssetType] = Query(None),
+    limit: int = Query(50, ge=1, le=100),
+    offset: int = Query(0, ge=0),
+    db: AsyncSession = Depends(get_db),
+):
+    """List assets with optional filters."""
+    stmt = select(Asset).where(Asset.owner_id == current_user.id)
+
+    if world_id is not None:
+        stmt = stmt.where(Asset.world_id == world_id)
+    if asset_type is not None:
+        stmt = stmt.where(Asset.asset_type == asset_type)
+
+    stmt = stmt.order_by(Asset.created_at.desc()).limit(limit).offset(offset)
+    result = await db.execute(stmt)
+    assets = result.scalars().all()
+    return assets
+
+
+@router.get("/{asset_id}", response_model=AssetResponse)
+async def get_asset(
+    asset_id: int,
+    current_user: CurrentUser,
+    db: AsyncSession = Depends(get_db),
+):
+    """Get a single asset by ID."""
+    asset = await db.get(Asset, asset_id)
+    if asset is None or asset.owner_id != current_user.id:
+        raise HTTPException(status_code=404, detail="Asset not found")
+    return asset
+
+
+@router.patch("/{asset_id}", response_model=AssetResponse)
+async def update_asset(
+    asset_id: int,
+    payload: AssetUpdate,
+    current_user: CurrentUser,
+    db: AsyncSession = Depends(get_db),
+):
+    """Update an asset."""
+    asset = await db.get(Asset, asset_id)
+    if asset is None or asset.owner_id != current_user.id:
+        raise HTTPException(status_code=404, detail="Asset not found")
+
+    update_data = payload.model_dump(exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(asset, field, value)
+
+    await db.commit()
+    await db.refresh(asset)
+    return asset
+
+
+@router.delete("/{asset_id}", status_code=204)
+async def delete_asset(
+    asset_id: int,
+    current_user: CurrentUser,
+    db: AsyncSession = Depends(get_db),
+):
+    """Delete an asset."""
+    asset = await db.get(Asset, asset_id)
+    if asset is None or asset.owner_id != current_user.id:
+        raise HTTPException(status_code=404, detail="Asset not found")
+
+    await db.delete(asset)
+    await db.commit()
+
+
+@router.post("/{asset_id}/upload", response_model=AssetResponse)
+async def upload_asset_file(
+    asset_id: int,
+    current_user: CurrentUser,
+    file: UploadFile = File(...),
+    db: AsyncSession = Depends(get_db),
+):
+    """Upload a file for an existing asset."""
+    asset = await db.get(Asset, asset_id)
+    if asset is None or asset.owner_id != current_user.id:
+        raise HTTPException(status_code=404, detail="Asset not found")
+
+    # Sanitize filename to prevent path traversal.
+    safe_filename = _sanitize_filename(file.filename or f"asset_{asset_id}")
+
+    # Read the file content.
+    content = await file.read()
+    file_size = len(content)
+
+    # Determine which size limit to apply.
+    if gltf_service.looks_like_gltf(content, file.filename):
+        max_bytes = settings.GLTF_MAX_FILE_SIZE_MB * 1024 * 1024
+    else:
+        max_bytes = settings.MAX_UPLOAD_SIZE_MB * 1024 * 1024
+
+    if file_size > max_bytes:
+        raise HTTPException(
+            status_code=413,
+            detail=f"File size {file_size} exceeds maximum allowed size {max_bytes} bytes",
+        )
+
+    # Write the file to the upload directory.
+    upload_dir = Path(settings.UPLOAD_DIR)
+    upload_dir.mkdir(parents=True, exist_ok=True)
+    stored_name = f"{asset_id}_{safe_filename}"
+    file_path = upload_dir / stored_name
+    file_path.write_bytes(content)
+
+    # Detect asset type from content/filename.
+    detected_type = _detect_asset_type(file.filename, content)
+
+    # Update asset record.
+    asset.file_path = str(file_path)
+    asset.mime_type = file.content_type
+    asset.file_size = file_size
+
+    # If this is a glTF file, extract and store metadata.
+    if detected_type == AssetType.MODEL_3D:
+        try:
+            metadata = gltf_service.extract_gltf_metadata(content)
+            asset.metadata_json = json.dumps(metadata)
+            # Also set the asset type to model_3d if it was auto-detected.
+            if asset.asset_type == AssetType.OTHER:
+                asset.asset_type = AssetType.MODEL_3D
+        except ValueError as exc:
+            raise HTTPException(
+                status_code=400,
+                detail=f"Invalid glTF file: {exc}",
+            )
+
+    await db.commit()
+    await db.refresh(asset)
+    return asset

backend/app/routers/auth.py

@@ -0,0 +1,323 @@
+"""Authentication router - login, register, token refresh."""
+
+import uuid
+from datetime import date, datetime, timedelta, timezone
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordRequestForm
+from jose import JWTError, jwt
+from passlib.context import CryptContext
+from pydantic import BaseModel, EmailStr
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.config import settings
+from app.database import get_db
+from app.dependencies import CurrentUser
+from app.models.session import RefreshToken
+from app.models.user import User
+from app.rate_limit import auth_rate_limit
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+router = APIRouter()
+
+## Minimum age to register. This platform is adults-only.
+MIN_AGE = 18
+
+
+# --- Pydantic schemas ---
+
+class TokenResponse(BaseModel):
+    access_token: str
+    refresh_token: str
+    token_type: str = "bearer"
+    access_token_expires_minutes: int
+
+
+class RefreshRequest(BaseModel):
+    refresh_token: str
+
+
+class RegisterRequest(BaseModel):
+    username: str
+    email: EmailStr
+    password: str
+    # Real date of birth -- the server computes age from it and rejects
+    # anyone under MIN_AGE. Still self-attested (no document check yet), but
+    # a concrete, stored, legally-meaningful data point rather than a
+    # throwaway checkbox, and the seam for a future hard ID-verification
+    # pass. See docs/architecture/content_moderation.md 5.2.
+    date_of_birth: date
+
+
+class UserResponse(BaseModel):
+    id: int
+    username: str
+    email: str
+    date_of_birth: date | None = None
+    is_active: bool
+    created_at: datetime | None = None
+
+    model_config = {"from_attributes": True}
+
+
+# --- Helpers ---
+
+def _create_access_token(data: dict) -> str:
+    """Create a signed access token using RS256.
+
+    Includes a unique ``jti`` claim so that concurrent/same-second calls
+    (e.g. back-to-back /refresh requests) still produce distinct tokens —
+    without it, two tokens minted for the same user within the same
+    second are byte-identical since ``sub``/``exp`` are the only claims.
+    """
+    to_encode = data.copy()
+    to_encode["jti"] = str(uuid.uuid4())
+    expire = datetime.now(timezone.utc) + timedelta(
+        minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES
+    )
+    to_encode.update({"exp": expire})
+    return jwt.encode(
+        to_encode,
+        settings.private_pem,
+        algorithm=settings.ALGORITHM,
+    )
+
+
+def _create_refresh_token(data: dict) -> str:
+    """Create a signed refresh token using RS256.
+
+    Includes a unique ``jti`` claim so that concurrent calls produce
+    distinct tokens even when issued within the same second.
+    """
+    to_encode = data.copy()
+    to_encode["jti"] = str(uuid.uuid4())
+    expire = datetime.now(timezone.utc) + timedelta(
+        days=settings.REFRESH_TOKEN_EXPIRE_DAYS
+    )
+    to_encode.update({"exp": expire})
+    return jwt.encode(
+        to_encode,
+        settings.private_pem,
+        algorithm=settings.ALGORITHM,
+    )
+
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    """Verify a plain password against a hash."""
+    return pwd_context.verify(plain_password, hashed_password)
+
+
+def hash_password(password: str) -> str:
+    """Hash a password."""
+    return pwd_context.hash(password)
+
+
+def calculate_age(birth_date: date, today: date | None = None) -> int:
+    """Calculate age in years from a birth date.
+
+    Used by /register (PC3 Phase 3) to compute age from the submitted
+    date_of_birth and enforce the 18+ gate. See
+    docs/architecture/content_moderation.md 5.2.
+
+    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
+
+
+def _issue_refresh_token(user_id: int, db: AsyncSession) -> str:
+    """Create and persist a refresh token for the given user."""
+    refresh_token_value = _create_refresh_token({"sub": str(user_id)})
+    refresh_token_record = RefreshToken(
+        id=str(uuid.uuid4()),
+        user_id=user_id,
+        token=refresh_token_value,
+        expires_at=datetime.now(timezone.utc)
+        + timedelta(days=settings.REFRESH_TOKEN_EXPIRE_DAYS),
+    )
+    db.add(refresh_token_record)
+    return refresh_token_value
+
+
+# --- Endpoints ---
+
+@router.post("/register", response_model=TokenResponse, status_code=status.HTTP_201_CREATED,
+             dependencies=[Depends(auth_rate_limit)])
+async def register(req: RegisterRequest, db: AsyncSession = Depends(get_db)):
+    """Register a new user and return access + refresh tokens.
+
+    Requires a date of birth; the server computes age and rejects anyone
+    under MIN_AGE (18). See docs/architecture/content_moderation.md for the
+    verification design and its self-attestation limitation.
+    """
+    age = calculate_age(req.date_of_birth)
+    if age < 0 or req.date_of_birth > date.today():
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Invalid date of birth",
+        )
+    if age < MIN_AGE:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail=f"You must be at least {MIN_AGE} to use this platform",
+        )
+
+    # Check if username already exists
+    result = await db.execute(select(User).where(User.username == req.username))
+    if result.scalar_one_or_none():
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="Username already registered",
+        )
+
+    # Check if email already exists
+    result = await db.execute(select(User).where(User.email == req.email))
+    if result.scalar_one_or_none():
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="Email already registered",
+        )
+
+    user = User(
+        username=req.username,
+        email=req.email,
+        hashed_password=hash_password(req.password),
+        date_of_birth=req.date_of_birth,
+    )
+    db.add(user)
+    await db.flush()  # flush to get user.id before creating refresh token
+    await db.refresh(user)
+
+    # Create access token
+    access_token = _create_access_token({"sub": str(user.id)})
+
+    # Create and persist refresh token
+    refresh_token_value = _issue_refresh_token(user.id, db)
+    await db.commit()
+
+    return TokenResponse(
+        access_token=access_token,
+        refresh_token=refresh_token_value,
+        access_token_expires_minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES,
+    )
+
+
+@router.post("/login", response_model=TokenResponse, dependencies=[Depends(auth_rate_limit)])
+async def login(form: OAuth2PasswordRequestForm = Depends(), db: AsyncSession = Depends(get_db)):
+    """Authenticate user and return access + refresh tokens.
+
+    Accepts form-encoded credentials (username/password) as expected by
+    OAuth2PasswordBearer, so the Swagger UI "Authorize" flow works correctly.
+    """
+    result = await db.execute(select(User).where(User.username == form.username))
+    user = result.scalar_one_or_none()
+
+    if not user or not verify_password(form.password, user.hashed_password):
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Incorrect username or password",
+        )
+
+    if not user.is_active:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="User account is inactive",
+        )
+
+    # Create access token
+    access_token = _create_access_token({"sub": str(user.id)})
+
+    # Create and persist refresh token
+    refresh_token_value = _issue_refresh_token(user.id, db)
+    await db.commit()
+
+    return TokenResponse(
+        access_token=access_token,
+        refresh_token=refresh_token_value,
+        access_token_expires_minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES,
+    )
+
+
+@router.post("/refresh", response_model=TokenResponse)
+async def refresh(req: RefreshRequest, db: AsyncSession = Depends(get_db)):
+    """Exchange a valid refresh token for a new access token.
+
+    Validates the refresh token against the database:
+    - Must exist in the refresh_tokens table
+    - Must not be expired (expires_at > now)
+    - Must be active (is_active == true)
+
+    On success, returns a new access token. The refresh token itself is
+    NOT rotated (the client keeps using the same refresh token).
+    """
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Invalid or expired refresh token",
+    )
+
+    # Step 1: Decode and validate the JWT signature/claims
+    try:
+        payload = jwt.decode(
+            req.refresh_token,
+            settings.public_pem,
+            algorithms=[settings.ALGORITHM],
+        )
+    except JWTError:
+        raise credentials_exception
+
+    user_id_str: str | None = payload.get("sub")
+    if user_id_str is None:
+        raise credentials_exception
+
+    try:
+        user_id = int(user_id_str)
+    except (ValueError, TypeError):
+        raise credentials_exception
+
+    # Step 2: Look up the refresh token in the database
+    result = await db.execute(
+        select(RefreshToken).where(
+            RefreshToken.token == req.refresh_token,
+            RefreshToken.user_id == user_id,
+        )
+    )
+    stored_token = result.scalar_one_or_none()
+
+    if stored_token is None:
+        raise credentials_exception
+
+    # Step 3: Check if the token is expired
+    if datetime.now(timezone.utc) >= stored_token.expires_at:
+        raise credentials_exception
+
+    # Step 4: Check if the token is active
+    if not stored_token.is_active:
+        raise credentials_exception
+
+    # Step 5: Issue a new access token
+    access_token = _create_access_token({"sub": str(user_id)})
+
+    return TokenResponse(
+        access_token=access_token,
+        refresh_token=req.refresh_token,  # Return the same refresh token
+        access_token_expires_minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES,
+    )
+
+
+@router.get("/me", response_model=UserResponse)
+async def get_current_user(current_user: CurrentUser):
+    """Get current user profile from the JWT token."""
+    return current_user

backend/app/routers/avatar.py

@@ -0,0 +1,78 @@
+"""Avatar router - the current user's persisted avatar loadout.
+
+The loadout is a single JSON document matching the client's
+``AvatarLoadout.to_json()`` shape. The server has no copy of the asset
+catalog, so it only validates the envelope (JSON object, non-empty
+``base_body``); which assets are valid for which slot is the client's job.
+"""
+
+from typing import Annotated, Any
+
+from fastapi import APIRouter, Depends, HTTPException
+from pydantic import BaseModel, Field
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.database import get_db
+from app.dependencies import CurrentUser
+from app.models.avatar_loadout import AvatarLoadout, DEFAULT_LOADOUT
+
+router = APIRouter()
+
+DbDep = Annotated[AsyncSession, Depends(get_db)]
+
+# A loadout document is small; reject anything absurd outright.
+MAX_LOADOUT_BYTES = 16 * 1024
+
+
+class LoadoutResponse(BaseModel):
+    data: dict[str, Any]
+    is_default: bool = Field(
+        description="True when the user has never saved a loadout and this is "
+        "the server default."
+    )
+
+
+class LoadoutUpdate(BaseModel):
+    data: dict[str, Any]
+
+
+def _validate_envelope(data: dict[str, Any]) -> None:
+    base_body = data.get("base_body")
+    if not isinstance(base_body, str) or not base_body.strip():
+        raise HTTPException(
+            status_code=422,
+            detail="loadout.data must have a non-empty string 'base_body'",
+        )
+    slots = data.get("slots", {})
+    if not isinstance(slots, dict):
+        raise HTTPException(status_code=422, detail="loadout.data.slots must be an object")
+    if len(str(data)) > MAX_LOADOUT_BYTES:
+        raise HTTPException(status_code=413, detail="loadout document too large")
+
+
+@router.get("/loadout", response_model=LoadoutResponse)
+async def get_loadout(current_user: CurrentUser, db: DbDep):
+    """Return the current user's saved loadout, or the server default if they
+    have never saved one."""
+    row = await db.get(AvatarLoadout, current_user.id)
+    if row is None:
+        return LoadoutResponse(data=dict(DEFAULT_LOADOUT), is_default=True)
+    return LoadoutResponse(data=row.data, is_default=False)
+
+
+@router.put("/loadout", response_model=LoadoutResponse)
+async def put_loadout(payload: LoadoutUpdate, current_user: CurrentUser, db: DbDep):
+    """Replace the current user's loadout."""
+    _validate_envelope(payload.data)
+
+    row = await db.get(AvatarLoadout, current_user.id)
+    if row is None:
+        row = AvatarLoadout(user_id=current_user.id, data=payload.data)
+        db.add(row)
+    else:
+        row.data = payload.data
+
+    await db.commit()
+    await db.refresh(row)
+    return LoadoutResponse(data=row.data, is_default=False)

backend/app/routers/users.py

@@ -0,0 +1,106 @@
+"""User management router."""
+
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from pydantic import BaseModel, EmailStr
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.database import get_db
+from app.dependencies import CurrentUser
+from app.models.user import User
+
+router = APIRouter()
+
+
+# ─── Pydantic schemas ────────────────────────────────────────────────────────
+
+class UserResponse(BaseModel):
+    id: int
+    username: str
+    email: str
+    is_active: bool
+
+    model_config = {"from_attributes": True}
+
+
+class UserUpdate(BaseModel):
+    email: EmailStr | None = None
+    is_active: bool | None = None
+
+
+# ─── Endpoints ───────────────────────────────────────────────────────────────
+
+@router.get("/me", response_model=UserResponse)
+async def get_current_user_profile(
+    current_user: CurrentUser,
+):
+    """Get the currently authenticated user's profile."""
+    return current_user
+
+
+@router.get("/{user_id}", response_model=UserResponse)
+async def get_user(
+    user_id: int,
+    current_user: CurrentUser,
+    db: Annotated[AsyncSession, Depends(get_db)],
+):
+    """Get a user by ID.  Only the owner can view their own profile."""
+    result = await db.execute(select(User).where(User.id == user_id))
+    user = result.scalar_one_or_none()
+    if not user:
+        raise HTTPException(status_code=404, detail="User not found")
+
+    # Only the owner may view their own profile.
+    if user.id != current_user.id:
+        raise HTTPException(status_code=403, detail="Not authorized to view this user")
+
+    return user
+
+
+@router.patch("/{user_id}", response_model=UserResponse)
+async def update_user(
+    user_id: int,
+    user_update: UserUpdate,
+    current_user: CurrentUser,
+    db: Annotated[AsyncSession, Depends(get_db)],
+):
+    """Update a user.  Only the owner can update their own account."""
+    result = await db.execute(select(User).where(User.id == user_id))
+    user = result.scalar_one_or_none()
+    if not user:
+        raise HTTPException(status_code=404, detail="User not found")
+
+    # Only the owner may update their own account.
+    if user.id != current_user.id:
+        raise HTTPException(status_code=403, detail="Not authorized to update this user")
+
+    if user_update.email is not None:
+        user.email = user_update.email
+    if user_update.is_active is not None:
+        user.is_active = user_update.is_active
+
+    await db.commit()
+    await db.refresh(user)
+    return user
+
+
+@router.delete("/{user_id}", status_code=status.HTTP_204_NO_CONTENT)
+async def delete_user(
+    user_id: int,
+    current_user: CurrentUser,
+    db: Annotated[AsyncSession, Depends(get_db)],
+):
+    """Delete a user.  Only the owner can delete their own account."""
+    result = await db.execute(select(User).where(User.id == user_id))
+    user = result.scalar_one_or_none()
+    if not user:
+        raise HTTPException(status_code=404, detail="User not found")
+
+    # Only the owner may delete their own account.
+    if user.id != current_user.id:
+        raise HTTPException(status_code=403, detail="Not authorized to delete this user")
+
+    await db.delete(user)
+    await db.commit()

backend/app/routers/worlds.py

@@ -0,0 +1,204 @@
+"""Worlds router - CRUD for game worlds."""
+
+from datetime import datetime
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, HTTPException, Query
+from pydantic import BaseModel, Field
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from app.database import get_db
+from app.dependencies import CurrentUser
+from app.models.world import World, WorldVisibility
+from app.services.game_servers import supervisor
+
+router = APIRouter()
+
+DbDep = Annotated[AsyncSession, Depends(get_db)]
+
+
+# --- Pydantic schemas ---
+
+class WorldCreate(BaseModel):
+    """Schema for creating a world."""
+    name: str = Field(..., min_length=1, max_length=255)
+    description: str | None = None
+    visibility: WorldVisibility = WorldVisibility.PUBLIC
+
+
+class WorldUpdate(BaseModel):
+    """Schema for updating a world."""
+    name: str | None = Field(None, min_length=1, max_length=255)
+    description: str | None = None
+    visibility: WorldVisibility | None = None
+
+
+class WorldResponse(BaseModel):
+    """Schema for world responses."""
+    id: int
+    name: str
+    description: str | None
+    visibility: WorldVisibility
+    owner_id: int
+    created_at: datetime | None = None
+
+    model_config = {"from_attributes": True}
+
+
+# --- Endpoints ---
+
+@router.get("/", response_model=list[WorldResponse])
+async def list_worlds(
+    current_user: CurrentUser,
+    db: DbDep,
+    skip: int = Query(0, ge=0),
+    limit: int = Query(50, ge=1, le=100),
+    visibility: WorldVisibility | None = None,
+):
+    """List worlds visible to the current user.
+
+    PUBLIC worlds are visible to everyone.
+    PRIVATE/FRIENDS_ONLY worlds are visible to their owner.
+    """
+    query = select(World).options(selectinload(World.owner))
+
+    # Filter by visibility if specified
+    if visibility:
+        query = query.where(World.visibility == visibility)
+        if visibility != WorldVisibility.PUBLIC:
+            # Requesting a non-public visibility explicitly must not bypass
+            # ownership — otherwise any authenticated user could list every
+            # PRIVATE/FRIENDS_ONLY world in the system just by passing the
+            # filter, defeating the point of the check below.
+            query = query.where(World.owner_id == current_user.id)
+    else:
+        # Show PUBLIC worlds + owner's own worlds
+        query = query.where(
+            (World.visibility == WorldVisibility.PUBLIC)
+            | (World.owner_id == current_user.id)
+        )
+
+    query = query.offset(skip).limit(limit).order_by(World.created_at.desc())
+    result = await db.execute(query)
+    worlds = result.scalars().all()
+    return worlds
+
+
+@router.get("/{world_id}", response_model=WorldResponse)
+async def get_world(
+    world_id: int,
+    current_user: CurrentUser,
+    db: DbDep,
+):
+    """Get a single world by ID, respecting visibility."""
+    result = await db.execute(
+        select(World).where(World.id == world_id).options(selectinload(World.owner))
+    )
+    world = result.scalar_one_or_none()
+    if not world:
+        raise HTTPException(status_code=404, detail="World not found")
+
+    # Allow access if world is PUBLIC or owned by current user
+    if world.visibility != WorldVisibility.PUBLIC and world.owner_id != current_user.id:
+        raise HTTPException(status_code=404, detail="World not found")
+
+    return world
+
+
+class JoinResponse(BaseModel):
+    """Address of the dedicated server hosting this world."""
+    world_id: int
+    host: str
+    port: int
+
+
+@router.post("/{world_id}/join", response_model=JoinResponse)
+async def join_world(
+    world_id: int,
+    current_user: CurrentUser,
+    db: DbDep,
+):
+    """Ensure a dedicated game server is running for this world and return its
+    ENet address for the client to connect to.
+
+    503 if game-server orchestration isn't enabled on this backend (e.g. a
+    plain dev/test instance with no Godot binary).
+    """
+    result = await db.execute(select(World).where(World.id == world_id))
+    world = result.scalar_one_or_none()
+    if not world:
+        raise HTTPException(status_code=404, detail="World not found")
+    if world.visibility != WorldVisibility.PUBLIC and world.owner_id != current_user.id:
+        raise HTTPException(status_code=404, detail="World not found")
+
+    try:
+        info = await supervisor.ensure_server(str(world_id))
+    except RuntimeError as exc:
+        raise HTTPException(status_code=503, detail=str(exc))
+
+    return JoinResponse(world_id=world_id, host=info["host"], port=info["port"])
+
+
+@router.post("/", response_model=WorldResponse, status_code=201)
+async def create_world(
+    world_data: WorldCreate,
+    current_user: CurrentUser,
+    db: DbDep,
+):
+    """Create a new world."""
+    world = World(
+        name=world_data.name,
+        description=world_data.description,
+        owner_id=current_user.id,
+        visibility=world_data.visibility,
+    )
+    db.add(world)
+    await db.commit()
+    await db.refresh(world)
+    return world
+
+
+@router.put("/{world_id}", response_model=WorldResponse)
+async def update_world(
+    world_id: int,
+    world_data: WorldUpdate,
+    current_user: CurrentUser,
+    db: DbDep,
+):
+    """Update an existing world."""
+    result = await db.execute(select(World).where(World.id == world_id))
+    world = result.scalar_one_or_none()
+    if not world:
+        raise HTTPException(status_code=404, detail="World not found")
+
+    if world.owner_id != current_user.id:
+        raise HTTPException(status_code=403, detail="Not owner of this world")
+
+    update_data = world_data.model_dump(exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(world, field, value)
+
+    await db.commit()
+    await db.refresh(world)
+    return world
+
+
+@router.delete("/{world_id}", status_code=204)
+async def delete_world(
+    world_id: int,
+    current_user: CurrentUser,
+    db: DbDep,
+):
+    """Delete a world."""
+    result = await db.execute(select(World).where(World.id == world_id))
+    world = result.scalar_one_or_none()
+    if not world:
+        raise HTTPException(status_code=404, detail="World not found")
+
+    if world.owner_id != current_user.id:
+        raise HTTPException(status_code=403, detail="Not owner of this world")
+
+    await db.delete(world)
+    await db.commit()

backend/app/services/game_servers.py

@@ -0,0 +1,182 @@
+"""Game-server orchestration.
+
+On ``POST /api/worlds/{id}/join`` the backend ensures a headless Godot
+dedicated-server process is running for that world and returns its address.
+One process per world, keyed by ``world_id``. A background reaper kills a
+world's server once its status file reports zero players for
+``GAME_SERVER_IDLE_TIMEOUT_SECONDS``.
+
+This lives in-process (a module-level singleton) rather than as a separate
+service, so the backend MUST run single-worker -- which it does
+(``uvicorn app.main:app`` with no ``--workers``). The Godot binary and
+project are on the host (see ``settings.GODOT_BIN`` / ``GAME_PROJECT_DIR``);
+the backend spawns them as subprocesses.
+
+Design notes / limits (PC3):
+ - All worlds currently load the same test level (per-world content is M2/M7).
+   ``world_id`` still scopes a distinct server process + session.
+ - Port allocation is a linear scan of the configured range.
+ - No crash-restart: if a server process dies, the next join respawns it.
+"""
+from __future__ import annotations
+
+import asyncio
+import json
+import socket
+import subprocess
+import tempfile
+import time
+from dataclasses import dataclass, field
+from pathlib import Path
+
+from app.config import settings
+
+
+@dataclass
+class _WorldServer:
+    world_id: str
+    port: int
+    proc: subprocess.Popen
+    status_path: Path
+    started_at: float = field(default_factory=time.time)
+    last_join: float = field(default_factory=time.time)
+
+    def status(self) -> dict:
+        try:
+            return json.loads(self.status_path.read_text())
+        except (OSError, ValueError):
+            return {}
+
+    def player_count(self) -> int:
+        return int(self.status().get("players", 0))
+
+    def alive(self) -> bool:
+        return self.proc.poll() is None
+
+    def stop(self) -> None:
+        if self.alive():
+            self.proc.terminate()
+            try:
+                self.proc.wait(timeout=10)
+            except subprocess.TimeoutExpired:
+                self.proc.kill()
+        self.status_path.unlink(missing_ok=True)
+
+
+class GameServerSupervisor:
+    def __init__(self) -> None:
+        self._servers: dict[str, _WorldServer] = {}
+        self._lock = asyncio.Lock()
+        self._reaper: asyncio.Task | None = None
+        self._runtime_dir = Path(tempfile.gettempdir()) / "agp-game-servers"
+        self._runtime_dir.mkdir(parents=True, exist_ok=True)
+
+    # ── lifecycle ────────────────────────────────────────────────────────
+    def start(self) -> None:
+        if not settings.GAME_SERVERS_ENABLED:
+            return
+        if self._reaper is None or self._reaper.done():
+            self._reaper = asyncio.create_task(self._reap_loop())
+
+    async def shutdown(self) -> None:
+        if self._reaper:
+            self._reaper.cancel()
+        async with self._lock:
+            for srv in list(self._servers.values()):
+                srv.stop()
+            self._servers.clear()
+
+    # ── join ─────────────────────────────────────────────────────────────
+    async def ensure_server(self, world_id: str) -> dict:
+        """Return ``{"host", "port", "world_id"}`` for the world's dedicated
+        server, spawning it if needed. Raises RuntimeError if orchestration
+        is disabled or no port/engine is available."""
+        if not settings.GAME_SERVERS_ENABLED:
+            raise RuntimeError("game servers are not enabled on this backend")
+
+        async with self._lock:
+            srv = self._servers.get(world_id)
+            if srv is not None and not srv.alive():
+                srv.stop()
+                srv = None
+                del self._servers[world_id]
+
+            if srv is None:
+                srv = self._spawn(world_id)
+                self._servers[world_id] = srv
+                # Give the engine a moment to bind the ENet port before we
+                # hand the address to a client.
+                await self._await_port(srv.port)
+
+            srv.last_join = time.time()
+            return {"host": settings.GAME_SERVER_HOST, "port": srv.port, "world_id": world_id}
+
+    # ── internals ────────────────────────────────────────────────────────
+    def _spawn(self, world_id: str) -> _WorldServer:
+        port = self._free_port()
+        status_path = self._runtime_dir / f"world_{world_id}_{port}.json"
+        status_path.unlink(missing_ok=True)
+        cmd = [
+            settings.GODOT_BIN, "--headless",
+            "--path", settings.GAME_PROJECT_DIR,
+            "res://scenes/server.tscn", "--",
+            "--port", str(port),
+            "--world", str(world_id),
+            "--status-file", str(status_path),
+        ]
+        proc = subprocess.Popen(cmd, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+        return _WorldServer(world_id=world_id, port=port, proc=proc, status_path=status_path)
+
+    def _free_port(self) -> int:
+        used = {s.port for s in self._servers.values()}
+        for p in range(settings.GAME_SERVER_PORT_MIN, settings.GAME_SERVER_PORT_MAX + 1):
+            if p in used:
+                continue
+            with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as s:
+                try:
+                    s.bind(("0.0.0.0", p))
+                    return p
+                except OSError:
+                    continue
+        raise RuntimeError("no free game-server port in the configured range")
+
+    async def _await_port(self, port: int, timeout: float = 8.0) -> None:
+        deadline = time.time() + timeout
+        while time.time() < deadline:
+            # ENet is UDP; a bind failure means something (our server) has it.
+            with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as s:
+                try:
+                    s.bind(("0.0.0.0", port))
+                except OSError:
+                    return
+            await asyncio.sleep(0.25)
+
+    async def _reap_loop(self) -> None:
+        try:
+            while True:
+                await asyncio.sleep(30)
+                async with self._lock:
+                    now = time.time()
+                    for wid, srv in list(self._servers.items()):
+                        if not srv.alive():
+                            srv.stop()
+                            del self._servers[wid]
+                            continue
+                        idle_for = now - srv.last_join
+                        if idle_for > settings.GAME_SERVER_IDLE_TIMEOUT_SECONDS and srv.player_count() == 0:
+                            srv.stop()
+                            del self._servers[wid]
+        except asyncio.CancelledError:
+            pass
+
+    def debug_state(self) -> list[dict]:
+        return [
+            {
+                "world_id": s.world_id, "port": s.port, "alive": s.alive(),
+                "players": s.player_count(), "uptime_s": round(time.time() - s.started_at),
+            }
+            for s in self._servers.values()
+        ]
+
+
+supervisor = GameServerSupervisor()

backend/app/services/gltf.py

@@ -0,0 +1,197 @@
+"""Lightweight glTF / GLB metadata extraction.
+
+This module intentionally avoids heavyweight dependencies such as trimesh or
+pygltflib. For the metadata fields the asset upload pipeline needs (mesh and
+vertex counts, animation presence, texture references, and the bounding box)
+a small amount of glTF-specific parsing is sufficient and keeps the backend
+dependency-free.
+"""
+
+from __future__ import annotations
+
+import json
+import struct
+from typing import Any, Optional
+
+# GLB binary header magic bytes ("glTF").
+_GLB_MAGIC = b"glTF"
+_GLB_MAGIC_INT = 0x46546C67  # b"glTF" interpreted as little-endian uint32
+_GLB_JSON_CHUNK_TYPE = 0x4E4F534A  # "JSON"
+_GLB_BIN_CHUNK_TYPE = 0x004E4942  # "BIN\0"
+
+# Whitespace allowed around a GLB JSON chunk. The spec pads with spaces (0x20),
+# but be lenient with null bytes and other whitespace that real exporters emit.
+_JSON_CHUNK_TRIM = b" \t\r\n\x00"
+
+
+def looks_like_gltf(content: bytes, filename: Optional[str] = None) -> bool:
+    """Return True when the bytes or filename indicate a glTF/GLB asset."""
+    if content.startswith(_GLB_MAGIC):
+        return True
+
+    if filename:
+        lowered = filename.lower()
+        if lowered.endswith(".gltf") or lowered.endswith(".glb"):
+            return True
+
+    # A bare JSON buffer (e.g. uploaded without an extension) that has the
+    # glTF asset marker is also a glTF file.
+    stripped = content.lstrip()
+    if stripped.startswith(b"{"):
+        try:
+            payload = json.loads(stripped.decode("utf-8"))
+        except (ValueError, UnicodeDecodeError):
+            return False
+        return isinstance(payload, dict) and "asset" in payload and "version" in payload.get("asset", {})
+
+    return False
+
+
+def _parse_glb(content: bytes) -> dict[str, Any]:
+    """Parse the JSON chunk of a GLB binary container."""
+    if len(content) < 12:
+        raise ValueError("GLB file is too short")
+
+    magic, _version, _length = struct.unpack_from("<III", content, 0)
+    if magic != _GLB_MAGIC_INT:
+        raise ValueError("invalid GLB magic")
+
+    offset = 12
+    json_chunk: Optional[dict[str, Any]] = None
+
+    while offset + 8 <= len(content):
+        chunk_length, chunk_type = struct.unpack_from("<II", content, offset)
+        offset += 8
+        chunk_end = offset + chunk_length
+        if chunk_end > len(content):
+            raise ValueError("GLB chunk overruns file boundary")
+
+        chunk_data = content[offset:chunk_end]
+        if chunk_type == _GLB_JSON_CHUNK_TYPE:
+            try:
+                json_chunk = json.loads(chunk_data.strip(_JSON_CHUNK_TRIM).decode("utf-8"))
+            except (ValueError, UnicodeDecodeError) as exc:
+                raise ValueError(f"invalid GLB JSON chunk: {exc}") from exc
+
+        offset = chunk_end
+
+    if json_chunk is None:
+        raise ValueError("GLB file does not contain a JSON chunk")
+
+    return json_chunk
+
+
+def _parse_gltf_json(content: bytes) -> dict[str, Any]:
+    """Parse a plain .gltf JSON file."""
+    stripped = content.lstrip()
+    try:
+        payload = json.loads(stripped.decode("utf-8"))
+    except (ValueError, UnicodeDecodeError) as exc:
+        raise ValueError(f"invalid glTF JSON: {exc}") from exc
+
+    if not isinstance(payload, dict):
+        raise ValueError("glTF JSON root must be an object")
+    return payload
+
+
+def _position_accessor_counts(gltf: dict[str, Any]) -> list[int]:
+    """Return POSITION accessor counts for every mesh primitive."""
+    counts: list[int] = []
+    accessors = gltf.get("accessors", [])
+    for mesh in gltf.get("meshes", []):
+        for primitive in mesh.get("primitives", []):
+            attributes = primitive.get("attributes", {})
+            position_index = attributes.get("POSITION")
+            if position_index is None:
+                continue
+            try:
+                accessor = accessors[int(position_index)]
+            except (IndexError, TypeError, ValueError):
+                continue
+            count = accessor.get("count")
+            if isinstance(count, int):
+                counts.append(count)
+    return counts
+
+
+def _position_bounds(gltf: dict[str, Any]) -> list[list[float]]:
+    """Return min/max bounds for every POSITION accessor that declares them."""
+    bounds: list[list[float]] = []
+    accessors = gltf.get("accessors", [])
+    for mesh in gltf.get("meshes", []):
+        for primitive in mesh.get("primitives", []):
+            attributes = primitive.get("attributes", {})
+            position_index = attributes.get("POSITION")
+            if position_index is None:
+                continue
+            try:
+                accessor = accessors[int(position_index)]
+            except (IndexError, TypeError, ValueError):
+                continue
+            minimum = accessor.get("min")
+            maximum = accessor.get("max")
+            if isinstance(minimum, list) and isinstance(maximum, list):
+                bounds.append([float(x) for x in minimum])
+                bounds.append([float(x) for x in maximum])
+    return bounds
+
+
+def _texture_refs(gltf: dict[str, Any]) -> list[str]:
+    """Collect external texture source references from the image array."""
+    refs: list[str] = []
+    for index, image in enumerate(gltf.get("images", [])):
+        uri = image.get("uri")
+        if isinstance(uri, str) and not uri.startswith("data:"):
+            refs.append(uri)
+            continue
+
+        name = image.get("name")
+        if isinstance(name, str) and name:
+            refs.append(name)
+            continue
+
+        if isinstance(uri, str):
+            # Embedded data URI; keep a stable, non-huge reference.
+            refs.append(f"data:{index}")
+            continue
+
+        buffer_view = image.get("bufferView")
+        if buffer_view is not None:
+            refs.append(f"bufferView:{buffer_view}")
+            continue
+
+        refs.append(f"image:{index}")
+
+    return refs
+
+
+def extract_gltf_metadata(content: bytes) -> dict[str, Any]:
+    """Extract upload-relevant metadata from glTF/GLB bytes.
+
+    Raises ValueError for malformed glTF content. The returned dict contains:
+        mesh_count, vertex_count, has_animation, texture_refs,
+        bounding_box_min, bounding_box_max.
+    """
+    if content.startswith(_GLB_MAGIC):
+        gltf = _parse_glb(content)
+    else:
+        gltf = _parse_gltf_json(content)
+
+    position_counts = _position_accessor_counts(gltf)
+    bounds = _position_bounds(gltf)
+
+    if bounds:
+        bounding_box_min = [min(axis) for axis in zip(*bounds[::2])]
+        bounding_box_max = [max(axis) for axis in zip(*bounds[1::2])]
+    else:
+        bounding_box_min = [0.0, 0.0, 0.0]
+        bounding_box_max = [0.0, 0.0, 0.0]
+
+    return {
+        "mesh_count": len(gltf.get("meshes", [])),
+        "vertex_count": sum(position_counts),
+        "has_animation": bool(gltf.get("animations")),
+        "texture_refs": _texture_refs(gltf),
+        "bounding_box_min": bounding_box_min,
+        "bounding_box_max": bounding_box_max,
+    }

backend/docker-compose.yml

@@ -0,0 +1,34 @@
+version: "3.9"
+
+services:
+  postgres:
+    image: postgres:16-alpine
+    environment:
+      POSTGRES_USER: agp_user
+      POSTGRES_PASSWORD: agp_password
+      POSTGRES_DB: agp_db
+    ports:
+      - "${POSTGRES_HOST_PORT:-5432}:5432"
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U agp_user -d agp_db"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+
+  redis:
+    image: redis:7-alpine
+    ports:
+      - "${REDIS_HOST_PORT:-6379}:6379"
+    volumes:
+      - redis_data:/data
+    healthcheck:
+      test: ["CMD", "redis-cli", "ping"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+
+volumes:
+  postgres_data:
+  redis_data:

backend/pytest.ini

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

backend/requirements.txt

@@ -0,0 +1,25 @@
+fastapi==0.115.6
+uvicorn[standard]==0.34.0
+sqlalchemy==2.0.36
+alembic==1.14.0
+psycopg2-binary==2.9.10
+asyncpg==0.31.0
+redis==5.2.1
+pydantic==2.10.3
+pydantic-settings==2.7.0
+python-jose[cryptography]==3.3.0
+passlib[bcrypt]==1.7.4
+# passlib 1.7.4 (last release, unmaintained since ~2020) detects its bcrypt
+# backend via bcrypt.__about__.__version__, which bcrypt>=4.1 removed --
+# hashing/verifying a password then raises "password cannot be longer than
+# 72 bytes" (a misleading downstream symptom of the real AttributeError:
+# module 'bcrypt' has no attribute '__about__') on every call. Without this
+# pin, `pip install -r requirements.txt` silently grabs whatever the latest
+# bcrypt is and breaks register/login outright. Pin below 4.1 explicitly.
+bcrypt==4.0.1
+python-multipart==0.0.20
+email-validator==2.2.0
+httpx==0.28.1
+pytest==8.3.4
+pytest-asyncio==0.25.0
+pytest-cov==6.0.0

backend/tests/conftest.py

@@ -0,0 +1,174 @@
+"""Shared pytest fixtures + hermetic-DB bootstrap.
+
+The integration tests hit a real Postgres (Postgres-specific types: JSONB,
+native ENUMs). To make ``cd backend && pytest`` work from a clean checkout
+with no manual setup, ``pytest_configure`` below brings up an ephemeral
+Postgres via docker compose and runs the migrations IF ``DATABASE_URL`` is
+not already pointing at a reachable database. When it is (dev loop, or the
+checkpoint runner which stands the DB up itself), that path is skipped and
+the existing database is reused.
+
+If Docker isn't available and no DB is reachable, the whole DB-backed suite
+is skipped with a clear message rather than erroring out 60+ times.
+"""
+
+import asyncio
+import os
+import socket
+import subprocess
+import sys
+import time
+from pathlib import Path
+from urllib.parse import urlsplit
+
+import pytest
+from sqlalchemy import text
+from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
+from sqlalchemy.pool import NullPool
+
+from app.config import settings
+from app.database import get_db
+from app.main import app
+
+TEST_TABLES = ("avatar_loadouts", "assets", "worlds", "sessions", "refresh_tokens", "users")
+
+BACKEND_DIR = Path(__file__).resolve().parents[1]
+_COMPOSE_PROJECT = "agp-pytest"
+_EPHEMERAL_PG_PORT = 25432
+
+# Set by _ensure_database() when it starts a container it owns; torn down in
+# pytest_unconfigure.
+_started_container = False
+_db_unavailable_reason: str | None = None
+
+
+def _port_open(host: str, port: int, timeout: float = 1.0) -> bool:
+    try:
+        with socket.create_connection((host, port), timeout=timeout):
+            return True
+    except OSError:
+        return False
+
+
+def _db_reachable(url: str) -> bool:
+    parts = urlsplit(url)
+    return _port_open(parts.hostname or "localhost", parts.port or 5432)
+
+
+def _run(cmd: list[str], **kw) -> subprocess.CompletedProcess:
+    return subprocess.run(cmd, cwd=BACKEND_DIR, capture_output=True, text=True, **kw)
+
+
+def pytest_configure(config):
+    global _started_container, _db_unavailable_reason
+
+    if _db_reachable(settings.DATABASE_URL):
+        return  # dev loop / checkpoint runner already provided one
+
+    if not _run(["docker", "--version"]).returncode == 0:
+        _db_unavailable_reason = (
+            "no reachable DATABASE_URL and docker is unavailable -- run the "
+            "checkpoint suite (scripts/run_checkpoint_tests.py) or start Postgres "
+            "manually"
+        )
+        return
+
+    env = os.environ.copy()
+    env["COMPOSE_PROJECT_NAME"] = _COMPOSE_PROJECT
+    env["POSTGRES_HOST_PORT"] = str(_EPHEMERAL_PG_PORT)
+    env["POSTGRES_PORT"] = str(_EPHEMERAL_PG_PORT)
+    up = _run(["docker", "compose", "up", "-d", "postgres"], env=env)
+    if up.returncode != 0:
+        _db_unavailable_reason = f"docker compose up postgres failed:\n{up.stderr[-800:]}"
+        return
+    _started_container = True
+
+    for _ in range(30):
+        r = _run(
+            ["docker", "compose", "exec", "-T", "postgres",
+             "pg_isready", "-U", "agp_user", "-d", "agp_db"],
+            env=env,
+        )
+        if r.returncode == 0:
+            break
+        time.sleep(1)
+    else:
+        _db_unavailable_reason = "ephemeral Postgres never became ready"
+        return
+
+    url = f"postgresql+asyncpg://agp_user:agp_password@localhost:{_EPHEMERAL_PG_PORT}/agp_db"
+    os.environ["DATABASE_URL"] = url
+    settings.DATABASE_URL = url
+
+    mig = _run([sys.executable, "-m", "alembic", "upgrade", "head"],
+               env={**os.environ, "DATABASE_URL": url})
+    if mig.returncode != 0:
+        _db_unavailable_reason = f"alembic upgrade head failed:\n{mig.stderr[-800:]}"
+
+
+def pytest_unconfigure(config):
+    if not _started_container:
+        return
+    env = os.environ.copy()
+    env["COMPOSE_PROJECT_NAME"] = _COMPOSE_PROJECT
+    env["POSTGRES_HOST_PORT"] = str(_EPHEMERAL_PG_PORT)
+    env["POSTGRES_PORT"] = str(_EPHEMERAL_PG_PORT)
+    _run(["docker", "compose", "down", "-v"], env=env)
+
+
+@pytest.fixture(scope="session", autouse=True)
+def _reset_database():
+    """Truncate all application tables once per test session."""
+    if _db_unavailable_reason:
+        pytest.skip(_db_unavailable_reason, allow_module_level=True)
+
+    async def _truncate() -> None:
+        engine = create_async_engine(settings.DATABASE_URL)
+        async with engine.begin() as conn:
+            await conn.execute(text(f"TRUNCATE TABLE {', '.join(TEST_TABLES)} CASCADE"))
+        await engine.dispose()
+
+    asyncio.run(_truncate())
+    yield
+
+
+@pytest.fixture(autouse=True)
+def _reset_rate_limiter():
+    """Every TestClient request looks like the same client IP, so the
+    per-IP auth limiter would trip mid-suite. Clear it between tests; the
+    dedicated rate-limit test disables this to exercise the real behaviour.
+    """
+    from app import rate_limit
+    rate_limit.reset_all()
+    yield
+
+
+@pytest.fixture(autouse=True)
+def _override_db():
+    """Override get_db so the app uses a fresh session per test.
+
+    Deliberately does NOT reuse app.database's shared engine: FastAPI's
+    (sync) TestClient runs each request through anyio's blocking-portal
+    machinery, which can hand different requests different event loops.
+    asyncpg connections are bound to the loop they were created on, so
+    reusing one from the shared pool across requests raises "attached to a
+    different loop" the moment a test makes more than one request. NullPool
+    sidesteps it: every checkout is a brand-new connection.
+    """
+    test_engine = create_async_engine(settings.DATABASE_URL, poolclass=NullPool)
+    test_session_factory = async_sessionmaker(test_engine, expire_on_commit=False)
+
+    async def _get_db():
+        async_session = test_session_factory()
+        try:
+            yield async_session
+            await async_session.commit()
+        except Exception:
+            await async_session.rollback()
+            raise
+        finally:
+            await async_session.close()
+
+    app.dependency_overrides[get_db] = _get_db
+    yield
+    app.dependency_overrides.clear()

backend/tests/test_auth_age_gate.py

@@ -0,0 +1,104 @@
+"""Tests for the 18+ age gate on user registration."""
+
+from datetime import date, timedelta
+
+import pytest
+from fastapi.testclient import TestClient
+
+from app.main import app
+from app.routers.auth import calculate_age, MIN_AGE, RegisterRequest
+
+
+class TestCalculateAge:
+    """Unit tests for the calculate_age helper."""
+
+    def test_exactly_18(self):
+        today = date(2026, 6, 15)
+        dob = today.replace(year=today.year - 18)
+        assert calculate_age(dob, today=today) == 18
+
+    def test_just_turned_18(self):
+        today = date(2026, 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):
+        today = date(2026, 6, 15)
+        dob = today.replace(year=today.year - 18) + timedelta(days=1)
+        assert calculate_age(dob, today=today) == 17
+
+    def test_leap_day_birthday_before(self):
+        assert calculate_age(date(2000, 2, 29), today=date(2024, 2, 28)) == 23
+
+    def test_leap_day_birthday_after(self):
+        assert calculate_age(date(2000, 2, 29), today=date(2024, 3, 1)) == 24
+
+
+class TestRegisterRequestDob:
+    def test_dob_parsed_from_iso_string(self):
+        req = RegisterRequest(username="u", email="u@example.com", password="p",
+                              date_of_birth="1990-01-01")
+        assert req.date_of_birth == date(1990, 1, 1)
+
+    def test_dob_required(self):
+        with pytest.raises(Exception):
+            RegisterRequest(username="u", email="u@example.com", password="p")
+
+    def test_bad_dob_string_rejected(self):
+        with pytest.raises(Exception):
+            RegisterRequest(username="u", email="u@example.com", password="p",
+                            date_of_birth="not-a-date")
+
+
+class TestRegisterAgeGate:
+    """End-to-end: the /register endpoint computes age from the DOB."""
+
+    def _dob_for_age(self, years: int) -> str:
+        return (date.today().replace(year=date.today().year - years)).isoformat()
+
+    def test_adult_accepted(self):
+        client = TestClient(app)
+        r = client.post("/api/auth/register", json={
+            "username": "gate_adult", "email": "gate_adult@e.com",
+            "password": "secret123", "date_of_birth": self._dob_for_age(25),
+        })
+        assert r.status_code == 201, r.text
+
+    def test_minor_rejected(self):
+        client = TestClient(app)
+        r = client.post("/api/auth/register", json={
+            "username": "gate_minor", "email": "gate_minor@e.com",
+            "password": "secret123", "date_of_birth": self._dob_for_age(15),
+        })
+        assert r.status_code == 403
+        assert str(MIN_AGE) in r.json()["detail"]
+
+    def test_exactly_18_accepted(self):
+        client = TestClient(app)
+        r = client.post("/api/auth/register", json={
+            "username": "gate_18", "email": "gate_18@e.com",
+            "password": "secret123",
+            "date_of_birth": (date.today().replace(year=date.today().year - 18) - timedelta(days=1)).isoformat(),
+        })
+        assert r.status_code == 201, r.text
+
+    def test_future_dob_rejected(self):
+        client = TestClient(app)
+        r = client.post("/api/auth/register", json={
+            "username": "gate_future", "email": "gate_future@e.com",
+            "password": "secret123", "date_of_birth": "2999-01-01",
+        })
+        assert r.status_code == 400
+
+    def test_dob_is_stored(self):
+        client = TestClient(app)
+        dob = self._dob_for_age(30)
+        reg = client.post("/api/auth/register", json={
+            "username": "gate_stored", "email": "gate_stored@e.com",
+            "password": "secret123", "date_of_birth": dob,
+        })
+        assert reg.status_code == 201
+        me = client.get("/api/auth/me", headers={
+            "Authorization": f"Bearer {reg.json()['access_token']}"
+        })
+        assert me.json()["date_of_birth"] == dob

backend/tests/test_auth_endpoints.py

@@ -0,0 +1,251 @@
+"""Integration tests for the auth endpoints (register + login).
+
+These tests hit the real FastAPI app against the real configured database
+(DATABASE_URL -- Postgres via Alembic migrations in CI/dev, not an isolated
+in-memory DB), so they exercise the full stack: Pydantic validation → DB →
+JWT → response. Requires migrations already applied (alembic upgrade head)
+before running.
+"""
+
+import pytest
+from fastapi.testclient import TestClient
+from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
+from sqlalchemy.pool import NullPool
+
+from app.config import settings
+from app.main import app
+from app.database import get_db
+from app.routers.auth import pwd_context
+
+
+# ---------------------------------------------------------------------------
+# Test fixtures
+# ---------------------------------------------------------------------------
+
+@pytest.fixture(autouse=True)
+def _override_db():
+    """Override get_db so the app uses a fresh session per test.
+
+    Deliberately does NOT reuse app.database's shared engine: FastAPI's
+    (sync) TestClient runs each request through anyio's blocking-portal
+    machinery, which can hand different requests different event loops.
+    asyncpg connections are bound to the loop they were created on, so
+    reusing one from the shared engine's connection pool across requests
+    raises "cannot perform operation: another operation is in progress" the
+    moment a test makes more than one request (register-then-login,
+    register-twice, etc.) -- confirmed this is the actual cause, not a bug
+    in the endpoints themselves. NullPool sidesteps it: every checkout is a
+    brand-new connection, never handed to a different loop than the one
+    that opened it.
+    """
+    test_engine = create_async_engine(settings.DATABASE_URL, poolclass=NullPool)
+    test_session_factory = async_sessionmaker(test_engine, expire_on_commit=False)
+
+    async def _get_db():
+        async_session = test_session_factory()
+        try:
+            yield async_session
+            await async_session.commit()
+        except Exception:
+            await async_session.rollback()
+            raise
+        finally:
+            await async_session.close()
+
+    app.dependency_overrides[get_db] = _get_db
+    yield
+    app.dependency_overrides.clear()
+
+
+# ---------------------------------------------------------------------------
+# Register endpoint
+# ---------------------------------------------------------------------------
+
+class TestRegister:
+    """Tests for POST /api/auth/register."""
+
+    def test_register_success(self):
+        """A valid registration returns 201 with a token."""
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/register",
+            json={
+                "username": "newuser",
+                "email": "new@example.com",
+                "password": "secret123",
+                "date_of_birth": "1990-01-01",
+            },
+        )
+        assert resp.status_code == 201
+        data = resp.json()
+        assert "access_token" in data
+        assert data["token_type"] == "bearer"
+
+    def test_register_rejects_under_18(self):
+        """A DOB that computes to under 18 gets a 403 (see test_auth_age_gate
+        for the age-math coverage)."""
+        from datetime import date
+        client = TestClient(app)
+        minor_dob = date.today().replace(year=date.today().year - 14).isoformat()
+        resp = client.post(
+            "/api/auth/register",
+            json={
+                "username": "kid",
+                "email": "kid@example.com",
+                "password": "secret123",
+                "date_of_birth": minor_dob,
+            },
+        )
+        assert resp.status_code == 403
+        assert "at least 18" in resp.json()["detail"]
+
+    def test_register_rejects_duplicate_username(self):
+        """Registering the same username twice returns 409."""
+        client = TestClient(app)
+        # First registration
+        client.post(
+            "/api/auth/register",
+            json={
+                "username": "duplicate",
+                "email": "dup1@example.com",
+                "password": "secret123",
+                "date_of_birth": "1990-01-01",
+            },
+        )
+        # Second registration with same username, different email
+        resp = client.post(
+            "/api/auth/register",
+            json={
+                "username": "duplicate",
+                "email": "dup2@example.com",
+                "password": "secret123",
+                "date_of_birth": "1990-01-01",
+            },
+        )
+        assert resp.status_code == 409
+        assert "Username already registered" in resp.json()["detail"]
+
+    def test_register_rejects_duplicate_email(self):
+        """Registering the same email twice returns 409."""
+        client = TestClient(app)
+        client.post(
+            "/api/auth/register",
+            json={
+                "username": "user1",
+                "email": "same@example.com",
+                "password": "secret123",
+                "date_of_birth": "1990-01-01",
+            },
+        )
+        resp = client.post(
+            "/api/auth/register",
+            json={
+                "username": "user2",
+                "email": "same@example.com",
+                "password": "secret123",
+                "date_of_birth": "1990-01-01",
+            },
+        )
+        assert resp.status_code == 409
+        assert "Email already registered" in resp.json()["detail"]
+
+    def test_register_missing_dob(self):
+        """Missing the required date_of_birth field returns 422."""
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/register",
+            json={
+                "username": "user",
+                "email": "user@example.com",
+                "password": "secret123",
+            },
+        )
+        assert resp.status_code == 422
+
+
+# ---------------------------------------------------------------------------
+# Login endpoint
+# ---------------------------------------------------------------------------
+
+class TestLogin:
+    """Tests for POST /api/auth/login."""
+
+    def _create_user(self, username: str, password: str, email: str = None):
+        """Helper to create a user via register."""
+        client = TestClient(app)
+        if email is None:
+            email = f"{username}@example.com"
+        resp = client.post(
+            "/api/auth/register",
+            json={
+                "username": username,
+                "email": email,
+                "password": password,
+                "date_of_birth": "1990-01-01",
+            },
+        )
+        assert resp.status_code == 201
+        return resp.json()["access_token"]
+
+    def test_login_success(self):
+        """Correct credentials return a token."""
+        self._create_user("loginuser", "correctpass")
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/login",
+            data={"username": "loginuser", "password": "correctpass"},
+        )
+        assert resp.status_code == 200
+        data = resp.json()
+        assert "access_token" in data
+        assert data["token_type"] == "bearer"
+
+    def test_login_wrong_password(self):
+        """Wrong password returns 401."""
+        # Distinct username from test_login_success -- there's no per-test
+        # DB rollback/isolation here (real Postgres via the app's own
+        # dependency-overridden session), so reusing "loginuser" collided
+        # with the user that test already created (409 on register instead
+        # of the intended 401-on-login assertion this test is actually for).
+        self._create_user("loginuser_wrongpass", "correctpass")
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/login",
+            data={"username": "loginuser_wrongpass", "password": "wrongpass"},
+        )
+        assert resp.status_code == 401
+        assert "Incorrect username or password" in resp.json()["detail"]
+
+    def test_login_nonexistent_user(self):
+        """Non-existent user returns 401 (not 404)."""
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/login",
+            data={"username": "nobody", "password": "any"},
+        )
+        assert resp.status_code == 401
+        assert "Incorrect username or password" in resp.json()["detail"]
+
+    def test_login_accepts_form_encoded(self):
+        """Login accepts application/x-www-form-urlencoded (OAuth2)."""
+        self._create_user("formuser", "formpass")
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/login",
+            data={"username": "formuser", "password": "formpass"},
+        )
+        assert resp.status_code == 200
+        assert "access_token" in resp.json()
+
+    def test_login_token_is_valid_jwt(self):
+        """The returned token is a valid JWT that can be decoded."""
+        self._create_user("jwttoken", "jwt123")
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/login",
+            data={"username": "jwttoken", "password": "jwt123"},
+        )
+        token = resp.json()["access_token"]
+        # Verify it's a 3-part JWT
+        parts = token.split(".")
+        assert len(parts) == 3

backend/tests/test_auth_expired_token.py

@@ -0,0 +1,171 @@
+"""Tests for expired-token rejection across auth endpoints.
+
+Covers two distinct expiry paths:
+
+1. An *access* JWT whose ``exp`` claim is in the past must be rejected
+   with 401 by ``GET /api/auth/me`` (jose's built-in ``exp`` validation).
+2. A *refresh* token whose persisted ``expires_at`` is in the past must be
+   rejected with 401 by ``POST /api/auth/refresh`` even though its JWT
+   signature is still valid.
+
+Requires migrations already applied (alembic upgrade head) before running.
+"""
+
+import asyncio
+from datetime import datetime, timedelta, timezone
+
+import pytest
+from fastapi.testclient import TestClient
+from jose import jwt
+from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
+from sqlalchemy.pool import NullPool
+
+from app.config import settings
+from app.main import app
+from app.database import get_db
+from app.models.session import RefreshToken
+
+
+# ---------------------------------------------------------------------------
+# Test fixtures
+# ---------------------------------------------------------------------------
+
+@pytest.fixture(autouse=True)
+def _override_db():
+    """Override get_db so the app uses a fresh session per test."""
+    test_engine = create_async_engine(settings.DATABASE_URL, poolclass=NullPool)
+    test_session_factory = async_sessionmaker(test_engine, expire_on_commit=False)
+
+    async def _get_db():
+        async_session = test_session_factory()
+        try:
+            yield async_session
+            await async_session.commit()
+        except Exception:
+            await async_session.rollback()
+            raise
+        finally:
+            await async_session.close()
+
+    app.dependency_overrides[get_db] = _get_db
+    yield
+    app.dependency_overrides.clear()
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+def _mint_access_token(exp: datetime) -> str:
+    """Mint an RS256 access token with an explicit ``exp`` claim."""
+    return jwt.encode(
+        {"sub": "1", "exp": exp},
+        settings.private_pem,
+        algorithm=settings.ALGORITHM,
+    )
+
+
+def _expire_refresh_token_in_db(token: str) -> None:
+    """Set the persisted refresh token's ``expires_at`` into the past."""
+
+    async def _do():
+        engine = create_async_engine(settings.DATABASE_URL, poolclass=NullPool)
+        session_factory = async_sessionmaker(engine, expire_on_commit=False)
+        async with session_factory() as session:
+            from sqlalchemy import update
+
+            await session.execute(
+                update(RefreshToken)
+                .where(RefreshToken.token == token)
+                .values(expires_at=datetime.now(timezone.utc) - timedelta(hours=1))
+            )
+            await session.commit()
+        await engine.dispose()
+
+    asyncio.run(_do())
+
+
+def _register_user(client: TestClient, username: str) -> str:
+    """Register a user and return its refresh token."""
+    resp = client.post(
+        "/api/auth/register",
+        json={
+            "username": username,
+            "email": f"{username}@example.com",
+            "password": "secret123",
+            "date_of_birth": "1990-01-01",
+        },
+    )
+    assert resp.status_code == 201
+    return resp.json()["refresh_token"]
+
+
+# ---------------------------------------------------------------------------
+# Expired access token (GET /api/auth/me)
+# ---------------------------------------------------------------------------
+
+class TestExpiredAccessToken:
+    def test_expired_access_token_is_rejected_by_me(self):
+        """An access JWT with a past exp claim returns 401 on /me."""
+        client = TestClient(app)
+        expired_token = _mint_access_token(
+            datetime.now(timezone.utc) - timedelta(minutes=5)
+        )
+        resp = client.get(
+            "/api/auth/me",
+            headers={"Authorization": f"Bearer {expired_token}"},
+        )
+        assert resp.status_code == 401
+        assert "Could not validate credentials" in resp.json()["detail"]
+
+    def test_garbage_access_token_is_rejected_by_me(self):
+        """A non-JWT bearer token returns 401 on /me."""
+        client = TestClient(app)
+        resp = client.get(
+            "/api/auth/me",
+            headers={"Authorization": "Bearer not-a-real-jwt"},
+        )
+        assert resp.status_code == 401
+
+    def test_missing_bearer_token_returns_401(self):
+        """No Authorization header at all returns 401 on /me."""
+        client = TestClient(app)
+        resp = client.get("/api/auth/me")
+        assert resp.status_code == 401
+
+
+# ---------------------------------------------------------------------------
+# Expired refresh token (POST /api/auth/refresh)
+# ---------------------------------------------------------------------------
+
+class TestExpiredRefreshToken:
+    def test_expired_refresh_token_is_rejected(self):
+        """A refresh token whose DB expires_at is in the past returns 401."""
+        client = TestClient(app)
+        refresh_token = _register_user(client, "expired_rt_user")
+
+        # Force the persisted record to be expired while its JWT signature
+        # is still valid.
+        _expire_refresh_token_in_db(refresh_token)
+
+        resp = client.post(
+            "/api/auth/refresh",
+            json={"refresh_token": refresh_token},
+        )
+        assert resp.status_code == 401
+        assert "Invalid or expired refresh token" in resp.json()["detail"]
+
+    def test_expired_refresh_token_jwt_is_rejected(self):
+        """A refresh JWT with a past exp claim is rejected before DB lookup."""
+        client = TestClient(app)
+        expired_jwt = jwt.encode(
+            {"sub": "1", "exp": datetime.now(timezone.utc) - timedelta(minutes=5)},
+            settings.private_pem,
+            algorithm=settings.ALGORITHM,
+        )
+        resp = client.post(
+            "/api/auth/refresh",
+            json={"refresh_token": expired_jwt},
+        )
+        assert resp.status_code == 401
+        assert "Invalid or expired refresh token" in resp.json()["detail"]

backend/tests/test_avatar_loadout.py

@@ -0,0 +1,91 @@
+"""Integration tests for GET/PUT /api/avatar/loadout.
+
+Hits the real app against the configured Postgres (same contract as the
+other integration tests -- migrations applied first).
+"""
+
+import pytest
+from fastapi.testclient import TestClient
+
+from app.main import app
+from app.models.avatar_loadout import DEFAULT_LOADOUT
+
+
+def _auth_headers(client: TestClient, username: str) -> dict:
+    resp = client.post(
+        "/api/auth/register",
+        json={
+            "username": username,
+            "email": f"{username}@example.com",
+            "password": "secret123",
+            "date_of_birth": "1990-01-01",
+        },
+    )
+    assert resp.status_code == 201, resp.text
+    return {"Authorization": f"Bearer {resp.json()['access_token']}"}
+
+
+class TestGetLoadout:
+    def test_new_user_gets_the_default(self):
+        client = TestClient(app)
+        headers = _auth_headers(client, "av_default")
+        resp = client.get("/api/avatar/loadout", headers=headers)
+        assert resp.status_code == 200
+        body = resp.json()
+        assert body["is_default"] is True
+        assert body["data"] == DEFAULT_LOADOUT
+
+    def test_requires_auth(self):
+        client = TestClient(app)
+        assert client.get("/api/avatar/loadout").status_code == 401
+
+
+class TestPutLoadout:
+    def test_save_then_read_back(self):
+        client = TestClient(app)
+        headers = _auth_headers(client, "av_save")
+        loadout = {
+            "base_body": "base_human_male_01",
+            "slots": {"hair": "hair_mohawk_01", "accessory": ["accessory_belt_01"]},
+            "skin_tone": {"r": 0.8, "g": 0.6, "b": 0.5, "a": 1.0},
+        }
+        put = client.put("/api/avatar/loadout", headers=headers, json={"data": loadout})
+        assert put.status_code == 200, put.text
+        assert put.json()["is_default"] is False
+
+        got = client.get("/api/avatar/loadout", headers=headers)
+        assert got.status_code == 200
+        assert got.json()["is_default"] is False
+        assert got.json()["data"] == loadout
+
+    def test_put_is_idempotent_replace(self):
+        client = TestClient(app)
+        headers = _auth_headers(client, "av_replace")
+        client.put(
+            "/api/avatar/loadout", headers=headers,
+            json={"data": {"base_body": "base_human_male_01", "slots": {"hair": "hair_mohawk_01"}}},
+        )
+        second = {"base_body": "base_human_male_01", "slots": {"chest": "chest_bandit_01"}}
+        client.put("/api/avatar/loadout", headers=headers, json={"data": second})
+        got = client.get("/api/avatar/loadout", headers=headers)
+        assert got.json()["data"] == second
+
+    def test_rejects_missing_base_body(self):
+        client = TestClient(app)
+        headers = _auth_headers(client, "av_nobase")
+        resp = client.put("/api/avatar/loadout", headers=headers, json={"data": {"slots": {}}})
+        assert resp.status_code == 422
+
+    def test_rejects_non_object_slots(self):
+        client = TestClient(app)
+        headers = _auth_headers(client, "av_badslots")
+        resp = client.put(
+            "/api/avatar/loadout", headers=headers,
+            json={"data": {"base_body": "base_human_male_01", "slots": "nope"}},
+        )
+        assert resp.status_code == 422
+
+    def test_requires_auth(self):
+        client = TestClient(app)
+        resp = client.put("/api/avatar/loadout", json={"data": {"base_body": "x", "slots": {}}})
+        assert resp.status_code == 401

backend/tests/test_gltf_metadata.py

@@ -0,0 +1,220 @@
+"""Tests for the lightweight glTF metadata extraction service."""
+
+import json
+import struct
+import pytest
+
+from app.services.gltf import (
+    extract_gltf_metadata,
+    looks_like_gltf,
+    _parse_glb,
+    _parse_gltf_json,
+)
+
+
+# ---------------------------------------------------------------------------
+# Test data helpers
+# ---------------------------------------------------------------------------
+
+def _make_gltf_json(
+    meshes: int = 1,
+    vertices_per_mesh: int = 24,
+    has_animations: bool = False,
+    images: list[dict] | None = None,
+) -> dict:
+    """Build a minimal glTF JSON structure."""
+    accessors = []
+    meshes_data = []
+    for i in range(meshes):
+        acc_index = len(accessors)
+        accessors.append({
+            "bufferView": 0,
+            "componentType": 5126,  # FLOAT
+            "count": vertices_per_mesh,
+            "type": "VEC3",
+            "max": [1.0, 1.0, 1.0],
+            "min": [-1.0, -1.0, -1.0],
+        })
+        meshes_data.append({
+            "primitives": [{
+                "attributes": {"POSITION": acc_index},
+            }],
+        })
+    gltf = {
+        "asset": {"version": "2.0"},
+        "accessors": accessors,
+        "meshes": meshes_data,
+    }
+    if has_animations:
+        gltf["animations"] = [{"name": "anim1", "channels": [], "samplers": []}]
+    if images:
+        gltf["images"] = images
+    return gltf
+
+
+def _make_glb(gltf_json: dict) -> bytes:
+    """Wrap *gltf_json* in a minimal GLB binary container."""
+    json_bytes = json.dumps(gltf_json).encode("utf-8")
+    json_length = len(json_bytes)
+    # Pad JSON chunk to 4-byte boundary.
+    json_padding = (4 - json_length % 4) % 4
+    json_chunk = json_bytes + b"\x00" * json_padding
+    json_chunk_type = 0x4E4F534A  # "JSON"
+    # No BIN chunk.
+    bin_length = 0
+    bin_chunk_type = 0x004E4942
+    total_length = 12 + 8 + len(json_chunk) + 8 + bin_length
+    header = struct.pack("<III", 0x46546C67, 2, total_length)  # magic, version, length
+    json_header = struct.pack("<II", len(json_chunk), json_chunk_type)
+    if bin_length > 0:
+        bin_header = struct.pack("<II", bin_length, bin_chunk_type)
+    else:
+        bin_header = b""
+    return header + json_header + json_chunk + bin_header
+
+
+# ---------------------------------------------------------------------------
+# looks_like_gltf
+# ---------------------------------------------------------------------------
+
+class TestLooksLikeGltf:
+    def test_glb_magic(self):
+        assert looks_like_gltf(b"glTF\x00\x00\x00\x00") is True
+
+    def test_gltf_extension(self):
+        assert looks_like_gltf(b'{"asset":{"version":"2.0"}}', "model.gltf") is True
+
+    def test_glb_extension(self):
+        assert looks_like_gltf(b"some binary", "model.glb") is True
+
+    def test_json_with_asset_version(self):
+        payload = json.dumps({"asset": {"version": "2.0"}}).encode()
+        assert looks_like_gltf(payload) is True
+
+    def test_plain_json_no_asset(self):
+        payload = json.dumps({"foo": "bar"}).encode()
+        assert looks_like_gltf(payload) is False
+
+    def test_non_json_bytes(self):
+        assert looks_like_gltf(b"\x89PNG\r\n\x1a\n") is False
+
+
+# ---------------------------------------------------------------------------
+# _parse_glb
+# ---------------------------------------------------------------------------
+
+class TestParseGlb:
+    def test_parses_valid_glb(self):
+        gltf_json = _make_gltf_json()
+        glb = _make_glb(gltf_json)
+        result = _parse_glb(glb)
+        assert result["asset"]["version"] == "2.0"
+        assert len(result["meshes"]) == 1
+
+    def test_rejects_too_short(self):
+        with pytest.raises(ValueError, match="too short"):
+            _parse_glb(b"glTF\x00\x00")
+
+    def test_rejects_invalid_magic(self):
+        with pytest.raises(ValueError, match="invalid GLB magic"):
+            _parse_glb(b"NOTglTF\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00")
+
+
+# ---------------------------------------------------------------------------
+# _parse_gltf_json
+# ---------------------------------------------------------------------------
+
+class TestParseGltfJson:
+    def test_parses_valid_gltf(self):
+        gltf_json = _make_gltf_json()
+        result = _parse_gltf_json(json.dumps(gltf_json).encode())
+        assert result["asset"]["version"] == "2.0"
+
+    def test_rejects_non_object(self):
+        with pytest.raises(ValueError, match="root must be an object"):
+            _parse_gltf_json(b"[1, 2, 3]")
+
+
+# ---------------------------------------------------------------------------
+# extract_gltf_metadata  (GLB path)
+# ---------------------------------------------------------------------------
+
+class TestExtractGltfMetadataGlb:
+    def test_basic_glb(self):
+        gltf_json = _make_gltf_json(meshes=1, vertices_per_mesh=24)
+        glb = _make_glb(gltf_json)
+        meta = extract_gltf_metadata(glb)
+        assert meta["mesh_count"] == 1
+        assert meta["vertex_count"] == 24
+        assert meta["has_animation"] is False
+        assert meta["bounding_box_min"] == [-1.0, -1.0, -1.0]
+        assert meta["bounding_box_max"] == [1.0, 1.0, 1.0]
+        assert meta["texture_refs"] == []
+
+    def test_multiple_meshes(self):
+        gltf_json = _make_gltf_json(meshes=3, vertices_per_mesh=12)
+        glb = _make_glb(gltf_json)
+        meta = extract_gltf_metadata(glb)
+        assert meta["mesh_count"] == 3
+        assert meta["vertex_count"] == 36
+
+    def test_with_animation(self):
+        gltf_json = _make_gltf_json(has_animations=True)
+        glb = _make_glb(gltf_json)
+        meta = extract_gltf_metadata(glb)
+        assert meta["has_animation"] is True
+
+    def test_with_external_texture(self):
+        gltf_json = _make_gltf_json(images=[{"uri": "textures/rock.png"}])
+        glb = _make_glb(gltf_json)
+        meta = extract_gltf_metadata(glb)
+        assert meta["texture_refs"] == ["textures/rock.png"]
+
+    def test_with_named_texture(self):
+        gltf_json = _make_gltf_json(images=[{"name": "my_texture"}])
+        glb = _make_glb(gltf_json)
+        meta = extract_gltf_metadata(glb)
+        assert meta["texture_refs"] == ["my_texture"]
+
+    def test_empty_meshes(self):
+        gltf_json = _make_gltf_json(meshes=0)
+        glb = _make_glb(gltf_json)
+        meta = extract_gltf_metadata(glb)
+        assert meta["mesh_count"] == 0
+        assert meta["vertex_count"] == 0
+        assert meta["bounding_box_min"] == [0.0, 0.0, 0.0]
+        assert meta["bounding_box_max"] == [0.0, 0.0, 0.0]
+
+
+# ---------------------------------------------------------------------------
+# extract_gltf_metadata  (plain .gltf JSON path)
+# ---------------------------------------------------------------------------
+
+class TestExtractGltfMetadataGltfJson:
+    def test_plain_gltf(self):
+        gltf_json = _make_gltf_json(meshes=2, vertices_per_mesh=8)
+        raw = json.dumps(gltf_json).encode()
+        meta = extract_gltf_metadata(raw)
+        assert meta["mesh_count"] == 2
+        assert meta["vertex_count"] == 16
+        assert meta["has_animation"] is False
+
+    def test_plain_gltf_with_animation(self):
+        gltf_json = _make_gltf_json(has_animations=True)
+        raw = json.dumps(gltf_json).encode()
+        meta = extract_gltf_metadata(raw)
+        assert meta["has_animation"] is True
+
+
+# ---------------------------------------------------------------------------
+# Error handling
+# ---------------------------------------------------------------------------
+
+class TestExtractGltfMetadataErrors:
+    def test_invalid_glb(self):
+        with pytest.raises(ValueError):
+            extract_gltf_metadata(b"not a glb")
+
+    def test_invalid_gltf_json(self):
+        with pytest.raises(ValueError):
+            _parse_gltf_json(b"[1, 2, 3]")

backend/tests/test_rate_limit.py

@@ -0,0 +1,56 @@
+"""The auth endpoints are rate-limited per client IP."""
+
+import pytest
+from fastapi.testclient import TestClient
+
+from app import rate_limit
+from app.config import settings
+from app.main import app
+
+
+@pytest.fixture(autouse=True)
+def _clean_limiter():
+    # This module tests the limiter itself: force it on (the checkpoint
+    # runner disables it suite-wide via RATE_LIMIT_ENABLED) and start each
+    # test from an empty window.
+    prev = settings.RATE_LIMIT_ENABLED
+    settings.RATE_LIMIT_ENABLED = True
+    rate_limit.reset_all()
+    yield
+    rate_limit.reset_all()
+    settings.RATE_LIMIT_ENABLED = prev
+
+
+def test_login_is_limited_after_the_threshold():
+    client = TestClient(app)
+    codes = []
+    for i in range(15):
+        r = client.post("/api/auth/login", data={"username": f"nobody{i}", "password": "x"})
+        codes.append(r.status_code)
+    # First 10 get through to the (failing) auth check; the rest are 429.
+    assert codes[:10] == [401] * 10
+    assert 429 in codes[10:]
+    assert codes[-1] == 429
+
+
+def test_register_shares_the_same_bucket():
+    client = TestClient(app)
+    # Burn the budget on login...
+    for i in range(10):
+        client.post("/api/auth/login", data={"username": f"x{i}", "password": "y"})
+    # ...register from the same IP is now blocked too.
+    r = client.post("/api/auth/register", json={
+        "username": "rl_user", "email": "rl@e.com",
+        "password": "secret123", "date_of_birth": "1990-01-01",
+    })
+    assert r.status_code == 429
+    assert "Retry-After" in r.headers
+
+
+def test_limiter_window_is_per_key():
+    limiter = rate_limit.SlidingWindowLimiter(max_hits=2, window_seconds=60)
+    limiter.check("a")
+    limiter.check("a")
+    with pytest.raises(Exception):
+        limiter.check("a")
+    limiter.check("b")  # different key, unaffected

backend/tests/test_refresh_endpoint.py

@@ -0,0 +1,201 @@
+"""Tests for the POST /api/auth/refresh endpoint.
+
+These tests exercise the full stack: register → get refresh token →
+refresh → new access token.  Requires migrations already applied
+(alembic upgrade head) before running.
+"""
+
+import pytest
+from fastapi.testclient import TestClient
+from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
+from sqlalchemy.pool import NullPool
+
+from app.config import settings
+from app.main import app
+from app.database import get_db
+
+
+# ---------------------------------------------------------------------------
+# Test fixtures
+# ---------------------------------------------------------------------------
+
+@pytest.fixture(autouse=True)
+def _override_db():
+    """Override get_db so the app uses a fresh session per test."""
+    test_engine = create_async_engine(settings.DATABASE_URL, poolclass=NullPool)
+    test_session_factory = async_sessionmaker(test_engine, expire_on_commit=False)
+
+    async def _get_db():
+        async_session = test_session_factory()
+        try:
+            yield async_session
+            await async_session.commit()
+        except Exception:
+            await async_session.rollback()
+            raise
+        finally:
+            await async_session.close()
+
+    app.dependency_overrides[get_db] = _get_db
+    yield
+    app.dependency_overrides.clear()
+
+
+# ---------------------------------------------------------------------------
+# Refresh endpoint tests
+# ---------------------------------------------------------------------------
+
+class TestRefresh:
+    """Tests for POST /api/auth/refresh."""
+
+    def _register_user(self, username: str, password: str, email: str = None):
+        """Helper to register a user and return the refresh token."""
+        client = TestClient(app)
+        if email is None:
+            email = f"{username}@example.com"
+        resp = client.post(
+            "/api/auth/register",
+            json={
+                "username": username,
+                "email": email,
+                "password": password,
+                "date_of_birth": "1990-01-01",
+            },
+        )
+        assert resp.status_code == 201
+        return resp.json()["refresh_token"]
+
+    def test_refresh_success(self):
+        """A valid refresh token returns a new access token."""
+        refresh_token = self._register_user("refep_refreshuser", "secret123")
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/refresh",
+            json={"refresh_token": refresh_token},
+        )
+        assert resp.status_code == 200
+        data = resp.json()
+        assert "access_token" in data
+        assert data["token_type"] == "bearer"
+        # The refresh token in the response is the same one we sent
+        assert data["refresh_token"] == refresh_token
+
+    def test_refresh_returns_different_access_token(self):
+        """Refreshing produces a new access token (different from any previous)."""
+        refresh_token = self._register_user("refep_refreshtoken", "secret123")
+        client = TestClient(app)
+
+        # First refresh
+        resp1 = client.post(
+            "/api/auth/refresh",
+            json={"refresh_token": refresh_token},
+        )
+        assert resp1.status_code == 200
+        access_token_1 = resp1.json()["access_token"]
+
+        # Second refresh
+        resp2 = client.post(
+            "/api/auth/refresh",
+            json={"refresh_token": refresh_token},
+        )
+        assert resp2.status_code == 200
+        access_token_2 = resp2.json()["access_token"]
+
+        # Each refresh should produce a new access token
+        assert access_token_1 != access_token_2
+
+    def test_refresh_invalid_token(self):
+        """An invalid (garbage) refresh token returns 401."""
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/refresh",
+            json={"refresh_token": "not.a.jwt.token"},
+        )
+        assert resp.status_code == 401
+        assert "Invalid or expired refresh token" in resp.json()["detail"]
+
+    def test_refresh_empty_body(self):
+        """Missing refresh_token field returns 422 validation error."""
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/refresh",
+            json={},
+        )
+        assert resp.status_code == 422
+
+    def test_refresh_missing_field(self):
+        """No body at all returns 422."""
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/refresh",
+            content="{}",
+            headers={"Content-Type": "application/json"},
+        )
+        assert resp.status_code == 422
+
+    def test_refresh_with_login_token(self):
+        """A refresh token obtained from login also works for /refresh."""
+        client = TestClient(app)
+        # Register first
+        client.post(
+            "/api/auth/register",
+            json={
+                "username": "refep_loginrefuser",
+                "email": "loginref@example.com",
+                "password": "secret123",
+                "date_of_birth": "1990-01-01",
+            },
+        )
+        # Login to get a refresh token
+        login_resp = client.post(
+            "/api/auth/login",
+            data={"username": "refep_loginrefuser", "password": "secret123"},
+        )
+        assert login_resp.status_code == 200
+        refresh_token = login_resp.json()["refresh_token"]
+
+        # Use it to refresh
+        resp = client.post(
+            "/api/auth/refresh",
+            json={"refresh_token": refresh_token},
+        )
+        assert resp.status_code == 200
+        assert "access_token" in resp.json()
+
+    def test_refresh_access_token_is_valid_jwt(self):
+        """The access token returned by /refresh is a valid JWT."""
+        from jose import jwt
+
+        refresh_token = self._register_user("refep_jwttoken", "secret123")
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/refresh",
+            json={"refresh_token": refresh_token},
+        )
+        assert resp.status_code == 200
+        access_token = resp.json()["access_token"]
+
+        # Verify it's a 3-part JWT
+        parts = access_token.split(".")
+        assert len(parts) == 3
+
+        # Verify it decodes with the public key
+        payload = jwt.decode(
+            access_token,
+            settings.public_pem,
+            algorithms=[settings.ALGORITHM],
+        )
+        assert "sub" in payload
+        assert "exp" in payload
+
+    def test_refresh_expires_minutes_in_response(self):
+        """The response includes access_token_expires_minutes."""
+        refresh_token = self._register_user("refep_expiretest", "secret123")
+        client = TestClient(app)
+        resp = client.post(
+            "/api/auth/refresh",
+            json={"refresh_token": refresh_token},
+        )
+        assert resp.status_code == 200
+        assert "access_token_expires_minutes" in resp.json()
+        assert resp.json()["access_token_expires_minutes"] == settings.ACCESS_TOKEN_EXPIRE_MINUTES

backend/tests/test_refresh_token_jti.py

@@ -0,0 +1,79 @@
+"""Tests for refresh token uniqueness (jti claim) and model column length."""
+
+import uuid
+from datetime import datetime, timedelta, timezone
+
+import pytest
+from jose import jwt
+
+from app.config import settings
+from app.routers.auth import _create_refresh_token
+from app.models.session import RefreshToken
+
+
+class TestRefreshTokenJtiUniqueness:
+    """Verify that _create_refresh_token produces unique tokens even when
+    called with identical data in rapid succession (issue #1 from review)."""
+
+    def test_two_calls_produce_different_tokens(self):
+        """Two calls with the same sub produce different JWTs because of jti."""
+        token_a = _create_refresh_token({"sub": "42"})
+        token_b = _create_refresh_token({"sub": "42"})
+        assert token_a != token_b
+
+    def test_jti_is_valid_uuid(self):
+        """The jti claim inside the refresh token is a valid UUID."""
+        token = _create_refresh_token({"sub": "1"})
+        payload = jwt.decode(
+            token,
+            settings.public_pem,
+            algorithms=[settings.ALGORITHM],
+        )
+        assert "jti" in payload
+        # Verify it parses as a UUID (raises ValueError if not)
+        uuid.UUID(payload["jti"])
+
+    def test_each_token_has_unique_jti(self):
+        """Generate 100 tokens for the same user — all jtis must differ."""
+        jtis = set()
+        for _ in range(100):
+            token = _create_refresh_token({"sub": "999"})
+            payload = jwt.decode(
+                token,
+                settings.public_pem,
+                algorithms=[settings.ALGORITHM],
+            )
+            jtis.add(payload["jti"])
+        assert len(jtis) == 100
+
+    def test_jti_survives_decode(self):
+        """The jti claim is present and correct after decode."""
+        token = _create_refresh_token({"sub": "7"})
+        payload = jwt.decode(
+            token,
+            settings.public_pem,
+            algorithms=[settings.ALGORITHM],
+        )
+        assert payload["sub"] == "7"
+        assert "jti" in payload
+        assert "exp" in payload
+
+
+class TestRefreshTokenModelColumnLength:
+    """Verify the model's token column length matches the migration (issue #2)."""
+
+    def test_token_column_has_length_512(self):
+        """RefreshToken.token column should be String(512), not unbounded."""
+        from sqlalchemy import inspect
+
+        # Get the column definition from the model's table
+        column = RefreshToken.__table__.columns["token"]
+        # The type should be String with length 512
+        assert column.type.length == 512
+
+    def test_token_column_type_is_string(self):
+        """The token column should be a String type."""
+        from sqlalchemy import String as SAString
+
+        column = RefreshToken.__table__.columns["token"]
+        assert isinstance(column.type, SAString)

backend/tests/test_world_join.py

@@ -0,0 +1,54 @@
+"""Tests for POST /api/worlds/{id}/join.
+
+The happy path spawns a real Godot process, so it's covered by a manual /
+checkpoint integration test, not here. These cover the envelope: auth,
+visibility, and the 503 when orchestration is disabled (the default).
+"""
+
+import pytest
+from fastapi.testclient import TestClient
+
+from app.main import app
+
+
+def _auth(client: TestClient, name: str) -> tuple[dict, int]:
+    r = client.post("/api/auth/register", json={
+        "username": name, "email": f"{name}@e.com", "password": "secret123", "date_of_birth": "1990-01-01",
+    })
+    assert r.status_code == 201, r.text
+    headers = {"Authorization": f"Bearer {r.json()['access_token']}"}
+    me = client.get("/api/users/me", headers=headers)
+    return headers, me.json()["id"]
+
+
+def _make_world(client: TestClient, headers: dict, visibility: str = "public") -> int:
+    r = client.post("/api/worlds/", headers=headers, json={"name": "W", "visibility": visibility})
+    assert r.status_code == 201, r.text
+    return r.json()["id"]
+
+
+class TestJoinWorld:
+    def test_requires_auth(self):
+        client = TestClient(app)
+        assert client.post("/api/worlds/1/join").status_code == 401
+
+    def test_unknown_world_is_404(self):
+        client = TestClient(app)
+        headers, _ = _auth(client, "join_404")
+        assert client.post("/api/worlds/999999/join", headers=headers).status_code == 404
+
+    def test_private_world_of_another_user_is_404(self):
+        client = TestClient(app)
+        owner_headers, _ = _auth(client, "join_owner")
+        wid = _make_world(client, owner_headers, "private")
+        other_headers, _ = _auth(client, "join_other")
+        assert client.post(f"/api/worlds/{wid}/join", headers=other_headers).status_code == 404
+
+    def test_disabled_orchestration_returns_503(self):
+        # GAME_SERVERS_ENABLED defaults to False in tests.
+        client = TestClient(app)
+        headers, _ = _auth(client, "join_503")
+        wid = _make_world(client, headers, "public")
+        r = client.post(f"/api/worlds/{wid}/join", headers=headers)
+        assert r.status_code == 503
+        assert "not enabled" in r.json()["detail"]

docs/architecture/avatar.md

@@ -449,6 +449,37 @@ The catalog is a JSON manifest mapping asset ids to metadata and resource paths:
 
 ---
 
+## 9a. Loadout Persistence (implemented, PC3 Phase 1)
+
+**Storage.** One row per user in `avatar_loadouts` (`user_id` PK/FK,
+`data` JSONB, timestamps). The entire loadout is stored as a single JSON
+document in the exact shape the client's `AvatarLoadout.to_json()` emits
+(`{"base_body": str, "slots": {...}, "skin_tone"?: {r,g,b,a}}`) rather than
+exploded into columns.
+
+**Why one JSON blob, not columns.** The server has no copy of the asset
+catalog (`assets/avatars/catalog.json` ships with the client). It therefore
+cannot meaningfully validate *which* asset belongs in *which* slot, whether
+an asset exists, or slot-exclusivity rules — that validation stays on the
+client (`AvatarLoadout.validate()` against the loaded `AvatarCatalog`). The
+server enforces only the envelope: a JSON object with a non-empty string
+`base_body`, an object `slots`, and a sane size cap. Keeping the schema
+opaque to the server also means catalog/loadout-shape changes don't need a
+migration.
+
+**Endpoints** (`/api/avatar`, bearer auth):
+
+| Method | Path | Behaviour |
+|---|---|---|
+| `GET` | `/loadout` | The user's saved loadout, or the server default (`{"base_body": "base_human_male_01", "slots": {}}`, `is_default: true`) if they have never saved one. |
+| `PUT` | `/loadout` | Replace the user's loadout (full document, not a patch). |
+
+**Defaults.** A brand-new account has no row; `GET` returns
+`models.avatar_loadout.DEFAULT_LOADOUT` with `is_default: true` so the client
+can distinguish "never customised" from "customised back to the base look".
+
+---
+
 ## 10. Summary
 
 | Concern                | Decision                                              |

docs/architecture/content_moderation.md

@@ -227,18 +227,33 @@ An account has an **age verification status**:
 
 ### 5.2 Tier 1 — Self-Declaration Flow
 
+> **Implemented, PC3 Phase 3.** `POST /api/auth/register` now takes a real
+> `date_of_birth` (ISO `YYYY-MM-DD`), not the throwaway `over_18` boolean it
+> had before. The server computes age (`auth.calculate_age`) and rejects
+> anyone under `auth.MIN_AGE` (18) with a **403** — this platform is
+> adults-only, so there is no "minor, restricted" tier here (the 13+ rows
+> below are the general design, not the current gate). A future-in-the-past
+> or nonsensical date is a **400**. The DOB is stored on the user row and
+> surfaced only back to that user (`/api/auth/me`), never to other players.
+>
+> **Limitation, stated plainly:** this is still self-attested — a determined
+> user can enter a false DOB. It is a concrete, stored, legally-meaningful
+> data point (matching how most platforms gate before adding hard checks)
+> and the seam for Tier 2. Encryption-at-rest for the DOB column and the
+> Tier 2 ID-check hook below are **not yet implemented**.
+
 ```
 User submits { date_of_birth }
         │
         ▼
-Server validates format & plausibility (age 13–120, not in future)
+Server validates format & plausibility (real date, not in future)
         │
         ▼
 Compute age from DOB
         │
         ▼
-age >= 18 ──► status = self_declared (adult)
+age >= 18 ──► status = self_declared (adult)   ← the current gate
-age >= 13 ──► status = self_declared (minor, restricted)
+age >= 13 ──► status = self_declared (minor, restricted)   ← design only
 age <  13 ──► status = rejected (below minimum platform age)
 ```
 

docs/architecture/editor.md

@@ -0,0 +1,369 @@
+# Editor Architecture: Godot Editor Plugin vs. In-Game Editor
+
+> **Status:** Proposed
+> **Owner:** Platform team
+> **Related:** World chunk data format & persistence, server authority + client
+> prediction, content moderation & age verification, avatar component system
+> **Godot version:** 4.6.2 stable
+
+## 1. Overview
+
+This document evaluates the two primary ways to build the **world/level
+authoring tool** for **agp-game**:
+
+- **(a) Godot editor plugin** — extend the Godot editor itself with custom
+  panels, dock widgets, and tools that operate on the project's scenes and
+  resources.
+- **(b) In-game editor** — a fully custom editor built as game UI (Godot
+  `Control` nodes) that runs inside the running game, editing the game's own
+  world data.
+
+The goal is to pick the approach that best fits the platform's constraints:
+a **server-authoritative** multiplayer game where the **world is stored as
+versioned chunks** (see `world.md`), content is **moderation-flagged** (see
+`content_moderation.md`), and the client is a **shipped binary** that players
+run (not a dev tool).
+
+This document is a **decision record**: it lays out the trade-offs, gives a
+clear recommendation, and defines the resulting architecture boundaries.
+
+---
+
+## 2. Context & Constraints
+
+Before comparing the two approaches, we must fix the constraints that drive the
+decision. These come from the existing architecture docs.
+
+### 2.1 The World Is Data, Not Scenes
+
+`world.md` defines the world as **chunk data** (JSON for authoring, binary for
+runtime/network), persisted in SQLite on the server. A chunk is the atomic unit
+of load, save, and stream. The **server is the only writer** to the store;
+clients submit **deltas** against a `base_revision` and the server validates and
+applies them.
+
+**Implication:** The editor's output is **chunk payloads**, not `.tscn` scene
+files. Whatever editor we build must serialize to the chunk contract, not to
+Godot scene resources.
+
+### 2.2 Server-Authoritative & Moderation-Aware
+
+- The server validates every edit (schema, bounds, moderation) before
+  persisting (`world.md` §5.4).
+- Content carries **content flags** aggregated from referenced assets/scripts
+  (`content_moderation.md` §3). Mature content is gated behind age verification.
+- The client receives a **content manifest** and never loads content not in it.
+
+**Implication:** An editor that runs on a **player's machine** cannot be the
+authority on what gets published. Editing must go through the server's
+validation pipeline, and the editor must surface moderation flags.
+
+### 2.3 The Client Is a Shipped Binary
+
+The game is a multiplayer product. Players run a **release build**. The Godot
+editor is a **development tool** that players do not have.
+
+**Implication:** If authoring is a first-class *player* feature (user-generated
+content), the editor must ship inside the game binary. If authoring is a
+*developer/platform* feature, it can live in the editor.
+
+### 2.4 Two Distinct Audiences
+
+The evaluation must separate two audiences, because they have opposite needs:
+
+| Audience | Who | Where they run | What they build |
+|----------|-----|----------------|-----------------|
+| **Platform/dev** | The team building the game | Godot editor (dev machines) | Base worlds, rooms, templates, test levels |
+| **Players (UGC)** | End users | The shipped game | Their own rooms/worlds, published to the server |
+
+The two approaches map cleanly onto these audiences, and the right answer is
+likely **both** — but with a clear primary recommendation.
+
+---
+
+## 3. Approach (a): Godot Editor Plugin
+
+### 3.1 What It Is
+
+A Godot editor plugin is a set of scripts (and optionally scenes) that extend
+the editor via the `EditorPlugin` API. It can add:
+
+- **Dock panels** (`add_control_to_dock`) — e.g., a chunk/tile palette panel.
+- **Toolbar buttons** (`add_control_to_container`).
+- **Inspector plugins** (`EditorInspectorPlugin`) — custom property editors.
+- **Import plugins** (`EditorImportPlugin`) — custom asset importers.
+- **Scene/Node plugins** (`EditorNode3DGizmoPlugin`) — custom gizmos.
+- **Menu entries** (`add_tool_menu_item`).
+
+Plugins are enabled per-project via `project.godot` (`[editor_plugins]`).
+
+### 3.2 Pros
+
+- **Full editor power for free:** You get the scene tree, inspector, viewport
+  navigation, undo/redo, gizmos, and asset pipeline — all battle-tested.
+- **Native Godot editing:** Editing `.tscn` scenes, materials, and nodes is
+  exactly what the editor is built for. Great for authoring **base content**
+  (rooms, templates, avatar base bodies).
+- **Fast iteration for devs:** The platform team can build and test levels
+  directly in the tool they already use.
+- **Undo/redo, selection, snapping** come from the editor's `EditorUndoRedoManager`.
+- **No runtime footprint:** Editor-only code is stripped from export builds
+  (`@tool` scripts and editor plugins are not shipped to players).
+
+### 3.3 Cons
+
+- **Not available to players.** Players don't run the Godot editor. Any
+  player-facing UGC authoring cannot use this approach.
+- **Tied to the editor's UX.** You inherit the editor's look and interaction
+  model; deep customization is limited by what the editor API exposes.
+- **Editor API churn.** `EditorPlugin` APIs change between Godot versions;
+  plugins are more brittle across upgrades than game code.
+- **Scene-centric, not data-centric.** The editor is optimized for scenes and
+  resources. Our world is **chunk data** (`world.md`). We'd have to build a
+  translation layer (scene ↔ chunk) and keep it in sync — a real source of
+  drift.
+- **Single-user, local.** The editor edits local files. It does not natively
+  talk to our server-authoritative chunk store or the moderation pipeline.
+- **Headless/CI friction.** Validating plugin behavior in CI requires running
+  the editor headless, which is heavier than testing game code.
+
+### 3.4 Fit for Our Constraints
+
+- **Platform/dev authoring:** Excellent. This is the natural home for building
+  base worlds, rooms, and templates.
+- **Player UGC:** Not applicable. Players cannot run the editor.
+- **Server-authoritative chunk store:** Poor fit natively. The editor edits
+  local scenes; we'd bolt on a chunk export/import and a server sync layer.
+
+---
+
+## 4. Approach (b): In-Game Editor
+
+### 4.1 What It Is
+
+A fully custom editor built as **game UI** — Godot `Control` nodes (panels,
+buttons, toolbars) that run inside the running game. It edits the game's own
+world data model (chunks) and submits edits through the normal server pipeline.
+
+### 4.2 Pros
+
+- **Ships to players.** The editor is part of the game binary, so **player UGC
+  authoring is possible** — the core requirement for a user-generated-content
+  platform.
+- **Data-native.** The editor operates directly on the **chunk model**
+  (`world.md`), so there is no scene↔chunk translation layer and no drift.
+- **Server-authoritative by construction.** Edits go through the same
+  `request_chunk_edit` RPCs as gameplay, so validation, revisioning, and
+  moderation apply uniformly. The editor cannot bypass the server.
+- **Moderation-aware.** Because edits flow through the server, content flags are
+  computed and enforced at the boundary (`content_moderation.md` §4). The editor
+  can surface flags and gate mature content.
+- **One codebase, one UX.** The editor uses the same UI toolkit and art style as
+  the game; no separate editor theme to maintain.
+- **Testable in CI.** The editor is ordinary game code; it can be exercised
+  headlessly and unit-tested like any other system.
+
+### 4.3 Cons
+
+- **We build everything.** No free scene tree, inspector, gizmos, or undo/redo.
+  We must implement selection, snapping, undo/redo, viewport navigation, and
+  property editing ourselves.
+- **Runtime footprint.** Editor UI ships in the binary (though it can be gated
+  behind a feature flag / separate scene that is only instantiated on demand).
+- **More upfront work.** A usable in-game editor is a large feature; it needs
+  its own architecture (tool modes, gizmos, palette, inspector).
+- **Not ideal for deep asset authoring.** Modeling a mesh or authoring a
+  material is better done in the Godot editor / DCC tools. The in-game editor
+  should focus on **world composition** (placing tiles and objects), not asset
+  creation.
+
+### 4.4 Fit for Our Constraints
+
+- **Platform/dev authoring:** Workable but not ideal for deep asset work.
+- **Player UGC:** The **only** viable approach. Players can only author through
+  the shipped game.
+- **Server-authoritative chunk store:** Excellent fit. The editor is a client
+  that submits validated deltas.
+
+---
+
+## 5. Comparison Matrix
+
+| Criterion | (a) Editor plugin | (b) In-game editor |
+|-----------|-------------------|--------------------|
+| Ships to players | ❌ No | ✅ Yes |
+| Player UGC authoring | ❌ Impossible | ✅ Core capability |
+| World data model fit | ⚠️ Scene-centric; needs translation layer | ✅ Chunk-native |
+| Server-authoritative edits | ⚠️ Bolted on | ✅ Native (same RPCs) |
+| Moderation enforcement | ⚠️ Manual | ✅ At the boundary |
+| Free editor features (undo, gizmos, inspector) | ✅ Rich | ❌ Build ourselves |
+| Runtime footprint | ✅ None (stripped from export) | ⚠️ Ships in binary (gated) |
+| Dev iteration speed | ✅ Fast | ⚠️ Slower to build |
+| Deep asset authoring (mesh/material) | ✅ Native | ❌ Out of scope |
+| CI testability | ⚠️ Heavier (headless editor) | ✅ Ordinary game code |
+| Editor API churn risk | ⚠️ Higher | ✅ None (game code) |
+
+---
+
+## 6. Recommendation
+
+**Primary recommendation: build the in-game editor (b) as the platform's
+authoring surface, and use a lightweight Godot editor plugin (a) only as an
+internal dev convenience.**
+
+### 6.1 Rationale
+
+1. **Player UGC is the deciding factor.** The platform's value proposition is
+   user-generated content (rooms, worlds, avatars). Players cannot run the Godot
+   editor, so **only an in-game editor can deliver player authoring**. This is a
+   hard requirement that the editor-plugin approach cannot meet.
+
+2. **The world is data, and the in-game editor is data-native.** `world.md`
+   defines chunks as the atomic unit. An in-game editor edits chunks directly
+   and submits them through the server pipeline. An editor plugin would force a
+   scene↔chunk translation layer that is a constant source of drift and bugs.
+
+3. **Server authority and moderation fall out naturally.** Because in-game
+   edits use the same `request_chunk_edit` RPCs as gameplay, validation,
+   revisioning, optimistic concurrency, and content-flag enforcement
+   (`content_moderation.md`) apply uniformly. The editor cannot bypass the
+   server — which is exactly what a moderation-aware UGC platform needs.
+
+4. **The editor-plugin's strengths are not what we need.** Its free features
+   (scene tree, inspector, gizmos) are for editing Godot scenes and resources.
+   Our authoring is world composition against a chunk contract, not scene
+   editing. The plugin's main win — deep asset authoring — is better served by
+   DCC tools and the Godot editor for the *platform team*, not by a plugin we
+   must maintain.
+
+### 6.2 The Role of the Editor Plugin (Dev Convenience Only)
+
+We still recommend a **small, optional** editor plugin for the **platform team**
+to author **base content** (base rooms, templates, avatar base bodies, test
+levels) directly in the Godot editor. This is a dev-time convenience, not a
+product feature:
+
+- It can export a scene/resource as a **chunk** (reusing the same encoder as the
+  in-game editor) so dev-authored content flows into the same pipeline.
+- It is **not shipped** to players and is **not** the authoring surface for UGC.
+- It should be kept thin to minimize editor-API churn risk.
+
+### 6.3 Scope Boundary
+
+To keep the in-game editor tractable, define its scope clearly:
+
+- **In scope (world composition):** placing tiles, placing static/dynamic
+  objects, setting transforms, editing object properties, saving/loading chunks,
+  submitting edits to the server, showing moderation flags.
+- **Out of scope (asset creation):** modeling meshes, authoring materials,
+  rigging avatars. These are done in DCC tools / the Godot editor and imported
+  as catalog assets (see `avatar.md` §7). The in-game editor **references**
+  catalog assets by id; it does not create them.
+
+---
+
+## 7. Resulting Architecture
+
+### 7.1 Shared Editor Core
+
+Both the in-game editor and the (optional) dev plugin should share a single
+**editor core** that operates on the chunk model. This avoids two divergent
+implementations.
+
+```
+EditorCore (shared, data-native)
+├── ChunkEditorModel      # in-memory chunk being edited (tiles, objects, flags)
+├── ChunkEncoder          # JSON/binary encode/decode (world.md §3)
+├── EditSession           # base_revision tracking, delta generation
+├── EditSubmitter         # request_chunk_edit RPC wrapper + conflict handling
+├── UndoRedoStack         # command pattern over chunk mutations
+├── SelectionManager      # selected tiles/objects
+├── ToolRegistry          # brush, object-place, select, erase, etc.
+└── ModerationView        # surfaces content flags; gates mature content
+```
+
+### 7.2 In-Game Editor (Primary)
+
+```
+InGameEditor (Control-based UI, shipped in binary, gated by feature flag)
+├── EditorViewport        # custom 2D/3D viewport with camera navigation
+├── Toolbar               # tool mode switcher
+├── PalettePanel          # tile/object palette (from catalog)
+├── InspectorPanel        # property editor for selected object
+├── ChunkBrowser          # load/save chunks, list rooms
+└── EditorCore            # shared core (above)
+```
+
+- Instantiated only when the player enters "build mode" (a separate scene /
+  feature flag), so the runtime footprint is negligible during normal play.
+- Submits edits via `request_chunk_edit`; handles `chunk_edit_result` conflicts
+  by re-fetching and re-applying (`world.md` §5.4).
+
+### 7.3 Dev Editor Plugin (Optional, Thin)
+
+```
+DevChunkPlugin (EditorPlugin, dev-only, not shipped)
+├── Dock panel: "Chunk Export"
+├── Reads the current scene / selected nodes
+├── Maps scene content → chunk model (via EditorCore.ChunkEncoder)
+└── Exports a .chunk.json / submits to a dev server
+```
+
+Kept thin to minimize editor-API churn. Its only job is to let the platform team
+author base content in the editor and push it into the same chunk pipeline.
+
+### 7.4 Data Flow
+
+```
+[In-game editor]  --request_chunk_edit(delta, base_revision)-->  [Server]
+        ^                                                          | validate
+        |                                                          | apply
+        +--chunk_edit_result(ok/new_revision | conflict)-----------| persist
+                                                                   v
+                                                              SQLite (world.db)
+
+[Dev plugin]  --export chunk JSON-->  [EditorCore.ChunkEncoder]  -->  [Server]
+```
+
+Both paths converge on the **same server validation pipeline**, so moderation
+and revisioning are uniform regardless of authoring surface.
+
+---
+
+## 8. Risks & Mitigations
+
+| Risk | Mitigation |
+|------|------------|
+| In-game editor is a large build | Scope it to world composition (§6.3); reuse EditorCore; ship behind a feature flag |
+| Custom viewport/gizmos are hard | Start with a 2D tile editor (matches `CHUNK_SIZE_Z=1` default); add 3D later |
+| Undo/redo complexity | Use a command pattern over chunk mutations; test headlessly |
+| Editor-plugin API churn | Keep the plugin thin; treat it as dev-only convenience, not a product surface |
+| Drift between dev plugin and in-game editor | Both use the same `EditorCore`/`ChunkEncoder` |
+| Players bypass moderation | Impossible by construction: edits go through server validation |
+
+---
+
+## 9. Open Questions / Future Work
+
+- **3D editing:** The default world is flat (`CHUNK_SIZE_Z=1`). A 3D in-game
+  editor (volumetric chunks) is future work (`world.md` §8).
+- **Collaborative editing:** Multiple players editing the same chunk concurrently
+  — the optimistic-concurrency model already supports it, but the UX (live
+  cursors, conflict resolution) is unspecified.
+- **Template library:** A curated set of room templates players can start from.
+- **Publish/review flow:** How a player's authored room enters the moderation
+  review queue (`content_moderation.md` §6) and becomes publicly joinable.
+
+---
+
+## 10. Summary
+
+| Concern | Decision |
+|---------|----------|
+| Primary authoring surface | **In-game editor** (ships to players, enables UGC) |
+| Dev authoring convenience | Thin, optional **editor plugin** (not shipped) |
+| World data model | Both operate on the **chunk model** via a shared `EditorCore` |
+| Server authority | Edits go through `request_chunk_edit`; server validates |
+| Moderation | Enforced at the server boundary for both paths |
+| In-game editor scope | World composition only; asset creation is out of scope |
+| Runtime footprint | Editor gated behind a feature flag / separate scene |

docs/architecture/networking.md

@@ -237,6 +237,62 @@ snapshot_state:
 
 ---
 
+## 7a. Server Orchestration (implemented, PC3 Phase 2)
+
+**One dedicated server process per world**, spawned on demand.
+
+```
+client                    backend (single worker)              host
+  │  POST /api/worlds/{id}/join  (bearer JWT)                    │
+  │ ───────────────────────────▶ GameServerSupervisor           │
+  │                              ensure_server(world_id):        │
+  │                                if none running for world ─── spawn:
+  │                                                              godot --headless
+  │                                                              res://scenes/server.tscn --
+  │                                                              --port <p> --world <id>
+  │                                                              --status-file <path>
+  │  ◀─────────────────────────── { host, port, world_id }       │
+  │                                                              │
+  │  ENet connect  host:port ───────────────────────────────────▶ dedicated server
+```
+
+- **Supervisor** (`backend/app/services/game_servers.py`): in-process singleton,
+  so the backend MUST run single-worker. Keys servers by `world_id`. Allocates
+  ports from `GAME_SERVER_PORT_MIN..MAX`. A background reaper kills a world's
+  server once its **status file** (`{players, tick, updated}`, rewritten by the
+  server ~1×/s) reports `players == 0` for `GAME_SERVER_IDLE_TIMEOUT_SECONDS`.
+  No crash-restart — the next join respawns.
+- **Enable flag:** `GAME_SERVERS_ENABLED` (default off). The checkpoint/playtest
+  launcher (`pm/checkpoint_ops.py`) turns it on, passes `GODOT_BIN`,
+  `GAME_PROJECT_DIR`, and `GAME_SERVER_HOST` (the LAN IP baked into the `.exe`).
+  A backend with it off returns **503** from `/join`, and the client falls back
+  to local single-player.
+- **Per-world content:** all worlds currently load the same test level (M2/M7
+  work). `world_id` still scopes a distinct process + session.
+
+### 7b. Client play path
+
+`world_list.gd` → `POST /join` → `Session.begin(world_id, host, port)` →
+load `game.tscn`. `game.gd` sees `Session.active` and connects a
+`NetworkClient`:
+
+- **Local player** keeps predicting with its own collision-aware
+  `CharacterBody3D` (`player.gd`) — that *is* the prediction. Its input frame
+  (`player.net_input`) is forwarded to the server every physics tick.
+- **Correction backstop:** if the local position drifts from the server's by
+  more than `CORRECTION_THRESHOLD` (1.5 m — generous; catches teleport / a wall
+  walked through / real desync, not prediction noise) it snaps.
+- **Remote players:** rendered from snapshots, position lerped. *Appearance sync
+  is a follow-up* — remotes currently show as labelled capsules; the server
+  does not yet replicate avatar loadouts.
+- **Disconnect** → status message → back to the world list.
+
+The `NetworkClient`'s own flat-plane prediction + input-replay reconciliation
+(§5) is exercised by `smoke_test_network_client.gd`; the collision-aware game
+path above uses the lighter `send_input()` + drift-snap instead.
+
+---
+
 ## 8. Security & Anti-Cheat
 
 - **No client-authoritative gameplay values.** Clients only send *inputs* and

docs/architecture/pc2_test_level.md

@@ -0,0 +1,194 @@
+# PC2 Test Level & Player Spawn — Design Note
+
+> **Status:** Decided (PC2)
+> **Owner:** Architecture
+> **Consumers:** the two PC2 implementation tasks — (1) build the test level,
+> (2) build the player & spawn it. Both must be able to follow this note
+> without further design decisions.
+
+## 1. Decision: static scene, not chunk streaming
+
+**The PC2 playable test level is a single, hand-authored, static Godot 3D
+scene.** It is **not** built through the chunk streaming system
+(`scripts/chunk_stream_manager.gd`, `chunk_scene.gd`, `chunk.gd`,
+`chunk_data_decoder.gd`).
+
+This is a deliberate decision, not a default:
+
+- **The streaming system has never been exercised with real content.** It is a
+  faithful port of the `docs/architecture/world.md` format spec, but nothing in
+  the project produces or serves chunk payloads for it to consume. `scenes/main.tscn`
+  wires `chunk_stream_manager.gd` onto a bare `Node3D` with no `player` reference
+  and no `_server_rpc`, so at runtime it does nothing. There is no server-side
+  chunk authoring/streaming endpoint to integrate against.
+- **PC2 scope is single-player, local-only, no networking.** The value of chunk
+  streaming is server-authoritative streaming around a moving player across a
+  network boundary. None of those preconditions exist in PC2, so exercising the
+  pipeline here would mean building a chunk *authoring + serving* path first —
+  clearly out of checkpoint scope.
+- **A static scene is the lowest-risk way to get "spawn a player in a real 3D
+  level and walk around" working**, which is the actual PC2 outcome being tested.
+
+Chunk streaming is **not removed and not broken by this decision** — it stays as
+an optional, later milestone. The static level is the PC2 proof of the *player*
+and *camera/physics* half of the problem; chunk streaming remains the later proof
+of the *world data* half.
+
+## 2. Where things live
+
+| Artifact | Path | Owned by |
+|---|---|---|
+| Test level scene | `scenes/worlds/test_level.tscn` | level task |
+| Player scene | `scenes/player.tscn` | player task |
+| Player controller script | `scripts/player.gd` | player task |
+| Game composition scene | `scenes/game.tscn` | player task |
+
+- **`scenes/worlds/`** is the convention for all level scenes (it does not exist
+  yet; the level task creates it). Future levels follow `scenes/worlds/<name>.tscn`.
+- `scenes/player.tscn` is **reusable** across levels — it must not hard-code any
+  reference to `test_level`; it discovers the spawn point at runtime (see §3).
+
+## 3. Player spawn convention
+
+The level scene **must** contain a `Marker3D` named exactly **`PlayerSpawn`**.
+That node's world transform is the spawn point.
+
+- `Marker3D` is a plain `Node3D` that shows a cross gizmo in the editor and
+  carries no gameplay behavior — it is the established Godot idiom for "position
+  hint." (Confirmed present in Godot 4.6.2.)
+- The marker's **position** is authoritative; its rotation is ignored by the
+  player (spawn yaw is the player's concern, default forward is fine).
+- Coordinate system: **Y-up, units = meters, 1 unit = 1 m.** The marker must sit
+  at least **1.0 m above the ground's top surface** (recommended `y = 1.0` where
+  the ground top is `y = 0`) so the player capsule does not spawn intersecting
+  the floor and get popped out by the physics solver.
+- There is exactly **one** `PlayerSpawn` per level. (If a level ever needs
+  multiple spawns, that is a later convention — not PC2.)
+
+**Lookup rule (implemented by `player.gd`, not by the level):**
+
+```
+# in player.gd _ready()
+var spawn := get_tree().current_scene.find_child("PlayerSpawn", true, false)
+if spawn is Node3D:
+    global_position = spawn.global_position
+else:
+    push_warning("player.gd: no PlayerSpawn marker found; spawning at origin")
+    global_position = Vector3(0, 1.0, 0)   # fallback, do not crash
+```
+
+The lookup runs from the current scene root so it finds the marker whether it is
+a direct child of the level instance or nested under a `Level` wrapper. The
+fallback keeps the player runnable in a scene that forgot its marker, but a
+**missing `PlayerSpawn` is a level bug** and the level task's smoke test must fail
+on it (see §6).
+
+## 4. Composition (who puts level + player together)
+
+`scenes/game.tscn` is the PC2 playable entry point:
+
+```
+Game (Node3D)
+├── Level      (instance of res://scenes/worlds/test_level.tscn)
+└── Player     (instance of res://scenes/player.tscn)
+```
+
+- `Game` is a plain `Node3D` with **no script** — composition is done by scene
+  instantiation, not code, so there is nothing to keep in sync.
+- The **level scene is self-contained and has zero dependency on the player** —
+  it loads and is smoke-testable on its own. The level task does not instance or
+  reference `player.tscn`.
+- The **player scene is self-contained and has zero dependency on any specific
+  level** — it only requires that the *current scene* contains a `PlayerSpawn`.
+- Ownership of `game.tscn` goes to the **player task**, which depends on the
+  level task having landed `test_level.tscn` first (chain with `depends_on`).
+
+## 5. Level content requirements (level task)
+
+`scenes/worlds/test_level.tscn`, root node `TestLevel` (`Node3D`). Required
+children:
+
+| Node | Type | Notes |
+|---|---|---|
+| `Ground` | `StaticBody3D` | `BoxShape3D` (e.g. `40 × 1 × 40`) centered at `(0, -0.5, 0)` so the **top face is `y = 0`**; matching `MeshInstance3D` (`BoxMesh`) so it is visible and collidable. Use a `StaticBody3D` rather than a bare `PlaneMesh` so collision is explicit and reliable. |
+| `Props` | `Node3D` | 3–5 simple props as `StaticBody3D` + `MeshInstance3D` using built-in primitives only (`BoxMesh`, `CylinderMesh`, `SphereMesh`). `assets/` is empty and PC2 must not require imported content. Positioned on the ground surface; scale freely. |
+| `Sun` | `DirectionalLight3D` | Pitch it downward (~ -45°), enable shadows if the compatibility renderer allows; shadows are optional. |
+| `WorldEnvironment` | `WorldEnvironment` | Ambient light and/or a simple background color. Keep it plain — the project uses `gl_compatibility`. |
+| `PlayerSpawn` | `Marker3D` | Per §3. Recommended `(0, 1.0, 0)`. |
+
+Notes:
+
+- **Do not** add any `script` to the level. It is pure content. Any per-level
+  behavior belongs to the player (or a future game-mode script), not the level.
+- Keep the whole level on the XZ plane around the origin; nothing off at extreme
+  coordinates, no thin walls the capsule can tunnel through.
+
+## 6. Player contract (player task)
+
+`scenes/player.tscn`, root `Player` (`CharacterBody3D`) + `scripts/player.gd`.
+
+Minimum for PC2:
+
+- **Body:** `CharacterBody3D` with a `CollisionShape3D` using `CapsuleShape3D`
+  (~`radius 0.3`, ~`height 1.8`) and a matching `CapsuleMesh` for visibility.
+- **Camera:** a `Camera3D` child. First-person (camera at capsule head height) is
+  the lowest-risk choice; third-person is fine too but is more work.
+- **Spawn:** per §3 — read `PlayerSpawn` from the current scene, fall back
+  gracefully.
+- **Movement:** gravity + `move_and_slide()` so the player stands on `Ground`.
+  WASD/arrow locomotion is the hard requirement. Mouse-look is recommended but
+  may be split into its own task if the controller grows.
+- **No networking, no avatar UI, no chunk code** — PC2 is local-only. Do not add
+  `MultiplayerAPI`, `ChunkStreamManager`, or any avatar customization here.
+
+The player must work when instanced under `Game` alongside a level; it must not
+assume it is the only node in the scene.
+
+## 7. Entry point / how a human plays it
+
+- `scenes/game.tscn` is the PC2 playable scene. For playtesting, load it directly
+  (e.g. `godot --path . scenes/game.tscn`), or temporarily set
+  `application/run/main_scene` to it.
+- **Wiring "Play → Join a world" in the existing `world_list` UI is out of scope
+  for this note** and out of scope for the level/player tasks. The current menu
+  flow ends at browse-worlds (PC1). If a checkpoint wants a clickable path into
+  the test level, that navigation wiring is its own small task — do not fold it
+  into level or player.
+
+## 8. Validation (both tasks must run this before "done")
+
+```sh
+# one-time, first checkout only — builds the class/import cache
+godot --headless --path . --import
+
+# then, to catch parse/load errors:
+godot --headless --path . --quit
+```
+
+- **Level task:** additionally load `test_level.tscn` headlessly and assert it
+  (a) loads without error and (b) contains a `Marker3D` named `PlayerSpawn`
+  positioned ≥ 1.0 m above the ground top. A smoke script following the existing
+  `scripts/smoke_test_*.gd` pattern is the right vehicle.
+- **Player task:** a smoke test that instantiates `game.tscn`, waits a frame,
+  and asserts the player's global position equals the `PlayerSpawn` position
+  (within a small epsilon). This is the check that proves the spawn convention
+  actually wired through — not just "the scene loads."
+
+## 9. Explicitly out of scope for PC2
+
+- Networking / multiplayer / prediction (single-player, local-only).
+- Chunk streaming integration and server-side chunk authoring/serving.
+- Avatar customization UI and glTF avatar loading.
+- Join-a-world navigation from the world list.
+- Any content moderation / age-gating logic in the level.
+
+## 10. Summary
+
+| Concern | Decision |
+|---|---|
+| Level construction | Static hand-authored Godot 3D scene (chunk streaming deferred, not removed) |
+| Level location | `scenes/worlds/test_level.tscn` |
+| Spawn convention | `Marker3D` named `PlayerSpawn`, ≥ 1.0 m above ground, looked up by the player |
+| Player | `scenes/player.tscn` (`CharacterBody3D`) + `scripts/player.gd`, reusable across levels |
+| Composition | `scenes/game.tscn` instances `Level` + `Player`; no script |
+| Entry point | Load `scenes/game.tscn` directly; UI join-wiring deferred |

docs/architecture/scripting_sandbox.md

@@ -0,0 +1,159 @@
+# GDScript Sandboxing for User-Written Scripts
+
+> **Status:** Proposed
+> **Owner:** Platform team
+> **Related:** Content moderation & age verification (scripts are one of the
+> three moderated content types), avatar component system
+
+## 1. Overview
+
+This document evaluates how to safely run **user-written scripts** as part of
+UGC (user-generated content) in **agp-game**, and recommends an approach.
+
+**Bottom line: Godot 4 has no built-in security sandbox for GDScript, and
+none of the three options named in the original task hold up under testing.**
+A script running anywhere inside the Godot process — however it's loaded,
+parented, or wrapped — runs with full engine privileges: arbitrary process
+execution, full filesystem read/write, and raw network access. Sandboxing
+has to happen *outside* the scripting language, not through an in-engine
+restriction mechanism, because no such mechanism exists.
+
+This was verified directly against Godot 4.6.2 (`godot --headless`, evidence
+in `sandbox_probe/` on this branch) rather than assumed from documentation,
+some of which (see §2.1) describes APIs that don't actually exist in this
+version.
+
+## 2. Options Evaluated
+
+### 2.1 Godot's built-in "ScriptServer" restrictions — does not exist
+
+There is no `ScriptServer` class in Godot 4.6.2:
+
+```
+ClassDB.class_exists("ScriptServer")  →  false
+```
+
+There's also no project setting to disable engine subsystems for scripts —
+none of `application/run/disable_os`, `disable_file_access`, or
+`disable_network` exist as settings, and `ProjectSettings.get_property_list()`
+returns nothing matching "sandbox", "restrict", or "security". Any plan that
+assumes a flag like this exists needs to be dropped; it was likely conflated
+with sandboxing features from a different engine/scripting ecosystem, or
+with **export template stripping** (which controls what ships in a build,
+not what a script can call at runtime).
+
+Directly probed capabilities of an ordinary GDScript running as a normal
+node script, no special setup:
+
+| Capability | Available to any script? |
+|---|---|
+| `OS.execute(...)` — run arbitrary processes | ✅ Yes |
+| `FileAccess.open(...)` — read/write any path the OS user can reach | ✅ Yes (read `/etc/hostname`, write `/tmp/...` both succeeded) |
+| `TCPServer` / `HTTPClient` / `HTTPRequest` / `PacketPeerUDP` / `WebSocketPeer` | ✅ All instantiate and work |
+| `ClassDB.instantiate(...)` — construct any engine class by name | ✅ Yes |
+| Loading and running a second script from source text at runtime (`GDScript.new()` + `.reload()`) | ✅ Yes |
+
+**Verdict: rejected.** There is nothing to configure here — the restriction
+surface this option assumed doesn't exist in the engine.
+
+### 2.2 Isolated SubViewport with a limited API — doesn't isolate scripts
+
+`SubViewport` is a **rendering and input isolation** primitive (it gives a
+scene subtree its own render target and can gate input propagation) — it is
+not a security or scripting boundary. A script attached to any node inside a
+`SubViewport` still runs in the same process, on the same GDScript VM, with
+the exact same access to `OS`, `FileAccess`, networking classes, and
+`ClassDB` as a script anywhere else in the tree. Nothing about being
+"inside" a SubViewport changes what API calls are reachable from a script.
+
+**Verdict: rejected.** This solves a rendering/UI-composition problem, not
+the security problem the task is asking about. Worth keeping in mind for
+other purposes (e.g. isolated preview rendering of user avatars), but it
+provides zero script sandboxing.
+
+### 2.3 Custom GDScript interpreter with an allowlist — right idea, wrong layer for "custom interpreter"
+
+Two ways to read this option, tested separately:
+
+**(a) Write/embed a separate GDScript parser+interpreter.** Not
+practical — this means re-implementing (and then indefinitely maintaining,
+in lockstep with every Godot release) a full language interpreter outside
+the engine. Far more engineering than the problem justifies.
+
+**(b) Use Godot's built-in `Expression` class as a restricted subset.**
+`Expression` *looks* like a natural allowlist mechanism — it only evaluates
+a single expression, no control flow, no arbitrary statements. But it isn't
+safe by default: it can still reach through to unsafe engine methods if you
+aren't careful about what object you hand it as a base instance:
+
+```gdscript
+var expr = Expression.new()
+expr.parse("get_environment('HOME')", ["OS"])
+expr.execute([], OS)   # → "/home/daddy"  (successfully called OS.get_environment)
+```
+
+So `Expression` is a viable building block only if the host **never passes
+a base instance (or arguments) that exposes anything sensitive** — i.e. the
+allowlisting work still has to happen at the call site, `Expression` itself
+enforces none of it.
+
+**Static text pattern-matching (blocklisting dangerous substrings like
+`"OS.execute"` before parsing) was also probed and is not a real
+defense** — it's trivially defeated by string concatenation, `call()`,
+`Callable`, or any other indirection, and produces false confidence.
+
+**Verdict: partially viable, but only as a foundation, not a solution on
+its own.** A hand-built, narrow, data-driven DSL (not full GDScript, not
+raw `Expression`) with an explicit allowlist of safe operations and *no
+ability to reference engine singletons or arbitrary objects* is the only
+version of "custom interpreter" that's actually safe. This is real
+engineering effort, not a config flag.
+
+## 3. Recommendation
+
+**Don't run untrusted GDScript in-process at all.** Given none of the three
+in-engine options provide a real boundary, the two approaches actually worth
+building are, in order of recommended priority:
+
+1. **Primary: a narrow, non-Turing-complete content DSL**, not general
+   scripting. Most UGC scripting needs in a game like this (custom
+   interactions, simple triggers, item behaviors) don't need a general
+   programming language — they need a small set of declarative
+   verbs/conditions (e.g. `on_interact: give_item("torch")`,
+   `on_enter: play_sound("chime")`). Expressed as data (JSON/Resource, not
+   code) and interpreted by trusted, hand-written GDScript on the engine
+   side. This has *zero* attack surface by construction — there's no
+   interpreter to escape because there's no general execution, just a
+   fixed, reviewed set of verbs. This is almost certainly sufficient for
+   the actual UGC use cases in this game and should be scoped against real
+   feature requirements before assuming more is needed.
+
+2. **If genuinely general scripting becomes a hard requirement**, isolate it
+   at the OS level, not the engine level: run untrusted scripts in a
+   **separate process** (a stripped-down Godot instance or a dedicated
+   interpreter) under OS sandboxing (a restricted user account, a
+   container, or `firejail`/`bwrap`/seccomp), communicating with the main
+   game over a narrow IPC/RPC boundary that only exposes intentionally-safe
+   operations. This is the only approach that provides a real security
+   boundary for arbitrary code, because it doesn't depend on the scripting
+   language cooperating — the OS enforces it. Substantially more
+   infrastructure than option 1; only worth it if option 1's DSL genuinely
+   can't express what's needed.
+
+**Do not** attempt in-process GDScript sandboxing via SubViewport,
+ScriptServer, or ad hoc blocklisting — all three were directly tested and
+none provide a real boundary (§2).
+
+## 4. Open Questions
+
+- What do actual planned UGC scripts need to *do*? (Trigger conditions,
+  simple item/state effects, dialogue branching?) This determines whether
+  the DSL in §3.1 is sufficient or whether §3.2's process isolation is
+  needed. Needs a concrete feature list before implementation starts.
+- If §3.2 is needed later, does it run per-user-session or shared/pooled?
+  Affects resource cost and isolation guarantees.
+- Interaction with the content moderation pipeline (`content_moderation.md`):
+  scripts as a moderated content type still need a moderation flag path
+  regardless of which execution model is chosen — a DSL makes static
+  analysis of *what a script can possibly do* far easier than it would be
+  for general code, which is an additional point in its favor.

docs/architecture/world.md

@@ -0,0 +1,737 @@
+# World Chunk Data Format & Persistence Architecture
+
+> **Status:** Proposed
+> **Owner:** Platform team
+> **Related:** Server authority + client prediction, avatar component system, content moderation & age verification, backend auth (JWT)
+
+## 1. Overview
+
+This document specifies the **world chunk data format** and **persistence
+schema** for **agp-game**, a Godot-based multiplayer game built by autonomous
+agents. It defines:
+
+- The **chunk data format** — both a human-readable **JSON** form (for
+  authoring, tooling, and debugging) and a compact **binary** form (for
+  runtime loading and network transfer).
+- The **SQLite schema** that persists world state on the server, including
+  chunk metadata, chunk payloads, and the world/room hierarchy.
+- The **read/write API** that the server and client use to load, save, and
+  stream chunks.
+
+The goal is a **single, versioned chunk contract** that is shared across the
+Godot client, the Python backend, and the persistence layer. A chunk is the
+atomic unit of world geometry, gameplay objects, and persistence — the server
+loads and saves whole chunks, and clients stream the chunks around them.
+
+### 1.1 Design Goals
+
+- **Versioned & forward-compatible:** Every chunk carries a format version so
+  the loader can migrate old data and reject unknown future data gracefully.
+- **Dual representation:** JSON for authoring/debugging, binary for
+  runtime/network. Both encode the *same* logical model so there is exactly one
+  source of truth for the schema.
+- **Server-authoritative persistence:** The server is the only writer to the
+  SQLite store. Clients submit *edits* (deltas) and the server applies and
+  persists them, mirroring the server-authoritative networking model.
+- **Chunk-granular persistence:** Persistence happens at chunk granularity so
+  the server can save a dirty chunk without rewriting the whole world, and can
+  stream only the chunks a client needs.
+- **Deterministic & testable:** The binary format is byte-stable for a given
+  logical payload, enabling checksums, caching, and reproducible tests.
+- **Moderation-aware:** Chunks reference content (assets, scripts) that carry
+  content flags (see `content_moderation.md`); the persistence layer stores the
+  moderation state alongside chunk data so enforcement can happen at load time.
+
+---
+
+## 2. World Model & Chunking
+
+### 2.1 World Hierarchy
+
+The world is organized as a hierarchy that matches the moderation content graph:
+
+```
+World
+ └── Room
+      └── Chunk   (the atomic persistence & streaming unit)
+           ├── Tiles / Terrain
+           ├── Static objects (props, geometry)
+           ├── Dynamic objects (spawnable entities, interactables)
+           └── Metadata (flags, version, timestamps)
+```
+
+- A **World** is the top-level container (a named, versioned space).
+- A **Room** is a bounded region within a world (a level, a building, a zone).
+- A **Chunk** is a fixed-size, axis-aligned region of a room. It is the unit of
+  load, save, and stream.
+
+### 2.2 Chunk Dimensions
+
+Chunks are **fixed-size, axis-aligned boxes** in world space. The default
+dimensions are a configuration constant so they can be tuned per world:
+
+| Constant            | Default | Description                                        |
+|---------------------|---------|----------------------------------------------------|
+| `CHUNK_SIZE_X`      | 32      | Chunk width in world units (tiles).                |
+| `CHUNK_SIZE_Y`      | 32      | Chunk height in world units (tiles).               |
+| `CHUNK_SIZE_Z`      | 1       | Chunk depth (1 = flat 2D world; >1 = volumetric).  |
+| `CHUNK_ORIGIN`      | `(0,0)` | World-space origin of chunk coordinate `(0,0)`.    |
+
+A chunk is identified by its **integer chunk coordinate** `(cx, cy, cz)`,
+computed from a world-space position `p` as:
+
+```
+cx = floor((p.x - CHUNK_ORIGIN.x) / CHUNK_SIZE_X)
+cy = floor((p.y - CHUNK_ORIGIN.y) / CHUNK_SIZE_Y)
+cz = floor((p.z - CHUNK_ORIGIN.z) / CHUNK_SIZE_Z)
+```
+
+The chunk's world-space bounding box is therefore:
+
+```
+min = (CHUNK_ORIGIN.x + cx*CHUNK_SIZE_X, ...)
+max = min + (CHUNK_SIZE_X, CHUNK_SIZE_Y, CHUNK_SIZE_Z)
+```
+
+### 2.3 Chunk Coordinate Key
+
+For storage and lookup, a chunk is addressed by a **canonical string key**:
+
+```
+"{world_id}:{room_id}:{cx}:{cy}:{cz}"
+```
+
+Example: `"w_0001:r_0001:12:-4:0"`. This key is the primary lookup key in the
+SQLite `chunks` table and is used in the read/write API.
+
+---
+
+## 3. Chunk Data Format
+
+### 3.1 Logical Model
+
+Both the JSON and binary encodings serialize the same logical chunk model. The
+logical model is defined here once; the two encodings are projections of it.
+
+```
+Chunk
+ ├── version        : uint   (format version, currently 1)
+ ├── key            : string (canonical chunk key, see §2.3)
+ ├── world_id       : string
+ ├── room_id        : string
+ ├── coord          : { cx, cy, cz }   (int)
+ ├── bounds         : { min_x, min_y, min_z, max_x, max_y, max_z } (float)
+ ├── tiles          : TileLayer[]       (terrain / tile data)
+ ├── objects        : WorldObject[]     (static + dynamic objects)
+ ├── flags          : ContentFlags      (moderation flags, see §3.5)
+ ├── meta           : { created_at, updated_at, revision, author } 
+ └── checksum       : string            (SHA-256 of canonical payload)
+```
+
+### 3.2 Tile Layer
+
+A chunk's terrain is stored as one or more **tile layers**. Each layer is a
+dense grid of tile IDs of size `CHUNK_SIZE_X × CHUNK_SIZE_Y` (× `CHUNK_SIZE_Z`
+for volumetric worlds).
+
+```
+TileLayer
+ ├── name      : string   (e.g. "ground", "walls", "decor")
+ ├── layer_id  : uint
+ ├── width     : uint     (= CHUNK_SIZE_X)
+ ├── height    : uint     (= CHUNK_SIZE_Y)
+ ├── depth     : uint     (= CHUNK_SIZE_Z)
+ ├── tiles     : uint[]   (flattened tile IDs, row-major, length = w*h*d)
+ └── palette   : TileDef[] (tile ID → tile definition, shared per layer)
+```
+
+**Tile encoding:** A tile ID is a `uint16` index into the layer's `palette`.
+`0` is reserved for "empty/air". The palette maps each tile ID to a `TileDef`:
+
+```
+TileDef
+ ├── id       : uint16
+ ├── asset_id : string   (reference to a tile/terrain asset)
+ ├── solid    : bool     (collision)
+ ├── flags    : uint32   (bitmask: walkable, climbable, liquid, ...)
+ └── variants : uint8    (number of visual variants for this tile)
+```
+
+**Rationale for palette + indices:** Storing dense `uint16` indices rather than
+full asset strings per cell keeps the binary payload small (2 bytes/cell) while
+the palette (shared across the layer) carries the rich per-tile metadata.
+
+### 3.3 World Objects
+
+Objects are the non-tile entities in a chunk: static props, interactables,
+spawn points, and dynamic-object templates.
+
+```
+WorldObject
+ ├── id          : string   (stable object id, unique within the chunk)
+ ├── type        : string   (e.g. "prop", "interactable", "spawn_point", "door")
+ ├── asset_id    : string   (reference to the object's mesh/glTF asset)
+ ├── transform   : { pos: [x,y,z], rot: [x,y,z,w], scale: [x,y,z] }
+ ├── properties  : object   (type-specific key/value map, JSON-typed)
+ ├── dynamic     : bool     (true if this is a spawnable dynamic entity)
+ └── flags       : ContentFlags (per-object moderation flags)
+```
+
+**Dynamic objects** are stored as *templates* in the chunk. Their *runtime
+state* (position, health, inventory) is **not** stored in the chunk; it lives
+in the runtime entity store and is persisted separately (see §4.4). This keeps
+chunks stable and diffable — a chunk only changes when its *static* content
+changes.
+
+### 3.4 Content Flags
+
+Each chunk (and each object) carries a **content flag set** that is the
+aggregate of the moderation flags of the assets and scripts it references. This
+mirrors the aggregation rules in `content_moderation.md`:
+
+```
+ContentFlags
+ ├── categories : { violence, sexual, language, substance, gambling, horror, hate, custom }
+ │                (each → severity: none|mild|moderate|severe)
+ ├── mature     : bool   (true if any contributing item is mature)
+ └── sources    : string[] (flag ids that contributed, for audit)
+```
+
+The server computes and persists these flags at write time so that enforcement
+(age gating, content filtering) can happen at load time without re-scanning
+assets.
+
+### 3.5 JSON Encoding
+
+The JSON encoding is the **authoring and debugging** representation. It is
+human-readable, diffable, and used by tools and tests. It is the canonical
+logical model serialized directly.
+
+```json
+{
+  "version": 1,
+  "key": "w_0001:r_0001:12:-4:0",
+  "world_id": "w_0001",
+  "room_id": "r_0001",
+  "coord": { "cx": 12, "cy": -4, "cz": 0 },
+  "bounds": { "min_x": 384.0, "min_y": -128.0, "min_z": 0.0,
+              "max_x": 416.0, "max_y": -96.0,  "max_z": 1.0 },
+  "tiles": [
+    {
+      "name": "ground",
+      "layer_id": 0,
+      "width": 32,
+      "height": 32,
+      "depth": 1,
+      "palette": [
+        { "id": 0, "asset_id": "", "solid": false, "flags": 0, "variants": 1 },
+        { "id": 1, "asset_id": "tiles/grass", "solid": false, "flags": 1, "variants": 4 }
+      ],
+      "tiles": [0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1]
+    }
+  ],
+  "objects": [
+    {
+      "id": "obj_0001",
+      "type": "interactable",
+      "asset_id": "props/chest",
+      "transform": { "pos": [400.0, -110.0, 0.0],
+                     "rot": [0.0, 0.0, 0.0, 1.0],
+                     "scale": [1.0, 1.0, 1.0] },
+      "properties": { "loot_table": "chest_basic", "locked": false },
+      "dynamic": false,
+      "flags": { "categories": { "violence": "none" }, "mature": false, "sources": [] }
+    }
+  ],
+  "flags": { "categories": { "violence": "none" }, "mature": false, "sources": [] },
+  "meta": { "created_at": "2026-08-17T00:00:00Z",
+            "updated_at": "2026-08-17T00:00:00Z",
+            "revision": 3,
+            "author": "agent-bot" },
+  "checksum": "9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08"
+}
+```
+
+> **Note on the example checksum:** The value shown above is illustrative only.
+> In practice the `checksum` field is the SHA-256 of the canonical binary
+> payload body (see §3.6.3), not of the JSON text. The value here is a
+> placeholder for documentation purposes.
+
+### 3.6 Binary Encoding
+
+The binary encoding is the **runtime and network** representation. It is compact
+and byte-stable. It uses a simple, explicitly-specified layout (no external
+serialization library) so it can be produced and consumed identically by the
+Godot client (GDScript) and the Python backend.
+
+#### 3.6.1 Header
+
+| Offset | Size | Field        | Type / Encoding                          |
+|--------|------|--------------|------------------------------------------|
+| 0      | 4    | magic        | ASCII `"AGPC"` (0x41 0x47 0x50 0x43)     |
+| 4      | 2    | version      | `uint16` LE (currently `1`)              |
+| 6      | 2    | header_len   | `uint16` LE (bytes of header after this) |
+| 8      | 4    | flags        | `uint32` LE (bitmask, reserved)          |
+| 12     | 4    | payload_len  | `uint32` LE (bytes of payload body)      |
+| 16     | 32   | checksum     | SHA-256 of payload body (hex, 32 bytes)  |
+
+Total header size: **48 bytes**.
+
+#### 3.6.2 Payload Body
+
+The payload body is a sequence of typed sections. Each section has a small
+header:
+
+| Offset | Size | Field      | Type / Encoding            |
+|--------|------|------------|----------------------------|
+| 0      | 1    | section_id | `uint8` (see table below)  |
+| 1      | 4    | section_len| `uint32` LE (bytes of section data) |
+| 5      | ...  | data       | section-specific           |
+
+Section IDs:
+
+| section_id | Section        | Data layout                                                       |
+|------------|----------------|-------------------------------------------------------------------|
+| `0x01`     | metadata       | world_id, room_id (length-prefixed strings), coord (3×int32), bounds (6×float32) |
+| `0x02`     | tile layer     | name, layer_id, dims (3×uint16), palette, dense tile indices      |
+| `0x03`     | object         | one `WorldObject` (repeated; one section per object)              |
+| `0x04`     | content flags  | category severities (8×uint8), mature (uint8), sources (string list) |
+| `0x05`     | meta           | created_at, updated_at (int64 unix), revision (uint32), author (string) |
+
+**String encoding:** length-prefixed UTF-8 — `uint16` LE byte length followed by
+the UTF-8 bytes.
+
+**Tile layer data layout (section `0x02`):**
+
+```
+name        : string
+layer_id    : uint16 LE
+width       : uint16 LE
+height      : uint16 LE
+depth       : uint16 LE
+palette_count : uint16 LE
+palette     : palette_count × TileDef
+tile_count  : uint32 LE
+tiles       : tile_count × uint16 LE   (dense, row-major)
+```
+
+```
+TileDef:
+  id        : uint16 LE
+  asset_id  : string
+  solid     : uint8
+  flags     : uint32 LE
+  variants  : uint8
+```
+
+**Object data layout (section `0x03`):**
+
+```
+id          : string
+type        : string
+asset_id    : string
+pos         : 3 × float32
+rot         : 4 × float32
+scale       : 3 × float32
+dynamic     : uint8
+properties  : JSON string (length-prefixed)
+flags       : ContentFlags (see 0x04 layout)
+```
+
+**Content flags layout (section `0x04`):**
+
+```
+violence, sexual, language, substance, gambling, horror, hate, custom
+            : 8 × uint8   (severity enum: 0=none,1=mild,2=moderate,3=severe)
+mature      : uint8
+source_count: uint16 LE
+sources     : source_count × string
+```
+
+#### 3.6.3 Byte-Stability
+
+For a given logical payload, the binary encoding is **deterministic**:
+
+- All integers are little-endian.
+- All strings are UTF-8, length-prefixed, and never null-terminated.
+- Maps (e.g. `properties`) are serialized as a **canonical JSON string** with
+  keys sorted lexicographically.
+- The `checksum` is the SHA-256 of the payload body bytes.
+
+This guarantees that two encoders produce identical bytes, enabling content
+addressing, caching, and reproducible tests.
+
+---
+
+## 4. SQLite Persistence Schema
+
+The server persists world state in a **SQLite** database. SQLite is chosen for
+its zero-configuration, single-file, transactional, and embedded nature — ideal
+for a server that owns the world store and needs ACID guarantees without a
+separate database process.
+
+### 4.1 Database Layout
+
+The database file is `world.db` (path configurable). It contains the following
+tables:
+
+```
+worlds
+rooms
+chunks
+chunk_objects
+content_flags
+revisions
+```
+
+### 4.2 `worlds`
+
+Top-level world containers.
+
+```sql
+CREATE TABLE worlds (
+    id          TEXT PRIMARY KEY,          -- e.g. 'w_0001'
+    name        TEXT NOT NULL,
+    description TEXT,
+    chunk_size_x INTEGER NOT NULL DEFAULT 32,
+    chunk_size_y INTEGER NOT NULL DEFAULT 32,
+    chunk_size_z INTEGER NOT NULL DEFAULT 1,
+    origin_x    REAL NOT NULL DEFAULT 0,
+    origin_y    REAL NOT NULL DEFAULT 0,
+    origin_z    REAL NOT NULL DEFAULT 0,
+    created_at  TEXT NOT NULL,             -- ISO-8601 UTC
+    updated_at  TEXT NOT NULL
+);
+```
+
+### 4.3 `rooms`
+
+Rooms within a world.
+
+```sql
+CREATE TABLE rooms (
+    id          TEXT PRIMARY KEY,          -- e.g. 'r_0001'
+    world_id    TEXT NOT NULL REFERENCES worlds(id) ON DELETE CASCADE,
+    name        TEXT NOT NULL,
+    bounds_min_x REAL NOT NULL,
+    bounds_min_y REAL NOT NULL,
+    bounds_min_z REAL NOT NULL DEFAULT 0,
+    bounds_max_x REAL NOT NULL,
+    bounds_max_y REAL NOT NULL,
+    bounds_max_z REAL NOT NULL DEFAULT 1,
+    created_at  TEXT NOT NULL,
+    updated_at  TEXT NOT NULL,
+    UNIQUE (world_id, name)
+);
+CREATE INDEX idx_rooms_world ON rooms(world_id);
+```
+
+### 4.4 `chunks`
+
+The core persistence table. One row per chunk. The **payload** is stored as a
+BLOB in the **binary format** (§3.6); the JSON form is derived on demand for
+authoring/debugging and is not stored (to avoid dual-write drift).
+
+```sql
+CREATE TABLE chunks (
+    key         TEXT PRIMARY KEY,          -- canonical key 'world:room:cx:cy:cz'
+    world_id    TEXT NOT NULL REFERENCES worlds(id) ON DELETE CASCADE,
+    room_id     TEXT NOT NULL REFERENCES rooms(id) ON DELETE CASCADE,
+    cx          INTEGER NOT NULL,
+    cy          INTEGER NOT NULL,
+    cz          INTEGER NOT NULL DEFAULT 0,
+    format_version INTEGER NOT NULL DEFAULT 1,
+    payload     BLOB NOT NULL,             -- binary chunk encoding (§3.6)
+    payload_len INTEGER NOT NULL,
+    checksum    TEXT NOT NULL,             -- SHA-256 of payload
+    revision    INTEGER NOT NULL DEFAULT 0,
+    dirty       INTEGER NOT NULL DEFAULT 0, -- 1 = needs flush to disk
+    created_at  TEXT NOT NULL,
+    updated_at  TEXT NOT NULL,
+    UNIQUE (world_id, room_id, cx, cy, cz)
+);
+CREATE INDEX idx_chunks_world_room ON chunks(world_id, room_id);
+CREATE INDEX idx_chunks_coord ON chunks(cx, cy, cz);
+```
+
+**Design notes:**
+
+- The `payload` BLOB is the single source of truth for chunk content. The
+  `checksum` guards against corruption and enables content addressing.
+- `revision` increments on every write; it is used for optimistic concurrency
+  and change detection (see §5.4).
+- `dirty` marks chunks that have been modified in memory but not yet flushed,
+  enabling a write-behind persistence strategy (see §5.5).
+
+### 4.5 `chunk_objects`
+
+A denormalized, queryable index of the objects inside each chunk. This is
+**derived** from the chunk payload and kept in sync by the write path. It exists
+so the server can answer queries like "which chunks contain a door?" without
+parsing every payload BLOB.
+
+```sql
+CREATE TABLE chunk_objects (
+    id          TEXT NOT NULL,             -- object id (unique within chunk)
+    chunk_key   TEXT NOT NULL REFERENCES chunks(key) ON DELETE CASCADE,
+    type        TEXT NOT NULL,             -- 'prop', 'interactable', ...
+    asset_id    TEXT,
+    dynamic     INTEGER NOT NULL DEFAULT 0,
+    pos_x       REAL NOT NULL,
+    pos_y       REAL NOT NULL,
+    pos_z       REAL NOT NULL DEFAULT 0,
+    PRIMARY KEY (chunk_key, id)
+);
+CREATE INDEX idx_chunk_objects_type ON chunk_objects(type);
+CREATE INDEX idx_chunk_objects_asset ON chunk_objects(asset_id);
+```
+
+**Sync mechanism:** `chunk_objects` is maintained **explicitly by the write
+path** — it is not a SQL trigger. Whenever `put_chunk` (or `delete_chunk`)
+commits a chunk, the service layer performs a **delete-and-reinsert** of that
+chunk's object rows in the same transaction: it deletes all rows for
+`chunk_key`, then inserts fresh rows parsed from the new payload. This keeps the
+index transactionally consistent with the payload and avoids the complexity and
+fragility of SQL triggers over a binary BLOB. Because the index is derived, it
+can always be rebuilt from `chunks.payload` if it ever drifts (a `rebuild_index`
+utility is provided for this).
+
+### 4.6 `content_flags`
+
+Persists the aggregated moderation flags per chunk (and optionally per object).
+This lets the server enforce age/content gates at load time without parsing
+payloads.
+
+```sql
+CREATE TABLE content_flags (
+    chunk_key   TEXT NOT NULL REFERENCES chunks(key) ON DELETE CASCADE,
+    object_id   TEXT NOT NULL DEFAULT '',  -- '' = chunk-level flag (sentinel)
+    violence    INTEGER NOT NULL DEFAULT 0,
+    sexual      INTEGER NOT NULL DEFAULT 0,
+    language    INTEGER NOT NULL DEFAULT 0,
+    substance   INTEGER NOT NULL DEFAULT 0,
+    gambling    INTEGER NOT NULL DEFAULT 0,
+    horror      INTEGER NOT NULL DEFAULT 0,
+    hate        INTEGER NOT NULL DEFAULT 0,
+    custom      INTEGER NOT NULL DEFAULT 0,
+    mature      INTEGER NOT NULL DEFAULT 0,
+    sources     TEXT NOT NULL DEFAULT '[]', -- JSON array of flag ids
+    PRIMARY KEY (chunk_key, object_id)
+);
+CREATE INDEX idx_content_flags_mature ON content_flags(mature);
+```
+
+Severity is stored as `0=none, 1=mild, 2=moderate, 3=severe`.
+
+**Chunk-level vs. object-level flags:** Chunk-level flags use the **sentinel
+value `''` (empty string)** in `object_id` rather than `NULL`. This is
+deliberate: in SQLite, `NULL` values in a composite primary key are **not**
+unique-constrained, so two rows with the same `chunk_key` and `object_id = NULL`
+could be inserted accidentally. Using `''` as the sentinel means the composite
+`PRIMARY KEY (chunk_key, object_id)` enforces that there is **exactly one**
+chunk-level flag row per chunk. Object-level flags use the object's actual `id`
+(which is never empty). The application layer treats `object_id = ''` as
+"chunk-level" and any non-empty value as "object-level".
+
+### 4.7 `revisions`
+
+An append-only audit log of chunk writes. Enables rollback, auditing, and
+replication of changes.
+
+```sql
+CREATE TABLE revisions (
+    id          INTEGER PRIMARY KEY AUTOINCREMENT,
+    chunk_key   TEXT NOT NULL,             -- NOT a FK: survives chunk deletion
+    revision    INTEGER NOT NULL,
+    actor       TEXT NOT NULL,             -- user / agent id
+    action      TEXT NOT NULL,             -- 'create' | 'update' | 'delete'
+    checksum    TEXT NOT NULL,             -- SHA-256 of payload
+    payload     BLOB,                      -- full binary payload at this revision
+    created_at  TEXT NOT NULL
+);
+CREATE INDEX idx_revisions_chunk ON revisions(chunk_key);
+```
+
+**Rollback support:** The `payload` BLOB stores the **full binary chunk payload**
+at each revision. This is what makes rollback possible: to restore a chunk to a
+previous revision, the server reads the `payload` of the target revision and
+writes it back to `chunks.payload` (incrementing `revision` and appending a new
+`revisions` row). Without the payload, only the checksum would be available,
+which is insufficient to reconstruct the chunk.
+
+**Audit trail preservation:** `chunk_key` is **not** a foreign key to `chunks`.
+This means deleting a chunk does **not** cascade-delete its revision history —
+the audit trail is preserved even after a chunk is removed. (The `chunk_key`
+string is still stored so the history can be correlated to a chunk that existed
+at that time.) If a chunk is later recreated with the same key, its history is
+still intact.
+
+### 4.8 Schema Versioning & Migrations
+
+The database carries a schema version in a `meta` table:
+
+```sql
+CREATE TABLE meta (
+    key   TEXT PRIMARY KEY,
+    value TEXT NOT NULL
+);
+-- seed: INSERT INTO meta(key, value) VALUES ('schema_version', '1');
+```
+
+Migrations are applied in order at startup. Each migration is a numbered SQL
+script; the server tracks the applied version in `meta` and applies any pending
+migrations transactionally. This keeps the schema forward-compatible as the
+chunk format evolves.
+
+---
+
+## 5. Read/Write API
+
+The API is exposed as a **Python service layer** on the backend (the same
+process that owns the SQLite store) and consumed by the Godot client over the
+network transport (see `networking.md`). The service layer is the **only**
+writer to the database; clients never touch SQLite directly.
+
+### 5.1 Service Interface (Python)
+
+```python
+class WorldStore:
+    """Owns the SQLite connection and chunk read/write operations."""
+
+    def get_chunk(self, key: str) -> Chunk | None: ...
+    def get_chunk_binary(self, key: str) -> bytes | None: ...
+    def put_chunk(self, chunk: Chunk, actor: str) -> Chunk: ...
+    def delete_chunk(self, key: str, actor: str) -> None: ...
+    def list_chunks(self, world_id: str, room_id: str | None = None,
+                    bounds: Bounds | None = None) -> list[str]: ...
+    def get_chunk_flags(self, key: str) -> ContentFlags: ...
+    def flush_dirty(self) -> int: ...
+    def rollback_chunk(self, key: str, revision: int, actor: str) -> Chunk: ...
+    def rebuild_index(self, chunk_key: str | None = None) -> int: ...
+    def migrate(self) -> None: ...
+```
+
+### 5.2 Encoding Helpers
+
+The service layer provides symmetric encode/decode functions shared by the
+client and server:
+
+```python
+def encode_binary(chunk: Chunk) -> bytes: ...
+def decode_binary(data: bytes) -> Chunk: ...
+def encode_json(chunk: Chunk) -> str: ...
+def decode_json(text: str) -> Chunk: ...
+def checksum(payload: bytes) -> str: ...
+```
+
+These are the single implementation of the format spec (§3), so the Godot
+client and Python backend never drift.
+
+### 5.3 Network RPCs
+
+The chunk API is exposed to the client via RPCs (matching the networking
+architecture). All chunk traffic is **reliable** (chunks are discrete,
+must-arrive data).
+
+| RPC                        | Direction | Payload                                   | Notes |
+|----------------------------|-----------|-------------------------------------------|-------|
+| `request_chunk`            | C → S     | `{ key }`                                 | Client asks for a chunk |
+| `chunk_data`               | S → C     | `{ key, binary_payload, checksum }`       | Server streams a chunk |
+| `request_chunk_edit`       | C → S     | `{ key, base_revision, delta }`           | Client submits an edit |
+| `chunk_edit_result`        | S → C     | `{ key, success, new_revision, error? }`  | Acknowledges an edit |
+| `chunk_invalidated`        | S → C     | `{ key, new_revision }`                   | Server pushes a change |
+| `request_chunk_flags`      | C → S     | `{ key }`                                 | Age/content gate check |
+
+### 5.4 Edit & Concurrency Model
+
+- **Read:** Client requests a chunk; server returns the binary payload and its
+  `revision`.
+- **Edit:** Client submits a **delta** against a known `base_revision`. The
+  server applies the delta, increments `revision`, persists, and returns the new
+  revision.
+- **Optimistic concurrency:** If the chunk's current revision differs from the
+  client's `base_revision`, the server rejects the edit with a conflict error
+  and the client re-fetches and re-applies. This prevents lost updates when two
+  clients edit the same chunk.
+- **Deltas:** A delta is a JSON patch (RFC 6902 style) applied to the chunk's
+  logical model. The server validates the patched chunk (schema, bounds,
+  moderation) before persisting.
+
+### 5.5 Write-Behind Persistence
+
+To amortize disk I/O, the server keeps a **dirty set** of chunks modified in
+memory and flushes them to SQLite in batches:
+
+1. `put_chunk` updates the in-memory chunk and marks it `dirty`.
+2. A background flusher periodically calls `flush_dirty()`, which writes all
+   dirty chunks in a single transaction and clears the `dirty` flag.
+3. On graceful shutdown, `flush_dirty()` is called to ensure durability.
+
+This keeps the hot path (in-memory chunk access) fast while guaranteeing
+durability at shutdown and on a configurable interval.
+
+**Recovery after unclean shutdown:** The `dirty` column in the `chunks` table
+exists specifically to support recovery if the process crashes before a flush
+completes. On startup, the server scans for rows where `dirty = 1` and treats
+them as **unflushed in-memory state that was lost** — it re-reads the last
+persisted payload from `chunks.payload` (the last durable state) and clears the
+`dirty` flag. In other words, `dirty = 1` at startup means "the last write was
+not durable; discard the in-memory delta and fall back to the persisted
+payload." This guarantees that the on-disk state is always a consistent,
+previously-committed snapshot, never a partially-written chunk. (The in-memory
+dirty set is authoritative during normal operation; the `dirty` column is only a
+recovery marker.)
+
+### 5.6 Streaming & Caching
+
+- The server streams only the chunks a client needs (those within the client's
+  view radius), using `list_chunks` with a bounds query.
+- Chunks are cached in memory (LRU) keyed by `key`; the cache is invalidated on
+  write.
+- The binary payload is content-addressed by `checksum`, so unchanged chunks can
+  be served from cache without re-reading SQLite.
+
+---
+
+## 6. Format Versioning & Migration
+
+- The chunk format `version` field (currently `1`) is checked on decode. A
+  decoder that encounters a higher version than it supports **rejects** the
+  chunk with a clear error rather than misreading it.
+- The SQLite `schema_version` in `meta` drives database migrations (§4.8).
+- Chunk payloads are migrated **lazily**: when a chunk is read and its
+  `format_version` is older than the current one, the server migrates it to the
+  current version in memory and marks it dirty so it is rewritten on the next
+  flush. This avoids a costly full-world migration at startup.
+
+---
+
+## 7. Security & Integrity
+
+- **Server-authoritative writes:** Only the `WorldStore` writes to SQLite;
+  clients submit deltas that are validated before application.
+- **Checksum verification:** Every chunk payload is checksummed (SHA-256) on
+  write and verified on read. Corruption is detected and the chunk is re-fetched
+  or flagged.
+- **Bounds validation:** Chunk coordinates and object positions are validated
+  against the world's chunk dimensions and room bounds before persistence.
+- **Moderation enforcement:** `content_flags` are checked at load time; mature
+  chunks are gated behind the age-verification flow (see `content_moderation.md`).
+- **Input validation:** All string fields are length-limited and validated
+  against allowed character sets to prevent injection and oversized payloads.
+
+---
+
+## 8. Open Questions / Future Work
+
+- **Volumetric worlds:** The schema and format already support `CHUNK_SIZE_Z >
+  1`, but the tooling and streaming for 3D chunks are not yet specified.
+- **Chunk compression:** For very large worlds, the binary payload could be
+  compressed (e.g. zstd) before storage/transfer. The header reserves a `flags`
+  bitmask for a compression flag.
+- **Multi-server sharding:** If a single SQLite file becomes a bottleneck, the
+  `chunks` table could be sharded by `world_id` across multiple databases. The
+  key design already supports this (world_id is a leading key component).
+- **Delta compression for streaming:** Instead of sending full chunks, the
+  server could send only the delta between revisions to reduce bandwidth for
+  frequently-updated chunks.

docs/checkpoints/PC1.md

@@ -0,0 +1,72 @@
+# Package Checkpoint 1 (PC1)
+
+Validated 2026-08-20 against `main` commit `927f9bd`, from a genuinely fresh
+clone (not a reused agent workspace).
+
+## Automated validation
+
+Run with `scripts/run_checkpoint_tests.py` — see
+`docs/testing/test_inventory.md` for exactly what each suite covers.
+
+| Check | Result |
+|---|---|
+| Alembic migrations, fresh DB | PASS |
+| Backend pytest | 68/68 PASS |
+| Godot smoke tests (4 files) | ALL PASS |
+| Linux export (`agp-game.x86_64`) | Builds, verified as a real ELF64 binary |
+| Windows export (`agp-game.exe`) | Builds, verified as a real PE32+ binary |
+
+## Problems found during this checkpoint (fixed, tracked as tasks)
+
+- Roadmap showed the Godot Engine Scaffold feature amber despite 6/6 tasks
+  done — a historical data gap (a review-feedback follow-up task's
+  supersession link was never recorded, predating when that field started
+  being tracked). Backfilled in the PM database; confirmed green.
+- `docs/testing/test_inventory.md` was stale (said 38 backend tests,
+  actually 68; said no integration tests existed, 4 real ones had landed).
+  Fixed via task `398bf1a22a2d` / PR #40.
+
+## What's actually testable right now
+
+Login/register/browse-worlds only — there's no joinable gameplay yet. That's
+the real scope of PC1; don't expect more when playtesting.
+
+- Register a new account (18+ only, rejected otherwise)
+- Log out, log back in with the same credentials
+- Play → Browse Worlds — loads a (currently empty) world list with no errors
+
+## Manual playtest: backend on cloudbison, client on pinkbison
+
+As of 2026-08-20 this is dashboard-controlled — no terminal commands, no
+env vars, no editing files. Foolproof enough to hand to someone else.
+
+### 1. On cloudbison — the AGP dashboard
+
+Open the dashboard (`http://cloudbison:7070`, or its Tailscale address) and
+go to **PC1** in the nav bar (`/checkpoint/PC1`). Click **Start Backend** —
+it pulls the latest `main`, stands up Postgres, runs migrations, and starts
+the API server, all in one step. The page shows the LAN address it's
+reachable at once it's up (under a minute).
+
+When you're done playtesting, click **Stop & Clean Up** on the same page —
+it tears down everything that step started (API server, Postgres
+container, its volume and network). Nothing is left running or lying
+around afterward, even if the dashboard itself gets restarted in between.
+
+### 2. On pinkbison — download and run the .exe
+
+Same dashboard page: click **Build .exe** the first time (or **Rebuild** to
+pick up newer changes) — this pulls the latest `main` and exports a Windows
+binary with cloudbison's backend address already baked in. Click
+**Download agp-game.exe**, copy it to pinkbison, and just run it. No
+environment variable, no config file, no build step on pinkbison at all.
+
+### 3. Tear down when done
+
+**Stop & Clean Up** on the dashboard page. That's it.
+
+## Status
+
+`config/checkpoint_focus_feature_ids` in the AGP framework (`~/agp`) still
+restricts agent claiming to the 5 PC1-scope features. Agents will not move
+on to post-PC1 work until that's widened.

docs/checkpoints/PC3.md

@@ -0,0 +1,97 @@
+# Package Checkpoint 3 (PC3)
+
+> **Status: partial.** PC3's planned scope was M4-avatars + M5-multiplayer +
+> Foundation Hardening + M6–M10 (see `docs/build-plan-v1.md`). As of
+> 2026-09-05, **M4, M5, and most of Foundation Hardening are done and
+> checkpoint-verified**; M6–M10 have not been started. This doc records what
+> is real. Whether to call this "PC3" (redefined scope, M6–M10 → PC4) or keep
+> PC3 open is a user decision.
+
+Built by Claude directly (fleet offline), branch `pc3` → `main`.
+
+## What's real and verified (`scripts/run_checkpoint_tests.py`, all green)
+
+| Check | Result |
+|---|---|
+| Alembic migrations, fresh DB | PASS |
+| Backend `pytest` | 77/77 PASS (hermetic — auto-starts an ephemeral Postgres) |
+| Godot smoke tests (~16 files) | ALL PASS |
+| `smoke_test_network_client` (real dedicated server) | 4/4 PASS |
+| 2-player multiplayer (`run_multiplayer_2p_test.sh`) | PASS |
+| Fresh-clone boot (`verify_fresh_clone.sh`) | PASS |
+| Linux + Windows exports | Build as real ELF64 / PE32+ binaries |
+
+### M4 — Avatars in the game
+
+- Placeholder avatar pack (14 GLBs, rigged 24-bone base body + attachments)
+  generated by `scripts/tools/gen_placeholder_avatars.gd`. Real art is a
+  content swap — catalog paths are stable.
+- The avatar **loader was fixed** — it had never run against a real skeleton
+  (`Skeleton3D.has_bone()` isn't a Godot 4 method; the bone-copy dropped the
+  skin binding; attachments were parsed then discarded).
+- `avatar_visualizer.gd` **rewritten** — the old one referenced a loader API
+  that never existed and didn't compile.
+- Persistence: `avatar_loadouts` table + `GET/PUT /api/avatar/loadout`
+  (loadout stored as one JSON doc; server validates the envelope only).
+- Wired into gameplay: the in-world player renders as the assembled avatar
+  (not a capsule); the loadout is fetched at login; "Customize Avatar" from
+  the main menu saves through to the backend.
+- **Follow-up:** camera is still first-person, so the local player doesn't
+  see their own avatar much (third-person is a polish item); remote players'
+  avatar appearance is not replicated yet (they show as labelled capsules).
+
+### M5 — Real multiplayer
+
+- `server.gd` **actually runs a sim now** — loads the world level, spawns a
+  server player per peer, processes each peer's input queue in seq order at a
+  fixed 30 Hz, broadcasts full snapshots with a per-peer `last_seq`. (The
+  input queue was a no-op before.)
+- `network_client.gd` reconciliation **replays in-flight inputs** from the
+  authoritative state (drops acked ones), snaps only on real drift.
+- **Server orchestration** (`backend/app/services/game_servers.py`): one
+  headless Godot dedicated-server process per world, spawned on demand by
+  `POST /api/worlds/{id}/join`, port-allocated, with a status-file idle
+  reaper. Off by default; the playtest launcher (`checkpoint_ops.py`)
+  enables it.
+- **Client play path**: world browser → `/join` → `Session` → `game.tscn`
+  connects → local player predicts with collision, input forwarded, server
+  position is a drift backstop, remote players render from snapshots,
+  disconnect returns to the world list. Falls back to local single-player
+  when the backend has no orchestration.
+- **Verified**: two real client processes each `register → /join → play`,
+  hosted on an orchestrated server, see and move relative to each other
+  (`run_game_multiplayer_test.sh`).
+
+### Foundation Hardening
+
+- **Hermetic backend tests** — `cd backend && pytest` works from a clean
+  checkout (auto ephemeral Postgres + migrations, torn down after); skips
+  cleanly with a message if there's no Docker.
+- **Fresh-clone boot check** — `verify_fresh_clone.sh` exports a pristine
+  tree, imports from scratch, boots headless, fails on any script error.
+  Also fixed the root cause: a stale `.godot/global_script_class_cache.cfg`
+  was committed to the repo.
+- **Real age verification** — `/register` takes a date of birth (not a
+  checkbox), server computes age, 403 under 18. Still self-attested; the
+  limitation and the ID-check hook are documented
+  (`content_moderation.md` 5.2).
+- **Auth rate limiting** — 10 attempts / min / IP on `/register` + `/login`.
+- **CI workflow** — `.forgejo/workflows/checkpoint.yml` written, **not
+  running yet**: needs the operator to enable Forgejo Actions + register a
+  `host` runner (one-time; see `docs/ci.md`). Interim gate is
+  `run_checkpoint_tests.py` by hand / the dashboard.
+
+## Not in PC3 (planned but not started)
+
+- **M2** server-side world persistence
+- **M6** scripting sandbox
+- **M7** in-game editor
+- **M8** social / chat
+- **M9** economy
+- **M10** discovery
+
+## Playtest
+
+Same as PC2 — grab the exe from the dashboard's `/checkpoints`, backend
+pointed at it. New: with multiple people in the same world you now actually
+see each other move.

docs/ci.md

@@ -0,0 +1,50 @@
+# CI
+
+`.gitea/workflows/checkpoint.yml` runs the full checkpoint suite
+(`scripts/run_checkpoint_tests.py`: migrations on a fresh DB, backend
+`pytest`, all Godot smoke tests, the 2-player multiplayer test, and the
+fresh-clone boot check) on **every push to `main` and every PR**.
+
+## Status: live
+
+Set up 2026-09-05:
+
+- Gitea Actions enabled (`[actions] ENABLED = true` in
+  `/DATA/AppData/forgejo/gitea/conf/app.ini`, container restarted; a
+  timestamped `.bak` is next to it).
+- `act_runner` v0.2.13 registered as **`agp-host`** with label **`host`**
+  (host execution mode — jobs run directly on the AGP box, which already
+  has Docker, `~/godot/godot`, and Python). Lives in `~/act-runner/`.
+- Green on the first successful run (`d76bf4d`).
+
+The workflow uses **no JavaScript actions** (no `actions/checkout`), so the
+host needs no Node: checkout is a shallow `git fetch` from the local Gitea
+using the injected `${{ github.token }}`, and the suite runs in a venv the
+job builds (host Python is PEP-668 externally-managed).
+
+## Make the runner permanent (one command, needs sudo)
+
+The runner currently runs as a plain background process — it won't survive a
+reboot. A unit file is ready at `~/act-runner/act-runner.service`:
+
+```bash
+sudo cp ~/act-runner/act-runner.service /etc/systemd/system/
+sudo systemctl daemon-reload
+pkill -f 'act_runner daemon'          # stop the temporary background one
+sudo systemctl enable --now act-runner
+```
+
+## Interim / local
+
+```bash
+python scripts/run_checkpoint_tests.py
+```
+
+— also what `/checkpoint/<PC>` on the dashboard runs before a playtest build.
+
+## Security note
+
+A host-mode runner executes whatever a workflow says, directly on the box,
+as `daddy` (in the `docker` group). Fine for a single-maintainer private
+repo; revisit if the repo gets outside contributors (switch to a
+docker-mode runner or an isolated VM).

docs/planning/client-server-wiring.md

@@ -0,0 +1,41 @@
+# 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 + register** UI built & wired (form-encoded + JSON/age gate) | 1 |
+| 3 | implementation | **World list** screen consuming `GET /api/worlds` | 1 |
+| 4 | testing | End-to-end headless smoke test + manual verify | 1,2,3 |
+
+## 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.
+
+## Notes
+- The main-menu auth UI does **not** exist yet (main_menu.gd currently has only Play/Quit
+  stubs). Task 2 must **build** the login/register UI, not merely wire an existing one.
+- The world-list screen also needs to be **built** (a new scene), not just wired.

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).

docs/planning/social.md

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+# Social — Friends, Chat & Groups — Plan
+
+> **Status:** Planned
+> **Owner:** Platform team
+> **Feature ID:** `social`
+> **Godot version:** 4.6.2 stable
+> **Backend:** FastAPI + SQLAlchemy (async) + PostgreSQL + Redis
+
+## 1. Overview
+
+This document breaks the **Social** feature into user stories and right-sized
+implementation tasks. The feature delivers:
+
+- **Friends & following** — a friend request/accept model plus a one-way follow
+  relationship, with block lists.
+- **Presence & status** — online/offline, custom status message, last-seen.
+- **Chat** — direct messages (DM) and in-experience (world/room) chat with
+  **first-class safety**: server-side text filtering, report-message, and rate
+  limiting.
+- **Groups** — named groups with roles (owner/admin/member) and a simple group
+  page.
+- **Public profiles** — avatar, bio, favorite experiences, and a friends list
+  that respects privacy settings.
+
+## 2. Why chat safety is the differentiator
+
+The platform is explicitly meant to pull adults away from a youth-oriented
+competitor. Chat is the highest-risk surface: it is real-time, user-generated,
+and where abuse happens fastest. Safety is therefore treated as a **blocking
+requirement**, not an add-on:
+
+- Every message passes a **server-side text filter** before it is stored or
+  delivered. The client filter is cosmetic only; the server is authoritative.
+- Every message can be **reported**; reports flow into a moderation queue with
+  actor + reason + audit trail (mirroring `content_moderation.md`).
+- Sending is **rate limited** per user (Redis token bucket) to stop flooding and
+  harassment-by-volume.
+- Report and block are always reachable from a message context in the UI.
+
+## 3. Existing constraints (do not re-build)
+
+- **Auth:** JWT bearer tokens; `get_current_user` / `CurrentUser` dependency in
+  `app/dependencies.py`. All social endpoints reuse this.
+- **DB:** async SQLAlchemy + Alembic; migration `0001_initial` is the head.
+- **Redis:** configured (`REDIS_URL`) but unused so far; adopted here for
+  presence and rate limiting.
+- **Models:** `User`, `World` (owner_id), `Asset` (owner_id, is_public). Avatars
+  and favorite-experience references point at existing rows.
+- **Client:** Godot 4.6.2, minimal `main_menu.gd`; no social UI yet.
+
+## 4. Key design decisions
+
+| Concern | Decision |
+|---|---|
+| Message transport | REST for send/history; **WebSocket** gateway for real-time delivery + presence (matches `networking.md`'s "WebSocket as secondary transport" for chat) |
+| Presence store | Redis (TTL heartbeat) + persisted `last_seen_at` on the user record |
+| Text filtering | Pluggable `TextFilter` interface with a deterministic default (profanity list + normalization) so it runs without external services; third-party hook later |
+| Rate limiting | Redis token-bucket dependency, reusable across all social endpoints |
+| Reports | `message_reports` table + moderation endpoints (list/review/resolve) with audit fields |
+| Friends vs. follow | Friends = mutual (request→accept). Follow = one-way (no approval). Block = hard deny that also hides content and prevents DMs |
+| Privacy | Per-user settings JSON (`profile_visibility`, `friends_list_visibility`, `favorites_visibility`) enforced server-side on every read |
+| Groups | `groups` + `group_members` (role: owner/admin/member) + group page aggregate endpoint |
+| Real-time | One WebSocket endpoint multiplexing presence, DM, and world-chat messages via Redis pub/sub |
+
+## 5. User stories
+
+### US-1 Friends & following
+As a player, I can send a friend request, accept/decline incoming requests,
+unfriend, follow/unfollow other players, and block users so they can't interact
+with me.
+
+**Acceptance criteria**
+- Friend requests are one-directional until accepted; accepted friendships are mutual.
+- Follow is one-way and requires no approval.
+- Block prevents DMs, hides the blocked user's profile/friends interactions, and
+  removes any existing friendship/follow between the two.
+- Duplicate/self requests are rejected idempotently.
+
+### US-2 Presence & status
+As a player, I can see whether my friends are online, their custom status, and
+when they were last seen.
+
+**Acceptance criteria**
+- Online/offline is derived from a server-side heartbeat (Redis TTL), not client claims.
+- `last_seen_at` persists and is visible (subject to privacy settings).
+- Custom status text is optional and length-limited.
+
+### US-3 Public profiles
+As a player, I can view a public profile page showing avatar, bio, favorite
+experiences, and a friends list that respects the owner's privacy settings.
+
+**Acceptance criteria**
+- Avatar and bio are editable by the owner only.
+- Favorite experiences reference existing `World` rows.
+- A viewer sees only the sections the owner's privacy settings allow; blocked
+  users see a restricted view.
+
+### US-4 Chat (DM + in-experience) with safety
+As a player, I can send direct messages and chat inside a world/room. Messages
+are filtered, rate limited, and reportable.
+
+**Acceptance criteria**
+- Server filters message text before storing/delivering; filtered content is either
+  rejected (blocking) or redacted (configurable per filter policy).
+- Send rate is limited per user (token bucket); excess sends get `429`.
+- Every message has a stable id, author, timestamp, and conversation/world scope.
+- Any message can be reported with a reason; reports are stored and reviewable.
+- Real-time delivery over WebSocket with REST fallback for history.
+
+### US-5 Groups
+As a player, I can create a group, join/leave groups, and (as owner/admin)
+manage roles and view a simple group page.
+
+**Acceptance criteria**
+- Each group has exactly one owner and any number of admins/members.
+- Role transitions are authorized (only owner can transfer ownership or promote/demote admins).
+- Group page lists name, description, member list with roles, and member count.
+
+### US-6 Godot client
+As a player, I can access friends, presence, chat, profiles, and groups from the
+game UI.
+
+**Acceptance criteria**
+- An API client handles JWT auth, HTTP, and WebSocket for all social calls.
+- Dedicated screens/panels: friends+presence, DM & world chat (with report),
+  profile page, group page.
+- Client-side filtering is cosmetic; server responses remain authoritative.
+
+## 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 | Friends/follow/block models + Alembic migration | US-1 | — |
+| 2 | Friends & follow API router | US-1 | 1 |
+| 3 | Presence & status model + endpoints (Redis heartbeat) | US-2 | — |
+| 4 | Profile model + migration + own-profile endpoints | US-3 | 1 |
+| 5 | Public profile view + favorites + privacy enforcement | US-3 | 2, 4 |
+| 6 | Chat data models + migration (conversations, messages, reports) | US-4 | — |
+| 7 | Text filtering service + profanity config | US-4 | — |
+| 8 | Redis rate-limiting dependency | US-4 | — |
+| 9 | DM chat send/list endpoints (filter + rate limit) | US-4 | 6, 7, 8 |
+| 10 | Report-message endpoint + moderation queue | US-4 | 6, 9 |
+| 11 | In-experience (world/room) chat endpoints | US-4 | 9 |
+| 12 | Real-time WebSocket gateway (presence + DM + world chat) | US-4 | 3, 9, 11 |
+| 13 | Group + membership models + migration | US-5 | — |
+| 14 | Groups API (CRUD, join/leave, roles, group page) | US-5 | 13 |
+| 15 | Godot API client (auth + HTTP + WebSocket) | US-6 | 2 |
+| 16 | Godot friends & presence UI | US-6 | 3, 15 |
+| 17 | Godot chat UI (DM + world chat + report) | US-6 | 12, 15 |
+| 18 | Godot profile page UI | US-6 | 5, 15 |
+| 19 | Godot groups UI + group page | US-6 | 14, 15 |
+
+## 7. Phasing
+
+- **Phase 1 (data + core APIs):** tasks 1–5 (friends, presence, profiles).
+- **Phase 2 (chat safety — the differentiator):** tasks 6–12 (chat + safety +
+  realtime). This is the critical path and highest priority.
+- **Phase 3 (groups):** tasks 13–14.
+- **Phase 4 (client):** tasks 15–19, each landing after its backend dependency.
+
+## 8. Out of scope for this feature
+
+- Age verification / maturity gating (covered by `content_moderation.md`).
+- Voice chat, media/image messages, message editing/deletion history.
+- Third-party profanity/toxicity vendors (the `TextFilter` interface leaves a
+  hook, but the default is deterministic and dependency-free).
+- Mobile push notifications.

docs/testing/README.md

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+# Testing at Package Checkpoints
+
+A Package Checkpoint (PC1, PC2, ...) is a periodic review point — every few
+real milestones, the client and server builds get packaged together and
+independently reviewed before anyone calls anything actually done. See
+`project_agp` in Claude's memory, or ask, for the full definition; this
+doc is just the mechanical "how do I run the tests" part of that review.
+
+## Running the suite
+
+```
+python scripts/run_checkpoint_tests.py
+```
+
+Brings up a throwaway Postgres, runs Alembic migrations against it, runs the
+backend pytest suite, starts the backend server, and runs every Godot
+headless smoke test (`scripts/smoke_test_*.gd`) against it. Tears the
+Postgres container down afterward (`--keep-postgres` to skip that if you
+want to poke at the DB after a failure).
+
+If port 5432 is already taken on the machine, pass `--postgres-port` with
+something else.
+
+Exit code is 0 only if everything that actually ran passed — suites with
+nothing to run yet (no Godot binary found, no smoke test scripts yet) are
+reported SKIPPED, not treated as a failure.
+
+## What this does and doesn't prove
+
+Passing this script means: migrations apply cleanly to a genuinely empty
+database, the backend's unit-level logic is correct, and whatever Godot
+smoke tests exist actually round-trip against a live backend. It does
+**not** mean full endpoint/integration coverage exists — see
+`test_inventory.md` for the current, honest list of what's tested and what
+isn't. A checkpoint review should still involve reading the actual diffs
+for anything this script's current coverage doesn't reach, not just running
+green and calling it done.
+
+## Growing this over time
+
+As real integration tests get added (endpoint tests hitting the FastAPI app,
+more Godot smoke coverage beyond `health_check`), they should land under
+`backend/tests/` / `scripts/smoke_test_*.gd` respectively — this script
+picks up new files automatically, nothing to register by hand. Update
+`test_inventory.md`'s tables when you do, so the inventory stays a source
+of truth instead of quietly going stale.
+
+Eventual goal (not implemented yet): gate merges to `main` on this script
+passing, the same way a real CI pipeline would. For now it's a manual step
+run at checkpoint review time.