diff --git a/tests/vllm_demo/test_world_graph.py b/tests/vllm_demo/test_world_graph.py
new file mode 100644
index 0000000..12a99b4
--- /dev/null
+++ b/tests/vllm_demo/test_world_graph.py
@@ -0,0 +1,139 @@
+"""
+Unit tests for WorldGraph
+"""
+
+from world_graph import (
+    WorldGraph, Room, Door, WorldObject, Direction,
+    AgentInfo, create_two_room_scenario, create_button_door_scenario
+)
+
+def test_room_contains():
+    """Test room boundary checking."""
+    room = Room("test", "test room", bounds=(5, 5, 10, 10))
+
+    assert room.contains(5, 5) == True   # Top-left corner
+    assert room.contains(14, 14) == True # Bottom-right (exclusive)
+    assert room.contains(15, 15) == False # Outside
+    assert room.contains(4, 5) == False  # Just outside left
+
+    print("PASS: room_contains")
+
+def test_room_at():
+    """Test spatial room lookup."""
+    world = create_two_room_scenario()
+
+    # Guard room is at (1,1) with size (8,8)
+    room = world.room_at(3, 3)
+    assert room is not None
+    assert room.name == "guard_room"
+
+    # Armory is at (11,1) with size (8,8)
+    room = world.room_at(13, 3)
+    assert room is not None
+    assert room.name == "armory"
+
+    # Between rooms (the door area) - should return None
+    room = world.room_at(9, 4)
+    assert room is None
+
+    print("PASS: room_at")
+
+def test_describe_room_basic():
+    """Test basic room description."""
+    world = create_two_room_scenario()
+
+    desc = world.describe_room("guard_room")
+
+    assert "You are in the guard room" in desc
+    assert "brass key" in desc
+    assert "Exits:" in desc
+    assert "east" in desc
+    assert "armory" in desc
+
+    print("PASS: describe_room_basic")
+    print(f"  Output: {desc}")
+
+def test_describe_room_with_agents():
+    """Test room description with visible agents."""
+    world = create_two_room_scenario()
+
+    agents = [
+        AgentInfo("Wizard", "a wizard", (3, 3)),
+        AgentInfo("Knight", "a knight", (4, 4)),
+    ]
+
+    desc = world.describe_room("guard_room", visible_agents=agents, observer_name="Wizard")
+
+    assert "knight" in desc.lower()
+    assert "wizard" not in desc.lower()  # Observer excluded
+
+    print("PASS: describe_room_with_agents")
+    print(f"  Output: {desc}")
+
+def test_describe_locked_door():
+    """Test that locked doors are described correctly."""
+    world = create_button_door_scenario()
+
+    desc = world.describe_room("button_room")
+
+    assert "locked" in desc.lower()
+
+    print("PASS: describe_locked_door")
+    print(f"  Output: {desc}")
+
+def test_available_actions():
+    """Test action enumeration."""
+    world = create_two_room_scenario()
+
+    actions = world.get_available_actions("guard_room")
+
+    assert "GO EAST" in actions
+    assert "TAKE brass_key" in actions
+    assert "LOOK" in actions
+    assert "WAIT" in actions
+
+    print("PASS: available_actions")
+    print(f"  Actions: {actions}")
+
+def test_determinism():
+    """Test that descriptions are deterministic."""
+    world = create_two_room_scenario()
+
+    desc1 = world.describe_room("guard_room")
+    desc2 = world.describe_room("guard_room")
+    desc3 = world.describe_room("guard_room")
+
+    assert desc1 == desc2 == desc3, "Descriptions must be deterministic!"
+
+    print("PASS: determinism")
+
+def test_direction_opposites():
+    """Test direction opposite calculation."""
+    assert Direction.NORTH.opposite == Direction.SOUTH
+    assert Direction.SOUTH.opposite == Direction.NORTH
+    assert Direction.EAST.opposite == Direction.WEST
+    assert Direction.WEST.opposite == Direction.EAST
+
+    print("PASS: direction_opposites")
+
+def run_all_tests():
+    """Run all WorldGraph tests."""
+    print("=" * 50)
+    print("WorldGraph Unit Tests")
+    print("=" * 50)
+
+    test_room_contains()
+    test_room_at()
+    test_describe_room_basic()
+    test_describe_room_with_agents()
+    test_describe_locked_door()
+    test_available_actions()
+    test_determinism()
+    test_direction_opposites()
+
+    print("=" * 50)
+    print("All tests passed!")
+    print("=" * 50)
+
+if __name__ == "__main__":
+    run_all_tests()
diff --git a/tests/vllm_demo/world_graph.py b/tests/vllm_demo/world_graph.py
new file mode 100644
index 0000000..c923d1e
--- /dev/null
+++ b/tests/vllm_demo/world_graph.py
@@ -0,0 +1,474 @@
+"""
+WorldGraph: Room-based World Representation
+============================================
+
+Provides dual-purpose data structures for:
+1. Generating 2D tilemaps (visual representation)
+2. Generating text descriptions (LLM context)
+
+Ensures deterministic text output: same state = same description.
+"""
+
+from dataclasses import dataclass, field
+from typing import Dict, List, Optional, Tuple, Any
+from enum import Enum
+
+
+class Direction(Enum):
+    NORTH = "north"
+    SOUTH = "south"
+    EAST = "east"
+    WEST = "west"
+
+    @property
+    def opposite(self) -> 'Direction':
+        opposites = {
+            Direction.NORTH: Direction.SOUTH,
+            Direction.SOUTH: Direction.NORTH,
+            Direction.EAST: Direction.WEST,
+            Direction.WEST: Direction.EAST,
+        }
+        return opposites[self]
+
+    @property
+    def vector(self) -> Tuple[int, int]:
+        vectors = {
+            Direction.NORTH: (0, -1),
+            Direction.SOUTH: (0, 1),
+            Direction.EAST: (1, 0),
+            Direction.WEST: (-1, 0),
+        }
+        return vectors[self]
+
+
+@dataclass
+class Room:
+    """A room in the world graph."""
+    name: str                           # Internal ID: "kitchen", "guard_room"
+    display_name: str                   # Text output: "the kitchen", "a dimly lit guard room"
+    bounds: Tuple[int, int, int, int]   # (x, y, width, height) in tile coords
+    properties: Dict[str, Any] = field(default_factory=dict)  # {"lit": True, "temperature": "warm"}
+    description_template: Optional[str] = None  # "A {temperature} room with {features}."
+
+    @property
+    def x(self) -> int:
+        return self.bounds[0]
+
+    @property
+    def y(self) -> int:
+        return self.bounds[1]
+
+    @property
+    def width(self) -> int:
+        return self.bounds[2]
+
+    @property
+    def height(self) -> int:
+        return self.bounds[3]
+
+    @property
+    def center(self) -> Tuple[int, int]:
+        return (self.x + self.width // 2, self.y + self.height // 2)
+
+    def contains(self, x: int, y: int) -> bool:
+        """Check if a tile coordinate is within this room."""
+        return (self.x <= x < self.x + self.width and
+                self.y <= y < self.y + self.height)
+
+
+@dataclass
+class Door:
+    """A connection between two rooms."""
+    room_a: str                     # Room name
+    room_b: str                     # Room name
+    position: Tuple[int, int]       # Tile position of the door
+    direction_from_a: Direction     # Direction from room_a to reach room_b
+    locked: bool = False
+    key_id: Optional[str] = None    # Which key unlocks this door
+
+    @property
+    def direction_from_b(self) -> Direction:
+        return self.direction_from_a.opposite
+
+
+@dataclass
+class WorldObject:
+    """An interactable object in the world."""
+    name: str                       # Internal ID: "brass_key"
+    display_name: str               # Text output: "a brass key"
+    room: str                       # Which room contains it
+    position: Tuple[int, int]       # Tile position (or None if carried)
+    affordances: List[str] = field(default_factory=list)  # ["takeable", "unlocks:pantry_door"]
+    description: str = ""           # "A tarnished brass key with ornate handle."
+
+
+@dataclass
+class AgentInfo:
+    """Information about an agent for description purposes."""
+    name: str                       # "Wizard", "Knight"
+    display_name: str               # "a wizard", "the knight"
+    position: Tuple[int, int]       # Current tile position
+    is_player: bool = False         # Is this the observing agent?
+
+
+class WorldGraph:
+    """
+    Graph-based world representation.
+
+    Provides:
+    - Room/door/object storage
+    - Deterministic text description generation
+    - Spatial queries (what room is at x,y?)
+    - Available action enumeration
+    """
+
+    def __init__(self):
+        self.rooms: Dict[str, Room] = {}
+        self.doors: List[Door] = []
+        self.objects: Dict[str, WorldObject] = {}
+
+    # =========================================================================
+    # Building the World
+    # =========================================================================
+
+    def add_room(self, room: Room) -> None:
+        """Add a room to the world."""
+        self.rooms[room.name] = room
+
+    def add_door(self, door: Door) -> None:
+        """Add a door connecting two rooms."""
+        self.doors.append(door)
+
+    def add_object(self, obj: WorldObject) -> None:
+        """Add an object to the world."""
+        self.objects[obj.name] = obj
+
+    # =========================================================================
+    # Spatial Queries
+    # =========================================================================
+
+    def room_at(self, x: int, y: int) -> Optional[Room]:
+        """Get the room containing a tile coordinate."""
+        for room in self.rooms.values():
+            if room.contains(x, y):
+                return room
+        return None
+
+    def get_exits(self, room_name: str) -> List[Door]:
+        """Get all doors leading out of a room."""
+        exits = []
+        for door in self.doors:
+            if door.room_a == room_name or door.room_b == room_name:
+                exits.append(door)
+        return exits
+
+    def get_door_in_direction(self, room_name: str, direction: Direction) -> Optional[Door]:
+        """Get the door in a specific direction from a room."""
+        for door in self.doors:
+            if door.room_a == room_name and door.direction_from_a == direction:
+                return door
+            if door.room_b == room_name and door.direction_from_b == direction:
+                return door
+        return None
+
+    def get_objects_in_room(self, room_name: str) -> List[WorldObject]:
+        """Get all objects in a room."""
+        return [obj for obj in self.objects.values() if obj.room == room_name]
+
+    # =========================================================================
+    # Text Description Generation (Deterministic!)
+    # =========================================================================
+
+    def describe_room(self, room_name: str,
+                      visible_agents: List[AgentInfo] = None,
+                      observer_name: str = None) -> str:
+        """
+        Generate a complete room description.
+
+        Args:
+            room_name: The room to describe
+            visible_agents: List of agents visible in the room
+            observer_name: Name of the observing agent (excluded from description)
+
+        Returns:
+            Deterministic prose description of the room
+        """
+        room = self.rooms.get(room_name)
+        if not room:
+            return "You are in an unknown location."
+
+        parts = []
+
+        # Base location
+        parts.append(f"You are in {room.display_name}.")
+
+        # Room template description (if any)
+        if room.description_template and room.properties:
+            try:
+                desc = room.description_template.format(**room.properties)
+                parts.append(desc)
+            except KeyError:
+                pass
+
+        # Visible agents
+        if visible_agents:
+            agent_desc = self._describe_agents(visible_agents, observer_name)
+            if agent_desc:
+                parts.append(agent_desc)
+
+        # Objects on the ground
+        objects = self.get_objects_in_room(room_name)
+        if objects:
+            obj_desc = self._describe_objects(objects)
+            parts.append(obj_desc)
+
+        # Exits
+        exits = self.get_exits(room_name)
+        parts.append(self._describe_exits(room_name, exits))
+
+        return " ".join(parts)
+
+    def _describe_agents(self, agents: List[AgentInfo], observer_name: str = None) -> str:
+        """Describe visible agents (excluding observer)."""
+        others = [a for a in agents if a.name != observer_name and not a.is_player]
+        if not others:
+            return ""
+
+        if len(others) == 1:
+            return f"You see {others[0].display_name} here."
+        else:
+            names = [a.display_name for a in others]
+            formatted = ", ".join(names[:-1]) + f" and {names[-1]}"
+            return f"You see {formatted} here."
+
+    def _describe_objects(self, objects: List[WorldObject]) -> str:
+        """Describe objects in the room."""
+        if not objects:
+            return ""
+
+        # Group by affordance for natural description
+        takeable = [o for o in objects if "takeable" in o.affordances]
+        furniture = [o for o in objects if "takeable" not in o.affordances]
+
+        parts = []
+        if takeable:
+            if len(takeable) == 1:
+                parts.append(f"On the ground you see {takeable[0].display_name}.")
+            else:
+                names = [o.display_name for o in takeable]
+                formatted = ", ".join(names[:-1]) + f" and {names[-1]}"
+                parts.append(f"On the ground you see {formatted}.")
+
+        if furniture:
+            for obj in furniture:
+                parts.append(f"There is {obj.display_name} here.")
+
+        return " ".join(parts)
+
+    def _describe_exits(self, room_name: str, exits: List[Door]) -> str:
+        """Describe available exits."""
+        if not exits:
+            return "There are no visible exits."
+
+        exit_parts = []
+        for door in exits:
+            # Determine direction and destination from this room's perspective
+            if door.room_a == room_name:
+                direction = door.direction_from_a.value
+                dest_room = self.rooms.get(door.room_b)
+            else:
+                direction = door.direction_from_b.value
+                dest_room = self.rooms.get(door.room_a)
+
+            dest_name = dest_room.display_name if dest_room else "unknown"
+
+            if door.locked:
+                exit_parts.append(f"{direction} ({dest_name}, locked)")
+            else:
+                exit_parts.append(f"{direction} ({dest_name})")
+
+        # Sort for deterministic output
+        exit_parts.sort()
+
+        return "Exits: " + ", ".join(exit_parts) + "."
+
+    # =========================================================================
+    # Action Enumeration
+    # =========================================================================
+
+    def get_available_actions(self, room_name: str,
+                              can_speak: bool = True) -> List[str]:
+        """
+        Get list of available actions for an agent in a room.
+
+        Returns list of action strings like:
+        ["GO NORTH", "GO EAST", "TAKE brass_key", "WAIT", "LOOK"]
+        """
+        actions = ["LOOK", "WAIT"]
+
+        # Movement actions
+        for door in self.get_exits(room_name):
+            if door.room_a == room_name:
+                direction = door.direction_from_a.value.upper()
+            else:
+                direction = door.direction_from_b.value.upper()
+
+            if not door.locked:
+                actions.append(f"GO {direction}")
+            else:
+                # Could add UNLOCK action here if agent has key
+                pass
+
+        # Object interactions
+        for obj in self.get_objects_in_room(room_name):
+            if "takeable" in obj.affordances:
+                actions.append(f"TAKE {obj.name}")
+            if "pushable" in obj.affordances:
+                actions.append(f"PUSH {obj.name} <direction>")
+            if "openable" in obj.affordances:
+                actions.append(f"OPEN {obj.name}")
+            if "readable" in obj.affordances:
+                actions.append(f"READ {obj.name}")
+
+        # Speech actions
+        if can_speak:
+            actions.append("ANNOUNCE '<message>'")
+            actions.append("SPEAK '<message>'")
+
+        return sorted(actions)
+
+
+# =============================================================================
+# Factory Functions for Common Scenarios
+# =============================================================================
+
+def create_two_room_scenario() -> WorldGraph:
+    """
+    Create a simple two-room test scenario.
+
+    Layout:
+    +--------+   +--------+
+    | Room A |===| Room B |
+    | (west) |   | (east) |
+    +--------+   +--------+
+
+    Room A: "the guard room" - contains a brass key
+    Room B: "the armory" - destination room
+    Door: unlocked, between rooms
+    """
+    world = WorldGraph()
+
+    # Room A (left side)
+    room_a = Room(
+        name="guard_room",
+        display_name="the guard room",
+        bounds=(1, 1, 8, 8),  # x, y, width, height
+        properties={"lit": True, "atmosphere": "musty"},
+        description_template="The air is {atmosphere}."
+    )
+    world.add_room(room_a)
+
+    # Room B (right side)
+    room_b = Room(
+        name="armory",
+        display_name="the armory",
+        bounds=(11, 1, 8, 8),
+        properties={"lit": True, "atmosphere": "cold"},
+        description_template="Weapon racks line the walls."
+    )
+    world.add_room(room_b)
+
+    # Door connecting them
+    door = Door(
+        room_a="guard_room",
+        room_b="armory",
+        position=(9, 4),  # Between the rooms
+        direction_from_a=Direction.EAST,
+        locked=False
+    )
+    world.add_door(door)
+
+    # Object in Room A
+    key = WorldObject(
+        name="brass_key",
+        display_name="a brass key",
+        room="guard_room",
+        position=(3, 3),
+        affordances=["takeable", "unlocks:dungeon_door"],
+        description="A tarnished brass key with an ornate handle."
+    )
+    world.add_object(key)
+
+    return world
+
+
+def create_button_door_scenario() -> WorldGraph:
+    """
+    Create the Phase 1 scenario from issue #154.
+
+    Layout:
+    +----------+   +----------+
+    | Room A   |   | Room B   |
+    | [Button] |===| [Goal]   |
+    | Agent A  |   | Agent B  |
+    +----------+   +----------+
+
+    - Door starts locked
+    - Button in Room A unlocks the door
+    - Agent A can reach button; Agent B's goal is blocked by door
+    - Success: Agents coordinate to solve puzzle
+    """
+    world = WorldGraph()
+
+    # Room A (button room)
+    room_a = Room(
+        name="button_room",
+        display_name="the button room",
+        bounds=(1, 1, 8, 8),
+        properties={"lit": True}
+    )
+    world.add_room(room_a)
+
+    # Room B (goal room)
+    room_b = Room(
+        name="goal_room",
+        display_name="the goal room",
+        bounds=(11, 1, 8, 8),
+        properties={"lit": True}
+    )
+    world.add_room(room_b)
+
+    # Locked door
+    door = Door(
+        room_a="button_room",
+        room_b="goal_room",
+        position=(9, 4),
+        direction_from_a=Direction.EAST,
+        locked=True,
+        key_id="button_mechanism"
+    )
+    world.add_door(door)
+
+    # Button in Room A
+    button = WorldObject(
+        name="wall_button",
+        display_name="a large button on the wall",
+        room="button_room",
+        position=(2, 4),
+        affordances=["pressable", "activates:main_door"],
+        description="A heavy stone button protrudes from the wall."
+    )
+    world.add_object(button)
+
+    # Goal marker in Room B
+    goal = WorldObject(
+        name="goal_marker",
+        display_name="a glowing rune on the floor",
+        room="goal_room",
+        position=(15, 4),
+        affordances=["examinable"],
+        description="An arcane symbol pulses with soft light."
+    )
+    world.add_object(goal)
+
+    return world