Add rulebook RAG pipeline and LLM-driven game setup wizard

RAG: switch Postgres to pgvector, chunk and embed the three D&D
rulebooks locally via sentence-transformers, and retrieve relevant
excerpts per DM turn (query = latest player message) to ground the
system prompt. Retrieval runs off the event loop and is capped by a
relevance threshold and a max character budget so it can't blow up
context size or cost.

Game setup wizard: creating a game now opens a short chat where the
DM asks about genre, length, and the player's experience level, then
proposes a name and description via a tool call. The player can edit
both before creating the game. Stateless endpoint — the frontend
carries the conversation, no DB needed since the game doesn't exist
yet.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/app/alembic/versions/7c3f9a2e1d44_add_rulebook_chunks.py

@@ -0,0 +1,43 @@
+"""add rulebook_chunks (pgvector RAG)
+
+Revision ID: 7c3f9a2e1d44
+Revises: 48846ed4fe0e
+Create Date: 2026-08-31 19:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+from pgvector.sqlalchemy import Vector
+
+# revision identifiers, used by Alembic.
+revision: str = '7c3f9a2e1d44'
+down_revision: Union[str, None] = '48846ed4fe0e'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.execute("CREATE EXTENSION IF NOT EXISTS vector")
+
+    op.create_table(
+        'rulebook_chunks',
+        sa.Column('id', sa.UUID(), nullable=False),
+        sa.Column('source_document', sa.String(length=200), nullable=False),
+        sa.Column('chunk_index', sa.Integer(), nullable=False),
+        sa.Column('content', sa.Text(), nullable=False),
+        sa.Column('embedding', Vector(384), nullable=False),
+        sa.Column('doc_metadata', postgresql.JSONB(astext_type=sa.Text()), nullable=False),
+        sa.PrimaryKeyConstraint('id'),
+    )
+    op.create_index(
+        op.f('ix_rulebook_chunks_source_document'), 'rulebook_chunks', ['source_document'], unique=False
+    )
+
+
+def downgrade() -> None:
+    op.drop_index(op.f('ix_rulebook_chunks_source_document'), table_name='rulebook_chunks')
+    op.drop_table('rulebook_chunks')
+    op.execute("DROP EXTENSION IF EXISTS vector")

backend/app/api/routes_games.py

@@ -8,11 +8,13 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.auth.users import current_active_user
 from app.db import get_async_session
+from app.llm.game_setup import run_game_setup_turn
 from app.models.character import Character
 from app.models.game import Game, GameParticipant
 from app.models.message import Message
 from app.models.user import User
 from app.schemas.game import GameCreate, GameJoin, GameRead
+from app.schemas.game_setup import GameSetupChatRequest, GameSetupChatResponse
 from app.schemas.message import MessageRead
 from app.ws_tickets import issue_ticket
 
@@ -108,6 +110,15 @@ async def create_game(
     return serialized[0]
 
 
+@router.post("/setup-chat", response_model=GameSetupChatResponse)
+async def game_setup_chat(
+    payload: GameSetupChatRequest,
+    user: User = Depends(current_active_user),
+) -> GameSetupChatResponse:
+    result = await run_game_setup_turn(payload.messages)
+    return GameSetupChatResponse(**result)
+
+
 @router.get("/{game_id}", response_model=GameRead)
 async def get_game(
     game_id: uuid.UUID,

backend/app/api/ws_game.py

@@ -120,7 +120,7 @@ async def game_websocket(websocket: WebSocket, game_id: uuid.UUID, ticket: str)
                     )
 
                     try:
-                        dm_message = await run_dm_turn(session, game_id)
+                        dm_message = await run_dm_turn(session, game_id, latest_player_message=content)
                     except Exception:  # noqa: BLE001
                         logger.exception("DM turn failed for game %s", game_id)
                         await websocket.send_json({"type": "error", "detail": "dm_turn_failed"})

backend/app/llm/client.py

@@ -13,6 +13,11 @@ def get_dm_system_prompt() -> str:
     return (PROMPTS_DIR / "dm_system_prompt.txt").read_text(encoding="utf-8")
 
 
+@lru_cache
+def get_game_setup_prompt() -> str:
+    return (PROMPTS_DIR / "game_setup_prompt.txt").read_text(encoding="utf-8")
+
+
 @lru_cache
 def get_llm_client() -> AsyncOpenAI:
     return AsyncOpenAI(api_key=settings.xai_api_key, base_url=settings.xai_base_url)

backend/app/llm/game_setup.py

@@ -0,0 +1,55 @@
+import json
+
+from app.config import settings
+from app.llm.client import get_game_setup_prompt, get_llm_client
+from app.llm.tools import game_setup as game_setup_tool
+
+MAX_ROUNDS = 3
+MAX_TOKENS = 1024
+
+TOOLS = [{"type": "function", "function": game_setup_tool.TOOL_SCHEMA}]
+
+
+async def run_game_setup_turn(client_messages: list[dict]) -> dict:
+    """Stateless setup-wizard turn: the caller owns conversation history (no DB, no game yet).
+
+    Returns {"messages": <history to resend next turn>, "assistant_text": str | None,
+    "proposal": {"name": str, "description": str} | None}.
+    """
+    client = get_llm_client()
+    messages = [{"role": "system", "content": get_game_setup_prompt()}] + client_messages
+
+    assistant_text: str | None = None
+    proposal: dict | None = None
+
+    for _ in range(MAX_ROUNDS):
+        response = await client.chat.completions.create(
+            model=settings.dm_model,
+            max_tokens=MAX_TOKENS,
+            messages=messages,
+            tools=TOOLS,
+        )
+        message = response.choices[0].message
+        if message.content:
+            assistant_text = message.content
+
+        if not message.tool_calls:
+            messages.append({"role": "assistant", "content": message.content or ""})
+            break
+
+        messages.append(message.model_dump(exclude_unset=True))
+        for tool_call in message.tool_calls:
+            args = json.loads(tool_call.function.arguments)
+            if tool_call.function.name == "propose_game_setup":
+                proposal = {"name": args.get("name", ""), "description": args.get("description", "")}
+            messages.append(
+                {
+                    "role": "tool",
+                    "tool_call_id": tool_call.id,
+                    "content": json.dumps({"status": "ok"}),
+                }
+            )
+        if proposal:
+            break
+
+    return {"messages": messages[1:], "assistant_text": assistant_text, "proposal": proposal}

backend/app/llm/orchestrator.py

@@ -4,13 +4,14 @@ import uuid
 
 from sqlalchemy.ext.asyncio import AsyncSession
 
-logger = logging.getLogger("app.llm.orchestrator")
-
 from app.config import settings
 from app.llm.client import get_dm_system_prompt, get_llm_client
 from app.llm.context import build_context
 from app.llm.tools import character_sheet, dice
 from app.models.message import Message
+from app.rag.retrieval import build_rag_block
+
+logger = logging.getLogger("app.llm.orchestrator")
 
 MAX_TOOL_ROUNDS = 5
 MAX_TOKENS = 4096
@@ -38,9 +39,18 @@ async def _execute_tool_call(
         return {"error": str(exc)}
 
 
-async def run_dm_turn(session: AsyncSession, game_id: uuid.UUID) -> Message:
+async def run_dm_turn(
+    session: AsyncSession, game_id: uuid.UUID, latest_player_message: str | None = None
+) -> Message:
     client = get_llm_client()
-    messages = [{"role": "system", "content": get_dm_system_prompt()}]
+    system_prompt = get_dm_system_prompt()
+
+    if latest_player_message:
+        rag_block = await build_rag_block(session, latest_player_message)
+        if rag_block:
+            system_prompt = f"{system_prompt}\n\n{rag_block}"
+
+    messages = [{"role": "system", "content": system_prompt}]
     messages.extend(await build_context(session, game_id))
 
     final_text = ""

backend/app/llm/prompts/game_setup_prompt.txt

@@ -0,0 +1,21 @@
+Rolle
+Du hilfst einem Spieler dabei, ein neues D&D-Spiel einzurichten, bevor es losgeht. Du bist derselbe erfahrene Dungeon Master, aber in dieser kurzen Setup-Phase geht es nicht ums eigentliche Abenteuer, sondern nur darum, die Eckdaten zu klären.
+
+Ablauf
+Stelle dem Spieler nacheinander (eine Frage nach der anderen, nicht alle auf einmal) folgende drei Fragen, bis du zu allen dreien eine Antwort hast:
+
+1. Welches Genre bzw. welche Welt wünscht er sich (z. B. High Fantasy, düster, humorvoll, Horror, Piraten, eine eigene Idee)?
+2. Wie lang soll das Spiel werden — ein einzelnes One-Shot-Abenteuer oder eine längere Kampagne über mehrere Sitzungen?
+3. Wie ist sein Erfahrungsstand mit D&D — komplette(r) Anfänger(in), gelegentlich gespielt, oder erfahrene(r) Regelkenner(in)?
+
+Sobald du alle drei Antworten hast, rufe das Werkzeug propose_game_setup auf mit:
+- einem passenden, einprägsamen Namen für das Spiel
+- einer kurzen Beschreibung (Genre und Welt, optional ein Hinweis auf Umfang und Erfahrungsstand)
+
+Der Spieler sieht deinen Vorschlag danach in einem Formular und kann Name und Beschreibung noch selbst anpassen, bevor er das Spiel erstellt.
+
+Ton
+Bleib locker, freundlich und kurz angebunden — das ist nur die Einrichtung, kein Rollenspiel. Sprich den Spieler per "Du" an.
+
+Sprache
+Antworte in der Sprache, in der der Spieler schreibt.

backend/app/llm/tools/game_setup.py

@@ -0,0 +1,22 @@
+TOOL_SCHEMA = {
+    "name": "propose_game_setup",
+    "description": (
+        "Call this once you know the desired genre/world, the intended length (one-shot vs. "
+        "campaign), and the player's experience level. Propose a fitting name and a short "
+        "description for the new game — the player can still edit both before creating it."
+    ),
+    "parameters": {
+        "type": "object",
+        "properties": {
+            "name": {
+                "type": "string",
+                "description": "A fitting, evocative name for the game.",
+            },
+            "description": {
+                "type": "string",
+                "description": "Short description covering genre and world/setting.",
+            },
+        },
+        "required": ["name", "description"],
+    },
+}

backend/app/models/__init__.py

@@ -1,6 +1,7 @@
 from app.models.character import Character
 from app.models.game import Game, GameParticipant
 from app.models.message import Message
+from app.models.rulebook_chunk import RulebookChunk
 from app.models.user import User
 
-__all__ = ["User", "Game", "GameParticipant", "Character", "Message"]
+__all__ = ["User", "Game", "GameParticipant", "Character", "Message", "RulebookChunk"]

backend/app/models/rulebook_chunk.py

@@ -0,0 +1,23 @@
+import uuid
+
+from pgvector.sqlalchemy import Vector
+from sqlalchemy import Integer, String, Text
+from sqlalchemy.dialects.postgresql import JSONB, UUID
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.db import Base
+
+EMBEDDING_DIM = 384
+
+
+class RulebookChunk(Base):
+    __tablename__ = "rulebook_chunks"
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), primary_key=True, default=uuid.uuid4
+    )
+    source_document: Mapped[str] = mapped_column(String(length=200), nullable=False, index=True)
+    chunk_index: Mapped[int] = mapped_column(Integer, nullable=False)
+    content: Mapped[str] = mapped_column(Text, nullable=False)
+    embedding: Mapped[list[float]] = mapped_column(Vector(EMBEDDING_DIM), nullable=False)
+    doc_metadata: Mapped[dict] = mapped_column(JSONB, nullable=False, default=dict)

backend/app/rag/chunking.py

@@ -0,0 +1,33 @@
+import re
+
+# Rough word-count targets standing in for the 300-800 token / 10-20% overlap guideline —
+# English prose runs ~0.75 words per token, so ~380 words ≈ 500 tokens.
+WORDS_PER_CHUNK = 380
+OVERLAP_WORDS = 60
+
+_WHITESPACE_RE = re.compile(r"[ \t]+")
+_BLANK_LINES_RE = re.compile(r"\n{3,}")
+
+
+def _normalize(text: str) -> str:
+    text = _WHITESPACE_RE.sub(" ", text)
+    text = _BLANK_LINES_RE.sub("\n\n", text)
+    return text.strip()
+
+
+def chunk_text(
+    text: str, words_per_chunk: int = WORDS_PER_CHUNK, overlap_words: int = OVERLAP_WORDS
+) -> list[str]:
+    words = _normalize(text).split()
+    if not words:
+        return []
+
+    step = words_per_chunk - overlap_words
+    chunks = []
+    start = 0
+    while start < len(words):
+        chunks.append(" ".join(words[start : start + words_per_chunk]))
+        if start + words_per_chunk >= len(words):
+            break
+        start += step
+    return chunks

backend/app/rag/embeddings.py

@@ -0,0 +1,22 @@
+from functools import lru_cache
+
+from sentence_transformers import SentenceTransformer
+
+# Multilingual so German player messages retrieve relevant chunks from the
+# English-language rulebooks. 384-dim output, matching RulebookChunk.embedding.
+MODEL_NAME = "paraphrase-multilingual-MiniLM-L12-v2"
+
+
+@lru_cache
+def get_embedding_model() -> SentenceTransformer:
+    return SentenceTransformer(MODEL_NAME)
+
+
+def embed_texts(texts: list[str]) -> list[list[float]]:
+    model = get_embedding_model()
+    embeddings = model.encode(texts, normalize_embeddings=True, show_progress_bar=False)
+    return embeddings.tolist()
+
+
+def embed_query(text: str) -> list[float]:
+    return embed_texts([text])[0]

backend/app/rag/retrieval.py

@@ -0,0 +1,51 @@
+import asyncio
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.rulebook_chunk import RulebookChunk
+from app.rag.embeddings import embed_query
+
+DEFAULT_TOP_K = 5
+# Cosine distance cutoff (0 = identical, 2 = opposite) — drop weak matches rather than
+# stuffing the prompt with irrelevant rulebook text when nothing actually fits the query.
+# Calibrated against test queries: genuinely relevant chunks scored 0.30-0.45.
+MAX_DISTANCE = 0.6
+# Hard cap on injected rulebook text so one turn's context/cost doesn't balloon even when
+# several chunks all clear the relevance threshold.
+MAX_BLOCK_CHARS = 4000
+
+
+async def retrieve_relevant_chunks(
+    session: AsyncSession, query: str, top_k: int = DEFAULT_TOP_K
+) -> list[tuple[RulebookChunk, float]]:
+    # embed_query is a synchronous, CPU-bound sentence-transformers call — run it off the
+    # event loop so it doesn't stall other concurrent requests/WebSocket connections.
+    query_embedding = await asyncio.to_thread(embed_query, query)
+    distance = RulebookChunk.embedding.cosine_distance(query_embedding)
+
+    rows = (
+        await session.execute(
+            select(RulebookChunk, distance.label("distance")).order_by(distance).limit(top_k)
+        )
+    ).all()
+    return [(row[0], row[1]) for row in rows]
+
+
+async def build_rag_block(session: AsyncSession, query: str, top_k: int = DEFAULT_TOP_K) -> str:
+    results = await retrieve_relevant_chunks(session, query, top_k=top_k)
+    relevant = [chunk for chunk, distance in results if distance <= MAX_DISTANCE]
+    if not relevant:
+        return ""
+
+    parts = [
+        "Relevante Auszüge aus den Regelwerken — richte dich danach und nenne bei Bedarf die Quelle:"
+    ]
+    used_chars = 0
+    for chunk in relevant:
+        entry = f"\n[{chunk.source_document}]\n{chunk.content}"
+        if used_chars + len(entry) > MAX_BLOCK_CHARS and used_chars > 0:
+            break
+        parts.append(entry)
+        used_chars += len(entry)
+    return "\n".join(parts)

backend/app/schemas/game_setup.py

@@ -0,0 +1,16 @@
+from pydantic import BaseModel
+
+
+class GameSetupChatRequest(BaseModel):
+    messages: list[dict] = []
+
+
+class GameSetupProposal(BaseModel):
+    name: str
+    description: str
+
+
+class GameSetupChatResponse(BaseModel):
+    messages: list[dict]
+    assistant_text: str | None
+    proposal: GameSetupProposal | None