diff --git a/backend/app/__init__.py b/backend/app/__init__.py
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Binary files /dev/null and b/backend/app/__init__.py differ
diff --git a/backend/app/main.py b/backend/app/main.py
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+++ b/backend/app/main.py
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+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+from pydantic import BaseModel
+from typing import Any, Dict, List, Optional
+
+
+class Answer(BaseModel):
+    question_code: str
+    value: Any
+
+
+class SessionCreate(BaseModel):
+    language: str
+    answers: List[Answer]
+
+
+class MtsPreparation(BaseModel):
+    session_id: str
+    proposed_presenting_flowchart: Optional[str] = None
+    red_flag_indicators: List[str] = []
+    suggested_priority_level: Optional[str] = None
+
+
+app = FastAPI(title="Triage-Fragen API", version="0.1.0")
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+
+@app.get("/health")
+async def health() -> Dict[str, str]:
+    return {"status": "ok"}
+
+
+@app.post("/sessions", response_model=MtsPreparation)
+async def create_session(payload: SessionCreate) -> MtsPreparation:
+    session_id = "dummy-session-id"
+
+    flowchart: Optional[str] = None
+    red_flags: List[str] = []
+    priority: Optional[str] = None
+
+    for ans in payload.answers:
+        if ans.question_code == "chief_complaint" and ans.value == "chest_pain":
+            flowchart = "CHEST_PAIN"
+        if ans.question_code == "breathlessness" and ans.value is True:
+            red_flags.append("breathlessness")
+        if ans.question_code == "pain_intensity" and isinstance(ans.value, int) and ans.value >= 8:
+            red_flags.append("severe_pain")
+
+    if "breathlessness" in red_flags:
+        priority = "RED_OR_ORANGE"
+
+    return MtsPreparation(
+        session_id=session_id,
+        proposed_presenting_flowchart=flowchart,
+        red_flag_indicators=red_flags,
+        suggested_priority_level=priority,
+    )