diff --git a/app/core/privacy.py b/app/core/privacy.py
new file mode 100644
index 0000000..4f0087a
--- /dev/null
+++ b/app/core/privacy.py
@@ -0,0 +1,16 @@
+"""PII scrubbing and pseudonymisation (issue #2). Contract stub — implementation lands in #2."""
+
+from app.core.types import ScrubbedText
+
+
+def scrub(text: str) -> ScrubbedText:
+    """Replace personal data (phones, emails, SNILS, names, addresses...) with placeholders."""
+    raise NotImplementedError
+
+
+def pseudo_id(snils: str, key: str | None = None) -> str:
+    """HMAC-SHA256(PSEUDO_KEY, normalised SNILS) as 32 hex chars.
+
+    The token is the only link between the identity and clinical databases.
+    """
+    raise NotImplementedError
diff --git a/app/core/types.py b/app/core/types.py
new file mode 100644
index 0000000..98d43a4
--- /dev/null
+++ b/app/core/types.py
@@ -0,0 +1,27 @@
+"""Shared core types. Frozen contract between zones: change only via a separate small PR."""
+
+from enum import IntEnum
+from typing import NewType
+
+# Text that has passed `app.core.privacy.scrub()`. The LLM gateway accepts only this type (guardrail #1).
+ScrubbedText = NewType("ScrubbedText", str)
+
+
+class RiskLevel(IntEnum):
+    """Safety risk level. Ordered, so the combined signal is `max(lexicon, llm)`."""
+
+    NONE = 0
+    POSSIBLE = 1
+    ACUTE = 2
+
+
+class AlertLevel(IntEnum):
+    """Alert level stored in DB.
+
+    UI colour is derived (ADR-006): ACUTE=red, HIGH/MODERATE=yellow, INFO=grey.
+    """
+
+    INFO = 0
+    MODERATE = 1
+    HIGH = 2
+    ACUTE = 3