feat: auto-update fall_id when KVNR is entered on a case

When a KVNR is entered on a case that has a random-suffix or legacy
Nachname-based fall_id, the fall_id is automatically rebuilt using
the new KVNR.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/api/cases.py

@@ -24,6 +24,7 @@ from app.schemas.case import (
 from app.schemas.disclosure import DisclosureRequestCreate, DisclosureRequestResponse
 from app.config import get_settings
 from app.services.audit_service import log_action
+from app.services.import_service import has_random_suffix
 from app.services.disclosure_service import (
     create_disclosure_request, has_active_disclosure, has_pending_request,
 )
@@ -433,6 +434,12 @@ def set_case_kvnr(
     old_kvnr = case.kvnr
     new_kvnr = payload.get("kvnr")
     case.kvnr = new_kvnr
+
+    # Auto-update fall_id if it currently has a non-KVNR suffix
+    old_fall_id = case.fall_id
+    if new_kvnr and case.fall_id and has_random_suffix(case.fall_id):
+        case.fall_id = f"{case.jahr}-{case.kw:02d}-{case.fallgruppe}-{new_kvnr}"
+
     case.updated_by = user.id
     db.commit()
     db.refresh(case)
@@ -443,8 +450,8 @@ def set_case_kvnr(
         action="kvnr_updated",
         entity_type="case",
         entity_id=case.id,
-        old_values={"kvnr": old_kvnr},
-        new_values={"kvnr": new_kvnr},
+        old_values={"kvnr": old_kvnr, "fall_id": old_fall_id},
+        new_values={"kvnr": new_kvnr, "fall_id": case.fall_id},
         ip_address=request.client.host if request.client else None,
         user_agent=request.headers.get("user-agent"),
     )

backend/app/services/import_service.py

@@ -9,6 +9,7 @@ Handles:
 
 import logging
 import random
+import re
 import string
 
 from sqlalchemy.orm import Session
@@ -41,6 +42,28 @@ def generate_fall_id(parsed: ParsedCase) -> str:
     return f"{parsed.jahr}-{parsed.kw:02d}-{parsed.fallgruppe}-{suffix}"
 
 
+# KVNR format: letter followed by 9 digits (e.g. A123456789)
+KVNR_PATTERN = re.compile(r'^[A-Z]\d{9}$')
+
+
+def has_random_suffix(fall_id: str | None) -> bool:
+    """Check if a fall_id ends with a non-KVNR suffix.
+
+    Returns True for random suffixes (6-char alphanumeric) and legacy
+    Nachname-based suffixes. Returns False for KVNR suffixes.
+    """
+    if not fall_id:
+        return False
+    parts = fall_id.rsplit("-", 1)
+    if len(parts) < 2:
+        return False
+    suffix = parts[1]
+    # If it matches KVNR pattern, it's NOT a random suffix
+    if KVNR_PATTERN.match(suffix):
+        return False
+    return True
+
+
 def check_duplicate(db: Session, parsed: ParsedCase) -> bool:
     """Check if a case already exists in the database.
 

backend/tests/test_import.py

@@ -17,6 +17,7 @@ from app.services.import_service import (
     confirm_import,
     generate_fall_id,
     generate_random_suffix,
+    has_random_suffix,
     preview_import,
 )
 
@@ -354,3 +355,25 @@ class TestPreviewImportMocked:
         assert result.rows[0].row_number == 1
         assert result.rows[1].row_number == 2
         assert result.rows[2].row_number == 3
+
+
+# ── has_random_suffix tests ───────────────────────────────────────────
+
+
+class TestHasRandomSuffix:
+    def test_kvnr_suffix(self):
+        """Fall_id with KVNR is NOT random."""
+        assert has_random_suffix("2026-06-onko-A123456789") is False
+
+    def test_random_suffix(self):
+        """Fall_id with 6-char random suffix IS random."""
+        assert has_random_suffix("2026-06-onko-X7K9M2") is True
+
+    def test_legacy_nachname_suffix(self):
+        """Fall_id with legacy Nachname suffix IS treated as non-KVNR."""
+        assert has_random_suffix("2020-32-onko-Bartl-Zimmermann") is True
+        assert has_random_suffix("2026-06-kardio-Tonn") is True
+
+    def test_empty_fall_id(self):
+        assert has_random_suffix("") is False
+        assert has_random_suffix(None) is False