Reject invalid balances on account updates

jarca_ledger_mcp/application/accounts_write_services.py

@@ -48,8 +48,15 @@ def update_ledger_account(account_id: str, db_path: str | None = None, **fields:
         if current is None: return fail("not_found", "account not found")
         balance_update = "last_balance" in fields and fields.get("last_balance") is not None
         basis_update = "last_balance_basis_date" in fields and fields.get("last_balance_basis_date") is not None
-        if basis_update and (not balance_update or fields.get("last_balance") == ""):
+        if basis_update and not balance_update:
             return fail("validation_error", "last_balance_basis_date requires last_balance")
+        normalized_balance = None
+        if balance_update:
+            try:
+                from .account_valuation_service import _strict_int
+                normalized_balance = _strict_int(fields["last_balance"], "last_balance", allow_none=False)
+            except (ValueError, TypeError) as e:
+                return fail("validation_error", str(e))
         normalized_basis = None
         if basis_update:
             try:
@@ -64,7 +71,7 @@ def update_ledger_account(account_id: str, db_path: str | None = None, **fields:
                 if k == "statement_status": v = normalize_statement_status(str(v))
                 if k == "liquidity_bucket": v = normalize_liquidity_bucket(str(v))
                 if k == "active": v = int(bool(v))
-                if k == "last_balance" and v != "": v = int(v)
+                if k == "last_balance": v = normalized_balance
                 if k == "currency": v = str(v).upper()
                 if k == "last_balance_basis_date": v = normalized_basis
             except Exception as e: return fail("validation_error", str(e))
@@ -83,7 +90,7 @@ def update_ledger_account(account_id: str, db_path: str | None = None, **fields:
         stored_date = str(current["last_balance_basis_date"] or "")[:10]
         incoming_date = normalized_basis if basis_update else ""
         historical = bool(balance_update and incoming_date and stored_date and incoming_date < stored_date)
-        candidate_balance = fields.get("last_balance", current["last_balance"])
+        candidate_balance = normalized_balance if balance_update else current["last_balance"]
         if historical:
             kept=[(u,p) for u,p in zip(updates,params) if not u.startswith(("last_balance=","last_balance_basis_date=","last_synced_at="))]
             updates=[u for u,_ in kept]; params=[p for _,p in kept]

tests/test_import_current_balance_authority.py

@@ -121,6 +121,78 @@ def test_create_rejects_whitespace_or_non_integer_dated_balance_without_mutation
         assert service.list_account_valuations(baseline["account"]["id"], db_path=path)["valuations"] == before_valuations
 
 
+def test_update_rejects_bool_or_float_dated_balance_without_mutation(tmp_path):
+    path = str(tmp_path / "ledger.sqlite3")
+    account = service.create_ledger_account(
+        "baseline",
+        last_balance=900,
+        last_balance_basis_date="2026-07-01",
+        db_path=path,
+    )["account"]["id"]
+    before = service.list_ledger_accounts(active_only=False, db_path=path)["accounts"][0]
+    before_valuations = service.list_account_valuations(account, db_path=path)["valuations"]
+
+    for invalid_balance in (True, False, 1.2, -1.2):
+        rejected = service.update_ledger_account(
+            account,
+            last_balance=invalid_balance,
+            last_balance_basis_date="2026-07-02",
+            db_path=path,
+        )
+
+        assert rejected["success"] is False
+        assert rejected["error_code"] == "validation_error"
+        assert service.list_ledger_accounts(active_only=False, db_path=path)["accounts"][0] == before
+        assert service.list_account_valuations(account, db_path=path)["valuations"] == before_valuations
+
+
+def test_update_rejects_empty_undated_balance_without_mutation(tmp_path):
+    path = str(tmp_path / "ledger.sqlite3")
+    account = service.create_ledger_account(
+        "baseline",
+        last_balance=900,
+        last_balance_basis_date="2026-07-01",
+        db_path=path,
+    )["account"]["id"]
+    before = service.list_ledger_accounts(active_only=False, db_path=path)["accounts"][0]
+    before_valuations = service.list_account_valuations(account, db_path=path)["valuations"]
+
+    rejected = service.update_ledger_account(account, last_balance="", db_path=path)
+
+    assert rejected["success"] is False
+    assert rejected["error_code"] == "validation_error"
+    assert service.list_ledger_accounts(active_only=False, db_path=path)["accounts"][0] == before
+    assert service.list_account_valuations(account, db_path=path)["valuations"] == before_valuations
+
+
+def test_update_preserves_zero_and_signed_integer_balance_semantics(tmp_path):
+    path = str(tmp_path / "ledger.sqlite3")
+    account = service.create_ledger_account("baseline", db_path=path)["account"]["id"]
+
+    zero = service.update_ledger_account(
+        account,
+        last_balance=" +0 ",
+        last_balance_basis_date="2026-07-01",
+        db_path=path,
+    )
+    signed = service.update_ledger_account(
+        account,
+        last_balance="-12",
+        last_balance_basis_date="2026-07-02",
+        db_path=path,
+    )
+
+    assert zero["success"] is True
+    assert zero["account"]["last_balance"] == 0
+    assert signed["success"] is True
+    assert signed["account"]["last_balance"] == -12
+    assert signed["account"]["last_balance_basis_date"] == "2026-07-02"
+    assert [(item["basis_date"], item["amount"]) for item in service.list_account_valuations(account, db_path=path)["valuations"]] == [
+        ("2026-07-01", 0),
+        ("2026-07-02", -12),
+    ]
+
+
 def test_zero_dated_balance_and_valid_import_recovery(tmp_path, monkeypatch):
     path = str(tmp_path / "ledger.sqlite3")
     zero = service.create_ledger_account(