Reject invalid dated balances on account creation

tests/test_import_current_balance_authority.py

@@ -101,6 +101,55 @@ def test_empty_balance_with_basis_date_is_rejected_without_mutation_before_impor
     assert {(item["basis_date"], item["amount"]) for item in valuations} == {("2026-06-30", 900)}
 
 
+def test_create_rejects_whitespace_or_non_integer_dated_balance_without_mutation(tmp_path):
+    path = str(tmp_path / "ledger.sqlite3")
+    baseline = service.create_ledger_account("baseline", db_path=path)
+    before = service.list_ledger_accounts(active_only=False, db_path=path)["accounts"]
+    before_valuations = service.list_account_valuations(baseline["account"]["id"], db_path=path)["valuations"]
+
+    for invalid_balance in (" ", "not-an-integer", True, False, 1.2, -1.2):
+        rejected = service.create_ledger_account(
+            "invalid",
+            last_balance=invalid_balance,
+            last_balance_basis_date="2026-07-01",
+            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"] == before
+        assert service.list_account_valuations(baseline["account"]["id"], db_path=path)["valuations"] == before_valuations
+
+
+def test_zero_dated_balance_and_valid_import_recovery(tmp_path, monkeypatch):
+    path = str(tmp_path / "ledger.sqlite3")
+    zero = service.create_ledger_account(
+        "zero",
+        last_balance=0,
+        last_balance_basis_date="2026-06-01",
+        db_path=path,
+    )
+
+    assert zero["success"] is True
+    assert zero["account"]["last_balance"] == 0
+    assert [(item["basis_date"], item["amount"]) for item in service.list_account_valuations(zero["account"]["id"], db_path=path)["valuations"]] == [("2026-06-01", 0)]
+
+    account = service.create_ledger_account("recoverable", db_path=path)["account"]["id"]
+    monkeypatch.setattr(
+        imports_service,
+        "parse_kb_bank_pdf",
+        lambda *_: _parsed(_transaction("2026-06-30", 900, 1), "hash-valid"),
+    )
+    monkeypatch.setattr(imports_service, "now_iso", lambda: "2026-07-02T09:00:00")
+
+    imported = imports_service.import_kb_bank_pdf("synthetic", "pw", account_id=account, db_path=path)
+
+    current = next(item for item in service.list_ledger_accounts(active_only=False, db_path=path)["accounts"] if item["id"] == account)
+    assert imported["success"] is True
+    assert current["last_balance"] == 900
+    assert current["last_balance_basis_date"] == "2026-06-30"
+
+
 def test_account_write_sync_timestamp_does_not_infer_balance_basis_or_candidate(tmp_path):
     path = str(tmp_path / "ledger.sqlite3")
     unknown = service.create_ledger_account(