Thanks for tackling this - valuable hardening. I tested the change locally and traced the call graph; coverage of the monetary entry points looks broad and consistent. A few observations:

1. Redundant validateAccessRights in repayLoanWithTopup

fromLoanAccount's hierarchy is validated twice - once right after it is assembled, and again after toLoanAccount is assembled. The first call looks like a copy-paste duplicate and can be removed.

2. Scheduled-job paths depend on the system user being head-office

validateAccessRights calls authenticatedUser(), which throws if there is no user. transferFunds(...) is invoked by ExecuteStandingInstructionsTasklet, TransferInterestToSavingsTasklet, TransferFeeChargeForLoansTasklet, and deposit-maturity processing. These run as the system user (office_id=1, hierarchy "."), so the prefix check passes for every account - but this is an implicit invariant. Could we add a short comment documenting that dependency, and/or a smoke test on one job path so a future change to the system user's office doesn't silently break standing instructions?

3. Primary repayment path - confirmed makeLoanRepayment is covered transitively via makeLoanRepaymentWithChargeRefundChargeType, so standard repayments are protected. 👍

Test suggestion: a negative integration test (user scoped to a child/sibling office attempting a transaction on an account in another branch → expect NoAuthorizationException / 403), plus a positive same-hierarchy case, would lock in the intended behaviour.