Salesforce Winter '27 adds FORMULA() for arithmetic and field-to-field comparisons in a SOQL WHERE clause, without a formula field or post-processing. The beta requires API version 68.0 or later and supports sandbox, Developer Edition, and scratch orgs only. It is not available in production.
Test one comparison that currently relies on a formula field or post-processing. Compare the returned record membership with the existing implementation, not just record counts. Record any differences from the baseline.