Screenshot of the "Simulate as user" drawer opened from the Row Security panel. Right-anchored 640 px drawer. Header "Simulate effective rules". Body: email input "alice.north@acme.test"; roles multi-chip input with "region_manager_emea" added; a "Simulate" button. Below the inputs, a result card labelled "Effective predicate for this principal" renders a pretty-printed combined predicate tree with three levels: AND node → role_predicate `dimension_equals('region.region_code', 'EMEA')` (source rule: "EMEA manager scope"), user_mapping `region.region_code IN (SELECT allowed_region FROM demo_data.user_region_map WHERE user_id = 'alice.north@acme.test')` (source rule: "Account-manager assignments"). Next to each leaf is a small pill showing which rule it came from. A footer card reads "Applies to 3 of 4 enabled rules. 1 rule (Self-service view) does not fire — its role is not on this principal." Dimensions: 1280x900px. Purpose: make rule interaction legible before the rules ever run.