The question every security team asks is what leaves the building. Our default answer is: less than you would expect, and nothing you have not approved.
Redaction happens at the gateway before any external call. Named entities, identifiers, account numbers, health information and anything else in your classification policy are replaced with reversible tokens; the model works on tokenised text and the response is rehydrated on return. For a large class of tasks — summarisation, drafting, classification, extraction of structure rather than identity — the model does not need the real values at all, and this is invisible in output quality.
Data classification then drives model selection. Public and internal data may go to a frontier hosted model; restricted data goes only to an approved zero-retention enterprise endpoint; the most sensitive classes go only to a model hosted inside your own VPC. That policy lives in one place and is enforced by the gateway rather than trusted to each integration.
Warehouse-native AI is the strongest pattern where it applies. Running inference inside Snowflake or BigQuery means the data never moves and no new security boundary is created — which frequently converts a three-month security review into a one-week one, and is worth choosing on that basis alone.
Everything is logged: who asked, what was sent after redaction, which model answered, what came back, and what it cost. That record is what makes governance answerable and, in our experience, is what converts a sceptical security function into a supportive one.