Registering a guardrail is a control-plane write; the data-plane worker that
serves /chat/completions only picks it up on its next periodic DB sync (~30s), so
the first call after the create ran against a worker with no guardrail and passed
the raw email straight through. The tests asserted on that first call, so they
read in-flight propagation as a PII leak.
Confirmed directly against a live proxy: the same call is unmasked at t=0s and
masked at t=8s, and the presidio analyzer itself correctly returns EMAIL_ADDRESS
with score 1.0 the whole time. The MCP guardrail suite already documents and
waits out this exact sync delay; presidio never got the same treatment.
Poll the call until the placeholder replaces the PII, so the assertions judge the
synced state. A guardrail that never masks still fails, on the last unmasked
content. pre_call and post_call now pass repeatably.
Refs LIT-4821
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