Alpha faucet — grant a 7-day Storyflo+ trial in exchange for one "claim" per listener per UTC day. The actual on-chain USDC transfer on Base Sepolia is queued; the tier flip happens immediately so the listener sees premium voices on their next render.

Idempotent on (listener_token, claim_day) — duplicate clicks return the existing claim row's expires_at rather than minting a new grant. ip_hash is captured for abuse triage but is not a primary uniqueness key (a household sharing IP shouldn't block legitimate claims from different listener_tokens).