Arbitrum Sepolia primary, Robinhood Chain when the SDK ships

Context

Earlier drafts claimed "dual-primary deployment from Day 1." A 2026-05-18 search confirmed no public Robinhood Chain SDK or contracts repo.

Decision

Arbitrum Sepolia is the actual primary. The RH-Chain adapter ships within 14 days after Robinhood publishes an SDK.

Alternatives

Wait for RH (rejected: cannot ship Year-1 on a chain with no SDK). Bet entirely on RH (rejected: same).

Consequences

The dual-primary claim is demoted to an honest conditional.