Stylus over pure Solidity for compute-heavy contracts (Plinth, Vigil, Coffer, Sigil)

Context

SPAN margin computation is a nested loop. The Solidity equivalent is estimated at 10 to 100x more gas per the Arbitrum docs.

Decision

Plinth + Vigil + Coffer + Sigil in Rust + Stylus. Adapters, registries, and governance in Solidity.

Alternatives

All-Solidity (rejected: violates the gas goal). All-Stylus (rejected: the adapter ecosystem is Solidity-native; integration friction).

Consequences

The team must master both Rust and Solidity. The build pipeline is more complex (cargo stylus + Foundry). Worth it for the compute moat.