Permission system

A permission is a contract that answers one question: is this call allowed? The kernel asks it on every dispatch and respects the answer. Everything Sail can do — every venue, every bound, every strategy constraint — is expressed as a permission. This is where you build.

This section covers:

• IPermission & Context — the interface every permission implements, reproduced from source, field by field.
• Full expressiveness — why permissions are arbitrary Solidity rather than a constraint grammar, and what that buys.
• Shared multi-tenant templates — example implementations of the pattern: one deployment, per-account config, the opaque params blob, and the starter catalog. Reference examples, not drop-in production contracts.
• Permission lifecycle — registration, configuration, replacement, revocation, and manager rotation — each tied to the EIP-712 operation that authorizes it.
• Extension interfaces — optional introspection and agent-identity conventions for tooling.

The mental model

Permission Signer ── registers ──▶ permission address joins the account's mandate
Manager ── dispatch names it ────▶ kernel staticcalls evaluate(txData, ctx)
evaluate returns true ───────────▶ Safe executes · false/revert/OOG ─▶ dispatch reverts

The kernel never inspects what a permission checks. It guarantees the four evaluation properties — static, gas-capped, selective, fail-closed — and leaves the meaning entirely to the permission author. Adding a new DeFi venue is therefore a contract deployment, not a protocol upgrade.