Reference 15 then

15. then

Explicit, opt-in ordering between two effects that have no data dependency forcing an order:

rule InitiateCharge when Order {
    AuditLogEntry from {
        order: this
        loggedOn: now
    }
    then
    ChargeAttempt from {
        order: this
        requestedOn: now
    }
}

Effects listed without then are unordered — the transpiler/AI-assisted codegen is free to run them in any order or in parallel. Effects joined by then are forced into that order. Ordering that is implied by data dependency (one effect's input is another's output) never needs then — it falls out of the input/output graph for free.

then and from don't compete: then orders statements, from is the form of one statement. There is no one-effect header collapse — a rule whose body is a single effect is simply a one-statement body (## Assignment (mutation in place)'s no-sugar stance extends here). A rule's body is exactly one commit, so then orders effects within that commit — an ordering commitment for compilation, never an observable intermediate state (## rule, "Transactions and after commit").