`bynk.transition.*` errors

Step invariants — transition <name>: <pred over old/new> — are the invariant predicate widened from a single committed state to the move between two (v0.116). These are their common errors. See the Step invariants reference.

bynk.transition.not_bool

[bynk.transition.not_bool] Error: transition `bad` predicate has type `Int`, but a transition must be `Bool`

Cause: a transition predicate does not evaluate to Bool.

Fix: make it a boolean claim over old/new — a comparison (new.count >= old.count), an implies, an is narrowing, or a pure Bool-returning method.

bynk.transition.impure_predicate

[bynk.transition.impure_predicate] Error: transition `bad` uses an effectful or test-only construct; a step invariant predicate must be pure

Cause: a predicate uses an effect, ? propagation, expect, or Val — a transition is the one predicate surface and must be pure.

Fix: remove the effectful/test-only construct. A predicate may read the old/new state and call pure value methods only.

bynk.transition.no_step_reference

[bynk.transition.no_step_reference] Error: transition `bad` references neither `old` nor `new`, so it constrains a single state, not a step

Cause: a transition predicate mentions neither old nor new, so it is a claim about one committed state, not a move.

Fix: write it as an invariant (which constrains a single committed state), or reference old/new to make it a genuine step claim.

bynk.transition.duplicate_name

[bynk.transition.duplicate_name] Error: agent `Order` declares more than one transition named `t`

Cause: two transitions share a name. The name rides the InvariantViolation failure report, so it must be unique per agent.

Fix: give each transition a distinct name.

bynk.transition.cross_agent_reference

[bynk.transition.cross_agent_reference] Error: transition `bad` references another agent; a step invariant constrains a single agent's own state move

Cause: a predicate references another agent. A transition, like an invariant, constrains one agent’s own reachable states.

Fix: a property that genuinely spans agents belongs in a saga or a scenario, not a transition.

bynk.parse.transition_after_handler

[bynk.parse.transition_after_handler] Error: a `transition` must be declared before the agent's handlers

Cause: a transition appears after an on handler. Step invariants form a phase between the store fields and the handlers, beside the snapshot invariants.

Fix: move the transition above the first handler.