The pure mapping from Statifier.Effect.t() (and the session's own lifecycle messages) to StatifierUI.Trace.Message.t(), matching docs/wire-format.md field for field. No process, no session, no %Statifier.Machine{} - the whole vocabulary is testable from a struct literal.

Value handling

Anything from the engine that occupies a value position - Event.data, Log.value, Trace.Done.donedata, Effect.Done.donedata, Send.data, SendDelayed.data, Invoke.params, Invoke.content, DatamodelChange.new_value, DatamodelChange.prior_value - goes through StatifierUI.Value.encode/1; its {:error, _} is propagated, never rescued. Everything structural is reduced first (decision 6): MapSets to sorted lists (configuration/1), atoms to "kind"-tagged objects (origin/1, owner/1). This ordering matters - StatifierUI.Value.encode/1 rejects any term outside predicator's closed value domain with {:error, {:unsupported_value, term}}, so handing it a raw tuple or a bare atom would produce a wrong error (:unsupported_value instead of a normalizer-specific one) rather than the structural, purpose-built handling this module gives those shapes.

Absence

_event.data keeps ADR-0005's three-way rule unchanged: :undefined omits the key, nil is present as JSON null, %{} is present as {} (put_defined/3). DatamodelChange.new_value and DatamodelChange.prior_value follow the same three-way rule, because they share _event.data's property: the engine spells "unbound" as :undefined there (ADR-0037), so nil genuinely means a stored null. Every other nullable field in this vocabulary has no engine-side way to distinguish "no value" from "a genuinely null value" - Statifier.Effect.Log.value and the two donedata fields default to plain nil for "nothing here", never :undefined - so put_present/3 and put_value/3 generalize the rule (decision 5) by treating nil and :undefined alike as absence for those fields, applied uniformly instead of remembered clause by clause.