The environment logs value-free events

Status: accepted, 2026-10-11. Answers #15's event sink and the plan's D-N17. Serves Honest data and What earns a concept. Reopen a case when an adopter shows the number it needs and cannot derive; reopen the value-free rule never.

Context#

The runtime reported through four hooks: the store's reportMissing, reportUnexpected and reportAmbiguousIdentity, and the environment's requiredFieldMissing, each a closure handed a Record, a Slot or a Value. A production app wanted one place to attach its logging and metrics, and a privacy rule: a hook that hands over a record makes it one line to log a slot's value. The hooks also kept Record, Value, Slot and TypeID public for a mechanism's sake. Relay's environment takes a log function called with each LogEvent.

Decision#

One sink, Environment.log, called with each LogEvent: a value-free enum of names and counts, never a record, a slot, a value, a variable or a response body. The first cases are the fetch (started, completed with its duration, failed with its failure's kind), the commit (its kind and the slots it changed in records that existed), a field error a fetch's response carried that no @catch handled, by operation and response path, the image (opened, unavailable, written with its batches, failed) and missing data (a field read and never fetched, a value a reader's type cannot hold, an id naming records of several types, a @required(action: LOG) field that is null), each by type and field name. The four hooks are gone, not forwarded. Debug builds print the missing-data cases by default, as the hooks did; a release build logs nothing until the app sets log. A case earns its place as a concept does: by an adopter's number that cannot be derived from the cases that exist.

Evidence#

Every event is raised where the runtime already knew the fact: the hooks' four call sites, the two fetch paths, the commit's one door, the image's open and write. A bench row measures a fetch and a commit with a counting log installed, in BENCHMARKS.md.

Not chosen#

• Durations, byte counts, slot counts and notification counts on every event, as #15 drafts them. Each is a measurement the runtime would make for a sink that may be absent; the fetch's duration is kept because the handle times it already. The rest wait for the number an adopter needs.
• Keeping the hooks as forwarders. Two doors to one fact drift, and the hooks' signatures are what kept the record types public.
• A protocol for the sink. A closure is Relay's shape and an app's logger wraps in one line.