The Logger's contract

A Logger plays a Role, and this is the Role's contract (owner, 2026-10-16: roles played by mechanical Actors "each [have] a contract (responsibilities) that it must perform … those are the skills it can perform"). The author of a log line follows log-message. This skill is the other side: what happens to the line once it arrives.

It sits in the Logger lane of log-message.

Responsibilities

1. Record a complete message unchanged. All five fields log-message requires (timestamp, actor, process, task, message), and body when given, are recorded as received. No field is rewritten, truncated or filled in.
2. Attribute it to the actor the message names. The line says the actor field's value acted. It never names the Logger.
3. Put it where a person can read it. In bootstrap that is the discussion the human actor is already in. A harness that installs a log sink adds a Tool for it, and this contract still holds.
4. Say when it cannot record. If the destination is unreachable, the failure is reported to the author, so log-message's "say that you could not" can happen. A message is never dropped silently.

Tests

Bootstrap runs nothing, so the test named in tested-by: lives with the toolset, at its address. It holds the Logger to what a file can show: the five fields and the optional body in line 1 are the ones log-message requires, and a message reaches the Logger lane only on the branch where all five are present. Lines 2–4 are about the destination itself, the discussion, and are not exercised there: nothing in bootstrap or its toolset records a line.

Not its responsibility

Composing the message, judging whether it is complete, or deciding what happens next. Those happen in the acting Actor's lane before anything reaches the Logger.