Linter

A linter checks code against rules and names each violation with its place. It covers the formatter's check too. Loops can read it on every edit, because it is fast and its messages can tell the agent what to change.

What it sees

Whatever its rules were written to see, and nothing else. Rules can encode more than style: the project's conventions, the boundaries between parts of its architecture, and database migrations that are unsafe to run. A clean run says the code breaks none of the rules. It says nothing about whether the code works.

Reading the signal

• Exit code zero: no rule was broken.
• Non-zero exit code: each violation gives its file:line, the rule's name and a message. The most useful messages teach the fix, so the agent fixes the cause instead of silencing the rule.
• A disable comment without a reason is itself a finding. It hides a violation instead of explaining it.

A linter that stops on a broken configuration or a missing plugin has not checked the code. Its failure says nothing about the work.