constraint

A constraint is a rule Fishhawk checks against the real output of a stage. It is not advice given to the agent — it is a check run afterwards, against the diff, by code the agent does not execute.

constraints:
  - max_files_changed: 45
  - forbidden_paths: [".github/workflows/**", ".fishhawk/**"]
  - required_outcomes: [tests_added_or_updated, ci_green]

max_files_changed bounds the blast radius. A change that grew past its approved scope fails rather than landing.
forbidden_paths are glob patterns the stage may not write. The check is on the committed diff, so an agent that edits a forbidden file has failed the stage whatever it says in its summary.
required_outcomes are conditions the result must satisfy — tests were added or updated, CI is green.

Why the distinction from a gate matters

A gate asks a person. A constraint asks the diff. An agent can write a persuasive explanation of why it needed to touch a forbidden path; it cannot make the path check return true. When you are deciding how much autonomy to grant, the question worth asking is which of your rules are gates — persuadable — and which are constraints.

Scope

The plan’s declared file scope acts as a constraint too. A file the agent edits without declaring is dropped from the commit; a file it creates without declaring fails the stage. Widening the scope mid-stage is a request that goes back to the operator, not a decision the agent makes.

plan — where the declared scope comes from.