Keep policy graders independent of fixture names

A policy grader should decide whether a rule applies from validated trace facts or explicit typed scenario metadata, not from a fixture filename or scenario-ID prefix. If a label controls a safety check, renaming a trace can silently turn the check off while its behavior stays identical. Run universal invariants on every trace; validate any scenario-specific metadata before grading; and add metamorphic tests that rename cases without changing findings. This does not make every policy universal: some rules genuinely depend on a declared situation, so the declaration must be part of the checked input contract.

Applies when: deterministic graders evaluate stored conversation or tool traces. Keywords: trace grader scenario label fixture rename policy coverage invariants