190. Mutation testing is scheduled evidence over declared critical predicates, never a gate on every change
Context
Coverage proves a line ran, not that a test would fail if it were wrong (docs/COVERAGE.md). The owner asked for mutation testing several times, and the CI pool judges one pull request at a time.
Decision
Critical predicates are declared once in .ai/repo/ci. A scheduled or offloaded mutation run records its survivors in the ledger, and they are published. A survivor is a finding with an owner, never a red pull request.
Alternatives rejected
- A blocking mutation-score gate per pull request (CI cost)
- Mutation over the whole crate
Consequences
Mutation evidence is periodic and revision-stamped; claims about adversarial strength cite it.
Sources
Promoted on 2026-10-18 from the owner's ChatGPT project (workspace chatgpt-majordomus, issue I3100). The owner has not accepted it; it is proposed for the owner's decision.
chatgpt-majordomus:c113#16chatgpt-majordomus:c139#5chatgpt-majordomus:c158#10chatgpt-majordomus:c158#20chatgpt-majordomus:c293#2