Function mutation_contract_errors 

pub fn mutation_contract_errors() -> u64

How many writes this process refused as a mutation contract error — an off-contract or ambiguous entity_type stamp, on either outcome (rulings AA 1, AG 3) — each rolled back.

Exported by the server as fraiseql_mutation_contract_errors_total (ruling AJ 3): a contract error is a bug in a mutation function, and this is where operators see it happen. Aggregate on purpose; the per-operation error counter names the operation.