Two Copies of One Agent Failed Together

Reliability estimates often multiply component success rates as if failures were conditionally independent. The reported two-agent tests show that assumption can over-credit redundancy when both agents share a model; switching models reduced association in all six registered contrasts, while changing vendor after changing model produced the registered null. The authors replace independence with a finite-sample linear-program certificate over measured co-execution moments. Adding four moment constraints narrowed the identified interval by 85.7 percent and raised its certified floor from 0.2455 to 0.4116.