Key Points: Supply chain is a governing constraint, not a checkbox: a weak supply chain thread score sets the ceiling for your entire MRL — you cannot advance past your lowest-scoring thread, no matter how strong the rest of your assessment is. MRL criteria embed supply chain requirements explicitly: from MRL 3 through MRL 9, each gate assesses whether your supplier base can actually support production — not just whether your design can. Supplier count is a measurable risk variable: every additional vendor in your supply chain is a schedule dependency, a quality variable, and a communication overhead. Vertical integration directly satisfies MRL evaluation criteria: a partner who controls material selection, converting, machining, and dispensing under one roof reduces the number of open supplier relationships that auditors assess. Early partner selection is an MRL strategy: qualifying a vertically integrated partner at MRL 4–5 pays dividends at every subsequent gate and prevents the costly requalification that hits programs at MRL 7–8. Why Supply Chain Risk Controls Your MRL Score Manufacturing Readiness Levels exist because good designs fail in production all the time. The MRL framework — formalized in guidance published by the Joint Defense Manufacturing Technology Panel — was built to evaluate whether a program's manufacturing approach can actually support the mission, not just pass a design review.