Cloud Security Posture Management (CSPM) systems detect known vulnerabilities by maintaining a rule set, distributing it to customers, and evaluating it against periodically-collected asset inventories. To our knowledge, in publicly documented architectures the rule set is environment-agnostic and curated centrally by the vendor; updates are batched into release cycles and shipped on a cadence ranging from hours to days depending on detection severity. The disclosure-to-protection window -- from a CVE being published to the customer's system being capable of detecting affected assets -- is therefore bounded by the vendor's release cadence for version-match detections, and by additional human authoring time for richer detections incorporating configuration predicates beyond the affected-software string. We propose an architecture in which the rule set is not vendor-distributed but continuously derived, within the customer's tenant, from the intersection of public catalogue feeds and the live asset graph. A rule comes into existence when a catalogue entry and an applicable asset are simultaneously present, and goes out of existence when either input ceases to support it. Derivation is bidirectional: new catalogue entries and new assets both trigger it. It incorporates the full structured-field content of catalogue entries, not only the affected-software predicate. The live rule set is bounded by environment diversity rather than catalogue breadth. Prior systems incrementally evaluate a static rule set; we incrementally derive the rule set itself. We present the threat model, the architecture, formal semantics with an equivalence theorem, complexity analysis, a worked example, and an evaluation methodology. The contribution is the architectural shift and its latency and resource consequences; rule correctness and alert prioritization are out of scope.