diff --git a/internal/brain/tier3/brain.go b/internal/brain/tier3/brain.go
new file mode 100644
index 000000000..523bb438e
--- /dev/null
+++ b/internal/brain/tier3/brain.go
@@ -0,0 +1,14 @@
+package tier3
+
+import "fmt"
+
+// Tier3Brain provides high-level cognitive security analysis for autonomous agents.
+type Tier3Brain struct {
+	FleetID string
+}
+
+func (b *Tier3Brain) AnalyzeThreat(threatData string) string {
+	fmt.Printf("Analyzing threat for fleet %s: %s\n", b.FleetID, threatData)
+	// Tier-3 reasoning for complex attack vectors
+	return "Mitigation Strategy: Isolation"
+}