diff --git a/docs/roadmap/implementation.md b/docs/roadmap/implementation.md
index a009636..a309832 100644
--- a/docs/roadmap/implementation.md
+++ b/docs/roadmap/implementation.md
@@ -245,7 +245,7 @@ Validate: `go test ./internal/engine -run 'Resolution|Metadata|Provenance|Histor
 engine race tests, and the everyday check. Complexity is output-sensitive to
 affected events, not every delta times every field.
 
-## Stage 9: Collect sensitivity directly from trees
+## Stage 9: Collect sensitivity directly from trees — Complete
 
 Roadmap candidate 5. Owner: engine `secret.go`. Keep fixed-point propagation
 unchanged until Stage 11 so collection is independently reviewable.
diff --git a/internal/engine/secret.go b/internal/engine/secret.go
index b91795f..7490fa3 100644
--- a/internal/engine/secret.go
+++ b/internal/engine/secret.go
@@ -9,17 +9,10 @@ type secretDependency struct {
 
 func classifySecretPaths(schema *schemaDescriptor, predicate func(Path) bool, metadata Metadata, final *document.Node, applications []historyApplication, projections ...*document.Node) map[string]bool {
 	paths := make(map[string]Path)
-	finalPaths := make(map[string]*document.Node)
-	indexDocument(final, Path{}, finalPaths)
-	for pointer := range finalPaths {
-		addSecretPath(paths, pointer)
-	}
 	for _, application := range applications {
-		applicationPaths := make(map[string]*document.Node)
-		indexDocument(application.value, application.path, applicationPaths)
-		for pointer := range applicationPaths {
-			addSecretPath(paths, pointer)
-		}
+		walkDocument(application.value, application.path, func(path Path, _ *document.Node) {
+			addSecretPath(paths, path.String())
+		})
 	}
 	var dependencies []secretDependency
 	for pointer, history := range metadata.history {
@@ -65,16 +58,19 @@ func classifySecretPaths(schema *schemaDescriptor, predicate func(Path) bool, me
 	}
 
 	secret := make(map[string]bool)
-	for _, tree := range append(projections, final) {
-		projected := make(map[string]*document.Node)
-		indexDocument(tree, Path{}, projected)
-		for pointer, node := range projected {
+	classifyProjection := func(tree *document.Node) {
+		walkDocument(tree, Path{}, func(path Path, node *document.Node) {
+			pointer := path.String()
 			addSecretPath(paths, pointer)
 			if node.Sensitive {
 				secret[pointer] = true
 			}
-		}
+		})
 	}
+	for _, tree := range projections {
+		classifyProjection(tree)
+	}
+	classifyProjection(final)
 	for pointer, path := range paths {
 		if root, ok := schemaSecretRoot(schema, path); ok {
 			secret[root.String()] = true
diff --git a/internal/engine/secret_classification_test.go b/internal/engine/secret_classification_test.go
new file mode 100644
index 0000000..6b2502f
--- /dev/null
+++ b/internal/engine/secret_classification_test.go
@@ -0,0 +1,23 @@
+package engine
+
+import "testing"
+
+func TestSecretPredicateReceivesDetachedHistoricalPath(t *testing.T) {
+	path := Keys("records").Key("1")
+	metadata := Metadata{history: map[string][]Change{
+		path.String(): {{Path: path}},
+	}}
+	seen := false
+	classified := classifySecretPaths(nil, func(candidate Path) bool {
+		if candidate.String() != path.String() {
+			return false
+		}
+		seen = true
+		candidate.segments[0].key = "changed"
+		return true
+	}, metadata, nil, nil)
+
+	if !seen || !classified[path.String()] || classified["/changed/1"] {
+		t.Fatalf("classification after predicate mutation = %#v, predicate called: %v", classified, seen)
+	}
+}