Preserve sibling inheritance in configuration history and explanations

internal/engine/history.go

@@ -6,6 +6,40 @@ import (
 
 const historyNodeLimit = 4_000_000
 
+type retainedNodeCounter struct {
+	seen  map[*document.Node]bool
+	count int
+	limit int
+}
+
+func newRetainedNodeCounter(limit int) *retainedNodeCounter {
+	return &retainedNodeCounter{seen: make(map[*document.Node]bool), limit: limit}
+}
+
+func (c *retainedNodeCounter) add(root *document.Node) bool {
+	if c == nil {
+		return true
+	}
+	stack := []*document.Node{root}
+	for len(stack) != 0 {
+		node := stack[len(stack)-1]
+		stack = stack[:len(stack)-1]
+		if node == nil || c.seen[node] {
+			continue
+		}
+		c.seen[node] = true
+		c.count++
+		if c.limit >= 0 && c.count > c.limit {
+			return false
+		}
+		for _, entry := range node.Mapping {
+			stack = append(stack, entry.Value)
+		}
+		stack = append(stack, node.Sequence...)
+	}
+	return true
+}
+
 // History applications borrow immutable policy-validated input trees. Metadata
 // records answer presence and origin queries; replay reconstructs value changes.
 // Replay reconciles with canonical decoding before domain resolution so both
@@ -230,11 +264,11 @@ func replaceHistoryPath(root **document.Node, path Path, replacement *document.N
 	}
 }
 
-func historyNodesWithinLimit(baseline, input, final *document.Node, applications []historyApplication, resolutions []resolutionSnapshot) bool {
-	return historyNodesWithin(historyNodeLimit, baseline, input, final, applications, resolutions)
+func historyNodesWithinLimit(baseline, input, final *document.Node, applications []historyApplication, resolutions []resolutionSnapshot, inherited ...*inheritanceScope) bool {
+	return historyNodesWithin(historyNodeLimit, baseline, input, final, applications, resolutions, inherited...)
 }
 
-func historyNodesWithin(limit int, baseline, input, final *document.Node, applications []historyApplication, resolutions []resolutionSnapshot) bool {
+func historyNodesWithin(limit int, baseline, input, final *document.Node, applications []historyApplication, resolutions []resolutionSnapshot, inherited ...*inheritanceScope) bool {
 	seen := make(map[*document.Node]bool)
 	count := 0
 	var visit func(*document.Node) bool
@@ -272,5 +306,23 @@ func historyNodesWithin(limit int, baseline, input, final *document.Node, applic
 			return false
 		}
 	}
+	for _, expansion := range inherited {
+		if expansion == nil {
+			continue
+		}
+		if !visit(expansion.root) {
+			return false
+		}
+		for _, operation := range expansion.operations {
+			if !visit(operation.parent) || !visit(operation.effective) {
+				return false
+			}
+		}
+		for _, replacement := range expansion.replacements {
+			if !visit(replacement.before) || !visit(replacement.after) {
+				return false
+			}
+		}
+	}
 	return true
 }