Replay added configuration paths in explanations

docs/config.md

@@ -162,7 +162,10 @@ parser values. `Present=false` with empty YAML means absence or deletion; explic
 null is present and renders as `null`. The history starts with the canonical typed
 application-default or Go-zero baseline, then includes only relevant base sources in
 traversal order, the selected profile, supplied CLI records, and audited net
-resolution operations. Explicit equal writes remain visible. When input replay
+resolution operations. Overlapping parent/child resolution records are rendered
+as one net subtree event with combined reasons and dependencies, rather than
+pretending that the recorded assignments ran in lexical order. Explicit equal
+writes remain visible. When input replay
 differs from the final typed input, a `ChangeDecoding` event records the transition
 before domain resolution. Its origin retains the decoded path's source/default
 attribution; its reason identifies static-default retention and canonical decoding.

docs/roadmap/remediation.md

@@ -132,6 +132,11 @@ the effective value and origin without implying that a final-present path is abs
 
 ## 5. P2 — Replay newly created resolution paths
 
+Status: complete. Replay inserts new mapping entries/subtrees and coalesces
+overlapping parent/child net operations while retaining reasons and dependencies.
+Leaf/container regressions cover nested creation, removal and overlapping records.
+Full tests pass with the issue-8 TMPDIR workaround; vet, build and whitespace pass.
+
 Evidence: [explain.go](../../explain.go), `replaceHistoryPath`, returns immediately
 when a mapping entry is absent, even when the replacement is a newly created value.
 

explain.go

@@ -134,7 +134,7 @@ func (r *Result[T]) Explain(path Path) (Explanation, bool) {
 	}
 
 	working = document.Clone(r.input)
-	for _, snapshot := range r.resolution {
+	for _, snapshot := range coalescedResolutionSnapshots(r.resolution) {
 		relevant := pathsIntersect(snapshot.change.Path, path)
 		var before ValueSnapshot
 		if relevant {
@@ -271,6 +271,37 @@ func mergeHistoryAtPath(root **document.Node, path Path, incoming *document.Node
 	}
 }
 
+// Resolution records describe one before/final transformation, not assignment
+// order. A parent already carries its descendants' final values; merge overlapping
+// intent into that event rather than replay a child assignment a second time.
+func coalescedResolutionSnapshots(snapshots []resolutionSnapshot) []resolutionSnapshot {
+	groups := make([]resolutionSnapshot, 0, len(snapshots))
+	for _, snapshot := range snapshots {
+		merged := false
+		for i := range groups {
+			if !pathContains(groups[i].change.Path, snapshot.change.Path) {
+				continue
+			}
+			for _, reason := range snapshot.change.Reasons {
+				groups[i].change.Reasons = appendUniqueString(groups[i].change.Reasons, reason)
+			}
+			for _, dependency := range snapshot.change.Dependencies {
+				groups[i].change.Dependencies = appendUniquePath(groups[i].change.Dependencies, dependency)
+			}
+			if snapshot.change.Origin.Operation == ChangeNormalization {
+				groups[i].change.Origin.Operation = ChangeNormalization
+			}
+			merged = true
+			break
+		}
+		if !merged {
+			snapshot.change = cloneChange(snapshot.change)
+			groups = append(groups, snapshot)
+		}
+	}
+	return groups
+}
+
 func replaceHistoryPath(root **document.Node, path Path, replacement *document.Node) {
 	if root == nil || *root == nil {
 		return
@@ -289,7 +320,19 @@ func replaceHistoryPath(root **document.Node, path Path, replacement *document.N
 			}
 			position := documentEntryIndex(current.Mapping, segment.key)
 			if position < 0 {
-				return
+				if replacement == nil {
+					return
+				}
+				child := &document.Node{Kind: document.Mapping}
+				if last {
+					child = document.Clone(replacement)
+				}
+				current.Mapping = append(current.Mapping, document.Entry{Key: segment.key, Value: child})
+				if last {
+					return
+				}
+				current = child
+				continue
 			}
 			if last {
 				if replacement == nil {

explain_test.go

@@ -365,3 +365,48 @@ func TestExplanationReconcilesDefaultsAfterInputReplacement(t *testing.T) {
 		}
 	}
 }
+
+func TestExplanationReplaysResolutionAdditionsAndOverlappingIntent(t *testing.T) {
+	type cfg struct {
+		M map[string]any `yaml:"m"`
+	}
+	for _, overlap := range []bool{false, true} {
+		t.Run(fmt.Sprint(overlap), func(t *testing.T) {
+			result, err := Load(Bytes("base", []byte("m: {old: 1}\n")), Options[cfg]{Definition: Definition[cfg]{Resolve: func(c *cfg, r *Resolution) error {
+				c.M["new"] = map[string]any{"child": int64(7)}
+				delete(c.M, "old")
+				r.Record(Keys("m", "new"), ChangeDerivedDefault, "add nested", Keys("m", "old"))
+				r.Record(Keys("m", "old"), ChangeNormalization, "remove old")
+				if overlap {
+					r.Record(Keys("m"), ChangeNormalization, "update container")
+				}
+				return nil
+			}}})
+			if err != nil {
+				t.Fatal(err)
+			}
+			for _, path := range []Path{Keys("m"), Keys("m", "new"), Keys("m", "new", "child"), Keys("m", "old")} {
+				x, ok := result.Explain(path)
+				if !ok {
+					t.Fatal("missing known history")
+				}
+				var count int
+				for _, v := range x.History {
+					if v.Origin.Layer == LayerResolution {
+						count++
+						if overlap && len(v.Reasons) != 3 {
+							t.Fatal("lost overlapping intent")
+						}
+					}
+				}
+				if overlap && count != 1 {
+					t.Fatalf("overlapping records applied %d times", count)
+				}
+				last := x.History[len(x.History)-1]
+				if last.After != x.Effective {
+					t.Fatalf("incorrect replay for %s: %#v", path, x)
+				}
+			}
+		})
+	}
+}