Avoid duplicate intermediate source history

docs/roadmap/remediation.md

@@ -123,7 +123,13 @@ checks effective and historical redaction.
 
 ## 2. Intermediate Source Definitions Are Duplicated In Metadata History
 
-Priority: P2. Status: open.
+Priority: P2. Status: complete.
+
+Completion: displaced definitions are omitted only when a preceding operation
+already introduced that concrete path with the same represented origin.
+`TestTierHistoryRecordsEachContributionOnce` failed before the fix and passes
+for both differing and equal-valued tiers. The full ordinary suite and
+`git diff --check` passed, including the existing shape-change regressions.
 
 Relevant code: `observeSourceEvidence` in
 [history_source.go](../../internal/engine/history_source.go), lines 82–117;

facade_tier_history_test.go

@@ -0,0 +1,43 @@
+package configkit_test
+
+import (
+	"testing"
+
+	configkit "gitea.maximumdirect.net/eric/ConfigKit"
+)
+
+func TestTierHistoryRecordsEachContributionOnce(t *testing.T) {
+	t.Parallel()
+	for _, middle := range []string{"mid", "low"} {
+		t.Run(middle, func(t *testing.T) {
+			result, err := configkit.LoadLayered[map[string]any](
+				configkit.Input{Source: configkit.Bytes("main", []byte("x: high\n"))},
+				configkit.LayeredOptions[map[string]any]{Underlays: []configkit.Underlay{
+					{Inputs: []configkit.Input{{Source: configkit.Bytes("low", []byte("x: low\n"))}}},
+					{Inputs: []configkit.Input{{Source: configkit.Bytes("middle", []byte("x: "+middle+"\n"))}}},
+				}},
+			)
+			if err != nil {
+				t.Fatal(err)
+			}
+			history := result.Metadata().History(configkit.Keys("x"))
+			if len(history) != 3 {
+				t.Fatalf("history has %d records; want the three independent contributions", len(history))
+			}
+			for index, sourceID := range []string{"source-2", "source-3", "source-1"} {
+				change := history[index]
+				if len(change.Origin.Locations) != 1 || change.Origin.Locations[0].SourceID != sourceID {
+					t.Fatalf("contribution %d has origin %#v", index, change.Origin)
+				}
+				if index == 0 {
+					if len(change.Previous) != 0 {
+						t.Fatal("first source contribution has a previous origin")
+					}
+				} else if len(change.Previous) != 1 || len(change.Previous[0].Locations) != 1 ||
+					change.Previous[0].Locations[0] != history[index-1].Origin.Locations[0] {
+					t.Fatalf("contribution %d has incorrect previous origin %#v", index, change.Previous)
+				}
+			}
+		})
+	}
+}

internal/engine/history_source.go

@@ -89,6 +89,9 @@ func (builder *historyBuilder) observeSourceEvidence(root *document.Node, origin
 			owned.hasApplicationRef = true
 		}
 		for displacedIndex, displaced := range record.displaced {
+			if sourceOriginRepresentedByOperation(builder.model, displaced.path, displaced.origin) {
+				continue
+			}
 			definitionPayload := payload
 			definitionPayload.substep = displacedIndex + 1
 			definition := builder.addAttribution(displaced.origin, nil, nil)
@@ -249,6 +252,9 @@ func sourceOriginRepresentedByOperation(model *historyModel, path Path, origin O
 		if observation.phase != historyPhaseSources || observation.role != historyRoleOperation {
 			return
 		}
+		if !observation.afterPresent || !sameConcreteHistoryPath(path, observation.path) {
+			return
+		}
 		operationOrigin, ok := model.resolveAttribution(observation.attributionRef)
 		if !ok {
 			return