diff --git a/docs/roadmap/implementation.md b/docs/roadmap/implementation.md
index dccef0d..5acc494 100644
--- a/docs/roadmap/implementation.md
+++ b/docs/roadmap/implementation.md
@@ -347,6 +347,13 @@ Findings: **D04, F05**.
 Owners: `internal/engine/sequence_combine.go`, `inheritance*.go`, `compose.go`,
 `history.go`, `secret.go`, `destination.go`, and associated tests.
 
+Status: **complete** (D04, F05). Prior completed commits: `2736ddf`,
+`deb9aa5`, `ae3408a`, `ea27f17`, `08a8c25`, `877c497`, `8aba43d`,
+`7bf2f0c`, `0f9ecf1`, `119b42c`. Validation passed:
+`env GOTOOLCHAIN=local GOPROXY=off GOTELEMETRY=off go test ./internal/engine -run 'Sequence|Collection|Inheritance|History|Secret|Destination' -count=1`,
+`env GOTOOLCHAIN=local GOPROXY=off GOTELEMETRY=off go test ./internal/engine -count=1`,
+and `git diff --check`.
+
 Remove unread `discardedLower` and `inheritanceReplacement.path`, `previous`, and
 `effective`, plus calculations solely producing them. Keep replacement `before`
 and `after` trees for accounting, projections, active origins/history, and append's
diff --git a/internal/engine/compose.go b/internal/engine/compose.go
index efb26ea..968d685 100644
--- a/internal/engine/compose.go
+++ b/internal/engine/compose.go
@@ -483,21 +483,6 @@ func allMappingClaims(claims []compositionClaim) bool {
 	return true
 }
 
-func mergeDisjointMappings(target, incoming *document.Node, index *mappingIndex) {
-	for _, incomingEntry := range incoming.Mapping {
-		position := index.find(target, incomingEntry.Key)
-		if position < 0 {
-			cloned := incomingEntry
-			cloned.Value = document.Clone(incomingEntry.Value)
-			index.append(target, cloned)
-			continue
-		}
-		// Claim validation guarantees that the only remaining overlap is a
-		// mapping pair. Empty mappings naturally contribute no child entries.
-		mergeDisjointMappings(target.Mapping[position].Value, incomingEntry.Value, index)
-	}
-}
-
 func documentEntryIndex(entries []document.Entry, key string) int {
 	for index := range entries {
 		if entries[index].Key == key {
diff --git a/internal/engine/destination.go b/internal/engine/destination.go
index 7bdceb2..efdd4c6 100644
--- a/internal/engine/destination.go
+++ b/internal/engine/destination.go
@@ -18,13 +18,6 @@ const (
 	placementModeSequenceItem
 )
 
-// PlacementModeFromFacade preserves root-owned numeric values until preflight
-// can reject unsupported modes.
-func PlacementModeFromFacade(value uint8) placementMode { return placementMode(value) }
-
-// PlacementModeForFacade converts private source evidence to the root-owned mode.
-func PlacementModeForFacade(value placementMode) uint8 { return uint8(value) }
-
 // InputWithPlacement copies the root-owned mode into a private engine input.
 func InputWithPlacement(input Input, value uint8) Input {
 	input.placementMode = placementMode(value)
diff --git a/internal/engine/history.go b/internal/engine/history.go
index a0fc903..758410b 100644
--- a/internal/engine/history.go
+++ b/internal/engine/history.go
@@ -237,10 +237,6 @@ func applyHistoryApplication(root **document.Node, application historyApplicatio
 	mergeHistoryAtPath(root, application.path, application.value, index, application.sequencesByPath)
 }
 
-func mergeHistoryDocument(target **document.Node, incoming *document.Node, index *mappingIndex) {
-	mergeHistoryDocumentAtPath(target, incoming, Path{}, index, nil)
-}
-
 func mergeHistoryDocumentAtPath(target **document.Node, incoming *document.Node, path Path, index *mappingIndex, sequences map[string]sequenceHistoryContributionIndex) {
 	if incoming == nil {
 		return
diff --git a/internal/engine/inheritance.go b/internal/engine/inheritance.go
index 8436193..eb32d8f 100644
--- a/internal/engine/inheritance.go
+++ b/internal/engine/inheritance.go
@@ -129,15 +129,11 @@ func projectInheritancePolicyTemplates(templates []collectionPolicyScope, prefix
 	return projected
 }
 
-// A replacement retains the displaced source/derivation record while the
-// effective origin belongs to the child. Value trees are borrowed immutable
-// inputs or detached templates and are budgeted with retained history later.
+// A replacement retains the before and after values for history accounting.
+// The trees are borrowed immutable inputs or detached templates.
 type inheritanceReplacement struct {
-	path      Path
-	before    *document.Node
-	after     *document.Node
-	previous  []displacedDefinition
-	effective Origin
+	before *document.Node
+	after  *document.Node
 }
 
 // A link represents one shared relationship edge. Each contributor retains
@@ -173,11 +169,6 @@ func inheritanceDirective(node *document.Node) (document.Entry, bool) {
 	return document.Entry{}, false
 }
 
-func inheritanceDirectiveLocation(node *document.Node) Location {
-	entry, _ := inheritanceDirective(node)
-	return publicLocation(entry.Value.Location)
-}
-
 func withoutInheritanceDirective(node *document.Node) *document.Node {
 	payload := *node
 	payload.Mapping = make([]document.Entry, 0, len(node.Mapping))
diff --git a/internal/engine/inheritance_collection.go b/internal/engine/inheritance_collection.go
index 6af19bf..d229aad 100644
--- a/internal/engine/inheritance_collection.go
+++ b/internal/engine/inheritance_collection.go
@@ -237,10 +237,8 @@ func applyInheritanceSequenceOrigins(
 	var replacements []inheritanceReplacement
 	if operation == sequenceModeReplace {
 		if lower != nil {
-			displaced := displacedOrigins(lower, origins, path)
 			replacements = append(replacements, inheritanceReplacement{
-				path: path.clone(), before: lower, after: higher,
-				previous: displaced, effective: cloneOrigin(incomingOrigins[path.String()]),
+				before: lower, after: higher,
 			})
 			deleteOriginSubtree(origins, path, lower)
 		}
@@ -265,12 +263,10 @@ func applyInheritanceSequenceOrigins(
 		lowerPath := path.Index(replacement.lowerIndex)
 		higherPath := path.Index(replacement.higherIndex)
 		outputPath := path.Index(replacement.outputIndex)
-		previous := displacedOrigins(lower.Sequence[replacement.lowerIndex], origins, lowerPath)
 		deleteOriginSubtree(origins, lowerPath, lower.Sequence[replacement.lowerIndex])
 		copyInheritanceSubtreeAt(origins, incomingOrigins, higher.Sequence[replacement.higherIndex], higherPath, outputPath)
 		replacements = append(replacements, inheritanceReplacement{
-			path: outputPath, before: lower.Sequence[replacement.lowerIndex], after: higher.Sequence[replacement.higherIndex],
-			previous: previous, effective: cloneOrigin(incomingOrigins[higherPath.String()]),
+			before: lower.Sequence[replacement.lowerIndex], after: higher.Sequence[replacement.higherIndex],
 		})
 	}
 	for _, projection := range combined.higherItems {
diff --git a/internal/engine/inheritance_combine.go b/internal/engine/inheritance_combine.go
index 33271b1..ce2d33d 100644
--- a/internal/engine/inheritance_combine.go
+++ b/internal/engine/inheritance_combine.go
@@ -55,10 +55,8 @@ func combineInheritanceTemplate(
 			mergeInheritanceOrigin(mergedOrigins, childPath, child.origins[childPath.String()])
 		},
 		replaced: func(childPath Path, existing, incoming *document.Node) {
-			previous := displacedOrigins(existing, mergedOrigins, childPath)
 			result.replacements = append(result.replacements, inheritanceReplacement{
-				path: childPath.clone(), before: existing, after: incoming,
-				previous: previous, effective: cloneOrigin(child.origins[childPath.String()]),
+				before: existing, after: incoming,
 			})
 			deleteOriginSubtree(mergedOrigins, childPath, existing)
 			copyInheritanceSubtree(mergedOrigins, child.origins, incoming, childPath)
diff --git a/internal/engine/inheritance_identified_test.go b/internal/engine/inheritance_identified_test.go
index c62b6d6..3e6a3e4 100644
--- a/internal/engine/inheritance_identified_test.go
+++ b/internal/engine/inheritance_identified_test.go
@@ -198,11 +198,6 @@ func TestIdentifiedInheritanceResolvesNestedCollectionsAtEachDestination(t *test
 	if _, found := expanded.origins["/jobs/0/steps/1/value"]; !found {
 		t.Fatal("nested inherited value did not retain its destination origin")
 	}
-	for _, replacement := range expanded.replacements {
-		if replacement.path.String() == "/jobs/0/id" {
-			t.Fatal("parent identity was treated as payload replaced by the child's identity")
-		}
-	}
 }
 
 func TestIdentifiedInheritanceRespectsOutputNodeBudget(t *testing.T) {
diff --git a/internal/engine/inheritance_origin_test.go b/internal/engine/inheritance_origin_test.go
index bec8a98..6d3c534 100644
--- a/internal/engine/inheritance_origin_test.go
+++ b/internal/engine/inheritance_origin_test.go
@@ -44,11 +44,8 @@ func TestInheritedOriginsKeepSourcePathsPresenceAndIndependentReplacement(t *tes
 	if len(count.Locations) != 1 || count.Locations[0].SourceID != "source-2" || len(projectInheritanceSteps(count)) != 0 {
 		t.Fatalf("direct replacement origin = %#v", count)
 	}
-	if len(result.replacements) != 1 || result.replacements[0].path.String() != "/child/count" ||
-		result.replacements[0].before.Text != "0" || result.replacements[0].after.Text != "3" ||
-		len(result.replacements[0].previous) != 1 ||
-		len(projectInheritanceSteps(result.replacements[0].previous[0].origin)) != 1 {
-		t.Fatalf("displaced inheritance = %#v", result.replacements)
+	if len(result.replacements) != 1 || result.replacements[0].before.Text != "0" || result.replacements[0].after.Text != "3" {
+		t.Fatalf("replacement accounting values = %#v", result.replacements)
 	}
 	settings := result.origins["/child/settings"]
 	if len(settings.Locations) != 2 || settings.Locations[0].SourceID != "source-1" ||
diff --git a/internal/engine/secret.go b/internal/engine/secret.go
index c38735b..0f4bcc1 100644
--- a/internal/engine/secret.go
+++ b/internal/engine/secret.go
@@ -134,12 +134,6 @@ func classifySecretPathsWithEvidence(schema *schemaDescriptor, predicate func(Pa
 	return closeSecretDependencies(paths, secret, dependencies, inherited)
 }
 
-func addSecretEvidencePath(paths map[string]Path, destination, local Path) Path {
-	path := appendDestination(destination, local)
-	addSecretPath(paths, path.String())
-	return path
-}
-
 func addSecretPath(paths map[string]Path, pointer string) {
 	if existing, found := paths[pointer]; found && existing.valid() {
 		// Accumulator keys already match their paths' canonical spelling. History
diff --git a/internal/engine/sequence_combine.go b/internal/engine/sequence_combine.go
index a63f66d..41ac3c1 100644
--- a/internal/engine/sequence_combine.go
+++ b/internal/engine/sequence_combine.go
@@ -23,7 +23,6 @@ type sequenceCombinationResult struct {
 	higherItems    []sequenceItemProjection
 	replacements   []sequenceItemReplacement
 	appendedHigher []int
-	discardedLower []int
 }
 
 func combineSequence(
@@ -36,7 +35,7 @@ func combineSequence(
 	}
 	switch policy.operation {
 	case sequenceModeReplace:
-		return replaceSequence(lower, higher, policy.effectiveIdentityFields, context)
+		return replaceSequence(higher, policy.effectiveIdentityFields, context)
 	case sequenceModeAppend, sequenceModeUpsert:
 		return combineIdentifiedSequences(lower, higher, policy.operation, policy.effectiveIdentityFields, context)
 	default:
@@ -55,7 +54,7 @@ func unchangedSequenceValue(lower *document.Node) sequenceCombinationResult {
 }
 
 func replaceSequence(
-	lower, higher *document.Node,
+	higher *document.Node,
 	identityFields []string,
 	context sequenceCombinationContext,
 ) (sequenceCombinationResult, []Diagnostic) {
@@ -68,9 +67,6 @@ func replaceSequence(
 	if higher.Kind == document.Sequence {
 		result.higherItems = sequenceItemProjections(len(higher.Sequence), 0)
 	}
-	if lower != nil && lower.Kind == document.Sequence {
-		result.discardedLower = sequenceIndexes(len(lower.Sequence))
-	}
 	return result, nil
 }
 
diff --git a/internal/engine/sequence_combine_test.go b/internal/engine/sequence_combine_test.go
index eaea064..ed5140c 100644
--- a/internal/engine/sequence_combine_test.go
+++ b/internal/engine/sequence_combine_test.go
@@ -19,13 +19,12 @@ func TestCombineSequenceOperationsAndItemEvidence(t *testing.T) {
 		wantHigher       []sequenceItemProjection
 		wantReplacements []sequenceItemReplacement
 		wantAppended     []int
-		wantDiscarded    []int
 	}{
 		{
 			name:  "replace uses only higher records",
 			lower: "items: [{id: a}, {id: b}]\n", higher: "items: [{id: b, text: revised}]\n",
 			operation: sequenceModeReplace, want: []string{"b"},
-			wantHigher: []sequenceItemProjection{{inputIndex: 0, outputIndex: 0}}, wantDiscarded: []int{0, 1},
+			wantHigher: []sequenceItemProjection{{inputIndex: 0, outputIndex: 0}},
 		},
 		{
 			name:  "append retains then appends",
@@ -57,7 +56,7 @@ func TestCombineSequenceOperationsAndItemEvidence(t *testing.T) {
 			if got := sequenceIdentityValues(result.value, "id"); !reflect.DeepEqual(got, test.want) {
 				t.Fatalf("combined IDs = %#v, want %#v", got, test.want)
 			}
-			if !reflect.DeepEqual(result.lowerItems, test.wantLower) || !reflect.DeepEqual(result.higherItems, test.wantHigher) || !reflect.DeepEqual(result.replacements, test.wantReplacements) || !reflect.DeepEqual(result.appendedHigher, test.wantAppended) || !reflect.DeepEqual(result.discardedLower, test.wantDiscarded) {
+			if !reflect.DeepEqual(result.lowerItems, test.wantLower) || !reflect.DeepEqual(result.higherItems, test.wantHigher) || !reflect.DeepEqual(result.replacements, test.wantReplacements) || !reflect.DeepEqual(result.appendedHigher, test.wantAppended) {
 				t.Fatalf("item evidence = %#v", result)
 			}
 		})
@@ -112,7 +111,7 @@ func TestReplaceSequenceAllowsNullAndNonSequenceValues(t *testing.T) {
 			lower := sequenceFromYAML(t, "items: [{id: lower}]\n")
 			higher := sequenceFromYAML(t, test.higher)
 			result, diagnostics := combineSequence(lower, higher, sequenceCombinationPolicy(sequenceModeReplace), sequenceCombinationContext{destination: Keys("items")})
-			if len(diagnostics) != 0 || result.value == nil || result.value.Kind != test.wantKind || !reflect.DeepEqual(result.discardedLower, []int{0}) {
+			if len(diagnostics) != 0 || result.value == nil || result.value.Kind != test.wantKind {
 				t.Fatalf("replacement result = %#v, %#v", result, diagnostics)
 			}
 		})
@@ -172,7 +171,7 @@ func TestCombineSequenceReplacementResetsLowerIdentity(t *testing.T) {
 	higher := sequenceFromYAML(t, "items: [{name: new}]\n")
 	policy := sequenceCombinationPolicy(sequenceModeReplace, "name")
 	result, diagnostics := combineSequence(lower, higher, policy, sequenceCombinationContext{destination: Keys("items")})
-	if len(diagnostics) != 0 || !reflect.DeepEqual(sequenceIdentityValues(result.value, "name"), []string{"new"}) || !reflect.DeepEqual(result.discardedLower, []int{0}) {
+	if len(diagnostics) != 0 || !reflect.DeepEqual(sequenceIdentityValues(result.value, "name"), []string{"new"}) {
 		t.Fatalf("replacement applied obsolete identity: %#v, %#v", result, diagnostics)
 	}
 }