diff --git a/docs/roadmap/remediation.md b/docs/roadmap/remediation.md
index 0e8ba1c..c725a3d 100644
--- a/docs/roadmap/remediation.md
+++ b/docs/roadmap/remediation.md
@@ -343,7 +343,14 @@ asserting timing or promising a new public call-count contract.
 
 ## 7. Explanation Dispatch Repeatedly Searches All Selections And Payloads
 
-Priority: P2. Status: open.
+Priority: P2. Status: complete.
+
+Completion: a query-local payload-reference index and application-fallback map
+are built in one pass over ordered selections. Source/CLI, inheritance, and
+resolution replay use direct lookups while retaining model chronology and the
+query-scoped attribution correction. The tier-history regression now also
+checks explanation contribution order/origins. The full ordinary suite and
+`git diff --check` passed; no replay algorithm or shared-state lifetime changed.
 
 Relevant code: `Inspection.Explain`, `historySelectionForPayload`,
 `historySelectionForApplication`, and `historySelectionForResolutionGroup` in
diff --git a/facade_tier_history_test.go b/facade_tier_history_test.go
index a790bb2..000adc2 100644
--- a/facade_tier_history_test.go
+++ b/facade_tier_history_test.go
@@ -24,11 +24,18 @@ func TestTierHistoryRecordsEachContributionOnce(t *testing.T) {
 			if len(history) != 3 {
 				t.Fatalf("history has %d records; want the three independent contributions", len(history))
 			}
+			explanation, found := result.Explain(configkit.Keys("x"))
+			if !found || len(explanation.History) != len(history) {
+				t.Fatal("explanation lost ordered tier contributions")
+			}
 			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 len(explanation.History[index].Origin.Locations) != 1 || explanation.History[index].Origin.Locations[0] != change.Origin.Locations[0] {
+					t.Fatalf("explanation contribution %d has a different source origin", index)
+				}
 				if index == 0 {
 					if len(change.Previous) != 0 {
 						t.Fatal("first source contribution has a previous origin")
diff --git a/internal/engine/explain.go b/internal/engine/explain.go
index e779944..12178e9 100644
--- a/internal/engine/explain.go
+++ b/internal/engine/explain.go
@@ -44,17 +44,18 @@ func (r *Inspection) Explain(path Path) (Explanation, bool) {
 	if model == nil {
 		return Explanation{}, false
 	}
-	selections := model.selectHistory(path)
-	if len(selections) == 0 && !model.hasObservedShape(path) {
+	selected := model.selectHistory(path)
+	if len(selected) == 0 && !model.hasObservedShape(path) {
 		return Explanation{}, false
 	}
+	selections := model.indexReplaySelections(selected)
 	explanation := Explanation{Path: path.clone(), Effective: valueSnapshotWithLookup(r.final, path, r.secrets, model.documentLookup)}
 	if info, ok := r.metadata.Lookup(path); ok {
 		explanation.Origin = cloneOrigin(info.Origin)
 	}
 
 	working := document.Clone(model.baseline)
-	if baseline, found := historySelectionForPayload(selections, historyPayloadRef{phase: historyPhaseBaseline, id: 0}); found && baseline.after {
+	if baseline, found := selections.byPayload[historyPayloadRef{phase: historyPhaseBaseline, id: 0}]; found && baseline.after {
 		explanation.History = append(explanation.History, ValueChange{
 			After:  valueSnapshot(working, path, r.secrets),
 			Origin: cloneOrigin(baseline.attribution.origin),
@@ -68,7 +69,7 @@ func (r *Inspection) Explain(path Path) (Explanation, bool) {
 		application := payload.application
 		before := valueSnapshot(working, path, r.secrets)
 		applyHistoryApplication(&working, application, replayIndex)
-		selected, relevant := historySelectionForApplication(model, selections, historyPhaseSources, historyPayloadRef{phase: historyPhaseSources, id: payloadID})
+		selected, relevant := selections.application(historyPayloadRef{phase: historyPhaseSources, id: payloadID})
 		if !relevant {
 			continue
 		}
@@ -88,7 +89,7 @@ func (r *Inspection) Explain(path Path) (Explanation, bool) {
 	// decoding applies them to the final input tree. Show that reconciliation
 	// explicitly before typed CLI contributions and domain resolution.
 	if checkpoint := model.preCLICheckpoint; checkpoint != nil {
-		selection, selected := historySelectionForPayload(selections, historyPayloadRef{phase: historyPhasePreCLI, id: 0})
+		selection, selected := selections.byPayload[historyPayloadRef{phase: historyPhasePreCLI, id: 0}]
 		replayed, _ := documentAtPath(working, path)
 		decoded, _ := documentAtPathWithLookup(checkpoint.root, path, model.documentLookup)
 		if selected && !configurationValuesEqual(replayed, decoded) {
@@ -110,7 +111,7 @@ func (r *Inspection) Explain(path Path) (Explanation, bool) {
 		applicationRef := historyPayloadRef{phase: historyPhaseCLI, id: payloadID}
 		before := valueSnapshot(working, path, r.secrets)
 		applyHistoryApplication(&working, payload.application, replayIndex)
-		selected, relevant := historySelectionForApplication(model, selections, historyPhaseCLI, applicationRef)
+		selected, relevant := selections.application(applicationRef)
 		if !relevant {
 			continue
 		}
@@ -125,7 +126,7 @@ func (r *Inspection) Explain(path Path) (Explanation, bool) {
 		})
 	}
 	if checkpoint := model.postCLICheckpoint; checkpoint != nil {
-		selection, selected := historySelectionForPayload(selections, historyPayloadRef{phase: historyPhasePostCLI, id: 0})
+		selection, selected := selections.byPayload[historyPayloadRef{phase: historyPhasePostCLI, id: 0}]
 		replayed, _ := documentAtPath(working, path)
 		effectiveInput, _ := documentAtPathWithLookup(checkpoint.root, path, model.documentLookup)
 		if selected && !configurationValuesEqual(replayed, effectiveInput) {
@@ -141,7 +142,7 @@ func (r *Inspection) Explain(path Path) (Explanation, bool) {
 	}
 	if model.resolutionPayload != nil {
 		for _, group := range model.resolutionPayload.replayGroups {
-			selection, selected := historySelectionForResolutionGroup(selections, group)
+			selection, selected := selections.resolutionGroup(group)
 			if !selected || group.coveringRecordID < 0 || group.coveringRecordID >= len(model.resolutionPayload.snapshots) {
 				continue
 			}
@@ -171,41 +172,51 @@ func (r *Inspection) Explain(path Path) (Explanation, bool) {
 	return explanation, true
 }
 
-func historySelectionForPayload(selections []historySelection, ref historyPayloadRef) (historySelection, bool) {
-	for _, selection := range selections {
-		if selection.payload == ref {
-			return selection, true
-		}
-	}
-	return historySelection{}, false
+// historyReplaySelections is query-local dispatch state, not another evidence
+// or attribution owner. Replay still follows the model's ordered payloads.
+type historyReplaySelections struct {
+	byPayload            map[historyPayloadRef]historySelection
+	applicationFallbacks map[historyPayloadRef]historySelection
 }
 
-func historySelectionForApplication(model *historyModel, selections []historySelection, phase historyPhase, applicationRef historyPayloadRef) (historySelection, bool) {
-	if direct, ok := historySelectionForPayload(selections, applicationRef); ok {
-		return direct, true
+func (model *historyModel) indexReplaySelections(ordered []historySelection) historyReplaySelections {
+	indexed := historyReplaySelections{
+		byPayload:            make(map[historyPayloadRef]historySelection, len(ordered)),
+		applicationFallbacks: make(map[historyPayloadRef]historySelection),
 	}
-	// Only removed/replaced paths lacking a direct contribution need an
-	// operation fallback. A descendant's location cannot describe its container.
-	var selected historySelection
-	found := false
-	var payloads []historySourcePayload
-	switch phase {
-	case historyPhaseSources:
-		payloads = model.sourcePayloads
-	case historyPhaseCLI:
-		payloads = model.cliPayloads
-	default:
-		return selected, found
-	}
-	for payloadID, candidate := range payloads {
-		if candidate.kind != historySourceOverlayPayload || !candidate.hasApplicationRef || candidate.applicationRef != applicationRef {
+	for _, selection := range ordered {
+		ref := selection.payload
+		indexed.byPayload[ref] = selection
+		if selection.role != historyRoleOperation || ref.substep != 0 {
 			continue
 		}
-		if operation, ok := historySelectionForPayload(selections, historyPayloadRef{phase: phase, id: payloadID}); ok {
-			selected, found = operation, true
+		var payloads []historySourcePayload
+		switch ref.phase {
+		case historyPhaseSources:
+			payloads = model.sourcePayloads
+		case historyPhaseCLI:
+			payloads = model.cliPayloads
+		default:
+			continue
+		}
+		if ref.id < 0 || ref.id >= len(payloads) {
+			continue
+		}
+		payload := payloads[ref.id]
+		if payload.kind == historySourceOverlayPayload && payload.hasApplicationRef {
+			indexed.applicationFallbacks[payload.applicationRef] = selection
 		}
 	}
-	return selected, found
+	return indexed
+}
+
+func (selections historyReplaySelections) application(ref historyPayloadRef) (historySelection, bool) {
+	if direct, found := selections.byPayload[ref]; found {
+		return direct, true
+	}
+	// Only removed/replaced paths lacking a direct contribution need fallback.
+	selection, found := selections.applicationFallbacks[ref]
+	return selection, found
 }
 
 func checkpointExplanationAttribution(selection historySelection) (Origin, []string) {
@@ -215,11 +226,11 @@ func checkpointExplanationAttribution(selection historySelection) (Origin, []str
 	return Origin{Operation: ChangeDecoding}, nil
 }
 
-func historySelectionForResolutionGroup(selections []historySelection, group resolutionReplayGroup) (historySelection, bool) {
+func (selections historyReplaySelections) resolutionGroup(group resolutionReplayGroup) (historySelection, bool) {
 	var fallback historySelection
 	found := false
 	for _, recordID := range group.originalRecordIDs {
-		selection, ok := historySelectionForPayload(selections, historyPayloadRef{phase: historyPhaseResolution, id: recordID})
+		selection, ok := selections.byPayload[historyPayloadRef{phase: historyPhaseResolution, id: recordID}]
 		if !ok {
 			continue
 		}
diff --git a/internal/engine/inheritance_explain.go b/internal/engine/inheritance_explain.go
index dcc3a45..bea0403 100644
--- a/internal/engine/inheritance_explain.go
+++ b/internal/engine/inheritance_explain.go
@@ -2,7 +2,7 @@ package engine
 
 import "gitea.maximumdirect.net/eric/ConfigKit/internal/document"
 
-func appendInheritanceExplanation(explanation *Explanation, working **document.Node, query Path, model *historyModel, selections []historySelection, secrets map[string]bool) {
+func appendInheritanceExplanation(explanation *Explanation, working **document.Node, query Path, model *historyModel, selections historyReplaySelections, secrets map[string]bool) {
 	if model == nil {
 		return
 	}
@@ -10,7 +10,7 @@ func appendInheritanceExplanation(explanation *Explanation, working **document.N
 		for operationIndex, operation := range payload.operations {
 			if operation.control != nil {
 				ref := historyPayloadRef{phase: historyPhaseInheritance, id: 0, substep: operationIndex * 2}
-				selection, selected := historySelectionForPayload(selections, ref)
+				selection, selected := selections.byPayload[ref]
 				if !selected {
 					continue
 				}
@@ -25,8 +25,8 @@ func appendInheritanceExplanation(explanation *Explanation, working **document.N
 			}
 			parentRef := historyPayloadRef{phase: historyPhaseInheritance, id: 0, substep: operationIndex * 2}
 			childRef := historyPayloadRef{phase: historyPhaseInheritance, id: 0, substep: operationIndex*2 + 1}
-			parentSelection, hasParent := historySelectionForPayload(selections, parentRef)
-			childSelection, hasChild := historySelectionForPayload(selections, childRef)
+			parentSelection, hasParent := selections.byPayload[parentRef]
+			childSelection, hasChild := selections.byPayload[childRef]
 			before := valueSnapshot(*working, query, secrets)
 			replaceHistoryPath(working, operation.transfer.to, operation.parent)
 			// A record keeps its own identity throughout inheritance. Restore it