diff --git a/internal/modules/dnd/shared/source_ref_order.go b/internal/modules/dnd/shared/source_ref_order.go
index 06a9699..7027b75 100644
--- a/internal/modules/dnd/shared/source_ref_order.go
+++ b/internal/modules/dnd/shared/source_ref_order.go
@@ -15,10 +15,16 @@ type SourceRefOrder struct {
 
 // NewSourceRefOrder captures the source identity and unit positions from doc.
 func NewSourceRefOrder(doc *source.SourceDocument) SourceRefOrder {
+	return NewSourceRefOrderWithIndex(doc, source.NewDocumentIndex(doc))
+}
+
+// NewSourceRefOrderWithIndex captures source identity with a supplied
+// document index for source-reference comparison and canonicalization.
+func NewSourceRefOrderWithIndex(doc *source.SourceDocument, index source.DocumentIndex) SourceRefOrder {
 	if doc == nil {
 		return SourceRefOrder{}
 	}
-	return SourceRefOrder{sourceID: doc.ID, index: source.NewDocumentIndex(doc)}
+	return SourceRefOrder{sourceID: doc.ID, index: index}
 }
 
 // Less orders references by source identity, then document positions when
diff --git a/internal/modules/dnd/validate/combatturns/invariants/validator.go b/internal/modules/dnd/validate/combatturns/invariants/validator.go
index c2d65ff..0a4ec9b 100644
--- a/internal/modules/dnd/validate/combatturns/invariants/validator.go
+++ b/internal/modules/dnd/validate/combatturns/invariants/validator.go
@@ -48,10 +48,14 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 // Validate checks only invariants owned by normalized combat-turn output. A
 // shape or source-reference failure is deliberately deferred to its owner.
 func Validate(doc *source.SourceDocument, value dnd.CombatTurnList) error {
-	if combatshape.Validate(value) != nil || !sourceRefsValid(doc, value) {
+	if combatshape.Validate(value) != nil {
 		return nil
 	}
-	issues := issuesFor(shared.NewSourceRefOrder(doc), value)
+	index := source.NewDocumentIndex(doc)
+	if !sourceRefsValid(index, value) {
+		return nil
+	}
+	issues := issuesFor(shared.NewSourceRefOrderWithIndex(doc, index), value)
 	if len(issues) == 0 {
 		return nil
 	}
@@ -97,10 +101,10 @@ func issuesFor(order shared.SourceRefOrder, value dnd.CombatTurnList) []string {
 	return issues
 }
 
-func sourceRefsValid(doc *source.SourceDocument, value dnd.CombatTurnList) bool {
+func sourceRefsValid(index source.DocumentIndex, value dnd.CombatTurnList) bool {
 	for _, turn := range value.CombatTurns {
 		for _, ref := range turn.SourceRefs {
-			if source.ValidateRef(doc, ref) != nil {
+			if index.ValidateRef(ref) != nil {
 				return false
 			}
 		}
diff --git a/internal/modules/dnd/validate/combatturns/source_refs/validator.go b/internal/modules/dnd/validate/combatturns/source_refs/validator.go
index 590b5ca..8e10b80 100644
--- a/internal/modules/dnd/validate/combatturns/source_refs/validator.go
+++ b/internal/modules/dnd/validate/combatturns/source_refs/validator.go
@@ -37,7 +37,7 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 	if err := combatshape.Validate(req.Value); err != nil {
 		return contracts.ValidationResult{Approved: true}, nil
 	}
-	issues := sourceRefIssues(req.Source, req.Value)
+	issues := sourceRefIssues(source.NewDocumentIndex(req.Source), req.Value)
 	if len(issues) == 0 {
 		return contracts.ValidationResult{Approved: true}, nil
 	}
@@ -48,11 +48,11 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 	}, nil
 }
 
-func sourceRefIssues(doc *source.SourceDocument, value dnd.CombatTurnList) []string {
+func sourceRefIssues(index source.DocumentIndex, value dnd.CombatTurnList) []string {
 	issues := make([]string, 0)
 	for turnIndex, turn := range value.CombatTurns {
 		for refIndex, ref := range turn.SourceRefs {
-			if err := source.ValidateRef(doc, ref); err != nil {
+			if err := index.ValidateRef(ref); err != nil {
 				issues = append(issues, fmt.Sprintf("combat_turns[%d].source_refs[%d]: %s", turnIndex, refIndex, diagnostics.Truncate(err.Error())))
 			}
 		}
diff --git a/internal/modules/dnd/validate/npcinteractions/invariants/validator.go b/internal/modules/dnd/validate/npcinteractions/invariants/validator.go
index 064d561..aa33e4f 100644
--- a/internal/modules/dnd/validate/npcinteractions/invariants/validator.go
+++ b/internal/modules/dnd/validate/npcinteractions/invariants/validator.go
@@ -77,7 +77,11 @@ func (v *Validator) CheckpointFingerprints() []pipeline.CheckpointFingerprint {
 }
 
 func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationRequest[dnd.NPCInteractionList]) (contracts.ValidationResult, error) {
-	if interactionshape.Validate(req.Value) != nil || !allSourceRefsValid(req.Source, req.Value) {
+	if interactionshape.Validate(req.Value) != nil {
+		return contracts.ValidationResult{Approved: true}, nil
+	}
+	index := source.NewDocumentIndex(req.Source)
+	if !allSourceRefsValid(index, req.Value) {
 		return contracts.ValidationResult{Approved: true}, nil
 	}
 	if v == nil || v.npcResolver == nil {
@@ -90,7 +94,7 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 	if !npcRegistry.Bound() {
 		return contracts.ValidationResult{Approved: false, ReasonCode: ReasonCode, Message: "invalid NPC interaction normalization: NPC registry reference is required"}, nil
 	}
-	issues := issuesFor(req.Source, shared.NewSourceRefOrder(req.Source), req.Value, npcRegistry)
+	issues := issuesFor(shared.NewSourceRefOrderWithIndex(req.Source, index), req.Value, npcRegistry)
 	if len(issues) == 0 {
 		return contracts.ValidationResult{Approved: true}, nil
 	}
@@ -101,16 +105,18 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 	}, nil
 }
 
-func allSourceRefsValid(doc *source.SourceDocument, value dnd.NPCInteractionList) bool {
+func allSourceRefsValid(index source.DocumentIndex, value dnd.NPCInteractionList) bool {
 	for _, interaction := range value.Interactions {
-		if !interactionmodel.ValidSourceRefs(doc, interaction.SourceRefs) {
-			return false
+		for _, ref := range interaction.SourceRefs {
+			if index.ValidateRef(ref) != nil {
+				return false
+			}
 		}
 	}
 	return true
 }
 
-func issuesFor(doc *source.SourceDocument, order shared.SourceRefOrder, value dnd.NPCInteractionList, npcRegistry *npcregistry.Registry) []string {
+func issuesFor(order shared.SourceRefOrder, value dnd.NPCInteractionList, npcRegistry *npcregistry.Registry) []string {
 	issues := make([]string, 0)
 	for index, interaction := range value.Interactions {
 		prefix := fmt.Sprintf("interactions[%d]", index)
diff --git a/internal/modules/dnd/validate/npcinteractions/source_refs/validator.go b/internal/modules/dnd/validate/npcinteractions/source_refs/validator.go
index c3486c3..8195efb 100644
--- a/internal/modules/dnd/validate/npcinteractions/source_refs/validator.go
+++ b/internal/modules/dnd/validate/npcinteractions/source_refs/validator.go
@@ -41,10 +41,11 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 	if interactionshape.Validate(req.Value) != nil {
 		return contracts.ValidationResult{Approved: true}, nil
 	}
+	index := source.NewDocumentIndex(req.Source)
 	issues := make([]string, 0)
 	for interactionIndex, interaction := range req.Value.Interactions {
 		for refIndex, ref := range interaction.SourceRefs {
-			if err := source.ValidateRef(req.Source, ref); err != nil {
+			if err := index.ValidateRef(ref); err != nil {
 				issues = append(issues, fmt.Sprintf("interactions[%d].source_refs[%d]: %s", interactionIndex, refIndex, diagnostics.Truncate(err.Error())))
 				continue
 			}
diff --git a/internal/modules/dnd/validate/npcs/source_refs/validator.go b/internal/modules/dnd/validate/npcs/source_refs/validator.go
index c8635fa..7adc1f4 100644
--- a/internal/modules/dnd/validate/npcs/source_refs/validator.go
+++ b/internal/modules/dnd/validate/npcs/source_refs/validator.go
@@ -37,10 +37,11 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 	if err := npcshape.Validate(req.Value); err != nil {
 		return contracts.ValidationResult{Approved: true}, nil
 	}
+	index := source.NewDocumentIndex(req.Source)
 	issues := make([]string, 0)
 	for npcIndex, npc := range req.Value.NPCs {
 		for refIndex, ref := range npc.SourceRefs {
-			if err := source.ValidateRef(req.Source, ref); err != nil {
+			if err := index.ValidateRef(ref); err != nil {
 				issues = append(issues, fmt.Sprintf("npcs[%d].source_refs[%d]: %s", npcIndex, refIndex, diagnostics.Truncate(err.Error())))
 			}
 		}
diff --git a/internal/modules/dnd/validate/scenedescriptions/invariants/validator.go b/internal/modules/dnd/validate/scenedescriptions/invariants/validator.go
index e39511e..4b93a63 100644
--- a/internal/modules/dnd/validate/scenedescriptions/invariants/validator.go
+++ b/internal/modules/dnd/validate/scenedescriptions/invariants/validator.go
@@ -36,10 +36,14 @@ func (v *Validator) CheckpointFingerprints() []pipeline.CheckpointFingerprint {
 }
 
 func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationRequest[dnd.SceneDescriptionList]) (contracts.ValidationResult, error) {
-	if shape.Validate(req.Value) != nil || !sourceRefsValid(req.Source, req.Value) {
+	if shape.Validate(req.Value) != nil {
 		return contracts.ValidationResult{Approved: true}, nil
 	}
-	issues := issuesFor(req.Source, req.Value)
+	index := source.NewDocumentIndex(req.Source)
+	if !sourceRefsValid(index, req.Value) {
+		return contracts.ValidationResult{Approved: true}, nil
+	}
+	issues := issuesFor(index, req.Value)
 	if len(issues) == 0 {
 		return contracts.ValidationResult{Approved: true}, nil
 	}
@@ -49,20 +53,20 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 	}, nil
 }
 
-func sourceRefsValid(doc *source.SourceDocument, value dnd.SceneDescriptionList) bool {
+func sourceRefsValid(index source.DocumentIndex, value dnd.SceneDescriptionList) bool {
 	for _, scene := range value.Scenes {
-		if source.ValidateRef(doc, scene.SourceRef) != nil {
+		if index.ValidateRef(scene.SourceRef) != nil {
 			return false
 		}
 	}
 	return true
 }
 
-func issuesFor(doc *source.SourceDocument, value dnd.SceneDescriptionList) []string {
+func issuesFor(index source.DocumentIndex, value dnd.SceneDescriptionList) []string {
 	issues := make([]string, 0)
 	if !sort.SliceIsSorted(value.Scenes, func(left, right int) bool {
-		leftStart, _ := source.UnitIndex(doc, value.Scenes[left].SourceRef.StartUnitID)
-		rightStart, _ := source.UnitIndex(doc, value.Scenes[right].SourceRef.StartUnitID)
+		leftStart, _ := index.Position(value.Scenes[left].SourceRef.StartUnitID)
+		rightStart, _ := index.Position(value.Scenes[right].SourceRef.StartUnitID)
 		if leftStart != rightStart {
 			return leftStart < rightStart
 		}
diff --git a/internal/modules/dnd/validate/scenedescriptions/source_refs/validator.go b/internal/modules/dnd/validate/scenedescriptions/source_refs/validator.go
index 8241d7b..9f0942b 100644
--- a/internal/modules/dnd/validate/scenedescriptions/source_refs/validator.go
+++ b/internal/modules/dnd/validate/scenedescriptions/source_refs/validator.go
@@ -42,9 +42,10 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 	if req.Stage == string(pipeline.StageExtract) && req.Chunk == nil {
 		issues = append(issues, "current extraction chunk must not be nil")
 	}
-	for index, scene := range req.Value.Scenes {
-		prefix := fmt.Sprintf("scenes[%d]", index)
-		if err := source.ValidateRef(req.Source, scene.SourceRef); err != nil {
+	index := source.NewDocumentIndex(req.Source)
+	for sceneIndex, scene := range req.Value.Scenes {
+		prefix := fmt.Sprintf("scenes[%d]", sceneIndex)
+		if err := index.ValidateRef(scene.SourceRef); err != nil {
 			issues = append(issues, prefix+".source_ref: "+diagnostics.Truncate(err.Error()))
 			continue
 		}
diff --git a/internal/modules/dnd/validate/spells/source_refs/validator.go b/internal/modules/dnd/validate/spells/source_refs/validator.go
index 7a1290a..e7bad43 100644
--- a/internal/modules/dnd/validate/spells/source_refs/validator.go
+++ b/internal/modules/dnd/validate/spells/source_refs/validator.go
@@ -36,10 +36,11 @@ func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationReq
 	if err := spellshape.Validate(req.Value); err != nil {
 		return contracts.ValidationResult{Approved: true}, nil
 	}
+	index := source.NewDocumentIndex(req.Source)
 	issues := make([]string, 0)
 	for spellIndex, spell := range req.Value.SpellCasts {
 		for refIndex, ref := range spell.SourceRefs {
-			if err := source.ValidateRef(req.Source, ref); err != nil {
+			if err := index.ValidateRef(ref); err != nil {
 				issues = append(issues, fmt.Sprintf("spell_casts[%d].source_refs[%d]: %s", spellIndex, refIndex, diagnostics.Truncate(err.Error())))
 			}
 		}