Index import dependencies for local scope scheduling

docs/internal/imports.md

@@ -72,6 +72,12 @@ tuple comparisons. On a stalled graph, deterministic DFS over the residual graph
 returns a closed cycle rotated to its smallest key; blocked dependents are not
 reported as cycle members.
 
+Import edge preparation builds an importer-to-target adjacency index once for
+an acquisition's outer and item-local scheduling, and once for grouped
+scheduling. Each scope gathers edges from its participating identities and
+retains only edges with both endpoints in its local slots. The retained
+inclusion graph still owns cycle diagnostics and source relationships.
+
 Import composition schedules a main tier or one underlay group as a single
 strict-scope graph. Applicable collection declarations are gathered for the
 scope before peer composition, including identity inherited from lower tiers.

docs/roadmap/remediation.md

@@ -152,7 +152,7 @@ and race-enabled import/destination tests passed with Go 1.26.10 on Linux.
 
 ## 3. Restrict Import-Scope Edge Preparation To Relevant Nodes
 
-Status: open. Priority: medium. Category: algorithmic efficiency and allocation
+Status: complete (2026-10-25). Priority: medium. Category: algorithmic efficiency and allocation
 scaling.
 
 **Evidence.** `scheduleAcquisitionScopes` in
@@ -190,3 +190,16 @@ coverage in [imports_test.go](../../internal/engine/imports_test.go) and
 existing destination/provenance evidence tests. Cover broad independent item
 scopes if a consequential gap remains; verify index construction and edge
 visitation bounds by source review without new performance gates.
+
+**Completion.** Scheduling now builds an importer-to-target adjacency index once
+for an acquisition and shares it across outer and pending item scopes. Grouped
+scheduling builds its own index once. Local preparation visits only adjacency
+lists for participating identities, includes only edges with both endpoints in
+the local slot map, and allocates edge storage as needed rather than reserving
+the whole graph per scope. For the broad sibling family, preparation is O(E + P)
+before the unchanged stable Kahn scheduling. The inclusion graph and cycle
+diagnostics remain unchanged. Tests cover excluded endpoints/unselected slots
+and broad main/underlay item scopes with retained helper origins and projected
+destinations. Focused scheduling tests, the development check, documentation
+links, and `go test -race ./...` passed with Go 1.26.10 on Linux. No timing or
+allocation thresholds were introduced.

internal/engine/dependency_integration_test.go

@@ -5,6 +5,29 @@ import (
 	"testing"
 )
 
+func TestImportSchedulingKeepsUnselectedSlotsAndScopeBoundaries(t *testing.T) {
+	dependent := importNodeKey{resourcePath: "a-dependent"}
+	external := importNodeKey{resourcePath: "external"}
+	prerequisite := importNodeKey{resourcePath: "z-prerequisite"}
+	graph := newImportInclusionGraph()
+	for _, key := range []importNodeKey{dependent, external, prerequisite} {
+		graph.addNode(importGraphNode{key: key})
+	}
+	graph.addEdge(dependent, prerequisite, Location{})
+	graph.addEdge(dependent, external, Location{})
+	graph.addEdge(external, prerequisite, Location{})
+	contributions := []acquiredContribution{
+		{identity: dependent}, {identity: external}, {identity: prerequisite},
+	}
+	scheduled := scheduleContributionSlots(contributions, []int{0, 2}, indexImportDependencies(graph))
+	if scheduled[0].identity != prerequisite || scheduled[1].identity != external || scheduled[2].identity != dependent {
+		t.Fatalf("scope schedule = %#v", scheduled)
+	}
+	if contributions[0].identity != dependent || contributions[2].identity != prerequisite {
+		t.Fatal("scheduling changed the input slots")
+	}
+}
+
 func TestImportAndInheritanceIntegrationsUseEquivalentReadySchedules(t *testing.T) {
 	names := []string{"a-base", "b-independent", "z-dependent"}
 	keys := make(map[string]importNodeKey, len(names))
@@ -33,7 +56,7 @@ func TestImportAndInheritanceIntegrationsUseEquivalentReadySchedules(t *testing.
 		}
 		graph.addEdge(keys["z-dependent"], keys["a-base"], Location{})
 
-		scheduled := scheduleContributionSlots(contributions, []int{0, 1, 2}, graph)
+		scheduled := scheduleContributionSlots(contributions, []int{0, 1, 2}, indexImportDependencies(graph))
 		got := make([]string, len(scheduled))
 		for index, contribution := range scheduled {
 			got[index] = contribution.identity.resourcePath[1:]

internal/engine/import_acquisition.go

@@ -178,7 +178,7 @@ func acquireImportedWithAccess(request importAcquisitionRequest, policy *acquisi
 		}
 	}
 	if len(diagnostics) == 0 {
-		state.scheduleAcquisitionScopes(&state.scope)
+		scheduleAcquisitionScopes(&state.scope, indexImportDependencies(state.importGraph))
 	}
 
 	closeErr := access.close()

internal/engine/import_graph.go

@@ -157,7 +157,20 @@ func (graph importInclusionGraph) scheduleCycle(closingEdge int, location Locati
 	}, true
 }
 
-func scheduleAcquisitionScope(scope acquisitionScope, graph importInclusionGraph) acquisitionScope {
+// importDependencyIndex is built once per scheduling operation and shared by
+// its scopes. Inclusion targets are grouped by importer, so local scheduling
+// need not scan or reserve storage for unrelated graph edges.
+type importDependencyIndex map[importNodeKey][]importNodeKey
+
+func indexImportDependencies(graph importInclusionGraph) importDependencyIndex {
+	index := make(importDependencyIndex)
+	for _, edge := range graph.edges {
+		index[edge.importer] = append(index[edge.importer], edge.imported)
+	}
+	return index
+}
+
+func scheduleAcquisitionScope(scope acquisitionScope, dependencies importDependencyIndex) acquisitionScope {
 	slots := make([]int, 0, len(scope.contributions))
 	for index, contribution := range scope.contributions {
 		if contribution.scopeOwner != scope.owner {
@@ -166,7 +179,7 @@ func scheduleAcquisitionScope(scope acquisitionScope, graph importInclusionGraph
 		slots = append(slots, index)
 	}
 	scheduled := scope
-	scheduled.contributions = scheduleContributionSlots(scope.contributions, slots, graph)
+	scheduled.contributions = scheduleContributionSlots(scope.contributions, slots, dependencies)
 	return scheduled
 }
 
@@ -179,10 +192,10 @@ func scheduleAcquisitionGroup(scopes []acquisitionScope, graph importInclusionGr
 	for index := range slots {
 		slots[index] = index
 	}
-	return acquisitionScope{contributions: scheduleContributionSlots(contributions, slots, graph)}
+	return acquisitionScope{contributions: scheduleContributionSlots(contributions, slots, indexImportDependencies(graph))}
 }
 
-func scheduleContributionSlots(contributions []acquiredContribution, slots []int, graph importInclusionGraph) []acquiredContribution {
+func scheduleContributionSlots(contributions []acquiredContribution, slots []int, dependencies importDependencyIndex) []acquiredContribution {
 	if len(slots) < 2 {
 		return append([]acquiredContribution(nil), contributions...)
 	}
@@ -193,14 +206,14 @@ func scheduleContributionSlots(contributions []acquiredContribution, slots []int
 		positions[contribution.identity] = position
 		keys[position] = contribution.identity.dependencyKey()
 	}
-	edges := make([]dependencyEdge, 0, len(graph.edges))
-	for _, edge := range graph.edges {
-		importer, importerOK := positions[edge.importer]
-		imported, importedOK := positions[edge.imported]
-		if importerOK && importedOK {
+	var edges []dependencyEdge
+	for importerKey, importer := range positions {
+		for _, importedKey := range dependencies[importerKey] {
+			if imported, exists := positions[importedKey]; exists {
 				edges = append(edges, dependencyEdge{prerequisite: imported, dependent: importer})
 			}
 		}
+	}
 	order, _ := scheduleDependencies(keys, edges)
 	if len(order) != len(keys) {
 		return append([]acquiredContribution(nil), contributions...)

internal/engine/imports.go

@@ -53,11 +53,11 @@ type importTraversal struct {
 	importGraph  importInclusionGraph
 }
 
-func (s *importTraversal) scheduleAcquisitionScopes(scope *acquisitionScope) {
-	*scope = scheduleAcquisitionScope(*scope, s.importGraph)
+func scheduleAcquisitionScopes(scope *acquisitionScope, dependencies importDependencyIndex) {
+	*scope = scheduleAcquisitionScope(*scope, dependencies)
 	for index := range scope.contributions {
 		if pending := scope.contributions[index].pendingItem; pending != nil {
-			s.scheduleAcquisitionScopes(pending)
+			scheduleAcquisitionScopes(pending, dependencies)
 		}
 	}
 }

internal/engine/imports_test.go

@@ -1107,6 +1107,70 @@ id: item
 	})
 }
 
+func TestBroadItemScopesKeepHelperOriginsAndDestinations(t *testing.T) {
+	t.Parallel()
+
+	type item struct {
+		ID    string `yaml:"id"`
+		Value string `yaml:"value"`
+	}
+	type config struct {
+		Items []item `yaml:"items"`
+	}
+	directory := t.TempDir()
+	const count = 32
+	var main strings.Builder
+	main.WriteString("configkit:\n  imports:\n")
+	for index := count - 1; index >= 0; index-- {
+		name := strconv.Itoa(100 + index)
+		main.WriteString("    - path: item-" + name + ".yml\n      destination: [items]\n      placement: sequence-item\n")
+		writeImportFile(t, directory, "item-"+name+".yml", "configkit: {imports: [{path: helper-"+name+".yml}]}\nid: item-"+name+"\n")
+		writeImportFile(t, directory, "helper-"+name+".yml", "value: helper-"+name+"\n")
+	}
+	mainPath := writeImportFile(t, directory, "main.yml", main.String())
+	definition := Definition[config]{sequenceIdentityRegistrations: []sequenceIdentityRegistration{{
+		selector: sequenceIdentitySelector{literalSequenceSelector("items")}, identityFields: []string{"id"},
+	}}}
+	for _, layered := range []bool{false, true} {
+		t.Run(strconv.FormatBool(layered), func(t *testing.T) {
+			var loaded *Loaded[config]
+			var err error
+			if layered {
+				loaded, err = LoadLayered(Input{Source: NoSource()}, testSecretBinding(), LayeredOptions[config]{
+					Definition: definition,
+					Underlays:  []Underlay{{Inputs: []Input{{Source: File(mainPath), Imports: true}}}},
+				})
+			} else {
+				loaded, err = Load(File(mainPath), testSecretBinding(), Options[config]{Imports: true, Definition: definition})
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			result := testLoaded(loaded)
+			sources := result.Sources()
+			if len(result.Config.Items) != count || len(sources) != 2*count+1 {
+				t.Fatalf("item/source counts = %d/%d", len(result.Config.Items), len(sources))
+			}
+			metadata := result.Metadata()
+			for index, record := range result.Config.Items {
+				name := strconv.Itoa(100 + index)
+				if record.ID != "item-"+name || record.Value != "helper-"+name {
+					t.Fatalf("item %d = %#v", index, record)
+				}
+				// Acquisition remains authored (descending); final item order is
+				// dependency-ready (ascending), with helper evidence reprojected.
+				helper := sources[2*(count-index)]
+				field, found := metadata.Lookup(Keys("items").Index(index).Key("value"))
+				if !found || len(field.Origin.Locations) != 1 || field.Origin.Locations[0].SourceID != helper.ID ||
+					helper.Path != canonicalTestPath(t, filepath.Join(directory, "helper-"+name+".yml")) ||
+					helper.Destination.String() != Keys("items").Index(index).String() {
+					t.Fatalf("item %d helper evidence = %#v, %#v", index, field, helper)
+				}
+			}
+		})
+	}
+}
+
 func TestItemHelperScopeScheduleInterleavesUnequalBranches(t *testing.T) {
 	directory := t.TempDir()
 	mainPath := writeImportFile(t, directory, "main.yml", `configkit: