Reuse origin metadata across configuration collections

docs/internal/sources.md

@@ -82,6 +82,9 @@ declaration; absent and null fields remain distinguishable from explicit
 strings, including empty strings. It closes content-file handles before
 returning and retains no source capability for public inspection.
 
+Prompt materialization shares a lazy metadata snapshot across root and collection
+resources during construction, avoiding a full metadata copy per collection.
+
 Role and cache-control normalization is applied to execution-owned message
 copies. ConfigKit v0.8.0 retains effective input message metadata and its
 resource origins; recording a sequence-wide normalization in the retained

docs/roadmap/remediation.md

@@ -1,6 +1,6 @@
 # Configuration Collections Implementation Review Findings
 
-Status: three findings open. Review completed 2026-10-17.
+Status: Finding 1 completed; Findings 2–3 open. Review completed 2026-10-17.
 
 Reviewed implementation after `89af2a1` through `0221cd4` against the accepted
 [feature roadmap](configuration-collections.md), [implementation plan](implementation.md),
@@ -35,7 +35,7 @@ addresses a retained public guarantee that no longer describes scoped views.
 
 ## Finding 1: Share Origin Metadata Across Collection Materialization
 
-Priority: P2. Status: open.
+Priority: P2. Status: completed 2026-10-17.
 
 Locations: [load.go](../../internal/configuration/load.go), lines 257–262, and
 [materializePrompts](../../internal/configuration/prompts.go), lines 84–95.
@@ -78,6 +78,15 @@ one file-backed collection, and use a small scaling benchmark to verify the
 repeated full-snapshot cost is removed. Do not make exact allocations, elapsed
 times, or private helper call order a new contract.
 
+Completion: prompt materialization now traverses root and collection resources
+within one construction-scoped pass sharing the lazy origin metadata snapshot.
+Extended the imported/inherited-content test across distinct collection resource
+contexts and added a scaling benchmark without allocation or timing assertions.
+At 64 collections the same benchmark dropped from 104,574,200 to 21,239,712
+allocated bytes per construction in single-iteration local measurements.
+Validation passed: focused origin tests and benchmark, race-enabled configuration
+and public API tests, configuration vet, and `git diff --check`.
+
 ## Finding 2: Detach The Optional Label In Internal Prepared Snapshots
 
 Priority: P3. Status: open.

internal/configuration/benchmark_test.go

@@ -126,6 +126,40 @@ func layeredDefinitions(count int) configurationShape {
 	}
 }
 
+func BenchmarkCollectionFileBackedConstruction(b *testing.B) {
+	for _, count := range []int{4, 16, 64} {
+		b.Run(fmt.Sprintf("collections_%d", count), func(b *testing.B) {
+			collections := make(map[string]any, count)
+			for index := range count {
+				collections[fmt.Sprintf("collection-%03d", index)] = map[string]any{
+					"prompts": map[string]any{
+						"example": map[string]any{
+							"messages": []any{map[string]any{"role": "user", "content_file": "body.md"}},
+							"output":   map[string]any{"format": "text", "validation_mode": "none"},
+						},
+					},
+				}
+			}
+			namespace := configkit.NewFilesystem("collection benchmark", fstest.MapFS{
+				"body.md": {Data: []byte("Hello")},
+			})
+			main := configkit.Input{
+				Source:     configkit.Mapping("collections", map[string]any{"collections": collections}),
+				Filesystem: &configkit.FilesystemContext{FS: &namespace, Root: ".", BaseDir: "."},
+			}
+			b.ReportAllocs()
+			for b.Loop() {
+				result, err := load(main, nil)
+				if err != nil {
+					b.Fatal(err)
+				}
+				constructionResult = result
+			}
+			b.ReportMetric(float64(count), "collections/op")
+		})
+	}
+}
+
 func BenchmarkConfigurationConstruction(b *testing.B) {
 	for _, scenario := range []struct {
 		name  string

internal/configuration/load.go

@@ -255,10 +255,8 @@ func load(main configkit.Input, underlays []configkit.Underlay) (*loaded, error)
 		return nil, fmt.Errorf("load configuration: %w", err)
 	}
 	state.result = result
-	for _, resources := range resourceSets(&result.Config) {
-		if err := state.materializePrompts(resources.prompts, resources.bases.prompts, resources.namespace); err != nil {
-			return nil, fmt.Errorf("load configuration: %w", err)
-		}
+	if err := state.materializePrompts(); err != nil {
+		return nil, fmt.Errorf("load configuration: %w", err)
 	}
 	if err := state.buildExecutionProfiles(); err != nil {
 		return nil, fmt.Errorf("load configuration: %w", err)

internal/configuration/prompts.go

@@ -81,10 +81,8 @@ func resolvePrompts(prompts map[string]promptConfig, basePath configkit.Path, re
 	}
 }
 
-func (state *loaded) materializePrompts(prompts map[string]promptConfig, basePath configkit.Path, namespace string) error {
-	if state.prompts == nil {
-		state.prompts = make(map[string]*promptEntry)
-	}
+func (state *loaded) materializePrompts() error {
+	state.prompts = make(map[string]*promptEntry)
 	var metadata *configkit.Metadata
 	lookupOrigin := func(path configkit.Path) (configkit.FieldInfo, bool) {
 		if metadata == nil {
@@ -93,17 +91,20 @@ func (state *loaded) materializePrompts(prompts map[string]promptConfig, basePat
 		}
 		return metadata.Lookup(path)
 	}
-	for _, id := range sortedKeys(prompts) {
-		promptBase := basePath.Key(id)
-		if strings.TrimSpace(id) == "" {
-			return fmt.Errorf("%s: prompt ID must not be blank", promptBase)
+	for _, resources := range resourceSets(&state.result.Config) {
+		for _, id := range sortedKeys(resources.prompts) {
+			promptBase := resources.bases.prompts.Key(id)
+			if strings.TrimSpace(id) == "" {
+				return fmt.Errorf("%s: prompt ID must not be blank", promptBase)
+			}
+			fullID := indexedResourceID(resources.namespace, id)
+			raw := resources.prompts[id]
+			entry, err := state.materializePrompt(fullID, raw.Version, raw, promptBase, lookupOrigin)
+			if err != nil {
+				return err
+			}
+			state.prompts[fullID] = entry
 		}
-		fullID := indexedResourceID(namespace, id)
-		entry, err := state.materializePrompt(fullID, prompts[id].Version, prompts[id], promptBase, lookupOrigin)
-		if err != nil {
-			return err
-		}
-		state.prompts[fullID] = entry
 	}
 	return nil
 }

internal/configuration/prompts_test.go

@@ -16,9 +16,11 @@ import (
 
 func TestLoadCapturesInheritedImportedContent(t *testing.T) {
 	files := fstest.MapFS{
-		"app/main.yaml":     {Data: []byte("configkit:\n  imports:\n    - path: ../catalog/base.yaml\ncollections:\n  docs:\n    prompts:\n      child:\n        extends: base\n")},
-		"catalog/base.yaml": {Data: []byte("collections:\n  docs:\n    release_version: r1\n    prompts:\n      base:\n        version: \"v1\"\n        messages:\n          - role: ' USER '\n            cache_control:\n              type: ' ephemeral '\n              ttl: ' 1h '\n            content_file: ./body.md\n        output:\n          format: text\n          validation_mode: basic\n")},
-		"catalog/body.md":   {Data: []byte("Captured {{.name}}")},
+		"app/main.yaml":         {Data: []byte("configkit:\n  imports:\n    - path: ../catalog/base.yaml\n    - path: ../other/definition.yaml\ncollections:\n  docs:\n    prompts:\n      child:\n        extends: base\n")},
+		"catalog/base.yaml":     {Data: []byte("collections:\n  docs:\n    release_version: r1\n    prompts:\n      base:\n        version: \"v1\"\n        messages:\n          - role: ' USER '\n            cache_control:\n              type: ' ephemeral '\n              ttl: ' 1h '\n            content_file: ./body.md\n        output:\n          format: text\n          validation_mode: basic\n")},
+		"catalog/body.md":       {Data: []byte("Captured {{.name}}")},
+		"other/definition.yaml": {Data: []byte("collections:\n  other:\n    prompts:\n      child:\n        messages:\n          - role: user\n            content_file: ./body.md\n        output:\n          format: text\n          validation_mode: none\n")},
+		"other/body.md":         {Data: []byte("Other collection {{.name}}")},
 	}
 	namespace := configkit.NewFilesystem("embedded", files)
 	state, err := load(configkit.Input{
@@ -56,7 +58,12 @@ func TestLoadCapturesInheritedImportedContent(t *testing.T) {
 	if originPath != "catalog/base.yaml" {
 		t.Fatalf("content origin = %q, want catalog/base.yaml", originPath)
 	}
+	other, otherInspection, err := state.prompt("other/child")
+	if err != nil || other.Templates[0].Content != "Other collection {{.name}}" {
+		t.Fatalf("other collection did not retain its source context: %+v, %v", other, err)
+	}
 	files["catalog/body.md"].Data = []byte("Changed")
+	files["other/body.md"].Data = []byte("Changed other collection")
 	again, againInspection, err := state.prompt("docs/child")
 	if err != nil || again.Templates[0].Content != "Captured {{.name}}" || againInspection.PromptHash != inspection.PromptHash {
 		t.Fatalf("captured definition changed after source mutation: %+v, %+v, %v", again, againInspection, err)
@@ -66,6 +73,10 @@ func TestLoadCapturesInheritedImportedContent(t *testing.T) {
 	if err != nil || third.Templates[0].Content != "Captured {{.name}}" {
 		t.Fatalf("caller mutation escaped into index: %+v, %v", third, err)
 	}
+	otherAgain, otherAgainInspection, err := state.prompt("other/child")
+	if err != nil || otherAgain.Templates[0].Content != "Other collection {{.name}}" || otherAgainInspection.PromptHash != otherInspection.PromptHash {
+		t.Fatalf("other captured definition changed after source mutation: %+v, %+v, %v", otherAgain, otherAgainInspection, err)
+	}
 }
 
 func TestLoadUsesExplicitMappingContextAndClosesContent(t *testing.T) {