Rename selected configuration profiles to overlays

2026-09-23 18:27:29 +00:00
parent 66e080ed34
commit ae91f57bbe
32 changed files with 306 additions and 283 deletions
--- a/internal/engine/directives.go
+++ b/internal/engine/directives.go
@@ -181,24 +181,24 @@ func nodeImportDiagnostic(code Code, path Path, message string, node *document.N
 	return Diagnostic{Code: code, Severity: SeverityError, Path: path, Message: message, Primary: &location}
 }

-func profileDirectiveDiagnostics(node *document.Node, current Path) []Diagnostic {
+func overlayDirectiveDiagnostics(node *document.Node, current Path) []Diagnostic {
 	if node.Kind == document.Mapping {
 		for _, entry := range node.Mapping {
 			childPath := current.Key(entry.Key)
 			if entry.Key == directiveKey {
 				location := publicLocation(entry.KeyLocation)
 				return []Diagnostic{{
-					Code: CodeProfileDirective, Severity: SeverityError, Path: childPath,
-					Message: "profiles cannot contain configuration directives", Primary: &location,
+					Code: CodeOverlayDirective, Severity: SeverityError, Path: childPath,
+					Message: "overlays cannot contain configuration directives", Primary: &location,
 				}}
 			}
-			if diagnostics := profileDirectiveDiagnostics(entry.Value, childPath); len(diagnostics) != 0 {
+			if diagnostics := overlayDirectiveDiagnostics(entry.Value, childPath); len(diagnostics) != 0 {
 				return diagnostics
 			}
 		}
 	} else if node.Kind == document.Sequence {
 		for index, child := range node.Sequence {
-			if diagnostics := profileDirectiveDiagnostics(child, current.Index(index)); len(diagnostics) != 0 {
+			if diagnostics := overlayDirectiveDiagnostics(child, current.Index(index)); len(diagnostics) != 0 {
 				return diagnostics
 			}
 		}
--- a/internal/engine/explain_render.go
+++ b/internal/engine/explain_render.go
@@ -38,7 +38,7 @@ func (r *Inspection) WriteExplanation(output io.Writer, path Path) error {
 		rendered.WriteString("  - representation: ")
 		if change.Origin.Operation == ChangeDecoding {
 			rendered.WriteString("input to canonical typed\n")
-		} else if change.Origin.Layer == LayerBase || change.Origin.Layer == LayerProfile || change.Origin.Layer == LayerCLI {
+		} else if change.Origin.Layer == LayerBase || change.Origin.Layer == LayerOverlay || change.Origin.Layer == LayerCLI {
 			rendered.WriteString("policy-validated input\n")
 		} else {
 			rendered.WriteString("canonical typed\n")
--- a/internal/engine/explain_test.go
+++ b/internal/engine/explain_test.go
@@ -21,13 +21,13 @@ type explanationConcurrency struct {
 	} `yaml:"transcription"`
 }

-func TestExplainShowsDefaultBaseAndEffectiveProfileValue(t *testing.T) {
+func TestExplainShowsDefaultBaseAndEffectiveOverlayValue(t *testing.T) {
 	directory := t.TempDir()
 	mainPath := writeImportFile(t, directory, "config.yml", "configkit:\n  imports: [{path: transcription.yml}]\n")
 	writeImportFile(t, directory, "transcription.yml", "transcription:\n  concurrency: 8\n")
-	writeImportFile(t, directory, filepath.Join("profiles", "testing.yml"), "transcription:\n  concurrency: 1\n")
+	writeImportFile(t, directory, filepath.Join("overlays", "testing.yml"), "transcription:\n  concurrency: 1\n")
 	result, err := testLoad[explanationConcurrency](File(mainPath), Options[explanationConcurrency]{
-		Imports: true, Profile: "testing",
+		Imports: true, Overlay: "testing",
 		Definition: Definition[explanationConcurrency]{Defaults: func() explanationConcurrency {
 			value := explanationConcurrency{}
 			value.Transcription.Concurrency = 4
@@ -44,7 +44,7 @@ func TestExplainShowsDefaultBaseAndEffectiveProfileValue(t *testing.T) {
 	if got := explanationValues(explanation); !reflect.DeepEqual(got, []string{"4\n", "8\n", "1\n"}) {
 		t.Fatalf("history values = %#v", got)
 	}
-	if explanation.Effective.YAML != "1\n" || explanation.Origin.Layer != LayerProfile ||
+	if explanation.Effective.YAML != "1\n" || explanation.Origin.Layer != LayerOverlay ||
 		len(explanation.Origin.Locations) != 1 || explanation.Origin.Locations[0].SourceID != "source-3" ||
 		explanation.Origin.Locations[0].Line != 2 {
 		t.Fatalf("effective explanation = %#v", explanation)
@@ -70,18 +70,18 @@ func TestExplainReplaysCLIResolutionContainersAndSafeHistoricalValues(t *testing
 	directory := t.TempDir()
 	mainPath := writeImportFile(t, directory, "config.yml", `concurrency: 8
 equal: same
-limit: wrong-before-profile
+limit: wrong-before-overlay
 items: [base, removed]
 labels: {base: retained}
 dynamic: {retired: HISTORICAL_EXPLAIN_CANARY, public: visible}
 credential: APP_SECRET
 classified: APP_SECRET
 `)
-	writeImportFile(t, directory, filepath.Join("profiles", "testing.yml"), `concurrency: 1
+	writeImportFile(t, directory, filepath.Join("overlays", "testing.yml"), `concurrency: 1
 equal: same
 limit: 7
-items: [profile]
-labels: {profile: retained}
+items: [overlay]
+labels: {overlay: retained}
 dynamic: selected
 `)
 	result, err := testLoadWithSecretLookup(File(mainPath), func(name string) (string, bool) {
@@ -90,7 +90,7 @@ dynamic: selected
 		}
 		return "RESOLVED_EXPLAIN_CANARY", true
 	}, Options[explanationConfig]{
-		Profile: "testing",
+		Overlay: "testing",
 		Overrides: []Override{
 			{Path: Keys("concurrency"), Value: 2, Flag: "--concurrency"},
 			{Path: Keys("equal"), Value: "same", Flag: "--equal"},
@@ -130,7 +130,7 @@ dynamic: selected
 	if got := explanationValues(concurrency); !reflect.DeepEqual(got, []string{"4\n", "8\n", "1\n", "2\n", "3\n"}) {
 		t.Fatalf("concurrency history = %#v", got)
 	}
-	if got := historyValueLayers(concurrency); !reflect.DeepEqual(got, []Layer{LayerDefault, LayerBase, LayerProfile, LayerCLI, LayerResolution}) {
+	if got := historyValueLayers(concurrency); !reflect.DeepEqual(got, []Layer{LayerDefault, LayerBase, LayerOverlay, LayerCLI, LayerResolution}) {
 		t.Fatalf("concurrency layers = %#v", got)
 	}
 	if concurrency.History[4].Before.YAML != "2\n" || concurrency.History[4].Reasons[0] != "normalized\nconcurrency" ||
@@ -149,7 +149,7 @@ dynamic: selected
 	}

 	limit, _ := result.Explain(Keys("limit"))
-	if got := explanationValues(limit); !reflect.DeepEqual(got, []string{"0\n", "wrong-before-profile\n", "7\n"}) {
+	if got := explanationValues(limit); !reflect.DeepEqual(got, []string{"0\n", "wrong-before-overlay\n", "7\n"}) {
 		t.Fatalf("overridden invalid input was not retained: %#v", got)
 	}
 	removed, ok := result.Explain(Keys("dynamic", "retired"))
@@ -182,7 +182,7 @@ dynamic: selected
 	}
 	labels, _ := result.Explain(Keys("labels"))
 	if len(labels.History) != 4 || !strings.Contains(labels.Effective.YAML, "default: retained") ||
-		!strings.Contains(labels.Effective.YAML, "profile: retained") || !strings.Contains(labels.Effective.YAML, "cli: retained") {
+		!strings.Contains(labels.Effective.YAML, "overlay: retained") || !strings.Contains(labels.Effective.YAML, "cli: retained") {
 		t.Fatalf("composite mapping history = %#v", labels)
 	}
 	if labels.Origin.Layer != LayerCLI || len(labels.Origin.Locations) != 3 {
@@ -258,7 +258,7 @@ dynamic: selected
 	var invalidInput bytes.Buffer
 	if err := result.WriteExplanation(&invalidInput, Keys("limit")); err != nil ||
 		!strings.Contains(invalidInput.String(), "policy-validated input") ||
-		strings.Contains(invalidInput.String(), "wrong-before-profile\n    source: layer=\"base\"\n    before (canonical typed)") {
+		strings.Contains(invalidInput.String(), "wrong-before-overlay\n    source: layer=\"base\"\n    before (canonical typed)") {
 		t.Fatalf("historical representation rendering = %v\n%s", err, invalidInput.String())
 	}
 }
@@ -340,8 +340,8 @@ func TestExplanationReconcilesDefaultsAfterInputReplacement(t *testing.T) {
 				if cli {
 					opts.Overrides = []Override{{Path: Keys("m"), Value: map[string]any{"b": 2}, Flag: "--m"}}
 				} else {
-					writeImportFile(t, root, "profiles/p.yml", "m: {b: 2}\n")
-					opts.Profile = "p"
+					writeImportFile(t, root, "overlays/p.yml", "m: {b: 2}\n")
+					opts.Overlay = "p"
 				}
 				result, err := testLoad(File(main), opts)
 				if err != nil {
--- a/internal/engine/glob_test.go
+++ b/internal/engine/glob_test.go
@@ -229,11 +229,11 @@ func TestGlobTraversalBoundsNonmatchesAndAcceptedCandidates(t *testing.T) {
 	}
 }

-func TestFilesystemContextIsValidatedWithoutImportsOrActiveProfile(t *testing.T) {
+func TestFilesystemContextIsValidatedWithoutImportsOrActiveOverlay(t *testing.T) {
 	directory := t.TempDir()
 	mainPath := writeImportFile(t, directory, "main.yml", "items: {root: root}\n")
 	result, err := testLoad[importTestConfig](File(mainPath), Options[importTestConfig]{
-		Profile: "default", Filesystem: &FilesystemContext{Root: directory},
+		Overlay: "default", Filesystem: &FilesystemContext{Root: directory},
 	})
 	if err != nil || result.Config.Items["root"] != "root" {
 		t.Fatalf("file filesystem context = %#v, %v", result, err)
@@ -247,9 +247,9 @@ func TestFilesystemContextIsValidatedWithoutImportsOrActiveProfile(t *testing.T)
 		t.Fatalf("byte filesystem context = %#v, %v", result, err)
 	}
 	requireLoadCode(t, Bytes("memory.yml", []byte("{}\n")), Options[importTestConfig]{Filesystem: &FilesystemContext{BaseDir: directory}}, CodeOptionsInvalid)
-	defaultsOnly, err := testLoad[importTestConfig](NoSource(), Options[importTestConfig]{Profile: "default"})
+	defaultsOnly, err := testLoad[importTestConfig](NoSource(), Options[importTestConfig]{Overlay: "default"})
 	if err != nil || defaultsOnly == nil {
-		t.Fatalf("default profile with NoSource = %#v, %v", defaultsOnly, err)
+		t.Fatalf("default overlay with NoSource = %#v, %v", defaultsOnly, err)
 	}

 	if runtime.GOOS == "linux" || runtime.GOOS == "darwin" {
--- a/internal/engine/load.go
+++ b/internal/engine/load.go
@@ -19,17 +19,17 @@ type Definition[T any] struct {
 }

 // Options contains the application definition and per-load input selections.
-// Imports enables explicit path and glob imports; Profile selects one fixed profile
-// overlay; Overrides contains only values explicitly supplied by an application CLI.
+// Imports enables explicit path and glob imports; Overlay selects one fixed overlay;
+// Overrides contains only values explicitly supplied by an application CLI.
 type Options[T any] struct {
 	Definition Definition[T]
 	Imports    bool
-	Profile    string
+	Overlay    string
 	Filesystem *FilesystemContext
 	Overrides  []Override
 }

-// FilesystemContext supplies filesystem roots for imports and profiles.
+// FilesystemContext supplies filesystem roots for imports and overlays.
 type FilesystemContext struct {
 	BaseDir string
 	Root    string
@@ -113,7 +113,7 @@ func (r *Inspection) Diagnostics() []Diagnostic {
 }

 // Load parses and strictly decodes zero or one selected source, explicitly enabled
-// imports, and one selected profile. It accepts at most one Options value and
+// imports, and one selected overlay. It accepts at most one Options value and
 // returns no result when any error is reported.
 func Load[T any](source Source, secrets SecretBinding, supplied ...Options[T]) (*Loaded[T], error) {
 	return loadWithSecretLookup(source, secrets, os.LookupEnv, supplied...)
--- a/internal/engine/load_input.go
+++ b/internal/engine/load_input.go
@@ -25,7 +25,7 @@ func assembleBaseInput[T any](source Source, options Options[T]) (assembledInput
 		input.document = input.composition.root
 	} else {
 		input.sources = sourceInfos(parsed.source)
-		if options.Filesystem != nil && !activeProfile(options.Profile) {
+		if options.Filesystem != nil && !activeOverlay(options.Overlay) {
 			if diagnostic := validateFilesystemContext(source, options.Filesystem, parsed); diagnostic != nil {
 				return input, []Diagnostic{*diagnostic}
 			}
@@ -40,17 +40,17 @@ func assembleBaseInput[T any](source Source, options Options[T]) (assembledInput
 }

 func applyInputLayers[T any](source Source, options Options[T], input assembledInput) (assembledInput, []Diagnostic) {
-	if !activeProfile(options.Profile) && len(options.Overrides) == 0 {
+	if !activeOverlay(options.Overlay) && len(options.Overrides) == 0 {
 		return input, nil
 	}
 	composition, diagnostics := compositionForInput(input)
 	if len(diagnostics) != 0 {
 		return input, diagnostics
 	}
-	if activeProfile(options.Profile) {
-		composition, input.sources, diagnostics = loadProfileDocument(
+	if activeOverlay(options.Overlay) {
+		composition, input.sources, diagnostics = loadSelectedOverlayDocument(
 			source, options.Filesystem, input.parsed, composition, input.sources,
-			options.Profile, options.Definition.Version, defaultImportLimits(),
+			options.Overlay, options.Definition.Version, defaultImportLimits(),
 		)
 		if len(diagnostics) != 0 {
 			return input, diagnostics
@@ -69,7 +69,7 @@ func applyInputLayers[T any](source Source, options Options[T], input assembledI
 	return input, nil
 }

-// compositionForInput initializes one handoff for profiles and CLI, including
+// compositionForInput initializes one handoff for overlays and CLI, including
 // defaults-only CLI input. Raw source bytes and mapping keys retain their budgets.
 func compositionForInput(input assembledInput) (*composedDocument, []Diagnostic) {
 	if input.composition != nil {
--- a/internal/engine/metadata_test.go
+++ b/internal/engine/metadata_test.go
@@ -60,8 +60,8 @@ func TestHistoricalPathsExposeHiddenBaseOwnershipWithoutResolvingBaseSecrets(t *
 			root := writeImportFile(t, dir, "main.yml", "configkit:\n  imports: [{path: first.yml}, {path: second.yml}]\ncredential: CONFIGKIT_HISTORY_UNUSED_PROD_KEY\n")
 			writeImportFile(t, dir, "first.yml", "definitions: {recap: {prompt: recap}}\n")
 			writeImportFile(t, dir, "second.yml", "definitions: {recap: {output: recap.md}}\n")
-			writeImportFile(t, dir, "profiles/testing.yml", "definitions: null\ncredential: "+credential+"\n")
-			result, err := testLoad[config](File(root), Options[config]{Imports: true, Profile: "testing"})
+			writeImportFile(t, dir, "overlays/testing.yml", "definitions: null\ncredential: "+credential+"\n")
+			result, err := testLoad[config](File(root), Options[config]{Imports: true, Overlay: "testing"})
 			if err != nil {
 				t.Fatal(err)
 			}
--- a/internal/engine/options.go
+++ b/internal/engine/options.go
@@ -10,8 +10,8 @@ func selectOptions[T any](source Source, supplied []Options[T]) (Options[T], []D
 	}
 	var diagnostics []Diagnostic
 	definition := options.Definition
-	if !validProfileName(options.Profile) {
-		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "profile name must contain only ASCII letters, digits, underscore, or hyphen"))
+	if !validOverlayName(options.Overlay) {
+		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "overlay name must contain only ASCII letters, digits, underscore, or hyphen"))
 	}
 	if options.Filesystem != nil {
 		diagnostics = append(diagnostics, filesystemOptionDiagnostics(source, options.Filesystem)...)
@@ -19,11 +19,11 @@ func selectOptions[T any](source Source, supplied []Options[T]) (Options[T], []D
 	if source.kind == sourceNone && options.Imports {
 		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "NoSource cannot enable imports"))
 	}
-	if source.kind == sourceNone && options.Profile != "" && options.Profile != "default" {
-		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "NoSource cannot select an active profile"))
+	if source.kind == sourceNone && options.Overlay != "" && options.Overlay != "default" {
+		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "NoSource cannot select an active overlay"))
 	}
-	if options.Filesystem == nil && (source.kind == sourceBytes || source.kind == sourceReader) && (options.Imports || activeProfile(options.Profile)) {
-		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "byte and reader imports or profiles require filesystem context"))
+	if options.Filesystem == nil && (source.kind == sourceBytes || source.kind == sourceReader) && (options.Imports || activeOverlay(options.Overlay)) {
+		diagnostics = append(diagnostics, optionDiagnostic(CodeOptionsInvalid, "byte and reader imports or overlays require filesystem context"))
 	}
 	if definition.Version != nil {
 		if !definition.Version.Path.valid() {
--- a/internal/engine/overlay.go
+++ b/internal/engine/overlay.go
@@ -20,14 +20,14 @@ type displacedDefinition struct {
 func overlayDocuments(base *composedDocument, overlay *document.Node) (*composedDocument, []Diagnostic) {
 	if base == nil || base.root == nil || base.root.Kind != document.Mapping || overlay == nil || overlay.Kind != document.Mapping {
 		return nil, []Diagnostic{{
-			Code: CodeProfileInvalid, Severity: SeverityError,
-			Message: "profile overlay requires mapping document roots",
+			Code: CodeOverlayInvalid, Severity: SeverityError,
+			Message: "overlay overlay requires mapping document roots",
 		}}
 	}
 	result := cloneComposedDocument(base)
-	mergeOverlayOrigin(result.origins, Path{}, overlay.Location, LayerProfile)
-	mergeOverlayMappings(result, result.root, overlay, Path{}, LayerProfile, true)
-	result.applications = append(result.applications, historyApplication{layer: LayerProfile, value: overlay})
+	mergeOverlayOrigin(result.origins, Path{}, overlay.Location, LayerOverlay)
+	mergeOverlayMappings(result, result.root, overlay, Path{}, LayerOverlay, true)
+	result.applications = append(result.applications, historyApplication{layer: LayerOverlay, value: overlay})
 	return result, nil
 }

--- a/internal/engine/overlay_test.go
+++ b/internal/engine/overlay_test.go
@@ -22,7 +22,7 @@ to_scalar: {child: old}
 	}
 	overlay := parseCompositionDocument(t, "source-2", `shared:
  changed: new
-  added: profile
+  added: overlay
 sequence: []
 nullable: null
 to_map: {child: new}
@@ -42,7 +42,7 @@ to_scalar: scalar
 	}{
 		{path: Keys("shared", "kept"), kind: document.String, text: "base"},
 		{path: Keys("shared", "changed"), kind: document.String, text: "new"},
-		{path: Keys("shared", "added"), kind: document.String, text: "profile"},
+		{path: Keys("shared", "added"), kind: document.String, text: "overlay"},
 		{path: Keys("sequence"), kind: document.Sequence},
 		{path: Keys("nullable"), kind: document.Null},
 		{path: Keys("to_map"), kind: document.Mapping},
@@ -62,7 +62,7 @@ to_scalar: scalar
 		t.Fatal("parent replacement retained a stale child origin")
 	}
 	shared := result.origins["/shared"]
-	if shared.Layer != LayerProfile || len(shared.Locations) != 2 {
+	if shared.Layer != LayerOverlay || len(shared.Locations) != 2 {
 		t.Fatalf("shared mapping origin = %#v", shared)
 	}
 	if len(result.overlays) != 5 {
--- a/internal/engine/override_test.go
+++ b/internal/engine/override_test.go
@@ -41,9 +41,9 @@ func TestOverridesRunAtHighestInputPrecedenceBeforeResolutionAndValidation(t *te
  labels: {base: retained}
  api_key: BASE_SECRET
 `)
-	writeImportFile(t, directory, filepath.Join("profiles", "testing.yml"), `settings:
-  target: profile
-  labels: {profile: retained}
+	writeImportFile(t, directory, filepath.Join("overlays", "testing.yml"), `settings:
+  target: overlay
+  labels: {overlay: retained}
 `)
 	validated := false
 	overrides := []Override{
@@ -62,7 +62,7 @@ func TestOverridesRunAtHighestInputPrecedenceBeforeResolutionAndValidation(t *te
 		}
 		return "credential-value", true
 	}, Options[overrideLifecycleConfig]{
-		Imports: true, Profile: "testing", Overrides: overrides,
+		Imports: true, Overlay: "testing", Overrides: overrides,
 		Definition: Definition[overrideLifecycleConfig]{
 			Defaults: func() overrideLifecycleConfig {
 				return overrideLifecycleConfig{Settings: overrideLifecycleSettings{Target: "default", Count: 9, Text: "default", Items: []string{"default"}}}
@@ -86,7 +86,7 @@ func TestOverridesRunAtHighestInputPrecedenceBeforeResolutionAndValidation(t *te
 		t.Fatalf("testLoadWithSecretLookup() error = %v", err)
 	}
 	want := overrideLifecycleSettings{
-		Target: "cli", Labels: map[string]string{"base": "retained", "profile": "retained", "cli": "selected"},
+		Target: "cli", Labels: map[string]string{"base": "retained", "overlay": "retained", "cli": "selected"},
 		APIKey: result.Config.Settings.APIKey,
 	}
 	if !validated || result.Config.Settings.Count != 0 || result.Config.Settings.Enabled || result.Config.Settings.Text != "" ||
@@ -95,7 +95,7 @@ func TestOverridesRunAtHighestInputPrecedenceBeforeResolutionAndValidation(t *te
 		t.Fatalf("effective settings = %#v", result.Config.Settings)
 	}
 	sources := result.Sources()
-	if len(sources) != 3+len(overrides) || sources[0].Layer != LayerBase || sources[1].Layer != LayerBase || sources[2].Layer != LayerProfile {
+	if len(sources) != 3+len(overrides) || sources[0].Layer != LayerBase || sources[1].Layer != LayerBase || sources[2].Layer != LayerOverlay {
 		t.Fatalf("sources = %#v", sources)
 	}
 	for index, override := range overrides {
@@ -104,7 +104,7 @@ func TestOverridesRunAtHighestInputPrecedenceBeforeResolutionAndValidation(t *te
 		}
 	}
 	history := result.Metadata().History(Keys("settings", "target"))
-	wantLayers := []Layer{LayerDefault, LayerBase, LayerProfile, LayerCLI, LayerResolution}
+	wantLayers := []Layer{LayerDefault, LayerBase, LayerOverlay, LayerCLI, LayerResolution}
 	if got := historyLayers(history); !reflect.DeepEqual(got, wantLayers) {
 		t.Fatalf("target history layers = %#v, want %#v; history %#v", got, wantLayers, history)
 	}
--- a/internal/engine/provenance_test.go
+++ b/internal/engine/provenance_test.go
@@ -16,7 +16,7 @@ type layeredConfig struct {
 	Shared struct {
 		Equal    string `yaml:"equal"`
 		Imported string `yaml:"imported"`
-		Profile  string `yaml:"profile"`
+		Overlay  string `yaml:"overlay"`
 	} `yaml:"shared"`
 	Values   []int                  `yaml:"values"`
 	Items    map[string]layeredItem `yaml:"items"`
@@ -40,7 +40,7 @@ nullable: base
 empty: {}
 `)
 	importPath := writeImportFile(t, directory, "imported.yml", "shared: {imported: base}\n")
-	profilePath := writeImportFile(t, directory, "profiles/testing.yml", `shared: {profile: selected}
+	overlayPath := writeImportFile(t, directory, "overlays/testing.yml", `shared: {overlay: selected}
 values: [3, 4]
 value: selected
 nullable: null
@@ -71,23 +71,23 @@ empty: {}
 	}

 	result, err := testLoad[layeredConfig](File(mainPath), Options[layeredConfig]{
-		Imports: true, Profile: "testing", Definition: definition,
+		Imports: true, Overlay: "testing", Definition: definition,
 	})
 	if err != nil {
 		var loadError *LoadError
 		_ = errors.As(err, &loadError)
 		t.Fatalf("%v: %#v", err, loadError.Diagnostics())
 	}
-	wantSources := []string{canonicalTestPath(t, mainPath), canonicalTestPath(t, importPath), canonicalTestPath(t, profilePath)}
+	wantSources := []string{canonicalTestPath(t, mainPath), canonicalTestPath(t, importPath), canonicalTestPath(t, overlayPath)}
 	sources := result.Sources()
 	gotSources := make([]string, len(sources))
 	for index, source := range sources {
 		gotSources[index] = source.Path
 	}
-	if !reflect.DeepEqual(gotSources, wantSources) || sources[2].Layer != LayerProfile {
+	if !reflect.DeepEqual(gotSources, wantSources) || sources[2].Layer != LayerOverlay {
 		t.Fatalf("sources = %#v", sources)
 	}
-	if result.Config.Shared.Equal != "same" || result.Config.Shared.Imported != "base" || result.Config.Shared.Profile != "selected" ||
+	if result.Config.Shared.Equal != "same" || result.Config.Shared.Imported != "base" || result.Config.Shared.Overlay != "selected" ||
 		!reflect.DeepEqual(result.Config.Values, []int{5}) || result.Config.Nullable != nil || result.Config.Derived != 7 ||
 		result.Config.Empty["retained"] != "default" {
 		t.Fatalf("configuration = %#v", result.Config)
@@ -100,13 +100,13 @@ empty: {}
 	empty, _ := metadata.Lookup(Keys("empty"))
 	firstValue, _ := metadata.Lookup(Keys("values").Index(0))
 	if !equal.Explicit || equal.Origin.Layer != LayerBase || derived.Explicit || derived.Origin.Operation != ChangeDerivedDefault ||
-		!nullable.Explicit || !nullable.Null || nullable.Origin.Layer != LayerProfile ||
-		!empty.Explicit || empty.Origin.Layer != LayerProfile || len(empty.Origin.Locations) != 2 ||
+		!nullable.Explicit || !nullable.Null || nullable.Origin.Layer != LayerOverlay ||
+		!empty.Explicit || empty.Origin.Layer != LayerOverlay || len(empty.Origin.Locations) != 2 ||
 		!firstValue.Explicit || firstValue.Origin.Operation != ChangeNormalization {
 		t.Fatalf("metadata = equal %#v derived %#v nullable %#v empty %#v value %#v", equal, derived, nullable, empty, firstValue)
 	}
 	if _, ok := metadata.Lookup(Keys("value", "child")); ok {
-		t.Fatal("profile-removed child remains effective")
+		t.Fatal("overlay-removed child remains effective")
 	}
 	if _, ok := metadata.Lookup(Keys("values").Index(1)); ok {
 		t.Fatal("resolution-removed sequence index remains effective")
@@ -116,10 +116,10 @@ empty: {}
 	}

 	assertHistoryLayersAndPaths(t, metadata.History(Keys("values").Index(1)),
-		[]Layer{LayerDefault, LayerBase, LayerProfile, LayerResolution},
+		[]Layer{LayerDefault, LayerBase, LayerOverlay, LayerResolution},
 		[]string{"/values/1", "/values/1", "/values", "/values"})
 	assertHistoryLayersAndPaths(t, metadata.History(Keys("value", "child")),
-		[]Layer{LayerDefault, LayerBase, LayerProfile},
+		[]Layer{LayerDefault, LayerBase, LayerOverlay},
 		[]string{"/value/child", "/value/child", "/value"})
 	removedHistory := metadata.History(Keys("items", "remove", "value"))
 	assertHistoryLayersAndPaths(t, removedHistory,
@@ -159,11 +159,11 @@ empty: {}
 	}
 }

-func TestSelectedProfileLoadsRemainIndependentConcurrently(t *testing.T) {
+func TestSelectedOverlayLoadsRemainIndependentConcurrently(t *testing.T) {
 	directory := t.TempDir()
 	mainPath := writeImportFile(t, directory, "main.yml", "values: [1, 2]\n")
-	writeImportFile(t, directory, "profiles/testing.yml", "values: [3, 4]\n")
-	options := Options[layeredConfig]{Profile: "testing"}
+	writeImportFile(t, directory, "overlays/testing.yml", "values: [3, 4]\n")
+	options := Options[layeredConfig]{Overlay: "testing"}

 	const loads = 16
 	results := make(chan *testResult[layeredConfig], loads)
@@ -200,7 +200,7 @@ func TestSelectedProfileLoadsRemainIndependentConcurrently(t *testing.T) {
 		if !reflect.DeepEqual(result.Config.Values, []int{3, 4}) {
 			t.Fatalf("concurrent result contaminated = %#v", result.Config.Values)
 		}
-		if info, ok := result.Metadata().Lookup(Keys("values")); !ok || info.Origin.Layer != LayerProfile {
+		if info, ok := result.Metadata().Lookup(Keys("values")); !ok || info.Origin.Layer != LayerOverlay {
 			t.Fatalf("concurrent metadata contaminated = %#v, %v", info, ok)
 		}
 	}
@@ -220,7 +220,7 @@ sequence: [first, second]
 composite: {first: first}
 `)
 	secondPath := writeImportFile(t, directory, "second.yml", "composite: {second: second}\n")
-	profilePath := writeImportFile(t, directory, "profiles/testing.yml", "equal: same\nprofile: profile\n")
+	overlayPath := writeImportFile(t, directory, "overlays/testing.yml", "equal: same\noverlay: overlay\n")
 	compositeSources := map[string]bool{
 		canonicalTestPath(t, mainPath):   true,
 		canonicalTestPath(t, firstPath):  true,
@@ -232,12 +232,12 @@ composite: {first: first}
 		Sequence  []string          `yaml:"sequence"`
 		Composite map[string]string `yaml:"composite"`
 		Equal     string            `yaml:"equal"`
-		Profile   string            `yaml:"profile"`
+		Overlay   string            `yaml:"overlay"`
 		CLIEqual  string            `yaml:"cli_equal"`
 	}
 	var callbackErr error
 	result, err := testLoad[config](File(mainPath), Options[config]{
-		Imports: true, Profile: "testing", Overrides: []Override{{Path: Keys("cli_equal"), Value: "same", Flag: "--cli-equal"}},
+		Imports: true, Overlay: "testing", Overrides: []Override{{Path: Keys("cli_equal"), Value: "same", Flag: "--cli-equal"}},
 		Definition: Definition[config]{Resolve: func(_ *config, resolution *Resolution) error {
 			check := func(ok bool, message string) {
 				if !ok && callbackErr == nil {
@@ -257,9 +257,9 @@ composite: {first: first}
 			fileOwner(Keys("main"), canonicalTestPath(t, mainPath))
 			fileOwner(Keys("imported"), canonicalTestPath(t, firstPath))
 			fileOwner(Keys("sequence").Index(1), canonicalTestPath(t, firstPath))
-			profile := fileOwner(Keys("equal"), canonicalTestPath(t, profilePath))
-			fileOwner(Keys("profile"), canonicalTestPath(t, profilePath))
-			check(profile.Origin.Layer == LayerProfile, "profile replacement retained base ownership")
+			overlay := fileOwner(Keys("equal"), canonicalTestPath(t, overlayPath))
+			fileOwner(Keys("overlay"), canonicalTestPath(t, overlayPath))
+			check(overlay.Origin.Layer == LayerOverlay, "overlay replacement retained base ownership")
 			cli, found := resolution.InputInfo(Keys("cli_equal"))
 			check(found && cli.Origin.Layer == LayerCLI && len(cli.Origin.Locations) == 1, "CLI replacement lost ownership")
 			if found && len(cli.Origin.Locations) == 1 {
@@ -298,7 +298,7 @@ composite: {first: first}
 		t.Fatal(err)
 	}
 	if result.Config.Main != "main" || result.Config.Imported != "imported" || !reflect.DeepEqual(result.Config.Sequence, []string{"first", "second"}) ||
-		result.Config.Equal != "same" || result.Config.Profile != "profile" || result.Config.CLIEqual != "same" {
+		result.Config.Equal != "same" || result.Config.Overlay != "overlay" || result.Config.CLIEqual != "same" {
 		t.Fatalf("configuration = %#v", result.Config)
 	}

--- a/internal/engine/records.go
+++ b/internal/engine/records.go
@@ -6,7 +6,7 @@ type Layer string
 const (
 	LayerDefault    Layer = "default"
 	LayerBase       Layer = "base"
-	LayerProfile    Layer = "profile"
+	LayerOverlay    Layer = "overlay"
 	LayerCLI        Layer = "cli"
 	LayerResolution Layer = "resolution"
 )
@@ -90,13 +90,13 @@ const (
 	CodeImportLimitExceeded Code = "import.limit_exceeded"
 	CodeImportVersion       Code = "import.version"

-	CodeProfileInvalid       Code = "profile.invalid"
-	CodeProfileMissing       Code = "profile.missing"
-	CodeProfileOutsideRoot   Code = "profile.outside_root"
-	CodeProfileRepeated      Code = "profile.repeated"
-	CodeProfileDirective     Code = "profile.directive"
-	CodeProfileVersion       Code = "profile.version"
-	CodeProfileLimitExceeded Code = "profile.limit_exceeded"
+	CodeOverlayInvalid       Code = "overlay.invalid"
+	CodeOverlayMissing       Code = "overlay.missing"
+	CodeOverlayOutsideRoot   Code = "overlay.outside_root"
+	CodeOverlayRepeated      Code = "overlay.repeated"
+	CodeOverlayDirective     Code = "overlay.directive"
+	CodeOverlayVersion       Code = "overlay.version"
+	CodeOverlayLimitExceeded Code = "overlay.limit_exceeded"

 	CodeComposeInvalid  Code = "compose.invalid"
 	CodeComposeConflict Code = "compose.conflict"
--- a/internal/engine/render_test.go
+++ b/internal/engine/render_test.go
@@ -71,7 +71,7 @@ empty_sequence: []
 labels: {hidden: DYNAMIC_CANARY_6a12, public: visible}
 sequence: [second, first]
 `)
-	writeImportFile(t, directory, "profiles/testing.yml", "dynamic: selected\n")
+	writeImportFile(t, directory, "overlays/testing.yml", "dynamic: selected\n")
 	definition := Definition[renderConfig]{
 		Secret: func(path Path) bool {
 			return path.String() == "/labels/hidden" || path.String() == "/dynamic/retired"
@@ -85,7 +85,7 @@ sequence: [second, first]
 			return nil
 		},
 	}
-	result, err := testLoad[renderConfig](File(mainPath), Options[renderConfig]{Definition: definition, Profile: "testing"})
+	result, err := testLoad[renderConfig](File(mainPath), Options[renderConfig]{Definition: definition, Overlay: "testing"})
 	if err != nil {
 		t.Fatal(err)
 	}
--- a/internal/engine/selected_overlay.go
+++ b/internal/engine/selected_overlay.go
@@ -12,12 +12,12 @@ import (
 	yamladapter "gitea.maximumdirect.net/eric/ConfigKit/internal/yaml"
 )

-func activeProfile(name string) bool {
+func activeOverlay(name string) bool {
 	return name != "" && name != "default"
 }

-func validProfileName(name string) bool {
-	if !activeProfile(name) {
+func validOverlayName(name string) bool {
+	if !activeOverlay(name) {
 		return true
 	}
 	for _, character := range name {
@@ -31,38 +31,38 @@ func validProfileName(name string) bool {
 	return true
 }

-func loadProfileDocument(source Source, context *FilesystemContext, main parsedSource, base *composedDocument, sources []SourceInfo, name string, rule *VersionRule, limits importLimits) (*composedDocument, []SourceInfo, []Diagnostic) {
+func loadSelectedOverlayDocument(source Source, context *FilesystemContext, main parsedSource, base *composedDocument, sources []SourceInfo, name string, rule *VersionRule, limits importLimits) (*composedDocument, []SourceInfo, []Diagnostic) {
 	rootPath, _, _, diagnostic := importFilesystem(source, context, main)
 	if diagnostic != nil {
 		return nil, cloneSourceInfos(sources), []Diagnostic{*diagnostic}
 	}
-	profilePath := filepath.Join(rootPath, "profiles", name+".yml")
-	canonical, err := canonicalExistingPath(profilePath)
+	overlayPath := filepath.Join(rootPath, "overlays", name+".yml")
+	canonical, err := canonicalExistingPath(overlayPath)
 	if err != nil {
-		code := CodeProfileInvalid
-		message := "selected profile could not be resolved"
+		code := CodeOverlayInvalid
+		message := "selected overlay could not be resolved"
 		if errors.Is(err, fs.ErrNotExist) {
-			code, message = CodeProfileMissing, "selected profile does not exist"
+			code, message = CodeOverlayMissing, "selected overlay does not exist"
 		} else if errors.Is(err, fs.ErrPermission) {
-			code, message = CodeImportPermission, "selected profile cannot be accessed"
+			code, message = CodeImportPermission, "selected overlay cannot be accessed"
 		}
 		return nil, cloneSourceInfos(sources), []Diagnostic{importDiagnostic(code, message, nil)}
 	}
 	if !containedPath(rootPath, canonical) {
-		return nil, cloneSourceInfos(sources), []Diagnostic{importDiagnostic(CodeProfileOutsideRoot, "selected profile resolves outside the configuration root", nil)}
+		return nil, cloneSourceInfos(sources), []Diagnostic{importDiagnostic(CodeOverlayOutsideRoot, "selected overlay resolves outside the configuration root", nil)}
 	}
 	for _, existing := range sources {
 		if existing.Path != "" && existing.Path == canonical {
-			return nil, cloneSourceInfos(sources), []Diagnostic{importDiagnostic(CodeProfileRepeated, "selected profile is already present in the base source graph", nil)}
+			return nil, cloneSourceInfos(sources), []Diagnostic{importDiagnostic(CodeOverlayRepeated, "selected overlay is already present in the base source graph", nil)}
 		}
 	}
 	if len(sources)+1 > limits.sources {
-		return nil, cloneSourceInfos(sources), []Diagnostic{importDiagnostic(CodeProfileLimitExceeded, "selected profile exceeds the source-count limit", nil)}
+		return nil, cloneSourceInfos(sources), []Diagnostic{importDiagnostic(CodeOverlayLimitExceeded, "selected overlay exceeds the source-count limit", nil)}
 	}

 	root, err := os.OpenRoot(rootPath)
 	if err != nil {
-		value := globFilesystemDiagnostic(err, "configuration root could not be opened for the selected profile", Location{})
+		value := globFilesystemDiagnostic(err, "configuration root could not be opened for the selected overlay", Location{})
 		value.Primary = nil
 		return nil, cloneSourceInfos(sources), []Diagnostic{value}
 	}
@@ -74,57 +74,57 @@ func loadProfileDocument(source Source, context *FilesystemContext, main parsedS
 	}()
 	relative, err := filepath.Rel(rootPath, canonical)
 	if err != nil || filepath.IsAbs(relative) || relative == ".." || strings.HasPrefix(relative, ".."+string(filepath.Separator)) {
-		return nil, cloneSourceInfos(sources), []Diagnostic{importDiagnostic(CodeProfileOutsideRoot, "selected profile could not be addressed inside the configuration root", nil)}
+		return nil, cloneSourceInfos(sources), []Diagnostic{importDiagnostic(CodeOverlayOutsideRoot, "selected overlay could not be addressed inside the configuration root", nil)}
 	}

 	sourceID := "source-" + strconv.Itoa(len(sources)+1)
-	profileLocation := &Location{SourceID: sourceID}
-	profileSource := SourceInfo{ID: sourceID, Label: filepath.ToSlash(filepath.Join("profiles", name+".yml")), Path: canonical, Layer: LayerProfile}
-	sources = append(cloneSourceInfos(sources), profileSource)
-	data, diagnostic := readProfileFile(root, relative, sourceID, limits.bytes-base.inputBytes)
+	overlayLocation := &Location{SourceID: sourceID}
+	overlaySource := SourceInfo{ID: sourceID, Label: filepath.ToSlash(filepath.Join("overlays", name+".yml")), Path: canonical, Layer: LayerOverlay}
+	sources = append(cloneSourceInfos(sources), overlaySource)
+	data, diagnostic := readOverlayFile(root, relative, sourceID, limits.bytes-base.inputBytes)
 	if diagnostic != nil {
 		return nil, sources, []Diagnostic{*diagnostic}
 	}
-	profileRoot, issues := yamladapter.Parse(bytes.NewReader(data), sourceID, yamladapter.Limits{Depth: maxDocumentDepth, Nodes: maxDocumentNodes})
+	overlayRoot, issues := yamladapter.Parse(bytes.NewReader(data), sourceID, yamladapter.Limits{Depth: maxDocumentDepth, Nodes: maxDocumentNodes})
 	if len(issues) != 0 {
 		return nil, sources, parserDiagnostics(sourceID, issues)
 	}
-	nodeCount := countInputNodes(profileRoot)
+	nodeCount := countInputNodes(overlayRoot)
 	if base.inputNodes+nodeCount > limits.nodes {
-		return nil, sources, []Diagnostic{importDiagnostic(CodeProfileLimitExceeded, "selected profile exceeds the aggregate node limit", profileLocation)}
+		return nil, sources, []Diagnostic{importDiagnostic(CodeOverlayLimitExceeded, "selected overlay exceeds the aggregate node limit", overlayLocation)}
 	}
-	if diagnostics := profileDirectiveDiagnostics(profileRoot, Path{}); len(diagnostics) != 0 {
+	if diagnostics := overlayDirectiveDiagnostics(overlayRoot, Path{}); len(diagnostics) != 0 {
 		return nil, sources, diagnostics
 	}
-	if versionNode := fragmentVersionClaim(profileRoot, rule); versionNode != nil {
+	if versionNode := fragmentVersionClaim(overlayRoot, rule); versionNode != nil {
 		location := publicLocation(versionNode.Location)
 		return nil, sources, []Diagnostic{{
-			Code: CodeProfileVersion, Severity: SeverityError, Path: rule.Path.clone(),
-			Message: "profiles cannot contribute to or replace the schema-version path", Primary: &location,
+			Code: CodeOverlayVersion, Severity: SeverityError, Path: rule.Path.clone(),
+			Message: "overlays cannot contribute to or replace the schema-version path", Primary: &location,
 		}}
 	}
 	closeErr := root.Close()
 	rootClosed = true
 	if closeErr != nil {
-		return nil, sources, []Diagnostic{importDiagnostic(CodeImportRead, "configuration root could not be closed after reading the selected profile", nil)}
+		return nil, sources, []Diagnostic{importDiagnostic(CodeImportRead, "configuration root could not be closed after reading the selected overlay", nil)}
 	}

-	profiled, diagnostics := overlayDocuments(base, profileRoot)
-	if profiled != nil {
-		profiled.inputBytes = base.inputBytes + int64(len(data))
-		profiled.inputNodes = base.inputNodes + nodeCount
+	overlayd, diagnostics := overlayDocuments(base, overlayRoot)
+	if overlayd != nil {
+		overlayd.inputBytes = base.inputBytes + int64(len(data))
+		overlayd.inputNodes = base.inputNodes + nodeCount
 	}
-	return profiled, sources, diagnostics
+	return overlayd, sources, diagnostics
 }

-func readProfileFile(root *os.Root, relative, sourceID string, remaining int64) ([]byte, *Diagnostic) {
+func readOverlayFile(root *os.Root, relative, sourceID string, remaining int64) ([]byte, *Diagnostic) {
 	limit := min(int64(maxSourceBytes), remaining)
 	if limit < 0 {
 		limit = 0
 	}
 	data, failure := readRegularFile(relative, root.Stat, root.Open, limit)
 	if failure != nil {
-		value := sourceReadDiagnostic(failure, sourceID, CodeProfileLimitExceeded, "selected profile exceeds a source or aggregate byte limit")
+		value := sourceReadDiagnostic(failure, sourceID, CodeOverlayLimitExceeded, "selected overlay exceeds a source or aggregate byte limit")
 		return nil, &value
 	}
 	return data, nil
--- a/internal/engine/selected_overlay_test.go
+++ b/internal/engine/selected_overlay_test.go
@@ -9,7 +9,7 @@ import (
 	"testing"
 )

-type profileTestConfig struct {
+type overlayTestConfig struct {
 	Settings struct {
 		Kept    string `yaml:"kept"`
 		Changed string `yaml:"changed"`
@@ -21,7 +21,7 @@ type profileTestConfig struct {
 	Schema   map[string]string `yaml:"schema"`
 }

-func TestLoadAppliesSelectedProfileAfterBaseAndBeforeDefaults(t *testing.T) {
+func TestLoadAppliesSelectedOverlayAfterBaseAndBeforeDefaults(t *testing.T) {
 	directory := t.TempDir()
 	mainPath := writeImportFile(t, directory, "main.yml", `configkit:
  imports: [{path: base.yml}]
@@ -33,19 +33,19 @@ nullable: base
 value: {child: base}
 `)
 	basePath := writeImportFile(t, directory, "base.yml", "settings: {added: imported}\n")
-	profilePath := writeImportFile(t, directory, "profiles/testing.yml", `settings:
-  changed: profile
-values: [profile]
+	overlayPath := writeImportFile(t, directory, "overlays/testing.yml", `settings:
+  changed: overlay
+values: [overlay]
 nullable: null
 value: scalar
 `)

-	result, err := testLoad[profileTestConfig](File(mainPath), Options[profileTestConfig]{
+	result, err := testLoad[overlayTestConfig](File(mainPath), Options[overlayTestConfig]{
 		Imports: true,
-		Profile: "testing",
-		Definition: Definition[profileTestConfig]{Defaults: func() profileTestConfig {
+		Overlay: "testing",
+		Definition: Definition[overlayTestConfig]{Defaults: func() overlayTestConfig {
 			defaultValue := "default"
-			return profileTestConfig{
+			return overlayTestConfig{
 				Values: []string{"default"}, Nullable: &defaultValue,
 				Settings: struct {
 					Kept    string `yaml:"kept"`
@@ -58,31 +58,31 @@ value: scalar
 	if err != nil {
 		t.Fatal(err)
 	}
-	if result.Config.Settings.Kept != "main" || result.Config.Settings.Changed != "profile" || result.Config.Settings.Added != "imported" {
+	if result.Config.Settings.Kept != "main" || result.Config.Settings.Changed != "overlay" || result.Config.Settings.Added != "imported" {
 		t.Fatalf("settings = %#v", result.Config.Settings)
 	}
-	if !reflect.DeepEqual(result.Config.Values, []string{"profile"}) || result.Config.Nullable != nil || result.Config.Value != "scalar" {
-		t.Fatalf("profile values = values %#v nullable %#v value %#v", result.Config.Values, result.Config.Nullable, result.Config.Value)
+	if !reflect.DeepEqual(result.Config.Values, []string{"overlay"}) || result.Config.Nullable != nil || result.Config.Value != "scalar" {
+		t.Fatalf("overlay values = values %#v nullable %#v value %#v", result.Config.Values, result.Config.Nullable, result.Config.Value)
 	}
 	sources := result.Sources()
-	wantPaths := []string{canonicalTestPath(t, mainPath), canonicalTestPath(t, basePath), canonicalTestPath(t, profilePath)}
+	wantPaths := []string{canonicalTestPath(t, mainPath), canonicalTestPath(t, basePath), canonicalTestPath(t, overlayPath)}
 	gotPaths := make([]string, len(sources))
 	for index, source := range sources {
 		gotPaths[index] = source.Path
 	}
-	if !reflect.DeepEqual(gotPaths, wantPaths) || sources[2].Layer != LayerProfile {
+	if !reflect.DeepEqual(gotPaths, wantPaths) || sources[2].Layer != LayerOverlay {
 		t.Fatalf("sources = %#v", sources)
 	}
 	changed, _ := result.Metadata().Lookup(Keys("settings", "changed"))
 	kept, _ := result.Metadata().Lookup(Keys("settings", "kept"))
-	if changed.Origin.Layer != LayerProfile || changed.Origin.Locations[0].SourceID != "source-3" || kept.Origin.Layer != LayerBase {
+	if changed.Origin.Layer != LayerOverlay || changed.Origin.Locations[0].SourceID != "source-3" || kept.Origin.Layer != LayerBase {
 		t.Fatalf("origins = changed %#v kept %#v", changed, kept)
 	}
 	if _, ok := result.Metadata().Lookup(Keys("value", "child")); ok {
 		t.Fatal("removed child remains effective")
 	}
 	childHistory := result.Metadata().History(Keys("value", "child"))
-	if len(childHistory) < 2 || childHistory[len(childHistory)-1].Path.String() != "/value" || childHistory[len(childHistory)-1].Origin.Layer != LayerProfile {
+	if len(childHistory) < 2 || childHistory[len(childHistory)-1].Path.String() != "/value" || childHistory[len(childHistory)-1].Origin.Layer != LayerOverlay {
 		t.Fatalf("removed child history = %#v", childHistory)
 	}
 	if _, ok := result.Metadata().Lookup(Keys("values").Index(1)); ok {
@@ -94,34 +94,34 @@ value: scalar
 	}
 }

-func TestLoadProfileSelectionUsesOneFixedYAMLFile(t *testing.T) {
+func TestLoadOverlaySelectionUsesOneFixedYAMLFile(t *testing.T) {
 	directory := t.TempDir()
 	mainPath := writeImportFile(t, directory, "main.yml", "settings: {kept: base}\n")
-	writeImportFile(t, directory, "profiles/testing.yml", "settings: {changed: selected}\n")
-	writeImportFile(t, directory, "profiles/default.yml", "settings: {changed: forbidden}\n")
+	writeImportFile(t, directory, "overlays/testing.yml", "settings: {changed: selected}\n")
+	writeImportFile(t, directory, "overlays/default.yml", "settings: {changed: forbidden}\n")

 	for _, name := range []string{"", "default"} {
-		result, err := testLoad[profileTestConfig](File(mainPath), Options[profileTestConfig]{Profile: name})
+		result, err := testLoad[overlayTestConfig](File(mainPath), Options[overlayTestConfig]{Overlay: name})
 		if err != nil || result.Config.Settings.Changed != "" || len(result.Sources()) != 1 {
-			t.Fatalf("inactive profile %q = %#v, %v", name, result, err)
+			t.Fatalf("inactive overlay %q = %#v, %v", name, result, err)
 		}
 	}
-	selected, err := testLoad[profileTestConfig](File(mainPath), Options[profileTestConfig]{Profile: "testing"})
+	selected, err := testLoad[overlayTestConfig](File(mainPath), Options[overlayTestConfig]{Overlay: "testing"})
 	if err != nil || selected.Config.Settings.Changed != "selected" || len(selected.Sources()) != 2 {
-		t.Fatalf("selected profile = %#v, %v", selected, err)
+		t.Fatalf("selected overlay = %#v, %v", selected, err)
 	}

 	for _, name := range []string{"../testing", "testing.yml", "one,two", "with space", "é", "bad\x00name"} {
 		t.Run(name, func(t *testing.T) {
-			requireProfileLoadCode(t, File(mainPath), Options[profileTestConfig]{Profile: name}, CodeOptionsInvalid)
+			requireOverlayLoadCode(t, File(mainPath), Options[overlayTestConfig]{Overlay: name}, CodeOptionsInvalid)
 		})
 	}
-	requireProfileLoadCode(t, File(mainPath), Options[profileTestConfig]{Profile: "missing"}, CodeProfileMissing)
-	writeImportFile(t, directory, "profiles/fallback.yaml", "settings: {changed: fallback}\n")
-	requireProfileLoadCode(t, File(mainPath), Options[profileTestConfig]{Profile: "fallback"}, CodeProfileMissing)
+	requireOverlayLoadCode(t, File(mainPath), Options[overlayTestConfig]{Overlay: "missing"}, CodeOverlayMissing)
+	writeImportFile(t, directory, "overlays/fallback.yaml", "settings: {changed: fallback}\n")
+	requireOverlayLoadCode(t, File(mainPath), Options[overlayTestConfig]{Overlay: "fallback"}, CodeOverlayMissing)
 }

-func TestLoadProfileRejectsDirectivesVersionsAndBaseAliases(t *testing.T) {
+func TestLoadOverlayRejectsDirectivesVersionsAndBaseAliases(t *testing.T) {
 	versionRule := &VersionRule{Path: Keys("schema", "version"), Check: func(version Version, _ *Validation) error {
 		if !version.Present || version.Text != "4" {
 			return errors.New("unexpected version")
@@ -130,55 +130,55 @@ func TestLoadProfileRejectsDirectivesVersionsAndBaseAliases(t *testing.T) {
 	}}
 	for _, test := range []struct {
 		name    string
-		profile string
+		overlay string
 		code    Code
 	}{
-		{name: "root directive", profile: "configkit: {}\n", code: CodeProfileDirective},
-		{name: "nested directive", profile: "settings: {configkit: {}}\n", code: CodeProfileDirective},
-		{name: "equal integer version", profile: "schema: {version: 4}\n", code: CodeProfileVersion},
-		{name: "ancestor scalar", profile: "schema: null\n", code: CodeProfileVersion},
+		{name: "root directive", overlay: "configkit: {}\n", code: CodeOverlayDirective},
+		{name: "nested directive", overlay: "settings: {configkit: {}}\n", code: CodeOverlayDirective},
+		{name: "equal integer version", overlay: "schema: {version: 4}\n", code: CodeOverlayVersion},
+		{name: "ancestor scalar", overlay: "schema: null\n", code: CodeOverlayVersion},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			directory := t.TempDir()
 			mainPath := writeImportFile(t, directory, "main.yml", "schema: {version: 4}\n")
-			writeImportFile(t, directory, "profiles/testing.yml", test.profile)
-			requireProfileLoadCode(t, File(mainPath), Options[profileTestConfig]{Profile: "testing", Definition: Definition[profileTestConfig]{Version: versionRule}}, test.code)
+			writeImportFile(t, directory, "overlays/testing.yml", test.overlay)
+			requireOverlayLoadCode(t, File(mainPath), Options[overlayTestConfig]{Overlay: "testing", Definition: Definition[overlayTestConfig]{Version: versionRule}}, test.code)
 		})
 	}

 	t.Run("mapping sibling is allowed", func(t *testing.T) {
 		directory := t.TempDir()
 		mainPath := writeImportFile(t, directory, "main.yml", "schema: {version: 4}\n")
-		writeImportFile(t, directory, "profiles/testing.yml", "schema: {other: allowed}\n")
-		result, err := testLoad[profileTestConfig](File(mainPath), Options[profileTestConfig]{Profile: "testing", Definition: Definition[profileTestConfig]{Version: versionRule}})
+		writeImportFile(t, directory, "overlays/testing.yml", "schema: {other: allowed}\n")
+		result, err := testLoad[overlayTestConfig](File(mainPath), Options[overlayTestConfig]{Overlay: "testing", Definition: Definition[overlayTestConfig]{Version: versionRule}})
 		if err != nil || result.Config.Schema["other"] != "allowed" {
 			t.Fatalf("mapping sibling = %#v, %v", result, err)
 		}
 	})

-	t.Run("profile aliases imported base", func(t *testing.T) {
+	t.Run("overlay aliases imported base", func(t *testing.T) {
 		directory := t.TempDir()
-		mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: profiles/testing.yml}]}\n")
-		writeImportFile(t, directory, "profiles/testing.yml", "settings: {changed: value}\n")
-		requireProfileLoadCode(t, File(mainPath), Options[profileTestConfig]{Imports: true, Profile: "testing"}, CodeProfileRepeated)
+		mainPath := writeImportFile(t, directory, "main.yml", "configkit: {imports: [{path: overlays/testing.yml}]}\n")
+		writeImportFile(t, directory, "overlays/testing.yml", "settings: {changed: value}\n")
+		requireOverlayLoadCode(t, File(mainPath), Options[overlayTestConfig]{Imports: true, Overlay: "testing"}, CodeOverlayRepeated)
 	})
 }

-func TestLoadProfileKeepsBaseFailuresAndFilesystemContainment(t *testing.T) {
-	t.Run("base parse precedes profile", func(t *testing.T) {
+func TestLoadOverlayKeepsBaseFailuresAndFilesystemContainment(t *testing.T) {
+	t.Run("base parse precedes overlay", func(t *testing.T) {
 		directory := t.TempDir()
 		mainPath := writeImportFile(t, directory, "main.yml", "settings: [\n")
-		writeImportFile(t, directory, "profiles/testing.yml", "settings: {changed: profile}\n")
-		requireProfileLoadCode(t, File(mainPath), Options[profileTestConfig]{Profile: "testing"}, CodeYAMLInvalid)
+		writeImportFile(t, directory, "overlays/testing.yml", "settings: {changed: overlay}\n")
+		requireOverlayLoadCode(t, File(mainPath), Options[overlayTestConfig]{Overlay: "testing"}, CodeYAMLInvalid)
 	})

-	t.Run("profile parse", func(t *testing.T) {
+	t.Run("overlay parse", func(t *testing.T) {
 		directory := t.TempDir()
 		mainPath := writeImportFile(t, directory, "main.yml", "{}\n")
-		writeImportFile(t, directory, "profiles/testing.yml", "settings: [\n")
-		loadError := requireProfileLoadCode(t, File(mainPath), Options[profileTestConfig]{Profile: "testing"}, CodeYAMLInvalid)
+		writeImportFile(t, directory, "overlays/testing.yml", "settings: [\n")
+		loadError := requireOverlayLoadCode(t, File(mainPath), Options[overlayTestConfig]{Overlay: "testing"}, CodeYAMLInvalid)
 		if loadError.Diagnostics()[0].Primary.SourceID != "source-2" || len(loadError.Sources()) != 2 {
-			t.Fatalf("profile parse attribution = %#v / %#v", loadError.Diagnostics(), loadError.Sources())
+			t.Fatalf("overlay parse attribution = %#v / %#v", loadError.Diagnostics(), loadError.Sources())
 		}
 	})

@@ -186,32 +186,32 @@ func TestLoadProfileKeepsBaseFailuresAndFilesystemContainment(t *testing.T) {
 		t.Run("symlink escape", func(t *testing.T) {
 			root := t.TempDir()
 			outside := t.TempDir()
-			outsideProfile := writeImportFile(t, outside, "testing.yml", "settings: {changed: outside}\n")
-			if err := os.Mkdir(filepath.Join(root, "profiles"), 0o755); err != nil {
+			outsideOverlay := writeImportFile(t, outside, "testing.yml", "settings: {changed: outside}\n")
+			if err := os.Mkdir(filepath.Join(root, "overlays"), 0o755); err != nil {
 				t.Fatal(err)
 			}
-			if err := os.Symlink(outsideProfile, filepath.Join(root, "profiles/testing.yml")); err != nil {
+			if err := os.Symlink(outsideOverlay, filepath.Join(root, "overlays/testing.yml")); err != nil {
 				t.Skipf("symlinks unavailable: %v", err)
 			}
 			mainPath := writeImportFile(t, root, "main.yml", "{}\n")
-			requireProfileLoadCode(t, File(mainPath), Options[profileTestConfig]{Profile: "testing"}, CodeProfileOutsideRoot)
+			requireOverlayLoadCode(t, File(mainPath), Options[overlayTestConfig]{Overlay: "testing"}, CodeOverlayOutsideRoot)
 		})
 	}

 	t.Run("byte source context", func(t *testing.T) {
 		directory := t.TempDir()
-		writeImportFile(t, directory, "profiles/testing.yml", "settings: {changed: selected}\n")
-		result, err := testLoad[profileTestConfig](Bytes("s3://bucket/main.yml", []byte("{}\n")), Options[profileTestConfig]{
-			Profile: "testing", Filesystem: &FilesystemContext{BaseDir: directory, Root: directory},
+		writeImportFile(t, directory, "overlays/testing.yml", "settings: {changed: selected}\n")
+		result, err := testLoad[overlayTestConfig](Bytes("s3://bucket/main.yml", []byte("{}\n")), Options[overlayTestConfig]{
+			Overlay: "testing", Filesystem: &FilesystemContext{BaseDir: directory, Root: directory},
 		})
 		if err != nil || result.Config.Settings.Changed != "selected" {
-			t.Fatalf("byte profile = %#v, %v", result, err)
+			t.Fatalf("byte overlay = %#v, %v", result, err)
 		}
-		requireProfileLoadCode(t, Bytes("memory.yml", []byte("{}\n")), Options[profileTestConfig]{Profile: "testing"}, CodeOptionsInvalid)
+		requireOverlayLoadCode(t, Bytes("memory.yml", []byte("{}\n")), Options[overlayTestConfig]{Overlay: "testing"}, CodeOptionsInvalid)
 	})
 }

-func TestLoadProfileCountsAgainstAggregateBudgets(t *testing.T) {
+func TestLoadOverlayCountsAgainstAggregateBudgets(t *testing.T) {
 	for _, test := range []struct {
 		name   string
 		limits func(parsedSource, int) importLimits
@@ -219,8 +219,8 @@ func TestLoadProfileCountsAgainstAggregateBudgets(t *testing.T) {
 		{name: "source count", limits: func(_ parsedSource, _ int) importLimits {
 			return importLimits{sources: 1, bytes: maxTotalBytes, nodes: maxDocumentNodes}
 		}},
-		{name: "aggregate bytes", limits: func(main parsedSource, profileBytes int) importLimits {
-			return importLimits{sources: 2, bytes: main.bytes + int64(profileBytes) - 1, nodes: maxDocumentNodes}
+		{name: "aggregate bytes", limits: func(main parsedSource, overlayBytes int) importLimits {
+			return importLimits{sources: 2, bytes: main.bytes + int64(overlayBytes) - 1, nodes: maxDocumentNodes}
 		}},
 		{name: "aggregate nodes", limits: func(main parsedSource, _ int) importLimits {
 			return importLimits{sources: 2, bytes: maxTotalBytes, nodes: countInputNodes(main.document) + 1}
@@ -229,8 +229,8 @@ func TestLoadProfileCountsAgainstAggregateBudgets(t *testing.T) {
 		t.Run(test.name, func(t *testing.T) {
 			directory := t.TempDir()
 			mainPath := writeImportFile(t, directory, "main.yml", "{}\n")
-			profileData := "settings: {changed: selected}\n"
-			writeImportFile(t, directory, "profiles/testing.yml", profileData)
+			overlayData := "settings: {changed: selected}\n"
+			writeImportFile(t, directory, "overlays/testing.yml", overlayData)
 			main, diagnostics := parseSource(File(mainPath), "source-1", defaultParseLimits())
 			if len(diagnostics) != 0 {
 				t.Fatal(diagnostics)
@@ -241,17 +241,17 @@ func TestLoadProfileCountsAgainstAggregateBudgets(t *testing.T) {
 			}
 			base.inputBytes = main.bytes
 			base.inputNodes = countInputNodes(main.document)
-			_, _, diagnostics = loadProfileDocument(File(mainPath), nil, main, base, sourceInfos(main.source), "testing", nil, test.limits(main, len(profileData)))
-			if len(diagnostics) == 0 || diagnostics[0].Code != CodeProfileLimitExceeded {
+			_, _, diagnostics = loadSelectedOverlayDocument(File(mainPath), nil, main, base, sourceInfos(main.source), "testing", nil, test.limits(main, len(overlayData)))
+			if len(diagnostics) == 0 || diagnostics[0].Code != CodeOverlayLimitExceeded {
 				t.Fatalf("diagnostics = %#v", diagnostics)
 			}
 		})
 	}
 }

-func requireProfileLoadCode(t *testing.T, source Source, options Options[profileTestConfig], code Code) *LoadError {
+func requireOverlayLoadCode(t *testing.T, source Source, options Options[overlayTestConfig], code Code) *LoadError {
 	t.Helper()
-	result, err := testLoad[profileTestConfig](source, options)
+	result, err := testLoad[overlayTestConfig](source, options)
 	if result != nil || err == nil {
 		t.Fatalf("result, error = %#v, %v", result, err)
 	}
--- a/internal/engine/source_fifo_test.go
+++ b/internal/engine/source_fifo_test.go
@@ -23,8 +23,8 @@ func TestNonregularSourcesDoNotBlock(t *testing.T) {
 			source = File(filepath.Join(root, "pipe.yml"))
 		case "import":
 			opts.Imports = true
-		case "profile":
-			opts.Profile = "fifo"
+		case "overlay":
+			opts.Overlay = "fifo"
 		}
 		_, err := testLoad(source, opts)
 		var loadErr *LoadError
@@ -38,7 +38,7 @@ func TestNonregularSourcesDoNotBlock(t *testing.T) {
 		}
 		t.Fatalf("expected nonregular classification, got %v", loadErr.Diagnostics())
 	}
-	for _, mode := range []string{"file", "import", "profile"} {
+	for _, mode := range []string{"file", "import", "overlay"} {
 		t.Run(mode, func(t *testing.T) {
 			root := t.TempDir()
 			input := "value: 1\n"
@@ -48,12 +48,12 @@ func TestNonregularSourcesDoNotBlock(t *testing.T) {
 			if err := os.WriteFile(filepath.Join(root, "config.yml"), []byte(input), 0600); err != nil {
 				t.Fatal(err)
 			}
-			if err := os.Mkdir(filepath.Join(root, "profiles"), 0700); err != nil {
+			if err := os.Mkdir(filepath.Join(root, "overlays"), 0700); err != nil {
 				t.Fatal(err)
 			}
 			fifo := filepath.Join(root, "pipe.yml")
-			if mode == "profile" {
-				fifo = filepath.Join(root, "profiles", "fifo.yml")
+			if mode == "overlay" {
+				fifo = filepath.Join(root, "overlays", "fifo.yml")
 			}
 			if err := syscall.Mkfifo(fifo, 0600); err != nil {
 				t.Fatal(err)