diff --git a/Makefile b/Makefile
index e5ba828c..137b94d0 100644
--- a/Makefile
+++ b/Makefile
@@ -6,9 +6,12 @@ all: tidy cuefmtcheck lintcue lintinsights test
 # SCHEMA VALIDATION TESTS
 #
 
+# -count=1: the tests read the *.cue schemas at runtime, which Go's test cache
+# cannot track, so cached passes can go stale against edited schemas.
 test:
 	@echo "  >  Running schema validation tests ..."
-	@cd test && go test -v ./...
+	@cd test && go test -v -count=1 ./...
+	@cd cmd && go test -v -count=1 ./...
 	@echo "  >  Schema validation tests complete."
 
 
diff --git a/cmd/internal/cmd/converter.go b/cmd/internal/cmd/converter.go
index fadd9db5..18eda35c 100644
--- a/cmd/internal/cmd/converter.go
+++ b/cmd/internal/cmd/converter.go
@@ -40,6 +40,14 @@ type OpenAPIComponents struct {
 	Schemas map[string]interface{} `yaml:"schemas" json:"schemas"`
 }
 
+// hiddenBase maps a hidden definition name (e.g. "_MappingStrict") to the
+// visible definition it constrains (e.g. "Mapping"), so refs can be rewritten
+// and the hidden definition omitted from output. Populated before parsing.
+// Rewriting a ref intentionally drops the hidden definition's extra
+// constraints (e.g. conditional requiredness), which OpenAPI cannot express;
+// the ref collapses to the visible base type.
+var hiddenBase map[string]string
+
 type SchemaInfo struct {
 	Type        string                 `yaml:"type,omitempty" json:"type,omitempty"`
 	Description string                 `yaml:"description,omitempty" json:"description,omitempty"`
@@ -48,6 +56,7 @@ type SchemaInfo struct {
 	Pattern     string                 `yaml:"pattern,omitempty" json:"pattern,omitempty"`
 	Format      string                 `yaml:"format,omitempty" json:"format,omitempty"`
 	Items       interface{}            `yaml:"items,omitempty" json:"items,omitempty"`
+	Enum        []string               `yaml:"enum,omitempty" json:"enum,omitempty"`
 	Ref         string                 `yaml:"$ref,omitempty" json:"$ref,omitempty"`
 	XStatus     string                 `yaml:"x-status,omitempty" json:"x-status,omitempty"`
 }
@@ -105,6 +114,28 @@ func convertCUEToOpenAPI(schemaDir, outputPath string, opts ConvertOpts) error {
 	seen := make(map[string]bool)
 	manifest := make(map[string][]string) // filename → schema names
 	files := insts[0].Files
+
+	// Pre-pass: map hidden definitions (#_Name) to the visible definition
+	// they constrain, so they can be filtered and their refs rewritten.
+	hiddenBase = make(map[string]string)
+	for _, f := range files {
+		for _, decl := range f.Decls {
+			field, ok := decl.(*ast.Field)
+			if !ok {
+				continue
+			}
+			ident, ok := field.Label.(*ast.Ident)
+			if !ok || !strings.HasPrefix(ident.Name, "#_") {
+				continue
+			}
+			base := findBaseIdent(field.Value)
+			if base == "" {
+				return fmt.Errorf("hidden definition %s does not unify with a visible definition; cue2openapi cannot rewrite refs to it", ident.Name)
+			}
+			hiddenBase[strings.TrimPrefix(ident.Name, "#")] = base
+		}
+	}
+
 	names := make([]string, 0, len(files))
 	byName := make(map[string]*ast.File)
 	for _, f := range files {
@@ -205,6 +236,9 @@ func parseFile(file *ast.File, spec *OpenAPISpec, seen map[string]bool, rootName
 			continue
 		}
 		typeName := strings.TrimPrefix(ident.Name, "#")
+		if _, hidden := hiddenBase[typeName]; hidden {
+			continue // internal validation helper; refs are rewritten to its base
+		}
 		if rootName != "" && ident.Name == "#"+rootName {
 			if field.Comments() != nil {
 				for _, cg := range field.Comments() {
@@ -339,6 +373,76 @@ func parseDefinitionField(field *ast.Field, spec *OpenAPISpec, fileStatus string
 	}
 }
 
+// findBaseIdent walks a conjunction like `{...} & #Base & {...}` and returns
+// the first visible definition name it embeds or unifies with. Inside struct
+// literals only embed declarations are inspected, so an attribute-only struct
+// like `{@go(-)}` never counts as a base.
+func findBaseIdent(expr ast.Expr) string {
+	switch x := expr.(type) {
+	case *ast.Ident:
+		if strings.HasPrefix(x.Name, "#") && !strings.HasPrefix(x.Name, "#_") {
+			return strings.TrimPrefix(x.Name, "#")
+		}
+	case *ast.BinaryExpr:
+		if x.Op == token.AND {
+			if n := findBaseIdent(x.X); n != "" {
+				return n
+			}
+			return findBaseIdent(x.Y)
+		}
+	case *ast.StructLit:
+		for _, elt := range x.Elts {
+			if ed, ok := elt.(*ast.EmbedDecl); ok {
+				if n := findBaseIdent(ed.Expr); n != "" {
+					return n
+				}
+			}
+		}
+	}
+	return ""
+}
+
+// refTarget resolves a definition reference name, substituting hidden
+// definitions with the visible definition they constrain.
+func refTarget(name string) string {
+	n := strings.TrimPrefix(name, "#")
+	if base, ok := hiddenBase[n]; ok {
+		return base
+	}
+	return n
+}
+
+// collectEnumStrings flattens a disjunction of string literals ("a" | *"b" | "c")
+// into its values. Returns ok=false if any branch is not a string literal.
+func collectEnumStrings(expr ast.Expr) ([]string, bool) {
+	switch x := expr.(type) {
+	case *ast.BinaryExpr:
+		if x.Op != token.OR {
+			return nil, false
+		}
+		left, ok := collectEnumStrings(x.X)
+		if !ok {
+			return nil, false
+		}
+		right, ok := collectEnumStrings(x.Y)
+		if !ok {
+			return nil, false
+		}
+		return append(left, right...), true
+	case *ast.UnaryExpr:
+		// Default marker: *"value". The default itself is deliberately not
+		// emitted as an OpenAPI `default`; only the enum value is kept.
+		if x.Op == token.MUL {
+			return collectEnumStrings(x.X)
+		}
+	case *ast.BasicLit:
+		if x.Kind == token.STRING {
+			return []string{strings.Trim(x.Value, "\"")}, true
+		}
+	}
+	return nil, false
+}
+
 func convertStructToSchema(st *ast.StructLit, spec *OpenAPISpec, description string) *SchemaInfo {
 	schema := &SchemaInfo{
 		Type:        "object",
@@ -355,7 +459,13 @@ func convertStructToSchema(st *ast.StructLit, spec *OpenAPISpec, description str
 			fieldSchema := convertFieldToSchema(x, spec, pendingComment)
 			if fieldSchema != nil {
 				fieldName := getFieldName(x)
-				if fieldName != "" {
+				// Only an unquoted _name label is hidden in CUE; a quoted
+				// "_name" is a regular exported field.
+				hidden := false
+				if id, ok := x.Label.(*ast.Ident); ok {
+					hidden = strings.HasPrefix(id.Name, "_")
+				}
+				if fieldName != "" && !hidden {
 					schema.Properties[fieldName] = fieldSchema
 					// Check if field is required
 					if x.Optional == token.NoPos {
@@ -427,8 +537,7 @@ func convertIdentToSchema(ident *ast.Ident, spec *OpenAPISpec, description strin
 		return &SchemaInfo{Type: "boolean", Description: description}
 	} else if strings.HasPrefix(name, "#") {
 		// Type reference
-		refType := strings.TrimPrefix(name, "#")
-		return &SchemaInfo{Ref: fmt.Sprintf("#/components/schemas/%s", refType), Description: description}
+		return &SchemaInfo{Ref: fmt.Sprintf("#/components/schemas/%s", refTarget(name)), Description: description}
 	}
 
 	return &SchemaInfo{Type: "string", Description: description}
@@ -461,6 +570,9 @@ func convertBinaryExprToSchema(expr *ast.BinaryExpr, spec *OpenAPISpec, descript
 
 	// Handle union types (disjunctions)
 	if expr.Op == token.OR {
+		if values, ok := collectEnumStrings(expr); ok {
+			return &SchemaInfo{Type: "string", Description: description, Enum: values}
+		}
 		return &SchemaInfo{Type: "string", Description: description}
 	}
 
@@ -483,12 +595,11 @@ func convertListLitToSchema(list *ast.ListLit, spec *OpenAPISpec, description st
 		// Also check for [#Contact, ...] pattern
 		if ident, ok := elt.(*ast.Ident); ok {
 			if strings.HasPrefix(ident.Name, "#") {
-				refType := strings.TrimPrefix(ident.Name, "#")
 				return &SchemaInfo{
 					Type:        "array",
 					Description: description,
 					Items: &SchemaInfo{
-						Ref: fmt.Sprintf("#/components/schemas/%s", refType),
+						Ref: fmt.Sprintf("#/components/schemas/%s", refTarget(ident.Name)),
 					},
 				}
 			}
diff --git a/cmd/internal/cmd/converter_test.go b/cmd/internal/cmd/converter_test.go
new file mode 100644
index 00000000..4aeb6598
--- /dev/null
+++ b/cmd/internal/cmd/converter_test.go
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package cmd
+
+import (
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
+	"testing"
+
+	"cuelang.org/go/cue/parser"
+	"github.com/goccy/go-yaml"
+)
+
+func TestConvertCUEToOpenAPI(t *testing.T) {
+	out := filepath.Join(t.TempDir(), "openapi.yaml")
+	if err := convertCUEToOpenAPI("../../..", out, ConvertOpts{}); err != nil {
+		t.Fatal(err)
+	}
+	data, err := os.ReadFile(out)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var spec struct {
+		Components struct {
+			Schemas map[string]SchemaInfo `yaml:"schemas"`
+		} `yaml:"components"`
+	}
+	if err := yaml.Unmarshal(data, &spec); err != nil {
+		t.Fatal(err)
+	}
+	schemas := spec.Components.Schemas
+
+	// Disjunctions of string literals emit enum values. Expected values come
+	// from #MethodType (policy.cue) and #Lifecycle (collections.cue); update
+	// here when those CUE enums change.
+	if got := schemas["MethodType"].Enum; !slices.Equal(got, []string{"Behavioral", "Intent", "Remediation", "Gate"}) {
+		t.Errorf("MethodType enum = %v", got)
+	}
+	// "Active" is the *default in CUE; it appears here as a plain enum value.
+	if got := schemas["Lifecycle"].Enum; !slices.Equal(got, []string{"Active", "Draft", "Deprecated", "Retired"}) {
+		t.Errorf("Lifecycle enum = %v", got)
+	}
+
+	// Hidden definitions and hidden fields don't leak into the output.
+	for name, s := range schemas {
+		if strings.HasPrefix(name, "_") {
+			t.Errorf("hidden definition %s leaked into schemas", name)
+		}
+		for prop := range s.Properties {
+			if strings.HasPrefix(prop, "_") {
+				t.Errorf("hidden field %s.%s leaked into properties", name, prop)
+			}
+		}
+	}
+
+	// Refs to hidden definitions resolve to their visible base type
+	// (#_MappingStrict -> Mapping, mappingdocument.cue).
+	mappings, ok := schemas["MappingDocument"].Properties["mappings"].(map[string]interface{})
+	if !ok {
+		t.Fatalf("MappingDocument.mappings missing or not a map: %v", schemas["MappingDocument"].Properties["mappings"])
+	}
+	items, _ := mappings["items"].(map[string]interface{})
+	if ref, _ := items["$ref"].(string); ref != "#/components/schemas/Mapping" {
+		t.Errorf("MappingDocument.mappings items $ref = %q, want #/components/schemas/Mapping", ref)
+	}
+	if strings.Contains(string(data), "schemas/_") {
+		t.Errorf("ref to a hidden definition leaked into output")
+	}
+}
+
+func TestCollectEnumStrings(t *testing.T) {
+	cases := []struct {
+		expr string
+		want []string // nil: expect ok=false
+	}{
+		{`"a" | "b" | "c"`, []string{"a", "b", "c"}},
+		{`*"a" | "b"`, []string{"a", "b"}},
+		{`"a" | *"b" | "c"`, []string{"a", "b", "c"}},
+		{`"a" | #Other`, nil},
+		{`int | string`, nil},
+		{`"a" & "b"`, nil},
+	}
+	for _, tc := range cases {
+		expr, err := parser.ParseExpr("test", tc.expr)
+		if err != nil {
+			t.Fatalf("%s: %v", tc.expr, err)
+		}
+		got, ok := collectEnumStrings(expr)
+		if tc.want == nil {
+			if ok {
+				t.Errorf("%s: expected ok=false, got %v", tc.expr, got)
+			}
+		} else if !ok || !slices.Equal(got, tc.want) {
+			t.Errorf("%s: got %v (ok=%v), want %v", tc.expr, got, ok, tc.want)
+		}
+	}
+}