diff --git a/internal/cmd/template_use.go b/internal/cmd/template_use.go
index b08a7a5..5b22696 100644
--- a/internal/cmd/template_use.go
+++ b/internal/cmd/template_use.go
@@ -161,7 +161,6 @@ func (a *App) executeTemplate(templateRoot, targetDir string, opts executeOpts)
 	defer os.RemoveAll(tmp)
 
 	tmpl.Context = ctx
-	tmpl.ComputedDefs = nil // already applied above
 	if err := tmpl.Execute(tmp); err != nil {
 		return err
 	}
diff --git a/internal/cmd/template_validate.go b/internal/cmd/template_validate.go
index 9b9ee20..cea7e71 100644
--- a/internal/cmd/template_validate.go
+++ b/internal/cmd/template_validate.go
@@ -41,6 +41,14 @@ func newTemplateValidateCmd(app *App) *cobra.Command {
 			// Use the first option so the template engine can compare them as strings.
 			resolveSelectDefaults(tmpl.Context)
 
+			if len(tmpl.ComputedDefs) > 0 {
+				computed, err := pkgtemplate.ApplyComputed(tmpl.Context, tmpl.ComputedDefs, tmpl.FuncMap(), tmpl.Delims())
+				if err != nil {
+					return fmt.Errorf("resolving computed values: %w", err)
+				}
+				tmpl.Context = computed
+			}
+
 			tmp, err := os.MkdirTemp("", "specs-validate-*")
 			if err != nil {
 				return err
diff --git a/internal/template/context.go b/internal/template/context.go
index 8db5e9d..074410d 100644
--- a/internal/template/context.go
+++ b/internal/template/context.go
@@ -180,6 +180,7 @@ func extractComputed(raw map[string]any) (map[string]string, error) {
 
 // resolveReferencedDefaults renders string values containing the left delimiter in
 // topological order so that each key's pre-fill value is correct before the user is prompted.
+// It returns a new map; the caller's input is never modified.
 func resolveReferencedDefaults(ctx map[string]any, funcMap texttemplate.FuncMap, delims specs.Delimiters) (map[string]any, error) {
 	// Find keys whose string value is a template expression.
 	var refKeys []string
@@ -202,15 +203,19 @@ func resolveReferencedDefaults(ctx map[string]any, funcMap texttemplate.FuncMap,
 		return nil, fmt.Errorf("referenced defaults: %w", err)
 	}
 
+	// Copy the input map so the caller's map is not mutated.
+	result := make(map[string]any, len(ctx))
+	maps.Copy(result, ctx)
+
 	for _, k := range sorted {
-		val, err := renderExpr(ctx[k].(string), ctx, funcMap, delims)
+		val, err := renderExpr(result[k].(string), result, funcMap, delims)
 		if err != nil {
 			return nil, fmt.Errorf("referenced default %q: %w", k, err)
 		}
-		ctx[k] = val
+		result[k] = val
 	}
 
-	return ctx, nil
+	return result, nil
 }
 
 // topoSort returns keys in an order where each key comes after all of its
diff --git a/internal/template/context_internal_test.go b/internal/template/context_internal_test.go
new file mode 100644
index 0000000..038431e
--- /dev/null
+++ b/internal/template/context_internal_test.go
@@ -0,0 +1,45 @@
+package template
+
+import (
+	"testing"
+
+	"github.com/specsnl/specs-cli/internal/specs"
+)
+
+func TestResolveReferencedDefaults_DoesNotMutateInput(t *testing.T) {
+	input := map[string]any{
+		"Name": "My App",
+		"Slug": "{{ .Name | toKebabCase }}",
+	}
+	// Take a snapshot of the template expression before calling.
+	originalSlug := input["Slug"]
+
+	fm := FuncMap(Config{})
+	result, err := resolveReferencedDefaults(input, fm, specs.DefaultDelimiters)
+	if err != nil {
+		t.Fatalf("resolveReferencedDefaults: %v", err)
+	}
+
+	// The input map must not have been modified.
+	if input["Slug"] != originalSlug {
+		t.Errorf("input[Slug] was mutated: got %q, want %q", input["Slug"], originalSlug)
+	}
+
+	// The returned map must have the resolved value.
+	if result["Slug"] != "my-app" {
+		t.Errorf("result[Slug] = %q, want %q", result["Slug"], "my-app")
+	}
+}
+
+func TestResolveReferencedDefaults_NoRefs_ReturnsSameMap(t *testing.T) {
+	input := map[string]any{"Name": "plain"}
+	fm := FuncMap(Config{})
+	result, err := resolveReferencedDefaults(input, fm, specs.DefaultDelimiters)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	// When there are no template refs, the original map may be returned as-is.
+	if result["Name"] != "plain" {
+		t.Errorf("result[Name] = %q, want %q", result["Name"], "plain")
+	}
+}
diff --git a/internal/template/template.go b/internal/template/template.go
index 81d799e..beba330 100644
--- a/internal/template/template.go
+++ b/internal/template/template.go
@@ -63,7 +63,7 @@ type RenderWarning struct {
 type Template struct {
 	Root         string                 // path to the template root (contains project.yaml + template/)
 	Context      map[string]any         // user input map with referenced defaults resolved
-	ComputedDefs map[string]string      // raw computed definitions; resolved by ApplyComputed post-prompt
+	ComputedDefs map[string]string      // raw computed definitions; caller must apply via ApplyComputed before Execute
 	Conditionals Conditionals           // varName → Cond; absent means always prompt
 	Referenced   map[string]bool        // schema variables referenced in template files or computed expressions
 	Metadata     *Metadata              // nil if __metadata.json is absent
@@ -146,17 +146,10 @@ func Get(templateRoot string, cfg Config) (*Template, error) {
 }
 
 // Execute renders the template/ subdirectory into targetDir, which must already exist.
-// If ComputedDefs is non-empty, computed values are resolved and merged into the context
-// before the walk begins.
+// Context must already contain all resolved values (user inputs and computed); call
+// ApplyComputed before Execute when ComputedDefs are present.
 func (t *Template) Execute(targetDir string) error {
 	ctx := t.Context
-	if len(t.ComputedDefs) > 0 {
-		var err error
-		ctx, err = ApplyComputed(t.Context, t.ComputedDefs, t.funcMap, t.cfg.delims())
-		if err != nil {
-			return err
-		}
-	}
 
 	srcRoot := filepath.Join(t.Root, specs.TemplateDirFile)
 
diff --git a/internal/template/template_test.go b/internal/template/template_test.go
index ad56599..0692e08 100644
--- a/internal/template/template_test.go
+++ b/internal/template/template_test.go
@@ -239,6 +239,13 @@ func TestExecute_ComputedValueInTemplate(t *testing.T) {
 		t.Fatalf("Get: %v", err)
 	}
 
+	// Caller is responsible for applying computed values before Execute.
+	ctx, err := pkgtemplate.ApplyComputed(tmpl.Context, tmpl.ComputedDefs, tmpl.FuncMap(), tmpl.Delims())
+	if err != nil {
+		t.Fatalf("ApplyComputed: %v", err)
+	}
+	tmpl.Context = ctx
+
 	target := t.TempDir()
 	if err := tmpl.Execute(target); err != nil {
 		t.Fatalf("Execute: %v", err)
@@ -250,6 +257,27 @@ func TestExecute_ComputedValueInTemplate(t *testing.T) {
 	}
 }
 
+func TestExecute_ComputedNotAppliedByExecute(t *testing.T) {
+	// Execute does not call ApplyComputed internally; a missing computed key causes an error.
+	root := buildTemplate(t,
+		"Name: acme\ncomputed:\n  DbName: \"{{toSnakeCase .Name}}_production\"\n",
+		map[string][]byte{
+			"config.txt": []byte("DB={{.DbName}}"),
+		},
+	)
+
+	tmpl, err := pkgtemplate.Get(root, pkgtemplate.Config{})
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+
+	// Intentionally skip ApplyComputed — Execute must NOT apply it internally.
+	target := t.TempDir()
+	if err := tmpl.Execute(target); err == nil {
+		t.Fatal("Execute: expected error for missing computed key DbName, got nil")
+	}
+}
+
 func TestExecute_PassthroughDoubleBrace(t *testing.T) {
 	// When __delimiters switches to [[ ]], the default {{ }} syntax passes through
 	// unchanged — important for files like GitHub Actions YAML that already use {{ }}.