diff --git a/config_test.go b/config_test.go
index c6b5005..7171943 100644
--- a/config_test.go
+++ b/config_test.go
@@ -255,3 +255,32 @@ func TestRequiredConfigSelectorOnlyAppliesToSelectedScopes(t *testing.T) {
 		}
 	}
 }
+
+func TestUnknownConfigScopeReportsChoicesWithoutRuntimeWork(t *testing.T) {
+	for _, tc := range []struct {
+		names   []string
+		scope   []string
+		choices string
+	}{
+		{[]string{"promptkit"}, nil, "available: promptkit"},
+		{[]string{"zeta", "alpha", "promptkit", "app"}, []string{"--scope", "unknown"}, "available: app, promptkit, alpha, zeta"},
+	} {
+		runtimeCalls := 0
+		suite := ConfigSuite[struct{}]{NewContext: func() struct{} { runtimeCalls++; return struct{}{} }}
+		for _, name := range tc.names {
+			suite.Scopes = append(suite.Scopes, ConfigScope[struct{}]{Name: name, Operations: []ConfigOperation{ConfigValidate}, Acquire: func(context.Context, ConfigRequest, struct{}) (Acquired[ConfigView], error) {
+				runtimeCalls++
+				return Acquired[ConfigView]{}, nil
+			}})
+		}
+		app, _ := New(Identity{Name: "example"})
+		if err := RegisterConfig(app, suite); err != nil {
+			t.Fatal(err)
+		}
+		var out, diagnostics bytes.Buffer
+		result := app.Execute(context.Background(), append([]string{"config", "validate"}, tc.scope...), Streams{Out: &out, Err: &diagnostics})
+		if result.Kind != OutcomeUsage || runtimeCalls != 0 || out.Len() != 0 || !strings.Contains(diagnostics.String(), tc.choices) {
+			t.Fatalf("result=%#v calls=%d out=%q diagnostics=%q", result, runtimeCalls, out.String(), diagnostics.String())
+		}
+	}
+}
diff --git a/docs/roadmap/remediation.md b/docs/roadmap/remediation.md
index 6033fc5..a25a2a3 100644
--- a/docs/roadmap/remediation.md
+++ b/docs/roadmap/remediation.md
@@ -66,6 +66,9 @@ architecture. The issues below affect behavior within the implemented structure.
 - R-07 complete: nil diagnostic writers are no-output entries, do not count as
   delivery attempts, and cannot suppress cause presentation.
 
+- R-08 complete: unknown scopes and absent default app scopes report available
+  choices in standard scope order without runtime acquisition.
+
 ## Findings and priority
 
 P1 means a supported invocation is blocked or its report content is corrupted.
diff --git a/selectors.go b/selectors.go
index b564986..385daad 100644
--- a/selectors.go
+++ b/selectors.go
@@ -118,7 +118,11 @@ func selectConfigScopes[C any](suite ConfigSuite[C], input configInput[C], opera
 	} else {
 		scope, ok := findConfigScope(suite.Scopes, input.Scope)
 		if !ok {
-			return nil, fmt.Errorf("unknown configuration scope %q", input.Scope)
+			choices := make([]string, 0, len(suite.Scopes))
+			for _, available := range orderedConfigScopes(suite.Scopes) {
+				choices = append(choices, available.Name)
+			}
+			return nil, fmt.Errorf("unknown configuration scope %q (available: %s)", input.Scope, joinStrings(choices))
 		}
 		if !containsOperation(scope.Operations, operation) {
 			return nil, unsupportedConfigOperation(scope, operation)